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Old 11-27-2013, 09:16 AM   #1
Singletrack_mind OP
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grip heaters on a /5?

I'm wondering about buying a friend of mine some grip heaters for his R75/5, but wondering if the stock charging system can handle the extra draw. Has anyone done this?

I am not thinking OEM BMW heated grips, which were not available for the /5s, I'm thinking just basic stick-on heaters that go under the grips. In my experience these work fine. Current draw would be 2.5A on low and 3A on high.

I believe the stock alternator is rated for 20A at 14V, so available power downstream from the RR will be a little less, but there's not much going on electrically anyway: A 35W headlight, 5W tail and the ignition system, which I don't know the power draw for. Blinkers, horn and brake light are inconsequential since they are only on briefly. Unless the ignition system draws a huge amount of power there should easily be an additional 3W in there I'd think, but I'd love to hear a yes/no from someone who's done it.

Thanks.
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Old 11-27-2013, 09:48 AM   #2
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I'm following this with interest. My hands kill me after a 45 minute ride to work in the morning when the temps are in the 20s.
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Old 11-27-2013, 10:29 AM   #3
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Old 11-27-2013, 10:40 AM   #4
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Shouldn't be a problem at all. I usually run with both grip heaters and electric vest.
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Old 11-27-2013, 12:49 PM   #5
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If there is an issue you might try replacing marker lights/running lights with led lights. Reduce all electric draw you can on existing items. But usually bmw's are overbuilt.
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Old 11-27-2013, 12:50 PM   #6
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If you're worried about it, just get a later alternator. They go for not much money at all on ebay, and they're identical to what was on Tonti Guzzis from like 74 on up. They're all 20 AMP, vs I think 14 for a /5 I bet you could find a set up for $50 or less, and your battery will be happy for it.
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Old 11-27-2013, 01:30 PM   #7
Singletrack_mind OP
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Quote:
Originally Posted by Pokie View Post
Shouldn't be a problem at all. I usually run with both grip heaters and electric vest.


And are you riding a /5 with stock electrics?
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Old 11-27-2013, 05:52 PM   #8
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Yup, stock 180 watt alternator.
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Old 11-27-2013, 09:08 PM   #9
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Thanks Pokie, I'll go ahead and do it.
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Old 11-28-2013, 02:52 PM   #10
dilandau
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i have heated grips on my /6- works fine. In my case I did not install them, so they are On unless you turn them OFF. which I would suggest not doing.. at some point i got to fix that.
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Old 11-28-2013, 03:32 PM   #11
blaine.hale
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Quote:
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Yup, stock 180 watt alternator.
Wow. That's the first time I've ever heard that.
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Old 11-29-2013, 09:10 PM   #12
Warin
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Quote:
Originally Posted by Singletrack_mind View Post
I'm wondering about buying a friend of mine some grip heaters

I'm thinking just basic stick-on heaters that go under the grips. In my experience these work fine. Current draw would be 2.5A on low and 3A on high.

should easily be an additional 3W in there I'd think,
Basic maths 3A * 12 volts = 36 Watts... not 3W

---------------
Would have thought heated grips would draw more power, maybe 3A each on high thus 6A total (72 Watts). I know my heated vest is 60 Watts max.
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Old 11-30-2013, 08:38 AM   #13
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They work fine. I would count on a 48 watt draw and wait to turn them on after the bike has been run above 3500 RPM's for a few miles ass the stock starter draws a lot. You could end up with a very week battery if you are just doing low speed around town riding with the grips on.
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Old 11-30-2013, 06:43 PM   #14
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Quote:
Originally Posted by Warin View Post
Basic maths 3A * 12 volts = 36 Watts... not 3W

---------------
Would have thought heated grips would draw more power, maybe 3A each on high thus 6A total (72 Watts). I know my heated vest is 60 Watts max.


Thanks for the correction. I am forever forgetful of the whole Amps/Watts/Volts relationship.

I took the amperage figures from the Rider Warehouse catalog, and it's my expectation that the amperage given is for the pair, since no one runs just one at a time (except my friend Dave, who made a burrito warmer out of one).

Given that your heated jacket is 60Watts, I find it unlikely that the two grip heaters combined would be 72W, which reinforces the assumption that they are 3A/36W considered together.

And for the other poster warning not to run them when using the starter or idling around town: Yes, good advice. Fortunately the friend who's bike these will go on lives somewhere rural, and pretty much every ride involves some nice long cruising at speed.
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