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Charging trolling motor battery while boondocking

cbird02
Explorer
Explorer
I have a two-battery bank that is charged by a solar panel via the onboard Renogy controller. I have a trolling motor that is run by a 12v deep cycle 100ah battery. I have 2 similar deep cycle batteries in the bank. When I am off grid, I want to charge my trolling battery from the RV without using an inverter to plug in my normal AC-DC charger. What is the most efficient way to do this? Can I just hook up my trolling battery in parallel with the other two and the whole bank will then be charging? What if I want to make sure that my trolling motor is fully charged even if my coach batteries are not? Thx

Craig
26 REPLIES 26

cbird02
Explorer
Explorer
CA Traveler wrote:
A common marine switch is 1 2 both off for the two banks.

A on/off switch between CC and house battery turns them on/off for charging. External + wire connected to CC and disconnect wires from battery when not needed.


What about this Marine Battery Isolator/Changeover Switch - 4 Positions - 100A Cont.

CA_Traveler
Explorer III
Explorer III
A common marine switch is 1 2 both off for the two banks.

A on/off switch between CC and house battery turns them on/off for charging. External + wire connected to CC and disconnect wires from battery when not needed.
2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob

cbird02
Explorer
Explorer
CA Traveler wrote:
cbird02 wrote:
I have a two-battery bank that is charged by a solar panel via the onboard Renogy controller. I have a trolling motor that is run by a 12v deep cycle 100ah battery. I have 2 similar deep cycle batteries in the bank. When I am off grid, I want to charge my trolling battery from the RV without using an inverter to plug in my normal AC-DC charger. What is the most efficient way to do this? Can I just hook up my trolling battery in parallel with the other two and the whole bank will then be charging? Yes What if I want to make sure that my trolling motor is fully charged even if my coach batteries are not? Disconnect the house batteries so all of the charge will be goint to the trolling motor battery. Thx

Craig


I think this is what I am going to do. Anyone know of some sort of switch I can install on the incoming wires from the existing charge controller? I don't want to unhook the wires every time so I am thinking like a switch that changes it from Coach to External battery, then I just uncoil some wires from inside my battery store, hook up the Trolling battery and flip the switch. Just don't know if that exists or what rating it would be. I have (1) 100W solar panel and the controller is rated at 30A.

cbird02
Explorer
Explorer
SJ-Chris wrote:

My boat has a ski tower. I usually take it off when I'm fishing (if there is more than 2 people). But if not, I could easily mount 1-3 panels up there. It would even provide a little bit of shade underneath. That would keep my trolling batteries charged up all day EVEN WHILE USING THEM. So....perhaps you can find a convenient (or creative) way of mounting 100-200 watts of solar on your boat. If you don't have any space on deck or on top of a canopy, maybe you could mount it on an 8' tall pole somewhere to keep it out of the way.

Perhaps this is all just a crazy idea...it's late (lol)

-Chris


This is for an 14' inflatable boat so no room for panels!

SJ-Chris
Explorer II
Explorer II
I have a family fish/ski boat. It has 2 Group 29 batteries (...or maybe they are 27s, I can't remember). It has a plug in the front of the boat for me to plug in my trolling motor (which runs off these two engine batteries). It's never been an issue for me (low batteries). Assuming I zoom too and from the fishing spot on the water, the engine alternator seems to have enough time to keep the batteries sufficiently charged.

Just recently, with my boat sitting for many months in winter storage, I decided I wanted to put a little portable solar on the boat to keep the batteries topped off during the winter. I bought some used 100w panels for $25 each and created a quick and easy portable charging system for my boat (using one 100w panel). (Side note: Has anyone else discovered solar to be a bit addictive??) It got my batteries up to 100% in no time at all (...they weren't low to begin with). Honestly, I find myself keeping the whole system unplugged most of the time because I don't want to just leave the batteries for days/weeks/months with a trickle charge on them when they don't really need it.

My boat has a ski tower. I usually take it off when I'm fishing (if there is more than 2 people). But if not, I could easily mount 1-3 panels up there. It would even provide a little bit of shade underneath. That would keep my trolling batteries charged up all day EVEN WHILE USING THEM. So....perhaps you can find a convenient (or creative) way of mounting 100-200 watts of solar on your boat. If you don't have any space on deck or on top of a canopy, maybe you could mount it on an 8' tall pole somewhere to keep it out of the way.

Perhaps this is all just a crazy idea...it's late (lol)

-Chris
San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs

time2roll
Nomad
Nomad
Charging direct is fine although you can only go out every other day. Or a second trolling battery is needed.

CA_Traveler
Explorer III
Explorer III
A second trolling battery can help - use one while charging the other one.
2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob

Bumpyroad
Explorer
Explorer
CA Traveler wrote:
cbird02 wrote:
I have a two-battery bank that is charged by a solar panel via the onboard Renogy controller. I have a trolling motor that is run by a 12v deep cycle 100ah battery. I have 2 similar deep cycle batteries in the bank. When I am off grid, I want to charge my trolling battery from the RV without using an inverter to plug in my normal AC-DC charger. What is the most efficient way to do this? Can I just hook up my trolling battery in parallel with the other two and the whole bank will then be charging? Yes What if I want to make sure that my trolling motor is fully charged even if my coach batteries are not? Disconnect the house batteries so all of the charge will be goint to the trolling motor battery. Thx

Craig

x2
just charge the TM battery, unless you have a monster of a solar charger it will have trouble keeping a TM battery charged fully.
bumpy

Lwiddis
Explorer II
Explorer II
โ€œWhat if I want to make sure that my trolling motor is fully charged even if my coach batteries are not?โ€

If you have room on the RVโ€™s roof I suggest a separate solar system specifically for the fishing battery.
Winnebago 2101DS TT & 2022 Chevy Silverado 1500 LTZ Z71, WindyNation 300 watt solar-Lossigy 200 AH Lithium battery. Prefer boondocking, USFS, COE, BLM, NPS, TVA, state camps. Bicyclist. 14 yr. Army -11B40 then 11A - (MOS 1542 & 1560) IOBC & IOAC grad

time2roll
Nomad
Nomad
Just realized Renogy mothership is just down the street from my RV storage.
I might have to stop in and check them out. ๐Ÿ™‚

time2roll
Nomad
Nomad
Renogy has the solution with a DC-DC charger:

https://www.renogy.com/12v-dc-to-dc-on-board-battery-charger/

I recommend the 20 amp version for what you are doing.

CA_Traveler
Explorer III
Explorer III
cbird02 wrote:
I have a two-battery bank that is charged by a solar panel via the onboard Renogy controller. I have a trolling motor that is run by a 12v deep cycle 100ah battery. I have 2 similar deep cycle batteries in the bank. When I am off grid, I want to charge my trolling battery from the RV without using an inverter to plug in my normal AC-DC charger. What is the most efficient way to do this? Can I just hook up my trolling battery in parallel with the other two and the whole bank will then be charging? Yes What if I want to make sure that my trolling motor is fully charged even if my coach batteries are not? Disconnect the house batteries so all of the charge will be goint to the trolling motor battery. Thx

Craig
2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob