[mopar21]

hi im looking at doing a dual battery setup i have 2 exide brand batterys does anyone know of a dual battery bracket or has anyone made one?also kinda clueless on how to start for the wiring is there a kit or am i gonna have to build it myself any help would be appricated thank you

 

[Elwenil]

I did this one on my old '74 W100:

It's made from old bed frame rails. If I were to do it again, I would move it to the passenger side. The Driver side already has enough weight on it with the steering box, column, brake booster and master cylinder and the driver. In the case of a pickup, usually the fuel tank is on that side as well.

 

[u2slow]

I'd also be trying to get the battery to the passenger side.

Here's pics of a dual battery 'kit' I saved from the interwebs...

 

[mopar21]

i was thinking of moving it to the passenger side as well!!now for the wiring should i do it in series or parallel??thinking of just buying bulk cable and building it all

 

[crazzywolfie]

hahahaha you always got to wire them in parallel or you would get 24v . you do got to use a solenoid or isolator to separate the 2 batteries.

 

[deathrowdave]

I have been reading this post . I understand you want two batteries . I understand you want second battery on pass side I have seen an M880 with pass side battery . But I don’t understand the need for an isolater or anything to separate the two . They should wired + to + and - to - and so be it . I have owned a few muscle cars with two batteries sitting behind the right rear wheel in the trunk , never had any special wiring and never one charging issue . Please help me to understand what I’m missing . Thanks

 

[SuperBurban]

If the two batteries are the same make, size, and age, then wiring them in parallel is ok. The more difference between the two batteries, then you need to think about an isolator, or solenoid. Batteries of different sizes, will tend to fight each other, and the bigger battery will never get to a full charge.

IMO, the isolator is the best way for the batteries. it keeps them electrically separated, but still allows each to get to full charge. Then have a solenoid controlled by a push button, to hook the two together if needed for the extra boost for starting.

Just using a solenoid to hook them together, while the engine is running, is not much different then hooking them together all the time.

The way my Camper is wired, the starting battery is wired to the starter, one wire goes to the key switch, to power the starter relay, a wire to the isolator, and a big wire from the boost solenoid, that has the secondary batteries hooked to one side, and the other side goes to the starter relay. The is a switch on the dash, so I can use it to hook all the batteries into the starting circuit. Everything else, is run off the secondary batteries.

 

[Elwenil]

Yeah, to me the best way is running a solenoid to separate the two batteries.  This prevent "dueling batteries" is you believe in that, but also keeps the second battery in reserve in case something drains the primary battery.  There isn't much point in dual batteries, in my opinion, if you just drain them both down.  For certain special uses I can see leaving them connected, like a drag car with no alternator that needs the capacity, or something but for most cases you will want the extra battery either for winching, as a reserve or just to double the cranking amps when needed.  In my situation, a deep cycle and a standard battery would need to be separated and I used the deep cycle just for "self jumping" the main battery when I ran it down.  That's a bit backward from how those are supposed to be used, but it's what worked best in my situation.

 

[crazzywolfie]

i personally look at it as you are better off safe than sorry with the battery and running a solenoid or isolator especially with how cheap they are especially when compared to the cost of replacing a battery. like most have pointed out you really don't need 2 batteries so the second battery would really only be needed for boosting or running accessories so it really doesn't need to be connected to the system all the time. it only needs a charge here and there to make sure it is topped up.

 

[KThaxton]

As mentioned, you must isolate them unless you always want to use identical batteries, of the same age....and if one fails, you need to replace both of them.
When batteries are just slightly different, even if they are identical but a different age, their internal resistance varies slightly. As they sit when not in use, they start to drain each other because of the difference in internal resistance.

In my RC, I needed a second battery for running a 12 volt cooler on multi-day backcountry trips. I also tied my 12v compressor to it. Therefore I needed a deep cycle. I used an RV solenoid to separate them that was operated by a rocker switch on the dash. This switch was tied in with the key-on 12v circuit, so when I did have it engaged, I didn't have to remember to switch it off when shutting the engine off.

 

[Mad Max]

I'm looking at a dual batt setup as well tho I haven't shopped for isolators in quite a while - what are y'alls recommendations for a good HD isolator?

 

[u2slow]

I like Blue Sea devices. I used a bunch of their stuff, including an ACR (auto charge relay) for running an inverter with dedicated battery in my work van 10-12 years ago. https://www.bluesea.com Add a basic battery battery switch to bridge the two for 'emergency' starts; or better yet - two - so you can take the dead battery out of the system. A big part of making it work is deciding what loads will run from which bank.

Funny thing is... having had 3 batteries in that Ford diesel van, I'm quite happy to just have one per vehicle these days.

 

[crazzywolfie]

i think it really depends on what you are using the 2nd battery for. if your just using it for boosting a regular solenoid would probably get the job done. i have been considering installing a e-bike battery in a couple of my vehicles for boosting. 20ah batteries seem strong enough to crank a v8 on its own but would work pretty good for boosting purposes when needed. i have already been dropping them in some of my old booster packs with dead batteries.

 

[SuperBurban]

Those e-bike batteries have special charging needs. Some of it is likely built into the battery, but other things like limiting the current, to only a few amps, is done at the charger end. I would not hook them to a car alternator to charge, it could get ugly, since they like to burn up when over charged.

 

[crazzywolfie]

i don't think it would be too bad. it is not like they need to be charging every time you have the vehicle on plus they say about 13.7-14.9 for charging which is about what a alternator would put out. it would only mainly be needed for boosting. i know i got a pretty good battery in my 81 but not so sure about the battery in the 89. plus could always limit the charging with a fuse.

 

[u2slow]

... plus could always limit the charging with a fuse.

Controlling voltage vs current are two different things. These special batteries probably need a charge controller. No sense in popping a fuse each time you've drawn the battery below 80% (for example).

 

[SuperBurban]

They need the special charge controller. Charging them after they are fully charged, can make them explode.

I had a lipo battery from an RC car, swell up when charged. I wrapped it in foil, and sealed it in 2 ziplock bags, and buried it in the back yard, where there is nothing but hard clay & rocks.'

They are nice, but can be dangerous if handled wrong.

https://phys.org/news/2016-01-incorrect-battery-triggers-explosion.html

 

[KThaxton]

They need the special charge controller. Charging them after they are fully charged, can make them explode.

I had a lipo battery from an RC car, swell up when charged. I wrapped it in foil, and sealed it in 2 ziplock bags, and buried it in the back yard, where there is nothing but hard clay & rocks.'

I had a Lipo puff up so discharged it with the charger, clipped the connector off the ends of the wires, soaked it in salt water over night then threw it in the trash.

 

[crazzywolfie]

these are not lithium ion batteries. just plane old lead acid batteries

 

[Mad Max]

...for me the main purpose for a second battery is to power the accessories when camping (stationary and engine not running), but it also needs to be able to back up the primary so I am going with the dual purpose deep cycle/starting units from X2 Power, and I'd also like to be able to link both together when winching and potentially 24v welding...