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?

 

[Gueyog8a7]

tl;dr at bottom.

Ok, so I let this slide and went to start the van this morning and flat.

Would any only jumper cables work, just stock ones? My battery is 80a I think and 1.8 litre so just buy for those specs? Might even be some old ones in the garage already. Then could I chop the one end of croc clips off and plug to load terminals of solar charge controller and charge away?

I frankly prefer the simplest solutions. These power packs sound like more bells and whistles than I want - power pack and such.

Would these be right?

Just seen this video where he connected the panel directly to the battery, so would using the load terminal be the same/better? As it would be using the load section rather than battery then it would not be set for a specific battery as it would in the case of battery connectors would it? So how would it (if at all) regulate the current flow to the starter battery and does it matter if it is unregulated?

Hmm I don't seem to see any voltage control settings for the load circuit in the manual. Unless I am missing it? Fuses are to stop amps right? So is there an equivalent cheap failsafe to prevent over voltage of the starter battery from the load circuit of the solar charge controller? Is this where a pwm would be a good choice? Cheaper than SCCs and fine for this simple task? I recall they can be like 15 pounds or so.

Ah I see that there are warnings that not using a charge controller will cause the battery to gas and possibly explode. Would the load terminals prevent this on the tracer bn, thus regulating the voltage to stay within safe levels? I never used it so not sure if there are settings. Will have to see if the manual says anything.

Also what type of connectors could I get to easy connect/disconnect the wires to the solar charge controller? For the other connections I just screwed the bare wires down as they stay in place but would want to easily connect and disconnect in this case. Adding more bits though I have to wonder whether the price will be as much/more than getting a £50 usb booster.

I guess I could skip that as I would be keeping a close eye on it and the guy in the video above says it only needs a couple of minutes to give enough charge to start the engine which is all I want.

I am confused now. If I want to make the wire myself how do I know how much current amps/watts the battery will draw from the leisure battery? I read up more about load terminals and saw that they are using the battery anyway but just via the solar charge controller. With other appliances on the fuse block we know how much they will draw because it says on them amps. So how to find out the same for how much a charger would take to charge the starter battery? It isn't the starter battery's ah is it? I read some of the mains chargers only use a couple of amps from what I recall but I don't know how I would make an equivalent device rigged direct to fuse block? Does it need some regulator in between leisure and starter batteries?

Would something like this be what I want to give a constant low current to the starter? Then with that lower current I could also just use smaller, and thus cheaper, wire from the device to the starter battery. So it would take a constant current and then I can fuse normally on the fuse block. Does that sound like it would work? Would 1.5a be enough power to allow it to turn over the battery after a while? This charger from halfords in ony 1a so seems like that current regulator could do the trick? Seems those big wall plugs do the same thing of just regulating power.

 

[NC_hydro]

I would almost pay money to watch this play out in person

 

[MakeMePower]

I would almost pay money to watch this play out in person

never saw someone trying to make something so "simple" so complicated.

 

[pollenface]

I use a standard voltage sensing relay connected in reverse.

When leisure battery is above 13.3v (solar charging) it engages the cranking battery. When below 12.8v it disengages.

Everyday both batteries are fully charged.

 

[Gueyog8a7]

I use a standard voltage sensing relay connected in reverse.

When leisure battery is above 13.3v (solar charging) it engages the cranking battery. When below 12.8v it disengages.

Everyday both batteries are fully charged.

Thanks.

For the way I suggest is there any way it would cause problems? Not connected directly as I suggested earlier, but rather using a couple of amp constant current regulator and attaching to fuse block with couple amp fuse then clipping to the battery. Can the battery somehow force current the other way and risk damaging the rest of the system or would that not happen? I ask because people usually say that the amp draw is dependent on the device and so if that is a starter battery could that not cause a massive surge which could travel back up the system or no?

I am thinking that the constant current regulator might be just an amp or two but is there anything that would cause the starter battery to overload the circuit or not? It would be fused on fuse block so I guess that would stop it there but otherwise would there be any likely event that it may happen or not?

Just wondering if there is anything else going on in those wall plugs trickle chargers or not.

I have already done the same for my laptop and mobile phone, replacing ac charger and rather having them plugged right to the fuse block but I wondered if there are any other considerations for this since it will be a starter battery that I am wanting to charge.

 

[Chispas]

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.

mate, youre spoiling the ship for a ha'p'orth of tar. I was DC only for a few years but then bought a cheap modified sine wave inverter & it was the right move, no messing with cables or melted cigarette lighter plugs. Then just plug in a trickle charger & forget about it .
I have one of these its more than 15 years old, still in use every summer in the yurt, charges phones & laptops no problem . Sterling Power have been around a long time & have a solid reputation in the Marine world.

 

[Gueyog8a7]

mate, youre spoiling the ship for a ha'p'orth of tar. I was DC only for a few years but then bought a cheap modified sine wave inverter & it was the right move, no messing with cables or melted cigarette lighter plugs. Then just plug in a trickle charger & forget about it .
I have one of these its more than 15 years old, still in use every summer in the yurt, charges phones & laptops no problem . Sterling Power have been around a long time & have a solid reputation in the Marine world.

Some people like tinkering to find their own solutions. It is not about the money.

I am very happy with the laptop and phone that are connected directly to the fuse block. I am glad I didn't just 'give in' in those cases and take the easy option.

 

[Hedges]

I bought a couple of these:

TE Connectivity EV200AAANA 500a 0-900vdc Tyco 12/24v

These were recovered from EV battery modules. These are VERY EXPENSIVE online. If you have any project that needs a high current relay this is your chance to save some money. Make a cheap 30a BMS into a 500a BMS. This will work for batteries in the 9-36v range so perfect for Lifepo4 and Lithium...

batteryhookup.com

I have a DIY battery.
Plan to connect two contactors directly to cell terminals, bypassing BMS.
Push a button on the dash to parallel 228 Ah 12V LiFePO4 with starting battery if a jump is needed.
Battery is rated for 684A, 10 seconds.

 

[Gueyog8a7]

I bought a couple of these:

TE Connectivity EV200AAANA 500a 0-900vdc Tyco 12/24v

These were recovered from EV battery modules. These are VERY EXPENSIVE online. If you have any project that needs a high current relay this is your chance to save some money. Make a cheap 30a BMS into a 500a BMS. This will work for batteries in the 9-36v range so perfect for Lifepo4 and Lithium...

batteryhookup.com

I have a DIY battery.
Plan to connect two contactors directly to cell terminals, bypassing BMS.
Push a button on the dash to parallel 228 Ah 12V LiFePO4 with starting battery if a jump is needed.
Battery is rated for 684A, 10 seconds.

Can you answer my qustion from #21? Should it not pose any risks to just run an amp (how many is safe, more = better? I just want enough to turn the engine over so the alternator can then take over) or so constant current to the battery from the fuse block? As in the battery would not somehow charge back up the other way or other unforeseen thing I had not thought of?