Piaggio Boxer-EV conversion (almost) finished

nasukaren's picture

My replacement servo-tester finally came in yesterday (a saga in itself). I immediately tore it apart and replaced the potentiometer in it with a cable so that it could plug into my Magura throttle. The design of this replacement looks very simple. All discrete components: a 555 timer IC, rectifier, and some caps. I think I'll try to reverse engineer it so that I can just build it myself next time.

While I was waiting for the replacement to arrive (two weeks!), I took my Boxer almost entirely apart and placed the ESC and other electronics in the compartment where the old gas tank used to be. I also made a pannier for the batteries on the side. The result is a pretty clean ride:

The bike is very stock looking, which was one of my key goals. From the outside, the only indication that it perhaps isn't gasoline powered are the two SLA batteries in the panniers. The only real work that needs to be done is to clean up the remaining wiring for the servo-tester / throttle.

This is a neighborhood kid who helped me make the battery carrier. He insisted on being in the photo.

I'd like to revise the battery carrier to be a little more stealth. This first version was just a hack-up to get the things mounted.

Right now I only have batteries mounted on the right side. Two SLAs (2 x 12V = 24V @ 18 Ah) give me a top speed of 30 kph (20mph) which is just fine for the type of intracity commuting that I made this bike for. The bike has such good starting torque that it's low max speed isn't that noticeable.

I originally planned to mount a third battery or perhaps fourth on the left side. However, two batteries are giving me the speed that I want so I might put a regular pannier on the left so that I can carry groceries.

The following are some screen shots of the CycleAnalyst after my first test ride in this new configuration.

My range was 6.5 km on almost fully recharged batteries. This surprised me. I only pulled out just over 7.5 Ah before the batteries died. The batteries are rated at 18 Ah (20 hr) nominal and around 12Ah (1 hr). I was sucking juice out of them pretty fast, still I expected a little more capacity.

The Wh/km of this bike is excellent as it's very light and not all that fast.

The speed here is given in km/h. So that would be around 20 mph max and 15 mph average.

The batteries were seemingly dead at the end of the test run. As you can see, Vmin was 15 volts (this includes voltage sag/drop from power use) which was causing my CycleAnalyst to reboot sporadically and the ESC to cut in and out. Very bad.

Yet when I hooked the SLAs back up to my smart charger, it said that they were 42% full. Which is about right as I pulled 7.5 Ah out of an 18 Ah battery. Still, there was really no juice left in them. Maybe if I had let them rest a little bit, I could've gone a few more kilometers.

I'm trying to figure out what to do. The max speed is fine but the current range is a bit lower than what I had wanted. I wanted a range of around 12 km so that I could go to work and back without recharging. Some people mentioned that AGM SLAs take a while to "break in" so I guess I'll try to see if that's true and if performance gets better as time goes along.

p.s. Just a side note, Amax was 129 amps @ 24 volts = 3000 watts or 4 electric horsepower! This was just starting torque, when I was cruising it was sipping around 300 watts to keep me going.

Comments

Mik's picture

You Beeeauty! Very nice post, thanks!

How strange....is the curse of the EV even hitting the DIY-er?

As in: "If you reach the bottom end of the expected range then you are doing well???"

Either the Martians are sucking electron power out of Earths sub-fields, or the battery specs are just as reliable as the average Ev-specs!

Mr. Mik

This information may be used entirely at your own risk.

There is always a way if there is no other way!

nasukaren's picture

Mik -

Yeah, I'm really not sure what is happening. Maybe gremlims are stealing Amp-hours while I'm not looking. I'd like to eventually move this bike over to NiMH or LiFEPO, but I need to save up some money before that! :-)

Karen

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

andys's picture

What LA batteries are you running? I found there was a noticeable difference in range and voltage drop when I went from regular SLA batteries to high rate ones. Powersonic and B&B make them in that size.

nasukaren's picture

Rhino Rage batteries:

http://www.ragebattery.com/batterystore/SLA-17-12.html

Hmmm... they *were* rated at 18Ah when I bought them, now the website shows them at 17Ah. Maybe they'll decrease down to 8Ah (truth in advertising) by the end of September.

I should've just splurged and gotten higher quality ones like you recommend.

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

Jeffkay's picture

Karen, My son's bike: http://www.evalbum.com/1314 uses the same form factor of the 18AH but they are 22 amp hour. They are Universal brand. See his blurb for range, motor, etc.
Jeff K.

nasukaren's picture

Jeff -

Your son has a great ride! Part of the difference in range is that his bike is very very light, while my moped is perhaps 100 lbs dry (w/out motor or batteries). And the CVT drivetrain eats up a lot of power too. :-(

My next conversion will be a bicycle!

Karen

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

Jeffkay's picture

Well the point of telling you about the 22AH is available. Also, if you live in a large metro area, which it seems you do, we have found it better to find the batteries local and though maybe they are a tad higher than the web sites, they will not have any shipping costs.
Jeff

P.S. My buddy is building a vintage looking bike like a Whizzer. While at a local electronics store I saw a pallet, almost empty of 18AH sealed lead acids. They were in great shape and only 20 bux each. He bought 6 of them!

P.S.S. If you are doing a bike next, look at the Bosch 36v/3AH lithium-manganese packs. they need no BMS and are a good deal at about 70 bux ea.

P.S.3 How did you attach the kid to the seat like that? Very handy and the kid looks fairly light..! LOL
Jeff

nasukaren's picture

Jeff -

The secret to attaching a kid to the seat is that he has no legs! Actually, they're detachable and he sockets onto the panniers.

Karen

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

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