A list of battery charging figures

[swift1894]

My 4 X 180Ah domestic batteries were reading very low this morning (11.7v) due to heavy use last night, which isn't normal practice.

 

I fired up the genny to recharge via the 80A charger and theses are the readings after 3.25 hours taken every 15 minutes.

13.6v 84A

13.4. 81

13.47 78

13.59 74

13.75 74

13.91 74

14.02 77(?)

14.08 63

14.22 50

14.24 48

14.26 45

14.30 38

14.32 33

14.35 29

 

I switched genny off then and all the electrics to see the state of charge in an hour.

 

What, if anything, do these figures show to the " electrically minded".

The batteries are about 4 years old (lead acid)

[Paul C]

4x180 = 720. I'd be looking for a tail current of (say) 1%, so 7.2A

 

Your figures show the most recent reading is 29A, approx 4% of my desired tail current. Can you clarify what your amp readings are - are they INTO the battery, or OUT OF the battery charger - because the two will be different:

 

Current INTO battery = current OUT OF charger - LOADS

 

LOADS, being the electrical load at the time of the reading eg fridge, lights, etc

 

 

Its close to fully charged but its not.

[nicknorman]

It tells us you've put in about 200AH but the batteries are still well short of being fully charged. Starting from a pretty low SoC (was the 11.7v at no load, or under some load?) you have put in roughly 1/4 of the rated capacity and got them up to moderately, but not completely, full. Hard to be precise but it suggests the batteries are well down on capacity, maybe at 1/2 their rated capacity. Whether any more capacity is recoverable with a long charge is debatable, but anyway I would charge the batteries fully asap, that means charging until the current is down to perhaps 10A or less (or anyway, until the current hasn't reduced within the last 30 mins or so).

 

At what current do you normally stop charging?

 

A longer charge would be a good idea. What sort of batteries are they? If wet batteries, and if your charger supports it, an equalisation charge might be a good idea.

[by'eck]

My calculation of amp hours put in is close although a little less than Nick's. I would agree that the readings suggest the capacity of the batteries is much less than the original 720 Ah. Difficult to interpolate from the readings but I would guess given the tail off of current draw no more than half original. Of course a good equalise charge may restore some of what has been lost.

[swift1894]

Just to update things these are the readings on my Mastervolt MICC (which I read from during charging as well) for 2 hours after charging and with all electrics turned off.

12.83v immediately after switching genny/ charger off

12.78v after 1 hour

12.70v after 2 hours

[swift1894]

It tells us you've put in about 200AH but the batteries are still well short of being fully charged. Starting from a pretty low SoC (was the 11.7v at no load, or under some load?) you have put in roughly 1/4 of the rated capacity and got them up to moderately, but not completely, full. Hard to be precise but it suggests the batteries are well down on capacity, maybe at 1/2 their rated capacity. Whether any more capacity is recoverable with a long charge is debatable, but anyway I would charge the batteries fully asap, that means charging until the current is down to perhaps 10A or less (or anyway, until the current hasn't reduced within the last 30 mins or so).

At what current do you normally stop charging?

A longer charge would be a good idea. What sort of batteries are they? If wet batteries, and if your charger supports it, an equalisation charge might be a good idea.

11.7 v was at no load. I don't have a particular charging cut off point as I often get a good charge from my solar panels ( but not today!).

They are wet Lead acids. I'm not sure if my Mastervolt 12/80 charger does an equalization charge, I'll check the manual but it doesn't ring any bells.

11.7 v was at no load. I don't have a particular charging cut off point as I often get a good charge from my solar panels ( but not today!).

They are wet Lead acids. I'm not sure if my Mastervolt 12/80 charger does an equalization charge, I'll check the manual but it doesn't ring any bells.

Btw now down to 12.54v 2.8A with nothing much on, but fridge and separate mini freezer obviously kicked in immediately after 2 hours of no power.

[Paul C]

You're only ever going to get a rough estimate on voltage alone. The key parameter(s) to watch are tail current during charging, near full batteries. To accurately estimate state of charge based on voltage alone, you'd need to be monitoring at much higher frequency than a person can do (realistically), for example a reading every few seconds, to see the voltage changes over these short timescales. This is basically how Smartgauge works - and its algorithms are proprietory.

[nicknorman]

11.7 v was at no load. I don't have a particular charging cut off point as I often get a good charge from my solar panels ( but not today!).

They are wet Lead acids. I'm not sure if my Mastervolt 12/80 charger does an equalization charge, I'll check the manual but it doesn't ring any bells.

 

Btw now down to 12.54v 2.8A with nothing much on, but fridge and separate mini freezer obviously kicked in immediately after 2 hours of no power.

The manual I could find on line is for a Mastervolt Mass 12/80-2 which I guess could be a "mark 2" version, although the front panel doesn't have the "-2" on the logo.

 

Anyway, you can only set equalise mode via Masterbus, so you would need a Masterbus interface + laptop (+free software) or something like a Masterview Easy (which is too expensive if that's all you need it for). Pretty sure the MCC doesn't allow setting equalise mode.

 

I also notice that the standard bulk charge voltage is 14.25 (temperature compensated) which is quite low especially for modern leisure batteries with lots of calcium. I would therefore recommend increasing the charge voltage by setting the DIP switches to the "traction" setting (dip switch 2) which will give 14.6v, which is a much better charging voltage to get the batteries fully charged. I also note there is a "diode" dip switch setting which has the effect of raising the voltage another 0.6v. If this is currently not activated, you could set it so that you would get another 0.6v which will give you 15.2v, which is getting close to an equalise voltage (nominally 15.5v).

 

I think you have been chronically undercharging your batteries by having a low charge voltage and short charging times. You might have knackered them, or you might be able to get some capacity back by equalising. However the latter requires quite a long charging time so if possible I would try to get onto shore power so you can first fully charge the batteries until the current is down to perhaps 7A or less at 14.6v, and then give it a further several hours at 15.2v.

 

Usual things apply for equalising, make sure the batteries have sufficient water and watch out for explosive hydrogen gas, and monitor for any significant temperature rise. The current during equalise should be no more than about 15A

Edited November 20, 2015 by nicknorman

[swift1894]

The manual I could find on line is for a Mastervolt Mass 12/80-2 which I guess could be a "mark 2" version, although the front panel doesn't have the "-2" on the logo.

Anyway, you can only set equalise mode via Masterbus, so you would need a Masterbus interface + laptop (+free software) or something like a Masterview Easy (which is too expensive if that's all you need it for). Pretty sure the MCC doesn't allow setting equalise mode.

I also notice that the standard bulk charge voltage is 14.25 (temperature compensated) which is quite low especially for modern leisure batteries with lots of calcium. I would therefore recommend increasing the charge voltage by setting the DIP switches to the "traction" setting (dip switch 2) which will give 14.6v, which is a much better charging voltage to get the batteries fully charged. I also note there is a "diode" dip switch setting which has the effect of raising the voltage another 0.6v. If this is currently not activated, you could set it so that you would get another 0.6v which will give you 15.2v, which is getting close to an equalise voltage (nominally 15.5v).

I think you have been chronically undercharging your batteries by having a low charge voltage and short charging times. You might have knackered them, or you might be able to get some capacity back by equalising. However the latter requires quite a long charging time so if possible I would try to get onto shore power so you can first fully charge the batteries until the current is down to perhaps 7A or less at 14.6v, and then give it a further several hours at 15.2v.

Usual things apply for equalising, make sure the batteries have sufficient water and watch out for explosive hydrogen gas, and monitor for any significant temperature rise. The current during equalise should be no more than about 15A

Brilliant. I shall adjust the dip switches accordingly. Currently all 4 are in the "off" setting so I'll change number 2 switch to "on" ( traction) and see how things go. Then once every so often change to traction + diode by switching switch 4 to "on" as well.

[nicknorman]

Brilliant. I shall adjust the dip switches accordingly. Currently all 4 are in the "off" setting so I'll change number 2 switch to "on" ( traction) and see how things go. Then once every so often change to traction + diode by switching switch 4 to "on" as well.

That's it. But I think you will need a long period of charging with 2 and 4 on to recover some capacity.

[swift1894]

That's it. But I think you will need a long period of charging with 2 and 4 on to recover some capacity.

Do you think I should put 2 & 4 "on" straight away. I've put 1 on and immediately got 14.67v which I've never had before. Yippee!!

 

Btw I remember talking to a guy at Mastervolt in The Nederlands some years ago and when I told him I had 720Ah of 12 volt batteries I think he recommended that I'd be better with 2 X 80A chargers. Is there any sense in that?

Edited November 21, 2015 by swift1894

[Graham.m]

My 4 X 180Ah domestic batteries were reading very low this morning (11.7v) due to heavy use last night, which isn't normal practice.

 

I fired up the genny to recharge via the 80A charger and theses are the readings after 3.25 hours taken every 15 minutes.

13.6v 84A

13.4. 81

13.47 78

13.59 74

13.75 74

13.91 74

14.02 77(?)

14.08 63

14.22 50

14.24 48

14.26 45

14.30 38

14.32 33

14.35 29

 

I switched genny off then and all the electrics to see the state of charge in an hour.

 

What, if anything, do these figures show to the " electrically minded".

The batteries are about 4 years old (lead acid)

 

I would say as these are wet lead acids get the hydrometer out and check the SG for more accurate way of checking level of charge

 

Looking at those figures I would guess a long way to go to full charge, but only a guess.

 

What is the temperature of the batteries and the SG?

[Graham.m]

When was the last time you topped the battery water up?

[bottle]

Do you think I should put 2 & 4 "on" straight away. I've put 1 on and immediately got 14.67v which I've never had before. Yippee!!

 

Btw I remember talking to a guy at Mastervolt in The Nederlands some years ago and when I told him I had 720Ah of 12 volt batteries I think he recommended that I'd be better with 2 X 80A chargers. Is there any sense in that?

 

Have I given you this link before (from the man that designed the Smartgauge)

 

http://www.smartgauge.co.uk/chargesize.html

[nicknorman]

Do you think I should put 2 & 4 "on" straight away. I've put 1 on and immediately got 14.67v which I've never had before. Yippee!!

Btw I remember talking to a guy at Mastervolt in The Nederlands some years ago and when I told him I had 720Ah of 12 volt batteries I think he recommended that I'd be better with 2 X 80A chargers. Is there any sense in that?

Equalisation is best done once the batteries are fully charged. Not really sure why, but I suppose you will get a lot of gassing for longer, possibly more plate corrosion in the long term. I would leave it on "traction" until the current drops to around 1% (ie around 7A, although we could be generous and say 10A!). That is the current going into the batteries, not the current coming out it of the charger which will include anything the boat's services are using. When you say "I've put 1 on" I presume you mean "one of them", not DIP switch 1?

 

80A is a little small for 720AH but if you get a bigger charger or another one, you need the generator to be able to supply that much power and you won't save a massive amount of charging time. Anyway, you batteries are probably more like 300AH at the moment!

[swift1894]

When you say "I've put 1 on" I presume you mean "one of them", not DIP switch 1?

Yes that's right, I meant I'd put one of them i.e. number 2 dip switch

'Twas a bit ambiguous.?

 

I'll put the dip switches onto traction & diode next week.

 

Thanks for the advice.?

Have I given you this link before (from the man that designed the Smartgauge)

 

http://www.smartgauge.co.uk/chargesize.html

Possibly. Might have been a while since. I'll have another read.

Thanks

Edited November 21, 2015 by swift1894

[dmr]

 

I would say as these are wet lead acids get the hydrometer out and check the SG for more accurate way of checking level of charge

 

Looking at those figures I would guess a long way to go to full charge, but only a guess.

 

What is the temperature of the batteries and the SG?

 

Based on Nicks 10 amps, about another 2 hours to fully charged!

 

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

[nicknorman]

Based on Nicks 10 amps, about another 2 hours to fully charged!

 

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

I meant 10A as a compromise point to turn up the voltage to equalisation. I think to get "fully charged" you'd need to get a good bit lower than that. I'd say 4 hrs!

[Graham.m]

Equalisation is best done once the batteries are fully charged. Not really sure why, but I suppose you will get a lot of gassing for longer, possibly more plate corrosion in the long term. I would leave it on "traction" until the current drops to around 1% (ie around 7A, although we could be generous and say 10A!). That is the current going into the batteries, not the current coming out it of the charger which will include anything the boat's services are using. When you say "I've put 1 on" I presume you mean "one of them", not DIP switch 1?

 

80A is a little small for 720AH but if you get a bigger charger or another one, you need the generator to be able to supply that much power and you won't save a massive amount of charging time. Anyway, you batteries are probably more like 300AH at the moment!

 

Need to know what the SG readings of each cell. Looking at the voltage and current decay. Even at 80A I would have expected the current to stay up for quite a while, but it had dropped over 30A in 3 Hours.

 

Wondering what the electrolyte level is and how long it is since the batteries were fully charged.

[nicknorman]

Need to know what the SG readings of each cell. Looking at the voltage and current decay. Even at 80A I would have expected the current to stay up for quite a while, but it had dropped over 30A in 3 Hours.

 

Wondering what the electrolyte level is and how long it is since the batteries were fully charged.

Yes I think the actual capacity is well down. Electrolyte levels have had a few mentions including from myself. I suspect it is a long time since the batteries were properly fully charged.

[Loafer]

 

Btw I remember talking to a guy at Mastervolt in The Nederlands some years ago and when I told him I had 720Ah of 12 volt batteries I think he recommended that I'd be better with 2 X 80A chargers. Is there any sense in that?

 

There's sense in that if you have spare shekels to buy a second charger. BUT before you do:

 

You don't have 720Ah any more. Sounds like you have about 400Ah max, so at the moment, ONE 80A charger is fine. As you can see, your charger isn't having to provide all 80A for long.

 

If and when you replace your battery bank, then do some more trials before you buy a second 80A charger.

 

If you see the charge current reducing below 80 A within an hour, then MY view is that a single 80A charger is plenty.

[Graham.m]

Yes I think the actual capacity is well down. Electrolyte levels have had a few mentions including from myself. I suspect it is a long time since the batteries were properly fully charged.

 

I have a feeling that one or more of the cells has gone hig, The low voltage for the first two hours or so concerns me, suggests there is something wrong with the battery impedance.

 

There's sense in that if you have spare shekels to buy a second charger. BUT before you do:

 

You don't have 720Ah any more. Sounds like you have about 400Ah max, so at the moment, ONE 80A charger is fine. As you can see, your charger isn't having to provide all 80A for long.

 

If and when you replace your battery bank, then do some more trials before you buy a second 80A charger.

 

If you see the charge current reducing below 80 A within an hour, then MY view is that a single 80A charger is plenty.

 

I would suggest it depends on how much DC power is being used in 24 hours as a norm.

 

My guess is the present capacity could be between 150 and 200Ah, but only a guess. SG readings with a Hydrometer would give a better idea

[swift1894]

Need to know what the SG readings of each cell. Looking at the voltage and current decay. Even at 80A I would have expected the current to stay up for quite a while, but it had dropped over 30A in 3 Hours.

 

Wondering what the electrolyte level is and how long it is since the batteries were fully charged.

 

Battery levels are fine.

It's several months since I was on mains supply though so, obviously, it's that long ago since they were fully charged.

Next stop......the hydrometer shop!

Edited November 22, 2015 by swift1894

[Graham.m]

Battery levels are fine.

It's several months since I was on mains supply though so, obviously, it's that long ago since they were fully charged.

Next stop......the hydrometer shop!

 

When a lead acid battery is discharged lead sulphate is produce by the chemical reaction. Initially this is soft and the action of fully recharging the battery turns it back into lead and sulphuric acid. Unfortunately if the battery is not recharged or fully recharged the lead sulphate turns into hard crystals which are hard or impossible to remove. The effect of this is that the battery’s capacity is reduced it is frequently referred to as sulphation and is one of the major cause of battery failure.

 

Thus it is important to FULLY recharge batteries after discharge.

[nicknorman]

Battery levels are fine.

It's several months since I was on mains supply though so, obviously, it's that long ago since they were fully charged.

Next stop......the hydrometer shop!

If you plan to get a hydrometer, I'd recommend the optical refractometer type that you can get from eBay for 20-30 quid. Easier to read IMO and no issues with float sticking etc,

 

Like this:

 

http://www.ebay.co.uk/itm/Battery-Acid-Ethylene-Propylene-Glycol-Antifreeze-ATC-AdBlue-Urea-Refractometer-/181934518426?hash=item2a5c24709a:g:X6EAAOxyOlhS3LyR

 

£17 in fact

Edited November 22, 2015 by nicknorman