Hitchcocks Forum

If I charge my battery on the bench via my Optimate charger it goes through the cycle fine, about 2hrs on charge light, then to good, green light, but if I charge with battery on the bike ( EFI ) I get a 2hour charge then desulphate for about an hour, then it goes to weak and stays there. It seems to contradict it self. The battery is only 6weeks old and the bike has no ancillaries to cause a problem. Any thoughts appreciated.

Check the wiring for somewhere it has chafed through. I had similar symptoms on my CX500 and wiring under the rear mudguard had dropped allowing the tyre to touch the wiring loom.

I have not been out to look at my bike but the diagram shows 3 20a fuses, you could take them out and try again if the problem goes try replacing them one at a time and recheck after replacing each one, if the problem reoccurs it will be a clue as to were the problem is, if there is no physical damage the reg rectifier may be at fault, do other people have this issue with this type of charger, I have an Optimate some ware which I stopped using long before I bought an Enfield as it did do some strange things

New battery means nothing, have you any battery voltage readings on or off the bike?

Hi, I've had this problem twice with my 1992 500 classic. Like you charged on the bench, all ok. Charged on the bike not ok. So the problem must be with the bike wiring and not the battery. First time it was rusty water and corrosion in a fuse holder, I cleaned it all up and fitted a new fuse and all was ok again. The second time the fault was traced to a poor earth wire to frame connection. Cleaned up the connector eye on the wire and used emery on the frame. After assembly with liberal use of Vaseline the problem went away again and has not come back since as I give both the fuse holder (now in the tool box out of the elements) and the earth wire a good looking at during servicing. Same thing happened with my old Yam TDM when the main fuse got corroded. Hope this helps, Ian.

I should have reported that the fuse in both cases wasn't blown so I assumed the corrosion was causing a problem with the measurable voltage detected by the Optimate, as the electrics all still worked on the bike but not to the standard demanded by the Charger. Ian

After a 70mile trip I checked the voltage it was 12.7v, but not knowing much about electrics that does not mean much to me, the charged battery read 13.1v. I will check but I think my fuses are 15 amp.

Rosy charge the batter off of the bike, check the voltage fully charged (should be 13.2 at completion of charge.) Leave the battery off of the bike for 24 hour and check the voltage again. It really should not drop much below 13 volts.
Put the battery back on the bike and then check the voltage with the engine running above tickover it should be charging at 14 volts plus.
(This is just basic diagnostics.) But as has been stated already a new battery can be duff. I have had the problem several times with "Japanese" batteries that are in fact made in America.)

As papasmurf states for the battery condition check but what are the readings? You should have no need to charge a battery remotely if the bike is used once a week or fortnight.

Just a point. Checking voltage on a battery doesn't tell you much. Put a load on the battery then test it. A completely knackered battery could show 12v but when a load is applied it will drop right off.