View Full Version : Charging 2 batteries with a 2 bank charger

07-03-2011, 10:15 PM
So I am trying to get my electrical system totally up and running on the trailer instead of just my ghetto fab "get 'er done" that has somewhat worked for the past few years.

So I have two marine batteries on my camping trailer. I recently installed (but haven't hooked up yet) a 2 bank battery charger. My questions are simple I hope...

I will obviously hook up each battery seperately to the charger... one battery per bank. However, I was wondering if I connect the batteries together in parallel (+ to + and - to -) will that have an adverse effect on the charger somehow?

I have been reading about isolation switches... that seems to be the ticket as I think it will allow me to charge each battery seperately, but still be able to use both of them at once when wired in Parallel? I am assuming the parallel connection happens through the switch?

Here is where my system is now:

2 batteries (not connected to one another)

2 bank charger with a pos and neg for each battery.

I want to run the batteries in Parallel to get all the amp/hours out of them.

Here is the isolating switch I am hoping to use, it allows the use of Battery 1, 2 or both at the same time and is rated for 300 amps.


I am just good enough with this to burn the trailer to the ground. Thanks in advance-:thumb:

07-03-2011, 11:32 PM

I have two batteries hooked up with a Marine switch. When It is sitting in my garage always on power, they are joined in parallel. When I am out camping, I use them one at a time. I have a voltage monitor I plu into let me know when I need to switch. That also provide me buffer to know I need to charge them. The buffer is about 2.5 days on a single battery


I used this battery charger from AT.
It's only 10 amp and I could have gotten the bigger one with dual outputs, but I figured I keep it plugged in while in my garage, so it's fully charged when I leave. I get 5-7 days with a fully charged setup. I also have a generator if I need to top up on the trail.

07-04-2011, 12:17 AM
Thats cool Romer, thanks... I have been looking at those switches and reading up a bit. using them one at a time is starting to make a lot of sense. I am just running some LED's and my fridge.

07-04-2011, 08:35 AM
I found Marine shops have the best parts for doing these setups. I go to westernmarine down south, sure there is something up north for you. I did like the AT charger better then what I found at the marine store

I'm running a fridge, some lights, a propane heater and a few small things like a phone charger and ipod

07-04-2011, 08:59 AM
I have a Guest 2 Bank Charger, and all the wire/connections are ready to roll. I just needed this last piece of the puzzle. It makes sense to run each battery seperate, I will still get the same number of amp hours out of them. What meter are you using to measure your voltage?

Thanks bud-

07-04-2011, 09:36 AM
I know some have a meter wired right in so they can monitor, those still take some volatge, no matter how small.

I have one I plug in to check it


I know others have wired on in like this


07-05-2011, 09:46 AM
Thanks Ken, my switch and monitor are on their way. :thumb:

07-07-2011, 09:22 PM
Romer, how are you grounding your batteries? Are you running to the frame somewhere or what? Thanks!

07-07-2011, 10:54 PM
Romer, how are you grounding your batteries? Are you running to the frame somewhere or what? Thanks!

Yes, they are tied to the frame

07-08-2011, 09:02 AM
Thanks Romer, you have been a big help. I appreciate it!

I should be fully wired by the end of the weekend, except for my water pump.

I got a mess of LED light strips to wire up in the RTT, and under the trailer lid and I am going to hard wire them into the fuse/switch block and be up and running after that.

07-20-2011, 12:10 PM
Thanks for all your help Romer. I am finally getting there. I just have to make up 4 new battery cables to run to the switch and to the ground. Then I need to install a ground terminal block and I should be good to go to wire up my accessories... LED lights, water pump, 12v outlets, and RTT lights. Should be wrapped up by the end of the weekend.

Here is where it sits now.

I have shore power coming in on the drivers side, it pumps power to the 2 bank charger (5amps more of a trickle than anything), that goes to each battery, batteries are grounded and the hot wires are run to the battery isolator switch 1,2, OFF or BOTH, accessory power runs to the switch/fuse panel and my accessories come off of the fuse panel inside to the part needing power.

I still need to build the cables for the batteries and install a 12v digital meter that lets me know where the charge of each battery is at. I am going to install that on the top of the switch/fuse box on the left.

Mucho gracias Romer for helping me on this one. :Thumb:

After this its time to finish up the plumbing and start the kitchen. :p:

07-20-2011, 12:17 PM
Here are a few more detail shots of the system... if anyone sees anything that should be changed, speak up now! :D

Battery Isolator switch from Blue Sea:

Blue Sea fuse/switch panel with carling illuminated switches:

Added some grommets to run wires throug the bottom:

Bought some heavy duty battery terminal covers:

12v power daisy chained with 10ga wire, to run RTT lights, or a DVD player:

Shore power and Charger:


07-20-2011, 01:42 PM
Here are a few more detail shots of the system... if anyone sees anything that should be changed, speak up now! :D


The owner.
That is so freaking clean it HURTS!

07-20-2011, 02:26 PM

The owner.
That is so freaking clean it HURTS!

Right :rolleyes:... because the Chilli is so sloppy and slapped together :thumb: