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Split Charge Systems and batteries

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Bob696:
the winch on the 110 is wired to the 2nd battrey. The split charge relay has a cut out switch so if I need engin power and the winch I can isolate the aux battery saving the alternator and relay.

Bulli:
I know what you are saying but then you are relying on an unsupported(no alternator or 2nd battery)battery to run your winch. The voltage will drop like a stone and thats when the increased ampage can damage BOTH your battery and your winch.
What kind of extras are you running that require a battery all to themselves? If you go on long camping trips and dont want to flatten your main battery i can see the point but for winching the system doesnt make that much sense. Plus its way more expensive than connecting the 2 batteries.

SimonR:
Although connecting two batteries in parallel seems a good idea - it is only a good idea with two accuratly matched batteries.

What tends to happen on un-matched batteries is they charge / discharge at slightly different rates.  This leads to an imbalance in the voltages after you have stopped charging /  discharging.  The battery with the higher voltage pumps charge into the other one.  It over-shoots a bit leading to charge being pumped the oher way.  The other battery over-shots and so the process continues.  Over a period of time, both batteries discharge to the point damage occurs.

The next simplest solution is just a heavy relay / solenoid which connects the batteries together while the alternator is charging.

A stalled 8274 draws about 170A between the batteries across the split charge relay.  Thus a relay capable of carrying 200 or so amps is sufficient.

Most of the people running a split charge in competitions use this setup.  It is not affected by water and you can fix it with a hammer (well, nearly!).  Neither applies to a computerised charge control system.

You can of course spend a few hundred quid extra on something with an anodised box and a blue LED - but personally, I go with the relay!

Si

Bob696:

--- Quote ---What kind of extras are you running that require a battery all to themselves?
--- End quote ---


Fridge, cdplayer, interior lights, dvd player CB and a few other things that are required when stationary (its a camper van conversion)


--- Quote ---Plus its way more expensive than connecting the 2 batteries
--- End quote ---

My heavy duty relay, all the wire and connectors cost me under £20

Bulli:
You will have to let me know where you got the cable from i paid 25 quid for one length of winch cabling!I looked at doing exactly the same as you and even have the relay sat in my garage.I spoke to Richard at scorpion who does a lot of extreme events and he recommended linking the 2 batteries. My winch has been the difference between staying put (forever seemingly) and getting home so I just dont want to compromise it for anything.
 I run all the same stuff but i switch my fridge to lpg as it if far more efficient than whilst on 12 volt.Too effiecient ....the first time i used it on gas it froze the milk and eggs solid by morning!

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