Batteries nightmare

[Fred_Smith]

Interesting topic this, surely a boat electrician would have confirmed the cabling was correct or not and the right sized cables used when he looked at it (Re Gibos point), did he?

Probably of no help but to endorse the Victron equipment, I have the same combi (but 2500 inverter) and the same monitor, both have operated faultlessly, the batteries don't boil, I do have a look at them every couple of months to check the levels and have topped up the water once in 12 months even then they hardly needed water.

Regarding the table in the first post what was the amp draw (which is net of whats going in and whats being taken out on the monitor readout) at the various times? might give a clue about the possible overcharging

Just a general point but you have a very big bank, I know you can have a big one of you choose but I would have thought 500 amp more than enough especially as you have land line most of the time, just curious

[nicknorman]

I've been trying to come to terms with the SOC reading of my Victron BMV302 and have noticed that the default setting for the Tail Current (the current at which the monitor considers the battery to be fully charged) is 4% of battery capacity which in the case of the OP would be 32.4amps. In other words when the current drops to 32.4amps and the voltage meets a minimum requirement (default 13.2volts) for a given period (default 3 minutes) then the monitor considers the battery to be 100% charged and will reset the SOC to 100% and the Consumed Energy to zero. This is patently wrong, as another contributor has pointed out this should be about 2-3 amps. As Tony has also pointed out this will have a cumulative effect very quickly showing a nearly totally discharged battery as fully charged. Changing the Tail Current setting to the minimum of 0.5% and the Battery Capacity to a more realistic figure, decreasing it occassionally as the batteries age, I'm hoping will give a more realistic estimate of actual SOC.

Don't forget that it is the current per battery AH that is important - the current for the whole bank will depend on the size of the bank!. That said, I agree that 32.4A (4%) is quite a high figure, but suggest that it should come down to 2-3 amps for a smaller bank of say 330 AH, but more than twice that for the OPs large bank. I would have thought 1% was the minimum to ensure that 100% was ever reached, so 8A in the case of the OP

[Rebotco]

Thanks - hugely - for the time you have spent on this. I am slightly embarrassed, though grateful, for the amount of debate this has generated but, on a positive note, this does rather support my contention that, as the problem seems relatively hard to explain, it is unreasonable for the boat builders to deny it is their responsibility as a warranty issue. Priority now is to stop it happening again; I will post photos early next week (am having a 'battery-free' weekend in Brighton!), to show interconnecting leads. And I have now bought a hydrometer and a UNI-T ut203 multimeter..........

 

The battery supplier will be looking at the batteries next week; they suggest the charger might have been 'turned down' (by Victron) too much, to compensate for the earlier overcharging

 

I agree I will probably need an 'expert report' (and recognise the danger of trying to fix the problem myself.) Any suggestions?

 

Bob

 

Hi Bob

Please do not feel embarrassed. The discussion is of immense value to many other boaters who have similar or related questions, but have not asked them.

It is the minute detail this sort of query unearths that is of such value, and cannot be found in one place elsewhere.

I for one am grateful to you for raising the issue.

[nicknorman]

Ref. periods on the shoreline (where we have spent the vast bulk of our time), some points of clarification on our battery care. It's sadly true that I believed uncritically the readouts from the Victron Monitor; I had, it seems wrongly, thought the whole charging and recharging routine was controlled automatically (and efficiently.....?) by the Victron charging and monitoring equipment. I will certainly not rely on SOC again, but it has never actually led me to take the batteries off charge just because it suggested they were 100% 'fully' charged; I have done so only to test their health every few months. The adaptive charging problem you explain, though, would certainly have added to any potential difficulties.

 

The only occasions we have ever left the batteries standing discharged have been overnight when (infrequently) cruising. As for 'using the boat like a house', yes, maybe on occasions, but only when on the shoreline. When using the batteries, we have been scrupulously (and increasingly!) careful with them, to a degree that others with a similar size bank have said is unnecessary. Yet (as a reminder), two new 810 amp battery banks seem to have been destroyed, one boiled and one not, in less than two years, with a total 180 hours engine use (first bank:150 hours; second bank: 30 hours), from new. The present bank has left the shoreline just once since their installation in late July 2011.

 

Re the synchronisation issue, I had understood (wrongly?) from the manual that the meter was resynched every time the battery was fully charged (in our case, regularly, on the shoreline), so I thought it should have happened regularly and automatically.

 

After the batteries were (I think!) fully charged at 13.4 volts yesterday evening and then waiting for 3-4 hours with no charge or load, I took the following hydrometer readings:

 

Battery Cells

1. 1.255. 1.255. 1.230. 1.220. 1.220. 1.240

2. 1.225. 1.250. 1.250. 1.260. 1.260. 1.250

3. 1.230. 1.230. 1.230. 1.240. 1.250. 1.260

4. 1.225. 1.250. 1.240. 1.225. 1.240. 1.240

5. 1.230. 1.245. 1.250. 1.250. 1.250. 1.250

6. 1.250 1.250. 1.230. 1.250. 1.250. 1.250

 

 

From your comments, these readings would seem to show some bad cells?

 

I am no expert on battery SG but it certainly looks to be too much spread for a healthy bank. But on the other hand, some cells showing fully charged. Have you tried an equalisation charge (read the Victron handbook to see if it will do that - I am sure it will). That puts a higher than normal charging voltage onto the bank for a limited time and might help to recover some capacity, however with the figures you posted originally I doubt it will make a massive difference

 

From your description it does seem hard to understand why the batteries have died, if they have been on a correcly set up charger for nearly all the short life. You are right to say that if the batteries are left on charge for a long time (with charger set correctly) it is not unreasonable to assume 100% SOC and the 600S should show that. However the meter will still show incorrectly if the actual battery capacity is less than that programmed into the meter.

 

So the question as to why the batteries seem severely sulphated remains unanswered to me. Meters like the 600S are worst when the batteries are cycled between say 50% and 80% repeatedly - after just a few cycles it will be way out. But you do not seem to be using it like that.

Edited June 8, 2012 by nicknorman

[Nickhlx]

We have a rated 480 aH of Trojan's and they are always brought up to an indicated 100% SoC daily, by both the Victron SoC meter, and the Smartgauge I added subsequently...

 

We have a 12V Waeco fridge, which I set to coldest by day when cruising and down to "1" for the night. We make around 8 pieces of toast each morning for breakfast on an electric toaster, and also have a microwave which, although used sparingly, does tend to heat milk and soup drinks when done by the cupful ( saves a bit of washing up) and I do tend to do the latter with the engine running, so these effectively are not having an impact on depleting the SoC

 

I have also changed almost all bulbs in the ceiling ( some 20 of them) for G4 LED lights that take around 1.8 watts ( and not had any failures in 3 years) which has saved a massive number of amp hours each evening .... ( I think this has been the most significant improvement I have done to reduce consumption, and do know I am mindful

of drawing significant powers only when the engine is running...)

 

and

 

we generally have the TV on each evening between around 18-00 hrs and 23-00 hrs... which draws around 36 watts. I run it from the mains, Victron Combi 12/3000/120, as I am concerned that spikes from the water pump / fridge etc may harm the TV...

 

In the morning we have the Webasto water heater come on from an hour before we get up to check we have enough hot water for 5 showers and to "take the edge off" the cooler temps in colder periods.

 

Last weekend we had a 4 day cruise and my daughter was lamenting she had "forgotten her hairdryer" !! ( I didn't know she usually brought it with her... )

 

 

The point of all this ?

 

I have yet to see the claimed SoC from either meter get down to below about 85% (of fully charged) and that is from a now 3 year old set of 480 aH batteries

( 4 x 240 aH, 6V, T-125 batteries)...

 

The engine seems to get the bank back up to an indicated 100% within about 4 hours, although it is running for around 8 hours most days... ( Iskra 175 amp alternator)

 

Between cruises, it is hooked up to a shoreline and is just about always at an indicated 99% or 100% when we next arrive at the boat for approx weekly checks when not cruising, and I have only had to top the water in the batteries twice in 3 years...

 

As a result I am very happy with the spec for our needs, and we don't worry about "holding back" on energy demands...

 

Nick

Edited June 8, 2012 by Nickhlx

[Chris Pink]

 

1 Forget 230V altogether when not on shore power (an exception might be made for a washing machine, using a cold cycle).

2 Do a power audit to work out your daily kWh need.

3 Buy batteries with four times that capacity.

4 Fit a Smartguage. Don't stop charging until you are back to 100%.

5 Install solar panels

6 Buy a 2kW petrol genny

7 Install an expensive charger, like a Victron, and match it to the batteries.

8 Never let the batteries go below 50% of capacity, preferably 60%.

9 If you think you can keep to 8, and have the money, consider AGM batteries which are very forgiving.

10 If you use a washing machine, you'll also need an inverter

11 Install a solar hot water system to heat the water in summer. This can be done quite cheaply (under £500 DIY).

 

 

 

1. can't (hard drives need it for instance)

2. varies too much

3. can't afford that

4. no

5. yes with you there

6. I'm happy on 1KW

7. yes, in my dreams, actually I do agree but again Victron is not for the masses so it's wise to keep abreast of the best of the rest. 20A chargers are pretty cheap these days, any more and they start to really ramp in price and even your 120A Victron won't keep that up for long.

8. well my batteries are safe down to 70% DOD according to the manufacturers but in general that' sound but a high target for most of the liveaboards I know to hit.

9. totally disagree flooded batteries are the way to go and I recommend US2200, Trojan 105 and the Crown equivalent (there's also another copy whose name I can't remember but is the cheapest in France)

10. no no no. Use a generator

11. would be nice but is a complicated bit of plumbing and a bit fragile for your average roof. You don't see many around. Heat water with gas is cheap. (*And what is this doing on an electric discussion)

 

Did I miss anything?

 

oh, your 1 and 10 contradict each other

 

I couldn't agree more,but like other practical things,some non practical people just cannot grasp these things no matter how much swotting up they try to do and can't really cope with the simplest of simple one battery systems,why some can't or have never topped up their cars battery never mind checking and topping up 7 or 8 of them beneath a heavy and dangerous great lump of steel plate decking that most w/beam boats seem to have,and then contorting themselves into the shape of the letter ''S''so as to get at em. And all those terminals and battery lugs to be seen to down there in semi darkness.

 

The difference is that if you choose to live off-grid, with that comes the taking of responsibility - which requires some learning. In a house you pass that responsibility to the utility corporations, off-grid you have to take some of that responsibility onto yourself.

 

Education is what is needed. Problem is, discussions such as this reach a frenzy of terminology and technical nit-picking that the average user is soon lost.

 

We have a rated 480 aH of Trojan's and they are always brought up to an indicated 100% SoC daily, by both the Victron SoC meter, and the Smartgauge I added subsequently...

 

 

The engine seems to get the bank back up to an indicated 100% within about 4 hours, although it is running for around 8 hours most days... ( Iskra 175 amp alternator)

 

Between cruises, it is hooked up to a shoreline and is just about always at an indicated 99% or 100% when we next arrive at the boat for approx weekly checks when not cruising, and I have only had to top the water in the batteries twice in 3 years...

 

As a result I am very happy with the spec for our needs, and we don't worry about "holding back" on energy demands...

 

Nick

 

Your usage is one of four common models;

 

Leisure user without hookup

Leisure user with electric hookup

Liveaboard 100% off-grid

Liveaboard grid connected

 

Of the four types your use is definitely the kindest on battery life and therefore you have more power to play with.

 

However for the other models, battery cost (life) has to be balanced against other factors.

 

All discussions of this nature seem to get sidetracked into batteries but the real equation is of power in against power out, the battery (and bank size) is simply something in the middle of the system.

Edited June 8, 2012 by Chris Pink

[George94]

1. can't (hard drives need it for instance)

2. varies too much

3. can't afford that

4. no

5. yes with you there

6. I'm happy on 1KW

7. yes, in my dreams, actually I do agree but again Victron is not for the masses so it's wise to keep abreast of the best of the rest. 20A chargers are pretty cheap these days, any more and they start to really ramp in price and even your 120A Victron won't keep that up for long.

8. well my batteries are safe down to 70% DOD according to the manufacturers but in general that' sound but a high target for most of the liveaboards I know to hit.

9. totally disagree flooded batteries are the way to go and I recommend US2200, Trojan 105 and the Crown equivalent (there's also another copy whose name I can't remember but is the cheapest in France)

10. no no no. Use a generator

11. would be nice but is a complicated bit of plumbing and a bit fragile for your average roof. You don't see many around. Heat water with gas is cheap. (*And what is this doing on an electric discussion)

 

Did I miss anything?

 

oh, your 1 and 10 contradict each other

 

 

 

 

 

It's reassuring that you disagree, Mr Pink.

 

1 But you can probably cut out most other things. Micro-waves, electric kettles, TV, etc.

2 Quite why you can't do a power audit I don't know. Varies? You obviously measure for the highest consumption you might achieve.

3 Can't afford it? Then you won't be able to cope with more than one night without a working genny. 4 times your consumption is 2 days down to 50%.

4 No Smartgauge? Well, perhaps I am not surprised.

5 You agree? Now I am wondering if I might be wrong.

6 1kW is OK if you don't mind taking much longer to charge your batteries.

7 An expensive charger that doesn't cook your batteries is cheaper in the long run.

8 50% is a reasonable rule of thumb, I feel.

9 I agree AGMs are very expensive, but they are preferred by people who value reliability, like the military. They need no maintenance, and can cope with a higher charging voltage, making them less likely to die from neglect or abuse. I shall come back in 10 years and tell you how mine have fared.

10 1kW for a washing machine? You need to be very sure you never use the hot water programme.

11 It's here because it is a way to minimise bought energy

 

And there was no contradiction at all, old chap.

Edited June 8, 2012 by George94

[dmr]

A lot for me to take in, but I'm getting there! Some responses below to the various points made.

 

The comments and suggestions about alternator use/regulation/testing, I understand, and will implement - rigorously!

 

Ref. periods on the shoreline (where we have spent the vast bulk of our time), some points of clarification on our battery care. It's sadly true that I believed uncritically the readouts from the Victron Monitor; I had, it seems wrongly, thought the whole charging and recharging routine was controlled automatically (and efficiently.....?) by the Victron charging and monitoring equipment. I will certainly not rely on SOC again, but it has never actually led me to take the batteries off charge just because it suggested they were 100% 'fully' charged; I have done so only to test their health every few months. The adaptive charging problem you explain, though, would certainly have added to any potential difficulties.

 

The only occasions we have ever left the batteries standing discharged have been overnight when (infrequently) cruising. As for 'using the boat like a house', yes, maybe on occasions, but only when on the shoreline. When using the batteries, we have been scrupulously (and increasingly!) careful with them, to a degree that others with a similar size bank have said is unnecessary. Yet (as a reminder), two new 810 amp battery banks seem to have been destroyed, one boiled and one not, in less than two years, with a total 180 hours engine use (first bank:150 hours; second bank: 30 hours), from new. The present bank has left the shoreline just once since their installation in late July 2011.

 

Re the synchronisation issue, I had understood (wrongly?) from the manual that the meter was resynched every time the battery was fully charged (in our case, regularly, on the shoreline), so I thought it should have happened regularly and automatically.

 

After the batteries were (I think!) fully charged at 13.4 volts yesterday evening and then waiting for 3-4 hours with no charge or load, I took the following hydrometer readings:

 

Battery Cells

1. 1.255. 1.255. 1.230. 1.220. 1.220. 1.240

2. 1.225. 1.250. 1.250. 1.260. 1.260. 1.250

3. 1.230. 1.230. 1.230. 1.240. 1.250. 1.260

4. 1.225. 1.250. 1.240. 1.225. 1.240. 1.240

5. 1.230. 1.245. 1.250. 1.250. 1.250. 1.250

6. 1.250 1.250. 1.230. 1.250. 1.250. 1.250

 

 

From your comments, these readings would seem to show some bad cells?

 

Thanks - hugely - for the time you have spent on this. I am slightly embarrassed, though grateful, for the amount of debate this has generated but, on a positive note, this does rather support my contention that, as the problem seems relatively hard to explain, it is unreasonable for the boat builders to deny it is their responsibility as a warranty issue. Priority now is to stop it happening again; I will post photos early next week (am having a 'battery-free' weekend in Brighton!), to show interconnecting leads. And I have now bought a hydrometer and a UNI-T ut203 multimeter..........

 

The battery supplier will be looking at the batteries next week; they suggest the charger might have been 'turned down' (by Victron) too much, to compensate for the earlier overcharging

 

I agree I will probably need an 'expert report' (and recognise the danger of trying to fix the problem myself.) Any suggestions?

 

Bob

 

I am not an expert on these things, but might just qualify as a half expert.

You have a hydrometer and can take SG measurements of every cell...you are now in a very good position to work out what is going on!

I don't see strong evidence of bad cells here. As has been suggested, swot up on "equalisation" and do a big one, taking SG measurements every hour.

I would hope to see all cells getting to the same value after a few hours, maybe even a little higher than 1.260. You need to get an estimate of battery temperature for accurate results.

It is just possible that these batteries still have a lot of life left in them!!!!!.

..............Dave

[grahame r]

Don't forget that it is the current per battery AH that is important - the current for the whole bank will depend on the size of the bank!. That said, I agree that 32.4A (4%) is quite a high figure, but suggest that it should come down to 2-3 amps for a smaller bank of say 330 AH, but more than twice that for the OPs large bank. I would have thought 1% was the minimum to ensure that 100% was ever reached, so 8A in the case of the OP

 

That's interesting, do you think the final charging current, say when the charger has been on shore power for over 24 hours, is a reliable guide to the actual Battery Capacity as opposed to the rated capacity when the batteries were new? I have 2 x 200amp hour batteries that were new last year and 4 x 110amp hour batteries that are probably knackered so in theory I have 840amp hours but the final current on shore power normally goes down to about 3-4 amps. I'm thinking that if I put in values of say 350 amp hours and 3.5 amps (1%) as tail current then the monitor may actually bear some resemblance to what is really happening.

My original point was that 4% as a default is far too high for any battery bank size and will give misleading results leading to massive undercharging when away from shore power for more than a very few days.

[nicknorman]

That's interesting, do you think the final charging current, say when the charger has been on shore power for over 24 hours, is a reliable guide to the actual Battery Capacity as opposed to the rated capacity when the batteries were new? I have 2 x 200amp hour batteries that were new last year and 4 x 110amp hour batteries that are probably knackered so in theory I have 840amp hours but the final current on shore power normally goes down to about 3-4 amps. I'm thinking that if I put in values of say 350 amp hours and 3.5 amps (1%) as tail current then the monitor may actually bear some resemblance to what is really happening.

 

Good question, but you would have to ask Gibbo that one. Clearly the final current after 24 hrs for good condition batteries will depend on bank size, but whether that diminishes as the batteries lose capacity I am not sure. My inclination would be not, since as batteries degrade there is likely to be more debris in them that could act as partial conductor between plates and therefore result in a higher final current. Just guessing though!

 

You should however put the estimated actual capacity into the meter, rather than the new capacity. You could estimate the actual capacity by discharging for a while from full, noting the AH consumed, then checking the rested open circuit voltage, from which the actual SOC can be fairly well estimated and hence the actual capacity calculated.

Edited June 9, 2012 by nicknorman

[Up The Creek]

Hi Bob

Please do not feel embarrassed. The discussion is of immense value to many other boaters who have similar or related questions, but have not asked them.

It is the minute detail this sort of query unearths that is of such value, and cannot be found in one place elsewhere.

I for one am grateful to you for raising the issue.

 

Thanks Brian. Nice of you to say that.

 

Bob

[smileypete]

It's reassuring that you disagree, Mr Pink.

 

1 But you can probably cut out most other things. Micro-waves, electric kettles, TV, etc.

2 Quite why you can't do a power audit I don't know. Varies? You obviously measure for the highest consumption you might achieve.

3 Can't afford it? Then you won't be able to cope with more than one night without a working genny. 4 times your consumption is 2 days down to 50%.

4 No Smartgauge? Well, perhaps I am not surprised.

5 You agree? Now I am wondering if I might be wrong.

6 1kW is OK if you don't mind taking much longer to charge your batteries.

7 An expensive charger that doesn't cook your batteries is cheaper in the long run.

8 50% is a reasonable rule of thumb, I feel.

9 I agree AGMs are very expensive, but they are preferred by people who value reliability, like the military. They need no maintenance, and can cope with a higher charging voltage, making them less likely to die from neglect or abuse. I shall come back in 10 years and tell you how mine have fared.

10 1kW for a washing machine? You need to be very sure you never use the hot water programme.

11 It's here because it is a way to minimise bought energy

 

And there was no contradiction at all, old chap.

Good points on both sides, few things to add.

 

6V traction batts can discharge by 80% no problem.

Decent size solar install will run a surplus in high summer, OK for spring/autumn.

So use microwave/travel kettle more in high summer, stick to gas winter.

Not much batt cycling in summer = even longer batt life.

Some deep batt cycling in winter = bit less batt life for above batts.

 

cheers,

Pete.

[pistnbroke]

sorry wrong topic

Edited June 9, 2012 by pistnbroke

[Up The Creek]

Good question, but you would have to ask Gibbo that one. Clearly the final current after 24 hrs for good condition batteries will depend on bank size, but whether that diminishes as the batteries lose capacity I am not sure. My inclination would be not, since as batteries degrade there is likely to be more debris in them that could act as partial conductor between plates and therefore result in a higher final current. Just guessing though!

 

You should however put the estimated actual capacity into the meter, rather than the new capacity. You could estimate the actual capacity by discharging for a while from full, noting the AH consumed, then checking the rested open circuit voltage, from which the actual SOC can be fairly well estimated and hence the actual capacity calculated.

 

Makes sense to me, thanks. Don't know if all the same points apply to my Victron Monitor (600S), but am asking Victron for their response, and will let you know what they say.

 

Bob

[Up The Creek]

I am not an expert on these things, but might just qualify as a half expert.

You have a hydrometer and can take SG measurements of every cell...you are now in a very good position to work out what is going on!

I don't see strong evidence of bad cells here. As has been suggested, swot up on "equalisation" and do a big one, taking SG measurements every hour.

I would hope to see all cells getting to the same value after a few hours, maybe even a little higher than 1.260. You need to get an estimate of battery temperature for accurate results.

It is just possible that these batteries still have a lot of life left in them!!!!!.

..............Dave

 

Thanks, the battery suppliers also suggested the 'equalisation' road (though that won't get to the root cause of the problem, of course)) which I will be travelling next week, and will report back.

 

Bob

 

Interesting topic this, surely a boat electrician would have confirmed the cabling was correct or not and the right sized cables used when he looked at it (Re Gibos point), did he?

Probably of no help but to endorse the Victron equipment, I have the same combi (but 2500 inverter) and the same monitor, both have operated faultlessly, the batteries don't boil, I do have a look at them every couple of months to check the levels and have topped up the water once in 12 months even then they hardly needed water.

Regarding the table in the first post what was the amp draw (which is net of whats going in and whats being taken out on the monitor readout) at the various times? might give a clue about the possible overcharging

Just a general point but you have a very big bank, I know you can have a big one of you choose but I would have thought 500 amp more than enough especially as you have land line most of the time, just curious

 

Good points. Will get amp draw figures.

Why such a large battery bank? Same answer about almost all of the more technical aspects of the boat; we took the recommendations of the boat builder..........

 

Bob

[by'eck]

Good question, but you would have to ask Gibbo that one. Clearly the final current after 24 hrs for good condition batteries will depend on bank size, but whether that diminishes as the batteries lose capacity I am not sure. My inclination would be not, since as batteries degrade there is likely to be more debris in them that could act as partial conductor between plates and therefore result in a higher final current. Just guessing though!

 

You should however put the estimated actual capacity into the meter, rather than the new capacity. You could estimate the actual capacity by discharging for a while from full, noting the AH consumed, then checking the rested open circuit voltage, from which the actual SOC can be fairly well estimated and hence the actual capacity calculated.

 

Clearly bank size will effect tail current, but in my experience it depends to a far greater degree on battery type/construction. As I've mentioned before lead/calcium batteries have a very low tail current. I found that at both the beginning & end of their life (due to diminished capacity) five years later, they drew less than an amp floating a 440 Ah bank.

 

A similar sized bank of lead/acid Trojans drew a tail current approx five times higher again at both beginning & end of life, even though lower charger voltage thresholds were set to match battery type.

[smileypete]

Clearly bank size will effect tail current, but in my experience it depends to a far greater degree on battery type/construction. As I've mentioned before lead/calcium batteries have a very low tail current. I found that at both the beginning & end of their life (due to diminished capacity) five years later, they drew less than an amp floating a 440 Ah bank.

 

A similar sized bank of lead/acid Trojans drew a tail current approx five times higher again at both

beginning & end of life, even though lower charger voltage thresholds were set to match battery type.

It's antimony lost from the batt plates that increases the 'finishing current'; as the batts age more antimony is lost from the plates so the current goes up. For a reasonably healthy battery the finishing current level is a good indicator of state of charge, 'The Battery FAQ' gives a good explanation.

 

(Lead/calcium batts have far less antimony so finishing current is much reduced, but the antimony is to strengthen the plates so normal lead calcuim batts aren't as vibration proof.)

 

A good way to learn all about batts is to start with Tony Brooks course notes, then The Battery FAQ, then the US Battery and Trojan websites, then Gibbo's Smartguage website, spend a little time here and there including some hands on with voltmeter/ammeter. NO need to spend hours at a time...

 

I'd suggest the OP could start with Tony's website and uses the voltmeter/ammeter on his batt meter to learn about the the different stages of batt charge and how they discharge.

 

If the batts need a top up charge on a shoreline while the boat unattended for long periods, it would be safer to get the electrician to fit and fuse a smaller charger, then isolate or switch off the Victron. I'm sure the Victron charge output can be down rated, not sure how...

 

cheers, Pete.

~smpt~

Edited June 10, 2012 by smileypete

[dmr]

Thanks, the battery suppliers also suggested the 'equalisation' road (though that won't get to the root cause of the problem, of course)) which I will be travelling next week, and will report back.

 

Bob

 

 

Actually, this just might lead to understanding what the problem is, you then just need to "fix" it.

Your initially problem was due to severe overcharging, or maybe a random cell failure.

That is now fixed.

Your current problem is probably what I would call "degenerative undercharging syndrome".

It goes like this:

For some reason you leave the batteries in a part discharged state for at least a couple of days.

This might be because you use too much electricity overnight when cruising, and don't cruise enough to replace it.

It might be because you leave the boat unattended for a while without a float charge.

The batteries become a little sulphated.

Sulphation is an evil thing because it conspires to fool both you and your charger into thinking you have a 100% charge when you do not.

On charge the current falls, the voltage increases, it looks like full charge, the charger goes into float.

But.........

you only have 85% charge because some of the sulphuric acid is trapped as sulphate.

So now you are leaving the batteries less than fully charged all the time leading to more sulphation.

Next charge looks like 100% but is only 82%, then 80% etc etc.

Your hydrometer is the weapon to use here, it will show that your "fully charged" batteries are only at 1.225 ror 1.230 rather than 1.265 (or more).

You can remove some sulphation with a long charge, this is why liveaboards do an 8 hour run once a week, but if your clever charger goes into float too soon then this will not help.

Slightly worse sulphation can be fixed by equalisation!

Even worse Sulphation can be fixed by a longer equalisation.

For really bad suphation there are special devices available but most people believe they are snake oil!

So

Equalise the hell out of your batteries, you have nothing to lose (as long as you don't blow yourself up).

Improve them as much as you can.

Spent a few months taking hydrometer readings to learn how to keep the batteries fully charged and only then go and get some nice new ones.

You might of course learn that its easier just to get to 90% and replace the batteries a bit more frequently.

Don't feel bad, it took me five years to work this out and I am an electronics engineer!!!

(this might all be rubbish but its worth a go!)

............Dave

[Up The Creek]

Actually, this just might lead to understanding what the problem is, you then just need to "fix" it.

Your initially problem was due to severe overcharging, or maybe a random cell failure.

That is now fixed.

Your current problem is probably what I would call "degenerative undercharging syndrome".

It goes like this:

For some reason you leave the batteries in a part discharged state for at least a couple of days.

This might be because you use too much electricity overnight when cruising, and don't cruise enough to replace it.

It might be because you leave the boat unattended for a while without a float charge.

The batteries become a little sulphated.

Sulphation is an evil thing because it conspires to fool both you and your charger into thinking you have a 100% charge when you do not.

On charge the current falls, the voltage increases, it looks like full charge, the charger goes into float.

But.........

you only have 85% charge because some of the sulphuric acid is trapped as sulphate.

So now you are leaving the batteries less than fully charged all the time leading to more sulphation.

Next charge looks like 100% but is only 82%, then 80% etc etc.

Your hydrometer is the weapon to use here, it will show that your "fully charged" batteries are only at 1.225 ror 1.230 rather than 1.265 (or more).

You can remove some sulphation with a long charge, this is why liveaboards do an 8 hour run once a week, but if your clever charger goes into float too soon then this will not help.

Slightly worse sulphation can be fixed by equalisation!

Even worse Sulphation can be fixed by a longer equalisation.

For really bad suphation there are special devices available but most people believe they are snake oil!

So

Equalise the hell out of your batteries, you have nothing to lose (as long as you don't blow yourself up).

Improve them as much as you can.

Spent a few months taking hydrometer readings to learn how to keep the batteries fully charged and only then go and get some nice new ones.

You might of course learn that its easier just to get to 90% and replace the batteries a bit more frequently.

Don't feel bad, it took me five years to work this out and I am an electronics engineer!!!

(this might all be rubbish but its worth a go!)

............Dave

 

Thanks Dave.

 

Doesn't sound like rubbish to me ("In the land of blind.........."), and trying the suggested equalisation seems to have achieved a consensus. Victron say it's worth a try, too, and it's fairly easy to do with my Victron set up. I'm still at a loss to see how we might have left batteries discharged for a few days, as we are so rarely off the shoreline, but that possibility does seem consistent with the train of events.

 

So, I tried equalisation this evening, and a sample of cells showed, as a result, an increase in SG for some of the apparently weaker cells (e.g from 1.225 to 1.250), and also for some of the stronger ones (from 1.250 to 1.260 etc). Some showed no change at all. That would seem to support your comment that the equalisation does have some limited effect, and is thus worth trying again? Your previous post suggested a few hours, so maybe try it a couple more times? (the Victron automatically stops the equalisation after around an hour). Or is the idea to keep going until I get all, or most, of the cells up to 1.265 or so (if that is possible)?

 

Have also reset the Tail Current to 1%.

 

One other point: after equalising/hammering away at 15.8 volts for an hour or so, the charger returns to float mode, and of course is then at 100% SOC, but (under a load of around 10 amps), it then rumbles away at 14+ volts for at least two hours, before settling at around 13.5. Is that to be expected?

 

Bob

[nicknorman]

Your previous post suggested a few hours, so maybe try it a couple more times? (the Victron automatically stops the equalisation after around an hour).

 

1 hr is quite a short equalisation time. I would note which are the worst cells, then repeat to see if they improve after a further hour. Bear in mind that water will be being electrolysed so ensure battery water levels are OK and remember that explosive hydrogen gas is produced, so have plenty of ventilation and no sparks!

[Tony Brooks]

Thanks Dave.

 

Doesn't sound like rubbish to me ("In the land of blind.........."), and trying the suggested equalisation seems to have achieved a consensus. Victron say it's worth a try, too, and it's fairly easy to do with my Victron set up. I'm still at a loss to see how we might have left batteries discharged for a few days, as we are so rarely off the shoreline, but that possibility does seem consistent with the train of events.

 

So, I tried equalisation this evening, and a sample of cells showed, as a result, an increase in SG for some of the apparently weaker cells (e.g from 1.225 to 1.250), and also for some of the stronger ones (from 1.250 to 1.260 etc). Some showed no change at all. That would seem to support your comment that the equalisation does have some limited effect, and is thus worth trying again? Your previous post suggested a few hours, so maybe try it a couple more times? (the Victron automatically stops the equalisation after around an hour). Or is the idea to keep going until I get all, or most, of the cells up to 1.265 or so (if that is possible)?

 

Have also reset the Tail Current to 1%.

 

One other point: after equalising/hammering away at 15.8 volts for an hour or so, the charger returns to float mode, and of course is then at 100% SOC, but (under a load of around 10 amps), it then rumbles away at 14+ volts for at least two hours, before settling at around 13.5. Is that to be expected?

 

Bob

 

 

I would suggest that no battery charger will ever do a full equalisation charge because the time required will vary between batteries. They should be done manually on a variable voltage charger and under continual monitoring for temperature, electrolyte level and specific gravity.

 

I go with the having another bash at "automatic" equalistaion with the charger.

[Up The Creek]

I would suggest that no battery charger will ever do a full equalisation charge because the time required will vary between batteries. They should be done manually on a variable voltage charger and under continual monitoring for temperature, electrolyte level and specific gravity.

 

I go with the having another bash at "automatic" equalistaion with the charger.

[dmr]

The really proper way to do an equalisation is to measure specific gravity every hour and to keep going till there is no further increase.

I reckon 6 hours would not be unreasonable, but as your batteries are a bit sick 10 or 12 is possible.

BUT BUT BUT

keep an eye on the water levels in the batteries, and the temperature.

I think 30 degC is the absolute max (check on the www)...if the batteries do get hot then stop for a while. The crap weather is on your side here.

and do make sure you have lots of ventilation, the last you thing you need right now is an explosion.

...........Dave

[Nickhlx]

The really proper way to do an equalisation is to measure specific gravity every hour and to keep going till there is no further increase.

I reckon 6 hours would not be unreasonable, but as your batteries are a bit sick 10 or 12 is possible.

BUT BUT BUT

keep an eye on the water levels in the batteries, and the temperature.

I think 30 degC is the absolute max (check on the www)...if the batteries do get hot then stop for a while. The crap weather is on your side here.

and do make sure you have lots of ventilation, the last you thing you need right now is an explosion.

...........Dave

 

I think the temp is 50 deg C as our batts run in an engine room temp of 30+ degrees...

 

( as measured by the Victron thermocouple attached to a battery post)

 

Nick

Edited June 12, 2012 by Nickhlx

[dmr]

I think the temp is 50 deg C as our batts run in an engine room temp of 30+ degrees...

 

Nick

I just found 115F on the www, which is 46C

I measure temperature on the battery case as I dont want to put my nice thermocouple into the acid, so a safety marging is good.

I am sure the thermocouple would be ok but I try to minimise acid contact since the brand new pair of trousers episode.

Our batteries are also in the engine room but the battery box sits right on the baseplate which helps to keep the temperature down.

The downside of this is lower capacity in the winter.

 

This is one of many good descriptions of equalisation on the www:

 

linky

 

Forgot to say...make sure that none of your electrical equipment is going to get upset by the higher equalisation voltage.

 

dave