Ben Nelson's Electro-Metro Build thread

[trikkonceptz]

Originally Posted by Daox

I recall reading that some guy was using a water bed heater to heat his battery compartment.

That could work, I recall those buggers get hot .. not to mention have the dial type thermostats which could regulate the temp if need be .. However would the additional drain on power be worth it?

[Christ]

Paul - I'm going to stick my neck out here and say something as I understand it... I might be wrong though.

Advancing the brushes in the motor has to do with the timing of polar transition, relative to the position of the armature... if the armature is spinning really fast, the transition of the polarity of the brush has to happen sooner, so that the momentum of the armature pushes it past the brush as it's reached the new polarity (think: signal latency)

It seems kind of like ignition timing in a ICE - you want to set the timing so that it begins the combustion process as the piston/crank is within X degrees of TDC (depends on engine specs for actual timing) so that it's reaching "critical mass" as the piston/crank is several degrees past TDC (dwell time) to create maximum power from the available expansion of gasses.

That said - You would want to "time" the latency of the signal process when changing the polarity of the brushes so that each polarity transition occurs as the armature is just passing the brush, so that part of the armature's momentum isn't used against the magnetic force...

ideally, you could change the "timing" of the brushes to alter the torque/speed profile of the DC brush motor.

IF YOU'RE NOT FAMILIAR WITH ELECTRIC MOTORS, AND YOU'RE READING THIS FOR EDUCATIONAL PURPOSES, PLEASE DO NOT READ TOO FAR INTO THIS POST. IT IS TO BE CONSIDERED PURELY SPECULATIVE, AS I OPENLY ADMIT THAT I HAVE ABSOLUTELY ZERO IDEA WHETHER IT'S CORRECT OR NOT. I WILL NOT BE HELD LIABLE IF YOU FOLLOW MY INFORMATION AND BLOW SOMETHING UP. BE WARNED.

[MPaulHolmes]

I think you are right, Jesse!! (fast and the furious! was that his name?)

[Christ]

Yeah, that's his name.. that's the right movie.. and "D'oh!" :hits head:

Did I get a new nickname? LOL.

[Tango Charlie]

Your explanation sounds plausible...Jesse.

[TheSGC]

Ben, what was your range before the cold?

I am now doing range tests using my PakTrakr and found that a cold pack gives me 11 miles range according to the PakTrakr. It was 25F out and I only drove 4.9 miles and the PakTrakr read 56% left. 25-45 MPH, hills and stop and go. Now two weeks ago it was 60F, with a fresh charge and I did a 1 mile drive and the voltages indicated a 33 mile range. I didn't have the PakTrakr at the time so I don't know how accurate the estimations are.

Just for comparison, I have a 96 volts system using 12v 125Ah batteries.

[bennelson]

On my 72V system of 6 95Ah gel-cell batteries, I could do just under 20 miles in the summer.

My most recent "cold" trip was 9.2 miles, and that was pushing it!

HALF the range with lead-acid gel-cells in the cold!

[TheSGC]

Originally Posted by bennelson

On my 72V system of 6 95Ah gel-cell batteries, I could do just under 20 miles in the summer.

My most recent "cold" trip was 9.2 miles, and that was pushing it!

HALF the range with lead-acid gel-cells in the cold!

Just under 20 summer miles with your pack is pretty nice. 6.8 KWh of power, plus Mr. Puekert and 20 miles sounds right on.

Yeah, this cold really bites! Are you using voltage to measure your Depth of Charge? I have been told that using voltage DoD is only accurate at least an hour after your have driven/charged the EV.

Now I must get back to building my insulated battery box and fight this cold!

[MetroMPG]

Originally Posted by TheSGC

Just for comparison, I have a 96 volts system using 12v 125Ah batteries.

Do you have an EV Album entry? (Sorry if I just missed it.)

[bennelson]

Other EVAlbum entries:

Ben Nelson's 1996 Geo Metro - Electro-Metro
Darin's 1993 Geo Metro ForkenSwift - Forkenswift