Voltage Sensing Relay (VSR) failure

[Goz]

So I've just drive to the cote d'azur and about 100 miles from our destination everything plugged into the leisure battery stopped working. I've now got the multimeter out and checked whats going on and the VSR is not responding at all. This has happened before when the leisure battery has got very low but that generally seemed to be the ground in the VSR giving gip. This time there is no response and the ground is registering correctly as connected to the chassis. So I'm pretty sure the VSR has died completely.

Ideally I'd like to just bypass the thing ... its given me plenty of gip over the years. I've been told, in the past, that its possible to wire the thing so it only comes on when they key is at ignition position 2. Does anyone have any ideas on how to do this?

Any thoughts or help appreciated!

[mikeonb4c]

So I've just drive to the cote d'azur and about 100 miles from our destination everything plugged into the leisure battery stopped working. I've now got the multimeter out and checked whats going on and the VSR is not responding at all. This has happened before when the leisure battery has got very low but that generally seemed to be the ground in the VSR giving gip. This time there is no response and the ground is registering correctly as connected to the chassis. So I'm pretty sure the VSR has died completely.

Ideally I'd like to just bypass the thing ... its given me plenty of gip over the years. I've been told, in the past, that its possible to wire the thing so it only comes on when they key is at ignition position 2. Does anyone have any ideas on how to do this?

Any thoughts or help appreciated!

I assume the circuit is fused (at both ends i think it should be) and that a flat lb hasnt caused a current pull thats blown them. But yes i cant see why you cant just connect in parallel to lb (fused of course) and use an isolator switch to disconnect it from sb when parked up. And in case lb is flat start car before reconnecting. But Geoff is the expert on this so hopefully he'll comment. My VSR can be very clicky at tickover but so far hasn't failed in 10years or so (fingers crossed!)

[g8dhe]

Yes check BOTH fuses, if the one to SB has failed then the VSR will do nothing at all. Its always the case that if one fuse blows you need to replace BOTH fuses as the other one will have been partially melted as well and fails at the most inopportune time.

Yes a Split Charge Relay can be setup to be switched with the Ignition, however if its an all in one Voltage Sensitive Relay then that's not normally possible as the circuitry is all inside the case. For an Ignition controlled setup then a standard Relay wired to the IG2 circuit is all that is needed.

[mikeonb4c]

Yes check BOTH fuses, if the one to SB has failed then the VSR will do nothing at all. Its always the case that if one fuse blows you need to replace BOTH fuses as the other one will have been partially melted as well and fails at the most inopportune time.

Yes a Split Charge Relay can be setup to be switched with the Ignition, however if its an all in one Voltage Sensitive Relay then that's not normally possible as the circuitry is all inside the case. For an Ignition controlled setup then a standard Relay wired to the IG2 circuit is all that is needed.

What about hard parallel wiring (fused of course) between SB and LB and fitting an isolator switch for when engine off. Would that be ok as a simple way of charging LB whilst on the move? Usual caveats about isolating when parked etc

[g8dhe]

A hard connection won't isolate the LB during starting you will end up with both batteries being discharged and the LB won't like the excessive current that will be drawn from it during starting.

[JulesMartin]

In my previous madness of owning a VW T25 camper the LB was hard wired via an isolator switch to the SB. This setup worked ok but it was a pain to remember to switch over when parking over night and to switch back again after starting in the morning so an automated version would always be my personal choice. I'd get your current setup repaired before considering going down the manual switching route. Also remember that LB's are not built in the same was as SB's and cannot take the internal massive amperage draw when starting.

[mikeonb4c]

A hard connection won't isolate the LB during starting you will end up with both batteries being discharged and the LB won't like the excessive current that will be drawn from it during starting.

Absolutely. You must isolate as soon as you stop engine and only reconnect after starting it. But if those rules are followed i guess it would be fine? In a way, all you are doing then is acting as a human VSR

[mikeonb4c]

In my previous madness of owning a VW T25 camper the LB was hard wired via an isolator switch to the SB. This setup worked ok but it was a pain to remember to switch over when parking over night and to switch back again after starting in the morning so an automated version would always be my personal choice. I'd get your current setup repaired before considering going down the manual switching route. Also remember that LB's are not built in the same was as SB's and cannot take the internal massive amperage draw when starting.

Absolutely, thats the real problem - you have to remember to do it, do it, and do it right, every time. The words 'human' and 'failings' come swiftly to mind

[Gripped]

We went for a simple but effective Lucas 30A split charge relay. Connects both batteries with ignition on. Isolates the SB when ignition off to ensure it doesn't get drained when camping.

I preferred to know exactly what's going on rather than trust a VSR. But I'm probably paranoid.

[mikeonb4c]

We went for a simple but effective Lucas 30A split charge relay. Connects both batteries with ignition on. Isolates the SB when ignition off to ensure it doesn't get drained when camping.

I preferred to know exactly what's going on rather than trust a VSR. But I'm probably paranoid.

Sounds good. Only problem I had when I had 30amp fuses (but it was battery to battery VSR) was on one occasion when LB deeply discharged it blew the fuse when drawing current and didnt realise so drove around with it flat which killed it. The replacement (Willinton) VSR kit is i think 65amp and has never nlown a fuse. And I have a panel voltmeter coming off the LB so I can confirm charging voltage is getting to it.

[g8dhe]

Something which tends to get forgotten about with Ignition switched v VSR switching is that the VSR only switches when the voltage has risen above the float voltage of 13.6v approx hence the initial charging current is much higher than in the case of the ignition switched setup when the SB and LB are connected prior to the alternator starting to generate so the the highest voltage will only be 12.6volts which means much less surge current, hence both relay and fuses don't need to be as highly rated. With Ignition switching 40Amp rating is quite adequate whilst with VSR switching 80-100Amp switching is quite common, hence one of the reason I prefer Ignition switching to VSR. The other reason is as stated before I have control, and can choose to let the batteries parallel up and let the EHU or Solar charge both batteries simply by switching the Ignition on but not starting the engine.

[mikeonb4c]

Something which tends to get forgotten about with Ignition switched v VSR switching is that the VSR only switches when the voltage has risen above the float voltage of 13.6v approx hence the initial charging current is much higher than in the case of the ignition switched setup when the SB and LB are connected prior to the alternator starting to generate so the the highest voltage will only be 12.6volts which means much less surge current, hence both relay and fuses don't need to be as highly rated. With Ignition switching 40Amp rating is quite adequate whilst with VSR switching 80-100Amp switching is quite common, hence one of the reason I prefer Ignition switching to VSR. The other reason is as stated before I have control, and can choose to let the batteries parallel up and let the EHU or Solar charge both batteries simply by switching the Ignition on but not starting the engine.

Its interesting trying to understand how the VSR option got going considering ignition switching sounds so much more robust a solution. Ehen I was looking to git an LB 13 years ago the talk /advice was all of VSRs. In fairness to VSRs I seem to recall being able to adjust a pot to alter the switchover voltage. Also, now i have solar charging, the days of deeply discharged LBs are hopefully all but behind me.

[g8dhe]

The VSR setup's became popular from the installation point of view, you didn't need to run the extra wire and tap into the ignition switch/fuse block also its not as easy to do in modern cars where there is more computer controlled activity, so there the VSR saves a lot of effort, also if you don't have the manuals for a vehicle to show where to get the IG2 circuit or equivalent then again the VSR solves the problem from an installers point of view ...

[mikeonb4c]

The VSR setup's became popular from the installation point of view, you didn't need to run the extra wire and tap into the ignition switch/fuse block also its not as easy to do in modern cars where there is more computer controlled activity, so there the VSR saves a lot of effort, also if you don't have the manuals for a vehicle to show where to get the IG2 circuit or equivalent then again the VSR solves the problem from an installers point of view ...

Thanks Geoff - great explanation as always from you!