Cheap dual battery setup. Is what I'm working on safe? (1 Viewer)

[BT80]

Hey guys, I posted in general tech also but this pertains to my 80 so figured I might should post here too in the event there is something 80 series specific I may be overlooking.


I'm rigging up a quick simple dual battery setup primarily to run a fridge on my Atlanta to Alaska adventure. We leave tomorrow! So I'm down to the wire...no pun intended.

Anyway what I've got in question is whether the setup I'm working on is safe or if I need to rethink my plans.

I've got 2 batteries, each 1000CCA 115Ah lead acid.

What I'm proposing is running a 4 gauge wire from the positive terminal of the cranking (main) battery to a marine on off switch into the cab easily accessible i.e. The side of the center console or something if the sort, then another 4 gauge wire from the switch to the secondary positive terminal. Then simply ground the secondary battery to frame.

This will allow me to separate the main from the secondary when we turn off the truck for any significant period of time. Allowing the fridge to keep power flowing from the secondary battery.

The couple concerns I have is as such:

Do I pose any risk running such a long strand of 4 gauge wire that long length into the cab and to the battery, were talking several feet of wire?

Secondly, should I be ok supplying 2000CCA while starting the vehicle, or should I disconnect (switch to secondary on off position) every time I crank the truck?

Thoughts, ideas, concerns?

I do also have the option to leave the switch out of the equation and just run the batteries in parallel because the fridge is SUPPOSED to shut off if it detects low battery. But I don't completely trust this, I haven't been able to test it.

 

[Cruiserdrew]

Don't run your switch into the cab. Leave it in the engine bay. You're doing a quicky install, keep it simple.

Upsize your wire to 2 gauge

Fuse both + leads at the battery with 150 amp fuses.<<<This is the most critical part of your install. Shorts in big cables = fire.

Does not matter when cranking the truck.

The fridge battery shut downs are at too low of a voltage. By the time you're at 10.8 volts, your battery is dead.

 

[45Kevin]

I'm no expert but I've been jonesing for a dual battery set up and will be using this method. Ignore the second house battery in your case. I was planning to run about 10' of the 4 guage. For both pos and ground. The diagram is from a dude on ExPo.

 

[Douglas S]

Don't run your switch into the cab. Leave it in the engine bay. You're doing a quicky install, keep it simple.

Upsize your wire to 2 gauge

Fuse both + leads at the battery with 150 amp fuses.<<<This is the most critical part of your install. Shorts in big cables = fire.

Does not matter when cranking the truck.

The fridge battery shut downs are at too low of a voltage. By the time you're at 10.8 volts, your battery is dead.

FWIW there are exactly zero fuses in the heavy battery cables of a factory dual battery cruiser. Not saying it's right, just saying. The runs are short enough that the risk is minimal if the cables are properly secured.

 

[Cruiserdrew]

A factory set up is engineered by pros. This is a quick and dirty by presumably a non-professional. It needs to be fused, or risk burning down the truck.

 

[dogfishlake]

I ran an optima in the right rear trunk area of my old street/road race 65 mustang for years. That cable ran through the inside of the car with fused ends, worked great. I've agonized over where to put a second battery up front, but @45Kevin post looks like a great setup, perhaps upgrading wire size like @Cruiserdrew said. Sounds like an amazing trip- have fun!

 

[BT80]

I've searched high and low for some 150A fuses locally and coming up dry.
I've worked for Honda and currently work on commercial airplanes, so I fee fairly competent in the install. I've already routed the cables in cab and the resistance on the length of cable should be perfectly fine with the 4g wire...and these trucks only charge at absolute max at around 80-90a. I may have no choice but to run without fuses for the time being. Maybe I can find some tomorrow but most stereo shops are closed here

 

[superjuice]

I've searched high and low for some 150A fuses locally and coming up dry.

There's a west marine in Atlanta off 41 near dobbins air base

 

[greentruck]

If you do the install right, then cruiserdrew's advice doesn't apply.

If you do it wrong, then it might be a bad day.

If you feel competent, even when rushing at the last minute, in getting the cables routed and loomed, then go for it. Just saying that it's a long and winding and bumpy road to Alaska. If you have the potential for a rub through at a sharp spot, that's a likely way to confirm it.

This is not withstanding the observation that Douglas made about Toyota engineering.

 

[LandCruiserPhil]

Keep it simple and follow the trucking industry and tie the battery's together and call it good. Major truck manufactures have been doing that way for years trouble free without fuses.

Do not ground your second battery to the frame unless you ground your main battery also.

 

[Cruiserdrew]

If you do the install right, then cruiserdrew's advice doesn't apply.

.

Sorry, but this is bad advice. Just because "most" people have gotten away with it for years doesn't make it right. With the vibration, and stress, and last minute prep, and the inability to predict everything that might happen, a fuse, takes away all of the risk. Things chafe, especially running into the cab, not worth the risk to me. Fuses also make it easier to work on the system, because you can remove the fuse, and the entire circuit is dead. So you can work on it with no concern.

 

[greentruck]

Andrew,
I agree with you, just trying to introduce a bit of levity in a serious conversation.

The problem with being wrong in this case is that you think everything is good until it isn't. The problem with being right is that you can't be sure being fused matters...unless you like peace of mind, which I think is your point here, beyond safe engineering practices.

 

[LandCruiserPhil]

Again truck manufactures do not use fuses. He needs to wire two battery's together its not rocket science. Yes it can be a problem if not done in a safe manor but the same caution apply when changing a tire.

 

[greentruck]

Tying two batteries together that are in the same location/tray isn't rocket science. You don't get it right, you'll usually know before you leave on a trip...

But once you get the wire going hither and yon, then I think Andrew's advice is worthwhile to consider. Plus burning the truck down doesn't get you closer to Alaska. However, sounds like the OP has expertise, so he knows what's best for him. Me? I got fuses on everything that leaves the engine compartment that I added. Things go wrong, even if put in right, too.

 

[BT80]

Any reason I couldn't run some 100 amp maxi fuses, sourced those at the local Walmart of all places. Just happened to be going by to pick up last minute provisions and checked over in the car stereo section. The largest fuses they have are 100, think those will pop?

 

[BT80]

And thanks for the replies, I do trust I've got things routed in a very unobstructed way that shouldn't allow for chafing but I do agree fuses are the safer route.

 

[Cruiserdrew]

Sounds fine. You will rarely exceed 100 amps, and 4 gauge can likely carry that. Much better than an unprotected circuit.

 

[BT80]

Thanks Guys I'll run that. Worst case I'll have to track down larger maxi style fuses down the road.

 

[dales33]

In mine ive put a second battery tray under the hood and run 3 B&S cable with a 100amp circuit breaker inline running to a revolution VSR (voltage sensitive relay) then to the second battery.
Both batteries are grounded to the frame.
The beauty of having a voltage sensitive relay is that once the house battery reaches 13.6v the relay opens and starts charging the second battery.
I just got an abr sidewinder battery management unit to install in the cab so i can monitor both batteries or link them together for starting if required.
I would go this route if i was tou. Much better way of maintaing a good starting battery and maintaing the 2nd.

 

[Dave 2000]

Fusing between the batteries is the way to go IMO, check out my sig for the link to my various mods including wiring. I would add that if you leave the batteries in parallel, and your starter battery fails, you could jump start via your house battery however, the low amp fuses will not hold for long, in particular if you have to crank awhile for your engine to start.


I 'think' your gasoline engines use a 2000 watt starter? If so then you need to cater for around 150 amps plus 'pull', a 100 amp fuse (assuming no dead short) should manage 200 amps before it blows.

If you do plan to try and start from the house battery in an emergency for example, you might want to link the batteries with jump leads to take the load off the fuses?

regards

Dave