Separate batteries with remote switch

[johanso]

My Land Cruiser has two starter batteries and I would like to have the ability to separate them. I have the fridge and other things connected to the second battery but since the batteries are connected I risk draining both. Although I'm not willing to make the second battery only a house battery. I want to keep the ability to use both as starter batteries.
Ideally I would like to be able to leave the car with the fridge on for a couple of hours and have it run just on the second battery and then when I'm back have the two batteries working together and getting charged while driving.

At first I was thinking just a simple battery switch but then I could see me forgetting to connect the batteries again and eventually have no power in the second battery.
Then I came across the Blue Sea remote battery switch. As far as I understand I could have a switch on the dash and choose wether the batteries are connected or disconnected.

https://www.bluesea.com/products/7700/ML-RBS_Remote_Battery_Switch_with_Manual_Control_-_12V_DC_500A

Would this product work in my application or should I go with the Blue Sea Add a battery kit containing a battery switch and a charging relay?
https://www.bluesea.com/products/7650/Add-A-Battery_Kit_-_120A

 

[brianjwilson]

Keep it simple and get the blue sea ACR 7622
https://www.bluesea.com/products/76...rging_Relay_with_Manual_Control_-_12V_DC_500A

You can manually connect or disconnect the batteries. Or leave it on auto. It will connect them when charging, disconnect when either battery drops below a specific voltage. Connect the start isolate wire and it will automatically isolate the batteries when you start the truck. UNLESS you manually connect them with the switch. So you leave it on auto all the time and it requires no brain intervention. If you need to connect them to help start or winch, flip the switch.

 

[rayra]

'battery isolator' / diode. Get thee to the power subforum, all is revealed there.

 

[Ducky's Dad]

Or look at the Painless Performance battery isolator. Puts a toggle switch on your dash that connects to their solenoid and allows you to manually select which batteries are starting or charging or out of the system. You choose, nothing automatic, but you can do it from the driver's seat, even while you are rolling down the highway. I have it on two trucks and it has worked just fine for 17 years. I'm adding a third battery to one of the trucks and will keep the Painless system but will use a Blue Sea manual switch to control drain and charging on the #2 and #3 batteries. Essentially, I am using the Blue Sea switch to isolate 2 from 3, and the Painless solenoid to isolate 1 from the other two. The house batteries will be primarily for the frig, but can also be used for starting or winching or running OBA and lights. My belief is that anything that is automatic will be more likely to fail.

 

[johanso]

Thanks guys!

 

[1stDeuce]

Those kits work great, and require a minimal understanding to wire them in, but they are EXPENSIVE!!

For a cheaper option, just put a continuous duty 12v solenoid between the batteries, and wire it to an source that is only hot in "run". (Or crank and run in your case, assuming you want both batteries to help start the vehicle.) You could easily add a SPDT switch to have on-off-auto capability if you really think you need it, but I never did on my truck, and never wished for it. The solenoid will separate the batteries when the vehicle isn't running, and connect them when it is. VERY Cheap and VERY simple, two of my favorite things in a mod.

BTW, normal starting batteries don't last long if you discharge them like you're planning to do... When you replace the aux battery, put a deep cycle marine battery in. It'll still do fine for starting, but it'll live through far more discharge cycles.

 

[1stDeuce]

Hmm, it occurs to me that since you're in Sweden, you might have a 24v system... If you do, nothing you're talking about will work, or is necessary, because you need both batteries to make 24v. To run 12v stuff, you just wire it to the battery closest to ground. (The one with the ground wire going to the frame/engine.) I've heard that the "low" battery will not charge well from a 24v alternator if it's run down very far, but it probably depends on how often and how low you discharge it. For small loads/discharge levels, I don't think it matters so much.

I spent a few weeks in Arvidsjaur for work a good many years ago. It was Nov/Dec, and it was awesome! Would love to visit again in the summer!

 

[Ducky's Dad]

I missed the part about Sweden, but for those of you in North America, be aware that the Optima Blue marine batteries are not all deep cycle, so be careful if that's what you are buying. Optima makes a Blue marine starting battery and a Blue marine dual purpose (starting and deep cycle). I ordered a pair of Optima Blues for my truck's house batteries and even gave the battery distributor the part numbers. They sent over a pair of Optima Blues that were not deep cycle, so we called to get the right batteries and they tried to insist that the batteries I had were deep cycle. Wrong. Some phone time and referring them to the Optima catalog convinced them to send the right batteries. Only obvious difference is the case color. Starting blues are a darker gray than the dual purpose blues. FYI

 

[johanso]

Hmm, it occurs to me that since you're in Sweden, you might have a 24v system... If you do, nothing you're talking about will work, or is necessary, because you need both batteries to make 24v. To run 12v stuff, you just wire it to the battery closest to ground. (The one with the ground wire going to the frame/engine.) I've heard that the "low" battery will not charge well from a 24v alternator if it's run down very far, but it probably depends on how often and how low you discharge it. For small loads/discharge levels, I don't think it matters so much.

I spent a few weeks in Arvidsjaur for work a good many years ago. It was Nov/Dec, and it was awesome! Would love to visit again in the summer!

I have a 12 volt system. The Blue Sea ACR 7622 seems to be the answer to my quest. Darn expensive though…

Arvidsjaur is pretty dark and cold in the winter. Did you do cold weather testing of cars? Thats usually what people do there. Summer up there is nice. The sun is up almost 24h/day.

 

[1stDeuce]

Yes, I was there for testing. And it was daylight from about 10am to 3pm I think. Lots of lakes and forest. And little red and white houses. We went up north of the Arctic Circle for a day and hung out at a little town to the north during their pre-christmas celebration. Also got to attend a St. Lucia ceremony, which was really great! And we drove past reindeer walking on the side of the road almost every day. (Who knew they were like cows with antlers??)

That Blue Sea unit is pretty cool, but it's just a pretty version of the 12 volt solenoid I was telling you about that you can get for $20. It does come with a very pretty switch though.