# New member intro and Question...



## madderscience (Jun 28, 2008)

Welcome.

your crx HF is pretty much an ideal conversion candidate, and your speed and range requirements are modest.


WRT the conversion kit being sold, That is a bridgestone Etek or similar clone motor. Those are really great motors, but are really best for smaller things like motorcycles and ground-up lightweight builds. One of those should be able to propel a very lightweight car at lower speeds if you keep it in 1st or 2nd gear and you don't have many hills to contend with. They are very efficient and powerful for their size but have a relatively low maximum safe RPM (around 4000 rpm I think) owing to their iron-less armature design. The listing does not say what the specs or mfg. of the controller and charger are, which I would consider a red flag. At the very least, figure out what they are and price everything out separately and compare with other models from other manufacturers.

72V will limit your useful top speeds to around 35 or 40, in a crx if you had enough time you might be able to get to 50 or 60 in 5th gear but that motor would probably start overheating if you sustained it very long.

As for batteries, you should avoid lead acid batteries, especially normal car starting batteries, at all costs. Yes lithium costs more up front and should have a BMS system, but it is vastly better, and in the case of a 72V conversion every pound kept off the car will really help. A 72V, 100ah lithium pack would weigh under 200lbs, while a 72V, 150ah golf cart battery pack (six, 150ah 12V batteries) would weigh more like 500lbs. Due to the properties of lead acid vs. lithium the lithium pack suggested would still have more usable energy than the lead pack, especially after a couple years. The golf cart pack in the usage scenario you expect would certainly work but you would be replacing it every 3-5 years. In the meantime, you would see a linear degradation in range over time. Normal car starting batteries would not survive more than a few cycles, they are not designed for deep discharges.

Whatever you do, due to the cold you will want to have your battery pack fully insulated and probably add a battery heater. (It can be set up to maintain 70 degrees or so when the car plugs in, to avoid loss in range due to cold) If plugged in regularly and well insulated the pack will stay warm for up to a day even if not plugged in, so daily commuting would be fine. There will also need to be forced air ventilation for an enclosed battery pack, especially for a lead acid pack which outgasses hydrogen and oxygen as it charges. The lithium would only need to have the forced ventilation to prevent overheating when it isn't sub zero outside.

In dry weather, a CRX with a 100ah 72V lithium pack will probably be good for 30 or 40 miles at 40mph if the chassis is set up well (good high PSI tires, alignment, etc). (guessing about 150wh/mile). Depending on how powerful your cabin heater is (but assuming it is made from a household ceramic space heater or 1 to 2kw), you will need 1 or 2 kwh per hour to run it, which would probably knock 5-10 miles off your range if operated continuously. It would also be drawing 15 to 30 amps off your batteries.

Driving in the snow without heat on it would be safe to assume 2/3 to 1/2 the range of dry, no-heater driving. With the cabin heater on, subtract another 10 to 20% given that is a 72v system.

In other words, worst case scenario driving in the cold and snow you might only get 10 or 15 miles of range with such a setup.

Good luck.


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## Tesseract (Sep 27, 2008)

n1div said:


> ....
> http://www.ebay.com/itm/EV-Electric...ric_Vehicle_Parts&hash=item3a9f67672f&vxp=mtr
> 
> Does anyone have any opinions/experience/thoughts with the kit?


Here is a search of all posts about that kit company, Wilderness EV.

(In case that link doesn't work, it is a search of all posts in the "EV conversions and builds" forum, plus all of its sub-forums, for the word "wilderness").

I don't have any personal experience with this company, but I have noticed over the years that the experience of others has been overwhelmingly negative, probably because the components are more suitable for a golf cart than an on-road vehicle, even one as light as an old VW Bug.


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## major (Apr 4, 2008)

n1div said:


> http://www.ebay.com/itm/EV-Electric...ric_Vehicle_Parts&hash=item3a9f67672f&vxp=mtr
> 
> Does anyone have any opinions/experience/thoughts with the kit?


That is a DCPM motor which is undersized for an EVcar. It would likely fail in short order. It might be a good motor for a go kart or small motorcycle, but not for a car.


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## n1div (Jan 6, 2015)

Thank you all for the feedback and input.

Based on the links you've provided, it does seem like the motor provided is a bit on the weak side for any suitable automotive duties.

As for batteries, I was thinking more like Optima yellow top since those can be fully discharged and weighs 44lbs a piece(x6 pieces ~ 264lbs).

What kind of models/brands do you guys suggest I look for in terms of a 72v forklift motor and how reliable would a used one be? Anything to look out for when looking for one? I just don't want to buy one and have to either rebuild or get a new one shortly after.

Thank you again for the general estimations for heater/insulation/winter tips.


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## lithiumlogic (Aug 24, 2011)

Such a small lithium pack won't be that expensive surely?

The other advantage of lithium, is that you could add to them later if you feel the need for more range/performance.


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## n1div (Jan 6, 2015)

lithiumlogic said:


> Such a small lithium pack won't be that expensive surely?
> 
> The other advantage of lithium, is that you could add to them later if you feel the need for more range/performance.


I don't really know as I haven't really shopped around.

For a 72v system for my given needs, what kind of prices are you seeing?


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## lithiumlogic (Aug 24, 2011)

I'm going to be lazy and just go here even though it's not the cheapest

http://store.evtv.me/products.php?cat=10

90 dollars each for the 60AH CALB cells.

20 of those = $1800

Your charger will cost that much, you'll need a dc-dc converter, adapter plate, motor controller, goodness knows what tools and sundries..

60 AH cells x 72 V = 4.32KW

Roughly, this is 20% of a Nissan Leaf pack. A Nissan Leaf does over 100 miles around town. OK , your motor might not be as efficient, and the smaller pack will be discharged at a higher relative rate, and cabin heat will take a bigger slice of the pie on a low power vehicle. Even so, that's way over your 5 mile goal. You could just go BMS free and not run the pack to the edge of capacity to save more money.

The cells can do 10C, which means your 4.32KW pack could do 43KW bursts - about 60 horsepower. That might not sound like much, but the original engine of such a vehicle probably had to be revved over 3000rpm before it was making 60HP. And even a small engine car can keep up with the flow of traffic in town without ever going over 3000rpm.

EDIT -

For comparison, these seem to be the Optima batteries the OP refers to :

http://www.optimabatteries.com/en-u...045-d34-78-yellowtop-starting-and-deep-cycle/

55AH 12V 44lb $255

$1524 Optima vs $1800 for CALB cells

Lithium weight 89lb
Optima Weight 264lb


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## n1div (Jan 6, 2015)

lithiumlogic said:


> For comparison, these seem to be the Optima batteries the OP refers to :
> 
> http://www.optimabatteries.com/en-u...045-d34-78-yellowtop-starting-and-deep-cycle/
> 
> ...


Thanks for the info.

I found a source to get the same batteries for less than $150 shipped per piece so that is more like $900. For half the price of the Lithium, I can live with 165lb weight penalty. 

Now to find more info on forklift motor/controllers...


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## PStechPaul (May 1, 2012)

You may also try these 112 A-h 12V batteries for $100 each from Walmart. I am planning on using a couple of them on my electric tractor, where the weight (60 lb each) is actually beneficial:
http://www.walmart.com/ip/EverStart-Maxx-Group-Size-29-Marine-Battery/20531539

or for $87:
http://www.walmart.com/ip/EverStart-Group-Size-29DC-Marine-Battery/20531543

A smaller one (41 lb) is just $77.
http://www.walmart.com/ip/EverStart-Group-Size-24DC-Marine-Battery/20531540

If you plan to go with lithium eventually but can't afford it now, at least these would get you started for $500 or so.


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## Duncan (Dec 8, 2008)

Hi
$900 v $1800 is only part of the comparison

55Ah Lead acid - is only 55Ah if you discharged at the 20hour rate - in other words at 55/20 = 2.75amps - no good for any vehicle
at a more sensible discharge rate (150amps) you will get less than 25Ah
(This does NOT apply to lithium)

So your $900 pack has less than half of the capacity of the $1800 pack

Then you come to battery life
You will be lucky to get 300 cycles out of the Lead Acid - About 1/10th of the life of the lithium pack

I certainly would NOT go lead!


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## PStechPaul (May 1, 2012)

Yes, lithium is the way to go. But if you must save money up front to get something running, might as well go with _cheap_ lead. Maybe even get some car batteries from a junkyard at about $20 each and you might get 50 cycles out of them if you don't drain them too far. And you can recycle the lead when they poop out.


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## madderscience (Jun 28, 2008)

Just make sure if you do go with lead that your charger and all other components will be compatible with lithium when (not if..) you upgrade, and make sure there is enough space in your battery boxes to accomodate the lithium pack you ultimately want to upgrade to.

Another possible approach would be to buy used nissan leaf cells. these are starting to show up in conversions and are pretty easy to work with. They come in 7v, 60AH modules I believe, so you would probably want 10 of these to make a minimum size 72v-ish pack. I would design the battery bay to allow doubling this in the future, or to allow an upgrade to either 120ah, or 144v.

BH


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## Yabert (Feb 7, 2010)

madderscience said:


> Another possible approach would be to buy used nissan leaf cells... I would design the battery bay to allow doubling this in the future... to allow an upgrade to 120ah


I strongly second this comment!
You will need to learn about lithium cells, right, but you will enjoy the power and the energy density of lithium cells.

Hey! Lightweight 72v lithium conversion can work very well and manage only 20 lithium cells is ''easy'': http://www.diyelectriccar.com/forums/showthread.php/72v-systems-small-car-68596.html


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