Converting To Lithium Batteries expectations and real life

We have closed the original “New GEM Owner - Converting To Lithium Batteries” (http://www.electricforum.com/cars/gem-cars-nevs-forum/3005-new-gem-owner-converting-lithium-batteries.html) thread as it was over 9 pages long.

However, please use this new thread to post you thoughts, expectations, experiences and views on converting to lithium batteries.

Out of curiosity, I stopped by a local scale to weigh my 2002 e825 two seater GEM. So, after removing the lead acid batteries and installing 22 CALB 100ah batteries, charger, etc., the vehicle now weighs 950lb.

Since the curb weight for the two seater is 1100 pounds with stock batteries, I was anticipating closer to 900 pounds but 950 pounds sounds good. I believe the 1100lb for the spec’d weight does not include the rear trunk and doors, which mine has.

RWD

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[quote=RWD;28968]…after removing the lead acid batteries and installing 22 CALB 100ah batteries…[/quote]I was wondering why you decided on such a low voltage LiFiPO4 pack? The controller can handle the voltage of up to 25 cells, and generally the higher the voltage the better for controller efficiency.

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?

RWD

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.

PS: For some reason, I stopped receiving subscription notifications to my original http://www.electricforum.com/cars/gem-cars-nevs-forum/3005-new-gem-owner-converting-lithium-batteries.html thread, so I didn’t notice new replies.

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.

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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.

Raise your cars rear up about one or two inches above the front and it will help stop the tires from braking loose… California rake.

Sit down, Shut up, Belt up…and HANG ON!

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.

Thanks,
Jeffrey 8189160787 LA, CA

Go with the Volt or Leaf. Lowest cost option out there.

If you go with volt, I can give you some tips.
The 48v packs are 44v nom. 24v packs are 22v nominal.

I used 2 X 12s 44v packs. Double if you want more range.

With Leaf you have more flexibility. Use 20-24s pack. And easy fit in center.

The advantage of the Volt. They are pre-assembled with monitor plug for accessories. More available and lower cost from junkyard.

One side shown. I have one on each side.
Wireless volt/amp meter pcb shown on B- terminal.

50ah only gives me <15M on a charge. I actually run 10-12 stop and go hilly miles then charge with plenty left.

[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]

My Trojans are dying so looking to go lithium…the question is WHAT ARE THE DIMENSIONS OF THE LEAF VOLT CELLS? Evidently the Calb or Calib new cells fit under the seat.

Can’t go wrong with Leaf. See Gwest thread with pictures.

I’m testing 24s monitors as I type. One is Bluetooth.

Think bat6 X 4 on steroids!:smiley:

The closed thread has a ton of useful information. How do we access it?

Rodney

Hi @Old_Houseboater

The old thread is here:-

http://community.electricforum.com/t/new-gem-owner-converting-to-lithium-batteries/1800

Regards,

Mark

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@Old_Houseboater @Cleanenergy you can bookmark this post for future reference. I have also added a “lithium” tag to it for easy searching in the future

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?