ex-British gas mk7 starting problems

[onomatopoeia99]

After having to call the AA from Tesco car park as my van (2.4, 330 awd) decided not to go (not turning over on the starter, just a half-hearted lurch then solenoid clicking) I've been trying to figure out what's going on with it. I'd not used it for a couple of weeks before taking it the two miles to Tesco, prior to that it was getting daily use since I bought it a couple of months back without any problems. I actually ended up canceling the AA as 20 minutes later it did start when I tried it.

It has two batteries and an "impact-g" isolator mounted on the side of the driver's seat mount just inside the door. When I put the charger on the rear battery took no charge at all and the front not all that much, under 20Ah worth. I left it a week (used my car for work) and checked the battery voltages this motning. Rear battery at 12.7V, front battery at 12.0V. When I tried to start it, it wouldn't go again. The isolator is not isolating and I haven't tried to charge it this time.

I'm given to understand the rear battery starts the van from reading other topics on here before posting, but that's the one that seems to have / retain charge in it, so am now confused as I don't know why if the rearmost one is fully charged, it won't turn over.

Also, both batteries are 110 type, but I've found topics saying they should be 100 type if two are fitted. Guess that doesn't matter as they still physically fit in the space provided.

[ake]

Both batteries are used at startup

Your battery voltages are low

Have you tried a jump start?