Disconnecting the battery. ..what (if anything ) will it affect?

[fred_jb 10,269]

Interesting discussion.  The manual for my GS says I shouldn't connect a charger directly to my battery due to the possibility of damaging the bike's electronics.   Of course BMW sell a CANBUS enabled charger which works via the 12V socket in the cockpit, but this socket is not usable by ordinary chargers as apparently it gets shut down unless it gets the right secret handshake from a compatible charger.

 

I've nevertheless connected a fused Optimate lead to my battery, but mainly to use with my air compressor which has an Optimate style lead.  I haven't yet decided whether to risk connecting my Optimate to it, but as it is an old version 2, I don't think it does anything fancy like voltage pulses to recover a dead battery, so would hopefully be OK.  I've used it without incident on all my other bikes.

[Tex 36,817]

As you say, Fred, interesting discussion. Most enjoyable. Thanks everyone. Don't forget though that many old motorcycles and cars (right up to the late sixties and early seventies for BSA) were positive earth. So rather than saying 'disconnect the negative lead first' we really need to remember 'disconnect the earth lead first'.

 

Or steer clear of old crap (sorry, I mean 'classics').

[ste7ios 469]

Optimate has a CAN bus version.

[SteveThackery 3,090]

6 hours ago, Jeffprince said:

Does that include the Optimate range? I use one for winter topping-up, without disconnecting the battery. Been doing it for years....

 

Sorry, Jeff, I don't know.  We would need to stick an oscilloscope on it to find out exactly what it was doing, or ask the manufacturer, I guess.  I do know it uses a far more sophisticated way of maintaining the charge in a battery, but whether it uses any desulphating techniques I honestly don't know.

 

As I say, I'm very sceptical indeed about the risks to ECUs, so I'm not at all surprised you've suffered no ill effects.

[SteveThackery 3,090]

2 hours ago, fred_jb said:

Interesting discussion.  The manual for my GS says I shouldn't connect a charger directly to my battery due to the possibility of damaging the bike's electronics.

 

Yes, it's interesting and I think this is because there are no proper standards for battery chargers, in terms of what voltages, currents, pulses, etc, they can deliver.  So from BMW's point of view a battery charger is essentially an uncontrolled and unknown device, which might do almost anything.

 

So, despite my scepticism, I actually agree with their policy.  From their point of view it's an unnecessary risk so it's easiest to advise against it.

 

From the owner's point of view, well, that's different.  I think the risk is minimal (although I would probably treat desulphating chargers differently until I've learned more about them), and I've never harmed any electronics by using battery chargers or messing with the battery leads.  Nor can I see a credible explanation of how you would actually cause harm from connecting/disconnecting the leads.

 

As always, I'm open to new information and willing to change my mind if presented with some credible, objective data (not just a story of what happened to the bloke down the road's mate).  

[ste7ios 469]

Steve, desulfation in general is controlled overcharging, allowing the voltage to rise up to 15V - 16V for some time, increasing also the battery temperature. But there is no standard, and some implementations are completely unscientific... That can harm VRLA batteries because overcharging causes gassing, depleting the electrolyte, and it may also cause grid corrosion...

 

Also the quality of every implementation is also important. A cheap charger may think that the voltage is e.g. 14.4V but in reality can be much higher. One example is a recent release of Lidl's charger.

 

Don't trust them too much...

 

On the other side Oxford Maximizer 3800 thinks it has reach 14.4V but it's lower... That doesn't do any good too. 14.4V to 14.6V is necessary to break soft sulfation crystals...

 

Lead acid batteries are well documented because of their ~150 years history... A nice resource about batteries is: http://batteryuniversity.com/learn/article/sulfation_and_how_to_prevent_it

 

Similar problems we may have from a broken charging system, so it's a good idea to monitor it with a permanent voltmeter, even with the latest MOSFET shunt Regulators / Rectifiers...

 

[fred_jb 10,269]

3 hours ago, ste7ios said:

Optimate has a CAN bus version.

Yes, apparently the version 4 has a CANBUS mode, though I think some people have had problems getting that into the correct mode to talk to their BMW bike.  Might try one of those and sell my version 2.

[Andy m 23,664]

10 hours ago, SteveThackery said:

 

I agree.  However, I've yet to see an convincing explanation of how these voltage spikes actually arise, nor have I ever seen any solid evidence of an ECU damaged in this way.

 

 

I have processed (rejected) claims on ECU's from UK vehicle builders where the power inputs have been destroyed and jump starting and battery charging have been noted by the people making the claim. The damage is the same as claims where you can see welding was done. I've even seen one with a burn mark on the case that matcheda welding set earth clamp.

 

Andy

[Guest Mac750]

On 2017-5-10 at 10:59, SteveThackery said:

 

I agree.  However, I've yet to see an convincing explanation of how these voltage spikes actually arise, nor have I ever seen any solid evidence of an ECU damaged in this way.

 

Every internet user "knows" it to be true, even though it happened to someone else......

By the way, I've gotta say that auto electronics are incredibly reliable these days.  Thirty years ago, aftermarket electronic ignitions were sometimes questionable, but I can truly say the last time I had an ECU fail on a car or motorcycle in my ownership was back in 1986 on a Saab 900 Turbo.

Welding is the main bug bear . (Not needed on a motorbike unless it's a Himalayan.😊) 

Always disconnect the battery first as a mig welder will spike / fry electrics on a car. 

[Tex 36,817]

2 hours ago, Mac750 said:

Welding is the main bug bear . (Not needed on a motorbike unless it's a Himalayan.😊) 

Always disconnect the battery first as a mig welder will spike / fry electrics on a car. 

 

It was welding that buggered up the R1150GS in the Long Way Round. The (grossly overloaded) rear subframe broke. It was mig welded up by a 'back street' guy who neglected to disconnect the battery. That's why they had to buy the little Russian (?) two stroke for the cameraman to ride while the 'back up' crew had bits flown out from BMW. 

[baben 11,813]

I would think that the fact you can buy a charging tail from Optimate so that you are able to easily connect your charger to the bike indicates that they do not see a problem existing. If it did someone would have sued them by now!

[Guest Mac750]

3 hours ago, baben said:

I would think that the fact you can buy a charging tail from Optimate so that you are able to easily connect your charger to the bike indicates that they do not see a problem existing. If it did someone would have sued them by now!

Had one on the PC as the battery was hidden . Took it off and fitted it on the NC no problems to report.