Anyone done this?

Lord Lucan

Full Member
How would you install a switch to use leisure battery as starter if vehicle starter battery has discharged? and you have a split charge relay fitted?

Thanks.

Btw, I tried to access resourses but couldn't open anything.
 

Squiffy

Full Member
How would you install a switch to use leisure battery as starter if vehicle starter battery has discharged? and you have a split charge relay fitted?

Thanks.

Btw, I tried to access resourses but couldn't open anything.
In all honesty it's far better to make sure your cab battery is in good nick from the get go. Of course it could be done using a heavy duty dual battery switch the kind that is used in marine environments (In the main), and heavy duty high ampage cable going from hab battery through the switch and on to the cab battery, but you would have to make very sure that the hab battery was isolated by the switch from the cab battery when not in use trying to start the engine. But in my view as I said it would be better to make sure your cab battery is in good condition and never used to operate the hab electrics other than in dire emergency. Phil

P.s It would probably be cheaper and easier to purchase some heavy duty commercial grade jump leads, and I don't mean the "Toys are us type"
 
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wildebus

Full Member
How would you install a switch to use leisure battery as starter if vehicle starter battery has discharged? and you have a split charge relay fitted?

Thanks.

Btw, I tried to access resourses but couldn't open anything.
If you did want to use the Leisure Battery to start the engine, you would need a much thicker cable then usual.

What you can do, if the starter battery is gone a bit low (as opposed to discharged/flat) is use the leisure battery as a bit of an booster.
If you have a Victron Cyrix-CT Battery Combiner (a posh version of a Split Charger Relay), you can fit a simple low-current momentary switch which will turn the combiner/relay on for 30 seconds and during that time try and start the engine.
If you have a switched relay, then it depends how that is switched to if you can use it to connect the batteries together without the engine already running.
If you have a typical Voltage Sensing Relay (VSR), then you can't go through the relay but would have to fit a separate battery isolation switch.

This kind of switch connected in parallel would give you a direct connection between Leisure and Starter batteries when on, and only have a connection via the relay when off

If you are still to buy a Relay and want this functionality, the small extra cost of the Victron Cyrix is worth it for the quality and convenience of the product (it also has a 5 year warranty).
But all the above is to provide the occasional "damn, left the lights on" kind of situation resolution. If you are looking at this functionality due to an actual regular starting problem, you really want to be fixing the issue at source.
 
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trevskoda

Full Member
All yyou require is a 200ah relay some battery cable,some light cable to a switch at dashboard,this closses the relay and connects all battery up,my van has this.
if you require a wiring dia here it is.
 

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Pudsey Bear

Full Member
That looks like a heater to me Trev ;) ;)

On my build I used 25mm2 cables to permanently connect both LBs to the VB, all get charged at the same rate at the same time 3 x 125ah.
 

trevskoda

Full Member
That looks like a heater to me Trev ;) ;)

On my build I used 25mm2 cables to permanently connect both LBs to the VB, all get charged at the same rate at the same time 3 x 125ah.
Nop simple ,one relay one switch two heavy battery cables from each side of switch to the batterys,relay is earthed with thine auto wire and same up to switch and back to les batt.
That looks like a heater to me Trev ;) ;)

On my build I used 25mm2 cables to permanently connect both LBs to the VB, all get charged at the same rate at the same time 3 x 125ah.
So you van will pull down starter battery leaving you stranded,the switch disconnects them and connect to charge all from alt if you like.
 

Greggbear67

Full Member
My leisure batteries are under my bed at the rear of my bus(2x110ah) The bus had a chair lift & when I took it out I retained the big thick battery leads that fed it to charge them. Now all 3 batteries are linked with thick cable, I have bought a heavy duty isolator switch, the type fitted to most competition vehicles. This will be fitted in line to the positive cable that goes back to the leisure batteries. If it is switched off the leisure batteries will be isolated & won't pull the starter battery down. If I switch it on, the alternator will charge all 3 batteries at once, but also while on the leisure batteries will also provide slave power to the main battery. All batteries are protected with 80amp fuses. As long as I remember to switch the isolator on/ off at the right times I see no issues & the system should work ok. Other advantage is my solar setup when fitted should keep all 3 batteries topped up between trips....
 

Lord Lucan

Full Member
My leisure batteries are under my bed at the rear of my bus(2x110ah) The bus had a chair lift & when I took it out I retained the big thick battery leads that fed it to charge them. Now all 3 batteries are linked with thick cable, I have bought a heavy duty isolator switch, the type fitted to most competition vehicles. This will be fitted in line to the positive cable that goes back to the leisure batteries. If it is switched off the leisure batteries will be isolated & won't pull the starter battery down. If I switch it on, the alternator will charge all 3 batteries at once, but also while on the leisure batteries will also provide slave power to the main battery. All batteries are protected with 80amp fuses. As long as I remember to switch the isolator on/ off at the right times I see no issues & the system should work ok. Other advantage is my solar setup when fitted should keep all 3 batteries topped up between trips....
This looks such a simple and much cheaper option.

Anyone see any issues with this design?
 

Squiffy

Full Member
Just one point is that if you are protecting the liesure battery with an 80amp fuse to the starter battery, if the starter battery is flat for whatever reason on starting the engine the starter is likely to be drawing in excess of 250amps and will blow your 80amp fuse, if that's how you are suggesting it is set up. What are the 80 amp fuses connected to ? Phil
 

trevskoda

Full Member
This looks such a simple and much cheaper option.

Anyone see any issues with this design?
Problem is you have to run back and switch over,better to have a dash swith going to a relay or red signal wire at altanator switching automaticly the relay over,then use the man dash switch to connect all up if a starter battery fails.
 

wildebus

Full Member
This looks such a simple and much cheaper option.

Anyone see any issues with this design?
Problem is you have to run back and switch over,better to have a dash swith going to a relay or red signal wire at altanator switching automaticly the relay over,then use the man dash switch to connect all up if a starter battery fails.
I would agree with Trev on the above to have some kind of automated switch by the dash if you want to have a semi-permanent connection.

I don't actually think having a setup that relies on manually connecting the batteries together (be it a mechanical switch you turn OR a remote switch you manually push) is the best way to go either, but it is an option and it generally works (but there are definately downsides that can catch you out - squiffy in a post above touches on that)
 

Greggbear67

Full Member
Just one point is that if you are protecting the liesure battery with an 80amp fuse to the starter battery, if the starter battery is flat for whatever reason on starting the engine the starter is likely to be drawing in excess of 250amps and will blow your 80amp fuse, if that's how you are suggesting it is set up. What are the 80 amp fuses connected to ? Phil
80amp fuses are connected in line to the positive wire from the starter battery just before it reaches the leisure batteries. I believe there is also one under the bonnet but I didn't fit that one.
 

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