The lead-acid batteries in our 2009 48-volt EZGO RXV electric golf cart were 5 years old and in need of replacement. Living in The Villages, Florida, golf carts are not only used on the course, they are an important means of transportation within this very large community.
Because of the need for extended range, we intended to replace the aging set of four (T-1275) 12-volt deep-cycle lead-acid batteries with six 8-volt lead-acid batteries, but started researching Lithium ion cells as an alternative.
Here is a picture of the 320 pound battery pack that that will soon be replaced. When new these batteries have a maximum charge capacity of 150 amp-hours, but only 75 amp-hours of usable capacity. After 5 years, the capacity has dropped to the point that the cart is almost un-usable.
The 4th battery is partially hidden on the left side. The battery in the middle was a temporary replacement, hence no watering caps like its companions.
Why this blog?
Because the cost of lithium battery systems is several times higher than traditional lead-acid batteries, there are not a lot of people using them in golf carts; Consequently there is not a wide network of experience in the design and installation of a lithium pack system for golf carts or many experiences from actual users. I am sharing this developing story and details of what I learn about battery conversion for those who are thinking of doing the same. Hopefully it will alleviate some of the concerns regarding lithium cells as a alternative, provide some useful information and potentially avert some costly mistakes.
While I will share my design choices and operating practices, these alternatives may not be the preferred options for everyone. I will attempt to provide details and my reasoning for each, but I respect the choices that others make. There are many opinions on this topic and each has merits.
Why Lithium?
We finally chose to go with the lithium option due to several factors:
- Long cell life (up to 2,000 charges versus about 500 for lead-acid)
- Deep discharge (recommended 80% of capacity versus 50% for deep cycle lead-acid))
- No watering required
- Significantly reduced weight and size of the battery pack
- A very flat voltage discharge curve keeps cart performance steady over the discharge cycle
- Flexibility to custom design a system for the distance we wanted versus the price we were willing to pay.
- An engineer by training, I was fascinated by the topic and the battery conversion process has turned into a hobby
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It looks like you have had this in use for over a year now. Would appreciate your thoughts: e.g.
ReplyDelete1, Is it still in use?
2, Have there been any failures?
3, Are you happy with it?
4, Have you needed a "battery controller"
5, How many miles do you get in The Villages on an 80% battery level?
6, Have you seen other conversions in The Villages?
7, Any thoughts on commercial packages for conversion?
8, If you did it again, would you have gotten "100 AH" cells?
...
I am interested because I also am in The Villages and would like an electric cart but with good range and minimal maintenance.
Thanks much!
Excellent questions.
ReplyDelete1. Yes, we rely on the cart every day. My wife runs the wheels off of it! We have put 1,400 miles since the battery conversion.
2. Not yet. No battery failures or failures of any other equipment (knock on wood).
3. We love it! I would convert it again if starting over.
4. Not sure what you mean by a battery controller. All electric carts have a controller built in. If you are referring to a BMS or monitor, no not yet. Just using the amp-hour meter.
5. We have never used more than 50 amp-hours, so I can only tell you that we get 1.75 amp-hours / mile. For 80 amp-hours, that translates to 45 miles. We charge 2 to 3 times per week when the meter says we have used 15 to 20 amp-hours.
6. Yes, one of the members of the Woodworking club converted a cart about 3 years ago using 180 amp-hour CALB cells and installed a BMS. He knows a couple of others who have conversions also.
7. I am waiting for a commercial battery monitoring system, not a BMS which actively moves current between cells. Did not find one last year and have not checked lately. Basically, I only want a system that shuts down the charge when any one of the batteries reaches a pre-set limit, and on the bottom end, shuts down the cart when any one battery reaches a lower limit. BMS systems tend to try and balance the cells; This just throws them out of balance and adds complexity. Our simple system servers us well, but I would not trust others not to run the cart to empty.
8. Yes, the 100 AH cells are plenty for The Villages. 45 mile range would translate into about 3 hours of driving at an average 15 MPH. Highly unlikely anyone would be doing that routinely. The 180 and 200 AH cells not only add cost, but also weight (which impacts range).
My wife and I will only drive an electric cart. Just can't talk with a passenger over the combustion engine noise, bad smell, gas/oil leaks in the garage, and the engine turning off every time I stop, etc...... I would recommend a lithium system.
Hope you find something that fits your needs.