Electrical help - battery drain

[dswassy]

Hi all,

Yesterday I was syncing my carbs with my bike idling and out of nowhere the bike died and I was unable to get any power when turning the ignition to accessory mode. I tried putting the battery on a charger and the charger didn't even see that it was connected. Eventually it did wake up and start charging, leading me to believe that the battery was completely drained down to nothing. The battery is a brand new Shorai lithium product. I could be wrong, but a complete drain doesn't seem normal just while idling. Could there be a short or some other obvious issue? I do have an auxiliary fog light but it is mounted properly with its own fuse.

Any help is appreciated!

[gspd]

Try a known good conventional battery and see what happens.

Auxiliary fog light? LED or incandescent? 10 watt generic LED, no problem. 100W PIAA ol'scool, fuggettaboutit.

[dswassy]

Incandescent, but it's only 25-35w.

[melville]

I found the battery on my 1978 R100/7 was draining when I was riding with my son when he was a new rider. I was shifting up at 3000 rpm to keep from losing him. As he got more comfortable on the bike and I was shifting up at 4000 rpm things improved.

Airheads have dodgy charging systems if you're comparing them to your cage. They need some revs!

[Rob Frankham]

I found the battery on my 1978 R100/7 was draining when I was riding with my son when he was a new rider. I was shifting up at 3000 rpm to keep from losing him. As he got more comfortable on the bike and I was shifting up at 4000 rpm things improved.

Airheads have dodgy charging systems if you're comparing them to your cage. They need some revs!

An airhead should be charging at 3000 RPM (provided there isn't too much drain on the system) If your charge circuit can't provide full charge at 3000rpm then there's something wrong with it. Check the diode board and the continuity of the stator windings are in spec and the wires between the two are good and connections clean. The Bosch 3 phase alternator will charge on 2 of the 3 phases but only at reduced rate.

Rob

[melville]

I found the battery on my 1978 R100/7 was draining when I was riding with my son when he was a new rider. I was shifting up at 3000 rpm to keep from losing him. As he got more comfortable on the bike and I was shifting up at 4000 rpm things improved.

Airheads have dodgy charging systems if you're comparing them to your cage. They need some revs!

An airhead should be charging at 3000 RPM (provided there isn't too much drain on the system) If your charge circuit can't provide full charge at 3000rpm then there's something wrong with it. Check the diode board and the continuity of the stator windings are in spec and the wires between the two are good and connections clean. The Bosch 3 phase alternator will charge on 2 of the 3 phases but only at reduced rate.

Rob

I was shifting at 3K, mostly running below that at the time. Slow drain from ride to ride as 12.8V became 12.6V and then 12.4V. And yes, original untouched 1978 charging system. All sorted now.

[dswassy]

Is it normal for the battery to drain that quickly while idling?

[Rob Frankham]

Unfortunately, it's not as simple as that...

I would never recommend a Lithium battery for a vehicle with a 'heritage' charging system. Lithium requires a completely different charge regime from lead acid batteries. That being said, if your battery (no matter what the type) is losing charge at normal riding sppeds, there is something wrong. It should also be good for many hours at idle (although that, of itself is a very bad idea!!!).

If you are worried about parasitic current drain, you need to put an ammeter in the line leading from the battery to the bike circuits (not the starter lead) and check. A drain of 4 to 5 amps at idle (no lights) wouldnt be unusual. With the engine stopped it would depend on the position of the crankshaft.

It seems to me that, if the battery is discharging that quickly, the battery probably isn't up to the job of supplying sufficient current for any extensive period of idling and you should consider whether it was a wise investment. Not able to give specific advice without knowing the spec of the battery involved.

Be careful how you deal with the Lithium battery... They are dangerous if mishandled nor faulty!!!

In essence, my advice would be to junk the Lithium and revert to Lead Acid...

Rob