Don't like the adverts?  Click here to remove them

Split charging system and winches


Well-Known Member
Apr 16, 2010
Country Flag
doing some research on split charging systems:


1) My LWB landcrusier 90 FX only has one battery, and only has wiring for one battery. even though it has aircon etc, but no rear heater or heated seats etc. So i have space for a 2nd battery in the engine compartment. just need to fit a base-plate and fab-up some battery hold-down brackets.
2) I will be shortly be fitting a winch, and a 500w inverter, so would be good to have extra juice for the winch, and also be able to run the 2nd battery to the inverter etc
3) mines an auto, so would be good to have second battery as backup if the primary fails or is flat

Two options I see are:

1) get this kit or DIY similar: ... 120a-model (£100)
2) get an IBS system like Chris has/had in lil blue. But these are now £178 e.g. tbruk.... even with a 10% discount, a big outlay

Big question is: if you have a winch wired to the main battery, and operating the winch with the engine running, how do these two systems cope. I suspect with the current draw on a winch, the "rawcomponents" (option 1 above) might fail - blow the 80A fuse? as the winch would end up trying to pull current from both batteries, as the relay would be live with the engine running.
And how does the 200A solenoid on the IBS system cope with the winch drawing power ?
AndyCook said:
and also found this kit:
any opinions on this too? appreciated

Hi Andy,

There is a lot of systems out there but as you have found very expensive, but I would use: ... l?cPath=80

or something like that, and connect the two +ve's together but put the relay in line, and connect
to the Alternator as in a split relay, but put a switch so you can switch it off.

So under normal conditions when you start the car up and the engine is running it charges both batteries,
but if you want to winch with the engine running and not connected together just switch off and the winch
will run from the Aux Battery and then when you switch on it will charge the Aux battery.

One point though, make sure the cable is thick enough between the two batteries, you need something like

Hope that helps, any questions please reply, or send PM

Hi Andy

I raised a few questions on the thread one below yours


but I haven't done anything on it yet much less even got my head round it... However, Jon Wildsmith's contribution is worth a read if you haven't already.

Sorry not to be of more assistance at this stage...

Pretty much covered in all that lot, but as I had the set up that you described.... It worked perfectly. You could winch off the main battery, or connect both batteries if you wanted, either running the engine or not. And, if you flattened the main battery, press the connect button and it would fire up off aux no problem. I think there are cheaper ways of doing it, but the IBS was neat and worked, plus it had flashy lights so there. Nothing you couldn't do with some wire, a relay and a toggle switch if you didn't want lights.
As I had a little, well err, problem in Wales when I couldn't run the engine, having plenty battery power to recover myself using the winch, taught me to never be without plenty of back up juice.

must admit - i do like those flashy lights!
Don't like the adverts?  Click here to remove them
If you want a split charge system that actually performs better than your alternator you could do worse than a sterling B2B charger and a big switch - boosted voltage 4 stage charging (for whatever battery type you use) plus with a big battery cut off switch (plus 50cm of heavy cable and a couple of lugs) you can then flick a switch and winch off both the cranking and aux batteries. Oh and it is tough enough... It WILL charge your batteries faster and fuller than any voltage sensing relay type arrangement. As far as split charging goes I believe Sterling have been well respected for years by caravan/boat types - no 4x4 marketing, but hey why reinvent the wheel.
Hi,After spending some time studying split charge systems and other various options, I have to agree with the above post Sterling was the winner for me, it was very capable of doing the job & good value for money.
I like the look of that but at £300 - I think I may need to go with something cheaper. It's certainly a neat piece of kit and if I was crossing the globe, then £300 would be in the budget. But for running a fridge a couple of times a year on a family picnic, it's more than I need I think. I shall go with a voltage sensing relay and some cable. I can always put the LB on charge at home occasionally if it needs it.

would that sterling diode need to be wired in before the passenger battery and then take cables to the LB and main battery as its 1 in 2 out? also will it let you draw power for the LB when winching?
Hmm. I seem to be going around in circles. I don't need extra winching power on this system. I shall go for winch on main battery and have the engine running. OK, if I roll it and hydraulic the engine I will only have the one shot, but let's not go there. I just want a leisure battery for bits and bobs, including running the compressor and inverter. It can't be a trickle charger off a caravan as that will not replace the charge fast enough if I use the inverter for something heavy like an angle grinder which will be a very occasional situation. Mostly it will be running a phone charger or something daft.

I certainly want it to be man enough for the currents involved but I only need one way flow. I shall connect the LB via an Anderson connector so that it can be removed and coupled to something like my flying jump lead set if I needed to give myself a jump start sometime. That diode system from Sterling looks good and at £65 is is reasonable. I may have to wait til Lincomb and see what people have put in their vehicles to fully appreciate the possibilities.

Good thread though, please keep it going. Jon's posting on the subject was extremely helpful and well worth the the time he spent typing it. Thanks Jon.

those sterling battery to battery chargers are also quite big, much larger than a voltage sensing relay and are not water resistant so cant be mounted under the bonnet. they also need ventilation which restricts where you can mount it even further. otherwise they look like a really good product, if only they were cheaper... are there any other options when it comes to clever multistage split chargers?

EDIT: sorry it turns out that they do do a waterproof one: BB121240W, but cant seem to find them anywhere that sells them online...
These are the ones fitted in the Virgin mobile vans that were used with the inverters i had for sale.
The guy who fits them says they are the bast and you can put an over ride on them for start assist.
They normally retail at about £50 ... 160a-400a/

Same make as the huge gel batteries that they use too.
The same batteries you going to sell us Paul? ;)
Now you can add the split systems to the list. Ahh hell, just sell us a van each please.
I think I is going to make me an offer on that.

Me likey. Looks heavy duty. Well over engineered to keep Jon happy. :lol:

I'm told you would have to taylor the size to your requirements, but the make is highly recommended by someone who is in the know.
Be aware that the larger amperage ones are quite big units in size and weight.