g8dhe wrote:Several things here;
1. There should be two fuses one either side of the relay (unless the relay is mounted very close to one of the battery terminals) one connecting to the S/B the other to the L/B.
2. The fuse is there to protect the CABLE(s), not the battery / relay or anything else, hence the need for two fuses as either battery can supply the power. The rating of the fuse however must also take into account the charging current of the L/B and yes 20Amp is a bit on the low side given that the relay is adequately rated at 70 Amps, 30 Amps is the normal sort of size but the wiring between the relay and both batteries needs to be able to handle 30 Amps as well !
3. Batteries can be a problem at this time of year as first of all most journeys are shorter than during summer and holidays, and there is usually more power being consumed from the alternator for things like Lights etc and hence you may find that the L/B doesn't get charged as much.
4. regarding the measurement of current yes you do expect a small surge of current when you first connect a battery, however did you make sure that the meter was set to at least 10 Amps and that you were using the right sockets for the leads? If so then an initial 0.2 Amp reading dropping to 0 looks correct, but its a good idea to switch on something like an internal lamp that is connected to the L/B just to make sure that you are reading the expected values, try connecting as you did before then turn on an internal lamp you would expect something like 1 Amp to be indicated, if so then when it is switched off again and the meter reads 0 then that indicates that you DON't have an unexpected load on the battery, NOW (your sure no other lights could have been left on before the battery went flat?).
5. Charging the L/B from a mains charger once it has gone flat is highly recommended as otherwise even if you do uprate the fuse to 30 Amps even that can blow if your revving the engine when the charge relay first comes in and the battery is flat.
1. Only 1 fuse (will double check later) between relay and LB. But, relay is right next to SB
2. Great, will change to 30A
3. Makes perfect sense, we have the heating right up and the lights are always on at this time of year.
4. Yes, was connected to the 10A (it's max) and red lead was connected to the 10A socket. Will test with appliances on later. It's possible there was a light on over Xmas.
5. Bought a Durite battery charger a few years ago and now ALWAYS charge it before a weekend away without hookup. Learnt the hard way at a festival with no fridge and water pump after 1 day!!
Thanks guys, I really do appreciate all your comments and advice.
Off out for lunch now but will no doubt be back posting later as I want to do as g8dhe suggested in point 4
