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I have a landscape trailer with a break-away battery that looks like it is currently getting charged from my 7 pin plug. I've recently added a 12v deep-cycle battery to power an electric jack on the trailer. I'm having trouble figuring out how to also charge this additional 12v deep-cycle battery. Do I hook them both in parallel and will that charge both? With the batteries being different sizes I wasn't sure if that was problematic or not. Appreciate any help.
 

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You can hook them in parallel although I'd suggest you look into a batter isolator. They allows you to charge both batteries from the same source but keeps them electrically isolated otherwise so that if one goes bad, it doesn't kill the other. You don't need a monster isolator. The charging pin on those 7-pin trailer plugs are usually a max of 20 amps. It isn't like you'd have several hundred amps like you would for multiple starting batteries in a truck.
 

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I have a landscape trailer with a break-away battery that looks like it is currently getting charged from my 7 pin plug. I've recently added a 12v deep-cycle battery to power an electric jack on the trailer. I'm having trouble figuring out how to also charge this additional 12v deep-cycle battery. Do I hook them both in parallel and will that charge both? With the batteries being different sizes I wasn't sure if that was problematic or not. Appreciate any help.
I've been doing this for decades on my bee trailers without issues. My bee trailers have an electric winch for lifting hives. If your truck is a Ford 2006 or newer with trailer towing package all lines to trailers are protected. The mistake many make is they try using the frame for the - side and that will cause issues. Make sure you have both a - and a + fairly heavy wire to your battery. I use #12 or 10 copper for both and color code them so there can be no mistakes.


https://www.countrytrailer.com/uploads/7wayplug.pdf
 

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I have a landscape trailer with a break-away battery that looks like it is currently getting charged from my 7 pin plug. I've recently added a 12v deep-cycle battery to power an electric jack on the trailer. I'm having trouble figuring out how to also charge this additional 12v deep-cycle battery. Do I hook them both in parallel and will that charge both? With the batteries being different sizes I wasn't sure if that was problematic or not. Appreciate any help.
When you hook up the battery make shore you are getting the correct voltage at the battery in the trailer. You have voltage drop between the alternator and the trailer, and smart alternators can also be a problem. Could someone correct me if I am wrong, you should get around 14 volts at the trailer and a full battery is about 13.5 volts
Regards John
 

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Does your trailer sit a lot? How much do you tow it? If it sits a lot, and you don't tow it long distances, the truck isn't going to have much time to fully charge the battery. I bought a solar panel trickle charger for our dump trailer, and keep that on it. It has worked great.
 

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Discussion Starter #7
Thanks everyone for the comments. I'll do some more research into those options. To answer some other questions that came up, my trailer gets used maybe twice a week. I use it for hauling equipment to some property that is about 10 minutes from my current home. Sometimes I'll use it to haul brush on longer runs of an hour round-trip. My truck is a 2015 Silverado.

Currently about once a month I put a battery charger on it while its parked in my driveway.
 

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Why not just ditch the smaller breakaway battery? The deep cycle will handle both beautifully and maybe you could repurpose the breakaway battery.
I've never thought of that travel trailers don't have the little battery so it must be ok. My experiance with the little guys is that they break off because of the weak support they have then i duct tape them back on and forget about them
 

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When you hook up the battery make shore you are getting the correct voltage at the battery in the trailer. You have voltage drop between the alternator and the trailer, and smart alternators can also be a problem. Could someone correct me if I am wrong, you should get around 14 volts at the trailer and a full battery is about 13.5 volts
Regards John
My deep cycle marine batteries usually read about 12.75 fully cvharge and with wires disconnected. Supply voltage runs about 13.75 with the motor running. 12.,75 is after the battery has rested and had a change to stabilize. I used a yearly lab calibrated fluke digital multimeter.
 
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