Batteries

[FadeToScarlet]

Hello all,

 

I believe that my five leisure batteries- 110AH maintenance free gel type- are coming to the end of their lives.

 

They never last more than 5 or 6 hours after a full day's cruising, i.e. the fridge compressor starts pulsating because there's not enough power to run it.

 

Over the past few days, I've borrowed a decent charger from Roger Gunkel, and have been steadily charging away, first at 30A, then 10A, and then at 2A.

 

Having done that for a few days, the voltages of each individual battery are as follows:

 

13.33

13.50

13.53

13.37

13.23

 

Despite them being wired in parallel, they're all different voltages; is the 0.3V difference between the "best" and "worst" worth worrying about? It's not as if there's one battery that's glaringly obviously pulling the others down. Also, Roger's diagnostic charger didn't point to any faults with any of the individual batteries.

 

At the moment, I've taken the bank apart (three leisures were stacked on top of two leisures and the starter battery in plastic crates) and I'm running the fridge- and one 12v fluorescent light- from two of the batteries- those with 13.37 and 13.23 volts- and I've been recording the voltage change over time.

 

15:40 - 13.06V

16:20 - 13.00V

17:30 - 12.98V

18:30 - 12.91V

19:30 - 12.7V

20.30 - 12.6V

22:00 - 12.6V

23:00 - 12.5V

23:24 - 12.19V

 

The fridge compressor started pulsating at 12.19V just now.

 

Those two batteries went from being as fully charged as I could get them, to not being able to run the fridge, in just over 7 hours.

 

The fridge shouldn't draw more than 4A, apparently; either way, those two batteries- which should give me 220AH of power, therefore lasting about 41 hours or so (fridge plus one light) last barely 8.

 

I intend to repeat the test on the other three batteries tomorrow- seeing how the voltage drops over time.

 

It appears to me that the batteries are, basically, not holding the charge; the other three appear the same.

 

So, basically, I've got several questions:

 

1) How can I measure the current the fridge is drawing? I've borrowed a multimeter and tried using it across the fuse for the fridge, which gave a reading of 3A; is this the correct way of doing it?

 

2) What do people think about the state of the batteries? All are performing similarly; they're at least 4 years old; is it time to bite the bullet and buy some new ones? I'm thinking of getting a couple of new 110AH batteries; two brand-new that actually work are better, presumably, than 5 that don't work properly!

 

Looking back at all that, it looks pretty clear to me that the batteries are shot! But, before I go to the expense of buying new ones, I want to find out what the fridge is drawing; if it's that which depletes them. It's got a 10A fuse, though, so presumably it's not drawing more than that, and it's the batteries that are rubbish!

[OptedOut]

I would have thought a 12 volt fridge would continue as normal at over 12 volts, is the test meter accurate.

Where are you taking the voltage reading?

Edited October 30, 2008 by OptedOut

[FadeToScarlet]

It's a reasonably swish multimeter that as far as I'm aware is accurate.

 

The readings were taken across the battery terminals directly, to see what voltage was in the battery at each time.

[alan_fincher]

Hi,

 

Firstly I'm no expert, but.....

 

Leisure / domestic batteries take quite a hammering, having to be continually deliberately part run down then recharged.

 

By comparison your starter battery has a much easier life, being generally kept fully charged, (which prolongs life), and needing only to deliver a quick (albeit big) dose of amps every few hours (or days) to start the engine.

 

Longevity of domestics will depend on how well looked after, and how often put through discharge/charge cycle. If never, ever, more than half discharged, and kept topped up with water, they will last well, particularly on a boat used only for holidaying. If receiving heavy liveaboard use, regularly heavily discharged, or not topped up when low on water, they will last much less long.

 

Frankly 4 years is pretty good, even in the optimal situation, and I suspect yours are now well knackered.

 

Some specifics:

 

(Assuming an accurate voltmeter) the 12.2 or so volts point at which your fridge is playing up should stll represent a battery about 50% charged. A that point it should be charged anyway, but a fridge shouldn't really be that sensitive to object to 12.2 volts. Is it possible you are measuring 12.2 volts at the battery, but that the fridge is at the end of a length of wire with volts drop, so "seeing" a lot less ? To know what the fridge will tolerate, you need to measure at the fridge.

 

You can measure current to the fridge, by measuring in-line, were the fuse should be. So across the fuse holder, with no fuse present, but not "across the fuse". I'm sure that's hat you probably meant. Although it may show 3 or 4 amps only when running, most take a much bigger surge to start. That may well be more than the 10 amps indicated by the fuse, because most fuses can take much higher currents for a short instant, than they can if it's applied continually.

 

12 volt fridges are fussy things and need much more meaty cable than they are often (largely because of the startup surge just mentioned).

 

I think you will need new batteries, but need to do a power audit to see ho big a bank you need, and what the implications will be for keeping them recharged. Search the forum for "+power +audit", for example.

 

Alan

 

Some update after my post jus made....

 

If you are measuring volts at the battery, it will not tell you what the fridge is getting, when it starts getting the jitters. Measure it at the fridge, and it may well be less than 12 volts.

 

My comment that 12.2 volts would normaly represent a battery still half charged is true only of "open" lead acid batteries.

 

I note yours are sealed gel, so that's prrobably not the "half charged" voltage for them, I suspect.

[OptedOut]

It's a reasonably swish multimeter that as far as I'm aware is accurate.

 

The readings were taken across the battery terminals directly, to see what voltage was in the battery at each time.

 

I think the above post by Alan sums up the possibilities.

Edited October 30, 2008 by OptedOut

[Roger Gunkel]

Hi James,

 

I'll drop round tomorrow morning and have a look with you, though my electrical knowledge is mainly picked up from this forum!

 

I noted that you are running on two of the 110AH batteries to test them, so your useable power will considerably less than the rated AH. It has also been very cold lately, which will further reduce battery efficiency. Add on to that the ageing degredation of the batteries and the fact that they have probably been run low quite often leading to sulphation and your performance figures are probably not far out.

 

See you later,

 

Roger

[Guest TerryL]

Hello all,

 

I believe that my five leisure batteries- 110AH maintenance free gel type- are coming to the end of their lives.

 

They never last more than 5 or 6 hours after a full day's cruising, i.e. the fridge compressor starts pulsating because there's not enough power to run it.

 

Over the past few days, I've borrowed a decent charger from Roger Gunkel, and have been steadily charging away, first at 30A, then 10A, and then at 2A.

 

Having done that for a few days, the voltages of each individual battery are as follows:

 

13.33

13.50

13.53

13.37

13.23

 

Despite them being wired in parallel, they're all different voltages; is the 0.3V difference between the "best" and "worst" worth worrying about? It's not as if there's one battery that's glaringly obviously pulling the others down. Also, Roger's diagnostic charger didn't point to any faults with any of the individual batteries.

 

At the moment, I've taken the bank apart (three leisures were stacked on top of two leisures and the starter battery in plastic crates) and I'm running the fridge- and one 12v fluorescent light- from two of the batteries- those with 13.37 and 13.23 volts- and I've been recording the voltage change over time.

 

15:40 - 13.06V

16:20 - 13.00V

17:30 - 12.98V

18:30 - 12.91V

19:30 - 12.7V

20.30 - 12.6V

22:00 - 12.6V

23:00 - 12.5V

23:24 - 12.19V

 

The fridge compressor started pulsating at 12.19V just now.

 

Those two batteries went from being as fully charged as I could get them, to not being able to run the fridge, in just over 7 hours.

 

The fridge shouldn't draw more than 4A, apparently; either way, those two batteries- which should give me 220AH of power, therefore lasting about 41 hours or so (fridge plus one light) last barely 8.

 

I intend to repeat the test on the other three batteries tomorrow- seeing how the voltage drops over time.

 

It appears to me that the batteries are, basically, not holding the charge; the other three appear the same.

 

So, basically, I've got several questions:

 

1) How can I measure the current the fridge is drawing? I've borrowed a multimeter and tried using it across the fuse for the fridge, which gave a reading of 3A; is this the correct way of doing it?

 

2) What do people think about the state of the batteries? All are performing similarly; they're at least 4 years old; is it time to bite the bullet and buy some new ones? I'm thinking of getting a couple of new 110AH batteries; two brand-new that actually work are better, presumably, than 5 that don't work properly!

 

Looking back at all that, it looks pretty clear to me that the batteries are shot! But, before I go to the expense of buying new ones, I want to find out what the fridge is drawing; if it's that which depletes them. It's got a 10A fuse, though, so presumably it's not drawing more than that, and it's the batteries that are rubbish!

Your batteries are unlikely to have the same capacity after 4 years especially if undercharged as they seem to be. A drop test will give an idea as to condition and may reveal the really bad ones. You should only discharge batteries down to 50% so the maximum possible capacity available of your two batteries can only be about 20 hrs not 41 and usually much less if never fully charged. The more battery capacity you can use linked together and increase the discharge time, the more this will improve the total output from them all so splitting the batteries up will also reduce the proportional capacity available. The fridge and flourescent will have consumed about 14 AH assuming a 12 watt light so that's considerably less than the 100 AH possible. 2 x 110 AH batteries are not very much even new and would only be likely to keep this load going for 24 hrs unless they were able to be fully charged every day.

 

http://www.waeco.co.uk/page.aspx?page=powercon&s=4

 

The other issue seems to be voltage drop to the fridge so check the voltage there and look at your charging system for improvements. If the current batteries are not lasting more than six hours now on your normal load and charging capacity then at a rough guess it would seem that you do need 5 x 110 AH batteries for about 36 hrs guaranteed maximum continuous use, more if the charging is improved but to be more accurate you need to estimate your total load over 24 hrs.

[FadeToScarlet]

Hi again all,

 

Thanks for the replies thus far.

 

Having looked over the batteries this morning with Roger, it appears that they've been wired up incorrectly- I'll do a diagram and post it later, together with what I think is the correct way, so that people can offer criticism, constructive or otherwise!

 

The first job is to connect all the batteries properly- then I'll be able to see if, after a proper charging, whether they last.

[FadeToScarlet]

Aha!

 

I think the majority of the problem is because the batteries have been wired up incorrectly.

 

It looks like there was originally one starter and two leisure batteries, and then the previous owner put three more batteries in a crate on top of them (hence the long leads between batteries #3 and #4 in the diagram below) which means that, whilst the domestic use comes from the entire bank, only two of the bank are directly being charged- the other htree are leeching charge from those batteries, hence the poor performance.

 

(In the diagram, the crossing wires below the selector switch aren't joined together- it's just that way because I can't work out how to do the little half-circle thing to show they aren't joined together in Word. Silly libary computer, doesn't even have Paint...)

 

http

://www.4shared.com/file/69162410/f20ab...ent_Setup.html

 

The solution is to rewire.

 

I want to put all the batteries in a line, so I can have all the connecting leads the same length, and then reconnect them like this:

 

http://www.4shared.com/file/69163076/f2867...deal_Setup.html

 

This way, all five of the battery bank will be charged simualtaneously. It might well be that the batteries are OK with a decent charge- I'll rewire them first (the cheapest option!) and see if that makes any difference.

 

(Thanks to Roger Gunkel for helping me figure this all out and pointing me in the right direction. )

Edited October 31, 2008 by FadeToScarlet

[Nickhlx]

I think there will be people who will disagree with this method of wiring them up...

 

I am not sure though how to improve it - perhaps with different length links and feed points.

 

It was recently debated for a bank of 4 and that is easy to understand, but for 5 the only way I can think

at the moment is to have a common point for the +ves and -ves, and then equal length leads going to

each battery from these points.

 

It was well debated a few weeks back.

 

Nick

[bottle]

Gibbo's (Smartgauge) page on wiring batteries to form a bank.

 

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

[alan_fincher]

Sorry to be a dampener, but my gut feel is that rewiring the battery bank another way isn't actually going to revive your tired batteries.

 

I suspect you will find that even if not completely shot, you will never get them back anywhere near their design capacity.

 

But for your sake, I hope my feelings are wrong!

 

Alan

[bottle]

Alan maybe right but sorting out the wiring will not do any harm.

 

Fingers crossed.

[FadeToScarlet]

Sorry to be a dampener, but my gut feel is that rewiring the battery bank another way isn't actually going to revive your tired batteries.

 

I suspect you will find that even if not completely shot, you will never get them back anywhere near their design capacity.

 

But for your sake, I hope my feelings are wrong!

 

Alan

 

Well, I'm not too disappointed! I know the batteries are looking knackered, and they won't get back to near their design capacity; but if this makes them last any longer then they currently do, then it's an improvement.

 

I'm looking at replacing the bank soon anyway, it's just a case of holding on until then; I think that rewiring so that they're used properly can't hurt.

 

I'm just about to look at Gibbo's page; I may well come back with an updated design!

[Guest TerryL]

Aha!

 

I think the majority of the problem is because the batteries have been wired up incorrectly.

 

It looks like there was originally one starter and two leisure batteries, and then the previous owner put three more batteries in a crate on top of them (hence the long leads between batteries #3 and #4 in the diagram below) which means that, whilst the domestic use comes from the entire bank, only two of the bank are directly being charged- the other htree are leeching charge from those batteries, hence the poor performance.

 

(In the diagram, the crossing wires below the selector switch aren't joined together- it's just that way because I can't work out how to do the little half-circle thing to show they aren't joined together in Word. Silly libary computer, doesn't even have Paint...)

 

http

://www.4shared.com/file/69162410/f20ab...ent_Setup.html

 

The solution is to rewire.

 

I want to put all the batteries in a line, so I can have all the connecting leads the same length, and then reconnect them like this:

 

http://www.4shared.com/file/69163076/f2867...deal_Setup.html

 

This way, all five of the battery bank will be charged simualtaneously. It might well be that the batteries are OK with a decent charge- I'll rewire them first (the cheapest option!) and see if that makes any difference.

 

(Thanks to Roger Gunkel for helping me figure this all out and pointing me in the right direction. )

 

This looks fairly straight forward to me giving an even charge to all batteries with a simple battery switch. I like it and hope it does something for the batteries.

[FadeToScarlet]

Gibbo's (Smartgauge) page on wiring batteries to form a bank.

 

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

 

Thanks for the link- I wish I'd seen that before doing all the head-scratching earlier!

 

I think the design I came up with- although not the theoretical optimum, with all the interconnecting links being the same, it is the practical optimum. If that makes sense...

 

Right. Tommorow morning, it's time for rewiring!

[FadeToScarlet]

Well, I now know which battery is a dud.

 

Having it smoking, a very sulpherous smell, too hot to touch, and spitting out electrolyte is a fairly good indicator!

 

I've disconnected it from the bank- hopefully, without the duff one, the bank will perform slightly better until I can get some new batteries.

[John Orentas]

I'm not getting involved with this thread but I would only advise that you can't possibly test your batteries in any way while they are connected together and by extension you cannot possibly charge them if one of them is defective as it looks more than likely to me that it is the case..

 

Separate them, then test and charge them individually.

[alan_fincher]

Having it smoking, a very sulpherous smell, too hot to touch, and spitting .............

 

Sounds a bit like some of the participants in the most fiercely argued electrical threads!

[FadeToScarlet]

I'm not getting involved with this thread but I would only advise that you can't possibly test your batteries in any way while they are connected together and by extension you cannot possibly charge them if one of them is defective as it looks more than likely to me that it is the case..

 

Separate them, then test and charge them individually.

 

Thanks for the valuable advice. I've already done that; now, I've reassembled the bank and, as we're going to be away from shore power for the next few days (as usual) we'll see how long they last, checking the voltage of them and so on, to get a better picture of how they're performing.

 

 

Sounds a bit like some of the participants in the most fiercely argued electrical threads!