Thread: Deciphering Dual Battery Setup

Hi,
I may well be wrong, but that photo of the relay looks like one I had in my truck years ago and that was not voltage sensing.
Link to Redarc VSR
Link to Traxide dual battery setup
A couple of links above may help a bit.
cheers

the relay/isolater in the diagram was just a random one i grabbed off google. the VSR sits seperately.

had a bit more of play, got the isolator relay to bridge the two batteries but nothing much happened. both batteries are stuffed and need replacing though (starting battery struggled to start the motor when cold, and is flat in a day without use )

got some pics of the real ones.


and the VSR Module. it's screwed in underneath the relay block, next to the expansion tank

all good now, after some more research looks like i was on the right track.

the VSR module sounds like a good thing; allows aux. battery to trickle charge, don't have to mess around with alternator/ignition wires as it's automatic. allthough i can't find much info on VSR modules, regardless of brand, model etc.... i would've thought they'd be more popular?

these are two others i found, similar in operation to mine. but not much info at all regarding their use with dual batt. setups
Automatic voltage sensing ACR split charging relay 12/24V 120A [BlueSea 7610 ACR] - £82.03 : LED Lights, Marker Truck LED Vehicle Lighting Trailers Commercial Lightbars Warning Lights Land Rover

http://www.rawcomponents.co.uk/relay...v-relay-1.html

EDIT: ok found why they're not really popular. something like the Redarc SBI12 solenoid is effectively the isolator and VSR module combined into one, which would make things a lot neater than installing the two seperately (as was done in mine)

and now i'm just thinking out allowed, so can close this thread

Hello there!
The VSR is electrically the same as a Redarc unit, it already contains a high current relay.
It looks to me like the original owner has set up the second relay to manually connect the two batteries for winching/ or starting the car if the main battery went flat (maybe leaving on the headlights etc.
Also, the way you have the switch shown (with the earth on the right) it will short your acc supply when you turn it off, just leave that side not connected (unless it's a switch with a light in it, in which case your diagram is correct!

Cheers,
Fraser

Originally Posted by robzilla

all good now, after some more research looks like i was on the right track.

the VSR module sounds like a good thing; allows aux. battery to trickle charge, don't have to mess around with alternator/ignition wires as it's automatic. allthough i can't find much info on VSR modules, regardless of brand, model etc.... i would've thought they'd be more popular?

these are two others i found, similar in operation to mine. but not much info at all regarding their use with dual batt. setups
Automatic voltage sensing ACR split charging relay 12/24V 120A [BlueSea 7610 ACR] - £82.03 : LED Lights, Marker Truck LED Vehicle Lighting Trailers Commercial Lightbars Warning Lights Land Rover

Intelligent Voltage Sensing 100 Amp 12v Relay - 12V - Relays & Holders - Raw Components Ltd - Auto electrical Supplies - Specialists in Split Charge Kits

EDIT: ok found why they're not really popular. something like the Redarc SBI12 solenoid is effectively the isolator and VSR module combined into one, which would make things a lot neater than installing the two seperately (as was done in mine)

and now i'm just thinking out allowed, so can close this thread

robzilla,

What you have identified as the sensing module should be used to drive the relay, otherwise the relay is only connecting as a result of the manual application of the switch. You could get much faster charging of your aux battery if it was connected to the rest of your charging system via your relay. If connected up as I suggest then the aux would only be charged after the primary battery has got to the 13.7 volt level and will isolate the aux battery when the voltage drops to 12.8 volt.

Then again if you want to have manual control and trickle charge only at other times then leave it as is.

I'm assuming though that once the car is running, the alternator puts out ~13-14V through the system, which will make the VSR kick in and trickle charge the Aux.
So even if the main batt. is low, both batteries will recieve charge as soon as the car starts.
Happy to keep the big relay manual as well. Would rarely need to bridge the batteries so easy enough to leave the switch in as is.

allthough i'll keep in mind using the manual switch for quicker charging as well. hadn't thought of that but might be times when the Aux. is flat and i need charged ASAP!

Hi robzilla, your VSR is a relay and as such will automatically cut-in once the motor is running and will cut-out once the motor is off or a short time after the motor stops.

You will not get any faster charging by switching on the solenoid, it seems to be there purely to jump start if needed and to join the batteries during winching.

To avoid accidentally leaving the switch on and flattening both batteries, leave the switch off unless you actually need a jump start or to winch.

While your set up will work when winching, if you do decide to do some rewiring, you would make your winch operate more efficiently if you moved the winch power cables to the cranking battery, this would mean a short cable distance between your winch and the alternator and this means less voltage drop which ultimately means a more efficient winch operation.

That VSR looks like my old BEP Marine one. Housing shape is still the same but the newer models have a heap more writing on them:

Voltage Sensitive Relays - BEP Marine