Flat Battery mystery

[John in Leeds]

Just back from boinging* around the Alps for a fortnight, so thought I'd add my thoughts & experience here.1) Some confusion about battery types seems to have crept in - Gel Batteries are not the same as AGM ones, so comments about one might not apply to the other. I've been using an AGM battery since 2004 and have just replaced it. Far superior to others in my experience, and you only need one, not two. They will fail if totally drained then not recharged. Otherwise they are pretty bulletproof (literally: I think you can find the video on YouTube!)2) The standard Commander wiring does indeed have the coils "Live" even when the ignition is turned off. This allows a measurable drain which can flatten a battery in about a week. (I did measure it & do the sums, but that was about 10 years ago). This is how I discovered the only way to destroy an AGM battery...... (Replaced FoC, but with a telling off!)I have fitted an isolator switch to prevent this. It also cuts off the fan feed to prevent that flattenning the battery if the thermal switch sticks "on". (oh, yes it can!! And you can't even bump-start a Rotary with zero Volts in the battery)3) There's many things wired downstream of the Starter Solenoid, so disconnecting that may also disconnect other components, depending on what you pull off where. i.e. don't assume it's the solenoid which is at fault (if indeed anything is).4) Notwithstanding (2) above, the current you are measuring is TINY, if the meter is measuring uA. Anything in the micro-amp department is of no consequence. Having worked backward from memory, my drain was showing as about 50mA (= 50,000 uA). I'm a bit puzzled as to why that range is ABOVE the others on the meter though.5) At the risk of stating the bl*****g obvious, if you suspect the battery, disconnect it after charging, then see if loses any charge over a week. i.e reconnect it and see if it works ok after that time.6) The clock takes a tiny current. You could probably run it for a year on a bike battery, so I wouldn't blame it for draining the battery. Alarm systems are a different matter, I believe.7) Given the tiny current involved, I'd suspect the movement of the bars is changing the earth return resistance, hence the current, as the current squeezes across greasy bearings to return to the battery. As I recall, there is NO earth return cable from the front to the battery. (I know this is normal practice, but it doesn't mean it's good). This has no bearing on leakage currents I might add. I'm just rambling....None of which helps you much, I know. Personally, I suspect the leaky-coil-current as the culprit, even though your meter suggests no detectable drain. (No.That doesn't make sense. But I'm sticking to it as the probable reason). In which case, pulling out the Ignition Unit fuse should stop the drain. That's effectively what my cut-out switch does. It's now been fitted for around ten years and I've never suffered a drained battery since. Except when I forget to turn it off. Which kinda proves the point.I think there was sumet else I meant to mention, but I can't recall what it was right now.....(*rear damping expired on day 5.)

[Richard Negus]

[quote="John in Leeds"2) The standard Commander wiring does indeed have the coils "Live" even when the ignition is turned off. This allows a measurable drain which can flatten a battery in about a week. (I did measure it & do the sums, but that was about 10 years ago).[/quote]Hi John,I'm aware that the coils positive is always live, but always believed that neither the tacho nor the ignition unit could conduct to ground when not powered up. Do you have any ideas where the current drain occurs?

[John in Leeds]

Hi RichardNow, funnily enough, I was thinking of asking you the same question!.... I have assumed - with no actual knowledge - that the ignition unit allows a certain amount of current flow, even when not powered up. Given the unit is mimicing a contact breaker which has a normally-closed state, this could be the case. As I am blissfully unaware of the specific circuitry, I don't know if that is plausible or not. Which annoys the physicist in me; but the engineer in me is quite happy that my cut-off switch cures the problem! Furthermore, I now have one of Graham's ignition units fitted in place of my old original unit. This seems to exhibit the same problem, but again, I've not studied it in detail. I can't see the tacho being any significant drain on the system either, which does rather leave the ignition amp as the only suspect.John

[Mick Taylor]

Here is an update, I have been through the wiring harness reasonably thoroughly, whilst doing so I had the meter connected and it showed a drain of 0.9 which is vastly greater than the 0.03 I started with originally. I did find, as I had the headlight out to access the large harness plugs to the instrument assembly and switchgear that the reading would fluctuate.Long story short, I found nothing untoward until I looked around the area of the starter solenoid and found one black wire in the harness had clearly overheated at some stage. This is almost certainly old damage that pre dates my ownership as I found identical damage to a single black cable near the horns shortly after buying the bike.I split a length of sleeving, slipped it over the damaged wire and re bound the harness, I also replaced the solenoid as I happened to have a new one.....and the reading on the meter while all this was going on continued to fluctuate but has now settled and stays at -0.03. Why?.....I haven't the faintest idea. As to the scale on the meter, 20u/10 is at the top of the scale and although it is measured in micro amps, I took the /10 to be some form of multiplier, so it may be a much greater scale than first appears to be the case; the book of words unhelpfully offers zero guidance on reading the scales.So, I'm back where I started, but I have fitted an Optimate harness so I can test the battery voltage in a few seconds without removing the seat or side panels.....I will give it a week or so and report back. Thanks for the help and guidance, it is appreciated even if I don't understand the nature of electrics to the extent that some of you obviously do.Mick.