[Derek Foote]

Hello,

I want to charge my 2 140amp house batteries off the Van battery. I currently have a breaker 25 (amp) in line off of the + of the car battery, running to a Voltage Sensing Relay (VSR), to the 1st house battery, then another vsr between the 1st and 2nd house battery. The (-) is grounded from the chassis through the 2 house batteries.

My questions is I have seen diagrams with a switch between the van battery and the house batteries. Do I need this? Am I at risk of ruining my batteries?

Any help would be appreciated.

Thanks,

Derek

 

[GaryBIS]

Hi,
I'm not seeing what the 2nd VSR is doing for you? I think that if the two house batteries are the same size/type that you can just hook them up in parallel with a single VSR between the van and pair of house batteries.

The VSR is basically there to insure that the house batteries are only hooked up to the van battery and charging system when the van is running. If you did not have it, there would be a danger of having the van battery run flat by house loads along with the house battery.

I don't think that normally a separate manual switch is needed between the van battery and house battery is needed. But, it does give you some extra flexibility when you want to be sure the house battery is not connected to the charging system.

The main function of the breaker (or fuse) is to protect the wiring between the van and house battery in case there is a short somewhere along this wiring. Since you have power sources on both ends (van bat on one end, and house bat on other end), you should really have a breaker or fuse on each end -- they should be located as close to the batteries as possible.

Disclaimer -- this is just my 2 cents -- I'm not a wiring expert.

Gary

 

[Lynnandj]

The Winnebago Travato, class B built on a Promaster frame, has a switch.
My opinion is a switch can't hurt; and may help isolate a battery problem if it ever arises.

 

[papab]

You're going to trip that 25 amp breaker.
I think a switch is a good idea, although probably not a big deal. If the house batteries are fully charged, agms need a float voltage of about 13.4, the van puts out 14+, so you could overcharge them on a long trip.

 

[RDinNHandAZ]

Thinking about this I guess I will put a switch in to let the MPPT controller from the solar top up the coach AGM golf cart batteries and only charge from the van when it has been a while and/or the batteries are down.

 

[Derek Foote]

Thanks for the time. I have it hooked up and it seems to be working. I have such a low electrical draw that its hard to say. I guess I can remove one of the VSR's. I'll admit the 25 amp breaker is low, but is was all they had at the time, but it hasn't tripped yet. I have a 1000k drive tomorrow, so that will be a good test. Does anyone know if the van battery will continue to run current to my house battery when the car is off but with the key is in or the interior lights are on? Or does the van need to be running?

Thanks,

Derek

 

[proeddie]

If the van is not running, the voltage of the van battery alone should not trigger the VSR whether the key is on or not. The VSR is designed to sense charging voltage from the alternator, and a charged van battery, and then make the connection to charge the aux battery.

VSRs are also called isolaters. They isolate the van battery from the aux so that they are not connected unless the alternator is providing charging voltage to the house battery.

Ed

 

[Derek Foote]

Great- Thanks for clearing that up.

Derek

 

[papab]

Your 1000k drive probably won't trip the breaker. The battery will draw very little current when it's charged up. It the battery is low it will draw a lot. I have a trimetric battery monitor & a current sensor on my setup & with 1 150 ah batt I saw more than 25 amps quite a bit. Up to 100 amps.

 

[proeddie]

The trick is to hook up something to your battery and let it run down (not dead, just under 12V). Then take your trip.

As papab says, it will draw the most amps when it needs recharging the most... when there is big difference between the van battery and the aux battery.

If you go an a trip with a fully charged battery, you won't learn much about its charging needs.

Ed