Ben Nelson's Electro-Metro Build thread

[MazdaMatt]

Damn, i was thinking at the start of your thread regarding not liking the current brake setup that you were going to explore the non-assisted brake route. Got my hopes up.

So how does it work now? Your pump ALWAYS pumps? or only when you are on the brakes, or what?

[bennelson]

Right now, the vac pump goes to a vacuum bottle, then to the brake booster. The vacuum bottle can hold enough for up to ten pumps of the brake pedal.

I had the vac pump rigged up to the brake light switch through a relay, because it was the simplest, cheapest way I could think of to do it.

The vac pump would run whenever my foot was on the pedal.

I finally found a good place to order a vacuum switch from. It just showed up in the mail today. Maybe I can get a few minutes to see about installing it tomorrow!

[MazdaMatt]

Sounds solid. Good luck.

Now that you've got the most efficient setup with boosted brakes, be sure to measure your amp-hours going to the booster. If the numbers are small, you're set, but you may find increased range with non-assisted brakes.

[bennelson]

I really don't have a good way to measure the amp-hours of just one particular 12V device. I don't think the pump is going to pull too much power.

Currently, everything 12v just runs directly from the 12v battery, with no dc/dc converter connecting the traction pack and the 12v accessory battery. So, by not using the pump at all, wouldn't gain me any range. It might make my headlights run a tiny bit longer, but thats it.

[bennelson]

I finally installed a vacuum switch to run the power brake system.

I shot video of the installation and will do a video about it next week.

Basically, the vacuum switch turns the pump on and off (but only when the key is in position) to keep vacuum in the vac flask up to a pre-set amount.

If the vacuum drops below that, the pump turns on to bring the vacuum back to that number.

Right now, I have it set to run the pump if the vac gauge reads below 10. For example, right when you turn the car on, the vacuum automatically powers up from 0 to about 12. Then, while driving, it will always return to 12 anytime it drops below 10.

[Daox]

Sounds great. What else do you have planned for the car then?

[MetroMPG]

Cool - another task done.

I think that's why it's fun working on a project like this - all the discrete mini-projects along the way.

[bennelson]

When I installed the vac switch for the power brake system, I did the how much power the pump uses.

It pulls 1.8 amps at 12 volts. It runs for about 2.5 seconds every second time you hit the brake. I don't think that adds up to a lot of power, and sure seemed a lot easier than swapping out a master cylinder.


Also, when I was over at Rich's working on the Citicar, he gave me a pair of "tow-tabs" for the Metro.

He wasn't sure if they were for a Saturn or a Metro, but they were kicking around a long time, and he gave them to me.

It looks like they will fit. These are chunks of metal that get bolted up in the front bumper so that you can attach a bar and flat-tow the car behind a truck.

Rich also mentioned that I will need to add those magnetic lights to the top of the Metro when towing it, but a slick mod would be to pop the tail lights open, and add extra bulbs. Wire those up to a 4-prong flat trailer plug in the front of the car, and plug in the car the way you would a trailer.

Then, the car's "original lights" would act as trailer lights!

I still don't know if those are the right tabs or not. I will have to take off the front bumper to find out for sure!

[Tango Charlie]

Using the stock lights is a clever idea. Always thinkin', aren't ya?

Is this so you can tow the Metro to shows/meets? What are you going to tow it with, the S-10?

[bennelson]

Yep, the plan is to be able to transport the car to auto shows, alternative energy events, etc.

I have also heard that it's a good idea to to have tow hooks because anyone new to electrics is bound to eventually mess something up, not have any power to the car, and need to tow it home.

I don't know if I would use my 4-cylinder S10 (manual transmission) to tow the car or not. That is the vehicle that I originally towed the Metro home with (using a trailer dolly).

It felt like the truck was good enough to tow the Metro, but just barely.

I would more likely borrow somebody else's truck on the rare occasion that I would need to tow the Metro. My dad has a Chevy AstroVan with the towing package. It's a pretty nice truck for general towing.

I do still have to take the Metro to inspection to prove that it no longer has an engine. (Apparently the pile of photos and records I sent in wasn't enough!) The emmissions test station is farther away from my house (opposite sides of the county!) than I can drive on a charge.

Looks like that will be my first tow.