Ben Nelson's Electro-Metro Build thread

[LostCause]

You and MetroMPG are beginning to inspire me with your cheap, backyard electric conversions.

Originally Posted by Nerys

Just how many amps would I need to go 60 miles? How do I do such math? I am tinkering with the idea of using NIMH batteries specifically 10 or 12 amp D cell NIMH's ie 600 cells would give me 72volts and 100amps. With nimh I can use ALL of the power no 50% usage limit as with Leads. Then the other question. How the the heck would you charge 600 cells :-(

You can do some basic sizing by using thse excel spreadsheets from Don Cameron's website.

60 miles @ highway speeds is in the realm of advanced EV technology. If you want to use a donor car, you will probably need a high voltage AC drive system and a lithium ion battery pack. To build a car around this technology will probably cost you $30-40,000, not the $1000 DC conversions that are popular. You might be able to use a truck w/ DC technology, but it would be close. Also, it will take ~6-9 hours to fully charge a depleted car...sucking massive amounts of energy while doing so.

NiMH cells are pretty rare beyond the Prius and very few "smart" chargers seem to exist for the technology. I think Ovonics (GM) bought up all the patents for large scale NiMH's and stamped them out of the market place.

[Ryland]

I would NOT use "D" cells to power a car, I tried that with my electric bike and it failed, wired up a string of 30 to get 36V and 10amp hours, the 20 amp draw that it takes to go up the driveway really heats them up and drains them down really fast, if I'm carful I can get about 6 miles out of a charge with them because they don't react well to the high discharge of a motor.
One of the other people with a Citicar said they figure they use 250 watt hours per mile, and that is with a 35mph top speed, a single "D" cell is 1.2V and if you get 10amp hour then you have 20 watt hours per cell, so at higher speeds could you use 500 watts per mile? so 25 "D" cells per mile, or 1,500 of them to make a 60 mile trip, just remember "D" cells don't like to run large motors.

[dremd]

I use D's on my bike, works fine. I can get 15 miles without pedaling at 13 mph (how fast I can pedal continuously) More like 6 at 20 mph without pedaling. With pedaling (heavy, but far from max) I can do 24~26 mph and get 22 miles (drooping towards the end of the pack)

However I WOULD NOT use them to power a car (excluding streamliner single seat extreme efficiency type thing.).

Figure max 10 amp discharge rate MAX through most of the cycle I have around 7 amps max.

[LostCause]

For what it's worth, "D-Cell" just describes the packaging size, not the capability of the battery. The Honda Insight uses industrial grade D-size NiMH batteries, which are quite a bit different then the stuff you can pick up at the local store.

- LostCause

[Christopher Jordan]

Originally Posted by bennelson

Old VWs are very popular for electric conversions.

Speaking of old VWs-
http://www.santacruzsentinel.com/ci_9129186

Now for an old Aspire Gas was $4.03/gal when I filled up yesterday Decided to get new tires for my trikes and park the Aspire for a while. If I could electrify it overnight; I sure would!

I went back to check out that Zap truck again- found out it went up in price an extra $900. in -1- month. (sob) Decided again I still do not want it.

countersTrike

[Nerys]

Well also remember I was talking about a 100amp pack thats TEN sets of 10amp D cells so each string would only have to absorb 1/10th the total load. WELL within the draw capacity of good quality cells. if it were not for the "quantity" I would need and therefore the cost I would use RC grade SUB C cells which can handle a wacky ton of amps without breaking a sweat :-) but that would double the size of the pack and therefore double the cost.

[WaxyChicken]

There IS a drawback with using smaller sized batteries of any type -
more weight is in the casing to energy ratio.

for example: 10 D size batteries weigh more in casings, wirings, and solder than a single 12v's casing of the same battery type.

So it's not just finding the proper charger and controller, it's also finding a large enough battery to use.

[Nerys]

Well thats the crux of the problem. With Chevron's actions its illegal for me to have larger batteries (ok there is one slightly larger but the cost of this cell is so much more than the D cell its not worth it and would NOT appreciably reduce the number of cells I would need but would quadruple the cost.)

Well there is no "larger" nimhs for all intents and purposes that I am permitted to purchase. so its D cells or no NIMH chemistry sadly.

The issue is "CAN" it be done. if an effective way can be found to charge them affordably I would like to at least try. Small scale first off course.

The advantage of nimh is I can use almost ALL the capacity (50% of the mass of leads is dead weight because you can not go below 50% capacity without gravely harming the cells. Nimhs do not suffer from this.

Nimhs will also last a lot longer. SO the time from pack to pack replacement will be a lot lower.

It also means I can buy in lots and slowly upgrade the pack.

I m just trying to find out if it CAN work. IE what kind of amps to I need to move say 3000 pounds 60 miles on typicaly relatively flat terrain with an average speed of 45mph.

I have no idea how to figure this out.

[bennelson]

I talked to a machinist on the phone tonight.

I am going over to his place sometime Sunday to take the Metro trasmission and motors to show him what I am thinking for attaching the two.

Hopefully this guy will have some good ideas and charge a reasonable rate.

I always knew that getting the coupler and mounting plate done right would be the most complicated part of this. That is to say, something I wouldn't be able to do all by myself for cheap.

Once I get the motor plate and coupler, I should be able to keep chipping away on all the other parts of the project.

[MetroMPG]

I might be able to help you save a few bucks on the lovejoy+clutch hub input shaft side, if that's the route you're going to take. That specific part was done gratis for us by a friend of Ivan's.

The machinist did the other half of the lovejoy for us - where he cut & welded in the stub shaft.

Edit: but if you've got a normal motor shaft, you may not need anything fancy on that side of the lovejoy.