Battery Charging

Post by **Radar in oz** » Tue Jul 03, 2007 8:52 pm

Sorry if it has been covered elsewhere, but I haven't been able to find an answer.

Does anyone know what tricks or connection sequence is required to connect a battery charger/tender via the accessories socket?

I have any epicycle charger.

My bike's manual says the socket switches "off" when the battery is charged and the ignition is off, does this mean that it switches itself on whenever it feels like it needs charging????

Radar

TWI · Post by **TWI** » Tue Jul 03, 2007 9:02 pm

The accessory socket is switched off shortly after the bike is shut down. Unless you connect a BMW-branded, recent build charger which signals the system to leave the socket switched on. The alternative is to wire the socket directly to the battery (which I did). The you can use whatever charger you want.

Post by **celticus** » Wed Jul 04, 2007 4:06 am

I also have done a work around for charging. I installed another non-canbus BMW style female socket ( Am I being redundant?) on the bike hooked straight to the battery and have the canbus socket tied up out of the way.
Works great

NeilS · Post by **NeilS** » Wed Jul 04, 2007 9:18 am

There are two issues with using the accessory socket for battery charging:

1. The CANbus controller turns the socket off when it detects that the charger is not providing voltage to the socket. So if your charger periodically turns itself off to test the battery, as many "smart" chargers do, the socket is disconnected until someone cycles the ignition key.

2. The CANbus controller includes a switch that cycles the charger. It breaks the connection when IT determines the battery is fully charged and re-connects when the battery falls to 12.7 volts. The result of this is the battery is cycled between full charge and about 80% charge, which isn't real good for it.

Bottom line: Use a direct connection to the battery.

BTW, the info above is from Tecmate. I have an Optimate charger, and I asked them about it when I first bought the bike. I was very impressed by their detailed reply.

Post by **Radar in oz** » Wed Jul 04, 2007 10:30 pm

Thanks for the replies.

Post by **amr122** » Fri Jul 06, 2007 1:04 am

When connecting the charger to the battery (not through the accessory socket), are you still supposed to have the battery disconnected from the electrical system so that the current from the charger doesn't damage the CANBus?

thanks,

Post by **celticus** » Fri Jul 06, 2007 3:48 am

I didn't disconnect mine. No problems.
Mark

NeilS · Post by **NeilS** » Fri Jul 06, 2007 7:38 am

Good question, Adam.

Normally, a battery acts as an "anchor" on the electrical system, preventing the voltage from rising too high. But when the battery is dead (or close to it), it can no longer perform this function, and some chargers might produce excessive voltages.

What's excessive? I don't know. I'm sure BMW does, but I doubt you'll find anyone there who will tell you. It's not in the manuals.

I'd say you won't have any problems charging a good, but discharged, battery or keeping your good battery topped up over the winter. But it wouldn't be a bad idea to disconnect the battery before charging when you think it might be on its last legs.