Charger causing ABS unit failure??

[ricky]

No, this is not the usual "my ABS shows a fault when cold starting" post!

When I purchased my R1150GS back in 2001, the dealer advised me against using my Optimate 2 battery charger on BMW bikes fitted with ABS, as he had heard anecdotel but significant evidence that it could damage the ABS "computer" unit under certain (unspecified) circumstances. Is this a myth I wondered?

I must admit to being more than a little sceptical, but heeded the advice and used the official BMW trickle charger instead. More recently, having fitted a sealed AGM bettery, and being aware that the BMW charger is not suitable for it (float charge voltage too low for AGM and Gel batteries), I started looking at specs for chargers. The same dealer said that the Oxford 'intelligent' charger was ok, but I don't know which model, and so far I have not found the specs.

I note that the Optimate 3 has a special recovery mode to charge badly sulphated batteries, in which it tries to push a constant 200mA into the battery. The terminal voltage can rise to 20-22v in this mode - could this be the clue to ABS unit failures? Is the ABS unit fully isolated with the ignition switched off? Hmmmmm.

Discuss!

Rick Sterry

 

[skywalker]

No its not.It has a permanent live feed to it

 

[ricky]

Aha, then it could indeed be true that the ABS computer will get zapped under certain conditions.

Glad I didn't put it to the test!

Rick

 

[ianm00]

To be safe when charging the battery with any charger why not just disconnect the battery from the bike, then charge.

Ian

 

[ricky]

Yeah, good idea. The fact that this means removing, or at the very least, lifting, the tank, doesn't in any way put you off then?

Rick

 

[ianm00]

Ricky,

On my 1200GS the battery terminals are accessible when you remove the seat.

Never had any experience of other BMWs, so yes this may be a problem if it means removing the tank!

Ian

 

[ricky]

The battery is rather hidden away on many bikes, instead of being under the seat like it was with my old VFR. It's a real nightmare to get at on some machines.

Getting at it does mean lifting the tank on the 1150GS, but at least you don't need to disconnect the fuel lines or the fuel pump and tank sensor connector. However, disconnecting the battery without removing the tank altogether is a bit fiddly - not worth the hassle just to charge it. Also, if you are unwise enough to forget to disconnect the negative terminal BEFORE the positive, and your spanner slips, you may find yourself in the middle of a large conflagration!

Anyway, I now have a homemade non-intelligent charger which will NOT attempt to stuff 22v up the ABS computer, so not a problem if I plug it in the accessory socket without disconnecting the battery.

Rick