Bosch battery guarantee?

Thanks..

Mrcheerful used his keyboard to write :

Well thanks for your efforts.

I managed to get through to Bosch themselves this morning and they said it had to go back to where purchased. Unfortunately a single outlet place, but luckily not too far away - could have been very awkward if it had been bought 300 miles away.

Took it back to the original supplier and they managed to get it to charge up and it seems to be holding it so far. The car only usually gets to be used at the weekends, but it only does good long runs and is often kept on a battery maintainer. Last weekend it wasn't on a maintainer and was completely flat, having done a couple of hundred miles the weekend before. I put enough charge in it to start it, did

100 miles and it was left until yesterday and found to be completely dead again.

I have a couple of chargers which will not charge a dead battery and another three which will, but none of them could manage to bring the battery back to life yesterday. Even a spare good battery in parallel via jumpers could not start the car, yet it started first touch with the spare battery just lashed up in place of the Bosch.

I checked the discharge with key off and temporary battery fitted - that was 500mA initially, then fell to 200mA, then fell again to 100mA and I suspect fell even more some time later. Engine running it was

14.2v with the Bosch refitted.

So I am now quite puzzled as to why the battery was flat in the first place and why I could not get a charge into it yesterday.

It was left connected for several hours and made no difference, yet the same spare battery started it instantly once I had botched it to the connections - posts on the car, flat terminals on the battery.

Voltage across the Bosch when I took it in was 9.79 yet their test instrument(?) suggested the battery was good, just flat.

Mrcheerful presented the following explanation :

Sorry, that was the OBD's reading which I meant to translate to a correct value. My Fluke suggests 14.5 to 14.6 at a tick-over, adding headlights on makes no difference to the reading.

I will ask tomorrow morning. and post here by midday.

I have not been able to get a definitive answer. Apparently the seller can choose their guarantee period and conditions. Costco will only deal with Bosch batteries they have sold from any of their own stores, their guarantee used to be 5 years and has now been dropped to 4. He suggested that you might want to contact Bosch directly and ask them about it.

Sorry it is not better news.

That sort of concurs with what my bloke said:ask the actual supplier. max discharge should be 30ma or less. 14.2 is not particularly high. my first thought is that there is an internal break in the battery. you need to leave jumper leads connected for a good few minutes if a battery is really flat before trying to start it, unless you have a monster battery and very heavy duty leads.

10 volts says to me that one cell is absolutely duff, probably the junk that falls off the plates has bridged the plates, thereby sort of avoiding that cell altogether.

Modern electronic testers can give the condition of the battery even when not fully charged. Although mine won't work on a battery reading 9.79 volts open circuit. That is totally discharged in practice.