Thursday, December 1, 2011

Preliminary semi-scientific conclusions

If you're new here, this post won't make much sense unless you read the previous post, and be warned, that post might not make much sense at all.

Oh well! That's life, so here, in as coherent a fashion as I can muster, are my conclusions.  I have the generous assistance of CircleBlue, BobSkoot and Brady Steffl, both on and off this blog, to thank for allowing me to get this far:
  • The Vespa LX 150 has a 12 volt electrical system that reliably (so far) generates at least 7.5 amps of electrical current at 3,000 RPM.
  • The total load of electrical bits and pieces that come with the stock Vespa LX 150 draw 7.27 amps.
  • That means that the Vespa LX 150 is designed to operate with a mere 0.23 amps left over to charge the battery.
  • The normal running electrical draw of the stock Vespa LX 150 is 3.85 amps.
  • Oxford heated handlebar grips consume 3.6 amps on average.
  • The normal running electrical draw of the Vespa LX 150 with Oxford heated grips in operation will be 7.45 amps, leaving 0.5 amps of electrical head room.
  • That 'head room' means that the Vespa LX 150's electrical system is able to deliver all the power needed to run the scooter, and run the heated grips, without drawing additional current from the battery.
  • The battery in the Vespa LX 150 is a 12 volt 9 A-h lead acid battery with a charging rate of 0.9 amps.
  • The trickle charging rate for the Vespa LX 150 battery is 0.03 amps.  This means that a charging rate of 0.03 amps is sufficient to keep the battery topped up if it's got a full charge.
  • With the Oxford heated grips running, the battery won't be draining, and there will even be 0.05 amps available for trickle charging the battery, which is more than the 0.03 amp trickle charging requirement for the battery.
My conclusion is that the Oxford heated grips work with the Vespa LX 150, but it's theoretically tight in terms of the electrical budget.

I think that in a real-world application, for the way that I run my Vespa in the course of a one hour commute each way to work, the Oxford heated grips will do just fine, and that the electrical budget won't be nearly as strained as the analysis to date would show.

For instance, I would expect either to run them at the low range of the settings from the beginning to the end of the commute, or wait until I feel a little chilled, and then run them at a higher setting only until I get the chill out.

Running the grips at 30% capacity will consume 1.08 amps of current, increasing the head room to 2.57 amps left to charge the battery, which is only 1.08 amps less than the stock bike's excess capacity, and a lot more current than the 0.9 amp normal charging rate of the battery.  Running the grips on the highest setting for the coldest twenty minutes of the commute would yield a similar result leaving 2.46 amps of headroom.

The worst case scenario would be running the grips on high from beginning to end of the commute.  In that case, there are times when the bike would be idling and producing less than the 7.5 amps of maximum current, and it is likely that for those portions of the commute there would a power deficit that would be draining the battery.

After a morning commute with that kind of brutal punishment, I still think that what battery drain would have occurred have still have been marginal and that the bike could start up for the evening commute.  After a similar evening commute, plugging in the battery tender at home would top up the battery and set the bike up for another such brutal commute the next morning.

What I don't think that the bike could handle would be a long distance cold weather trip with the grips running on high morning to night.  Although, even then, the likelihood is that the bike would be mostly running at high RPMs and the battery might just hold up fine.  As long as the high beam wasn't also on, and the GPS wasn't hooked up... and that's not likely to happen.

If I make that kind of trip, it'll be a mid-summer adventure.


Unknown said...


Your grips will come in handy even during the summer. On our long ride to Bend, OR in 2010, My riding partner was SonjaM and we left Toppenish at 6am heading south towards Bend, OR. Even though the daytime temps were around 100°F it was very cool in the morning and I had to turn the Grips ON. I never said a word but later when we were stopped for a rest break Sonja mentioned that she also turned her grips on.

another thing you should consider is a heated vest. don't get the fancy one with miles of wire, but the cheaper one which uses less AMPS and wire it up with a double pole, double throw switch. Sort of like a HI-OFF-LOW, 3 position. You may as well do this NOW which will save time later. Hook the heated grips to one side, and the heated vest to the other side. Remember that OFF is in the middle position. This will prevent you from having both ON at the same time and fry your electrical system. IF you want GRIPS you flick UP, and when you want VEST you flip down. Heat doesn't disappear instantly, there is some heat retention so could flip it back and forth to maintain your desired temperature.

Riding the Wet Coast

Unknown said...

David, it sounds like you've got this pretty well sorted out. I suspect that you'll rarely ever use the high setting for any real length of time - I have four settings with my heated grips, and the fourth turns my hands into a sweaty mess.

Cool, though, post your progress, I love DIY motorcycle projects. They're half the reason I love bikes as much as I do.

Behind Bars - Motorcycles and Life

Unknown said...

David, one more thing:

As you seem like the thinking-man's rider, I'll add you to the list of blogs I'm following and blogroll. Not many people would attack a problem like this in such a systematic way.

Behind Bars - Motorcycles and Life

David Masse said...

Bob, that's good advice. I now think that I'll do at least one more season with the LX 150 and so heated grips are a definite go. When I do trade up, some lucky person is going to get a very, very well-equipped Vespa LX 150.

Brady, thanks for the vote of confidence. I have similarly linked to your blog and am following you. I like your writing style and am really enjoying your blog. Keep'em coming.

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