DIY Electric Car Forums banner

1 - 4 of 4 Posts

·
Registered
Joined
·
53 Posts
Discussion Starter #1
When I began my conversion (almost 2 years ago), I expected to use flooded lead acid batteries (golf cart). The gist of my question is should I be considering lithium instead.

I'm kind of surprised battery type isn't an FAQ or sticky topic. If this has been answered, please just point me in the right direction.

My conversion is a 1985 VW Cabriolet (electro automotive kit). As I understand it the pro of the golf cart batteries are: lower price and less likely to turn them into expensive paperweights. The cons are maintenance and weight. I understand that lithium batteries have gotten cheaper and am wondering if I should be reconsidering.

I am aware that I may need a new controller or to reprogram the controller that came with my kit.
 

·
Registered
Joined
·
2,318 Posts
Pros:
1) No battery acid and corrosion to deal with and no inhaling fumes if they are inside the vehicle, and no adding water.
2) Almost no Peukert effect, much lower internal power loss, so significantly more useful energy out.
3) Supposed to last 3000 or more (depending on manufacturer) cycles at 70% DoD (no one has run them long enough to verify).
4) Less sensitive to cold, so greater vehicle range at lower temperatures than with lead acid.
5) Much higher energy density so generally much greater range for a given weight pack. If you want range of about 50 miles or more at highway speeds, LiFePO4 cells are about the only solution, other than a small pickup with lots of T 125's or T 145's.


Cons:
1) Require either unfailing care and discipline to ensure they are not over charged or over discharged since either of which if severe will kill a cell, or a bms to ensure this. Bms is around $400.00 to $2000.00 depending on pack size and type of bms.
2) Cost is much higher than fla. Life is expected to be about 2 to 3 times as long though, so maybe similar or lower cost overall. Life of both fla and LiFePO4 cells will depend strongly on discharge currents as fraction of cell or battery capacity, C.
3) Running them at over about 50 to 60 degree C can result in breakdown of the electrolyte, coating of the electrodes, an increase in internal resistance and loss in capacity.

Lots of threads here on various aspects of using LiFePO4 cells.
 

·
Registered
Joined
·
1,378 Posts
Good summary. A little addition: An abused lithium can emit fumes that are flammable, so lithium should be boxed and vented just like any other battery. I don't know if the fumes are toxic or not. It is nice that in normal operation they don't spit and gas.
Pros:
1) No battery acid and corrosion to deal with and no inhaling fumes if they are inside the vehicle, and no adding water.
2) Almost no Peukert effect, much lower internal power loss, so significantly more useful energy out.
3) Supposed to last 3000 or more (depending on manufacturer) cycles at 70% DoD (no one has run them long enough to verify).
4) Less sensitive to cold, so greater vehicle range at lower temperatures than with lead acid.
5) Much higher energy density so generally much greater range for a given weight pack. If you want range of about 50 miles or more at highway speeds, LiFePO4 cells are about the only solution, other than a small pickup with lots of T 125's or T 145's.


Cons:
1) Require either unfailing care and discipline to ensure they are not over charged or over discharged since either of which if severe will kill a cell, or a bms to ensure this. Bms is around $400.00 to $2000.00 depending on pack size and type of bms.
2) Cost is much higher than fla. Life is expected to be about 2 to 3 times as long though, so maybe similar or lower cost overall. Life of both fla and LiFePO4 cells will depend strongly on discharge currents as fraction of cell or battery capacity, C.
3) Running them at over about 50 to 60 degree C can result in breakdown of the electrolyte, coating of the electrodes, an increase in internal resistance and loss in capacity.

Lots of threads here on various aspects of using LiFePO4 cells.
 

·
Registered
Joined
·
4,325 Posts
When I began my conversion (almost 2 years ago), I expected to use flooded lead acid batteries (golf cart). The gist of my question is should I be considering lithium instead.
dependent on whether you can pay the ante up front, and believe the marketed life cycles. If so, LiFePo4 is the winner.

If you go FLA for INITIAL cost savings (despite weight and performance penalties) consider adding a central watering system to take care of FLA as painlessly as possible. (I happen to have a watering system available post-upgrade!)

I am aware that I may need a new controller or to reprogram the controller that came with my kit.
not a new controller, but a new charge curve in the charger for sure.
 
1 - 4 of 4 Posts
Top