..charging second/leisure battery simple way..

One of the key things for good battery life is to charge it before and after with a multistage charger this is especially important when you get back and the batteries levels down.

A split charger being a self switching or not will never charge the battery fully as the alternator is a bit of a hammer and only charges to 80 or 90 %, this efficiency also drops off each time use it.

 

I'm old school still. Split relay/charger and a numax leisure battery charger for when we're on grid or home. The fridge is three way so if we've no hook up the beers should still stay cold.

 

Old school Nick...pah.
We've got a Lucas 36amp alternator on the boat that charges the starter and 210ah leisure bank through a diode!
It's an odd collection of home assembled componentry inside the little box that's next to the batteries.
I lifted the cover once...brushed away the webs, carefully replaced it and prayed to the battery gods it never plays up.
So far so good.

 

These could be the update option.

https://en.m.wikipedia.org/wiki/Baghdad_Battery

 

I think the relay between the batteries whether voltage sensing or alternator driven will do a much better job than anything limited to 10 amps peak by the rating of a cigarette lighter socket.

It's very easy for something plugged into a cigarette lighter socket to get so hot the plastic melts and the spring pushing the centre pin out loses its temper as it approaches red heat making the connection worse and worse.

 

Campers place unusual demands on their batteries.

1. Camper is often not used for long periods

2. Camper uses considerable power while on site.

Molteni Mike's modifications.

1. Two batteries (NOT leisure ones) bought from a breakers yard for £25 each. They're huge, 70-80AH each.

2. Hardwired the +ve terminals together with heavy duty jumper lead cable. Then sent both earth cables to a heavy duty (300Amp!) "boat switch" placed in a rear cupboard. This gives a choice of OFF - batt 1 - batt2 - both. The choice of using the "earth" for this system is in case of a short circuit, the system is safe. Never ever turn the switch to OFF with the engine running, you'll fry the alternator diodes! I've never used the "both" option as charging more one than one battery in parallel results in the "better" battery only being charged to the level of the "worse" one.

3. Wired a solenoid (standard Leyland starter solenoid) so that when the starter is turning, BOTH batteries are momentarily called into action.

4. When parked in the drive, the electrics are plugged into an "Optimate" charger which safely keeps the battery charged without risk of overcharging.

Protocol when away from home.
As soon as the vehicle is parked for the night, the battery is "switched" to the other one. In this way the battery just charged by a long drive will be fresh for the following day. The one just connected can be used overnight without concern about the following morning's start.

Touch wood, this setup/protocol has worked 100% for several years.

Here's a picture of the boat switch, they're about £25 from chandlers. The Optimate charger is about £40 from various suppliers on eBay.


The traditional "split charge" system has the "overnight" camper electrics wired to the leisure battery and a relay to charge both batteries together when the alternator is turning. It's a great system when everything is working! But there's a small risk that something to do with the vehicle's electrics will be left on (sidelights, courtesy lights etc), causing the engine battery to drain on site.
Additionally, if the leisure battery is in poor condition, after a long drive the engine battery will become drained. It's possible to fit a gizmo which sends the alternator's charge to the battery with the greater need. But that is an expensive option.

But on an old vehicle, starting needs every help we can give , hence the decision to use two engine batteries which are used in tandem when cranking. In my set up, the system has controlability in that it's me who decides where the charge goes and which battery is used overnight. Actually I don't use much power on site, in the days when I had just one battery, I could remain on site for several nights and the engine would (just about) start.

For the majority of the time the camper is not used for holidays, so it can be driven without regard to charging.

I like the peace of mind which comes with knowing that the fully charged battery is completely isolated overnight from any current drain.

It's a bit of hassle to remember to switch over batteries but it soon becomes instinctive.

 

Bizzare, but if it works for you that's fine ...


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Gosh, my bus has different keys for the doors and ignition, can’t even remember them…even though they have idiot proof coloured tags