Although the car in question is not a Jaguar, I bought four of these CTEK units for my classic cars on the advice of this forum so I'll post the question here. Two of the cars have Interstate brand AGM batteries, one a few months old and the other about 20 months. The older of the two has in the past several months begun to occasionally at random throw an error on the CTEK ostensibly indicating that the battery will not hold a charge. However, the battery always appears fully charged, always seemingly turning the motor over at full strength and starting the car without fail. Is the CTEK continuing to operate even though its detected an error or does it give up and stop at that point? I've swapped around the units and another CTEK has thrown the same code. Thinking that there was a battery drain, I'd disconnected the battery and still found a few weeks later, the error had returned. I've never had that error on the CTEK or any error for that matter, even on the ten year old failing lead batteries that I'd replaced. I'm wondering if there is really a problem with this AGM battery that I should try to get Interstate to replace it while its still under warranty. Wonder how I'd convince them? Or is there something weird about CTEK and AGM batteries?

 

Ask ctek!

 

I'll try to contact them after the holidays, but you know how it is. Misery loves company. I'd feel more hopeful if somebody else posted that they'd experienced the same thing and successfully resolved it.