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Portable Batt. Charger Recommendations?

Hi All,

Can anyone recommend a good, fast, portable battery charger? My boat was pulled last weekend by the marina and I'm heading up there tomorrow to finish putting her to bed. The batteries should already be topped off, but I'm looking to prepare myself for having to "top off" the batteries. I mean, what if I go up to the boat, which has been off of shorepower (and all DC switches on the panel turned off) for about a week, and I test the batteries and they show 75% full? My thought is I would plug in a car-style 12V battery charger to top off the batteries. I have two 4Ds for house, and one Group 31 for a starting battery. So I would charge each of them individually.

The boat is more than two hours away though, and I'm thinking I'll be spending probably about 4 hours up there doing what I need to do. Is that even enough time for a car-style battery charger to top off the batteries?

Another alternative is that I WOULD be able to simply plug in my boat to "shore power" using an adapter on a conventional extension cord plugged into a normal 110v wall outlet. Would that charge the batteries to full in the small amount of time?

Thanks for any advice!

Last edited by bshock; 10-10-2014 at 09:27 AM.
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post #2 of 6 Old 10-10-2014
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Re: Portable Batt. Charger Recommendations?

It's only been a week? I sure wouldn't worry about them being discharged unless you left something on (which you said you didn't).

And you are going to charge them individually? So less than an hour on each battery, or each bank? What is the amperage of your onboard charger? Why do you think a portable charger would be more effective than using the shore power? What are your plans for keeping the batteries charged for the winter? Or are you hoping to charge them to full and leave them for the winter?
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post #3 of 6 Old 10-10-2014
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Re: Portable Batt. Charger Recommendations?

Batteries only looks about 1 to 3% charge per month sitting unused so if they were fully charged when boat was pulled then you should not need to do anything till recommissioning time then top off
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Re: Portable Batt. Charger Recommendations?

thanks guys, I don't know the amperage of my onboard battery charger, but yeah, it's only been a week. So maybe there's nothing to worry about.
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Re: Portable Batt. Charger Recommendations?

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Originally Posted by bshock View Post
Hi All,

Can anyone recommend a good, fast, portable battery charger? My boat was pulled last weekend by the marina and I'm heading up there tomorrow to finish putting her to bed. The batteries should already be topped off, but I'm looking to prepare myself for having to "top off" the batteries. I mean, what if I go up to the boat, which has been off of shorepower (and all DC switches on the panel turned off) for about a week, and I test the batteries and they show 75% full? My thought is I would plug in a car-style 12V battery charger to top off the batteries. I have two 4Ds for house, and one Group 31 for a starting battery. So I would charge each of them individually.

The boat is more than two hours away though, and I'm thinking I'll be spending probably about 4 hours up there doing what I need to do. Is that even enough time for a car-style battery charger to top off the batteries?

Another alternative is that I WOULD be able to simply plug in my boat to "shore power" using an adapter on a conventional extension cord plugged into a normal 110v wall outlet. Would that charge the batteries to full in the small amount of time?

Thanks for any advice!
You can't fully and adequately charge three flooded LA batteries at 75% SOC with ANY battery charger in 4 hours. That simply defies the limits of the chemistry...

In order to fully charge batteries, healthy enough for winter storage, the charge current should drop to under 1% of the banks 20 hour Ah capacity and this at 14.4V or better.

You are even better to wait until .5% acceptance occurs but 1% is will do. Ideally any battery than can be equalized before winter should be. Even AGM's exceed 8 hours to get to this point due to what is called CAR or the charge acceptance rate......

On the other hand I doubt your batteries will be at 75% SOC if they had previously been on charge at a dock. So any charge will help. Be certain to charge your batteries as full as you can then 100% disconnect the batteries from the vessel... Do not leave them connected regardless of switch position.....

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Last edited by Maine Sail; 10-10-2014 at 02:55 PM.
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Re: Portable Batt. Charger Recommendations?

Thanks Maine Sail, that's what I was wondering about.
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