my experience of a knackered battery is that (depending on knacker-age) connecting up to another battery will bring about smooth running, but on disconnecting you'll be back to square one. But at least you know more.

I imagine on the GS the engine management requires a certain level of battery charge, otherwise it fails the entire 'running' process. As opposed to something like an enfield which doesn't have any notable electrics (or brains like the GS) and therefore runs without a battery, on mechanics. Brains need power to do their calculations on how much fuel to dump in, etc, etc.

Having read your post Tim and scratching my head along the way, I go with Dougies' thoughts: I also had a battery problem recently (not a Beemer) and the bike would start easily with jump cables or by bump starting using a slope and/or pushing. No way would the bike circuitry charge the bike battery however.

Also, as Dougie says, the bikes that run without batteries have completely different electrical circuits with no electric starter of course: oh those days were so much simpler! (Only last year actually, when I owned a kicker TT600R!).

I also agree with you: try a replacement battery, assuming that all of the relevant connections are in good condition, no corrosion, well earthed etc.
Even if you cannot get the "right" Amp-hrs to suit the bike, borrowing one that is more or less right may prove the problem diagnostics.

Good luck,

ps Yes, modern "electronic" bikes need a small amount of power in the battery to activate the various circuits/electronic brains. That's why they will start by pushing etc: when the starter motor is not drawing current from the battery.

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Dave

Tim,

I can't add much here, but I would definitely post this on ADVRider.com as well, in the GSpot forum--people are pretty quick with GS-specific diagnosis there.

Good luck!

Thanks for the replies, guys. I think I understand the problem better, and have cross posted on AdvRider as well.

I'm going to try to find a replacement battery.

1. Has to be 12v
2. Has to fit in battery tray
3. The manual says 14Ah, so is it OK if I try for 10Ah or better?
4. Does it matter if it is unsealed and has to be filled with acid and then charged?

Anything else I need to be aware of?

Tim

__________________
"For sheer delight there is nothing like altitude; it gives one the thrill of adventure
and enlarges the world in which you live," Irving Mather (1892-1966)

Yes check if your Reg/Rec is what has caused the problem and over charged (Boiled) your battery.

__________________
Home of the UK Coast 2 Coast off-road Challenge
www.C2CChallenge.co.uk www.4X4Safari.co.uk

before you buy a new battery, you could have a car/bike shop test your existing battery. If they can fully recharge it for you, and it holds the charge (off the bike), then you can put it back on the bike and see if it holds the charge with the bike running.

to expand on the above post. when you fit the battery, check the it's not being fried again. I guess you've no electrical tester? At the very least run the bike and check for smells/leaks/bubbling/heat/etc coming off the battery.

An electrical tester would tell you if the battery is charging while the bike is running. So I guess do the above sensual test, and then ride to a car/bike shop and borrow a meter (or get them to help you). if the battery is not charging your reg/rec could have gone faulty (only when the unit gets hot?).

As mentioned, the regulator/rectifier may be stuffed - this can give a smell of bad eggs from the battery as the latter is cooked by over-charging, but the reg/rec may be under charging so that the battery simply goes flat.
In any case the smell thing may not be relevant with todays sealed batteries! (I am not sure about that one).

Nevertheless, IMO, trying a different battery is well worth doing; so many problems in the electrics start with a duff battery.
I was "hoping" that you could borrow another battery, ideally, or use the jump leads as an alternative to test the starting side of things.

Borrowing a batt is preferable IMO (for fault finding), because once you add the acid to the batt in the way you mention, it it "activated" and, therefore, sold (in any UK dealer anyway). Once you prove the problem source, then you could buy the battery.
Yes to the 12V.
Battery tray fit, yes, if you want to ride with it rather than just test the starter etc at a standstill.
Capacity: well 14 Ah would be much better, but it may be worth a go, provided that those fancy electronics on the bike do not "object". With lower capacity you would get a shorter time to the battery being discharged when running with lots of gadgets, lights ablaze, heated clothing etc etc. Also it would turn over the starter motor for less time before being flat.
Doesn't matter if it is an unsealed version: just an earlier technology.

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Dave

Hi Tim...
I suspect that the connection from one cell in the battery to another cell is going open circuit, hitting the battery top may do some good .. at least you'll be happerier giving it a hit

This bike won't run without the battery .. needs the battery to 'smoth' the alternator output.

If you are stuck for a reasonable battery for the bike - just get a small car one (the cheaper the better (you will be throwing it away eventually) and put that in parrallel to the bike battery - put it on the rear rack and run good thick wires up to it.

An unsealed battery may leak acid if the bike falls over .. make certain any vent tube is long enogh that any fluid will not touch the bike - even when tilted on its side.

You are meeting heaps of locals this trip!
Do check the battery voltage when the bike is running - more that 13 and less than 14.5 is ok. But on the symtoms I too think it is the battery .. or a loose connection .. check the earth wire... sometimes the lug to wire connections go faulty too.

Good luck.

------------------- Battery Specifications
The Ampere Hours (AH) won't worry you too much ..

The CCA (Cold Cranking Amps) may worry you - on a cold morning this gives the maximum current you can exect to draw from the battery .. should be in the order of 150 amps at least IIRC .. things like the Oddessy battery are over 220 amp .. your starter would draw 90? amps .. more on a clod morning ..

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Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S

I took the battery out yesterday and flashed the terminals--nothing at all.

I think (or rather am hoping) the problem is isolated to a duff battery. The chances of getting a powerful enough one locally are remote and although there's a BMW dealer in Casablanca the logistics are flakey. So a helpful GSer in Spain is getting one this afternoon and handing it someone coming over to Morocco next week.

In the meantime I'm planning to take the rear seat off, strap a small car battery in its place and jury rig it to the bike battery points by cannibalising some heavy duty jump leads.

At least that way I'll know for sure whether it's just the battery. Will let you know as things progress. In the meantime many thanks for the advice and support.

Tim

__________________
"For sheer delight there is nothing like altitude; it gives one the thrill of adventure
and enlarges the world in which you live," Irving Mather (1892-1966)