Dual Battery Setups! Let's see them! Multiple Batteries Thread!

Are you asking about floating the house 12V relative to the vehicle? Since you mention using a DC-DC charge it'll usually best to keep everything 12V at the same reference, e.g. use the truck frame as the common ground. If the two systems were completely isolated it could float and even with the DC-DC it might be fine but referencing the lithium negative to chassis ground (frame) will prevent any chance of an issue.

FWIW, you didn't ask but you might be thinking about a 120VAC house system such as would be the case in an RV. In those cases grounding and floating are a different subject. In that case floating is going to be safer and how you get power and ground for the inverter you use to create the 120VAC is a bit more important to prevent the vehicle from becoming dangerously hot in a fault.

 

Great points in here. I should note my charger/controller contains breakers within the unit to prevent issue on the isolated system.

 

Just so someone reading from the middle isn't confused, a breaker will prevent over current but not over voltage, which is the concern when you float a house system. Also choosing to bond the negative to chassis factors into the possibility of ground loops and noise. It ultimately just depends on a lot of factors. I'd have thought both sides of a DC-DC would be tied to a common reference but mainly you should follow whatever the manufacturer of the device you have suggests.

 

No plan for inverter at this point. Had considered running AWG6 cable from Lithium negative to truck frame under rear wheel well, but that idea on hold. Was wondering since DC/DC charger is connected to starter battery pos and neg, that device is 'grounded' thru the starter circuit? The common ground reference is the one screw under the hood? I wanted to avoid running a long ground cable, that's why considered short strap from -post to frame under rear wheel well.

 

the frame has far less resistance than even 4/0 gauge wire. I would recommend using the frame . However, don’t forget to upgrade grounding gauge wire or strap on the other end from either the frame or chassis whichever you choose.

 

A very solid connection on each end of the frame is critical for sure. The biggest issue I find with using the frame for circuit returns (which I do) is the connections you make can be fickle. They need to be bare metal and kept from corroding. Sometimes it's more reliable long term to run a long return cable.

 

I concur. I use existing holes or bolts first. Grind them down to bare metal. Always use a star washer. Finally, cover the connection in white lithium grease

 

Made the change from ML-ACR to

$458 Redarc BCDC1225D REDARC 25A in-Vehicle DC to DC Charger with MPPT — Dual Input for Solar & Alternator Charging, Green Power Priority - 12 or 24V Battery Charger Suitable with AGM, Gel, Lithium LiFePO4 Batteries

Redarc BCDC1225D. Pulled the 2AWG from the OGE kit and made my own 8AWG wires. Wasn’t planning on picking up the OGE specific mount so used double sided tape and zip ties. I think it should be sufficient.

 

Getting all my parts together to do my dual battery install. I already have the ML-ACR but was also thinking of switching to the redarc.

What made you end up switching?

 

My Odyssey batteries for some reason weren’t liking it. My starting battery would alway drain. Luckily, using the ML-ACR, I was able to connect the batteries and start my truck.

Atleast now, I know my secondary battery will be topped off. If I remember, I’ll put my starting battery on a charger once a month or so.

 

Have you read this thread - https://www.tacomaworld.com/threads/the-northstar-agm-battery-voltage-booster-upgrade.604478/

Not so much about the NorthStar battery, but about the preferred/required higher voltage requirement of an AGM battery.

With our "smart alternators", dual batteries will never both charge completely tied in parallel.

I don't want to rewrite that thread here, so I suggest you take a few minutes and peruse through it - there is some really good info there.

 

Thanks for reminding me. Added that link to the OP

 

So the Redarc has the ability to tie or separate the batteries just like the ML-ACR?

 

I've been getting parts together for adding a dual battery system. Does anyone have a parts list of that they used and the sizes they used? For example, what size wire and how long...what size fuses????

I already have both the stock location and aux location battery trays as well as the blue sea ml-acr.

 

it does not have the ability to tie the 2 batteries. It ensures the secondary battery is properly charged.

 

So your system is full-time separated? One for the truck and one for aux loads, with no tying them together? You said you switched the ML-ACR out for the Redarc which made me think it could do that

 

The ml-acr directly connects them together. It does not control charging it leave that for the alt. Wiring needs to be larger so you can link to start if the main battery is dead.

the red arc is a charge controller. Aka it can charge the second battery from the first but does not connect them together.
To self jump you would need to carry jumper cables to link the batteries

 

Yup. I was just confused by his post a few back when he said he went from a ML-ACR to a Redarc. In my mind that implied the Redarc could do both, which wouldn't make any sense electrically..

 

I stumbled across this the other day. It looks like REDARC does offer a self jump starting solution.



https://www.redarc.com.au/bcdc-dual-with-jump-start-feature-the-ultimate-battery-setup

 

Honestly I wouldent pay whatever price they want when it’s easy to do the same thing with an old school starter relay. there like $15 at any part store