Not sure I have a great answer but I had a couple concerns. 22 cells brings my battery pack to 80 volts, which is 10% higher than nominal, which is as high as I felt comfortable, at least starting out. I was unsure of how high other components could handle going above nominal (e.g., dc to dc converter). I know of one person that pushed his voltage to the upper spec and it prematurely failed. (Not sure the voltage was the cause).
I saw 22 cells really as a starting point. I can always add more cells but I’m very pleased with my performance and range. And it worked out real well that all 22 cells would fit under the seat real nicely.
I see you run 25 cells. How’s that working out for you? What is the voltage out of your pack?
Fitting everything under the seat would certainly be a valid reason to go with a lower voltage pack.
The main problem I see with such a short pack string is the motor controller will low-voltage cutout at 70 volts. With only 22 cells, that’s only down to 3.18 volts per cell. With the voltage sag under load, the motor controller will cut out a bit earlier than this and cut usable pack capacity even further.
The motor controller has a high voltage cutout at 86 volts, which is how I selected 25 cells. 86 / 25 cells is 3.44 volts per cell; just above the full resting voltage of a LiFePO4 cell. I stop charging when the pack is about 85.5-86 volts. Even if I charged to 87.5 volts immediately tried to turn it on and drive, I would only have to run the lights a few seconds to bleed off that top bit of over-voltage and get going.
I’m planning on recreating and updated thread with all the original info I had posted updated with any new info and advice I have. I’d also like to make is a bit more step-by-step, to make it easier to duplicate my efforts for those interested.
My Trojans are dying and I would like to convert to Lithium. ANY HELP/INFO/TIPS WOULD BE GREATLY APPRECIATED. I was hoping to get junkyard/ebay lithiums from a Volt or Leaf or similar. But, the big issue I gather is what would fit under the seat. Also, I was thinking I would just leave the two dying Trojans upfront for ballast.
[quote=bgeery;29124]Ah, I meant to address regarding steering and traction:
The steering is lighter with the lighter curb weight when using lithium. The tires will also break traction easier when accelerating. This is some combination of two things-
The lighter curb weight placing less downward pressure on the front drive tires.
The increased power at the motor due to increased pack voltage and lower voltage sag under load.
You can enjoy your new speed demon, adjust driving style slightly, or reprogram the controller for slightly less aggressive settings.[/quote]
[B]I would suggest maybe leaving two of the regular batteries under the seat… if that doesn’t do enough than leave the two over the rear axel also. If that doesn’t work, eat a lot of Pizza for the next 6 months…! :D[/B]
I know this is sorta irrelevant but I am a student trying to analyze consumer opinions on electric vehicles!! pleas take take the 2 minute survey. Input is wanted!! https://www.surveymonkey.com/r/M5ZY3B8
I converted to lithium and don’t find the traction a big problem, love the improvement in steering effort so don’t want to add weight but find the ride much harsher now. Does anyone know if there are air shocks or just softer spring shocks that will fit?
Hello. I am newer to the gem car and want to convert to lithium, and get the max out of my car. I have an 03 e825. Is there a way you can send me a list of the things I would need. Once I understand what I’m doing I should be good. All the videos I watch are not very descriptive.
If I was to get 2 48v battery packs they will work, out of a leaf.
Or for for volt batteries I would need 22 separate cells.
I was looking to see if Prius batteries would work. They seem to be around 7.5 volts per cell and if I got 10-12 I would be good?
First - Do your research. There are many decades of projects, countless hours, and (I shudder to think about) cash spent going down much the same path as you are thinking about going down, available in the archives. All you need to do is click on the magnifying glass tool in the upper right of the page and choose a variety of keywords.
Use these previous posts wisely. This forum and some of these players go back to when there were still vacuum tubes in controllers (not really). Much of this tech has been explored and abandoned (for one reason or another) already. The archives are a fantastic learning tool that doesn’t cost you a thing (yet). Use the old stuff so you can see where this all came from.
Then - Skip to the end of the book to see the stuff everybody is playing with today. Here is a good example of the richness that can be found in the forums.
The problem is that you are starting with a pre <2004 car as your base. Paging through the classifieds you can find a wide range of cars and many think they can be bought cheap, fixed up, end up sinking a ton of money into them and still find them not quite up what they wanted. They usually sell them to the next guy and look for a later model car and start over or wander away from the whole e-car thing completely.
If you are a brand new owner of your 2003 you may not know this yet. The early cars have quite a few issues. If you have owned your car for a while you may already know about some/all of these issues and may have already corrected them.
The brakes are horrible.
Suspension is like a dump truck
Steering is from same dump truck
Motor selection is limited
Gear ratio is set more/less for street (depending on your build this may/may not be bad)
Electrical system is marginal
Battery space is limited
Parts getting difficult to find
Charger may need to be upgraded for Lithium. (Is yours yellow/black)
This all being said, Most of the above can be dealt with, and many are quite happy with their early cars. It all depends on what your goals are.
Or use this car as a test bed for tinkering and keep your eye out for a deal on a 2006 car to build your hotrod. Most of the above issues have been dealt with.
Then, you need to decide what you want your car to be. Your description “get the max out of my car” is quite typical of how most of these projects start. Yes - quite a bit can be done. In the end you will still have a 20 year old car that you put a ton of cash into that you will never get back out. If you are fine with that, then proceed.
If you can do most of the work yourself that is a bonus. It gets real expensive if you need outside help to do the work. Some of these flipper guys charge quite a bit to polish your car for you and some guys out there actually make a living from it.
Here is something on your Leaf Pack. Make sure they will suit your needs.
I may have more to add later… We are just getting started.
I think converting to lithium batteries is the way to go. This will make batteries small, flexible, portable, reusable, increase shelf life, cheaper, safe, easy to charge and create more customer satisfaction as compared to lead acid batteries.