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Old 05-04-2020, 06:59 PM   #21
NCPW
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Default Re: 21 Cell Leaf build

Yes, you can use the BMS16. Keep in mind that every 3 cells will be counted as 1 by the BMS when monitoring.

I would make it a habit to check each individual cell with a DVM periodically to make sure the BMS readings are true and accurate though.
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Old 05-05-2020, 02:35 PM   #22
Tsteak
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Default Re: 21 Cell Leaf build

Quote:
Originally Posted by NCPW View Post
Yes, you can use the BMS16. Keep in mind that every 3 cells will be counted as 1 by the BMS when monitoring.

I would make it a habit to check each individual cell with a DVM periodically to make sure the BMS readings are true and accurate though.
Thanks for confirming!

If I'm not assembling the pack for another week or two, should I have it all connected in parallel in the meantime just because, or is that not important.

Also, looking for on-board Charger recommendations!!!

Thanks!
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Old 06-28-2020, 04:34 PM   #23
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Default Re: 21 Cell Leaf build

Any update on your install? I'm looking into this conversion as well.
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Old 07-03-2020, 02:19 PM   #24
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Default Re: 21 Cell Leaf build

Pack is finally going together, slowly, will post pics when it’s in. I have it assembled with the bus bars made and attached, but I’m out of town and won’t start working on the bms for another week or two. I live in the desert, so it’s around 112* making the cart a somewhat low priority...

I have my metal guy fabricating a “lid” of sorts to help support the pack, and protect it from the occasional accidental splash of water from the cooler that’s behind the seat. Plan to install an aluminum “floor” in the compartment under the seat, and will attach everything to that. Also have bilge fans from a boat going in to protect against over heating; not sure exactly how this will be set up, but the fans are built for 3” ducting, and I think I’ll have a fresh air supply, and an exhaust, and I have thermostatic switches for them...

I plan to post pictures of everything going together when it does...
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Old 09-03-2020, 11:35 PM   #25
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Default Re: 21 Cell Leaf build

Pack is complete. Mission Accomplished!!! -photos to come...

Yesterday was the inaugural run. Drove 6 miles to the course, played 18 holes, and drove home. Arrived home with 40% battery remaining on the ZEVA indicator.

Goal on the project was to build a cart that could go from my house to the course, play golf, and return. Mission accomplished, but there's a "but"... it seemed like, after yesterday's round and input from my ZEVA, that the math was reasonable that I could get to the course and back, with 36 holes played there; I'm not so sure after today.

The current temperatures are a little extreme here in the desert now (110*F,) and that may have an effect, but today the pack shut down due to "low cell" from the ZEVA about a half mile from home. This might indicate that the battery life is not as stout as I had hoped; although I'm not so sure... I checked each cell on the monitor after stopping, and they were all well within range, so I reset and was on my way. I think my "afterburner mode" might be a little stout on its draw at full throttle, and that's what was tripping the system. In the future I might need to switch back into "golf mode" near home (limits the amps to max the cart out at 25mph) so that the controller is not pulling so hard from the batteries. I'll experiment and see... -also, the last 2 miles of the return trip are uphill.

To-and-from the course, I'm running on the streets at 40mph+, pretty steadily for 6 miles; the only break for the system is the inevitable red lights when crossing the major streets. I kid you not, I am running a pretty steady 40-43mph the whole way. This is insane, but the cart is unbelievably stable and not really scary at all; I am surprised I am comfortable at these speeds, but I am. It should be needless to say, I don't recommend going this fast in a golf cart, it is very stupid... but, I am very stupid... (also, my cart is somehow way more stable than most; I've been freaked out at 35 driving other carts and haven't felt a shred of fear in mine... ok, that's a lie, I hit 47.7mph down-hill and that was a little too fast... but at 40, it feels ok to me...)

I wanted to build a 21 module system, because I new going to and from the course I would be murdering the batteries. I have a 600amp altrax, and it devours juice when allowed to open up. My lead acid batteries never stood much of a chance when I engaged "afterburner" mode (which is my name, apropos for this cart, I think, for the speedy side of the personality switch). I wasn't sure what I would get, but figured I would be driving WAY harder than most of our friends here on the forum with 14 module packs, so clearly I needed to go with an extra 7.

I followed McJeffe's model, almost to a tee, accept I skipped a lot of his neat and efficient quick-release, or disconnects he installed, as my 180lb battery pack will not be coming back out of the buggy any time soon. Much of my accessory items are stacked on the main battery lugs, rather than having additional bus bars...

One thing I've incorporated, or at least am in the process of incorporating, are marine blower motors to bring cool air into my battery compartment, and exhaust the hot air above the motor out. On yesterday's first run I didn't use these, as they are loud and kinda annoying, and getting to the course (despite being 110* out) didn't really heat anything up beyond normal temps; after running the motor hard too the course, it cooled quite a lot during play. On the way home though, I had to stop, turn on the fan, and let things cool about ½ mile from home... -it seems that when the cart starts to climb that steady rise of the last bit of my trip home, those extra amps it draws going 40mph are a heavy spend on the batteries... Today before leaving for home I fired up the fresh air intake blower, as I don't have the exhaust installed yet, and it helped immensely. Never got to an overheat scare, but the batteries were drawing low power.

I think I had the ZEVA set at 3.5v per cell for shutdown, I've changed that to 3.2v, as the cells were holding steady WAY above that, but obviously under load they were working too hard. I will see how this plays out and will adjust my driving habits as needed.

I believe intalling the second exhaust blower will be a huge help on my motor. I purchased cheap thermostatic switches to turn these on and off automatically at temperature but realize now, I should probably go with a manual switch. They are too loud to engage on the course, and frankly aren't needed out there. I'll be better off manually engaging them as needed for my crazy commute, and I believe they will help a lot.

Again, I will be posting photos of the project in the next week or two, and speaking to the little nuances of my project, but all I really did was follow McJeffe's 101 page, adding a 3rd module in parallel to the original 7 module leaf build (which is actually 14 cells). My setup is still 58v. max. His awesome schematic works exactly the same for 21 modules as it does for his 14, or even a 7 module setup.

The final numbers have me estimating I will get 30 miles of range from my pack, driving like an idiot. I suspect if I left it in golf mode, or kept it at 30mph or lower, I would get double that.

I can't say enough about the ZEVA BMS. I would not build a pack without one. Knowing how volatile these batteries can be vs. how safe they are when properly managed, the DIY route for BMS was never for me. The ZEVA, in my mind, is worth every penny! -I park this rocket ship in my garage for Christ's sake, it could burn down my whole house if I didn't have ZEVA watching it at all times...

Also, for what it's worth I should reiterate that I built off of a Series cart platform... (2002 Western 400, which is off an EZGO TXT Chasis)
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Old 09-04-2020, 06:01 AM   #26
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Default Re: 21 Cell Leaf build

FWIW....you can adjust your Alltrax controller to limit the amp draw from your battery pack. When I hooked up a laptop on my cart and went for a drive, it showed that on the steep hills the cart was demanding a high of 478amps. I set the controller to draw a max of roughly 300amps. When I drove the same "loop" after adjusting I saw no downgrade in performance of climbing the same hill.

Limiting the amp draw will extend the packs amp usage and allow you to go a bit farther.
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Old 09-04-2020, 10:04 AM   #27
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Default Re: 21 Cell Leaf build

Quote:
Originally Posted by DaveTM View Post
FWIW....you can adjust your Alltrax controller to limit the amp draw from your battery pack. When I hooked up a laptop on my cart and went for a drive, it showed that on the steep hills the cart was demanding a high of 478amps. I set the controller to draw a max of roughly 300amps. When I drove the same "loop" after adjusting I saw no downgrade in performance of climbing the same hill.

Limiting the amp draw will extend the packs amp usage and allow you to go a bit farther.
Thanks, great thinking! I've limited it some but that was before I had the ZEVA touch screen on the dash, which shows the amp draw from the battery in realtime; I'll experiment with those settings.

I'm also telling ZEVA that the pack is 180ah, which could be a touch strong. My modules are Gen 1. I'll learn more in the next few days, as I use the cart more, and get some cycles in...
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Old 09-04-2020, 10:35 AM   #28
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Default Re: 21 Cell Leaf build

Usually.....when\if my cart is calling for max amp's, I'm going up hills of dirt and I'm concentrating on keeping the cart in a straight line and not hitting a tree.
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Old 09-04-2020, 10:50 AM   #29
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Default Re: 21 Cell Leaf build

strange thing just happened. I checked the charge this morning, and the ZEVA had tripped again near full charge with a "high cell" warning. It has done this every time I charge. I reset it and plugged it back in, and after a few seconds it tripped "low cell" warning. Cell 14 (positive end of pack) suddenly went from somewhere around 4.12v to 0.008v.

Anyone got an idea what happened? I've reset the system a couple times but it still reads like that. I'm going to leave it off for a while and see if anything changes, before checking the bms wiring (which will be BRUTAL)...
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Old 09-04-2020, 10:55 AM   #30
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Default Re: 21 Cell Leaf build

Just keep in mind a motor will use as much current as it has access to regardless if it can turn the current into rotational movement.

Once the motor can no longer turn the current into the required torque it will just convert the excess available current into heat.

You can keep the Armature amps at the maximum but lower the Battery amps to the point where You notice a performance degradation.

For Example: Armature Current=600amps, Battery Current =300 amps.
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