Minimum Charging Voltage - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
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post #1 of 12 Old 10-07-2006, 10:34 AM Thread Starter
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Minimum Charging Voltage

Can any of you electrical gurus tell me what absolute minimum voltage is required to keep the battery charged while riding?

I just installed the Dual Star heated grip kit and with my digital multimeter hooked to the battery in the tankbag mapcase, went for a ride to check the battery voltage under different load conditions. With the max load I could put on (heated grips on high, Gerbings jacket liner on high, high beams on), the battery voltage was hanging right at about 12.8 volts while running at 5k rpm, which I understand is where max alternator output occurs. With no extra load at all, the voltage hangs around 14.4 volts at the same engine speed.

I leave my house at 4:10 am every morning for my 58 mile one-way commute, and when the temps dip into the 30s I'll be running all the electric gear on high along with high beams for most of the trip. Of course, the high beams will go off occasionally when I encounter the normal sparse traffic and that will allow a bit more charging (high beams took about an extra .3 volts according to my multimeter). Switching off one headlight at this time of the morning to gain more voltage is obviously not an option for me.

Voltage load was never a concern before on my BMWs with their 700 watt alternators, but as I've since moved on (up? ) into the Strom world I'd just like to be sure I don't kill my battery during my commute and leave myself stranded.

Thanks!

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post #2 of 12 Old 10-08-2006, 08:15 PM Thread Starter
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OK, I think I found the answer elsewhere. If anyone else is interested: Two of the battery monitor LED indicators that I've seen on the market give a green (positive charging) signal at or above 12 volts even. In the high 11s, you get a yellow (cautionary) light, and mid 11 volts and below is red for "Yer battery's gettin' ready to die, sucka!".

Looks like I should be just fine running my Gerbings and heated grips on full along with high beams in those cold, wee hours of the morning.

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post #3 of 12 Old 10-09-2006, 10:56 PM
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Thats curious. I have a datel voltmeter installed on my 05 650. I get 14.7 at 5k rpm with no extras turned on. If I turn my grips (dual star) and vest(cheap generic) on full the meter still reads 14.2 The high beams don't affect that much either, maybe .1 of a volt.
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post #4 of 12 Old 10-10-2006, 09:45 AM
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A fully charged battery (ign off) will read 12.6 volts. If you're reading 12.8 volts with everything on you've pretty much maxed out the capability of the alternator and may be in danger of "burning" the stator because it can't cool itself fast enough. The heavier the load, the hotter the alternator gets & heat kills. I'm never comfortable with the voltage dropping below 13.0 volts.
I've been in the automotive, industrial, marine and RV alternator & starter rebuilding business since July, 1983.
Maybe by turning off "momentarily" one of the heating devices your charging system will "live" longer.
Hope this helps, and you're right. The Vstrom's alternator is really too small for the added equipment needed to do year round longer distance riding.

Grandpa

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post #5 of 12 Old 10-10-2006, 10:00 PM Thread Starter
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jrw - I'd venture to guess that your heated vest draws substantially less current than my Gerbings liner. The Gerbings takes 77 watts, and I think my old Eclipse heated vest only drew 35 or 40.

grandpa - Thanks for the info about the stator heat. I don't suppose the fact that the ambient air will be in the 30s (which is exactly why I need all that heat!) will keep the stator any cooler, will it? I will be cycling the high beams on and off as I encounter the occasional car, but I'll most likely be at max current output for most of the trip. Maybe I'll just have to keep the grips on low and hope for the best. I'm also thinking that I should replace the standard taillight/brakelight bulbs with LEDs to lower their current draw so I have more to keep me warm.

This bike is so perfect for me in every other way, pretty disturbing that it's capabilities are limited by something as simple as a wimpy alternator. The one on the KLR is even worse, but not by much.

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post #6 of 12 Old 10-11-2006, 09:50 AM
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Anything you can do to keep from maxing out the alternator will help it "live". The 30 degree temp is not all that great because the alternator doesn't stick out in the air flow like that on early model Guzzi's, so heat is "trapped". 15 minutes at high load and 10-15 minutes and lower demand shouldn't hurt the alternator.

Stay warm, cold hurts.

Grandpa






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post #7 of 12 Old 10-11-2006, 12:36 PM Thread Starter
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Thanks for the follow-up. At least I have a little peace of mind now, Grandpa (why do I feel that you ought to be bouncing me on your knee while we discuss this???).

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post #8 of 12 Old 10-11-2006, 06:17 PM
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alternator mods?

Does anyone offer alternator mods to increase output? I know baja designs and others can increase the output of many dirt bikes. Might be worth checking into for many of us with the same concerns.
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post #9 of 12 Old 10-11-2006, 07:15 PM Thread Starter
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DrDale - I've seen that discussed a few times on various other threads, that some company was "looking in to" making a higher output alternator for the Stroms. I've never read where a product is actually on the market yet though. If someone makes one and it works well, I'll be one of the first in line.

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post #10 of 12 Old 10-13-2006, 08:22 PM
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Here is some info I found on alternator output from Powerlet: Not much margin for error with the V-Strom.

http://www.powerletproducts.com/docu...scapacity.html
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