[OR-Carl]

Hello all, I have been thinking about an EV conversion for a long time, and finally decided to take the plunge. I am mostly doing it to learn some new skills, so I am trying not to get too bogged down on the performance stats that I simply *must* have. I love the idea of driving a car that I designed and assembled, and that I can fuel with the sunlight that otherwise would just make the weeds in my yard grow taller.



This is my first attempt, so I have lots of questions, but I am finding lots of great info on older threads, and will try and do as much reading as I can. I live off grid at the moment, so I have a decent bit of knowledge about electricity and batteries. I have a modest metal shop, and some basic fabricating skills with my MIG welder. I feel like I have a grasp of the theory, but am hoping to draw on the pool of experience on this site to ease me over into the world of practice; without too many costly and time consuming blunders! Some of the posts are getting to be 10 years old, too, so I will need some guidance on what information is out of date.



From what I have read so far I am sort of thinking along the lines of an AC motor with LiFePO batteries. Seems that doing series wound DC might save 1,000$ but the AC will give me a little more efficiency and make Regen easy to add. I have a lot of hills here, and drive a lot of short stretches on back roads, so it seems like regen might be nice to have.



I like what I have read about CALB 180s, I was thinking of a 144vdc system, so like 45 cells in my battery. My math says this should give me 50-70 miles at 80% dod at about 300-400wh/mile? If my assumptions about rolling resistance and coef. of drag are close, I am thinking that might be about what I would pull going 45mph on average, with a little wiggle room for starts and stops?


Part of me wants lead acid to work, but the numbers dont seem to add up. I would like my truck to be able to actually move something other than electrons every now and then.



I am curious about Li-ion packs like the ones out of scrapped Tesla's, which seem like they might be a little cheaper, and have higher energy density. Have they caught up to the iron chemistry in terms of cycle life?



Anyhow, I would love to hear some input on these broad strokes, AC vs DC, Regen, and LiFePO vs Li-ion. I would also love it if anyone could point me to other s-10 or pickup builds on here for me to look over. I know I will have some questions about power steering and brake options (I will probably skip air con for now).


I just picked up my donor vehicle today; a really clean '96 with a blown head gasket. I will post a picture when I get a chance.

 

[brian_]

What has changed in the last decade is largely the availability of modern components salvaged from EVs. That means AC motors, matching controllers, and lithium-ion batteries.

While lead-acid has obviously fallen out of favour, so have the LiFePO4 cells; salvaged EV battery modules are the now-affordable replacement. Production EVs typically run at around 360 volts (nominal), and both brushed DC and common aftermarket AC motors are typically suitable for much lower voltage, but there is an easy solution: use only some modules of a salvaged EV pack.

 

[brian_]

LiFePO vs Li-ion

LiFePO4 is lithium-ion (Li-ion); LiFePO4 is just one of several cathode compositions used in lithium-ion cells. I assume that you are intended to compare LiFePO4 (also called "LFP") to the alternatives which have become much more common in recent EVs, such as NMC and NCA.

 

[OR-Carl]

salvaged EV battery modules are the now-affordable replacement.

So I have been looking at the battery offerings from EV West, and I did some comparisons between the different chemistries (thanks for the correction there). The price per usable Kwh is about half for the salvaged modules compared to new LFP cells. How do they stack up in terms of real world use? The CALB cells claim like 2000 cycles, but is that at much smaller C-ratings than they likely would see in an EV? Have people on here who did early conversions with that style of battery had to switch them over, or are they still going strong?



It clearly seems like Tesla put a lot of engineering into their batteries, but are there challenges with integrating them into a DIY setup? With 444 cells per module, and a string of 6 modules that is 2664 cells for the BMS to keep tabs on. I have not been able to find much info on that topic, and would really like some input on what others have used in the past. Also, what about cooling the batteries?



I was also looking at the Netgain hyper 9 high voltage AC motor, and wanted to get peoples take on that for powering a little pickup.

 

[Duncan]

My tuppence worth

NEW cells will have a failure rate - about 3-5%

Salvaged OEM cells are much much LESS likely to have any failures at all

I'm using a Chevy Volt Battery - very impressed by the engineering and the quality

As far as motors are concerned

Forklift motors are cheap powerful and unsophisticated

New DC are expensive powerful and unsophisticated

NEW AC (like the Hyper9) are expensive and wimpy or VERY expensive

AC from a production EV - are streets ahead of anything else - but you need to handle the electronics

 

[brian_]

It clearly seems like Tesla put a lot of engineering into their batteries...

Tesla... and everyone else. Although Tesla sells the most EVs (after all, they have massive capitalization and no other product to sell), they're not the only EV manufacturer. They are also the oddball, being the only significant manufacturer to stick with little cylindrical cells, and that last to go to permanent magnet motors. Every manufacturer has a sophisticated BMS, every manufacturer other than Nissan uses active liquid thermal management systems, and they all work.

With 444 cells per module, and a string of 6 modules that is 2664 cells for the BMS to keep tabs on.

No, the BMS is not aware that there are thousands of cells (7104 among the 16 modules in this example). It monitors only the groups of parallel cells, so every EV with the common battery configuration of 96 cell groups in series monitors only 96 voltages and a few temperatures (one or two temperatures per module), regardless of whether a group has a couple of large cells or dozens of small cells (74 in the modules from a Tesla 85 kWh battery).

Also, what about cooling the batteries?

Circulating coolant is important at least to evenly distribute heat in among the cells (in modules designed for liquid cooling); whether the system is actually needed for cooling or heating depends on the operating conditions of the vehicle.

 

[OR-Carl]

It monitors only the groups of parallel cells, so every EV with the common battery configuration of 96 cell groups in series monitors only 96 voltages

Ok, that makes sense, I think. When not charging or discharging, would all the cells in each cell group effectively have the same voltage, because being linked in parallel they can transfer power between each other and thereby stabilize their voltage? Like if there was one weak cell, the other 95 would all chip in a few electrons, and bring it up to an even footing with the others?

 

[MattsAwesomeStuff]

When not charging or discharging, would all the cells in each cell group effectively have the same voltage

Any time cells are in parallel, they're going to be the same voltage. Charging, discharging, idling, doesn't matter. If they're in parallel, they'll be the same voltage.

This happens nearly instantaneously, only limited by how much current the batteries can discharge or recharge at, and the resistive limits of the conductors (nearly zero).

Under massive loads, it's possible that the voltage of some cells will momentarily sag slightly compared to others, but that's because they're all being flatlined and some don't droop as much. It's still corrected almost instantly when the load is removed.

It's a non-issue. Whether the modules are the same voltage as each other in series, is a much more difficult question because there's no self-balancing mechnism. Hence why you should have a BMS.

 

[brian_]

Like if there was one weak cell, the other 95 would all chip in a few electrons, and bring it up to an even footing with the others?

Not "the other 95" (of the 96 groups in series), but the other 73 of the 74 in a parallel group within the module.

 

[OR-Carl]

Not "the other 95" (of the 96 groups in series), but the other 73 of the 74 in a parallel group within the module.

Yes, sorry I misread the earlier post and was thinking that the standard was 96pXXs, but yeah, i was talking about the parallel cells within the cell group. (I was about to gripe that you cant read the old posts while formulating a response, then scrolled down and found them.



So basically, a 5.3kw 22.8v Tesla module out of a model S, which has 3400ma cells in (74p6s) is going to look to the BMS like it was 6 cells in series, with a capacity of 251.6AH (74*3.4), right?



So complexity wise, 6 of those modules in series would be electrically equivalent to 36x prismatic cells of 251AH capacity.


That helps make it seem less daunting. I am still a little worried about thermal run-away, but maybe after doing more reading it will seem like less of a problem. I will try and find some threads with info on thermal management.



I posted a response to Duncan's message, but it didnt show up. It flashed some message that I didnt quite catch - does anything that quotes an Admin need to get authorized, was that it? Anyway, hopefully it shows up, as I wanted to get some input on motors.


Thanks everyone for the great help so far!

 

[brian_]

Yes, sorry I misread the earlier post and was thinking that the standard was 96pXXs, but yeah, i was talking about the parallel cells within the cell group.

Good

So basically, a 5.3kw 22.8v Tesla module out of a model S, which has 3400ma cells in (74p6s) is going to look to the BMS like it was 6 cells in series, with a capacity of 251.6AH (74*3.4), right?

So complexity wise, 6 of those modules in series would be electrically equivalent to 36x prismatic cells of 251AH capacity.

Yes, and yes.

I posted a response to Duncan's message, but it didnt show up. It flashed some message that I didnt quite catch - does anything that quotes an Admin need to get authorized, was that it?

I've never heard of that - it seems more likely to be a temporary glitch, or an attempt to post twice to the forum without enough time between them.

 

[Cor]

I just picked up my donor vehicle today; a really clean '96 with a blown head gasket. I will post a picture when I get a chance.

If you are thinking about converting an S10 then take some leads from the existing (factory) conversions that are aplenty. There are several factory EVs, from the 97 Chevy S10EV to the 94 US Electricar and the many home conversions.
To get an overview and conversion details, take a look at the EV Album and filter for S10. I have my S10 with Nissan Leaf batteries on there, as well as my previous S10 with Lead-acid.
www.evalbum.com

 

[dtbaker]

Dear OP,

I am one of the few 'old school' DIY conversion people that apparently still believes that a simple DC design is the way to go for the average DIY enthusiast.

I am NOT a fan of attempting re-use of OEM battery packs and/or AC motors.... because you'll find out very quickly that the expense goes way up, and the electronics to communicate between batteries with sophisticated chargers and environmental control, the controller/inverters with proprietary software/hardware/firmware, and sophisticated variable speed transmissions are all pretty daunting.

If you want a highly efficient Ev with a 200 mile range, buy one for $30-40k

If you want to BUILD one for $12k-$18k, I'd stick to:
- Warp9 DC brushed motor
- Zilla 1k or Soliton controller
- 120v or 144v or 156v x 130ah or 180ah or 200ah cells (CALB or other high quality prismatic in simple series)
- simple charger like Elcon/TCCH with LiFePO4 curve set for 3.5 or 3.55vpc at end-of-charge, top balance, and manually inspect/balance every 6 month.

If you visit http://www.EnviroKarma.org you can read thru the step-by-step build of my eSwift, and the move from original lead-acid to LiFePO4 (huge improvement)

Or.... if you want to 'rehab' one that's already *mostly done*, watch this forum, and buy one that is mostly done, and rehab whatever is missing or broken.

 

[OR-Carl]

Hey dtbaker, I appreciate your input. I have been thinking about doing one of these conversions for a while, so in my mind an "old school" build like you describe sounds exactly like what I had been imagining. That being said, I do recognize that progress is being made, and I dont want to build something that is obsolete before its even done. I have a lot more research to do, obviously, but Its great to hear from people who have actually done it.


Thanks, Cor, I have looked at some of the S-10s on the ev album, and I think I have yours bookmarked, even. Lots of good info on there, I just need to compile it all and digest it, as its so hard for me to keep everything straight still.


I did want to get back to the post you made, Duncan, and get some more input on what you meant. Specifically, you said that new AC systems are expensive and wimpy, and that new DC are expensive and powerful. So, comparing a warp 11 to a Hyper 9:


The hyper 9 puts out 162 ft/lbs, and 120hp (this is probably its peak output?)

The Warp 11 only does 135 ft/lb, and is rated at 32 hp continuous.



The price for the Hyper 9 is 4300, but that includes the controller, while the warp 11 is 3000 + at least 1500 for a controller?


It seems to me that they are both equally expensive, but is the AC version really wimpy? Am I missing something important in looking at the specs?

 

[dtbaker]

... I dont want to build something that is obsolete before its even done. ...So, comparing a warp 11 to a Hyper 9:

The hyper 9 puts out 162 ft/lbs, and 120hp (this is probably its peak output?)
The Warp 11 only does 135 ft/lb, and is rated at 32 hp continuous.

My point is that a 9" brushed DC motor, 1kamp controller, and 120v-156v LiFePO4 battery pack is not obsolete.... plenty of power, range, and reasonably simple to build for the average DIYer.

A Warp9 with a zilla 1k controller and 156v battery pack is capable of putting out about 150kw of power for 10-30 seconds.... which is WAY more than you need for very decent acceleration! It translates to 'feeling' like a small-block v-8. The nice thing about the Warp9 versus an 11" or 13" motor is that the max revs are higher (maybe 5000 rpm), so your existing transmission is usable.

AC motors/controllers used in all the OEM evs are more efficient, operate at lower currents, and extend range with regen braking... true... but cost more, are more complex, and operate at much higher voltage which means more complex battery pack and battery management as well as lots of computer/control stuff that may be out of the area of expertise for the average DIYer.

You have to pretty much change your mindset when looking at electric motor specs versus gasoline. with ICE motors you are used to looking at PEAK horsepower and torque ratings, but with DC electric they typical post the CONTINUOUS power ratings because they are thermally limited as they are typically air-cooled.

The good news is that a vehicle on the highway going 60mph probably only needs about 20kw to overcome air and rolling resistance, meaning that a Warp9 is plenty. The peak of 150kw in the example above would likely only be for 10 second 'acceleration' events, limited by your controller output, and then in between your motor air-cools..... a Warp 9 is PLENTY for any average urban/suburban use, trust me on that.

 

[brian_]

... you said that new AC systems are expensive and wimpy, and that new DC are expensive and powerful. So, comparing a warp 11 to a Hyper 9...

Comparisons in this forum between "DC" and anything else are often intended to mean salvaged (e.g. from forklift trucks) motors, and so the assumed cost of the DC motor is minimal.

Comparisons to new aftermarket AC motors are usually intended to mean to the induction motors from HPEVS, not the relatively recently available permanent magnet AC motor which NetGain is selling as the HyPer9.

And in Duncan's comments "expensive and wimpy" AC motors are low-voltage aftermarket motors (such as those from HPEVS), not the even more expensive high-voltage PM AC motors such as the HVH series or those from YASA.

 

[OR-Carl]

My point is that a 9" brushed DC motor, 1kamp controller, and 120v-156v LiFePO4 battery pack is not obsolete.... plenty of power, range, and reasonably simple to build for the average DIYer.


AC motors/controllers used in all the OEM evs are more efficient, operate at lower currents, and extend range with regen braking... true... but cost more, are more complex, and operate at much higher voltage which means more complex battery pack and battery management as well as lots of computer/control stuff that may be out of the area of expertise for the average DIYer.

a Warp 9 is PLENTY for any average urban/suburban use, trust me on that.

Okay, that is all good info to know. I did not mean to disparage the performance of an "old-school" rig with an LFP battery and a salvaged DC motor. I suspect that it would more than meet all the criteria that I am aiming for. However, a Zilla 1k controller costs about 2300$, right? And a new warp 9 costs 2000 - So even if I got a free motor, I am *only* going to save 2 grand, compared to buying a pretty capable AC system, right? If I figure that I am going to sink 20k on this project, that only amounts to 10%, which just so happens to be the number thrown around for how much regen might add to my performance. How much do forklift motors cost, anyway, and how easy are they to obtain? (remember, I am really new to this ) I am still in the planning phase, so nothing is set in stone, but I just dont want to cut every corner I come to untill i know its actually a worthwhile shortcut.


Has anybody out there used a Hyper 9 that could weigh in on its merits?


As far as batteries go, Prismatics sounds appealing for their relative simplicity, long cycle life, high discharge rate, and inherent saftey. But they are about twice the cost per Kwh of the used modules.



So right now, I guess I am looking to strike the right balance between complexity, performance and price. So far the only thing I think I will say is off the table for my build is going to be changing the drivetrain, and using production EV voltages (which I assume also precludes production EV motors). A little bit of software engineering I CAN probably handle (I think this is a pun, but I still basically have no idea what a CAN bus is or how it works ). Lots of reading to do...

 

[dtbaker]

However, a Zilla 1k controller costs about 2300$, right? And a new warp 9 costs 2000

Your can find used ones for 1/2 if you re patient.... I would go with Warp9 over a used forklift motor, they have much nicer brushes/commutator and well worth the extra cost over a rusty hunk of crap you have to rebuild.

As far as batteries go, Prismatics sounds appealing for their relative simplicity, long cycle life, high discharge rate, and inherent saftey. But they are about twice the cost per Kwh of the used modules.

you CAN wait for used/decommissioned prismatics.... but be aware that if the entire pack is not from the same build or batch, then you are asking for problems keeping them balanced over time as they will 'drift' due to differences in internal resistance.

... using production EV voltages (which I assume also precludes production EV motors). A little bit of software engineering I CAN probably handle (I think this is a pun, but I still basically have no idea what a CAN bus is or how it works ). Lots of reading to do...

before you sign up for that, poke around and see how many of the builds that have been completed and drivable on this forum are 120v-160v DC builds versus how many completed drivable conversions are 300v AC builds based on OEM parts.

Just as a frame of reference, I am a mechanical Engineer with years of experience in car mechanics, welding, machining, 'regular' software, but none in the EE stuff needed to talk to the OEM controllers, BMS and charging systems. The DC brushed motor, clutched transmission, simple controller, and simple top-balanced charger (without CAN bus and BMS ) is still the way to go in my opinion....

 

[Duncan]

My tuppence worth

A forklift motor is exactly the same as a Warp - except for the paint job - and I have found our local elephants graveyard so they cost $150 - $200 each

P&S do a series of superb controllers for about $1000 each

Volt Battery Packs cost about $1800 for 16 kwh and are incredibly well engineered and come apart into nice sized modules for the DIY user

 

[OR-Carl]

Sorry dtbaker, reading back over my own post, I can see that I was not being very clear - there is still so much I am trying to sort out.


So, the picture in my mind is coming down to these options, in order of my current level of interest:


Motor option A: New Hyper 9 144volt(or equivalent 120-144volt AC motor kit) total cost ~$4500


Motor option B: New Warp 9(or equivalent DC motor) + Zilla1k controller(or equivalent) total cost ~$3000-4500


Motor option C: Salvaged DC forklift motor + P&S controller(or equivalent) total cost ~$1200



Battery option 1: 6s 22.8v 5.3kwh Tesla modules with ~25kwh @80%DoD Cost: $9500 $/wh: 0.37



Battery option 2: 2s5p 60.8v 2.6kwh LG CHEM battery modules with ~21kwh @80%DoD Cost: $7400 $/wh: 0.35



Battery option 3: 45s 3.2v 180ah prismatic LiFePO4 cells with ~21kwh @80%DoD Cost: $11700 $/wh: 0.56


Battery option 4: Locally sourced modules from scrapped EVs, Size, cost, and availability: Unknown



Most of these option are of things that are in stock and ready to ship from EV west or other online retailers. I figure this is going to be a big enough project without it also turning into a scavenger hunt (I am not ruling out other options, especially if I find things that can be dependably sourced when I want them).




I am also pretty sure I will want a BMS system regardless of battery type.
I will include some form of thermal management system if I use Tesla or other OEM modules that call for it.
I will plan on keeping the stock transmission and clutch.


I am not going to do anything with a voltage over about 144vdc.
I am not planning on using any motors or transmission parts from production EVs.


I really do appreciate all the input, so feel free to weigh in on any of this.


This is the donor vehicle, btw. It still needs a name...