Geo Metro plug-in parallel hybrid EV - in progress

[Christopher Jordan]

Originally Posted by brihoo2k

Just a thought but how about going with a belt configuration like a cvt (constant variable transmission) you could possibly rob one off a snowmobile. I myself would not consider the size 40 chain

My 'El has a higher ratio and a poly-vee belt (former owner wrote this):
Chris Jordan's CityCom CityEL
but the newer 'Els have a chain. I have no idea what a Metro conversion would use.

[Coyote X]

I guess a rename might be in order. It would save me from actually starting a new thread

I am putting the sprocket on the axle about an inch away from the CV joint so it gets very little movement. From full extension to full compression of the wheel is about an inch of movement at most at that point. The suspension droops a lot more than it really should with the cut springs so I will be putting limiting straps on it anyway. right now with the wheels hanging in the air the springs could possibly fall out. So fixing that problem will make the sprocket movement pretty small.

I really don't like the idea of using #40 chain for a car. It just seems small.

ANSI 29.1 roller chain standard sizes
Size 	Pitch, in. 	Roller diameter, in. 	Ultimate strength, lb. 	Working load, lb.
25 	0.250" 	0.130" 	781 	140
35 	0.375" 	0.200" 	1,758 	480
41 	0.500" 	0.306" 	1,500 	500
40 	0.500" 	0.312" 	3,125 	810
50 	0.625" 	0.400" 	4,880 	1,430
60 	0.750" 	0.469" 	7,030 	1,980
80 	1.000" 	0.625" 	12,500 	3,300
100 	1.250" 	0.750" 	19,531 	5,072
120 	1.500" 	0.875" 	28,100 	6,800
140 	1.750" 	1.000" 	38,280 	9,040
160 	2.000" 	1.125" 	50,000 	11,900
180 	2.250" 	1.460" 	63,300 	13,700
200 	2.500" 	1.562" 	78,000 	16,000
240 	3.000" 	1.875" 	112,500 	22,250

810lbs working load probably mean at best I will get 10,000 miles on a chain before it breaks. If I can get a #50 chain that will make it much better but the only way to do it would be to add a gear reduction shaft and that means more parts and more points of failure.

from a web search.

530 chain has a pitch (distance between center line of rollers) of 5/8". The roller diameter is .400" and the width (inside distance between plates) is 3/8". #50 chain has the same specifications. An O-Ring 530 will be wider #50 and 530 chain are the same in dimensions. #50 is the ANSI industrial chain designation while 530 is the motorcycle industry designation for that chain. Both have the same specifications and can be used in place of each other (other than the 530 will be slightly stronger in regular chain and much stronger in the o-ring version).overall, but still has the same critical (roller, pitch, and inside width) dimensions.

So I really need to use #50 sprockets so I can use o-ring chain like I was planning. It will last much longer. Standard Roller Chain Sprocket Diameter - No. 50 Chain shows the diameter and I have a 3.75" max radius without grinding a notch into the control arm. I might possibly get 4" if I grind everything down. If I could possibly get an 8 tooth front sprocket then it would work great. If not I will have to build a shaft to do my gear reduction. I guess I need to hunt around and see what I can find. I have a week or two before spring break so I have time to look for stuff.

[Coyote X]

From fremont supply:



That will get me a 3.92 gear ratio. I would put the 22 tooth gear on the axle. It is 4.722 inch diameter so it clears everything fine. And put a shaft somewhere using those 2 bearings and a 14 tooth gear paired with the 22 on the axle. Then put a 30 tooth gear on the mid shaft and a 12 on the motor. That won't be an ideal setup but it should work and make changing the ratio a bit easier by just swapping gears on the shaft. This is very close to where 3rd gear is in the car right now so it seems about right. The only bad part is it is going to take a lot more fabrication to get that shaft fit in there somewhere and adding a lot of extra crap under the hood and be a lot more work and expense maintaining it in the future.

The best I can do with a #50 chain direct drive with no mid shaft is a 10/36 gear set so that gives me a bit lower motor RPM but I am not sure if it is good enough to actually work. It would be much cheaper and simpler since it does away with the extra shaft and assorted mess that goes with it. It would just be the 2 gears and a chain.

at 3.92 here is my rpm/mph
rpm	288	576	1151	1727	2303	2878	3454	4030
mph	5	10	20	30	40	50	60	70
at 3.6 here it is
rpm	264	529	1057	1586	2115	2643	3172	3701
mph	5	10	20	30	40	50	60	70

I have no experience at electric drives but I really can't see how 24 RPM at 5mph is really going to matter that much to the current draw pulling out from a stop.

Also I measured a stock framed metro and a 36 tooth gear will fit the axle without any real trouble, just a dent in the control arm mounting area for clearance. So if the 3.6 or 3.4 ratio is good enough then pretty much anyone could add an electric motor to their car real easily. A kit could be fabricated that would consist of an axle that has the keyway cut into it and a bracket set for the motor. Probably a couple hour job to add to any Metro.

[Coyote X]

Interesting charts on that motor running at 48v and 72v





From the thread where I found those charts at:

The X axis of these motor dyno charts is almost always torque, as the way they're tested is to have the motor drive an increasing load (i.e torque) and measure how the rpm/volts/current/etc changes.

In this case I believe the x-axis units are inch-pounds, 1 in-lb = 0.113 Nm. This would make sense with the Watts Out curve where take the 160 in-lb mark for example = 18 Nm, x 2500 rpm / 60 * 2PI (converting to radians per second) -> power of 4716W, looks about right on the Watts Out curve.

Edit: Interesting though that the amps and inch-pounds happens to be pretty much 1:1 - coincidence I suspect, but hard to fault Electrocycle's assumption! (Being a permanent magnet motor, it has a constant amps to torque ratio.)

So That means I would lose 8% of my acceleration rate going from 3.9:1 to 3.6:1 assuming I am accelerating at the current limit of the controller. That chart is very hard to figure out what they are talking about so I could be wrong I think I will order the 10/36 gears and mount them. Trial and error is a lot more fun than research.

[Coyote X]

Found a better selection of sprockets. They are at Shoup Manufacturing Company I ordered #50 sprockets. I got a 9 tooth drive gear and a 32, 34, and 36 tooth driven gear. They are the weld on hub type so I also got an X series 7/8 hub for the axle and a V series 7/8 hub for the motor. The available gear ratios with those driven gears are 3.55:1, 3.77:1 and 4:1. That should pretty much cover any range I need keeping my 4000 RPM limit of the motor.

Now that that part looks like it is pretty well settled it is time to move on to the next part, the controller and batteries. I don't think the Mars brushless motor can take much more than 72V and still have a long life. So I am not really sure I would ever use more than that. I could always modify the controller to boost it's output if it ever comes up I suppose. So the 72V 300A w/regen controller looks like my best bet.

For the batteries it looks like it is ideal to charge them individually. That is not hard really if I just use 5 or 10 amp automatic chargers, it would just be a mess of wires and crap to hook up all the time. Another simpler option is to charge them with one 72V charger and balance them using a balancer of some sort The Balancing Act | ELECTRIC-LEMON shows a pretty simple circuit to balance the batteries over time. That should get them charging and working as long as possible. The fun part is trying to figure out what kind of battery to use. I planned on using AGM-31 but I really don't think I can fit 6 of them in the car and still have room for anything else, they are pretty big batteries and heavy. I don't really think I need that much capacity anyway. I can get a MK 8A24 79 Ah (20 Hr) AGM Sealed Battery - Batteries: Sealed Agm @ AltE 79AH battery that looks like a good size to cram in corners in the car. 6 of those would be a lot lighter at 50lbs each. I am not sure what kind of range it would give me though.

Anyone know of a better battery to use?

[bennelson]

I think any AGM battery would be a good bet for a hybrid.

The Optima Yellow Tops on my motorcycle have worked well. I have heard of some other people say they ran into quality issues with Optimas, but mine have been great.

You could also use a charger like this for whatever you end up getting.

SE-1072 - Schumacher Chargers - 877-746-2288 Live Help

It's pretty reasonably priced as far as multi-battery chargers go.

[Coyote X]

Is that a battery in your pocket or are you happy to see me?



Ended up going in a completely different direction Got batteries from Walmart of all places. They are deep cycle/starting batteries rated at 125A. I figure under heavy load it would be more like 50AH but for a 60lb battery that is $67 they aren't bad. I only got 4 of them, the other 2 will have to wait for more to get back in stock. I can fit 4 in the trunk and 2 behind the seats in battery boxes. Going back to uncut rear springs will get the ride height back to what it is without batteries. This setup should last me a year or more, at least until LiFePO4 batteries get a stable price and good availability.

So now I am just waiting for sprockets to come in and I need to finally order a controller. I am still leaning towards the 72V model since from trying to stuff batteries in there I really don't think it is possible to get 10 of them in the car without serious modifications. I might go ahead and order everything since I have one more week of work until spring break. That would give me a lot of time to do everything to the car at once.

[MetroMPG]

Thread title changed. Let me know if you want something different.

A kit could be fabricated that would consist of an axle that has the keyway cut into it and a bracket set for the motor. Probably a couple hour job to add to any Metro.

I like the sound of that.

Way to grab the bull by the horns on this.

[roflwaffle]

Are you attaching the sprocket to the axle hub or shaft? I've been thinking about doing this for a couple years too but the shift linkage is in the way on one side and while the other side is doable if I went to manual brakes, something I was planning on doing anyway, it's right next to the exhaust manifold which probably would require a heat shield and funky electric motor mount. My pickup would be easier since I could just shorten the driveshaft and put a double shaft motor inline, but since it has to be smogged I have to get it legal somehow and the PR person I talked to at CARB was a total bonehead.

[Coyote X]

I am putting it on the shaft. There is room beside the transmission with the 3 cyl to run the chain up to where the motor will be sitting.

The 72301 controller is on its way. I went ahead and ordered the 72V 8A charger they have. I picked up the last 2 batteries today also and got a pair of battery boxes for the batteries that go behind the seats. So hopefully next weekend I can start installing everything. The sprockets have also came in. I have a 9 tooth drive sprocket and 32, 34, and 36 driven sprockets. The last thing I need to find is some welding cable. I am thinking for 300 amps I probably need 2 gauge minimum. 0 if I can find it. 4 gauge is probably good for going from the controller to the motor depending on the distance. I also need to order the parts to build a battery balancer and the stuff to modify the alternator to make it output 14.4V or 86.4V depending on what I want to charge.

The instructions for the controller leaves out a few details. Like do I need to ground the 72V to the chassis or leave it floating and just connect it directly to the controller only? And is it better to put the controller close to the batteries or closer to the motor? I could easily fit it in the trunk but if it is better near the motor I could make room for it under the hood as well.

On ebay I could get 3x6 solar cells 1.75W each. So with 200 of them I could get a few amps of charging. It would peak at 4.5A@72V. So if the car was parked outside with partially discharged batteries for a while I might get enough charge to get a few more miles out of it. I am really tempted to try that out after I get this electric drive working. It is another one of those things that won't pay off in saving money but it would be really cool to have on the car.