- Your skill level with auto mechanics and fabrication
Engineer/fabrictor/mechanic at a BMW performance shop. On hand MIG and TIG, sharing a building with a machine shop. Design automotive performance parts and software for a living. Have a reasonable electronics lab in house for "small" stuff, with a few good soldering stations, a hot air rework station, etc.
- The range you are hoping to get (how many miles/charge)
Initial target of 30 miles. Minimum of 25 (distance from home to shop). Longer term target of 60 miles if the lithium technology continues to drop in price.
- What level of performance you are hoping to get
doesn't need to be fast or quick. Needs to not hold up traffic off the line, and needs to be capable of 70mph on the freeway. Doesn't need to outrun a 1980's Mercedes 240D.
- How much money you are willing to put into your project
"less is more." At least for the first attempt. I'd like to keep this more of a "toe in the water" sort of test. so would love to target a budget of $5k. (Given my access to material and fabrication, the only "cost" would be the main parts. Batteries, motor, controller, charger, wire. The car is "free", and adding something like a gearbox would be as well.)
- What parts you've already considered, if any.
Batteries: AGM. likely PC2150's. Also trying to find info on "tempest" batteries. Such as the TR120
Controller: based on cost, and my love of building stuff, I would like to try the ReVolt.
Motor: There is apparently a very large forklift dismantler about an hour south of me. Would like to find something in the 8-9 inch range.
Charger: no idea.
BMS: also a ?.
I figure I'll need to decide on a battery first...? Though perhaps the cost of those sorts of components should drive part of the battery decision?
On the charger front, I would like to target a 4-6 hour recharge time. Max of 8 hours.
The donor car came with an automatic transmission. I could swap pedal clusters with a manual and plumb the clutch, but I would prefer to not. Clutchless with a manual is also an option. I have spare manual transmissions and appropriate driveshafts so installing one would be easy. My ideal solution (if it will work) would be to put the electric motor in the transmission tunnel and couple directly to the driveshaft. This would give the entire engine bay for batteries and the controller, and save the weight of the gearbox.
The car starting life as an automatic is to my advantage on the gearing front. The car came with a 4.44:1 differential. This gives me hope because the manual transmission 318ti's came with a 3.45, and things like the 328 came with a 2.93.
A 328 is OK off the line in 2nd gear with little throttle. (2.49 in the gearbox and 2.93 out back, so 7.29 total.)
I will try to do more testing on that front in the next few days (get a car to 1000 rpm in the closest gear to my target ratio, ~3rd gear in the 328) and see if the acceleration rate is in the ballpark.
Only other concern on gearboxless is the power draw for a given acceleration rate. I don't have any higher ratio diffs that I can easily use at the moment. Will direct drive be harder on battery/motor/controller/other parts? Or just slower?
On the battery front, I would love to do Lithium, and realize it is likely more cost effective long term, but I have difficulty justifying the up front expense.
Engineer/fabrictor/mechanic at a BMW performance shop. On hand MIG and TIG, sharing a building with a machine shop. Design automotive performance parts and software for a living. Have a reasonable electronics lab in house for "small" stuff, with a few good soldering stations, a hot air rework station, etc.
- The range you are hoping to get (how many miles/charge)
Initial target of 30 miles. Minimum of 25 (distance from home to shop). Longer term target of 60 miles if the lithium technology continues to drop in price.
- What level of performance you are hoping to get
doesn't need to be fast or quick. Needs to not hold up traffic off the line, and needs to be capable of 70mph on the freeway. Doesn't need to outrun a 1980's Mercedes 240D.
- How much money you are willing to put into your project
"less is more." At least for the first attempt. I'd like to keep this more of a "toe in the water" sort of test. so would love to target a budget of $5k. (Given my access to material and fabrication, the only "cost" would be the main parts. Batteries, motor, controller, charger, wire. The car is "free", and adding something like a gearbox would be as well.)
- What parts you've already considered, if any.
Batteries: AGM. likely PC2150's. Also trying to find info on "tempest" batteries. Such as the TR120
Controller: based on cost, and my love of building stuff, I would like to try the ReVolt.
Motor: There is apparently a very large forklift dismantler about an hour south of me. Would like to find something in the 8-9 inch range.
Charger: no idea.
BMS: also a ?.
I figure I'll need to decide on a battery first...? Though perhaps the cost of those sorts of components should drive part of the battery decision?
On the charger front, I would like to target a 4-6 hour recharge time. Max of 8 hours.
The donor car came with an automatic transmission. I could swap pedal clusters with a manual and plumb the clutch, but I would prefer to not. Clutchless with a manual is also an option. I have spare manual transmissions and appropriate driveshafts so installing one would be easy. My ideal solution (if it will work) would be to put the electric motor in the transmission tunnel and couple directly to the driveshaft. This would give the entire engine bay for batteries and the controller, and save the weight of the gearbox.
The car starting life as an automatic is to my advantage on the gearing front. The car came with a 4.44:1 differential. This gives me hope because the manual transmission 318ti's came with a 3.45, and things like the 328 came with a 2.93.
A 328 is OK off the line in 2nd gear with little throttle. (2.49 in the gearbox and 2.93 out back, so 7.29 total.)
I will try to do more testing on that front in the next few days (get a car to 1000 rpm in the closest gear to my target ratio, ~3rd gear in the 328) and see if the acceleration rate is in the ballpark.
Only other concern on gearboxless is the power draw for a given acceleration rate. I don't have any higher ratio diffs that I can easily use at the moment. Will direct drive be harder on battery/motor/controller/other parts? Or just slower?
On the battery front, I would love to do Lithium, and realize it is likely more cost effective long term, but I have difficulty justifying the up front expense.