Results tagged “ev” from The GPSy EV Project

The weather was finally nice enough to commute to work this week on my Piaggio Boxer EV with Prius NiMH batteries.

Here's the data from my CycleAnalyst:

My commute is slightly uphill on the way to work and downhill on the way back, which accounts for the difference in energy efficiency going to and from work.

The bike feels much lighter than with the SLAs and faster too (even with the gear reduction) so I have to say it's an unqualified success. I just hope I can get good life out of these batteries.

After Run #4, I was in a rush and so I put the charger on and went to a talk and then came back. About 3 hours had passed and the charger had over charged the batteries. It actually wedged the battery holder apart. So I'm worried now that my batteries will be weakened -- even though most of the bulging has subsided.

I reinforced the battery holder this morning and we'll see how it holds up.

I'm working on a bicycle assist motor project. I thought about using a hub motor or chain drive but given the economy, I'm going with a friction drive. Friction drive is cheap, has few little moving parts to go wrong, and is cheap. I think I can make it using parts almost entirely found around the shop -- with the exception of the friction roller.

Now what I like about friction drive is if you use a roller with a one-way bearing and take advantage of some physics, the motor can release from the wheel entirely when freewheeling, so the bicycle remains entirely pedal-able on its own.

I decided to go with rollers from the defunct EV Warrior project. They're available on the surplus market, have one way bearings, and are nicely knurled. Other people are making their own friction rollers from BMX wheel hub extensions, but they don't have one-way bearings.

Here are some dimensions almost entirely for my own benefit.

In my search for info on calculating EV efficiency, came across this interesting article with java calculators: http://www.ecoworld.com/transportation/the-battery-powered-car.html

The articles mention that standard EV car efficiency is around 4.4 kilometers (2.7 miles) per kilowatt-hour.

My little scooter gets around 40 watt-hours per kilometer on SLA (I need to get new figures for the 43.2 volt NiMH packs). Flipping that around, that's 25 km per kWh. That's around 16 miles per kWh.

I just won a bid for twelve Prius packs! They should hopefully be arriving later this week or early next.

Update: Batteries arrived and ready to be installed!

Each pack is a 7.2 volts 6.5 Ah prismatic NiMH battery with six cells. I'll be configuring them as 6S2P for 43.2 volts 13 Ah. I'm hoping that I can get at least 60% of the SOC from them (80% to 20% as on the Prius). That would be 43 volts, 7.8 Ah or 335 watt-hours.

This is perfect as I'm currently consuming 200 watts-hours each way with the heavy SLAs. The lighter NiMH packs should get my power consumption down even lower.

It looks like I'll be saving a good 20 kilograms or 50 pounds with only a slight loss in Watt-hours! I will have to bodge up a new battery carrier as the cells need to be kept under compression when being charged.

This is the post-flameout, rebuilt Piaggio Boxer EV. I changed the battery carrier from a top-mount system to saddle bags. This lowers the center of gravity and makes it easier to handle. I'm going to replace the seat with something more classic looking.

I welded the saddlebag carriers myself from steel tubing with my MIG welder.

The Electronic Speed Controller (ESC) is sitting on top. It's the replacement HV-110 that I received from Castle Creations with additional capacitors soldered in parallel on the input lines.

It's sitting in a Lexan enclosure that I bodged together. Unlike the old metal enclosure with a single temperature controlled fan, the new enclosure uses two fixed speed fans that pull the air across the ESC and the voltage converters (sitting below). They also are assisted by draft air when the vehicle is at speed.

This photo was taken a few minutes after a short run, the temp of the caps is 34 centigrade which is nominal. Anything less than 60 centigrade I think will be ok. The caps are rated at 85C.

Although the angle of the photo above makes it look like the ESC could short out on the voltage converters, it's actually held a centimeter or so above and everything is well insulated.

My little Piaggio-EV is back up and running. I made the following mods:

• My replacement HV-110 is now installed in an external plexiglass box with (much) better airflow and forced as well as passive air cooling. The forced cooling is on full all the time rather than the temperature variable fan that I used to have.
• Extra caps (470 uF x 6) soldered in parallel with input leads
• (Slightly) beefier wiring used -- 8 gauge rather than 12 ga
• 75 amp Andersen PowerPoles used instead of 30A
• Wiring shortened a bit
• Thermometer probe directly on caps to monitor heat

So far, it seemed ok. After my ride to work this morning, the caps heated up a bit -- from 17°C ambient at the beginning to 37°C ambient at the end of the 5 kilometer ride. I'm working on getting even more cooling in there.

6 amps used. 30 watts/kilometer average energy expenditure.

One of my best purchases last year was a little MIG welder from HarborFreight. It was around $100 with coupons. It doesn't come with any accessories, so I bought an auto-darkening welding helmet for around $40, leather welding gloves, slag chipper, etc. also at HF.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=98871

The MIG welder is flux core only with no gas option. This means you get a lot of splatter and slag, but you can always grind those off. I'm happy with the increasing quality of my welds on iron and steel. I used it to make the rear carrier on my scooter EV -- and most recently, a firewood rack for 1/2 cord of firewood. The little MIG welder runs on 120 VAC which is very handy since I can just use the current power outlet in my back yard.

Unfortunately a flux core MIG welder means that I can't weld aluminium (which needs gas), which is a bummer since the weight/strength ratio of AL is ideal for EV use. I need to upgrade to a gas MIG welder -- or a TIG welder. I'm leaning towards the latter but I really need to ge a 240/220 volt outlet installed since it's not worth trying to buy a 120 VAC TIG. But getting a TIG welder would be great. I could even weld titanium if I wanted to. :-) Maybe Santa will get me a Lincoln TIG welder for Christmas....

I use steel from a local steel reseller, Logan Steel. They sell surplus steel bar and sheet for $1 a pound, which is quite reasonable. Their billboards are ubiquitous in southern CT.

The other useful tools I'm using are an offset grinder to prep my welding stock. Also, I converted my HarborFreight compound sliding miter saw to be a metal cutting saw by putting in a 10" metal cutting disk. Very useful, especially when I'm cutting a lot of stock. What I like about my miter saw conversion is that I retained the ability to do 45° cuts (or any arbitrary degree) as well as relatively long cross-cuts, which a lot of dedicated metal chopsaws can't do.