Sticky wrote:

I had this exact problem on the twin battery system on my Patrol, the auto electrician explained that my twin charge system let the primary battery charge / balance the second system, this destroyed the starter battery in a year.

He told me that better split charge systems don't allow this and charge the batteries independantly, but I couldn't face shelling out on another system so he installed a 'throttle' that stopped the split charge system from working when the primary battery dropped below a certain percentage of capacity and I have had no problems at all since it was installed despite using the secondary battery for days at a time.

robharvey wrote:

James,

Is the "throttle" you are looking for a voltage sensitive relay (VSR)?

Have a look here:

http://www.bepmarine.com/125-Amp-Voltage-S...-1468.html

Rgds

Rob

Sticky wrote:

I had this exact problem on the twin battery system on my Patrol, the auto electrician explained that my twin charge system let the primary battery charge / balance the second system, this destroyed the starter battery in a year.

He told me that better split charge systems don't allow this and charge the batteries independantly, but I couldn't face shelling out on another system so he installed a 'throttle' that stopped the split charge system from working when the primary battery dropped below a certain percentage of capacity and I have had no problems at all since it was installed despite using the secondary battery for days at a time.

K9F wrote:

Could be one or the other, a voltage comparison check across the battery terminals with engine off and engine running should give you a clue. Even this check will not show how good your battery is at holding the charge though. (Battery capacitance value).
If both batteries are parallelled off (connected to each other) and the charge is significantly reduced on one - both will share the load. Effectively one will drag the other down. Could be several possibilities but that simple check above would be a good starting point! Hope this makes sense!

Speaking of holding charge - when I used to switch off the engine (with only main battery connected) the indicator used to stay in the green for quite a few minutes before slowly climbing down to 12,4V. Now it just ticks back in a few seconds to the orange LED. Seems the main battery should have a load test to confirm that it's a little tired by now.
According to the manaul the load test would be a little too complicated for the average Battery salesman.  Puma 110 - gone
Series III 1973 - going strong