How do I know if my battery is fading out?

[Halo]

I have 2 x 110 AH batteries which were made on 2005.
They have had a very easy life being on trickle charge via a top o the range mains charging system when not in use
I dont have a "battery tester" but woonder what is the best way to test the condition - should I leave a light on and see how long it takes for the volts to drop for example?
thanks in advance
Martin

 

[VicS]

I have 2 x 110 AH batteries which were made on 2005.
They have had a very easy life being on trickle charge via a top o the range mains charging system when not in use
I dont have a "battery tester" but woonder what is the best way to test the condition - should I leave a light on and see how long it takes for the volts to drop for example?
thanks in advance
Martin

Best way if they are not sealed is probably to get a hydrometer and check the electrolyte density.

I personally, or if sealed, check the volts with a digital voltmeter after resting for 12 hours with no charge or discharge. A good battery should read 12.7 or 12.8 ish volts.

Both methods give an indication of the state of charge but do not guarantee they will perform well esp as starter batteries

 

[reeac]

Assuming that they are dual purpose house + starter batteries and that they aren't powering anything then switch off the charger for a month and then see how easily they start the engine. If they're just house batteries then as already suggested, check the decrease in rest voltage for a month or two.

 

[vyv_cox]

There is a method involving drawing a relatively high current using a couple of big incandescent bulbs for a few hours, then checking voltage. I don't remember the details but it has come up several times and a search will probably find it.

 

[GHA]

http://www.instructables.com/id/AmpHourTest/?ALLSTEPS is one way.

I'm in the middle of building a tester with an arduino board, shame you're not a bit closer.

 

[EdWingfield]

I use the guy that services the local lifeboat batteries. He's got a reputation to maintain and won't con you into unnecessary replacements.

 

[JohnGC]

Best way if they are not sealed is probably to get a hydrometer and check the electrolyte density.

I personally, or if sealed, check the volts with a digital voltmeter after resting for 12 hours with no charge or discharge. A good battery should read 12.7 or 12.8 ish volts.

Both methods give an indication of the state of charge but do not guarantee they will perform well esp as starter batteries

+1.

Even better if you can measure the acid temperature and use the figure to correct the specific gravity reading.

Your local/favorite vehicle technician will probably have a tester that will quickly (a few seconds) test the cold cranking ability of a starter battery.

 

[ghostlymoron]

Unfortunately the garage type tester won't tell you anything useful about a 'leisure' battery capacity.
Halo, do you think you have a problem or just looking to the future?

 

[jwilson]

I croc clipped an old 55 watt headlamp to a suspect 80AH battery after charging, after about 6 hours battery voltage was down from 13 to 10.5 which represents about only 28 amp/hours taken out. Decided battery was shot as you ought to be able to get about 50% of the nominal capacity before the voltage drops that much.

 

[William_H]

Battery is as battery does. First question is will each battery start the engine with some enthusiam. Second test is will each battery power your lights fridge etc for the amount of time you need? ie overnight or longer. having 2 batteries is excellent as a backup so that should one fail to start the enginethen both should hopefully do the job but you will know you need new batteries. In other words stop worrying you have a redundancy system which is more than you have in your car. Possibly your car battery performance is more critcal than your boat. So just wait until it is obvious battereies are dead then buy new ones. good luck olewill

 

[William_H]

I croc clipped an old 55 watt headlamp to a suspect 80AH battery after charging, after about 6 hours battery voltage was down from 13 to 10.5 which represents about only 28 amp/hours taken out. Decided battery was shot as you ought to be able to get about 50% of the nominal capacity before the voltage drops that much.

I would say you are being over fussy especial;ly if it is part of a duel battery set up.. To actually get 28AH out of an 80AH battery while not brilliant is quite good I would say. In most cases you will get more more useful life out of it. But if you want to be obsessive have a new one. olewill

 

[CAPTAIN FANTASTIC]

By far the easiest and reliable way is to leave the batteries without charge for a week or so and then check if the voltage has dropped. If they show no less than 12.7 then the batteries are good. Holding the charge is the most critical issue.

 

[vyv_cox]

By far the easiest and reliable way is to leave the batteries without charge for a week or so and then check if the voltage has dropped. If they show no less than 12.7 then the batteries are good. Holding the charge is the most critical issue.

Unfortunately not true. My Red Flash starter battery holds a charge perfectly well, still 12.4 volts after 9 months for example, and 12.7 for weeks on end. But it is totally dead, won't turn the engine over.

 

[ianj99]

I would say you are being over fussy especial;ly if it is part of a duel battery set up.. To actually get 28AH out of an 80AH battery while not brilliant is quite good I would say. In most cases you will get more more useful life out of it. But if you want to be obsessive have a new one. olewill

I disagree. The best way is indeed to measure the capacity by attaching a known (ie real world) load as jwilson suggested.

However, I would then check the open circuit voltage to see what it recovers too once the load has been removed at 10.5v because you can also tell the charge remaining by the rested open circuit voltage according to Trojan's table below.

Specific gravity, and self discharge are not very helpful and the latter varies with battery type, and the former obviously impossible with a sealed battery.

Ian

 

[david_bagshaw]

Battery made in 2005, so 9 years old, it has had a good life, and think whatever capacity it now has is a bonus.

Like Viv I have had batteries show a good voltage after a weeks resting time, but no capacity to turn over the starter, and then recoverin seconds back to the original voltage

 

[Appleyard]

Battery Tester.

Buy one of these it is cheap and effective and will pay for itself.

http://www.toolstop.co.uk/index.php..._medium=base&gclid=COOG5KbolL0CFUcTwwodUZYAOA

 

[GHA]

Buy one of these it is cheap and effective and will pay for itself.

http://www.toolstop.co.uk/index.php..._medium=base&gclid=COOG5KbolL0CFUcTwwodUZYAOA

??

But it doesn't tell you much about how much capacity your battery has left in it? Maybe OK for a start battery.

Even a discharge test isn't completely accurate
http://batteryuniversity.com/learn/article/how_to_measure_capacity

 

[cryan]

Buy one of these it is cheap and effective and will pay for itself.

http://www.toolstop.co.uk/index.php..._medium=base&gclid=COOG5KbolL0CFUcTwwodUZYAOA

+1. Every Marine Lecky I've worked with has used something similar to this to test the condition of batteries along with testing the liquid with a hydrometer (traffic light kind are easiest to use-green good, Red bad etc).

 

[sailinglegend420]

Buy one of these it is cheap and effective and will pay for itself.

http://www.toolstop.co.uk/index.php..._medium=base&gclid=COOG5KbolL0CFUcTwwodUZYAOA

These are only designed to test starter batteries. A deep cycle house battery can easily pass the test but will be useless when you put on a small load for a long time. Don't waste your money on any of these "drop testers" - a cheap DIGITAL voltmeter will tell you much more about your batteries capacity. The simple answer is "know your boat" and realise that you are just not getting the time at anchor you used to before the voltage falls too low.

Every "lecky" I've seen uses one of these - but most don't really know what they are doing!!!! When you try and explain to them that they are useless on deep cycle batteries they just don't understand!

 

[vyv_cox]

I have seen it suggested that leisure type batteries should never be drop-tested as their plates are not robust enough to take it, unlike those of starter batteries.