Back in Chiang Mai I did not know about that and so what happened was that the car was standing in the garage for the better part of 5 months. Half loaded … Yes.. I know.. now. The batteries seem to have sulfated nicely and already before that incident they were not in their best state any more (as I know now ). I really treated them bad for the better part of two years. So I always cared that they don’t get discharged over a certain point, but not really cared about getting them fully loaded as I didn’t know about the importance of that.
Now I read the data sheet of my AGMs and found out that they already have done more cycles than they should be able to do.. . I treated them bad and they did approx 1/3 more cycles than they are calculated to do.
With the problem at the crossroad and many, many attempts to start the car I needed to connect the leisure batteries to the starter battery (got a switch for that in the car) to support further starting attempts but after a while they were empty too. So it seems that this was the final straw that broke the camels back.
So now I measured one of the AGMs and the result was bad.. well bad doesn’t even come close. I disconnected the middle battery from the main setup and connected it to one of the solar computers for a day. Fairly quickly the battery couldn’t take any more load, but I left it connected until the evening. After letting it sit for a while to check the volts it can hold (12.5) I connected a controlled power drain (lights) where I know how much power it draws – in that case exactly one amp. After not even an hour the battery was down to 12 volts, and after approx one hour the solar computer shut down the lights cause of the 11.7 volts warning. So this battery has approx 1 amp hour left, out of 120. The battery of my notebook is stronger, but doesn’t weight 30 Kilos – so it’s basically dead lead.