Battery voltage & charging anomalies

[psychonaut]

Hi - my second techie help question today

I have some shenanigans going on with my electrics that I don't understand. I have an '81 diesel, with a 1Y lump.

I have a Bosch alternator rated at 70 amps, and a starter battery rated at 60ah. My leisure battery is rated at 110ah. Both batteries are hooked up to a Zig unit, model CF9b, with the relevant fuses close to the +ve terminals of each battery. Following Covkid's useful entry in the Wiki, I have also fitted a bettery meter in the dash so I can keep an eye on the voltage and charging of both batteries. Ihave joined the battery watchers!!

On a long run (Preston to Cardiff) a couple of weeks ago, I noticed that no charging seemed to be taking place on either battery, and both were showing a voltage of 9.8 volts. This voltage didn't seem to change over the space of a few days, but the van had no problem starting at all, and fired into life on the first turn of the key every time. Surely a voltage on the starter of 9.8 volts would make starting difficult if not impossible? I'm happy that no starting current is being drawn from the leisure battery as the fuse (25 amp) isn't blowing. When starting the van, there was no further voltage drop when the glow plugs were warming up, which seemed odd, although probably a good thing bearing in mind how low the battery voltage seemed to be to start with!!

Also, despite being hooked up to the mains for 24 hours with the Zig Unit on, no charging seemed to be taking place, with the voltage on both batteries remaining pretty much static at 9.8 volts. I have charged both up with a mains charger this weekend, and the starter now shows 12.15 volts, dropping to 11.24 with the glo-plugs warming, and 14.31 with the engine running, thus proving the alternator is doing it's job. But why didn't it charge the batteries on the long run from Preston a couple of weeks ago? Also, is checking that the Zig is charging the batteries as simple as taking a multimeter reading off the connectors to each battery at the back of the Zig when it's plugged into the mains?

Many thanks for anyone that can shed any light or offer any advice for me

[Hacksawbob]

I used to have a zigan although I think there is a charging feature on them its not very good . I ran a chunky wire from one + to the other (with a fuse) to aid charging on mine I believe you can fit a diode to prevent reverse flow but I didn't. There are also fuses on the zig I take it you have checked them out?

[elsid]

I have had a few charging, or lack of, problems over last weekend, both batteries flat! I did a bit of messing about with my Zig CF9B and found that if you have the charger switch (not Zig mains charger) set to towing, with the engine running, the alternator will charge both batteries, when set to "on site" only the van battery receives a charge.. When on mains charging through the Zig unit and the switch set to "on site" only the leisure battery is charged. Has anyone got a circuit diagram of the Zig CF9? I have done a fairly comprehensive wiring diagram of the van but not the internals of the Zig unit.
Sid

[Hacksawbob]

http://www.freewebs.com/12voltsdc/Zig%2 ... %20PDF.pdf

[Red Westie]

Check the battery cell electrolyte levels, it could be you are boiling dry or near too on one or more cells.

Martin

[psychonaut]

Many thanks to all for the suggestions and advice, I'll follow them up