Too many volts

Travelling from Ireland to Scotland yesterday the xj900f started to cut out had to pull onto side of road, after a few minutes it started and seemed to run well, this happened a couple of times. At first couldn't see any obvious cause until I looked at the battery and noticed it looked swollen it also felt very hot to the touch. The battery is an AGM about 4 months old,since fitting it the bike has only done short trips no more than thirty miles or so maximum
Anyway called recovery firm and when they arrived checked voltage across battery with engine running it was giving a reading of around 24 volts so ended up being recovered.
The questions I have is it possible that the AGM battery and the standard regulator are incompatible , the reg,/rec unit is original as far as I can see are there any good reasonably priced alternatives for this or am I going to have to fit a possibly 30 year old unit and finally what else am I likely to have fried, the bike will run but have disconnected regulator and running from battery
I am assuming some part of the ignition circuit did not like having the excess voltage applied and decided to stop working causing the engine to cut out but won't find out of any permanent damage has been done till I can take it for a decent length run

 

AGM battery shoumd be fine with the charging system on our XJ's.

You're probably looking at a defective regulator as your issue here. I think would also suggest replacing the battery as well.

 

oh dear, yeh, appears your reg/rec has given up, new battery about £60, new reg/rec, around £80, is yours a 7 wire reg/rec?
also check the red wire from battery to reg/rec, for corrosion or burning on the connections, that can cause the reg /rec to output more voltage, to compensate for the bad connection, check all plugs and sockets , on this, and the 3white wires from the alternator to the reg/rec

 

I agree with failed charging system as well. AGM battery works fine with stock bikes, Absorbed Glass Mat (AGM) and wet cell or “flooded” battwries are both considered lead batteries and contain an electrolyte solution. I have one in every bike, one is 6 years old.

 

Hi got to get back to Ireland day after tomorrow so won't have time to check out wiring, it definitely is a 7 wire unit, have a spare unused unfilled battery over there will bring it with me next trip, thinking about changing voltage reg to something like an separate voltage regulator, had to do that on a fj12 when it kept giving alternator problems

 

Start with troubleshooting the stock system, it’s robust and plenty adequate and reliable. In 20+ years of working on and owning bikes I’ve had one, maybe two regulators that were actually bad. The factory service manual has a great section in troubleshooting and remediating charging issues.

Once you start swapping out components you’ll add additional headaches. I’d rather keep it stock unless it’s a widely known weak point.

 

Sounds like that's a good plan, managed to have a quick look today, thinking now that it's wiring problem,as the cause of the fault ,the clock which is normally on is now off,until the ignition is on, and resets every time the ignition is turned so it may be a faulton the harness or connections ,possibly the wire that inputs the battery voltage to the regulator so will have to wait a couple of weeks till I 'm back in Scotland just have to use the Douglas till then

 

just have to use the Douglas till then[/QUOTE]
Douglas, is that a pet name for a bike or is it really a Douglas, ( as in) Dragonfly etc. ,love to see a picture of that ,if it is.?

 

Its a t35, from 1948 the first of the mark series which was in turn the forerunner of the dragonfly
Tried to upload a file but it didn't happen will try when I get to a better computer

 

24V charging could ruin the battery. So you may have to replace it once the charging system is sorted. Depending on what voltage is getting to the circuit boards, it could be damaging there as well.

You should look for voltage difference between the brown wire to the R/R and the terminal voltage as a start. Drops in voltage going to the regulator will cause it to over charge even if functioning correctly. But usually that's a couple of volts higher (not 24V). The other option is a faulty R/R. Luckily, they tend to not fail too often (usually it's the wiring that gets you) so swapping out with a used unit isn't a bad idea (and even getting a spare or two). I think the R/R are the same across all of the XJs.

 

Douglas looks fantastic, a mate had a Dragonfly back in the 60s , in khaki brown

i know there are at least 2 different R/Rs , my 600 has only 4 wires, and is earthed through the case.
others have 5 wires with an earth connection

 

The reg/rec has 7 wires, had 5 minutes today between fixing the mascerator and stripping out the kitchen so disconnected it ,bike started and ran, obviously only had it running for a couple of minutes, so dont know if any boards have suffered any damage that will show up when hot, fingers crossed the battery seems to be holding charge, well at least it has for a couple of weeks since it all went wrong, may try tomorrow to check wiring but there was no sign of overheating at the connector plug . Will take a copy of the wiring diagram and see if Ican work out what is going on

 

chuck it in the macerator

 

All OK now
Think the problem was twofold, the overcharging seems to have been caused by a broken wire behind the headlight, the fuel gauge and clock were going off when ignition turned off now staying on the cutting out which i thought was the ignition unit overheating was in fact a blocked fuel filter, now done around 600 miles without any problems.
Voltage sitting at 14.3 volts with engine running

 

Interesting - but I'm trying to figure out how a broken wire could force the R/R to output 24V and subsequently 'inflate' your battery.

 

not totally sure as havent really cone much more than stare in bemusement at the wiring diagram. Think the wire is connected to the part of circuit connected to the voltage sensing part of the regulator so if no voltage on that wire then regulator will be assuming battery is flat, and supplying full charge to battery and hence overcharging.