Testing batteries

[Avocet]

I have a cheap 95Ah "leisure" battery that's only a couple of years old but doesn't seem to take a charge properly (or hold what charge it has for very long). Left it for 6 weeks once and came back to find not even enough "juice" to power the instrument displays. I checked for small battery drains but there is absolutely no current flowing when the master switch is off. I use this battery for starting as well as domestic use (its only a small engine with a decompressor) and I'm wondering whether I've buckled some of the plates by asking it to crank the engine. I can't measure the cranking current but I don't think it's very large. I was going to take it to my local motor factor and ask him to "load test" it but then I thought "hang on, that's just what I'd do if I was starting the engine!" Is there a way of testing these batteries without damaging them? Has anyone done a load test on a leisure battery and lived?

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[Phil]

Starting the engine with a "leisure" battery is not a problem, especially one your size.

Is the battery being properly charged in the first place?

Have you in the past shorted it out or flattened it totally, as this can cause a substantial reduction in charge capacity when charging after the event.

Had cheap leisure batteries on a liveaboard for thre years with no problems.


Phil

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[Jools_of_Top_Cat]

Have you tried emailing your question to the manufacturer?

If anyone should know, they should!

<hr width=100% size=1>Julian

<A target="_blank" HREF=http://www.topcatsail.co.uk/TC_IrishCruise_2003_00.html>Irish Cruise</A>

 

[DavidBolger]

I had much the same problem with my batteries a few weeks ago. As you are aware, with low cost leisure batteries they cannot be discharged too many times before they lose all their capacity. It sounds to me that this might be the case with your battery. In order to do a load test, have the battery fully charged. Connect a volt meter to the battery. Now crank your engine over for 15 seconds and watch what happens to the volts. If it drops below 10.5 volts, the battery is dead. If it drops quickly but stays above 10.5 volts and ideally above 11.5 volts, the battery has passed its load test and would seem to have a decent bit of capacity left in it. When cranking the engine, make sure it doesn't start. I do this by opening the decompression lever. If you do a hydrometer test, this will also give you a lot of information on the battery.

Hope this helps.

David

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[Evadne]

Is it still under warranty? If you know you didn't damage it yourself then it would be worth a claim. Cheap car-type batteries come with a 3-year guarantee which, the man assured me, is not dependent on it being used in a car, although I assume it doesn't include accidental discharge damage. I'd have hoped for at least the same from a leisure battery.

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[andyball]

I'd say that as low as 9V is fairly normal in some battery/starter applications, esp when v.cold.. It might not be ideal, but can be observed in practice in systems that work reliably. If you prevent starting with a decompressor, of course you'd expect a higher voltage since the starter will have less work to do.

<A target="_blank" HREF=http://www.uuhome.de/william.darden/testing.htm>here</A> is one of many pages about batteries on the site,this covers battery testing with the minimum of equipment.

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[dickh]

To prevent the engine starting when cranking and checking volts; pull out the stop control. If you use the decompressor, you will not put a normal starting load on the battery.

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[Avocet]

Thanks all,

It's only ben completely flattened once and why that happened is a bit of a mystery to me. I can only assume I forgot to turn the master switch off. The other thing I should have mentioned is that I have an 11amp automatic Halfords car battery charger. Do I need something with a bit more "grunt" for a battery this size?

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[andyball]

more grunt?

depends how flat you run the batteries b4 recharging & how long the charger has to do its stuff.

I've used a 4 amp charger for even larger batteries... & e v e n t u a l l y it'll bring 'em up to 15V or more, if a couple of days have passed.

If it's automatic, you probably leave it on all week ? an 11Amp one is fine.....but! it's worth checking the voltage that it automatically stops at : most of these chargers are aimed at cars (doh!) where squeezing the last 20% in isn't really an issue & possibly some cheap ones may simply keep the voltage below (say) 14.2V & leave it at that : you'll never get a full charge in the same way as a clever charger should. Also, if there isn't a "float" mode(13.8V or less) then leaving the battery at (say)14.4V week in/out won't help it's life much. Some people fudge round that with a timer switch so the charger's not on constantly.(you can buy 7 day ones, so eg after a weekend it might be on for mon/tues, then back on friday morning)

Having said that, a 95AH leisure batt. shouldn't cost much , so it may not be worth trying to get everything perfect.

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[Guest]

As I understand it a Leisure Battery is ONLY designed for domestic use and depper discharge than a traction battery. I also believe that a leisure battery is softer in deign plates than the traction type.

Trying to use a leisure battery on any starting medium will call for a high current shortening its life drastically - decompression or not.
The traction job does not like being discharged down too far or it finds it hard to recover, but will sustain high cranking currents.

I used to have a traction for starting / back-up and a leisure for domestic ......... stopped it for two larger traction jobs.

The batterys are charged at every opportunity so never really is an issue about leisure / traction on the domestic side. But at least I know that I can start my engine from either battery.

Previous boats had single battery's - I was glad when I upgraded to 2 !!


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[LadyInBed]

Your charger should be more than adequate for your battery.
Assuming that you can get into each cell, I would suggest taking the battery home, check that each cell is topped up to the correct level then put it on charge for about 6 hours.
Next stop charging and leave it to rest for half an hour or so, then check each cell with a hydrometer to ascertain the state of charge. If all the cells are at the same state of charge (hydrometer reads the same for all cells) all well and good, resume charging checking as before with the hydrometer until the hydrometer indicates full charge (1275 or all but one of the balls floating, depending on the flavour of the hydrometer).
If, when you check, one or two cells are at a much lower state of charge, then these cells have a problem and the terminals will never reach full voltage. But all is not lost, if you can continue charging at a reduced charge rate (trickle charging), the low cells can sometimes recover but at the cost of overcharging the good cells.
The alternative is to buy a new battery.


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