Thread: What Batteries - Dual Batteries

Originally Posted by CJT

x2

I was thinking running it off the auxilary would be better, especially if your vehicle is not running for some reason.

Wouldn't want to flatten the main cranking battery.

Can I ask what size batteries people are using?

From what I can tell the Optima's are only 55AH batteries.

My ARB 2nd battery has been using a supercharge allrounder mrv48
this is a combo 60AH / 525CCA
Fits in there nice, and lasted 5 years without any additional heat protection other than the side plate that holds it in.
Just put in an new one, , ( it runs the fridge when away)

Originally Posted by Urban Panzer

Mine is wired of the AUX batt (yellow top), had no issues to date.

I understand all your points, which is why my battery isolator is rated at 300AMP nominal and over 1200AMP cranking..........my original one would not have coped with the "possible" winch amperage draw which is why I changed it.

Once the engine is running, the winch will draw off both batteries anyway "through" your split charge unit. The one i fitted also has a "manual" switch (or remote) if you wish to connect the 2 batteries directly together....ie if the main starter battery goes down and you wish to jump start yourself...........and 2 batteries will help supply the winch far better than just one.
The TD5 has a 130AMP alternator, which should provide enough guts for winching.......well it has so far.

Would rather flatten the AUX batt using the winch than the main one.
Just my thoughts on it tho.......

I'd personally prefer the Aux battery connection too.
(BUT!) I would have thought if the winch was connected only to the main battery(and without the use of jump start override), that once the winch kicks in, the voltage drop during the winching process would(and should) stop any charge going to the Aux battery.
With Redarc, and many other common dual batt isolators, they're set for about a 12.7v kick in/out cycle .. one of the reasons I like the sound of the Drivesafe setting of 11.9v or whatever he's can be set too.
So with the winch killing the starting battery, which the alternator can't replenish at the same rate, whatever capacity the Aux has is all it has .. it won't receive any more charge from the alternator.

I'd have thought that the aux is there as the battery to be abuses, saving the main battery as the one to maintain enough energy to start the car again if it comes to that!

If you set up the dual battery isolator with the manual override/jump start switch, then in having the winch connected to the aux battery with the jump start switch you can still have the main battery helping the aux battery to maintain power at the winch.
The only thing to keep in mind, is that most override switches are momentary push types, meaning that you'd have to hold it all the while .. so a dual throw switch with both an on throw and a momentary throw would be more versatile than the usual momentary type switch.

In my D1(with the Redarc isolator) I only have a momentary jump start switch, and with the recent change to cold weather has been the only reason my D1(Tdi) has started in recent months .. new batteries now, so problem solvered!

In my brothers D2(Td5) we're about to set him up with a dual battery setup, but he has a winch to deal with. The plan is to avoid using it, but for those worst case scenarios when it has to be used, I'm going to wire it up via the Aux battery with a on switch(hoping to locate an on switch with a momentary on side as well .. but for him, if I can't find a switch with both on and momentary, just an on switch is the better way to go.

I agree that if you do have to winch, it'd be better to do it off both batteries, rather than just the one .. and then again for the sake of allowances for worst case scenarios, if the winching process took longer than anticipated and was depleting the batteries too far, you'd switch the over ride off, so that the isolator does what it's supposed too, leaving you with capacity in the main battery.
Before any dual battery though in my brothers D2, I have to clean up the spaghetti mess of wiring the winch installer created for the winch power feed .. all loose and just thrown on top of the battery!