Geo Metro plug-in parallel hybrid EV - in progress

[Blue Bomber Man]

I need a little more information on the capacity of your batteries. Best way to give it is: Battery Ah and that Batteries Voltage, and the total number of batteries.

I need to do it that way so that I can find the total Watt-hours for the spread sheet.

[Blue Bomber Man]

So I crunched a few numbers:

A 2 kw-hr pack will get you about 9 miles.

I'm finding the spreadsheet doesn't like such a small battery pack. It's because it also matches up battery output with what is required to reach certain speeds. So I lowered the output requirements significantly without adjusting the capacity, but what it means for you is you need to make sure have a high enough discharge rate to get your vehicle up to a usable speed. Without a high enough rate you will not be able to go all electric.

[Coyote X]

If I had to guess I would say the batteries under heavy load would give me 75AH of capacity. Guess I will find out soon, the controller and charger came in today

This weekend I will start on mounting the sprocket and motor. Once that is in it won't take much to get it rolling hopefully.

[Blue Bomber Man]

If thats 75 Ah at 72V then you have 5400 Watt-hours. Could be good for up to 25 miles, not so bad if you ask me

[MetroMPG]

I was going to say, I can't believe how quickly this is coming together. But then 1) I only have my typically slow work speed to compare to, and 2) maybe in some ways it's easier to hybridize than to convert.

[Coyote X]

It is coming together quickly mainly because I am just throwing money at it

The only actual work has been to build some battery trays. Spring break is coming up soon and as flexible and as easy as the car is to modify I don't see why it can't be more or less working by the end of next week assuming everything I have works like I am planning.

On the controller it has some copper lugs sticking out to attach the wiring. I can get copper crimp on lugs to attach the wiring to them but I don't think using standard steel bolts to attach it would be correct. Is it possible to find copper bolts and nuts to get it all together?

Also at the parts store they have these big blade disconnect switches. It says 250A continuous and 500A max. Do any of you think that adding a couple of those inline in my battery bank would hurt anything? I am thinking of putting them on there with the old airbag impact sensors to trigger solenoids to kick them open in case of an accident. So 2 switches could cut the bank into three sections at 24V each and be a lot safer than a 72V pack.

[MetroMPG]

Why not use stainless bolts for the lugs? Corrosion wouldn't be a problem, and I doubt the conductivity difference would be an issue (all stainless bolts in the ForkenSwift's circuits). But maybe I'm missing something. You can get brass bolts if you want - Paul got some for his controller project.

Those blade disconnects may not be rated high enough. If you have a collision that dead shorts a cable, the current will be higher than 500A. But you'll also have a fuse in the pack right?

As well, I've read about some conversions using an inertia switch. Like this: Switch, First Alert Inertia, recycled . But it still requires a main contactor or knife switch setup like you're imagining.

[bennelson]

Rather than getting all complicated with solenoids and airbag sensors, just use a contactor.

Beefy contactors are rated for high amperage and already are remotely operated switches. Put an inertia switch in-line with the power to the coil of the contactor.

If you smack into something, it will kill power to the coil, and the big springs pop the contactor open, killing all power on your EV circuit.

You could even get a fancy contactor that would have 3 seperate connections on it (each isolated from each other) and snake your battery cables to it. Then anytime the contactor is disengaged, your battery pack would be broken into three parts.

I was thinking about doing something similar to that to break a 144V pack in half for 72V charging.

[Coyote X]

I planned on putting a fuse right after the 72V terminal just in case of a short or something. I was thinking the blade switches might be good since they for the most part would never be used and I was wanting something that would be really reliable and could be operated by hand if the need arises. Maybe just putting a fuse after every other battery would work and not bothering with making it overcomplicated.

Contactors might be the best option. Where can I get a good one at? I didn't see much point in using one and also a fuse since I doubt it is possible for the three phase controller to stick wide open and even if it did the brakes can handle it considering the gearing.

[Blue Bomber Man]

Could just find a relay that is rated for the amperage/voltage you are running and have it triggered by something of lower power demands like a light duty switch.