charging batteries

[pieman22]

I have 2 stowaway 12v batteries i purchased from Academy a couple months ago. I wired them in parralel to run my trolling motor. What is the best way to charge them? I have been connecting my charger to the pos post on one battery and the neg post on the other. I have been charging at 2amps for over 24 hrs but they do not seem to be taking a solid charge(as my trolling motor thrust is very low). Im going to run them on 10amps tonight for a 6 hrs and see how they do. Any suggestions?

 

[Barnacle_Bill]

Re: charging batteries

Charging 2 batteries in parallel at 2 amps would take a very long time to recharge. Get yourself an on-board charger. Plug it in as soon as you get home then forget it until you are ready to go again. That way you will always have a fully charged battery.

 

[metriccrescentwrench]

Re: charging batteries

Do you know the amp-hour capacity of these batteries? With that knowledge you can get a rough idea of how long it would take to fully charge them at any given charging current. For instance, if they're 50 amp-hours each (times 2 gives a total capacity of 100 amp-hours) and are at 50 percent charge you'd have to add 50 amp-hours to them to get up to full charge (actually somewhat more than that because no battery is 100% efficient). At a 2 amp charge rate you're talking in excess of 25 hours for these made-up batteries.

Oh, just out of curiosity, what does battery charging have to do with Johnson/Evinrude repair and maintenance?

 

[Haffiman]

Re: charging batteries

Roughly old type lead-acid batteries should be charged with around 10% of their total capacity. (100 Amp/hours - 10 Amp charge) Going much higher, you risk boiling them out, and too much lower you will never get them charged.
A 2Amp charger may be ok for a motorbike battery, probably not for your application. The charge rate given is normally at 12 Volts, but as battery needs around 13,8 - 14,2 charge voltage to be fully charged, your charger will not manage.

 

[sschefer]

Re: charging batteries

I bought a West Marine charger this year in lieu of going with an onboard like I've always done. I run it at 10 amps until I get up to 13.5v then drop it back to 2amps and finish it off. It takes about 6 hours to charge a nearly drained (left the darn Lowrance on all day and night) group 24 combo battery. On my last boat with 2 group 27 deeps and a group 24 starting It would take the better part of 12 hours to bring them back to 100% from a 60% charge with a ProMariner tripple 20amp onboard charger. Just saying this for a practical reference rather than a math quiz.