Additional pack

[Aerowhatt]

Thank you for the tips on possible chargers. I wasn't aware of the high power ELCON or E-motorwerks DC chargers. They are both possibilities but either doesn't fit budget so there is that. More complication than needed, I should be able to do what I need for closer to $1,000.00

I think I might start with plan A which was mobile charging capability without pulling a trailer. I can do that for 145lbs on the hitch receiver (car handles fine with this load). Basically a genset modified with a catalytic converter and sound reduction down to 45 to 50 db. That's about as loud as a quiet dishwasher. Which would be acceptable in most any parking lot wouldn't you think? Of course an EVSE to go with it. Next step would be to charge while driving by building the required power supply to deliver low ripple 360 VDC from 240 VAC. Once that all is working and proven I can move toward the ~450 lb trailer which could charge at 14 to 15 KW if needed. Likely the two PMG 132 DC motor - generators that I already have driven by a subaru/robin 20 HP twin cylinder OVC engine.

The trailer design is something I'm not sure about until I do some electric "traveling" and see what I need along that I don't want inside the car. I'll have time to figure that angle out better and ultimately get something better suited to what I need. As long as it is kept narrow and light there are plenty of possibilities for ancillary usage. One thing I'm pretty sure of is using stock front rims and tires just like come on the "i" as the trailer wheels and tires. There are numerous advantages to doing so (up front cost not being one of them).

Aerowhatt

 

[jsantala]

This company is advertising a 8 kWh extra pack for our vehicles:

http://eauto.si/metron-shop/?product=electric-range-extender

Interestingly, it also uses a DC/DC converter, which boosts the extender battery from 60V to 360V. I'd like to get one of those converters..

 

[PV1]

I've seen that before, maybe the same company.

Unless my math is wrong, I can build a custom pack and make it fit in the back with very little cargo capacity difference and add 35-40 miles of range. If I remove the padded floor in the back and build a pack around the motor room lid, it can fit nearly flat at the same level as the stock cargo floor. The only issues to work out are the limited charge/discharge current and how to make 360 volts safe.

 

[wmcbrine]

This company is advertising a 8 kWh extra pack for our vehicles:

http://eauto.si/metron-shop/?product=electric-range-extender

Interestingly, it also uses a DC/DC converter, which boosts the extender battery from 60V to 360V. I'd like to get one of those converters..

€ 7,978.80 :shock:

 

[PV1]

If you don't mind me hijacking, I believe I can fit a 9 kWh battery pack in the same space as the padded cargo floor. For a roughly 1,000 cell battery pack, it will fit in the back and only be 1.5" higher than the stock floor. This extra 9 kWh would increase the range from 62 miles to 95 miles and weigh about 150 lbs. Being at main pack voltage, it would also be able to accept regen, quick charging (to a point, see below), and regular charging without a second plug.

The major caveat right now is the limited charge/discharge current. Aux pack amperage is limited to 30 amps, which is less than 1/3 of the possible amperage. Theoretically, with two packs of the same capacity and internal resistance would equally share load and charging currents. Keeping resistance the same, the load share would be 54 amps max for the aux pack and 96 amps max for the main pack. At the max, I could discharge the aux pack at 35 amps, which is still short of the theoretical max of 54 amps under full throttle. Of course, since I plan to source used laptop cells, the internal resistance may be high enough to nullify my amperage concerns.

 

[PV1]

I'm torn. For $2,400, I can get a bunch of used laptop cells and build a 12P88S auxiliary pack out of 1,056 cells. This is the easier of the two routes I'm thinking of, as there are already tabs welded to each group of 3 cells with a spot for wire interconnects between parallel groups. However, this may lead to less capacity than I hope for with more weight and space taken. Plus, there are current limits that I have to deal with.

http://liionwholesale.com has Panasonic cells that hold 3.4 Ah and can discharge 6.8 amps continuous. For a bulk purchase of 500 cells or more, the cost is $5.17 per cell. So, for a pack with similar (actually more) capacity, it would take 792 of these cells wired 9P88S and cost $4,100. With the current share between the packs, I calculated that the most that the car will pull from the aux. pack is 57 amps, which is below the max. continuous output of 61.2 amps. Of course, with differences in internal resistance, there may be more than 57 amps draw on the aux pack, but I plan to have a separate ammeter on the aux pack and limit throttle based on amperage. The downside to these cells is that I now have to weld/solder tabs to each cell and then connect each cell.

I want to use 18650 cells as they can be packaged in a way as to not affect cabin storage or handling (less than 100 lbs. in place of the foam floor in the back).

 

[Aerowhatt]

I want to use 18650 cells as they can be packaged in a way as to not affect cabin storage or handling (less than 100 lbs. in place of the foam floor in the back).

What do you plan to use for a BMS for them? I like the idea, but it seems like it will get more expensive once all the T's are crossed and I's dotted. As for amp loads I always put an auto reset circuit breaker in the Aux pack line. This trips if the Aux pack is near overtaxed and brings it back online a few seconds later. Pretty seamless and very simple without limiting acceleration when you might need it most.

Aerowhatt

 

[PV1]

I'm not sure on a BMS yet, but I have MiniBMS in mind right now.

I was thinking of having a buzzer attached to the relay driver of the ammeter when I'm near the max current, and if I'd need more acceleration, put the car in neutral, flip the switch to disconnect the aux pack, and drop it back in gear. Once the high demand is over, put the car back into neutral (do this to minimize arcing) and reconnect the pack. I can use the rocker switch i already have installed up front to control the aux relay.

That circuit breaker sounds like a better option than a fuse. Maybe have all three options, manual cut off, the breaker as fallback, and the fuse for definite overload.

 

[Don]

Would you actually use the extra 30 miles often enough to make it worth the $4K+ price tag?

Don

 

[PV1]

I would say yes, as it would allow much more use of heat in the winter, as well as enable freeway travel in places where I have to stick to the main roads (to Pittsburgh and back, for example). Plus, I would like to start venturing further out with the i-MiEV and start taking short road trips. There are a few places where it is just a little too far for comfort between charging locations (Blairsville, PA to Altoona, PA, or Cranberry to Slippery Rock, for instance).

Last winter, I helped to set up for my work's Christmas party. That was two round trips of 35 miles each, for a total of 70 miles in sub 20 F weather. I charged at every opportunity, and by the time the party was over, I was crawling home at 30 MPH with no heat at 5 F at midnight. I even had to stop and charge at my work on the way home, which worked out since I had to unload the AV equipment anyway. I was tempted to just sleep in the office overnight, I was so tired :lol: . Still, that's not something I wish to repeat.

Right now, the route to Normal, IL from my town could be done in the i-MiEV as is, but the aux pack would enable some AC/heat usage or travel along faster roads.

 

[jsantala]

I could really use about 7 kWh on my weekly 240km trip that I need to make. It would save me a stop (down from 3 to 2 stops). Especially since the middle stop is slow right now. Even 4 kWh would mean an hour saved. Doubling the charging speed would have the same effect (saving an hour). But getting 7 kWh would really be the ticket.

I've been also considering a 104s string of 20Ah LiFePO4 cells. I'm much more comfortable with LiFePO4 and have experience with them on my DIY motorcycle and car conversions. Also negates the need for a BMS, since I've found bottom balacing to be more than adequate. The cost for 104pcs of 20Ah cells would be a little over 3000€ and mean 6600 Wh more to drive around. Almost doubling the usable on-the-road range (you can only really get 10 kWh out of a CHAdeMO quickly).

The bad side on the LiFePO4 solution is the weight. The pack would weight around 70kg.

 

[Don]

I would say yes, as it would allow much more use of heat in the winter . . . .

Right now, the route to Normal, IL from my town could be done in the i-MiEV as is, but the aux pack would enable some AC/heat usage or travel along faster roads.

It sounds like you'd get a bigger bang for your buck with a diesel heater - $750 or so and no doubt you'd use that nearly every day for 5 or 6 months of the year. The extra range would be nice for those out of ton trips, but the heat would be welcomed every day in the winter . . . . and it's LOTS cheaper and simpler to do

Don

 

[Phximiev]

Given his success with the eSamba, his range extender project may be worth watching over the next month or so:

http://youtu.be/xFBUkU303Js

 

[Phximiev]

Well, it's going to be an interesting extender.

http://youtu.be/TA78B1XQq5U

 

[Phximiev]

Working extender?

http://youtu.be/85I4WSAkzkQ

 

[Phximiev]

This looks like an excellent result:

http://youtu.be/V2HbSiOwqGQ

It should be doable for an iMiev also.

 

[jray3]

Sorry for not taking the time to watch all of Jehu's vids- is he paralleling the packs, using one at a time, or transferring charge from the Aux pack to the main pack?
My EV conversions are set up for all of the above, with an Anderson SB350 connector on pack POS and NEG, before the main shunt and main fuse, but after the main disconnect. That way, when I connect an auxiliary pack, I can run it in parallel or only on the aux pack (by opening the main disconnect). Could even reverse the poles on the aux pack connector and run it in series with the main pack, which is a racing mod I'm considering for ultracapacitors (with a contactor to drop them out of series when depleted).
I can also do charging input through that connector, fand have used it with a genset trailer and also a Manzanita charger in DC-DC mode, like the Enginer setup.
With this approach, all current flow is measured by the main shunt and reported on an E-Meter (Xantrex Link 10), but since the BMS for the main pack doesn't use the main shunt, it doesn't get confused.

 

[Phximiev]

I don't know how he is setting up his packs. Good questions, perhaps calling/emailing him would be a possible approach?

I think he's here: http://www.electricsamba.com/category/esamba-episodes/

 

[jsantala]

I believe he has a 144V Curtis and since the packs are 60-ish Volts each he has them two in parallel and then in series.

These are the packs he's got:

http://www.evwest.com/catalog/product_info.php?cPath=4&products_id=329&osCsid=bkv5mk0og48b3vqtcsdlibrj16

They're from Smart EV, originally by Tesla. Many, many 18650 cells.

 

[pbui19]

When the Tesla Powerwall was first announced, i did a quick fit check and i think it'll fit in the iMiev with the seat down. Not a bad price of $3500 for 10kwh. But I am not sure if it comes with BMS. I really hope the Gigafactory works out.