BMW K bikes (Bricks)

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doktor33

doktor33
active member
active member
Hi,

I bought a DEKA ETX 20 L Battery for my K75 RT ABS. Does anyone already used it ? 
I don't know if it's linked or a coincidence, but my ABS ECU is KO since I installed it. I wonder if I did not make a mistake with this battery. I know it's more powerfull for start up... and may be too much ....

Thanks

http://k75rt.wordpress.com
    

BobT

BobT
Life time member
Life time member
Cannot understand why anyone would fit a huge, heavy old tractor battery to a bike. The battery only starts the bike and then does nothing. Cannot see how it would damage your ABS ECU.
I fitted a 600 gram lithium battery to my Ducati and it is very powerful for starting the bike.

    

Laitch

Laitch
Life time member
Life time member
@BobT wrote:Cannot understand why anyone would fit a huge, heavy old tractor battery to a bike. 
Suppose there was only enough ready money to buy one battery so it's used in the both the moto and an old tractor, transferred from one to the other when necessary. One person usually wouldn't operate the two engines simultaneously unless, of course, the tractor needed to be used for powering a generator providing power to the barn during dynamometer tests on the moto.  What are the chances of that happening?


__________________________________________________
1995 K75 81,000 miles
DEKA ETX 20 L Battery for a K75 RT ABS ? Usa-lo10
    

robmack

robmack
Life time member
Life time member
There was an active thread recently talking about replacement starter relay and I got to thinking "Why not fit two smaller lithium batteries instead of one large AGM?"  One battery would be dedicated to turning the starter motor and the other main battery to just powering the remaining electronics in the bike. There are clear advantages.  Since one starter battery is only used during starting, it can be of a smaller capacity because there are no other loads to drive than the starter motor.  The other battery can be sized for a much smaller capacity since there is no demand for cranking amps.  There is plenty of room in the battery compartment for two batteries side by side.  There is no situation where the starter relay can weld itself because there is no situation during starting where the demand on the  main battery would cause terminal voltage to droop.  The LSR would lessen the demand even more during starting.  The downside is fitting a splitter to ensure that each battery can be charged adequately by the alternator but prevent one battery discharging into the other.  This is a problem which faces boat owners so there are solutions out there in the market.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Dai

Dai
Life time member
Life time member


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

BobT

BobT
Life time member
Life time member
@robmack wrote:There was an active thread recently talking about replacement starter relay and I got to thinking "Why not fit two smaller lithium batteries instead of one large AGM?"  One battery would be dedicated to turning the starter motor and the other main battery to just powering the remaining electronics in the bike. There are clear advantages.  Since one starter battery is only used during starting, it can be of a smaller capacity because there are no other loads to drive than the starter motor.  The other battery can be sized for a much smaller capacity since there is no demand for cranking amps.  There is plenty of room in the battery compartment for two batteries side by side.  There is no situation where the starter relay can weld itself because there is no situation during starting where the demand on the  main battery would cause terminal voltage to droop.  The LSR would lessen the demand even more during starting.  The downside is fitting a splitter to ensure that each battery can be charged adequately by the alternator but prevent one battery discharging into the other.  This is a problem which faces boat owners so there are solutions out there in the market.
Are you mad? There is only one purpose for a battery on a bike or a car and that is to start the engine. Why would you want another one?

    

robmack

robmack
Life time member
Life time member
@BobT wrote:Are you mad? There is only one purpose for a battery on a bike or a car and that is to start the engine. Why would you want another one?
I don't think I'm mad.  But I guess I should so for second opinion. DEKA ETX 20 L Battery for a K75 RT ABS ? 1f600

A battery has more than that one function on a vehicle -- cranking the engine to start is only but one of them.  It supplies power to the circuitry on the vehicle when the engine is not running.  It provides ballast and stability to the system when the engine is running; the alternator is supplying both power for the vehicle and power for keeping the battery charged and the battery absorbs voltage and current fluctuations.

Our Mercedes has two batteries; one supplies most power for the engine and electronics of the car and the other supplies power for standby and auxillary functions.  My suggestion is along the same lines of thinking as Mercedes engineers.



Last edited by robmack on Sun May 23, 2021 9:16 pm; edited 1 time in total


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Most sailboats with inboard engines have two batteries. One that supplies lights and other stuff and a second that is just for starting the engine. So why not the same on a bike?


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

Shep

Shep
Gold member
Gold member
Well many bikes did have two systems in years gone by. One was a foot activated direct crank human battery to turn over the engine. If there was a battery then it was there for ancillary equipment.
Shep


__________________________________________________
Model        Production Date/Serial Number
K100RS      1984 July/ (F0040448)
K100RS      1986 Dec/ (H0142581)
    

Laitch

Laitch
Life time member
Life time member
@Point-Seven-five wrote:Most sailboats with inboard engines have two batteries.  One that supplies lights and other stuff and a second that is just for starting the engine.  So why not the same on a bike?
Because there is no refrigerator, anemometer, depth finder or television that might need power while a recliner cradles you as you watch the logistics involved in the international shipping of methylamine on Breaking Bad with the engine shut down.  Smile


__________________________________________________
1995 K75 81,000 miles
DEKA ETX 20 L Battery for a K75 RT ABS ? Usa-lo10
    

BobT

BobT
Life time member
Life time member
A motorbike is neither a Mercedes nor a boat. Mercedes do not even make bikes.
The BMW bikes are compact and very functional so why make it more complicated for no gain at all. 
Many old bikes never had batteries at all.

    

Dai

Dai
Life time member
Life time member
@BobT wrote:Many old bikes never had batteries at all.
Do

Not

Remind

Me.


(Horrendous memories come tumbling back of riding something vintage back in the 1970s one very dark night where the lights from the farmhouses shed more light on the road than the candle up front. The only thing that let me get very slowly home was a full moon. Thirty ****** miles of it!).


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

doktor33

doktor33
active member
active member
@BobT wrote:Cannot understand why anyone would fit a huge, heavy old tractor battery to a bike. The battery only starts the bike and then does nothing. Cannot see how it would damage your ABS ECU.
I fitted a 600 gram lithium battery to my Ducati and it is very powerful for starting the bike.
Hi,

I park my bike in a garage, far away from home, without any light or plug. Of course, the battery is just required to start the engine. But, when the battery is too low and you can't keep it in charge, that's absolutely not fun. 
This new battery is very powerful for startup, and I imagined that it's too much for the ECU. Just an hypotisis, 'cause I try to find why my ECU is KO after having changed the battery. Of course, I did not notice if it was right just before (didn't think I might have this joke !).

http://k75rt.wordpress.com
    

doktor33

doktor33
active member
active member
@robmack wrote:There was an active thread recently talking about replacement starter relay and I got to thinking "Why not fit two smaller lithium batteries instead of one large AGM?"  One battery would be dedicated to turning the starter motor and the other main battery to just powering the remaining electronics in the bike. There are clear advantages.  Since one starter battery is only used during starting, it can be of a smaller capacity because there are no other loads to drive than the starter motor.  The other battery can be sized for a much smaller capacity since there is no demand for cranking amps.  There is plenty of room in the battery compartment for two batteries side by side.  There is no situation where the starter relay can weld itself because there is no situation during starting where the demand on the  main battery would cause terminal voltage to droop.  The LSR would lessen the demand even more during starting.  The downside is fitting a splitter to ensure that each battery can be charged adequately by the alternator but prevent one battery discharging into the other.  This is a problem which faces boat owners so there are solutions out there in the market.
Interesting. I read a lot of post about starter relay that weld itself. Even if you eliminate all the classic reasons, it may still happen and you don't know why. The ellectrical circuit is quite simple I think, but it remains a mystery.

http://k75rt.wordpress.com
    

BobT

BobT
Life time member
Life time member
@doktor33 wrote:
@BobT wrote:Cannot understand why anyone would fit a huge, heavy old tractor battery to a bike. The battery only starts the bike and then does nothing. Cannot see how it would damage your ABS ECU.
I fitted a 600 gram lithium battery to my Ducati and it is very powerful for starting the bike.
Hi,

I park my bike in a garage, far away from home, without any light or plug. Of course, the battery is just required to start the engine. But, when the battery is too low and you can't keep it in charge, that's absolutely not fun. 
This new battery is very powerful for startup, and I imagined that it's too much for the ECU. Just an hypotisis, 'cause I try to find why my ECU is KO after having changed the battery. Of course, I did not notice if it was right just before (didn't think I might have this joke !).
If the battery is too low that it cannot keep its charge then it is either defective or old, time for a new one.
The battery supplies voltage (electrical Pressure) of between 12 and 14 volts, it could be the size of a cruise ship and supply that voltage and it would not be any more powerful in volts than a small one. Your ECU is broken for other reasons, did you connect the battery the wrong way round for an instant?

    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
@Laitch wrote:
@Point-Seven-five wrote:Most sailboats with inboard engines have two batteries.  One that supplies lights and other stuff and a second that is just for starting the engine.  So why not the same on a bike?
Because there is no refrigerator, anemometer, depth finder or television that might need power while a recliner cradles you as you watch the logistics involved in the international shipping of methylamine on Breaking Bad with the engine shut down.  Smile

Cell phone charger, GPS, sound system, heated gear, running lights, ABS. Might make sense to isolate those loads from the battery that starts the engine


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

BobT

BobT
Life time member
Life time member
@Point-Seven-five wrote:
@Laitch wrote:
@Point-Seven-five wrote:Most sailboats with inboard engines have two batteries.  One that supplies lights and other stuff and a second that is just for starting the engine.  So why not the same on a bike?
Because there is no refrigerator, anemometer, depth finder or television that might need power while a recliner cradles you as you watch the logistics involved in the international shipping of methylamine on Breaking Bad with the engine shut down.  Smile

Cell phone charger, GPS, sound system, heated gear, running lights, ABS.  Might make sense to isolate those loads from the battery that starts the engine
Why would you need to isolate them? None of those loads would be drawing anything if the ignition is off. If the engine is running, none of them will be drawing anything from the battery as the alternator is supplying the electrical energy.
Your phone charger and your GPS use so little energy that you could run both from the battery for weeks without much effect.

    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Get stuck in traffic for an hour or so with your lights on, wearing heated gear and you seat and grip heaters running. Brick alternators don't generate squat when the engine is idling. Then stop for gas and start your engine. Your 35 amp alternator ain't going to do the job. And don't reply with any nonsense about using the alternator to start the bike.

I'm not advocating two batteries. I have been all over the U.S. and Canada in all kinds of weather including snow with one seven year old battery. I'm just acknowledging that there may be situations where two batteries may offer a certain amount of power reserve and that the size and weight of lithium batteries makes it possible.



__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

BobT

BobT
Life time member
Life time member
@Point-Seven-five wrote:Get stuck in traffic for an hour or so with your lights on, wearing heated gear and you seat and grip heaters running.  Brick alternators don't generate squat when the engine is idling.  Then stop for gas and start your engine.  Your 35 amp alternator ain't going to do the job.  And don't reply with any nonsense about using the alternator to start the bike.

I'm not advocating two batteries.  I have been all over the U.S. and Canada in all kinds of weather including snow with one seven year old battery.  I'm just acknowledging that there may be situations where two batteries may offer a certain amount of power reserve and that the size and weight of lithium batteries makes it possible.


Good job you mentioned the weather because outside of the US we have no hot or cold climates. 
Do you have a voltmeter on your bike? I have fitted them on most bikes that I have owned and the reason that manufacturers fitted alternators rather than dynamos was that they still have spare power at low revs. 
If there was a reason for needing two batteries on a bike then why has no manufacturer aver done this on a standard production bike.
By the way there is no such thing as a brick alternator, it is a fairly common Bosch unit as was fitted to many different cars in the 80's and 90's and they have no problems ether.

    

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