Out of the blue ,the battery on my Mk 2 850 has failed, a 12N9-4B-1 it won"t now hold a charge and the charging light stays on all the time. the 3 phase 180 alternator has always been able to cope with a 10 W Q/H head light pilotbulb pretty well, but when I added a Q/H Stop/Tail bulb ,this seems to have been too much. Any point in a larger capacity battery ,i.e the Mk 3 14 amp one. Would it work? Would it fit? Or would it just take a bit longer to drain that one too? Thanks in advance folks!
If your alternator puts ou…
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Alec How old was the batte…
Alec
How old was the battery and what type of voltage regulator is fitted? As Owen says there is no point in fitting a larger battery. Have you checked if the regulator is working correctly? If not then the system may have overcharged the battery and considerably shortened its life. This is very common where the old zener regulators are still in use.
David
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Hi Alec, At the risk of te…
Hi Alec,
At the risk of teaching you to suck eggs, I had a similar problem where the wire to the regulator failed, although it looked good it had actually broken. However for a real technical answer speak to Al osbourne.
Good luck.
HT
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If your alternator puts out 180W and you don't have a MK3 electric starting aid then the battery can be small (physically as well as storage capacity and price). The current draw for your lights and ignition system could not normally exceed 180W (even running a 100W highbeam globe). The electrical storage capacity of your battery is really only for ignition at starting (you can even replace it with a capacitor for starting but the lights intensity will rise and fall as alternator output varies with revs). A dead/dying battery will suck alternator output and create heat in the battery due to the high resistance.
A multimeter is a good investment