How to make jumper cables from lifepo4 leisure battery to van battery for if it runs flat while off-grid?

[Gueyog8a7]

Is it just a simple case of getting long enough wires from the battery in the back to the engine and maybe a fuse? Having said that I imagine the thickness of the wire required would mean that length would cost a lot if you have to get over the amperage of the batteries? 80a for the engine battery and 100a for the lifepo4 leisure. Or does it not work like that?

Not sure how it would work so asking here!

The battery went flat several times last winter but had been at my mum's with shore hookup.

I am wondering how I could charge the battery from leisure/solar in the back once I will not have access to the above.

Think it will be an important capability as I won't know anyone where I will be going and so want to keep the van in running order.

I know there are split chargers some of which will use solar to charge the van engine battery but that seems way overkill just to use for this purpose as I found I had no reason to buy the split charger even through winter as solar got me through. Only just but that was only a few weeks in the very shortest days then fine into January so don't see that as justified and would be a waste of money.

As such how would I do it with the leisure battery directly? If the thickness of the wires would be expensive I could rather just unscrew the battery from the back and take it round to the front myself. A cumbersome task however I would hope to avoid running the battery down totally in the first place so would be aiming to do as little as possible.

 

[mikefitz]

battery went flat several times

Get a new starter battery is the first step.
Buy and install to maintain the starter battery,

Votronic 3065 Battery Master - Standby-charger 12V

<p>This Votronic charger is a great way to trickle charge your engine battery in a motorhome, Installed between the starter battery and the leisure...

www.roadpro.co.uk

Or a more advanced unit,

Ablemail AMT12-2 Battery Maintainer

<p>The AMT12-2 Trickle Charger has been designed to keep a vehicle’s starter battery charged and protected from damage during prolonged perio...

www.roadpro.co.uk

( note you will need the house battery negative connected to van metal for the negative path).

Use jump leads in an emergency to transfer some charge to the starter battery, disconnect before attempting to start, as the current limit on your lithium to too low to supply starter current.

 

[Gueyog8a7]

Get a new starter battery is the first step.
Buy and install to maintain the starter battery,

Votronic 3065 Battery Master - Standby-charger 12V

<p>This Votronic charger is a great way to trickle charge your engine battery in a motorhome, Installed between the starter battery and the leisure...

www.roadpro.co.uk

Or a more advanced unit,

Ablemail AMT12-2 Battery Maintainer

<p>The AMT12-2 Trickle Charger has been designed to keep a vehicle’s starter battery charged and protected from damage during prolonged perio...

www.roadpro.co.uk

( note you will need the house battery negative connected to van metal for the negative path).

Use jump leads in an emergency to transfer some charge to the starter battery, disconnect before attempting to start, as the current limit on your lithium to too low to supply starter current.

Hi again, and thanks.

So jumper leads are a 3rd option?

I want the cheapest option since I would not plan to have to do it often.

£40 is pretty reasonable for that votronic but still, having to install something, seems overboard for this if there is a simpler solution.

So jumpers could be used just like you would do normally from vehicle to vehicle, just with leisure battery instead?

What do you mean by the last sentence please? Did not understand? What does the last paragraph mean? What does the leisure battery current have to do with starting the engine battery?

 

[MisterB1959]

Vanbitz battery master will ensure your vehicle battery is topped up via your hab battery, so long as your hab battery is getting charged. They are in the UK .....

 

[mikefitz]

What does the last paragraph mean? What does the leisure battery current have to do with starting the engine battery?

If you jump the lithium to the starter battery , don't try to start with the lithium connected, it cannot deliver the starting current. The idea is to 'boost' the starter battery by having the jump leads connected for several minutes. If the starter battery is in poor condition, and after a number of 'flat' battery situations, it will be. Then the starter battery may be past help.
Do your self a favour and get a replacement starter battery. Fit a maintainer or drive the van for a few hours every week.

 

[Gueyog8a7]

If you jump the lithium to the starter battery , don't try to start with the lithium connected, it cannot deliver the starting current. The idea is to 'boost' the starter battery by having the jump leads connected for several minutes. If the starter battery is in poor condition, and after a number of 'flat' battery situations, it will be. Then the starter battery may be past help.
Do your self a favour and get a replacement starter battery. Fit a maintainer or drive the van for a few hours every week.

What would happen though? Why does it being connected affect if engine battery starts or not since engine battery should start itself shouldn't it? Not that it is too hard to take it off before just wondering what happens if not.

Of course I would aim for keeping enough charge and would be doing weekly shops mostly which will be several miles there and back. I noticed when I was taking longer day drives it has not run down completely since the winter but I am just planning for a 'just in case' scenario.

So you did not reply to other question, is it just as simple and the same process as using jump cables as you would from vehicle to vehicle/both starter batteries? Also when you said disconnect the leisure battery first, you mean from the leisure electrical system? Do the +/- screws need to be unscrewed or just turning the solar switch and battery isolator switch off is ok? Is there no risk of damaging the leisure system or anything else?