# Planning 2nd generation Prius hybrid to full EV conversion.



## brian_ (Feb 7, 2017)

NoNameSolarCompany said:


> 4. DO not expect to retain the car's transmission as it is highly integrated with the hybrid driver and gas engine, so direct motor drive to the drive shaft is likely how I will proceed.


Do you really expect to connect a motor *directly* to the axle shafts? For one thing, unless you use two motors (one per wheel) you will need a differential so that the car can go around corners. Next, if you don't have some reduction gearing, the motor will turn at wheel speed, which is much too slow... you would need an enormous motor or motors to produce enough power at a such a low speed.

Every practical electric car has a reduction drive of some sort.


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## brian_ (Feb 7, 2017)

NoNameSolarCompany said:


> 7. Battery preference: #18650 Lithium Ion batteries in individual plastic holders tightly packed to make a super battery. This way bad individual cells can be easily changed out. I expect it will be series/parallel to meet the requirements of the motor and any motor controller gear.


An 18650 cell is a single cell, not a battery; a battery is a group of cells connected together. The car needs one battery, composed of many cells. There's no reason to call the car's battery a "super battery" just because it has a lot of cells... they all do.



NoNameSolarCompany said:


> This way bad individual cells can be easily changed out.


It's not so easy. Each cell is normally connected by a small wire which is welded to the cell; the wire is so fine that it serves as a fuse. It's hard to tell which cell is doing what once they are connected together, and hard to pull out and replace individual cells. If you don't have a robot building up the battery out of those little cells, it's easier to use larger cells.



NoNameSolarCompany said:


> I expect it will be series/parallel to meet the requirements of the motor and any motor controller gear.


Well, yes... motors of a useful size don't run on the less than four volts of a single cell, so you need a lot of them in series. At any reasonable voltage a useful amount of power is far more current than a single 18650 cell can produce, so you need a lot of them in parallel. In any battery made of such small cells, you will have at least a thousand cells.


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## brian_ (Feb 7, 2017)

NoNameSolarCompany said:


> I have removed the hybrid battery which I deem inadequate and old and am selling it on eBay to help pay for the new EV conversion parts


Everybody else will consider it old, too, and inadequate for anything but direct replacement of a failed Prius battery... and Prius batteries are quite reliable. New Prius batteries are readily available, so there's not much reason to someone to put in your old one. Be realistic about the small amount that you might get for this battery.


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## NoNameSolarCompany (Feb 11, 2018)

The Prius hybrid battery is not *that* old as it only has 5 years on it with a 10 year warrantee. It's not the original battery that came with the car, the original battery was damaged when I was rear ended on the freeway one morning by 3 pickup trucks behind me all hitting each other in a train line starting with me in the front. It cracked connections inside the battery and the damage went unnoticed by the collision people and Toyota for 2 years while I started seeing problems with acceleration dropping out on the freeway at random times and so it took so long the insurance wouldn't' back replacement by the time Toyota figured out what was going on after countless repair visits for reasons that weren't the reason and didn't fix the problem so Toyota was kind enough at that point to replace the battery under warrantee to make up for all the bogus repair bills of non-causes. Thus the battery is nowhere near the age of the car. No I wouldn't try to be selling an out of warranty battery. You think me crazy or something? It's been sitting 6 months without a charge and is still holding 212 Volts, so I don't think its so old nobody will want it... It seems sound still for a Prius but its not energetic enough for a full EV. The space is better spent on Lithium ION batteries than NiMH.


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## NoNameSolarCompany (Feb 11, 2018)

brian_ said:


> An 18650 cell is a single cell, not a battery; a battery is a group of cells connected together. The car needs one battery, composed of many cells. There's no reason to call the car's battery a "super battery" just because it has a lot of cells... they all do.
> 
> 
> It's not so easy. Each cell is normally connected by a small wire which is welded to the cell; the wire is so fine that it serves as a fuse. It's hard to tell which cell is doing what once they are connected together, and hard to pull out and replace individual cells. If you don't have a robot building up the battery out of those little cells, it's easier to use larger cells.
> ...


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## brian_ (Feb 7, 2017)

NoNameSolarCompany said:


> The #18650 cells were not going to be soldered or welded to anything they were going to be inserted into spring-loaded carriers just like sticking AAs into a common toy. Easy changeability. The carriers wiring would be soldered together in series parallel to achieve the correct voltage/amperage combinations needed.


I'm not sure if you appreciate the currents involved here. Spring terminals are great for a flashlight or toy, but at the high peak currents of EV use, I don't think that's practical.

You could connect a set of cells in parallel to a bus bar with a soldered wire for each cell (so that each soldered connection carries the current of only one cell), but I doubt that you would want a soldered connection to carry the full current of the entire set. These connections are normally bolted together.


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## brian_ (Feb 7, 2017)

NoNameSolarCompany said:


> If you wouldn't recommend using #18650s, what commonly available cheaper per kilowatt larger capacity lithium ions would you suggest and what kind of charging system?


The current trend, for a few good reasons, is to use modules salvaged from used production EVs. It usually doesn't make sense to break the modules down to the individual cells, but it is common to open the pack to take out the modules, and then re-arrange the modules both to package them in the vehicle, and to create the desired combination of series and parallel connections.

The most popular sources of used batteries are the most common EVs (the Tesla Model S/X and the Nissan Leaf) and the only common and high-capacity plug-in hybrid (the Chevrolet Volt).

You could buy individual 18650 cells, but it would probably be more expensive than buying used Tesla modules, and the modules come already assembled. Also, individually purchased cells are unlikely to be well-matched, and may not even be suitable for EV use; "18650" is just a physical format, and there is lots of variation of internal construction and cell chemistry between them.


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