I am trying to figure out the best way to charge a 12v battery that I use to power an electric trolling motor. Our main boat engine's electrical system does not have the capacity to charge the trolling motor battery.Our TC has 180 watts of solar panels, approximately 17 volts, going to a Samlex a PWM controller rated at 30 amps charging two batteries. Right now the TC has two 12 volt batteries, but I can switch in two 6 volt batteries.We do not have an inverter. Our current solar system works well and we have all the capacity we need.We are usually off the grid, boondocking, when using the boat.Naturally we need to charge the battery in the evening or at night.I have thought about getting an inverter to run a battery charger and let it be at that. I have also thought about just rotating the 12 volt trolling motor battery into the camper battery bank and see how that goes, a little inconvenient. Any comments or suggestions?Rick

Don't use the inverter. Connect the battery to your other batteries when you need a charge. I'm sure others might have another idea.

I would make some quick connect cables and swap batteries every day.Anderson connectors would work great. Connector on the boat also.

sounds like you need Solar panels on the boat lol.Maybe a second trolling battery that you could swap out, always having one being charged back at camp via solar, maybe with a 2 position battery switch to target it once your house batteries are charged. Probably would be much easier with a charge port.http://mellomikeadventures.us/2016/07/feature-in-the-spotlight-palominos-battery-charge-station/

with the info given,1. you only have solar when boondocking, so charging must occur during the middle of the day.2. you are using the trolling battery in the boat during the day.Best is to swap two batteries and charge one every day. Either swap one of the TC batteries, or have two trolling batteries.An alternative is to use an inverter and battery charger to charge the trolling battery at night from the two TC batteries. Doeable but inefficient due to 2 power conversions, DC to AC and AC to DC.Another is to connect the trolling battery in parallel with TC batteries at night. They would equalize at about 2/3 of full charge each minus nighttime use. May not be enough for trolling.

use an inverter,plug your battery charger into it and charge the battery.i have a 1000 watt i plug into my winch connector with an anderson,sort of.it's actually a warn quick connect.i've been doing it this way for years.total cost is under 200 bucks.and a couple bucks in gas.

Electric Trolling Motor Battery Charging | Good Sam Community

jimh406
Explorer III
Jul 19, 2016
Don't use the inverter. Connect the battery to your other batteries when you need a charge. I'm sure others might have another idea.
time2roll
Nomad
Jul 19, 2016
I would make some quick connect cables and swap batteries every day.
Anderson connectors would work great. Connector on the boat also.
hedge
Explorer
Jul 19, 2016
sounds like you need Solar panels on the boat lol.

Maybe a second trolling battery that you could swap out, always having one being charged back at camp via solar, maybe with a 2 position battery switch to target it once your house batteries are charged. Probably would be much easier with a charge port.

http://mellomikeadventures.us/2016/07/feature-in-the-spotlight-palominos-battery-charge-station/
RickW
Explorer III
Jul 19, 2016
with the info given,

1. you only have solar when boondocking, so charging must occur during the middle of the day.

2. you are using the trolling battery in the boat during the day.

Best is to swap two batteries and charge one every day. Either swap one of the TC batteries, or have two trolling batteries.

An alternative is to use an inverter and battery charger to charge the trolling battery at night from the two TC batteries. Doeable but inefficient due to 2 power conversions, DC to AC and AC to DC.

Another is to connect the trolling battery in parallel with TC batteries at night. They would equalize at about 2/3 of full charge each minus nighttime use. May not be enough for trolling.
bcbouy
Explorer
Jul 20, 2016
use an inverter,plug your battery charger into it and charge the battery.i have a 1000 watt i plug into my winch connector with an anderson,sort of.it's actually a warn quick connect.i've been doing it this way for years.total cost is under 200 bucks.and a couple bucks in gas.
Bob__B
Explorer
Jul 20, 2016
Maybe a small quiet generator to sit by the boat to charge the batteries.
mkirsch
Nomad II
Jul 20, 2016
Look to the world of radio-controlled airplanes for the solution!

Something like this, for example:
http://www.hobbyking.com/hobbyking/store/__64345__Turnigy_Accucel_6_80W_10A_Balancer_Charger_LiHV_Capable.html

It is 12V powered and capable of charging a 12V lead acid battery at up to 10Amps.

It is much more efficient than the inverter method.
EricCO
Explorer II
Jul 21, 2016
Another option would be to put a battery isolator in your boat: https://en.wikipedia.org/wiki/Battery_isolator

When your cranking battery is fully charged by the motor's alternator, it will automatically start dumping extra current into your trolling motor battery.

Using the trolling motor won't drain the cranking battery with the isolator between them.
TxGearhead
Explorer II
Jul 21, 2016
^^^This. Some hard core fishermen do this to keep their troll motor batteries up.
mkirsch
Nomad II
Jul 22, 2016
Per the OP:

Our main boat engine's electrical system does not have the capacity to charge the trolling motor battery.

Take a look at RC Airplane chargers like I recommended above. There are a lot of them out there these days that can do lead acid batteries.