Finding the batteries in my bank to keep

[btrayfors]

"Doesnt always work that way though. Just got over a starting debacle. Battery read 12.8 cold after sitting overnite with no charge. Then it failed the load test miserably. That battery was the reason i bought the load tester to isolate the problem."

Exactly!

I don't know how many times we have to say it before it will finally sink in:

Resting battery voltage or "holding a voltage overnite" means almost NOTHING about the health of your battery.

Example: You have a battery which has been disconnected and sitting for a week and which measures 12.6 or even 12.7 volts. That means it's a good battery, right?

W R O N G !

Fact is, you have no idea whatsoever about the remaining capacity of that battery, i.e., its ability to store and deliver energy.

Whether or not it's worth keeping or fooling with depends on a number of factors, but you're first got to determine how much capacity is left. You can only do this with either a prolonged load test (preferably at C/20 load level) or by using a sophisticated (and expensive) capacity tester.

Bill

[Cheechako]

Resting battery voltage or "holding a voltage overnite" means almost NOTHING about the health of your battery.
Actually it does mean something, but yes is not as conclusive as a load test. If after resting over night and it's down in voltage.. like 11 volts or something etc... then you know it's bad. If it's not down, you are right, it may not be very good also. However if it's down overnight and the rest of the batteries are up, then you can bet it's the one that's bringing the rest down. Which was the original question I believe.

[Warby12]

Hi all. So I left the batteries fully charged and disconnected and watched for any crazy discharging. All good, they stayed very very close to each other ( I won't quote exact voltages because I have forgotten them and also noticed one of my multimeters is reading almost a full volt below the other ( now binned)) So two weeks down the track, uncharged and unloaded, they are still very very close to each other in voltage, I have run a very rough but practical test on them by connecting the fridge and seeing how they cope for 24 hours. Fridge was happy ( beer cold ) after 20 hours and voltage down to about 12.4 evenly across the five batteries. I'm very happy as this means at least they are good for weekending and this was with no solar connected.

I have them back on my ctek charger with no load, so I am wondering why with the charger running them at 13.75vlt float, the charger is till warm? Surely it would only take a trickle to keep this voltage or is it simply that 500 amp hours of batteries has a lot of resistance to deal with?

I'm sorry if this is not a very interesting thread but I am curious about the charging dynamics

[sparrowhawk1]

Sounds like you had the batteries connected together when you ran the fridge. As stated earlier you need to put a load on them individually to find out their true capacity.

[sailorboy1]

Originally Posted by forsailbyowner

I bought a battery load tester at harbor freight for $20. It will give you a reading in 15 seconds and the relative load capacity of the batteries will be easy to spot.

Will that little tester really be able to put enough load on a large boat house bank to be meaningful?

[sparrowhawk1]

Originally Posted by sailorboy1

Will that little tester really be able to put enough load on a large boat house bank to be meaningful?

? You don't test the whole bank you test one battery at a time

[sailorboy1]

Originally Posted by sparrowhawk1

? You don't test the whole bank you test one battery at a time

That's still a big battery, for mine that would be either a 12V bank of 230AH rating or a 6V 230AH battery.

I like the "idea" of the $20 Harbor Freight tester, but am finding it hard to believe that this is going to be useful. I don't need another tool to tell me battery lies.

[sparrowhawk1]

I don't know the exact specs but if it can't do 230ah battery its junk. It should have the amp draw specified.

[sailorboy1]

Originally Posted by sparrowhawk1

I don't know the exact specs but if it can't do 230ah battery its junk. It should have the amp draw specified.

maybe why the question was addressed to the person who said they had the tester you think

[sparrowhawk1]

Originally Posted by sailorboy1

maybe why the question was addressed to the person who said they had the tester you think

Point taken. I got drawn into it because you said battery bank not battery

[a64pilot]

I've used the battery testers that have a high resistance winding in them that essentially puts about 100 amp load on the battery and you watch the voltage with the load on, a "bad' batteries voltage will drop quite substantially with a high amp load on it. Not saying it will test all parameters of a battery, but I've never seen a good battery fail the load test.
Cheap, easy and simple test, why not test?
In the US pretty much all the parts houses will do the test for free, and many will "loan" tools, they require a large deposit to ensure the tool comes back though, but the deposit is refunded so the tool use is free.

[a64pilot]

Either way, the point is mute, his bank has enough amps for what he needs it to do, so until he leaves why buy new batteries.
I'm only doing the weekend thing myself, currently my bank is comprised of four year old Walmart batteries which I will leave alone until I leave full time and need a real battery bank, I'll nurse the Walmart batteries until they fail, who knows what will be available in a couple of years?

[Cheechako]

It sounds like your batteries are fine. A charger creates heat by the physics of how it works. Personally I wouldn't leave it hooked up all the time. Put it on now and then.

[Warby12]

Thanks guys yes I should probably have changed the name of the thread to "should I chuck out All of my batteries" by now. Agreed I should have tested them individually but I have bigger fish to fry. I need a holding tank so that I can actually untie from the marina and day sail batteries have passed the crucial weekend cold drink test so we are friends. I will disconnect them from the charger now and reconnect the solar with new cables and leave them be