Using Battery Tender to maintain charge on R12RT

[BeemerBerg]

I know this has been beat to death in previous posts, but I have another spin on this.

 

I'm thinking of hooking the rear socket directly to the battery on my R12RT (using an in-line fuse of course). This would make the outlet "hot" at all times, and take it out of the CANBUS system.

 

Does anyone know of a problem connecting my Battery Tender Junior to that "hot" outlet when the battery just needs a small trickle to stay alive? Just like the setup on the 11xx's. Seems that when the Battery Tender senses that the bike's battery is full enough, it just goes into a standby mode.

 

Or MUST I buy the special BMW charger to mate to the special BMW battery on the R12's?

 

Besides, when the battery is being charged while riding, how do it know that it's the alternator that supplying the juice, rather than an external power supply?

[steveknapp]

That works. I wimped out and just used the BT's harness.

 

The issues that plagued the later gel-battery 1150's still remain. And there are still dozens of opinions on what's the best battery charger for the longest life.

 

BMW warns about doing what you're going to do. The best reason I can see is that some chargers put out a high voltage to desulfate some batteries. This could damage the on-board electronics. The BT does NOT do this.

[KDeline]

If you ride it once every other week you should not need a tender. For the life of me, I can't understand why everybody thinks they need to plug these things in every night. I have NEVER used a tender and only charge the bikes every month or so in the winter. Batteries last me 4 or more seasons.

[kdude]

I agree... i'm using the bmw alarm on a gs 12 and have never have had to put the charger on during the riding season. However a sm. trickle charge is needed if the bike is going to be laid up for several months.

[Ken H.]

What Steve said. With a battery tender, smart technology type charger, directly to the battery (via your modified socket) there should be no problem. The battery itself will act as enough of a filter to prevent any issues I believe.

 

The only point of the BMW special charger that I can see is to tell the CAN-BUS electronics to leave the outlet on so the charging can take place. And of course with your modification that becomes a non-issue.

[Tool Man]

Ken,

It was my belief that at least on the GS model, the Accessory socket does NOT run through the Canbus system and is merely tied into the ignition circuit. It makes sense that it wouldn't be. Which is why I spliced into the socket harness to get switched power for my accessory fuse block instead of the running light. Haven't had a fault to date no matter how many lights and accessories are running.

[steveknapp]

Once BMWs had fuses and relays, they were kept in a box under the seat. Now there is this box called the ZFE (translates to Central Vehicle Electronics or some such). It's got all the same functions, but no replacable parts, in theory it lasts forever... It's THIS replacement of the fuses and relays, NOT CAN, that really should have ya worried. FWIW.

 

Just like anything on the bike that was electrical before went to a fuse somewhere. Now it all goes to the ZFE. So the accessory outlet connects to the solid state ZFE where before it went to the fuse box. And just as before where you wouldn't hook 100W of accessory lights up to a circuit without a relay, the same holds true now.

 

Why all the paranoia? Before if you overloaded a circuit the fuse would blow. Worst case you might melt some wire, tho that should never happen BUT it was all something that could be repaired.

 

The ZFE is an unknown. And expensive unknown. Now the ZFE should shut that output off, just like a fuse. It should be at least as safe as before. Unless they did it wrong.

 

The good thing about using the accessory outlet is you know it was designed for ~5A of load. If the ZFE blows up, and the dealer says "not under warranty, you had an accessory connected to the accessory outlet" he/she better start laughing.

[Ken H.]

It was my belief that at least on the GS model, the Accessory socket does NOT run through the Canbus system and is merely tied into the ignition circuit.

Well it still does the "alive" for 60 seconds after shut down thing, which makes me think it is still under the control of the ZFE.

 

Which as Steve points out, the ZFE is a module on the CAN-BUS, not the socket itself directly.

 

I too took the approach of using the socket to control a relay (actually the TPS-15 unit) to then power my switched items. No issues so far.

[Brimoon]

Please see below for the official word from the Fatherland:

[Brimoon]

Sorry, I meant to say please see the attachment.

 

Brian

[steveknapp]

Please see below for the official word from the Fatherland:

 

Whoo hoo! We can all sleep now!

[JayW]

<<If you ride it once every other week you should not need a tender. For the life of me, I can't understand why everybody thinks they need to plug these things in every night>>

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I puzzle over this too. I ride all year, though only once or twice in the coldest months. I have wondered how long it takes to fully recharge a battery that has been sitting idle for a few weeks. Is a 30 minute ride enough? Also, does running accessories such as heated seats and grips slow down the recharge rate (provided the total electrical draw does not exceed the capacity of the alternator)?

 

Jay

[Ken H.]

Also, does running accessories such as heated seats and grips slow down the recharge rate (provided the total electrical draw does not exceed the capacity of the alternator)

No. The regulator controls the charge rate and as long as the output of the alt. is greater than the total load the battery will be charging at the same rate regardless of the total load. BUT, as you may know, there are a lot of high load conditions when the alt. is not keeping up with the load, such as stop-and-go traffic riding. Under those conditions the load will effect the total charging rate and time as you will be in a discharge condition longer and deeper.

[JayW]

Thanks Ken. I also read somewhere that simply starting the engine and idling it will not charge the battery at all.

 

I am going to try to get by without a battery tender. I figure if I ride at least twice a month all year, and don't accidently leave the flashers on or otherwise drain the battery with the engine off, then a tender is not necessary. I'll bet I can get 4 or more years of service from the stock battery with this approach. Besides, if the battery does fail, the bike can be jump-started just like in a car, right?

 

Jay