Low voltage - thoughts please?

colino

My moneys on a parasitic drain that they will have come across before and want to check for before condemning an OK battery.

nobbysn*ts

Mines on a bad cell. Good cell, fully charged, is 2.1 volts. So the battery has 5 good cells, nominally at 10.5 volts, and 1 poor cell, at 1.8 volts off load, hence only 12.3 volts. When there is a load, the good cells remain at a similar voltage, as they can provide the required current, but the bad cell drops to 1.4v, as it can't, hence the 11.9 reading. If it was a parasitic drain, the battery would indeed be going flat, so at 11.9 it would struggle to start, as all cells would be discharged. It doesn't, as the 5 cells have full charge, and can provide the current required to turn the engine over. A decent load tester will show the current is there, but the voltage isn't.

Stoke

Sounds like the battery. Got a spare you can try?