flat battery after 5 weeks

It’s that time of year…
The weather’s been bad enough that it’d been 5 weeks since the Mandello went out. Pushed the button…you guessed it, flat battery.
It’s taken 20 hours with a 0.8 A charger to bring it back from deep discharge ( result of a couple of attempts to start ). The starter drain was enough to reboot the ECU each time the button was pressed.
So, it’s only a 12Ah battery because with AGM they can get the cranking amps to start from that small package, but that’s not much capacity when you’ve got modern, always alive electronics draining it slowly. Or not so slowly, as it turns out.
I’ve had the alarm on, and it has a ‘sleep’ mode it enters after two days, but it must be draining quite a lot still.

I’m going to leave the alarm off and monitor battery voltage over the winter.
But the real takeaway is, top-up charge your batteries more regularly than you think. I used to do the BMW at 8 weeks. I don’t think the V100 can go anywhere near that long.

Reminds me of the Spada electronic clock thing from the '80s. Nothing new under the sun, I suppose.

Funny I was only thinking about the clock on my Spada earlier this week as the battery had run down quite a bit. I cycle a charger around several bikes. So I think I might disconnect it or put a switch in the circuit. It wouldnt be so bad but it doesnt really keep the time anyway.

My 2023 V7 drains battery for a no start after 3 days in the garage from fully charged after each ride. Guessing “they all do that sir”. Guzzi electrics. Fully re charge every night before a ride now. Including every 3 days. Never had this on any bike in 45 years.

I’m going to reply to both in one post.
Mr-P; that’s exactly what I remember everybody doing back in the day. The clock just didn’t work well enough to be worth the flat batteries.

Howo; that’s not right. It’s under warranty, you should take it back and get it fixed. Off the top of my head I can think of a couple of possibilities.

One is the ECU isn’t going to sleep. Modern machines keep the ECU powered up permanently. The ignition switch is just a digital input to tell it to enter ‘run mode’. This is supposed to be a low power mode that for most machines is ok for a couple of months. Clearly, with the Mandello it’s half that; not good.
But 3 days isn’t right. If the ECU still thinks it’s in ‘run mode’ that’d be about the right amount of time before it drains the battery. If you wanted to try something yourself, you could disconnect the battery, to reset the ECU code, leaving it for say, half an hour, and then reconnect it. That might get it back into a proper state.
The other possibility is more dangerous, and I haven’t seen the wiring diagram for your machine, so I can’t say if it’s likely. If the regulator/rectifier is leaking that would sap the battery juice. That in itself is irritating, but the bigger deal is if the leak turns into a short-circuit. Then it catches fire, unless it’s fused. I think Guzzi started fusing the charge circuit a while back.

But take it back to the shop.

I havent ridden my V100 for about 3 weeks now and it took 12 hours for the charger to switch to “maintain” mode…

PS is the Oxford charger lead that I found on my bike standard? It’s not mentioned in the handbook…

it’s possibly a socket for additional usb like on the v85tt?

Nope. Even got a yellow sticker on it that refers to Oxford Optimiser…see it on RHS here…

My BMW GS did this when new, it took several call outs and several weeks in various dealers, but they finally changed the alternator, which is buried inside the engine.

There have been a lot of discussions on the BMW GS forums about the cause, because mine is far from unique. There seems to be a general view that “it’s the tracker”, these too go into a sleep mode when not disturbed.

My own conclusion, after three years of ownership is that, putting the alternator failure aside, it only fails to start after a few weeks when I have been using the heated grips - my commute is too short for the battery to fully recover if the grips are drawing current, and a few days of “using it every day” like this will deplete the battery.

I have a multi-channel float charger that I bought for a boat many years ago, but never installed. I’ve fitted this in the garage, and have 2-core leads with plugs fitted to where the bikes are parked, and I’ve fitted sockets to the bikes. Just plug it in if the bike will be parked for a couple of days, eg, now.

This winter has been mild, so the BMW has only been plugged in for a couple of weekends, the Guzzi has been on float for weeks, and I should probably take it off, and check the battery water level.

I’d expect a fully charged battery to be able to start a bike on a cold morning after 4 weeks of inactivity. 3 days however, suggests there is something very wrong - as with my alternator.

can’t be guzzi fitment then obviously, dealer?

regarding flat batteries, my v85 has an alarm fitted and still doesnt go flat although it’s rare i don’t ride it for more than 3 days even in winter.

never failed to start so far in 2.5 years. other bikes have for either a frozen sidestand sensor, or burned out solenoid.

Andymay Thanks all good advice :+1: interesting bit about ecm sleep mode hmmm. Have sat nav & usb fitted direct to battery both have power off switches. No alarm :alarm_clock:
Thanks for your input
tarnbaz. I had a mail with your post reply but can’t see it here? Anyway answered above. I’ll talk to the dealer before next service in the new year.

Something wrong there, my 2022 V7 Stone has gone 3 weeks or more and still started fine :thinking:

Well I got home after 12 weeks away. During that time my V100S has been parked in daughter’s garage. To test it out my son in law started it yesterday and it started without drama at the first turn of the key. It has not been on any kind of charger in all that time. I’m collecting it on Friday and not expecting a problem with the battery.