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josh843 11-10-2020 10:05 AM

BMW lithium batteries??
 
3 Attachment(s)
Been looking at going lithium for a little while as my T1275’s are just about shot. Came across these today and was wondering if anyone had any opinions on them? Obviously would need a BMS and a charger, but other than that look to be a decent deal if they can be hooked up in series. Also have a higher amp discharge rating than the leaf batteries. Cart is a 2016 rxv with tuned 235 Curtis.

dronning 11-10-2020 10:33 AM

Re: BMW lithium batteries??
 
One issue might be the Maximum Current discharge is only 180A. I've read discussions on only having a max 200A discharge may cause issues. Which would have impact on hills and acceleration.
- Dave

josh843 11-10-2020 10:51 AM

Re: BMW lithium batteries??
 
Quote:

Originally Posted by dronning (Post 1779654)
One issue might be the Maximum Current discharge is only 180A. I've read discussions on only having a max 200A discharge may cause issues. Which would have impact on hills and acceleration.
- Dave

Yes, however there are several people running the leaf packs that only have 130 dischagre with no issues, vs the 180 of these. I figured if anything these would be an “upgrade” at least on that front, over the leaf packs.

Sergio 11-10-2020 11:07 AM

Re: BMW lithium batteries??
 
The Leaf lithium cells have considerably more discharge than 130 amps, not sure where you got that value.

The "continuous" discharge is not a big deal as even upgraded carts use less than 150 amps during cruise speed.

The important number is the peak discharge and duration time as even stock motors can use upwards of 300 amps for several seconds during acceleration.

Most of the issues experience by folks with integrated packs is related to the BMS inability to sustain peak discharge current.

Having a good programable Controller like Alltrax that allows you to set Motor and Battery current independently help mitigate some of the issue with those packs.

josh843 11-10-2020 11:32 AM

Re: BMW lithium batteries??
 
Quote:

Originally Posted by Sergio (Post 1779671)
The Leaf lithium cells have considerably more discharge than 130 amps, not sure where you got that value.

The "continuous" discharge is not a big deal as even upgraded carts use less than 150 amps during cruise speed.

The important number is the peak discharge and duration time as even stock motors can use upwards of 300 amps for several seconds during acceleration.

Most of the issues experience by folks with integrated packs is related to the BMS inability to sustain peak discharge current.

Having a good programable Controller like Alltrax that allows you to set Motor and Battery current independently help mitigate some of the issue with those packs.

Thanks for clearing that up for me Sergio, I saw somewhere on some website that it had the maximum discharge for the leafs at 130, may not have been “peak” discharge and I’m not even sure what generation leaf it was that I was looking at. Is there anyway to easily find what the “peak” discharge would be on these BMW batteries? I would imagine it’s a fair amount higher than the maximum discharge, and also how do you think these would work with the zeva BMS?

Sergio 11-10-2020 01:26 PM

Re: BMW lithium batteries??
 
This site say they are good for 600 Amps for 10 seconds, that is more than enough for a good acceleration.
https://batteryhookup.com/products/b...35161014894754

Zeva is a nice BMS but the complete setup is on the upper range of prices typically used for golf carts.

You need to make sure they include balancing cables to make the connection to the cells easier.

You need to find a good central location to place the BMS in order to keep the balancing leads somewhat even.

You need to be very careful not to disconnect the batteries from each other if the BMS leads are still connected to the BMS or it could cause an issue with the small gauge wire used for balancing.

It will not be the easiest setup to implement, I prefer individual cell/modules like the Leaf or just buy new LifePO4 cells like many users are doing now and You will have a better system that those pre-fabricated units with unknown components inside.

jhornbr225 11-10-2020 08:05 PM

Re: BMW lithium batteries??
 
2 Attachment(s)
I'll chime in as I just got some from that series from Battery Hookup on Saturday.

I ordered 4x 5s modules, and 2x 4s modules, to make two strings of 14s. I also ordered 2 of the 100A BMS modules they have, as they claim they have modified firmware for low temp cutoff. I knew I would not be running full motor amps through the BMS. I've ordered the parts to build the HV-LV cutoff/charger isolation circuit ala Sergio.

In my reading since I ordered the batteries, I have determined that having two separate strings is not a good idea, even with separate BMS's. I now plan to parallel these up at the cell level. I took the plastic covers off one each of the 4s and 5s modules to get a plan on how to use heavy cable to parallel up the cells. Looking at the busbars, I see that the individual cell terminals are welded to the busbars. This would have been much easier if they were bolted to the busbars. My current plan is to use a dremel and make a slit in the busbar, and bend it up to a 90°. Then I can drill a hole in it for the lug. It appears that there is about 1/4" below the busbars, so I don't have to be too worried about cutting into the cell with the dremel. The 5s one will be pretty easy, as the pack + and - terminals are on opposite sides of the pack. I plan on using the BMW factory cables that Battery Hookup sent along with the modules. On the 4s however, the + and - terminals are on the same side of the pack. That makes space a little tight to be able to plug and unplug the factory terminals one I bend a tab up. On that one I'll have to make a slit, and bend it away from the pack's positive terminal. Of the 6 cables they sent, there are four 90° plugs. If I use one of those there, I think I'll have enough room. For the module's + and - terminals, I may have to cut one of those cables in half, and then put those cut ends into a power distribution block. That way I can have another connection over to the like connection on the parallel cell. I'd say drill a hole in the module + and - tab, but if you don't, you have nice easy plugs to completely isolate power. I'll also cut slitss in the plastic lids for the bent up tabs to go through. Less exposed busbar that way. I'm sure this would all make more sense with a picture. Pics attached.

Yeah, 10 seconds of 600A per 14s string would give the capability of 1200A! You just need to be really careful cutting the slits. And then brace the cables so they don't continue to pull on the tabs and bend them back and forth.

I'll be installing these in a 92 EZGO Marathon 3 Wheeler. Doing some planning on that respect today, I found that I might have to modify the angle braces going to the floor of where the batteries sit. With 6 of those batteries it's going to be a tight fit.

josh843 11-11-2020 07:42 AM

Re: BMW lithium batteries??
 
Quote:

Originally Posted by Sergio (Post 1779708)
This site say they are good for 600 Amps for 10 seconds, that is more than enough for a good acceleration.
https://batteryhookup.com/products/b...35161014894754

Zeva is a nice BMS but the complete setup is on the upper range of prices typically used for golf carts.

You need to make sure they include balancing cables to make the connection to the cells easier.

You need to find a good central location to place the BMS in order to keep the balancing leads somewhat even.

You need to be very careful not to disconnect the batteries from each other if the BMS leads are still connected to the BMS or it could cause an issue with the small gauge wire used for balancing.

It will not be the easiest setup to implement, I prefer individual cell/modules like the Leaf or just buy new LifePO4 cells like many users are doing now and You will have a better system that those pre-fabricated units with unknown components inside.

Thanks, great info. I may end up going with individual modules after reading this and the post below lol. Individual modules seems like a tad more straight forward process. Thanks again

Quote:

Originally Posted by jhornbr225 (Post 1779828)
I'll chime in as I just got some from that series from Battery Hookup on Saturday.

I ordered 4x 5s modules, and 2x 4s modules, to make two strings of 14s. I also ordered 2 of the 100A BMS modules they have, as they claim they have modified firmware for low temp cutoff. I knew I would not be running full motor amps through the BMS. I've ordered the parts to build the HV-LV cutoff/charger isolation circuit ala Sergio.

In my reading since I ordered the batteries, I have determined that having two separate strings is not a good idea, even with separate BMS's. I now plan to parallel these up at the cell level. I took the plastic covers off one each of the 4s and 5s modules to get a plan on how to use heavy cable to parallel up the cells. Looking at the busbars, I see that the individual cell terminals are welded to the busbars. This would have been much easier if they were bolted to the busbars. My current plan is to use a dremel and make a slit in the busbar, and bend it up to a 90°. Then I can drill a hole in it for the lug. It appears that there is about 1/4" below the busbars, so I don't have to be too worried about cutting into the cell with the dremel. The 5s one will be pretty easy, as the pack + and - terminals are on opposite sides of the pack. I plan on using the BMW factory cables that Battery Hookup sent along with the modules. On the 4s however, the + and - terminals are on the same side of the pack. That makes space a little tight to be able to plug and unplug the factory terminals one I bend a tab up. On that one I'll have to make a slit, and bend it away from the pack's positive terminal. Of the 6 cables they sent, there are four 90° plugs. If I use one of those there, I think I'll have enough room. For the module's + and - terminals, I may have to cut one of those cables in half, and then put those cut ends into a power distribution block. That way I can have another connection over to the like connection on the parallel cell. I'd say drill a hole in the module + and - tab, but if you don't, you have nice easy plugs to completely isolate power. I'll also cut slitss in the plastic lids for the bent up tabs to go through. Less exposed busbar that way. I'm sure this would all make more sense with a picture. Pics attached.

Yeah, 10 seconds of 600A per 14s string would give the capability of 1200A! You just need to be really careful cutting the slits. And then brace the cables so they don't continue to pull on the tabs and bend them back and forth.

I'll be installing these in a 92 EZGO Marathon 3 Wheeler. Doing some planning on that respect today, I found that I might have to modify the angle braces going to the floor of where the batteries sit. With 6 of those batteries it's going to be a tight fit.

Awesome write up! And also great info as well, Thanks!

jhornbr225 11-16-2020 09:31 AM

Re: BMW lithium batteries??
 
1 Attachment(s)
I pulled the Lead Acids out yesterday, and started actually trying to get these BMW Lithiums to fit.

The attached pic shows the two 4S and one 5S sitting in their intended spots.

First thing I see is that these are much shorter than the Trojans. That's good as I'll have to be a little creative to get them to fit. You can see in the pic that even though the one is sitting on the angles that held the Trojans, it's still under the stock F/R switch. And that area will be cleaned out, as I'm only going be using the little switches from the stock F/R switch.

With a little spacer under the one 4S so that it will clear the throttle linkage, I think I can put the two 4S batteries sideways across the front. A 5S will then fit behind each of them with no other mods.

I then have to put a 5S in the outer spaces. They are too long, so it starts to infringe on the splash guard/leaf spring mount area. There is a diagonal brace to the floor which would need modified. The good thing is that since these are not open topped and full of acid, I believe if they are on a slight angle, that it is no big deal. And since they are so short, I won't have any seat clearance issues, even if they are on an angle.

I do plan to keep the stock forward/reverse switch. I have the reversing contactor kit, but I plan to use the stock switch to operate it. So I hope the space behind the 4S batteries, and in front of the stock contactor/controller will be enough room for all my bigger parts (Alltrax 48500, SW200, and SW202). I also have an enclosure for the BMS/HV-LV cutoff relays ala Sergio to fit somewhere. I can tell I'm not going to have room for an on-board charger, unless I put in in the back footwell, which I am not prepared to do. My typical use case is I'll never be more than 1500 feet from home base. Unless for some reason there is room on one of the wheel splash guards, but with those big batteries on the sides, I'm not counting on it.

In pulling the second 4S out of it's box, I see that I missed another cable, and it's got a 90° connector on it. Score! Now I have five 90° connectors. That might come in handy.

I don't know where I am on weight reduction either. I read somewhere that the Trojans are 63lbs each. According to Battery Hookup, the four 5S batteries each weigh 34lbs, and the two 4s each weigh 28lbs, for a grand total of 192lbs. On paper that's a 186lb reduction. I used a Cherry Picker to lift the Trojans out, but I was muscling in the Lithiums for the tests.

morvolts2 11-24-2020 09:32 PM

Re: BMW lithium batteries??
 
I have nothing to add,other than make sure you sandblast the entire battery compartment.
I used 1/8 inch aluminum plate cut the same size as the battery rack to fill the holes and allow for some wiggle room.


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