Batteries (again...)

[smileypete]

Perhaps it time to throw away the battery cataloges and get the generator mags out.

 

A nice, built in, water cooled, cocooned 'on demand' diesel generator starts to look an attractive option if you look at all the problems people have with batteries.

Or put them to one side and head over to http://www.batteryfaq.org/

 

cheers,

Pete.

[mikevye]

A rule I learnt several years ago that applies to the average boater:-

 

However long you think it takes to fully recharge lead acid batteries, treble it and you might be close.

 

It does indeed seem to be about right.

 

Relating this to automotive industry, I regularly have to deal with completely flat batteries, we simply put a booster pack on, crank the engine, vehicle starts and seemingly proceeds with no problem. If we were writing off batteries through letting them go flat it would cost a fortune in replacement costs yet the need to replace them very rarely occurs.

[Sir Nibble]

That's because the capacity used to start the motor is so small compared to the full capacity of the battery and the electrical system is run from the alternator. If you were trying to use the reserve capacity with engine off you would most likely find it gone!

[Gibbo]

Relating this to automotive industry, I regularly have to deal with completely flat batteries, we simply put a booster pack on, crank the engine, vehicle starts and seemingly proceeds with no problem. If we were writing off batteries through letting them go flat it would cost a fortune in replacement costs yet the need to replace them very rarely occurs.

 

Ah but, you have to remember that from the point of view of merely starting the engine the typical vehicle battery is about 50 times bigger than it needs to be.

 

If by "booster pack" you mean one of those little power packs with a 7 to 10Ahr battery in it. then you've accepted how extra large the vehicle battery is in your own post by saying "we simply put a booster pack on, crank the engine, vehicle starts".

 

If you run side by side tests leaving the headlamps on with a new vehicle and one that has had the battery go flat you'll find a dramatic difference.

[mikevye]

Ah but, you have to remember that from the point of view of merely starting the engine the typical vehicle battery is about 50 times bigger than it needs to be.

 

If by "booster pack" you mean one of those little power packs with a 7 to 10Ahr battery in it. then you've accepted how extra large the vehicle battery is in your own post by saying "we simply put a booster pack on, crank the engine, vehicle starts".

 

If you run side by side tests leaving the headlamps on with a new vehicle and one that has had the battery go flat you'll find a dramatic difference.

 

simples!!!!

[ditchcrawler]

Relating this to automotive industry, I regularly have to deal with completely flat batteries, we simply put a booster pack on, crank the engine, vehicle starts and seemingly proceeds with no problem. If we were writing off batteries through letting them go flat it would cost a fortune in replacement costs yet the need to replace them very rarely occurs.

I did this two weeks ago. The Rangerover had been sitting for several weeks and the door lock wouldn't work. The battery was flat as a fart, not even a lamp glimmer. I didn't measure the voltage. I put it on the battery charger for 3 days and night and then put it back on the motor. It worked, BUT the engine starts first time, I don't think it would survive with a sluggish starter.

I now have one of those little, cheapo solar chargers on it and was surprised to see that it had actually increased the terminal voltage while it was connected to the car with the alarm, clock etc drawing power.

[Keeping Up]

I did this two weeks ago. The Rangerover had been sitting for several weeks and the door lock wouldn't work. The battery was flat as a fart, not even a lamp glimmer. I didn't measure the voltage. I put it on the battery charger for 3 days and night and then put it back on the motor. It worked, BUT the engine starts first time, I don't think it would survive with a sluggish starter.

I now have one of those little, cheapo solar chargers on it and was surprised to see that it had actually increased the terminal voltage while it was connected to the car with the alarm, clock etc drawing power.

I tried that during the summer. The car was left for 4 months with a solar charger connected. On my return I found the battery down to 3 volts.

 

After 24 hours on the (not very good) charger, the battery was at 14.5 volts and had stopped taking any more current. It seems to work again; at least, the car starts again OK now.

[Gibbo]

I tried that during the summer. The car was left for 4 months with a solar charger connected. On my return I found the battery down to 3 volts.

 

You owe me a new keyboard.

[WotEver]

You owe me a new keyboard.

[nb Innisfree]

Cheap leisures, couple of hours charging per day with an occasional full 8hr charge and expect a max of 1 to 2 years, think of all the diesel you'll save not caring for them with all that '100%' charging. I suppose we could get 6 or 7 years out of good batteries but it would cost us thousands in diesel. By keeping to a minimal charging routine I reckon we save £1000 + per year in diesel, more than pays for regular batts renewal

[Keeping Up]

You owe me a new keyboard.

Well I thought it might work. One 12v Lucas solar charge panel on the dashboard where the sun would shine on it for most of the day, wired directly to the battery terminals.

 

It works on my wife's car OK, I hoped it would work for mine

 

Is your keyboard solar-powered?

[Justme]

Cheap leisures, couple of hours charging per day with an occasional full 8hr charge and expect a max of 1 to 2 years, think of all the diesel you'll save not caring for them with all that '100%' charging. I suppose we could get 6 or 7 years out of good batteries but it would cost us thousands in diesel. By keeping to a minimal charging routine I reckon we save £1000 + per year in diesel, more than pays for regular batts renewal

 

 

I'm not so sure.

 

I use a 6kva diesel genny to charge my bats.

 

Last year I bought 1000L of red at a cost of about £400 (this years 1000L cost £460 inc vat). I have used it in the genny, tractor & recently (about 150L worth) mini digger. I would guess that I have used about 600L in the genny but could be more or less

 

Since dec 08 the genny has dome 610 hours. So aprox 1L per hour (so about 40p). Thats about £244 per year for charging. Ok we also have solar but that really only makes a big difference for 2 or 3 months & minimal after that. We run from 100% to 50 or 60% then recharge to 100% again. We can last 4 days that way when 100% relying on the genny & the recharge takes about 8-12 hours. Plus the occasional EQ charge. Also whilst the genny is on we max out the power used doing stuff like laundry etc.

 

If I had to change my bats after 2 years & not 6 or 7 it would cost me 3 times as much in bats. As each bank would cost £600 ish it would cost me £1800 in bats to change them every 2 years. My total fuel for 6 years is only £1464.

 

 

As I expect my bank to last longer than 7 years I should save even more.

 

I think a big problem is having bat banks that are far to small & you are having to recharge them every day or two.

[Smelly]

How does the big bank/charge times thing add up? Wouldn't a bigger bank at a higher state of charge take longer to re-charge, hence offsetting the saved fuel costs? At least with cheap lead acid batteries at about £250 a pop to replace.

 

OTH, this post inspired me and I came up with this

which would make a very cost effective battery replacement for some ingenious board members who teamed up. There's a 48 volt one if you search but that'd need 4 people and organising boaters is like herding cats.

 

It's a shame they won't fit under our cruiser stern

[nb Innisfree]

How does the big bank/charge times thing add up? Wouldn't a bigger bank at a higher state of charge take longer to re-charge, hence offsetting the saved fuel costs? At least with cheap lead acid batteries at about £250 a pop to replace.

 

OTH, this post inspired me and I came up with this

which would make a very cost effective battery replacement for some ingenious board members who teamed up. There's a 48 volt one if you search but that'd need 4 people and organising boaters is like herding cats.

 

It's a shame they won't fit under our cruiser stern

 

We have 8 x 120 ah @ 24v with 100 a alt. When batts are new we can squeeze 4 days before charging but that req 8 hrs min. to get back to 100%. This soon deteriorates batts. We can replace daily usage in less than 1 hour when new but this regime doesn't last long before voltage drops. For someone relying solely on alternators, batts are definitely not worth slaving over and caring for with lots of diesel and engine wear.

 

Larger batt bank coupled with a correspondingly larger alt definitely reduces charge times but difficult to draw a line for optimum cost tho for full time liveaboard I think we are near ideal.

[Justme]

How does the big bank/charge times thing add up? Wouldn't a bigger bank at a higher state of charge take longer to re-charge, hence offsetting the saved fuel costs? At least with cheap lead acid batteries at about £250 a pop to replace.

 

OTH, this post inspired me and I came up with this

which would make a very cost effective battery replacement for some ingenious board members who teamed up. There's a 48 volt one if you search but that'd need 4 people and organising boaters is like herding cats.

 

It's a shame they won't fit under our cruiser stern

 

 

The way I see it I can put more total energy in during the bulk phase in the same time you do (bigger mains type charger not alts & bigger acceptance due to bigger bats) plus when I do get to the slow bit, my slow phase will take the same time as your slow phase but I am only doing it once for every 4 days or so (longer if we have had some sun). If I do a short charge to say 90% I loose more running time than you would expect by the missing 10%.

 

Even at £250 for bats thats about how much fuel I am using per year still.

 

Thats the second time today some one has tried to herd cats....

 

We have 8 x 120 ah @ 24v with 100 a alt. When batts are new we can squeeze 4 days before charging but that req 8 hrs min. to get back to 100%. This soon deteriorates batts. We can replace daily usage in less than 1 hour when new but this regime doesn't last long before voltage drops.

 

Thats sort of proves my point.

 

You get 4 days from your 960ah (at 12v) bank so have used 480ah.

I get 4 days from my 1550ah bank so have used 775ah

 

BUT we are both using about 8 hours plus to recharge.

 

Even if I use 12 (which is only if I am EQ'ing as well) I get 64.5ah per charging hour

At 10 hours I get 75.5ah

at 8 hours I get 96.8ah

 

At 8 hours you get 60ah per charging hour plus in your own words "This soon deteriorates batts." & "We can replace daily usage in less than 1 hour when new but this regime doesn't last long before voltage drops. " so you are still drastically under charging in both cases.

 

I am charging with a 120 amp charger & a 50 amp charger till the absorb phase then its just the 120 amp one.

[Smelly]

The way I see it I can put more total energy in during the bulk phase in the same time you do (bigger mains type charger not alts & bigger acceptance due to bigger bats) plus when I do get to the slow bit, my slow phase will take the same time as your slow phase but I am only doing it once for every 4 days or so (longer if we have had some sun). If I do a short charge to say 90% I loose more running time than you would expect by the missing 10%.

 

Even at £250 for bats thats about how much fuel I am using per year still.

 

Thats the second time today some one has tried to herd cats....

 

 

 

Thats sort of proves my point.

 

You get 4 days from your 960ah (at 12v) bank so have used 480ah.

I get 4 days from my 1550ah bank so have used 775ah

 

BUT we are both using about 8 hours plus to recharge.

 

Even if I use 12 (which is only if I am EQ'ing as well) I get 64.5ah per charging hour

At 10 hours I get 75.5ah

at 8 hours I get 96.8ah

 

At 8 hours you get 60ah per charging hour plus in your own words "This soon deteriorates batts." & "We can replace daily usage in less than 1 hour when new but this regime doesn't last long before voltage drops. " so you are still drastically under charging in both cases.

 

I am charging with a 120 amp charger & a 50 amp charger till the absorb phase then its just the 120 amp one.

 

Wierd, I seem to get more when I quote...

 

So bigger bank; disproportionately longer bulk phase... Or is it just a bigger charger that makes the difference?

[smileypete]

The way I see it I can put more total energy in during the bulk phase in the same time you do (bigger mains type charger not alts & bigger acceptance due to bigger bats) plus when I do get to the slow bit, my slow phase will take the same time as your slow phase but I am only doing it once for every 4 days or so (longer if we have had some sun). If I do a short charge to say 90% I loose more running time than you would expect by the missing 10%.

 

I think I'd just have two banks of bats.

 

Each bank would be sized for about 1 days use.

 

That way I can have one bank out of service and charge it 100%, while using the other bank.

 

Then swap over sometime, say once a week and so start using the 100% charged one.

 

cheers,

Pete.

[Justme]

Wierd, I seem to get more when I quote...

 

So bigger bank; disproportionately longer bulk phase... Or is it just a bigger charger that makes the difference?

 

 

I think if you size the charger (not charger not alt so when it says 120 amps I get 120 amps, well at the start any way) to the bank then the bulk phase can be similar for all banks. Trouble with a bigger charger is you will have a longer absorb phase. But on the whole worth it overall.

 

 

 

I think I'd just have two banks of bats.

 

Each bank would be sized for about 1 days use.

 

That way I can have one bank out of service and charge it 100%, while using the other bank.

 

Then swap over sometime, say once a week and so start using the 100% charged one.

 

cheers,

Pete.

 

 

Even better is to use one to absorb charge the other so you only ever bulk charge using fuel. But you lose total capacity by splitting the bank.

[Ermenilda]

OK many thanks for all the replies am gonna try and reply to all to see if I can steer this topic back on track?

 

here goes...

 

If you need an inexpensive solution to get you buy whilst you think about the way forward, one of the chaps on here (Vince1969) has been passing on batteries that have had light UPS standby duty for their allotted time, get changed automatically, and only apparently had "light use".

 

many thanks for the heads up Nickhlx - most appreciated, good to know and will keep it in mind

 

Re-read my post. Particularly the part about how long it takes. A few years ago Mrs Gibbo sulfated the batteries on our boat. It took 3 days of continuous equalise charge to get them right again.

 

OK - I hear(d) what you are saying but this is the case WHEN they get sulfated - what I have been saying is that the blimmin things must never have taken a decent charge from when they were first installed on the boat - so why was that? OK - it would seem by all accounts that NOW they are sulfated - but what does that mean was wrong with them before?

 

Letting them drop to anywhere near 10v is just silly and wasting servicable batteries.

 

thanks Phylis - couldn't agree more! I don't want them to be 10v - honest!

 

You can do without a proper battery monitor if you have an accurate battery voltmeter and decent charge ammeter, and know how to interpret them.

 

thanks smileypete! every multimeter I have ever owned seems accurate enough to me. SIDE NOTE:- someone said about a clamp meter not being very accurate - I just put the multimeter in line between the mains battery charger (I have them plugged into the mains and charging in a flat as I type) and at the same time had the clamp meter on - both measured exactly the same amps which was 1.82A - so I would conclude the things are pretty darn accurate even down to these low amps

 

A rule I learnt several years ago that applies to the average boater:-

 

However long you think it takes to fully recharge lead acid batteries, treble it and you might be close.

 

It does indeed seem to be about right.

 

*cough cough* (doff cap etc.) beggin yer pardon sir but where might one find a professional boater I could have a word with please? what do they do with their batteries? we're all in the same boat aren't we? (not another pun!)

 

One thing that I can't see anywhere in your posts, is exactly what you are powering from your batteries that are flattening them in such a short space of time. Some idea of the load that you are placing on them, might help to diagnose the problem.

 

BRAVO! When I was doing the tests I had three lights on each pulling ~1.2A and had the inverter on with no load which pulled ~1A - I didn't run the tests with anything plugged into the inverter as I was only wanting to 'put a load' on to get the results but since seeing all these measurements I would say probably about 10A would be a good 'over'estimate to work with

 

Perhaps it time to throw away the battery cataloges and get the generator mags out.

 

A nice, built in, water cooled, cocooned 'on demand' diesel generator starts to look an attractive option if you look at all the problems people have with batteries.

 

I would stab a guess that this is what a 'professional' (loaded) boater does? Give up on the batteries and install a mini power station - I'll go with that but sadly lack the £££'s and/or willingness to put such a (most likely) expensive piece of kit into an old(ish) boat

 

Or put them to one side and head over to http://www.batteryfaq.org/

 

nice one smileypete! I've never come across this before on my travels through the 'net but looks good and will take a look through it - many thanks!

[Ermenilda]

Relating this to automotive industry, I regularly have to deal with completely flat batteries, we simply put a booster pack on, crank the engine, vehicle starts and seemingly proceeds with no problem. If we were writing off batteries through letting them go flat it would cost a fortune in replacement costs yet the need to replace them very rarely occurs.

 

right ok... kinda makes you think don't it? are batteries really as fragile as people seem to think they are?

 

That's because the capacity used to start the motor is so small compared to the full capacity of the battery and the electrical system is run from the alternator. If you were trying to use the reserve capacity with engine off you would most likely find it gone!

 

right yup - agree is a different story in the 'automotive world' as the battery gets caned starting the car but then the alternator provides the current for all the electrical stuff anyway and the battery slowly takes back the charge it just chucked out. Most people don't live in their car so there will be no draw on the batteries 'whilst they're out'

 

If you run side by side tests leaving the headlamps on with a new vehicle and one that has had the battery go flat you'll find a dramatic difference.

 

OK - so you are saying that in this situation (a car battery that got knacked and 'rejuvenated') it will have lost it's capability to be a 'good' battery - fair enough - makes sense I guess

 

Cheap leisures, couple of hours charging per day with an occasional full 8hr charge and expect a max of 1 to 2 years, think of all the diesel you'll save not caring for them with all that '100%' charging. I suppose we could get 6 or 7 years out of good batteries but it would cost us thousands in diesel. By keeping to a minimal charging routine I reckon we save £1000 + per year in diesel, more than pays for regular batts renewal

 

Hi nb Innisfree - are you an average or professional boater then? I think I would put you in the average yet realistic category

 

I'm not so sure.

 

I use a 6kva diesel genny to charge my bats.

 

***snipped out to save space - hope that's OK?***

 

 

As I expect my bank to last longer than 7 years I should save even more.

 

I think a big problem is having bat banks that are far to small & you are having to recharge them every day or two.

 

 

OK - but what is the point of all the K's if all you can push into a battery is a handful of amps - I would have thought you would be spending more on fuel than you are putting into the batteries but it sure seems like you've done your sums and it all looks good.

 

But this brings me onto what (most may shout out in unison) is completely obvious and there is no way of getting away from - 'you have to put back the amps you take out' so I guess it's great if it is a silent thing built in under the deck and all the bells and whistles (believe me I would LOVE something like that) but a good ol Lister SR2 running for 8-12 hours is gonna bring on some seriously p'd off neighbours knocking on your door!

 

but really though - dredging back all the 'knowledge' - it's not just about having a whacking great battery bank coz whilst it might mean that you can sit with your feet up gobbling all the kW for a few days - you're gonna have a helluva time getting all those amps back into the batts... OK so lets get a whacking great big generator/charging system and we'll have those suckers charged up in no time! NOPE! sorry but if you want to charge these batteries up you are going to have to be nice to them and drip feed them bit by bit because they won't take more than they want (but this also made me re-think - how come the mains battery charger I have plugged in now is able to push ~3A on 'slow' - ~5.5A on fast and ~20+A on boost? I thought a batt would only 'take what it wants/can...?!?')

 

so how are the professional boaters really doing it? (my guess is they have a silent mega bucks diesel genny mentioned earlier purring away under the deck how else can they do it? surely they are mere mortals just like us average boaters using similar batteries/charging etc... but somehow able to suck kW of leccy out on a daily basis!

 

OTH, this post inspired me and I came up with this

which would make a very cost effective battery replacement for some ingenious board members who teamed up. There's a 48 volt one if you search but that'd need 4 people and organising boaters is like herding cats.

 

link doesn't work! very intrigued to see what you've found!

 

 

in regards to the last few posts - this sounds more like it! Some real world experiences from average boaters (sorry if I offend any of you with this! ) and this is more along the lines of what I have been thinking about in order to come up with the next (stoopid no doubt) question/statement/theory->

 

"Why couldn't it be possible to have lots and lots of very low Ah batteries (I mean like 20Ah) with a junction box feeding from the alternator to EACH and every battery individually (like a large cable from the alternator with 'octopus legs' of smaller cables running to each of the batteries). This way the alternator would happily deliver the Amps to each of the batteries -> would run closer to its full rated output -> and the batteries would keep their 'cream' (90-100% charged bit) Then when it comes time to draw the power only this cream is skimmed off each of the batteries which in return can then be 're-creamed' with the octopus' hahahah

 

make sense? a load of old tosh? just the equivalent of a big bank/no different?

 

whaddya reckon experts?

[tomsk]

The Experts will undoubtedly advise you to buy a box of battery charge control gubbins which will solve all your problems in one fell swoop.

[Smelly]

try again

 

that seems to work... 24 volt forklift battery!

[Roger Gunkel]

BRAVO! When I was doing the tests I had three lights on each pulling ~1.2A and had the inverter on with no load which pulled ~1A - I didn't run the tests with anything plugged into the inverter as I was only wanting to 'put a load' on to get the results but since seeing all these measurements I would say probably about 10A would be a good 'over'estimate to work with

 

I must be a bit thick here, but I'm not sure why the response 'Bravo' to my question, or why there is no information on what you are powering from the batteries! I understand that during your tests you were only taking a limited ammount of amps, but that was presumably after the batteries had already started giving problems.

 

You mention an inverter, so presumably you have mains powered items on board. 10amps for 5mins is perhaps a little different from 10amps for 24 hours, so more information would be useful. When you first installed the batteries in the boat, what were you running from them? TV, fridge, lights pumps, washing machine etc. etc, and for how long?

 

To know what sort of drain over how long a period, might help to give some insight into how your new batteries first became run down to 10v.

 

Roger

[Gibbo]

"Why couldn't it be possible to have lots and lots of very low Ah batteries (I mean like 20Ah) with a junction box feeding from the alternator to EACH and every battery individually (like a large cable from the alternator with 'octopus legs' of smaller cables running to each of the batteries). This way the alternator would happily deliver the Amps to each of the batteries -> would run closer to its full rated output -> and the batteries would keep their 'cream' (90-100% charged bit) Then when it comes time to draw the power only this cream is skimmed off each of the batteries which in return can then be 're-creamed' with the octopus' hahahah

 

I'm not sure how to answer this so that the answer will come across clear so I'll take it in steps:-

 

Two x 20Ahr batteries in parallel is exactly the same as having a single 40Ahr battery (assuming correctly wired up - see below). Two 40Ahr batteries in parallel is exactly the same as a single 80Ahr battery and so on. So that part of the "question" becomes irrelevant. Just have one big battery. It makes no difference how many individual batteries make up the bank (again subject to being wired up correctly).

 

The "octopus legs" bit is really nothing more than making sure the batteries are properly balanced - http://smartgauge.co.uk/batt_con.html

 

So the conclusion "This way the alternator would happily deliver the Amps to each of the batteries -> would run closer to its full rated output -> and the batteries would keep their 'cream' ............." is completely incorrect.

 

And just to clarify (as there often seems to be some confusion on this point):-

 

Some people seem to think a bigger battery bank, with a bigger charger will take longer to charge (we even had a mathematician who [incorrectly] proved this). It is wrong. A 100Ahr bank with a 10 amp charger will take exactly the same time to charge as a 1000Ahr bank with a 100 amp charger. This can be proved mathematically but there's no need. It's so bl**din' obvious!

 

Finally, it is easy to speed up the bulk stage. Just put a bigger charger in. However the biggest part of the charge cycle is the acceptance stage. And that cannot be shortened. It is down to the batteries (not the charger - assuming the acceptance voltage is correct). For this reason, doubling the size of the charger actually makes much less difference to the total recharge time than many would imagine. A very rough guess would be that doubling the size of the charge will reduce the total recharge time by about 20% but obviously it varies greatly depending upon the precise relative sizes.

Edited October 22, 2009 by Gibbo

[Chris Pink]

I think I'd just have two banks of bats.

 

Each bank would be sized for about 1 days use.

 

That way I can have one bank out of service and charge it 100%, while using the other bank.

 

Then swap over sometime, say once a week and so start using the 100% charged one.

 

cheers,

Pete.

 

I am running this system

 

On about 2 weeks charging one bank to 80% at around 2 hours a day and the other just charging on a slower charger

 

Trouble is how do i know whether it works or not?