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?

 

[Gueyog8a7]

So can anyone confirm, is this just the same process as you would do from starter battery to starter battery? Just hook the other side to the leisure battery instead?

 

[MakeMePower]

is there a reason why your not just using a portable lithium jump pack, so much easier, and can be used with other vehicles

 

[Bananaman321]

So can anyone confirm, is this just the same process as you would do from starter battery to starter battery? Just hook the other side to the leisure battery instead?

I'm not looking to get into a public debate but you've been asking the same questions for too long. Buy that book and get crackin before you up your sh*t or your self.
No pun intended.

Check out CleverSolarPower.com I'll leave a link

Homepage ‣ Clever Solar Power​

cleversolarpower.com

A good book I recommend at $17

https://www.amazon.com/Off-Grid-Sol...-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

 

[Gueyog8a7]

is there a reason why your not just using a portable lithium jump pack, so much easier, and can be used with other vehicles

Because the whole point is to rely on solar not shore power and these 'packs' need shore power from what I read.

I want to be off grid and off grid means no shore power so I want a backup for if the battery goes out while off grid.

Also no inverter and don't want one, just DC.

 

[Gueyog8a7]

Also how about using the 'load' part directly on the epever solar charge controller that no one ever uses and put it to good use , bypassing the battery altogether?

 

[MakeMePower]

Because the whole point is to rely on solar not shore power and these 'packs' need shore power from what I read.

I want to be off grid and off grid means no shore power so I want a backup for if the battery goes out while off grid.

Also no inverter and don't want one, just DC.

lithium jumps packs are portable, and do not require shore power. the unit I have is charged via micro usb.

https://amzn.to/3AhJtSV

 

[MakeMePower]

Also how about using the 'load' part directly on the epever solar charge controller that no one ever uses and put it to good use , bypassing the battery altogether?

this will also work, just make sure the load is not to high, or a relay would be needed

 

[FishHog]

Because the whole point is to rely on solar not shore power and these 'packs' need shore power from what I read.

I want to be off grid and off grid means no shore power so I want a backup for if the battery goes out while off grid.

Also no inverter and don't want one, just DC.

Well they do need to be charged. But lots of ways to do that. I charge mine at home once a year but it’s usb so if you can charge a phone in your camper you can charge it. They are the right solution and safe solution for what your looking for and are just too handy not to have one

 

[Gueyog8a7]

this will also work, just make sure the load is not to high, or a relay would be needed

what classifies as too high? The starter battery is 80a.

Can I buy some jumper cables and just cut off the crocodile clips on one end and plug direct to the SCC? How does the SCC regulate how much goes to the battery? I would actually prefer this way than to use the lifepo4 battery 1 because the SCC is cheaper than a replacement battery and 2 that load output is spare while the battery terminals are loaded up already with other connections.

I also just got a reply from fogstar as I asked them if I could use it to charge the starter and they advised against it as it could damage the BMS they said.

 

[Gueyog8a7]

Well they do need to be charged. But lots of ways to do that. I charge mine at home once a year but it’s usb so if you can charge a phone in your camper you can charge it. They are the right solution and safe solution for what your looking for and are just too handy not to have one

Oh well it they can charge from usb that is great because I have two ports connected to the leisure battery yes.

Will just be a case of price then whether jumpers or one of these packs will be cheaper.

Actually there would be added satisfaction of rigging jump cables to the SCC if it would work.

These metal epevers have really wide ports to accept thick cables so should fit nicely. So it is just plug n play? I don't want to use them all the time so how could I set it up? I don't want to have to go down the back behind my bed to plug them in when I would want to use them. Also if plugged in all the time it would cause a short wouldn't it if the crocodile ends touched. Would that blow the scc? Should I fuse on the wires?

Maybe cut the wire somewhere along it so I can plug and unplug the ends? Not sure the best way?