I have a K100RT -85 that has two sets of extra headlights (High / Low with separate switch for both),Stereo,Heat Grips and electric movable screen,and this being Norway,there is more than one occasion that all the trimmings will be used all at once,and since I just got the bike & the battery need changing,I take the opportunity to ask for  advise about brand and amp before I do the purchase.. =)

Your battery has only one job, to start the bike. It does nothing when you switch your lights on and keep your hands warm, your 32 amp alternator does all that, because the engine is running.
Buy the battery specified for the K1100 it is plenty big enough for any K bike but is half the size and weight of the old technology fitted to the earlier K100. It also has more cranking power.

Hello!

18-20 AH is fine, use a AGM (cheaper) or a Gel Battery.
No old fashion acid Battery which you'll have to check the "water" level and drips acid!

http://www.biltema.no/no/Bil---MC/MC/Reservedeler/Batteri/MC-BATTERI-GEL-12V-20AH-2000029889/

http://skanbatt.no/batterier/vmf-batterier/vmf-mc-batterier/vmf-mc-batterier-12v-agm-gel/vmf-mc-batteri-12v-18ah-210cca-175x86x154-hyre/

Cheers

Other than the price, you will probably never notice the difference between the AGM and the Gel batteries. 

Save the difference by purchasing the AGM and use it to upgrade your extra headlights to LED's and then replace the 32Amp alternator with the later model 50 Amp unit.

Point-Seven-five wrote:Other than the price, you will probably never notice the difference between the AGM and the Gel batteries. 

Save the difference by purchasing the AGM and use it to upgrade your extra headlights to LED's and then replace the 32Amp alternator with the later model 50 Amp unit.

And how are you ever going to use more than 32 amps?

I was able to use more then 32 amps by running two electric vest, trailer lights, radio, intercom system, plus all of the motor electrics.  The bike wasn't even a year old when I found the limitations of how much I could use.  I never had any trouble except when using both vests and pulling the trailer.  When the 50 amp alternator became available about two years after the bike was made is when I installed the 50 amp alternator.  The OP with his two extra headlights may have a problem.  If you assume three 60 watt headlights that about 15 amps without anything else.

BobT wrote:

Point-Seven-five wrote:Other than the price, you will probably never notice the difference between the AGM and the Gel batteries. 

Save the difference by purchasing the AGM and use it to upgrade your extra headlights to LED's and then replace the 32Amp alternator with the later model 50 Amp unit.

And how are you ever going to use more than 32 amps?

OK, let's see.  You want to see and be seen at night, and have some tunes.  You need to pump fuel to the engine and control the fuel delivery.

Headlight 5A(stock H-4 Bulb up to 8A with Hi output bulbs)
Extra driving lights 3-10A (3A with LED's, 10A with Halogen)
Taillight with extra bulb 2A (Hi Viz Tail conversion)
Turn signals set up as running lights 1A (More Conspicuity)
Radio 5A
ECU and electronics 2A
Fuel Pump & injectors 5A

Total Basic load 18-30A

Stuck in traffic? Add Cooling Fan 5A

Total 23-35A

Cold weather?  Add Heated grips and gear 2-10A

Total 25-45A

Then you try to run that stuff when you're stuck in traffic and the engine is idling and the alternator is not at the full output point on the curve.  This is where the 50A alternator's slightly higher output will do a better job of keeping up with the load.

An added benefit is that the 50A, being designed for a heavier load will run cooler at typical loads which decreases internal resistance and thus the power losses due to resistance heating in the coils.

I hope this helps.

The voltage from a 32A alternator will start to drop away at 24A and the 50A unit will go to 42A before the volts start to drop away.
I found that at 32A the voltage was barely enough to charge at 13.3v at 4000rpm. The 32A alternators were an up grade from a 25A unit that was produced in the early 70s. I was told it was used for some VW cars.

Okay for the very few who seem to try and use as much electricity as the can, I'll re phrase that to say: For 99% of riders 99% of the time a 32 amp alternator will be more than adequate. 
I would love to hear that 5 amp consuming radio, please switch it on and we will listen from here. I wonder how many of us have radios on our bikes.
Why is it that when something is posted on here then the small minority come along and tell you their story.

Did you happen to read the original post?    Extra headlights, and I think he's riding in Norway, not the south of France.   Swap your shorts and flip flops for a heated vest and socks.

Take a few minutes and see what the audio output power of most auto radios is.  Then figure on how much of it you will need to hear it over wind noise.  Personally, I don't have a radio and don't really want one, but some of us might like one when grinding the miles away.

Many years back when I had a Honda 500-4 I was constantly short on electrical power. I was commuting 160 miles each way every weekend and no motorway. At night decent lights were needed so I upgraded and the alternator wasn't quite up to it. The only way I was able to deal with it a bit was a bigger battery. I didn't have radios or stuff but the lights on full power on a dark road did exceed the alternator output. A town on dipped lights helped restore some life into things. Poor roads and winter conditions its a must. Not to mention the then risks of a deer or cow on the road.


I am a bit of whatever as I refuse to have radio on the bike, or heated grips and don't bother with sat nav or phone charging.

The RT I have found with a decent pair of gloves and rain over gloves to keep wind chill off will allow me a 3 hour ride in zero temperatures without getting cold hands or cold anywhere.


I do have a discman for my music when I go camping.....preferences I suppose.! And my music system at home is around 800W......now if you fancy Mahler's 8th Symphony or Wont Get Fooled Again on full throttle I can happily listen to it above the sound of the lawnmower.

BobT wrote:Why is it that when something is posted on here then the small minority come along and tell you their story.

I was trying to give the original poster some advice that, based on his bike and equipment, would help him avoid problems in the future. 

Maybe you know more about what his needs are and how to provide for them, I have only designed and installed a couple successful electrical systems for long distance offshore cruising sailboats.  Looking at his application, I tried to consider the worst case likely to be encountered.  It's always that 1% situation that causes trouble when you least need it.  I would have thought that your experience as an aircraft mechanic would have taught you that.

Bottom line, I stand by my load estimates and recommendation for the 50A alternator.  Seems the electrical engineers at BMW were thinking the same way, since they went to 50A on the K bikes in 1994.

BobT wrote:
I would love to hear that 5 amp consuming radio, please switch it on and we will listen from here.

Switch it on to re-runs of Car Talk with Click and Clack and I'll open some windows and listen, too.

Okay you smart arses, Let us have a poll then. How many people with K100 8Valve and 16valve bikes have ditched their 32 amp alternators for a 50 amp one on this forum. Just answer No if you still have the standard and Yes if you have changed.
I'll be the first No.

The issue mainly affects the LT with the accessories and the LT didn't come out with the first Ks. First ones were the naked, the RS and RT. Did the alternator upgrade occur with the LT?

I'm still on whatever alternator came in the RT and LT because I never checked which one I had. All I know is the voltage they operate at but that doesn't tell me which one is in there.

BUT I have a 32A battery in the RT, only because my local lawnmower shop had a 20A 200CCA for €48 and a 32A 300CCA for €58 on the shelf and the Honda dealer wanted €90 for one I could have a week later. Better able to cope if the bike sits for a few weeks.

Given our weird winter I have a 20w rear light too. When my light upgrade kit is in then I need 20 amps for lighting alone and I do a lot of night riding. When I hit the brakes in town then I know I will be using more than the alternator is producing. I could fit LED lighting but the upgrade kit I have is for high wattage Halogen and I have already tried it out and its amazing even without the 2 driving lights.

So the answer is No for you then Olaf.

So far no.....but as you always say up north here is too cold....so we do need creature comforts.

My '94 RT has a 50A alternator, it is one of the main reasons I did not buy an earlier model.  It's the bike I use for touring and commuting in the colder months.  From November 1 to April it is my go to ride.  In the Fall there are nights where I ride home 55 miles from work.  I have a full set of extra lights on this bike as I ride country roads just after twilight and that time of year the deer are moving around a lot.

At 0C it is very nice to have the heated grips and a heated jacket liner and gloves.  What is especially nice is to have enough output to actually charge the battery when all this stuff is running so that at the end of the day I can actually just push the button to start the bike with a fully charged battery.  With a 32A alternator, and all that stuff running, the amount of current available for charging the battery is marginal.  While a partially charged battery will start the engine, driving around with less than a full charge on it will substantially shorten the battery's life span.  Resulting in it being dead before it's time.  Cold weather is brutal on electrical systems and I was making a suggestion that could very well save on the expense of frequent battery replacement.

I am assuming that since the original poster was living in Norway, the original question related to a situation similar to mine, and the mention of two sets of driving lights and the radio indicated that the power draw was probably higher than what is on my RT.  No where has BobT argued from an analysis of the loads on that bike other than to say that radios don't draw 5 amps.  Maybe it's his turn to lay out an argument for his position.

The car I drove for quite a few years when delivered to the Scandinavian market had a different battery arrangement despite being same engine and mine having the same preheater. No differences in electrical options or accessories. I suspect it was to allow for much greater use of air con, defogging, heaters etc.

This doesn't happen with bikes because no need to set them up for riding in -10 or -15C.

But the high load and cold has a huge effect on the battery and a start on a cold morning is quite telling. That's why I wouldn't put  the 20A 200CCA battery in my K. Too marginal in our climate although 99% of the time I would get away with it but I want 100%. On the Honda it would happen after a run that I used the lights on there wouldn't be enough in the battery to start the engine again....but it had a kick start so that was manageable.

Trouble is the place BobT lives in is warm enough there won't be a heated grip or heated suit in sight.

I too had to deal with needing extra light and it made such an amazing difference it was worth it. Sadly my experience to date with LED lights etc is that while they can be vastly more efficient the lumens don't seem to be where you want them.

When I popped the 160W H4 in the K it was awesome and the early K isn't all plastic so will take it. I have the ceramic bulb holders and relays and it was better than any of the cars.

On the Honda I wired the extra lights to the original wiring but with a switch so there was an option to have them on or off when using full beam, wired through a separate relay. Like the K it didn't have any relay as standard so it was easy and just ended up with two relays.

I use 2 x 100W spot lights and a 100W headlight plus at least 150W of other equipment that is standard K1100 electrical and even the 50A alternator was dropping away to 13.9V at full load so I went to a K1200 60A unit with the front half of a 50A alternator so as to fit and finally got 14.2V at max load. When riding at night I may do 100km without even going to lo beam once so I need a good output. So in answer to your question Bob a resounding YES on all 3 bikes.
Like I said the 32 A unit is marginal at best and it is at its worst when you need it most.

So we have two no's, not upgraded the K100 alternator from 32 amps. And zero yes have upgraded.
Rick does not count because his 1100 had a 50 amp as standard and he runs 100w bulbs which are illegal in most countries.
Why do people tell us about their K100 patio heater that needs more power than a nuclear power station when they know that others would never have that patio heater?

Wrong it's a 1993 K1100 and OEM is 32 A

BobT wrote:Rick does not count because his 1100 had a 50 amp as standard and he runs 100w bulbs
Why do people tell us about their K100 patio heater that needs more power than a nuclear power station when they know that others would never have that patio heater?

The needs of Ozians riding in the marsupially-infested dark of night and patio owners mindful of their guests' comfort don't count? What about puppies' and kitties' needs? Will theirs be the next to be abandoned?

RicK G wrote:Wrong it's a 1993 K1100 and OEM is 32 A

But Rick you failed because you didn't read the question "How many people with K100 8Valve and 16valve bikes have ditched their 32 amp alternators"

Got a 60amp one on my K100... but I'm clocking 6000-8000 miles a year at night on unlit country roads. Three headlights and two spotlights come with the added satisfaction of blinding cage drivers who won't dip. Total amperage used on my bike is 31A.

Bjornie: your best bet is not to change the battery but to try and find a 50amp LT alternator on ebay or from motorworks.co.uk. The alternator is a bolt-on fit but you will need to change the 32amp two-pin connector block for an 8mm ring terminal on the red wire and a 6.5mm spade terminal on the blue wire. It really isn't a difficult job.

If 50amps still isn't enough, it's possible to fit the back of an RT 60amp alternator into the front of the LT 50amp alternator, which is what Rick and I have done. Motorworks will sell you an already-converted 60amp alternator for the K100 for the Norwegian equivalent of £125 plus shipping.

Thanx for great thread and much useful information =) I will feel the bike for a little while and then make a decision  =)

Bob T

I posted that I changed my alternator.  I guess you missed it.  I'm glad that I did since before I changed it I had a dead battery when running my non-standard gear and accessories.  I never had any trouble when running the bike as equipped from BMW.  But why have extras if you can't use them.

BobT wrote:

RicK G wrote:Wrong it's a 1993 K1100 and OEM is 32 A

But Rick you failed because you didn't read the question "How many people with K100 8Valve and 16valve bikes have ditched their 32 amp alternators"

It is ambiguous.

I'm still waiting for BobT to explain how to run all our lights and heated gear on 32A.

Hello!

#BobT is thinking about replacing his 32A alternator With a 3-24 V 12 V Mini Micro alternator. The electricity that is saved will be donated to general electric ge and power the USA for free :-)

Cheers

https://de.aliexpress.com/item/3-24V-12V-Mini-Micro-3-phase-Alternator-Generator-Wind-Turbines-Hand-AC-Power/32708941941.html?spm=2114.47010508.4.2.dQu0pz

Hey that is an idea. Do away with the alternator that I hardly use and fit some little wind turbine battery chargers and a solar panel to the bike. Would not give the saved electricity to the US though, they pollute enough as it is. EDF pay me loads of money from the electricity that I generate on my roof. 

BobT wrote:Okay you smart arses, Let us have a poll then. How many people with K100 8Valve and 16valve bikes have ditched their 32 amp alternators for a 50 amp one on this forum. Just answer No if you still have the standard and Yes if you have changed.
I'll be the first No.

Yes

Sorta.

I have the alternator I got from an R bike, just need to change the terminals so I can install it.

Point-Seven-five wrote:Sorta.

I have the alternator I got from an R bike, just need to change the terminals so I can install it.

R bikes alternators are belt driven. K bike alternators are not so you also need to replace the R bike's pulley with the 12312305329 cup. ("clutch housing" in the parts catalog)  It is a different part than the 12311460302 cup of the 33 amp alternator.

Thanks, I didn't realize that they were different. 

Checking the photos at MaxBMW it looks like the difference is that the 35A clutch has a keyway, where the 50A doesn't.  Are there any other differences that require the different clutch.  The drive dog, hex nut, and the monkey nutz are the same for both.  Is the 50A clutch a different height? 

I can see where the lack of a keyway would prevent the 50 amp from working on the 35A, but what prevents the 35A from working on the 50A?

If you hold them side by side the 33A cup SEEMS to be the same depth and diameter as the 50A cup so it MIGHT be possible to use the 33A cup on the 50A alternator. However, I've done lots of 33A>50A upgrades and have always used the 50A cup just to be on the safe side.

The 50A alt is longer than the 33A.

The early coolant reservoir with the external sight tube doesn't play well with the 50A alternator.


The second gen reservoir with molded sight plastic does work with the 50A but you need to nudge the front of it out a bit to the right so it does work but isn't perfect.


The third gen reservoir is made to work with the 50A. Its tube exits from the rear instead of the front.

Good information!  This is a winter job so no rush.  The bike is a '91 16V RS so I think the overflow tank will be the third generation.  I plan on doing a test fit of the clutch and checking the height to the mounting surface of the tabs where the bolts go.

A 91 will have a gen 2 reservoir. Then gen 3 ones weren't used until 93.

https://www.realoem.com/bmw/enUS/partxref?q=17111461577