This is the scenario Few days ago we had a power cut - went on for quite a while so decided to use gas stove in camper van by the house to brew up. Some time later somebody -let's not play the blame game here- well OK it was SWMBO, returned kettle to van, but didn't quite close the sliding door properly. Result this morning one totally flat battery.
Not to worry, get out Halfords Automatic Battery Charger, connect it up, switch it on and - nothing. Slight hum tells me power is on. There's a little orange light to tell you its charging and a little green light to tell you when its gone into maintenance mode. There's EVEN a little red light to tell you you've connected it the wrong way round - and blown the fuse. There's a switch to choose between normal battery and sealed battery and a switch for Bike or Other vehicle battery. What a clever charger.
Dead as the proverbial dodo. Not a single light on. Perhaps it's gone to meet it's maker. Auxiliary battery is right next to vehicle battery, so quick check, and connect it to that - and yes it works. Little orange light on - charging - soon followed by little green light - maintenance mode. Back to vehicle battery - nothing. Get out meter, no voltage. Rig up as ammeter, no current. Get out test lamp. Connect "earth" lead to + on vehicle battery and point to + on Aux battery and light comes on. So vehicle battery is not high resistance/open circuit, so why the f*** won't it charge.
Can't get other vehicle alongside to use jump leads, only way would be to tow out camper van onto road to get near it to use leads. Can't use aux battery to start - it would destroy it.
Solution - put a jump lead from + on aux batt to + on vehicle batt to see what happens. Just touched for an instant and charger which was still connected, burst into life.
WHAT F****** USE IS A BATTERY CHARGER THAT WON'T CHARGE A TOTALLY FLAT BATTERY?