# Charging Trolling Motor Battery



## Fresca (Feb 3, 2017)

There is not a way to tie in trolling motor battery to engine battery on my skiff for charging due to boat design. Can I hook a battery charger into accessory cigarette lighter to trolling motor battery to charge while running boat?


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## Vertigo (Jun 3, 2012)

Not recommended, but you could do it, and if the charge on your engine battery is greater than the charge on your TM battery, the TM battery would gain charge. The TM battery and motor battery would be running in parallel. The down side is that the batteries will tend to equalize charge and if the TM battery goes flat it could drag your motor battery down with it. There's also the question of the amount of current that may be going thru your accessory socket wiring. Under some circumstances it could be enough to cause damage. You might also find that hooking the TM battery into your house electrical system could result in interference with your electronics. The best bet is to just get a charger for the TM battery and plug it in while the boat is on the trailer at home.


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## jfboothe (Dec 19, 2012)

I have a MinnKota DC alternator On-Board charger and it really works great. Anytime the engine is running, the dedicated deep cycle trolling motor battery is charging. The only time I hook up a stand alone charger is if the boat is sitting for an extended period of time. I have gone on a week long trip and used the trolling motor 4-5 hours per day with no problem. 

http://www.minnkotamotors.com/Battery-Chargers/On-Board-Chargers/DC-Alternator-Chargers/


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## Megalops (Oct 23, 2011)

Wow, a competitor to the Stealth One charger. Thanks for posting link.


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## Fresca (Feb 3, 2017)

So even if I plugged an On-Board charger into the boat accessory socket to TM battery it would end up equalizing both batteries? On-Board charger would not charge TM battery and running boat would not charge engine battery?


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## jfboothe (Dec 19, 2012)

Fresca said:


> So even if I plugged an On-Board charger into the boat accessory socket to TM battery it would end up equalizing both batteries? On-Board charger would not charge TM battery and running boat would not charge engine battery?


Do you have a 12volt battery charger that plugs in to a 12volt accessory socket? I haven't seen one like that before but I really never looked.


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## Smackdaddy53 (Dec 31, 2012)

jfboothe said:


> I have a MinnKota DC alternator On-Board charger and it really works great. Anytime the engine is running, the dedicated deep cycle trolling motor battery is charging. The only time I hook up a stand alone charger is if the boat is sitting for an extended period of time. I have gone on a week long trip and used the trolling motor 4-5 hours per day with no problem.
> 
> http://www.minnkotamotors.com/Battery-Chargers/On-Board-Chargers/DC-Alternator-Chargers/


I like!!!


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## Fresca (Feb 3, 2017)

I don't. Just wondering. What about Battery Tender and its cigarette lighter adapter?


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## jfboothe (Dec 19, 2012)

I could be wrong but I believe the battery tender is designed to be plugged in to a 120v AC outlet and the 12V accessory plug is to charge the battery _through _the a hot 12V socket rather than having to access the battery with clips. The quick connect on the end is designed to attach to the quick connect on the battery tender.


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## MariettaMike (Jun 14, 2012)

Megalops said:


> Wow, a competitor to the Stealth One charger. Thanks for posting link.


NOT really. Its a relay marketed as a charger.

https://www.westmarine.com/buy/blue...37D-19A2DA1BEC68&cm_sp=Onsite-Recs-_-MB-_-PDP

Stealth 1 is an actual battery charger/conditioner/maintainer that steps up voltage from 12V to 24V or 36V depending on model/setting. That Alternator product is permanent 1 bank, 2 bank, 3 bank outputs at 12V each.

For full charging/conditioning/maintenance you still have to install another on-board charger in parallel with the Alternator. While the Stealth system you just hook any AC charger/maintainer to your engine battery and forget it.

The limiting factor for any technology (including jumper cables) is the engine alternator output. Most engines under 70 hp are under 20A, and you don't get enough charge out of short runs to justify having it.


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## MariettaMike (Jun 14, 2012)

Fresca said:


> There is not a way to tie in trolling motor battery to engine battery on my skiff for charging due to boat design. Can I hook a battery charger into accessory cigarette lighter to trolling motor battery to charge while running boat?


You could, but I wouldn't recommend it because the potential for high current (amperage) would just blow fuses or melt insulation and catch your boat on fire.

Use jumper cables OR just swap batteries between runs.


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## Steve_Mevers (Feb 8, 2013)

If you have room to run two battery cables from your house batteries to your trolling motor batteries, you can install an islolator type device designed to switch your charging current to your trolling motor batteries once the house batteries are fully charged. I have been using this system for three years and I rarely charge my batteries using my AC charger anymore. Just returned from 5 days of fishing in Flamingo and batteries are still fully charged. If you want the exact make and model of the isloator I used I will look in my boat.


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## jfboothe (Dec 19, 2012)

MariettaMike said:


> NOT really. Its a relay marketed as a charger.
> 
> The limiting factor for any technology (including jumper cables) is the engine alternator output. Most engines under 70 hp are under 20A, and you don't get enough charge out of short runs to justify having it.


Can't disagree to a certain extent. You already have 12 volts there so really all that has to happen is routing the 12 volts to the battery you want to charge at the right time. I have an ETEC and plenty of amps for charging. I did seriously considering just putting two dual purpose batteries in for both starting and the trolling motor since I have a pull start too. If I kill the batteries running the trolling motor, then I won't be stuck. But I think I paid about $75 for the single bank MK 1 DC and it was easy. And it does work and work very well.


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## MariettaMike (Jun 14, 2012)

jfboothe said:


> ...But I think I paid about $75 for the single bank MK 1 DC and it was easy. And it does work and work very well.


The price is right for what it does, however the 25 amp minimum for the 2 bank 24V model is a deal killer for many outboards including etecs.


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## jfboothe (Dec 19, 2012)

"Supposedly" my little 25hp ETEC puts out 56 amps with 15 amps to drive the motor electronics, but I have no idea what rpm that happens at. Nice thing about a small light skiff is I only really need a 12v 55lb thrust TM and I don't have to have a 2 bank 24v system especially with the single battery being charged every time I run the outboard.


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## Smackdaddy53 (Dec 31, 2012)

The answer is this:
https://www.bluesea.com/resources/1366
I have one on my other boat.


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## Steve_Mevers (Feb 8, 2013)

This is the islolator I have on my boat, it keeps my trolling motor batteries charged all the time, I have used it for three years on a 24v system. They also make one that will charge your batteries from your outboard and also from your truck while driving, I have the model that works only off the outboard and it meets my needs. http://www.fishingminnesota.com/stay-n-charge/


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