Ima gonna split you in a camper van.

[Des]

Splitting charge between batteries in a shit old camper is a pain, doesn't really work. I started some years ago with an old van that had never had an auxiliary battery as there was only some tube lamps and a pump for the sink. I added a load of greedy electrics so stuck in a second lead acid lovely and swapped the alternator with an old Landrover one for double the ampres, added a thicker cable and a biggish current relay, again from an old landrover, to parallel both bats when the ignition's on and I was in business. Well not quite, regularly had to lug out the aux to give a mains charge, later fitted a matched pair of magic heavy electron buckets which helped, then stuck a solar panel on the roof, a good move as it put a stop to completely flattening a battery when I was careless, lot's better, but only when it's sunny. So I put this together to stick under the drivers seat.

 

 

Everything chargical secured to a bit of tin that I screw down, even knocked up a fruity little circuit diagram so I can figure it out in the future.

 

 

This is most of the fire hazard shit I ripped out, half of it my own doing.

 

 

So that's the solar regulator and a couple of relays back in only neatly this time and I've added a proper fuse box, an adjustable voltage sensing switch and a DC to DC transformer thing that's adjustable as well. I've nadgered it all together so that when the main battery shows about 14.2v to the voltage sensing switch, via the ign switch, it triggers the big relay that used to just join both batts + to +, but now connects via that DC to DC transformer which I've adjusted to a shade under 15v. My theory is that instead of the alternator sensing an average of both batts voltage, it's presented with one, plus load.

Proof of the pudding, ran the engine and watched both batteries charge up nicely, the sorcery yeilds. See this shitty meter, 

 

 

Those horizontal bars show capacity, I've never seen all the bars shaded like that, at best one of the top ones flashes, almost getting there but not quite, Just have to monitor it closely now, see how it behaves with one batt flat, the other, both or neither to be sure there's no overcharging or cycling relay shenanigans under unusual conditions.

Voltage drop is a cruel and mischievous adversary, If I have it beat and this lot proves reliable then it's a pretty cheap setup, hundreds can be spent on split charge systems that look a right load of old cock.

[Richard]

My work Transit has a good system. One of the batteries is disconnected when you switch the ignition off, so it can jump start itself if you flatten the other battery- as I often do.

[D Spares & Tyres]

I`ve got a battery in the boot of my shogun to operate the electric winch. Simple bit of wiring that I`ve done myself, got a thick bit of cable with an inline fuse from the main battery cable tied to the chassis then coming up through a hole I`ve drilled in the boot floor. Battery earthed to floor.

 

Simple and works fine

[Albert Ross]

I use those Smartcom Relays for my Auxiliary lighting panel. If the engine is running, I can use the high drain lighting. If not, they stay off. Great stuff, prevents them being left on.

[The Moog]

Looks great. What is the voltage booster used for? Where did you get the SMARTCOM relay from? 

 

I need to knock something up for the AMM at some point. 

[John F]

This will come in useful... thanks for uploading, Des!

[OwdChina]

The last time I was in England I noticed a mates Toyota Hilux had two batteries under the bonnet as standard. What's that all about then ?

[mat_the_cat]

/\ A mate of mine had a J reg Hilux Surf with the twin batteries, and he said it started using a 24 V starter (i.e. lower current for the same load), but everything else ran on 12 V.

 

Interesting set-up Des, I know that the charging voltage from an alternator never fills up the batteries completely so my approach was to fit a bank of 3 leisure batteries, so that I can shallow cycle them from a less than optimum charge, without spending lots of dosh on a true deep cycle battery.

 

Is there anything to limit charge current once the batteries are fully charged? That would be my only worry, that they potentially overcharge and gas/boil dry on a long run. It's *probably* going to be OK...but worth checking the levels if you can to build up confidence.

[OwdChina]

Ahh.....that would make sense, thanks Mat.

[dave21478]

....? Where did you get the SMARTCOM relay from? 

 

I need to knock something up for the AMM at some point. 

 

Dunno about Des, but I got one the same from Ebay for a few quid.

 

I just ran a thick cable through a fuse to the smart relay and then onto a second battery in the back.....just a normal car battery, not a leisure one.... to which I have connected up a few work lights and my big inverter so I can do stuff and not worry about flattening the cars battery leaving me stuck.

I know that running the second battery completely flat wont do it any favours in the long run but I had it going spare and will use it till it dies (if it ever does?) and then spend out on a better option.

[mat_the_cat]

Leisure batteries still don't like being run flat, although will cope with it slightly better than car batteries. It seems like you really have to spend a lot on 'proper' deep cycle batteries like Rolls, which then makes you think maybe it's more cost effective to just replace a cheaper battery more often...

[dave21478]

Thats exactly my thinking....yeah Ideally I would have some fancy-pants deep cycle battery but realistically I can comfortably get by with my salvaged old varta and when/if it gives up I will rummage another out the scrapyard for €20 or so.

[mat_the_cat]

When I bought mine I actually worked out that it was cheaper per Ah of usable capacity to get a few cheap leisure batteries which I ran down to say 50% charge, than run a 'better' one all the way down. Had 8 years life from the old set. Obviously the trade off is weight, but hey, it helps traction in a damp field!

[Des]

Smartcom came from Amazon Mr. Moog, and the booster is to bump up the charge to the second battery by a volt to allow for the voltage drop as it's that bit further away, it's also sort of isolating it from being all up in the alternators business. I might yet monkey with that alternator to bump its output up a shade, within reason should be fine as lead acids are quite good at self regulating, they'll gas more from a higher charge and need checking / topping up as opposed to the never ever not on your fucking life mate modern approach, this invariably involves removing stickers, hammer, screwdriver, holesaws and getting acid splashed in your eyes. Charging is a compromise, generally longest battery life will be from a charge that stops short of bubbling the cells.

All this bollocks and I bet at some point this summer I'll find myself bump starting the pile of shit ithrough some field in the no phone signal middle of buttfuck nowhere.

[Des]

I can has futuristic technologies. Digital Dash, Oh Yeah.

 

 

Little 2 wire voltmeters £1.60 a pop from amazon, mounted in a plastic dash top and a piece of stylish smoked perspex to take away the mean look, I love it, makes a nice distraction from watching the road.

I had some issues with the charging relay, after a bit of fine tuning of the smartcom cutting in point, all seemed well, but if headlamps and fridge are on the relay would cycle in tune with the indicators, wouldn't do it for the hazards or anything else, just indys, maybe there's a capacitor or something inductive in the flasher unit that does weird stuff to the electric, fuck knows, wouldn't adjust out anyway, then later it does it at certain levels of charge when just the fridge is powered, so I started noting exact circumstances in order to work out a solution said bollocks to that and ripped out the fucker of a fridge along with a bunch of wiring, gas pipes and a flue. Nothing wrong with that kind of fridge, a tiny gas flame runs them nicely when stationary but on the move the flame blows out and they take something like 20 or 30 amps on 12V, thats just greedy, so I've thrown a 12V only cooler in that shouldn't take much more than the solar provides and see how leaving it on all the time works out, one less relay simplifies the splitty charge panel and I can take the tippex to my fruity little diagram.

I SHALL be master of the volts.