EZGO TXT 875E: Battery Help Needed

[Bruiser Smith]

It seems like on this forum there is always one new person posting about a Burning Man art cart - this year that's evidently me, so first off hello everyone!

I was fortunate enough to get a really sweet deal on a 2001 EZGO Textron 875E industrial golf cart. It's 48v and I'm working through getting the electrical running, but it sat for a while and most of the 6v batteries are junk at this point.

Here is my dilemma: I'm looking for the best batteries for my application. I need to power the motor, nothing more - but, very very limited usage except a few times a year. I did some research, and also went by a local golf cart service/sale shop to talk about replacement batteries (Trojan T105s), and they recommended not using those due to the limited amount of usage along with the fact that those batteries don't like to sit unused.

****Please at this point don't say 'get a gas powered vehicle' - I get the point, and in a perfect world that's what I would have gotten. This EV is what I have currently and I need to make this current vehicle work for the time being****

I'm looking for suggestions for some kind of 48v power bank that requires minimal upkeep and will be used super infrequently. I realize that it may not exist currently, or may be cost prohibitive, but would love to hear people's suggestions.

[JohnnieB]

No lead acid batteries like to sit unused because they self-discharge and unless they are recharged every month or so they will become boat anchors in a couple of months, but if they are kept on float charge, they will last indefinitely, so all you need is the right charger and a power outlet near where the cart is stored.

However, even on float charge the wet-cell deep-cycle batteries normally used in carts need to have the electrolyte level checked periodically. On the other hand, AGM deep-cycle batteries are more or less maintenance free.

Also, using Lithium batteries is a possibility, but probably cost prohibitive.


---------
When you do use cart, how long are the trips you take. The longer the trip, the more storage capacity is needed.

If the trips aren't too long, using six 8V batteries will give you 48V. For max range, eight 6V batteries would be needed.

[BobBoyce]

Originally Posted by Bruiser Smith

It seems like on this forum there is always one new person posting about a Burning Man art cart - this year that's evidently me, so first off hello everyone!

I was fortunate enough to get a really sweet deal on a 2001 EZGO Textron 875E industrial golf cart. It's 48v and I'm working through getting the electrical running, but it sat for a while and most of the 6v batteries are junk at this point.

Here is my dilemma: I'm looking for the best batteries for my application. I need to power the motor, nothing more - but, very very limited usage except a few times a year. I did some research, and also went by a local golf cart service/sale shop to talk about replacement batteries (Trojan T105s), and they recommended not using those due to the limited amount of usage along with the fact that those batteries don't like to sit unused.

****Please at this point don't say 'get a gas powered vehicle' - I get the point, and in a perfect world that's what I would have gotten. This EV is what I have currently and I need to make this current vehicle work for the time being****

I'm looking for suggestions for some kind of 48v power bank that requires minimal upkeep and will be used super infrequently. I realize that it may not exist currently, or may be cost prohibitive, but would love to hear people's suggestions.

Lithium is your best option. They can be parked for extended periods of time, and don't require frequent charging to stay charged. You'll not have to check electrolyte levels, and they weigh a lot less than lead/acid batteries. You can find used Nissan Leaf (electric car) modules for about $80 each on eBay. Try to buy a matched set of 7 modules from a single supplier. A BMS (battery management system) PC Board can be bought from eBay for about $40, and the BMS can control the charger shutoff to allow a 48V golf cart charger to be used with your lithium pack.

Here is a link to my first post where I began the conversion of my 2008 RXV from a lead/acid pack to a lithium pack...

http://www.buggiesgonewild.com/elect...ml#post1505943

[Bruiser Smith]

Here is a link to my first post where I began the conversion of my 2008 RXV from a lead/acid pack to a lithium pack...

http://www.buggiesgonewild.com/elect...ml#post1505943

This is pretty awesome thanks for sending that. I'll pore over the details tonight as that would be about the same price as buying 8 new lead acid batteries. Any major pointers beyond what's located in the thread? Time is, well, very much a concern too. Ack.

[BobBoyce]

Originally Posted by Bruiser Smith

This is pretty awesome thanks for sending that. I'll pore over the details tonight as that would be about the same price as buying 8 new lead acid batteries. Any major pointers beyond what's located in the thread? Time is, well, very much a concern too. Ack.

My biggest issue was waiting for the various parts and pieces to arrive. If I lived in an area with access to electrical or electronic supply shops, it would have gone faster. But I was at the mercy of eBay, a few sellers excessive shipping delays, and broken items arriving...

I'm a visual thinker. So when I design something, I visualize it in my mind, then translate that into an actual assembly. I don't always commit it to paper or a drawing before actually building it. In this case, I tried to convey as much detail as possible. The drawing (BMS) defines the cells to BMS connections, since that is the heart of ensuring that the lithium cells charge and discharge limits are properly cared for.

[Bruiser Smith]

Originally Posted by BobBoyce

My biggest issue was waiting for the various parts and pieces to arrive. If I lived in an area with access to electrical or electronic supply shops, it would have gone faster. But I was at the mercy of eBay, a few sellers excessive shipping delays, and broken items arriving...

I'm a visual thinker. So when I design something, I visualize it in my mind, then translate that into an actual assembly. I don't always commit it to paper or a drawing before actually building it. In this case, I tried to convey as much detail as possible. The drawing (BMS) defines the cells to BMS connections, since that is the heart of ensuring that the lithium cells charge and discharge limits are properly cared for.

Hey Bob, just wanted to say thanks for the detailed write up and your responses. I love your clean install and am planning on doing something similar as possible following your instructions. Looking into things further, I have a few questions:

1. Since mine is an industrial EZGO Series there are obvious differences between that and your 2008 RXV - what concerns are there in taking a Series system to Lithium? Controller/solenoid issues?

2. Charger - I have the 48v Lester that came with it and it seems to work fine but is a super heavy thing. That said, am I correct in thinking that the BMS pulls double duty here as both charging the cells as well as distributing charge across them? It appears from your design that the BMS has 120v coming into it?

3. Power - do I need to add anything to regulate the onboard voltage down from the 53.2v of the Leaf packs? I'm concerned about frying any of the onboard electronics.

That said, I've decided to take this baby to lithium and have ordered:

*7 x Leaf packs 7.6v 64ah
*BMS PCB
*DPDT 48v relay - need 1 or 2?
*Thermal pad

For the shopping list, then, am I correct in thinking I still need to get the following?

*Bus bars/terminal mat
*Interlock - is this needed given my application?
*SB120 connector (can this be reused from cart?)
*2ga wire
*Charger? Happy to convert away from the Lester since it's a beast

[BobBoyce]

The BMS has pack voltage applied. There is a charger port on the BMS where the charger output to the batteries is applied. The interlock is to prevent running the pack too low and causing damage to the cells from over-discharge. Your large charger can still be used, if it can reach near 60V at the end of the charge cycle. You'll probably want to buy a smaller onboard charger whenever you can.

[Bruiser Smith]

Originally Posted by BobBoyce

The BMS has pack voltage applied

Do you mean for charging the pack, or for powering the cart? Or is this what the 48v relay is for? Sorry, I've built other electrical systems but the entire thing was plug & play.

Originally Posted by BobBoyce

Your large charger can still be used, if it can reach near 60V at the end of the charge cycle. You'll probably want to buy a smaller onboard charger whenever you can.

I don't think the Lestronic II charger gets to 60v - it's model 09695 rated 48v 25amp. And is definitely the older style super heavy chargers. They seem to have a 60v model as well so I'm guessing that it won't do 60v on its own. With that in mind do you have a small onboard charger that you would recommend for this setup? I'd love something that didn't weigh 50lbs

[BobBoyce]

48V lead acid pack chargers tend to cut off around 60V +/- 1V

The lithium pack itself powers the BMS on most of the lower end BMSs. You plug in the charger, and the BMS shuts off the charger port when it reaches the charger shutoff voltage. Once the pack is balanced during or after charging, the BMS goes into a low power idle state where it draws very little power. The BMS stays in the idle state most of the time, then checks the pack for balance quickly once in a while, then goes back into idle state until the pack voltage drops to the low power cutoff voltage. Then it shuts off the load (cart). Most people charge their packs before they get anywhere near the low voltage cutoff point. It extends the life of the pack to not run it down too much. When you power up the charger, the cycle repeats.

I used one relay contact to control AC power to shut off the charger, and the other contact to shut down the cart if battery voltage dropped too low.

[Bruiser Smith]

Sorry double post. Deleted