Lithium batteries move the batteries and install the victron shunt.

[Ron in BC]

Negative on that. The only time that I ever would use "both" would be for the microwave, which I no longer have, And I never would consider using the microwave unless I had pretty full batteries.

The purpose of the battery switch is to isolate the batteries and there's no need to ever have them paralleled. Simply go "1", "off", "2".

I normally use one battery for a few days and then switch. With solar and my typical usage I could probably exist with one battery. But if you loose a cell and the battery goes from hero to zero it's nice to be able to flip a switch and carry on without any disruption to your plans.

Ron

[John in Santa Cruz]

so how do you recharge the 'off' battery ?

if you opt to get a battery monitoring system like the Victron, you'd best get *TWO* since you have two isolated batteries

[alanmalk]

Originally Posted by Ron in BC

Negative on that. The only time that I ever would use "both" would be for the microwave, which I no longer have, And I never would consider using the microwave unless I had pretty full batteries.
...

Ron

Point taken. The folks with inverters used with toasters, microwaves, coffee pots, hair dryers, etc., need a parallel connection for the high amperage. A single ("ordinary") battery won't supply hundreds of amps without significant voltage sag, or in the case of LiFePO4, without tripping the BMS protection. Also, the simplicity of parallel connections can't be beat. (Folks with two 6 Volt batteries can ignore all of this, btw.)

For context: I used the 1-2-Both-Off switching in my sailboat where not being able to start the diesel engine may have been a life-or-death situation. Two different types of batteries (normally isolated) were involved - a totally different situation than trailering.

[Ron in BC]

Originally Posted by John in Santa Cruz

so how do you recharge the 'off' battery ?

Since the "off" battery is one that you left fully charged a few days ago that's a moot point. Well, actually, it is the point. I lost a cell in my old Scamp, flick, and I'm using my fully charged battery. No crisis.

Yes, marine use is a little different. Isolating the starting battery is always the prime concern. In my sailboat I had double selector switches. The first one was 1,2. Start and battery bank. The second was to isolate each house battery. But that's just me.

Ron

[alanerickson]

Originally Posted by Centex

You're probably already on top of this - I'd work to bring the two batteries independently to as close as possible the same SOC/voltage before making the final connection between them (minimize sudden current-flow between them at the moment of connection).

Yep, someone else already clued me in on this one. I've also seen recommendations to connect when fully charged and will probably do both charged and at same voltage.

[John in Santa Cruz]

Originally Posted by Ron in BC

Yes, marine use is a little different. Isolating the starting battery is always the prime concern. In my sailboat I had double selector switches. The first one was 1,2. Start and battery bank. The second was to isolate each house battery. But that's just me.

in a sense, towing is much the same, at least if your vehicle has an isolation relay on the hitch power (my Toyota and Ford does). When the engine is not running, the car battery is disconnected from the trailer.

[WanderBred]

For the charger to charge two or more batteries should I put in bus bars for positive negative and run separate lines to each battery for charging equally?

[alanmalk]

Originally Posted by WanderBred

For the charger to charge two or more batteries should I put in bus bars for positive negative and run separate lines to each battery for charging equally?

How are these "two or more batteries" connected? Permanent, in parallel, for example?

[WanderBred]

They will be in parallel to make 12 volts.

[alanmalk]

Originally Posted by WanderBred

They will be in parallel to make 12 volts.

Two 12 Volt batteries, permanently in parallel, is the setup I used for 7 years without doing anything "special". I hooked up the various chargers (solar, WFCO) on single charge lines just as if it was a single battery - which it essentially is, just larger than one battery.

[John in Santa Cruz]

there is a proper way to connect to two batteries in parallel. essentially, make sure the two cables that interconnect the batts are the same gauge and length, then connect your load and charging to ONE batts positive, and teh OTHER batts negative. this equalizes the wire resistance to both batts so they charge and discharge equally.