Can starter battery be charged from leisure battery?

[Transit-man-van]

I flattened the battery again due to all my electric window usage earlier in the week while trying to fix it. Didn't occur to me at all at the time. Only once I came to start it this morning and flat and suddenly twigged that would have been the obvious cause.

It is so easy to flatten the battery if not driving daily. I know some people say "just buy a new battery" and while I am sure a new one would hold more than this one which is probably over 10 years old I have read enough online to indicate this can happen easily no matter the battery condition. I am wondering if there is a way to charge it using my solar/leisure battery setup. It doesn't happen often enough that warrants paying 100-200 quid for one of those split chargers which keeps the starter trickle charged.

It does happen often enough that I would like a back up when I don't have access to shore power. Also I don't want to rely on shore power either - so not interested in those 'power packs'. I would like to harness the solar I already have on the van.

Can I simply run jumper cables from the leisure battery to the starter? Would they have to be large gauge? If so that would be pricey due to the length required to reach from inside the van living space out to the engine. Probably would cost over 100 quid for that at which point reaching similar prices for those split chargers.

The wallplugged charger only has really thin wires though so why is it they don't need thick ones like the thick gauge ones recommended for leisure battery main circuits?

[metalworker0]

A solar panel as a charger requires a bit of electronics to make sure battery is not overcharged and MANAGED..it could cook it , boil it, reduce the life of it, if not so.

This is not expensive either

https://www.ebay.co.uk/itm/326045268232?

if you directly coupled a leisure battery to a flat car battery initially it would require thick leads. as thick as jump leads or they would get hot until the power equalised in both batteries ...a flat battery connected to a charged leisure would equalise and you would end up with both half charged and not at full capacity ..unless the solar panels were connected to the leisure via the device I've linked to.

A new battery is not necessarily £100 plus ...i got a brand new shop soiled one from Tayna (just happens to be local to me) for £30 this year.

I would go on to say that, the way you are using the van (sleeping in it ,using the lights etc) probably would finish off a battery sooner than if used normally.
so a battery at 10 years old its probably finished and at the end of life,, which is probably why you are experiencing trouble.

A battery "drop test" can be carried out by any battery retailer for free ..they will then give you an estimate of the batteries capacity, as a percentage figure ..i replaced mine when it was showing only 75 percent fully charged.

Note; driving around with a poorly performing battery will place more load on the alternator ..and lead to early failure/ shorter lifespan of the alternator.

all the best.mark

[Transit-man-van]

A solar panel as a charger requires a bit of electronics to make sure battery is not overcharged and MANAGED..it could cook it , boil it, reduce the life of it, if not so.



all the best.mark

Thanks, yea I had noticed they are as cheap as like 30 quid on halfords. I read people still have issues even with new ones though especially if living in the van as you say, so not too motivated to do that as the first port of call since it seems to last ok so long as I am not using the electric in big bursts.

Ain't broke don't fix it. If it gets worse I would certainly move it up the priority list but since it is ok atm I would just like to know I had a backup in some solar setup.

Yes they might end up both half charged but I have solar so it would just top up the leisure wouldn't it so what is the problem?

I also asked on a camper forum and one member said they were able to successfully do it with just normal jumper cables, though don't know what they were rated at. I too was thinking they would need to be rated to the load of the starter battery at least wouldn't they? Or is it the leisure battery at 105a? I think it will get pricy for that but if it works it will be a nice to have. if paying over a hundred quid or so for that length of lead (going on memory as I think the thick gauge for leisure cost me something like 15-20 per meter, it would make more sense to get a device of similar price made for the job.

Oh I am seeing that jumper cables are only a few quid 10-40 https://www.partsinmotion.co.uk/car-par ... jump-leads and say rated to 100a+.

Should I add a fuse on the connection somewhere or no need? Also could it damage my leisure circuits if I don't disconnect them before connecting the starter? That is where a fuse would be handy right? To protect them or would the circuit not interfere with the fuse block items connected to the leisure battery?

Could I rather hook some wires direct to the solar charge controller, bypassing the leisure battery entirely as for my SCC there is a separate + - for 'load' which allows you to add something direct to it. Most people of the SCC think it redundant as why do that rather than use the fuseblock in most cases but this could be a good use for it maybe?

[metalworker0]

No need for fuse - do you ever frequent car boot sales ..because you'll get a set of jumpers there for a fiver or less .

just remember this though

There are a lot of fake ones made by the Chinese , they look like huge heavy duty cables --- they are not, they contain steel wires with copper plating on them and you'll have trouble starting a motorbike with them ...so carry magnet with you and see if the cables are magnetic, if they are, then don't buy.

The jumper will only carry the high amps for a couple of mins or less, before the batteries equalise.

The rest of the information is best read up on in the camper forums, as they have more experience than me .


all the best.mark

[Transit-man-van]

No need for fuse - do you ever frequent car boot sales ..because you'll get a set of jumpers there for a fiver or less .

just remember this though

There are a lot of fake ones made by the Chinese , they look like huge heavy duty cables --- they are not, they contain steel wires with copper plating on them and you'll have trouble starting a motorbike with them ...so carry magnet with you and see if the cables are magnetic, if they are, then don't buy.

The jumper will only carry the high amps for a couple of mins or less, before the batteries equalise.

The rest of the information is best read up on in the camper forums, as they have more experience than me .


all the best.mark

No, I never go to car boots. Also live in the country so mail order the best bet.

You mean the charge would go to 50% in that short of a time? Why no need to fuse?

So is it just normal jumper cables I am looking for and what amps? Up to the amps of the leisure battery?

I wouldn't be so sure about camper forums having more in depth knowledge. Majority are not keen on getting their hands dirty. The one response I got of the person who had done it successfully was more the exception. Most seem to prefer the hands off approach and get 'devices' that do the work for them. I prefer getting stuck in and doing DIY solutions when I can only resorting to an engineered option if I am unable to do a DIY jobby.

[metalworker0]

Well all these vans are custom fitted with the solar equipment, not ford equipment, each system is going to unique to the owner, its the camper van owners who do it , talk about it etc, not much talk here.

Jump leads are made to carry the amps for short periods of time ..and to start car ..its safe, don't need fuse ..you don't know how many amps are flowing.so therefore you don't know what fuse to put in ..you could do experiments with a clip on ammeter
....its going to be i imagine something like this:- depending on the resistance of the leads and the size of the leisure battery - state of battery charge:-
-..first 5 seconds 100 amps ./.next 5 seconds 95 amps , gradual decreasing until batteries are equal ,..i don't know the science of it , there will be someone who does ..they are not here...no out and out boffins here.

Once they are equal the load will be dependent on what you take out of it, the input will dependent on what you feed into it

a 200 watt solar panel is only capable of making so:-
200W/12V = 16.67 amps.

The battery left permanently connected to the other has to have heavy duty cable
similar to this ..so buy two of these ..one black one red

https://www.halfords.com/motoring/batte ... 65308.html?

or you could put a post in the mk7 forum asking how the duel battery set up works

all the best.mark

[Transit-man-van]

Well all these vans are custom fitted with the solar equipment, not ford equipment, each system is going to unique to the owner, its the camper van owners who do it , talk about it etc, not much talk here.

Oh, I see what you mean. I thought you meant the general electrics besides that, after it leaves the solar.

Jump leads are made to carry the amps for short periods of time ..and to start car ..its safe, don't need fuse ..you don't know how many amps are flowing.so therefore you don't know what fuse to put in ..you could do experiments with a clip on ammeter
....its going to be i imagine something like this:- depending on the resistance of the leads and the size of the leisure battery - state of battery charge:-
-..first 5 seconds 100 amps ./.next 5 seconds 95 amps , gradual decreasing until batteries are equal ,..i don't know the science of it , there will be someone who does ..they are not here...no out and out boffins here.

Once they are equal the load will be dependent on what you take out of it, the input will dependent on what you feed into it

a 200 watt solar panel is only capable of making so:-
200W/12V = 16.67 amps.

The battery left permanently connected to the other has to have heavy duty cable
similar to this ..so buy two of these ..one black one red

https://www.halfords.com/motoring/batte ... 65308.html?

or you could put a post in the mk7 forum asking how the duel battery set up works

all the best.mark

So even if the amps burst high at some points, it should not go above the maximum amps of the starter battery?

If so it sounds like the same general theory of sizing wire and fuses for any other leisure battery circuit.

Thanks for the comments.

[bortaf]

you can fit a battery master
https://www.ebay.co.uk/itm/116221574892 ... R5Tj_eGpZA

or change to a combined solar BtoB ? like the renogy DCC50s or redarc but they are over £300
you could fit a small 20W pannel and controler for about £40 ?
you could also just fit a split charge relay and wire it backwards so to speak, but then you'd need cables ect, cheapest would be a small solar pannel if you have room for a small one up top ?

[Transit-man-van]

you can fit a battery master
https://www.ebay.co.uk/itm/116221574892 ... R5Tj_eGpZA

or change to a combined solar BtoB ? like the renogy DCC50s or redarc but they are over £300
you could fit a small 20W pannel and controler for about £40 ?
you could also just fit a split charge relay and wire it backwards so to speak, but then you'd need cables ect, cheapest would be a small solar pannel if you have room for a small one up top ?

These all require more parts though. The point it to harness what I have already.

Split charger as I said is a waste of money. I only want the ability to recharge on the exceptional occasion when it runs flat so no need to pay hundreds for that.

That is why a couple of jump leads seems a good solution if it will work.

[bortaf]

Every time you flatten that starter battery you damage it, damage it enough times it's dead and you need a new battery, it's cheaper to fit a trickle charger of some sort than replace tha starter battery my batterys have been in 5 years and they still sit at 12.9 over night cos i charge them every day using the house (spare) solar,it's allways cheaper to prevent than to repair/replace

[Altransit]

you can fit a battery master
https://www.ebay.co.uk/itm/116221574892 ... R5Tj_eGpZA

That's a nice find Rob
I have to keep swapping the leads over, on my little dashboard solar charger, to top up both batteries one at a time
That there bit of kit is the answer