Effect of Autocom and Garmin SatNav on Battery

[Rocket]

Shortly after buying my 2007 RR I added a (basic) Autocom and Garmin Nuvi 550 SatNav.

Wiring into the bike

The BMW dealer hard-wired in the Autocom unit to the rear of the aux socket (tapped into the live wire going into the connector then -ve connected direct to the battery).

I wired in the Garmin myself utilising the spare SatNav socket under the tank (having bought the mating BMW connector and wired up as described on this forum). The Garmin unit is always removed from the bike after use

The problem

Battery would go flat after about a week if the bike wasn't used. This happened even with a brand new Exide battery.

Back to the dealer

What we observed

We discovered the bus system was not shutting down fully (allowing a couple of mins) when the ignition was turned off. There was a 0.12amps drain on the battery with the ignition off.
I disconnected the SAtNav connector (the Garmin unit was not on the bike - just the wire). The drain reduced to 0.07amps. We also disconnected the Autocom then switched ignition on (to power up the Bus) then switched off.
After 5 mins the Bus swithced off completely - zero amps drain on the battery

The Autocom and Garmin Nuvi 550 seem to prevent the BUS system from fully closing down fully when the ignition is switched off. There is something in the electronics of both which tells the BUS system to continue providing power even though they are not in use.

Proposed Solution

The dealer proposed they fit a relay switch which will isolate the accessories fully when the ignition is swithced off. This will prevent the Bus system from being fooled that power is still required. Autocom provide relay switches for this I m told

Conclusion
1. Not sure why the dealer didnt explain or do this when they first wired in the Autocom.
2. Problems caused from fitting accessories are not covered under the BMW warranty - except for those approved by BMW
3. Even with the Garmin removed the little box of electronics (on the cable ) creates a drain on the battery (ie is not compatible with the BMW BUS powering-down software)
4. Need to check compatibility of all electric accessories and ensure the power is fully off to prevent battery being drained(allowing for the built in delay ) - my experience is that even well know brands can cause problems (even when fitted by a dealer)
5. Alternative solution - retire asap so can ride every day to avoid such problems

The dealers suggestion has still to be proved. Will keep you posted.

[NeilS]

Are you sure that you're not being confused by the way the bike shuts down? I did some current measurements last spring when I was doing some electrical mods, and found the following:

1. Ignition on, engine off, 2.5 amps.
2. Ignition off, drops quickly to 0.6 amps.
3. A few seconds later, drops to 0.2 amps.
4. A few seconds later, drops to .07 amps.
5. About a minute later, drops to .0014 amps and stays there.

I ask because, if you're doing anything with your auxiliary equipment at the time a "step" in the shut-down procedure occurs, you don't know whether to attribute the current change to what you did or what the bike's computer did.

I don't know anything about your Autocom unit or about how it's wired, but I'm sure the GPS connector is positively shut off 1-2 minutes after the ignition is turned off. My zumo 450 reports this when it happens, displaying something like "I just lost external power, do you want me to continue on the battery?" Also, it's not uncommon for there to be a voltage-reducing circuit in some GPS units' mounts, and these circuits consume a bit of power even when the actual GPS is removed. However, this drain does not cause the bike to leave the GPS connector energized.

It's also worth noting that, with a dark current of 1.4 mA, leaving the bike unattended for a month only takes about one amp-hour out of the battery, approximately 7% of its nominal capacity.

HTH.

[Rocket]

You may be right, it may still be a problem with the computer - we didnt get consistent results even with the accessories removed.
However, adding a relay takes them out of the equation so if I still have problems after that mod, it must be a fault with the bikes computer.

I have to pay for the relay, which I am OK with if it resolves the problem. If not, then BMW will have to find the true cause and fix under warranty.

The technician seems to think the power drain should return to zero when the system is fully shut down.

Thanks for your reply.

Ron

[Dan-A]

Can you clarify the wiring on the autocom? The Plus is on the hot side of the accy socket and the minus is direct to the battery?

Try connecting the minus side of the autocom to the minus side of the socket. Going directly to the battery on the ground only might be a problem.

Otherwise I suggest a relay powered from the back of the socket and the power for the autocom direct from the battery. When the bike is on the relay will be powered by the canbus allowing power to the autocom, but the actual power to the unit will be from the battery direct.

[NeilS]

The technician seems to think the power drain should return to zero when the system is fully shut down.

Well, almost zero. You still need a bit of power to run the clock and keep some of the computer's memory circuits alive.

Going directly to the battery on the ground only might be a problem.

It's a good idea not to run lots of wires to the battery to avoid the "clutter" problem. But, electrically, it doesn't matter if a negative wire is connected to the battery, the negative side of another device, or the frame itself. They're all connected together.

[Rocket]

[quote="Dan-A"]Can you clarify the wiring on the autocom? The Plus is on the hot side of the accy socket and the minus is direct to the battery?

Yes, BMW wired it this way. They are fitting a relay but not sure where yet (shop closed yesterday when I called)

Will advise later

[Dan-A]

It's a good idea not to run lots of wires to the battery to avoid the "clutter" problem. But, electrically, it doesn't matter if a negative wire is connected to the battery, the negative side of another device, or the frame itself. They're all connected together.

I agree with that, but was wondering if the canbus system sees it that way?

[deilenberger]

CanBus really won't care. Seems people are afraid of the CanBus - but it's just a communications system between active components - and the battery isn't an active component (it has no computer in it..)

I personally prefer using a fuse-bus system where you can connect both negative and positive to one location such as the Centech fuse box.. but that's mostly for neatness and ease of troubleshooting.

[Rocket]

Relay fitted and celebratory ride to Chatsworth House, Derbyshire - UK's most popular tourist attraction outside London(about an hours ride from home). Thought if the battery was going to go flat on me , may as well be in a nice place!

Can't tell from photo but the grey steps to the right of the house up the sloping lawn is a beautiful water cascade.




Will see how long the battery keeps its charge.

[websterize]

Nothing like sheep to mow the grass. Nice shot. I hope they've got the electrics sorted out for you, Rocket.