Ben Nelson's Electro-Metro Build thread

[vinny1989]

Does the charger controller etc not need moving air around it for cooling?

A few vents on the vertical section hiding them, and a few computer brushless fans could keep some air circulating.

Looks good, hides parts and is also functional.

[bennelson]

The charger has a fan built into it.

There is quite a large amount of space in the "hidden compartment" and it's not sealed off right now, so air isn't an issue.

Once everything is sealed up and finished off, I will check it after doing a charge, and see if it's warm in there. I don't think it will be. If it is, I can always add a small fan like you said.


The Open Source Controller (the Cougar) arrived in the mail today.

I replaced my Curtis controller with the new Open Source controller. It's a little bigger, so I had to jam it down into the car a bit more to be able to close the hood.



The controller works great, although there is a small "shutter" when trying to pull away at really low speeds. That will be solved in version 2 of the controller.

The acceleration and speed with the 144V controller is better, but I am still trying to take things slow and test things before going really wild with them. Expect a full-blown test of the controller in a few days. (I still need to install the parachute brake!)

Also, having a 144V battery pack, and only a 72V charger is a bit of a bother. I have a connector to make a quick disconnect for an A pack and B pack, but I have to do some re-wiring to make it all work.

[Christ]

Ben, is there any way you could make a switching setup that would just convert your 144 to 2 parallel strings of 72? (So you could just flip the switch, and plug in one wire, so you could charge your packs without having to do it one at a time.)

Then, the next time you need the car, you could just unplug, flip the switch, and be ready to go!

[MPaulHolmes]

That's a really good idea! They do it all the time with buddy pairs of 12v batteries.

[bennelson]

Originally Posted by Christ

Ben, is there any way you could make a switching setup that would just convert your 144 to 2 parallel strings of 72?

I have thought about that.

The trouble is that they need to be very BIG switches. Switches cost money and take up space.

The double-action contactor I used for the "turbo" circuit would work well.

Hmmm... I have to figure this all out on paper.

[MPaulHolmes]

Wait! Couldn't it be a little baby switch? It would never be closed when at 144v. When it's open, the car is 144v, and closed, at 72v. That way, when you are charging, the switch just has to handle like 10 amps or so, and when it's open, the monster current would be not going through the little switch. I haven't thought it through very well, but it might be true?

[bennelson]

To switch the whole pack from one 144V series string to two 72V series strings run in parallel, I need 3 connections.

1 very big powerful connection in the middle of the pack that connects the two 72v strings together in series for running, and disconnects them for charging.

Then I need 2 connections are that disconnected for running and connected for charging. They only need to be able to run the current of the charger.

Rather than finding a bunch of switches or contactors, I already have a few spare Anderson connectors. Each connection connects/disconnects two cables at a time.

That means that I can use my existing beefy main battery disconnect as the "middle" connection that breaks the pack in half.

I can use a smaller Anderson disconnect (using both cables running through it) to connect the two ends of the battery packs to connect the two 72v strings together in parallel for battery charging.

The only downside to this whole thing is......DON'T HAVE BOTH CONNECTORS PLUGGED IN AT THE SAME TIME!!!!!

That said, guess what I just did by mistake.....


Glad I didn't pay too much for the batteries!


The good news is that I am just fine! Plywood is great at preventing splattering molten battery post!

[TestDrive]

Glad you're OK.

Is there a way to make the mistake non-repeatable? - Tape one of the light duty connections to a heavy duty cable such that it's not possible to have both circuits connected at the same time?

[MPaulHolmes]

Molten battery post? Holy cow! I'm glad you are OK, Ben! How many posts are bad?

[bennelson]

I like the idea of hooking the connections up so that if you even TRY to plug in the one set, it unplugs the other.

Only the one battery post got fried. The next one up from it also took a hit, but there wasn't any arcing between the post and nut, so it was able to come back off again.