Does anyone know about 12 volt batteries?

[Dutch]

My boat was gone for 2 1/2 months and my 2 year old batteries were in storage at the factory.  When I got it back my 36 volt Ulterra was not as powerful as usual.  I had Scott check them and he found one belly up.  He replaced it ( he only had one on hand) and I went back to the lake finding a strong trolling motor again.

I have 2 more ordered so he can replace the ones left.  What I am trying to find out is how good the other two are.  If they are only good enough for core swaps so be it.  But if they are still functional, I want to trade them to someone who has some cores to swap.

Do any of you have a definitive way to check them out?

[fishinwrench]

You can test them with a digital voltmeter.    

Charge them individually to a stable 12.70+ then let the battery sit overnight, if you lose more than .30v overnight.... it's time to replace.  

Since  you have one fresh one, you can also compare the loaded voltage drop of each, individually, when the TM button is activated (it doesn't have to be in the water).   Again, a difference of .30- indicates the weakest battery regardless of the state of charge.

[retired chem teacher]

here is how I check mine---first fully charge the battery- (2) -do a load test with a load tester.  (I bought mine for around $20 at Harbor freight)   (3) if the battery is not a sealed battery you can use a hydrometer to check specifc gravity of cells   If there is large difference in the 6 cells there is good chance the low reading cells are bad.  

1.26 – 1.28

100% Charge

Some hydrometers use colored balls like antifreeze testers that make life easier

I usually rely on load tester as I am not dealing with battery acid with a hydrometer.

[Dutch]

Should have mentioned they are agms.  I unplugged them overnight and checked them with a volt meter.  They tested 13.24 on the new one and 13.06 and 13.07 on the old ones.  

[MrGiggles]

For a deep cycle you can do like Wrench says. 

I personally don't think those digital testers are worth a crap. Old school carbon pile testers are the way to go, but they aren't testing for reserve capacity like you want in a deep cycle.

[aarchdale@coresleep.com]

Ever since ive owned a boat for about 9 years, i have done a lot of trolling for walleye using the troller. I always noticed batteries would work great for about 6 months and then they wouldn't last near as long. Take them and get them tested and they would test good. But during a normal day fishing bass, crappie or whatever just not pulling cranks the whole time you would never notice a deficit.  My last set of Duracells would only last about 2 hours of constant trolling before they were done. They still tested good.  Got a set of Lithiums, hopefully the hype is worth it.  I trolled hard for close to 6 hours on them the first trip out and they were great.   

[grizwilson]

Dutch, I have a much older AGM would love to trade, sure I have a core or two if we can make a deal.  Those sound better than mine.

[Dutch]

Griz I can get replacements on Thursday.  We need to do the exchange Wednesday late in the afternoon.

 

 I will pm you my phone number in case you don’t have it.