charging? or not?

[mrjones]

hello again everyone i finally got my 750M on the road a few weeks ago ,i did around 20 miles when i noticed the electrical power fading and luckily made it back home, upon inspection my new gel battery was almost flat so i looked on the internet for a likely cause, as i had fitted a new improved reg/rec i was puzzled , to put it mildly! it turns out you arnt meant to use a gel battery with the modern reg/rec ,when i bought it there was no mention of this anywhere , however the battery from my other bike (exup 1000) was the same size and the traditional lead acid type so i swapped them thinking my problems were over i went on another ride.

however the same thing happened again! this time i wasnt so lucky and had to call a breakdown company to get me home, anyway the reg /rec was changed for a new one (no quibble no charge) and i got a new lead/acid battery as the one i had used was boiled dry and u/s, my problem is that now theres almost no power getting through all i can get if the horn trying to beep but nothing else, obviously the fuse isnt blown and both batterys work fine on my other bike so any ideas?

[Alan H]

There's been lots posted about poor or non charging on triples, so best place to start is a search for 'charging' or 'alternator'. Same kind of reg/charging system on all triples so any reading will give you a start with the issue.

[teazer]

Electrical issues are a PIA, but fortunately it's not rocket science or brain surgery....

The real problem is that Japanese electrons in the seventies were much smaller than modern electrons so there was less power....


I'd suggest that you beg, borrow or steal a known good battery and connect it up. Then test voltage with everything OFF and then with it at idle and then as revs rise.

Off will probably be around 13v. ON and running it may be as low as 12 or maybe a little higher and as revs rise, it should go up to around 14v or so at the battery. What those numbers are on your bike tells a lot about the charging circuit.

For example if voltage does not rise at all with revs, it's not charging. If voltage is too low, it's under charging and if it's above say 14.5 it's too high.

The charging system on our bikes has an electromagnet and that is fed by the regulator. As voltage drops at the sensing wire, the regulator allows more power to the field coil to generate more electricity. The wrong type of regulator obviously could be an issue. As can the voltage at the sensing wire. Because of voltage drops across all the old switches and connections, the voltage that the regulator senses may be much lower than the actual battery voltage, so it overcharges trying to "catch up".

That's also why many of us recommend inserting a relay for the ignition circuit and two for the headlamp circuits and then run a new lead for the voltage sensor.

[PaulD738]

I'm sure I've read on here somewhere that modern combined reg/rectifier units can over charge our Stone Age charging systems and boil lead acid batteries dry?
Our very own prehistoric electrical Einstein Alan H will no doubt elaborate further

[Alan H]

If a wire (via a relay) is run direct from the battery to the new reg/rectifier unit, it 'should' be ok.
The biggest problem is that a few bad connections running through the 40 year old harness causes a low voltage to the unit and makes it think the battery needs lots of charge when it doesn't.

[summer0123]

I have a modern reg/rec and a Mottobat on my GT750 A.

When I fitted the reg/rec I measured the voltage at the terminal which fed the old reg and found it to be 11.8 volts with the engine running. I suspect this is because the wire comes off the ignition switch, through the kill switch, onto feed the coils and then ends up at the reg terminal. To get a more representative voltage I ran a new wire from the ignition switch (switched terminal) directly to the reg terminal and found I had a voltage of 12.4 volts with the engine running.
This modification maintains 13 volts across the battery at all times even if I ride the bike with lights off or full on.

I also had a charging problem initially and found the generator brushes and springs to be worn. After I replaced them I have had no problem.
paul

[mrjones]

that sounds like good advice although ,forgive my ignorance ,what type of relay? model type size? and yes i understand the live/red wire from the ignition or battery but to which wire on the combined reg/rec? i started the bike this afternoon and lo and behold the lights worked the neutral light came on but the horn didnt work! it must have gone out of "tune" in the 40 or so miles ive ridden. im going to fit a relay before i ride it but fingers crossed its alright now

[Alan H]

No it isn't. There's a bad connection that needs finding and sorting before it knackers something completely or leaves you stranded.

[teazer]

What voltages were you seeing at the battery when you ran it?

If you want to fit a relay into the ignition circuit, almost any automotive relay will work. Most are 20 amp or 30 amp and that is more than enough. For headlamp circuits I prefer Panasonic mini relays which are smaller and easier to fit inside the headlamp shell.

[summer0123]

Clearly you need to sort the issue out with electrical systems not working but if you want to run a modern reg/rec and concerned about overcharging and do not want to add a relay to the bike which could be a point of failure then send me a private message and I'll e mail a drawing of the modification i done on my bike.
paul