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Old 25-06-2014, 05:18   #1
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Keeping the dinghy battery charged

I've never had an electric-start outboard on our dinghy before, and we only use the dinghy occasionally...

So I'm looking for ideas on how folks keep the battery from self-discharging.

I know the outboard's alternator will re-juice the battery to the extent possible when we're underway, but the dinghy sometimes sits idle for a month or so at a time...

Thoughts? Or is it a non-problem? Or...?

-Chris
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Old 25-06-2014, 05:42   #2
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Re: Keeping the dinghy battery charged

It's a non-problem under most circumstances. If you usually motor about 5 or 10 minutes each time you start the engine then you should be OK. Self-discharge during the occasional month long layup won't be that much.

I have a yamaha 20 and a small start battery that also powers a bilge pump to deal with rain, and have never had the battery run down. Have had this setup 3 years it's a 12 foot RIB.
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Old 25-06-2014, 05:47   #3
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Re: Keeping the dinghy battery charged

Until pretty recently all outboards, even the big ones only trickle charged a battery, they didn't have alternators and voltage regulators.
First find out what the little Zuk has, I'd bet it simply trickle charges at a set rate regardless of battery charge like all outboards used to do, so charging up a partially depleted battery will likely never happen unless you run your dink for hours at a time.

I'd go for a small, cheap solar panel. Even a tiny one should keep a small battery charged, and you only need and want a tiny amount of current anyway
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Old 25-06-2014, 05:48   #4
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Re: Keeping the dinghy battery charged

I must type slow, never saw sailfast's post until after mine.
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Old 25-06-2014, 08:37   #5
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Re: Keeping the dinghy battery charged

The Suzuki alternator is 12A @ 14V. A month or two should not be a problem for the battery. For longer times, just take it home and put it on a charger every month or so.

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Old 25-06-2014, 09:04   #6
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Re: Keeping the dinghy battery charged

Thanks, guys, sounds like a non-problem... and yep, we can charge at home if it comes to that.

-Chris
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Old 25-06-2014, 10:49   #7
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Re: Keeping the dinghy battery charged

Get a small solar charger to keep the battery up. You can get cheap ones on ebay that overseas car companies use to keep batteries charged in cars sitting on the dock, they just plug into a a cigarette lighter. They do not put out enough to cook the bat so do not need a regulator but will keep the battery topped up.
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Old 25-06-2014, 11:28   #8
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Re: Keeping the dinghy battery charged

12 amps is enough for some lights, a bilge pump and maybe even some tunes
My little C-140 airplane came with a 15 amp fuse for it's generator
funny how things change
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Old 25-06-2014, 15:35   #9
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Re: Keeping the dinghy battery charged

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Originally Posted by ranger42c View Post
I've never had an electric-start outboard on our dinghy before, and we only use the dinghy occasionally...

So I'm looking for ideas on how folks keep the battery from self-discharging.

I know the outboard's alternator will re-juice the battery to the extent possible when we're underway, but the dinghy sometimes sits idle for a month or so at a time...

Thoughts? Or is it a non-problem? Or...?

-Chris
Non-problem, especially if you have a sealed battery. A flooded battery will loose 15% capacity per month, so it becomes a problem after a few months.
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Old 26-06-2014, 05:35   #10
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Re: Keeping the dinghy battery charged

I'm definitely OK with the "non-problem" opinion!

That's also supported by my experience with our sealed lead acid tractor battery during winter months... although that's recharged by a larger alternator, and it gets a work-out if we have big snow and I have to plow for several hours on end.

One of these days, then, I'll stop in the battery store down the street and get 'er done.

-Chris
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Old 26-06-2014, 10:46   #11
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Re: Keeping the dinghy battery charged

Also, how big is the engine and do you have a backup pull start.

The 25hp Merc on our big boat has both electric and pull start, so if the battery ever dies, it's simple to just pull start.

Used to have a pull start 40hp that wasn't bad to turn over.

The only issue with the battery is what parasitic draws do you have. If there is a bilge pump that runs periodically, that could kill the battery much quicker and the small trickle charger isn't likely to solve the issue.
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Old 26-06-2014, 11:34   #12
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Keeping the dinghy battery charged

We use a Sterling 12v to 12v isolation transformer to keep our dinghy battery charged from the house banks on Indigo.
Paul
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Old 26-06-2014, 12:39   #13
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Re: Keeping the dinghy battery charged

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Originally Posted by valhalla360 View Post

Also, how big is the engine and do you have a backup pull start.

The only issue with the battery is what parasitic draws do you have. If there is a bilge pump that runs periodically, that could kill the battery much quicker and the small trickle charger isn't likely to solve the issue.

Only 15-hp, with pull-start... and I've been using that; it's easy enough.

No additional loads.

-Chris
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Old 26-06-2014, 13:29   #14
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Re: Keeping the dinghy battery charged

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Only 15-hp, with pull-start... and I've been using that; it's easy enough.

No additional loads.

-Chris
With no other loads and easy pull start as a back up, I wouldn't worry about it.

Only thing you might consider is a disconnect switch on the battery to guarantee no parasitic loads.
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Old 27-06-2014, 06:51   #15
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Re: Keeping the dinghy battery charged

Yep, fair enough, Especially if I ever add anything else electric to the boat...

I do like the "don't worry about it" solution.

-Chris
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