# Planning 1969 Chevy El Camino conversion



## Vhclbldr (Feb 8, 2014)

My first post (yes, I am a newbie on this forum, please be patient)
I am comfortable fabricating entire vehicles (my creation is at http://www.indycycle.net), am competent with MIG and TIG (mild and stainless steel, chromoly and Aluminum), and have helped students construct four Electrathon Competition vehicles at three different schools as well as a recumbent electric tadpole bicycle.

This will be my first ICE-EV conversion, so I want to do it correctly, but possibly in stages (running prototype, then possible upgrade in motor/batteries, etc).
I would like to have a 50-70 mile range per charge, but more importantly would like to get massive torque (300-500 ft-lbs) with little weight difference (or even lower weight).

Running prototype costs will be minimum ($2K range), so most likely a forklift motor or similar will be the first motor choice along with Lead Acid Batteries. I know this won't get me the performance I want, but it will get it on the road.

However, I am leaning more towards just biting the bullet and getting the right components for the performance/range I want, so spending $4K for the motor/controller and $10K for LiFePo battery pack would not be unreasonable. I have looked into EV West's packages (Warp11 motor with Reid transmission) but am not familiar enough with other alternatives to commit yet.


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## Duncan (Dec 8, 2008)

Hi
IMHO - you are right to skip the lead,

Motors - DC is cheap and powerful, AC is expensive or wimpy or both

DC motors 
So far nobody has been able to convince me that an expensive EV motor is anything other than a forklift motor with advanced brushes (easy to DIY) and a nice coat of paint

DC controllers
I used a Soliton for a while - it is much more expensive than an OpenRevolt
BUT it is amazingly well made and powerful 
If I could afford one (get it past the wife) I would love to have one
Pricey but really nice

In your shoes I would be looking at 
Lithium
Forklift motor
Soliton


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## Vhclbldr (Feb 8, 2014)

Lithium, or LiFePo specifically?


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## Duncan (Dec 8, 2008)

Vhclbldr said:


> Lithium, or LiFePo specifically?


LiFeP04
Is whats normally used on EV's
You can get decent sized batteries and its quite robust and reluctant to burst into flames

LithiumPoly is used in RC cars - its light and powerful but has short life and a tendency to explode


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## Vhclbldr (Feb 8, 2014)

Is there a specific brand or supplier you would recommend, or should I dig through the battery forum?


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## Vhclbldr (Feb 8, 2014)

After several days (weeks) of reading various threads and posts, e-mails and online conversations, I believe my plan will go like this:

Phase 1 - Donor Car: Acquire 1969-1972 El Camino & move to Garage Mahal. Budget: $5000

Phase 2 - Prep: Modify drivetrain/body/bed for conversion (Remove ICE components, swap bench seats for ABS Racing Seats from JEGS, repair body damage, replace front clip with fiberglass fenders, hood, & header panel). Budget: $1000

Phase 3 - Motors: Acquire Impulse 9 (with Turbo 400-splined end) and Warp 9 Motors, connect with adapter plate. Approx cost: $4500

Phase 4 - Power: Acquire ~262V worth of 60AH LiFePo cells (88 cels at 3.4v each yeilds 299v) & design packs (to be placed througout vehicle to balance weight). Also acquire JuiceBox charger for battery packs. Approx cost: $8-10K

Phase 5 - Controller: Acquire Controller - either Zilla Z2K or Soliton 1 (the latter being $1k less, may not be the best choice in the long run). Approx cost: $4K

Lets see, that would be about $25K for the total project budget. Allowing for 20% cost overrun, I will plan on spending around $30K on this vehicle.

Anybody see anything wrong with my math, or can recommend changes for the long haul?


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## RIPPERTON (Jan 26, 2010)

Duncan said:


> You can get decent sized batteries and its quite robust and reluctant to burst into flames
> 
> LithiumPoly is used in RC cars - its light and powerful but has short life and a tendency to explode


Ive seen more LiFePo4 fires than LiPo.


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## dougingraham (Jul 26, 2011)

Vhclbldr said:


> Phase 1 - Donor Car: Acquire 1969-1972 El Camino & move to Garage Mahal. Budget: $5000


I've never owned an El Camino but I have always liked them. With this old of a vehicle there will be issues. Fix everything that is going to stay with the car as a conversion. Rust, brakes, suspension, that kind of stuff. Do your upgrades before you pull the ICE gear out. If you can do it yourself that is great but easier to drive it to a shop if you choose to farm out some of the repairs.



Vhclbldr said:


> Phase 3 - Motors: Acquire Impulse 9 (with Turbo 400-splined end) and Warp 9 Motors, connect with adapter plate. Approx cost: $4500


This was the one that caught my eye when I read the post. So your plan is to siamese an Impulse 9 with a Warp 9? You really only want to do this with identical motors or they don't share the load well. The plan is to wire the motors in series?



Vhclbldr said:


> Phase 4 - Power: Acquire ~262V worth of 60AH LiFePo cells (88 cels at 3.4v each yeilds 299v) & design packs (to be placed througout vehicle to balance weight). Also acquire JuiceBox charger for battery packs. Approx cost: $8-10K


I like your high voltage approach. It is what I would do today if I was going to do it over. 88 of the 60AH cells yields a 16.9 kwh pack. If the vehicle ends up weighing 3500 lbs then this gives an estimated drop dead range of 48 miles and a reasonable range of 34 miles. I would consider taking a hit to the weight and going to 100AH cells to increase the range but also to make them happier at peak loads. Hitting 1000 amps is a lot for these 60AH cells. If you use a zilla 2k that implies that the peak battery loads might be even greater.



Vhclbldr said:


> Phase 5 - Controller: Acquire Controller - either Zilla Z2K or Soliton 1 (the latter being $1k less, may not be the best choice in the long run). Approx cost: $4K


If you are planning on drag racing and pushing the motor to over 1000 amps then go with the Zilla.

It really depends on your goals but unless you are planning on drag racing it you probably don't need two motors. You mentioned you wanted a lot of torque. A single Warp 9 will do around 300 ft-lbs at something like 1100 amps for a short period of time. If I was doing my car over I would use a WarP 11 HV and a high voltage pack. You might consider a regular WarP 11 and a little lower voltage battery pack consisting of 120 AH cells (use pairs of 60AH cells.) At least 60 cells in series. That would give you a pack of 23 kwh with an estimated drop dead range of 65 miles. These are really rough range estimates and without knowing more it is probably only within 20% margin of error.

I wish you the best on this build!


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## Vhclbldr (Feb 8, 2014)

Thank you for the feedback, Doug! I may have my motors mixed up (Transwarp vs. Impulse), but the intent is to have the motors direct to the rear driveshaft, and the Transwarp comes fitted with just that. 

If I could get 300 ft-lbs out of a single Warp11 with less than 200 volts, I could see going the single motor and soliton controller route. Perhaps a single warp 11 with a EVGlide tranny would give me the best combination of oomph and range?

I agree that going with 100AH cells would be better (200 would be GREAT!), because my furthest commute is 39 miles each way once a month, with an eight hour stop before returning. For that, I would just use my normal ICE Ford Explorer.

I forgot to add my plan of putting a PV array onto the rear tonneau cover and being able to switch between charging the 12v accessory pack and main pack. Also toying with an on board range-extending generator (like a small honda unit) in the bed of the truck, but that defeats the battery conversion somewhat.

I am about eight months from beginning Phase 1, and will definitely get the donor car up to snuff in phase 2 (possibly upgrading to a Hotchkiss front end and rear swaybar) before beginning electrification, so I have time to make up my mind. The one thing I like about the dual 9's is that if I choose to try to take on some loud, rumbly mustang or corvette at a local stoplight (or Xmas tree), I could have a better chance of showing them my rear lights.

Silent but deadly...


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## Vhclbldr (Feb 8, 2014)

After reading a bit more, I am leaning towards the following build to maximize cost and performance, as well as scalability:

Warp 9 motor + EVGlide trans + Soliton 1 + (88) 100AH CALB cells.
This will put initial costs at roughly $2k + $3.5k + $3k + $10k = $19k

The weight will be almost identical to the original curb weight with ICE, and allow for brief 300 ft-lbs of torque (not allowing for transmission changes) plus highway speeds and decent range.


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## EcoReality (Mar 10, 2014)

Okay, I'm going to be a bit contrary and suggest picking up some flooded-cell NiCd batteries. Although they are heavier than liths, their internal resistance is lower, and they just will not sag, for a real neck-jerking experience off the block.

There are SAFT 180 AH batteries floating around out there, surplused from some bus company going under. You could easily get 5C, or 1,000 amps out of them!

Come to think of it, the extra weight will be useful on top of the drive wheels to keep them from smoking too much.


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## Vhclbldr (Feb 8, 2014)

More reading and more changes to the plan...

My current (revised) plan is to use a single Warp 11 mated to an EVGlide tranny, controlled via Soliton 1, and powered by 88 100AH Cells. I am still not sure about whether I will go with LiFePo or CALB yet, but I have time to decide upon that.

My reasons for the single 11" + EVGlide are:
- simpler build for first project
- plenty of torque @ 1000a if I need it (~300 ft-lbs)
- Tranny will give more low end grunt and top end speed, plus reverse and speedo
- if more power is desired in the future, there is room under the hood for tandem 11" with adapter plate (similar to EV west's BMW).

Any comments/issues/advice that I am not considering?


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## Casper10 (Mar 8, 2014)

Vhclbldr said:


> More reading and more changes to the plan...
> 
> My current (revised) plan is to use a single Warp 11 mated to an EVGlide tranny, controlled via Soliton 1, and powered by 88 100AH Cells. I am still not sure about whether I will go with LiFePo or CALB yet, but I have time to decide upon that.
> 
> ...


Hi Vhclbldr,I'll be watching on thru the build as I plan to convert my Ford Falcon utility to EV. From my recollection the elcamino is about the same size as my ute so I could gain a lot of experience from your build(at no cost HeHe).I am going to install a sound proofed generator into mine as well as pv,I have been playing around with the generator in my motor home installing a hydrogen generator on it and so far it's working out great, a lot less fuel use and cleaner emissions(smells better) and it seems to dip a lot less when ac starts etc, more power or holding load better,no concrete tests just seat of your pants feeling. Best of luck Casper10


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## Casper10 (Mar 8, 2014)

Vhclbldr said:


> More reading and more changes to the plan...
> 
> My current (revised) plan is to use a single Warp 11 mated to an EVGlide tranny, controlled via Soliton 1, and powered by 88 100AH Cells. I am still not sure about whether I will go with LiFePo or CALB yet, but I have time to decide upon that.
> 
> ...


Hi Vhclbldr,I'll be watching on thru the build as I plan to convert my Ford Falcon utility to EV. From my recollection the elcamino is about the same size as my ute so I could gain a lot of experience from your build(at no cost HeHe).I am going to install a sound proofed generator into mine as well as pv,I have been playing around with the generator in my motor home installing a hydrogen generator on it and so far it's working out great, a lot less fuel use and cleaner emissions(smells better) and it seems to dip a lot less when ac starts etc, more power or holding load better,no concrete tests just seat of your pants feeling. Best of luck Casper10


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## Vhclbldr (Feb 8, 2014)

Casper, I plan to add PV panels on the tonneau for charging while parked and had also considered adding a range-extending generator as well. Hydrogen may be the more environmentally friendly option, but I may go with a small, quiet gas one. Plenty of time to explore those options, especially since it will be a removable one.


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## Vhclbldr (Feb 8, 2014)

*Donor Vehicle*

DougIngram and John Metric, I could use your input on this one:

The Donor Elky has been found and purchased, now awaiting shipping from California.
The car is in near perfect condition for the build, already without engine/trans and engine bay/frame cleaned/painted. Several steps easier for me.

Definitely going the Zilla Z2K controller route, and likely 68 100AH CALB or Thundersky cells - 60 for a 198v main pack, then two separate 12v packs to run the accessories - switchable between use and solar charging during the day using panels on a custom tonneau.

I have read good things about the Elcon chargers, perhaps a 1500 for overnight charging.

I am torn between two Transwarp 9s (like John Metric, and possibly purchased through Lone Star EV) or just a single Transwarp 11.

Dual 9's with the coupler would cost more, but potentially produce more rear-wheel horsepower with the Zilla+hairball.

A single 11 might give me the performance I am looking for and end up weighing less overall and be less complex, as well.

Advice/thoughts/recommendations?


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## Hollie Maea (Dec 9, 2009)

*Re: Donor Vehicle*

If I were you, even if you decide to go with one motor now, get the high voltage Zilla so you can put a second motor in series when you inevitably decide you want it.

The motor choice between 9 inch and 11 inch is not as big deal as you might think. They will mostly just change the torque curve in such a way that can be mostly be compensated by gearing changes. But putting a second motor in series, assuming you have the controller capabilities, truely doubles your power.


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## Vhclbldr (Feb 8, 2014)

*Re: Donor Vehicle*



Hollie Maea said:


> If I were you, even if you decide to go with one motor now, get the high voltage Zilla so you can put a second motor in series when you inevitably decide you want it.
> 
> The motor choice between 9 inch and 11 inch is not as big deal as you might think. They will mostly just change the torque curve in such a way that can be mostly be compensated by gearing changes. But putting a second motor in series, assuming you have the controller capabilities, truely doubles your power.


I was thinking that same thing, instead of using a single Soliton1 and having to purchase a second one.

Also, I am leaning more toward the dual nines as it would give me more RPM range when coupled to the EV glide.

Too bad Lone Star doesn't sell a 2-speed with reverse, then I could get the package deal and known reliability.


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## sholland (Jan 16, 2012)

Not sure if you mentioned already or not, but you're going to need a charger too... The Juice box is just an EVSE or charge station.


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## Vhclbldr (Feb 8, 2014)

sholland said:


> Not sure if you mentioned already or not, but you're going to need a charger too... The Juice box is just an EVSE or charge station.


Agreed, which is why I like the Elcon. Given the many places in the rear panels of the El Camino, I should be able to mount it out of the way, but still accessible as needed.


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## dougingraham (Jul 26, 2011)

Vhclbldr said:


> Agreed, which is why I like the Elcon. Given the many places in the rear panels of the El Camino, I should be able to mount it out of the way, but still accessible as needed.


I operated for almost two years with the charger in the garage. If you never charge at public facilities why haul around the weight of the charger?


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## dougingraham (Jul 26, 2011)

*Re: Donor Vehicle*



Vhclbldr said:


> Definitely going the Zilla Z2K controller route, and likely 68 100AH CALB or Thundersky cells - 60 for a 198v main pack, then two separate 12v packs to run the accessories - switchable between use and solar charging during the day using panels on a custom tonneau.
> 
> I have read good things about the Elcon chargers, perhaps a 1500 for overnight charging.
> 
> ...


I just went back and re-read the whole thread. You want huge torque and you can get that 300+ ft-lb with a single Warp9 if you have enough current. A Zilla 2K will do that. If you are going to seriously drag race then you will want to Siamese your motors and do something like John Metric (and others) have done. My single WarP9 at 1000 amps did 266 ft-lb on a dyno. I found a reference to WarP 9 at 1400 amps of 339 ft-lbs. John Metric seems to be putting 200 volts at 2000 amps into his motors which means his peak HP into a motor is 536 (1072 for both).

If you are not going to seriously drag race you might consider a single Warp 11 HV motor. At 288 volts and 1400 amps you can briefly reach 540 HP into the motor. At 1400 amps that reference I saw indicates 415 ft-lbs. At 288 volts and 1000 amps it would be 386 HP and torque of 291 ft-lbs.

There is a big difference between an ICE car with 300 ft-lbs and an EV with that much because the torque comes on from zero RPM. With a WarP9 and a controller battery combo that can deliver 1000 amps at 170 volts you will see that torque from 0 rpm up to around 4500 rpm. In an ICE you will see that peak at perhaps 4000 rpm and it drops off in both directions. You might have less than 3000 rpm where the torque is good and the 300 ft-lbs is a peak found only in a very narrow range in the middle of that torque band.

Torque is what gives you that grin.


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## Vhclbldr (Feb 8, 2014)

*Re: Donor Vehicle*



dougingraham said:


> I just went back and re-read the whole thread. You want huge torque and you can get that 300+ ft-lb with a single Warp9 if you have enough current. A Zilla 2K will do that. If you are going to seriously drag race then you will want to Siamese your motors and do something like John Metric (and others) have done. My single WarP9 at 1000 amps did 266 ft-lb on a dyno. I found a reference to WarP 9 at 1400 amps of 339 ft-lbs. John Metric seems to be putting 200 volts at 2000 amps into his motors which means his peak HP into a motor is 536 (1072 for both)....
> 
> Torque is what gives you that grin.


Thanks for the wisdom, Doug.
With the plan for using a Z2K, I can just get a single transwarp 9 and alway add a second one if the urge to drag it comes over me. I like the wider range of rpm and lower weight of the 9, and would guess that it has a lower draw under medium load as well.


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## dougingraham (Jul 26, 2011)

*Re: Donor Vehicle*



Vhclbldr said:


> Thanks for the wisdom, Doug.
> With the plan for using a Z2K, I can just get a single transwarp 9 and alway add a second one if the urge to drag it comes over me. I like the wider range of rpm and lower weight of the 9, and would guess that it has a lower draw under medium load as well.


I don't think you will be disappointed. With the single motor it should feel quicker than it did with the original ICE. You can add a second zilla when you add the second motor or you could go to a Z2K HV from the start and run a high voltage pack. If you add the second motor you can just put them in series and turn the motor voltage setting in the zilla up to 300 volts.

The comment about the lower draw under medium load isn't really true. For most of these motors the efficiency is better in the middle load areas. It only gets poor at very low power levels but at very low power levels you are using so little power it almost doesn't matter. I suppose if you were driving in a parade at creep speed.


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## Vhclbldr (Feb 8, 2014)

Does wanting 526 out of a single Nine mean building a +200v main pack? And how many AH would be reasonable? I am estimating 100AH cells (or 2x60AH cells in parallel would work)


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## dougingraham (Jul 26, 2011)

Vhclbldr said:


> Does wanting 526 out of a single Nine mean building a +200v main pack? And how many AH would be reasonable? I am estimating 100AH cells (or 2x60AH cells in parallel would work)


Its probably not what you want to hear but to get to 192 volts reliably you probably need to mess with the brush holders and certainly replace the brushes with the correct DRAG racing brushes. These will not last long for street use. To get to the 200+ volts that John Metric is doing will most certainly require replacing the brush holders with the Helwig setup ($2100 per motor).

Setup for street use with occasional stints on the drag strip I would set the motor limits to 172 volts and maybe as much as 1400 amps giving 241 kw (323 HP peak into the motor). And you probably don't want to do this for more than 10 to 15 seconds tops. When stuff goes bad it happens really fast at these power levels.

You need to build a pack that can produce the input power the motor/controller is configured to take. At the bare minimum you need to have the sagged voltage exceed the maximum motor voltage you have selected. So yes if you want 200 motor volts you will need a pack that has a nominal voltage perhaps 25% higher than that. For a 200 volt motor setting you would want a 267 volt pack or about 83 LiFe cells in series. The other side of the coin is the amps. If you want to do 2000 amps at 200 volts (sagged) you need to take the 2000 amps and divide by the burst C rating of the batteries. Lets say your batteries can do 8C. You would need 2000/8=250 ah of batteries. If you do a 267 volt pack at 250 ah and the car weighs 3000 lbs you could expect a range of 222.5 miles. And it would be heavy enough that you wouldn't have a particularly fast car. This is why drag cars have special batteries.

It is not so grim if you drop the voltage to 172 and the current to 1000 amps. You would have 172 kw (231 hp) input to the motor. You would need a pack that unsagged was about 229 volts (72 LiFe cells in series) and 1000 amps / 8C = 125 AH. This would be 28.6 kwh and would give a 3000 lb car an expected range of about 95 miles. The pack would weigh something over 670 lbs.

You can take advantage of further increasing the voltage to lessen the AH requirement. If you were to take a 28.6 kwh pack made from 100 AH cells you would need 89 cells in series. The higher voltage will lower the battery amps requirement so that the 100 AH cells would be adequate. 172 motor volts * 1000 motor amps / (284.8 battery volts * 0.75) = 805 battery amps. This is pretty close to the 8C rating. Cells like the CALB CA series seem to only sag about 10% at 10C so if you were to use those you could get by with a smaller battery.

I believe you would be plenty happy with 172 kw on an El Camino. In low gear you will have no trouble making smoke come out of the tires.


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## Vhclbldr (Feb 8, 2014)

I will look into an 89-cell 100AH CALB pack and see if that will fit into the various places I plan to place them (gas tank, behind cab under bed, front end).

I am still wondering if the dual 9's:
A) will fit into the available space (I think so)
B) would be able to perform well with an 89-cell 100AH pack (or would I need to increase the AH or Volts in order to be able to send more power due to twice the motors)

My estimate is the I would have to double the pack capacity (volts or AH) in order to put in around 1000A at 172V into each motor through the Zilla Z2K HV.

I really value your explaining the pack and performance figures to me.

Luckily, I have some time while I wait for my Elky to be delivered from Cali...


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## dougingraham (Jul 26, 2011)

Vhclbldr said:


> I will look into an 89-cell 100AH CALB pack and see if that will fit into the various places I plan to place them (gas tank, behind cab under bed, front end).


Others have said and I agree. Fitting the batteries is about 60% of the work. But you need to decide on what you are going to fit. Making the decision on what will work and what is in the budget.




Vhclbldr said:


> I am still wondering if the dual 9's:
> A) will fit into the available space (I think so)


I know there is no room for this in my car. And when you get everything out of the hood area it looks cavernous but it fills up so quickly.



Vhclbldr said:


> B) would be able to perform well with an 89-cell 100AH pack (or would I need to increase the AH or Volts in order to be able to send more power due to twice the motors)


An 89 cell 100 AH pack of CALB CA cells can do about 256 kw (344 HP) for around 10 seconds. This is still single motor power levels. If you add a second motor all you do is share the load between the motors. You would still only get 245 kw.



Vhclbldr said:


> My estimate is the I would have to double the pack capacity (volts or AH) in order to put in around 1000A at 172V into each motor through the Zilla Z2K HV.


This is 344 kw. And with the caveat on the Manzanita Micro page you can't do quite enough voltage to place the motors in series. So you need to place them in parallel and do the 2000 amps way. At the low end using CALB CA's as the example you want 200 AH at a sagged voltage of 172 volts. You could use paired 100AH cells and 60 in series making a pack size of 38.4 kwh. You can also do this with 180 AH cells but you need a little more voltage. 200*172/180 = 191 volts sagged. Adding 10% for the sag gives 212.3 volts or 67 cells once you round it up. This would be a 38.6kwh pack.

With two motors (312 lbs I believe) and about 900 lbs of batteries it will probably feel a bit porky when you try to take corners. You will probably remove somewhere between 600 and 800 lbs of stuff and add back in 1300 lbs if you do the two motors with a range pack. Adding 600 lbs won't kill it but you might feel the extra weight.

What you could do is single motor with enough batteries to max out the motor but plan to add the second motor and double the pack at a future date. If you plan for it it won't be too bad if you decide you want more later on. Single motor and 60 of the 100 AH cells will be a little over 600 lbs. Add at least another hundred lbs for stuff and the vehicle will be similar in weight to original. Expected drop dead range of 64 miles and a battery saving range of 50 miles.

Everything depends on exactly what you want to do with the car. If all you want is to daily drive it then you don't need to be nearly so ambitious to get a good reliable ride.


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## Vhclbldr (Feb 8, 2014)

Since my goal is a snappy daily driver for a 12-mile round trip commute, but one that makes people think twice about deriding EV's, I will plan on a single Transwarp 9 with EV glide tranny, 89 100AH CALB for the main pack, and a single Optima for the accessory/controls. The Zilla Z2K should allow peppy performance. 

I still have to decide upon a BMS (or if not, bottom balancing on a regular basis, but this seems to detract from the convenience and low maintenance aspect of an EV).
I have heard good comments on several, but still have some time before having to commit.

Getting the car here and painting it (so it doesn't rust in the east coast atmosphere) is my first step. Hope to have that in the next 2-3 weeks.


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## dougingraham (Jul 26, 2011)

Vhclbldr said:


> Since my goal is a snappy daily driver for a 12-mile round trip commute, but one that makes people think twice about deriding EV's, I will plan on a single Transwarp 9 with EV glide tranny, 89 100AH CALB for the main pack, and a single Optima for the accessory/controls. The Zilla Z2K should allow peppy performance.


With 89 100 AH CALB CA cells (not SE) your 10 second battery output peak will be 285 kw or about 382 HP into the motor. Once the brushes are seated you will be able to get over 300 ft-lb from the motor from 0 to over 4000 rpm. I think you will be able to call this snappy. 



Vhclbldr said:


> I still have to decide upon a BMS (or if not, bottom balancing on a regular basis, but this seems to detract from the convenience and low maintenance aspect of an EV).


You probably will have to bottom balance your pack only once. I did mine and then two years later I did it again just to see if there was any real drift and there was not. The cells don't drift if they are in good working order. They will drift if some outside unbalancing load is placed on them (like a BMS.) With a bottom balance arrangement the only outside connection to the cells should be the strap between the cells and the cables at the most positive and most negative. Any other connections can cause imbalance.

EV's are not maint free. The oil doesn't need changing and the clutch almost never wears out but tires still need to be replaced and suspension components still have wear. If you have a car with no regen you will still need to do brakes maybe even more often because there is no motor back pressure. And you still have to wash it.

One thing I look forward to with the mass adoption of EV's is parking lots that have no unsightly oil spots.


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## Vhclbldr (Feb 8, 2014)

Working from my iPad makes it difficult to select individual statements to quote, but I wanted to quote your, "I think you will find this snappy" and add a bunch of smiles in response.
Really looking forward to it.

Do you use a BMS? By your post, it sounds like they are not that necessary as long as I do an initial bottom balancing first.

As far as other regular maintenance, you did not mention brush replacement along with tires, suspension, brakes and washing, but I imagine brush replacement is pretty infrequent under regular driving conditions.


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## dougingraham (Jul 26, 2011)

Vhclbldr said:


> Do you use a BMS? By your post, it sounds like they are not that necessary as long as I do an initial bottom balancing first.


I don't. As near as I can tell none of the OEM's do anything but monitor the cell voltages and the pack or module temperatures but not at a specific cell level. This is probably because they know the cells don't get out of balance on their own but you do need to keep an eye on things for people who know nothing. I consider my BMS to be me.

You can bottom balance or top balance. You should only have to do this once or when you decide to add more cells. With a bottom balance you can drive the car until it stops going and not hurt the cells much. If you let other people drive your car this will happen. Heck you might even do it. It is human nature to be just a couple of blocks from home and think you can make it when your instruments are telling you not to. With a top balance you will wreck cells if you do that. A top balance will get you a little extra energy out of the pack because the average pack voltage will be slightly higher. Not sure it is enough to worry about.



Vhclbldr said:


> As far as other regular maintenance, you did not mention brush replacement along with tires, suspension, brakes and washing, but I imagine brush replacement is pretty infrequent under regular driving conditions.


I looked at my brushes last weekend and I don't see any real sign of wear at 5700 miles. My motor is buried and it takes about an hour to get to where I can look at them. Probably take another half hour to change them in the car. I don't know how long they will really last but I will be driving this car about 6000 miles per year and if they last 50000 miles that is over 8 years. I suspect I will either have a serious upgrade to the power train before then or I will have moved everything to a different roller.

When the car shows up post some pictures!


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## sholland (Jan 16, 2012)

All OEM BEV and PHEV vehicles monitor all cell voltages, and they have some sort of balancing. Almost all use passive balancing of ~50 - 100mA, which is really only enough to manage very small levels of mismatch, and often only achieving balance over several charge/discharge cycles. The OEMs also have a strong desire to control cost and complexity (risk) so choose passive balancing. 

Most large packs, or packs comprised of large capacity cells (~100Ah+) in say buses, commercial vehicles, grid storage, UPS, etc use active balancing, with its ability to allow charging and discharging of cells and much higher transfer currents (100mA+). Poorer quality cells and applications with extremely high load or charge currents that exacerbate even small mismatch will benefit from active balancing. With the balance current levels required a passive balancing BMS would require dissipation of large amounts of energy (heat) and so becomes a problem. Also 100mA on a 500Ah cell would almost nothing. 

All of these systems also have very demanding accuracy, as the BMS will feed the SoC (state of charge) and SoH (state of health) algorithms at the pack level. Other requirements are detecting pack current, connection failures, temperature, self test etc.


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## Vhclbldr (Feb 8, 2014)

Okay, I have finally got a reason to start a blog on the EV build.
My El Camino has arrived. See more here:
http://electriccamino.blogspot.com

Looks like its time to start a new thread, since I have moved past the "planning" phase and into the "execution" phase.


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## sholland (Jan 16, 2012)

Lookin good... congratulations!


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