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Discussion Starter #1
I don't know if I should post this in this forum or in the batteries forum since technically the side of the cart I am working on is already electric. So, mod's if I belong in the batteries sub forum, please move my post.


I am working on a 2016 Textron/Ez-Go/Bad-Body Ambush iS, It is a dual drive golf cart. (Front electric, Rear Gas, or both for 4wd)

I am getting rid of the wet cell batteries which are 8x 6v 220ah (trojans?) and I am replacing with

2016 Tesla S packs (444) 6s 74p 24v 233ah packs. My plan was 3/3 parallel. (Or possibly 4/4 parallel) this gets into my questions/lack of knowledge. I am told 3/3 parallel, 6 total, will drastically increase my range while saving the most weight. (Removing over 500lbs and going back with 250lbs). 4/4 I'll be getting back into the same weight but range will be increased all the more and I am looking for suggestions here.

Also it was suggested that I charge them with 3x EV Peak A9 Chargers and use the chargers 12s function splitting 6s and 6s (one to each battery of the parallel) and making those connections x3.

I have some strong 13.6v 50a power supplies to run the chargers already in my shop to power the chargers mentioned above but I would like to build something self contained that is plug and forget. If I wind up saving enough weight and I am able, I would really like to mount the charging system under the "hood" of the cart where it housed 2 of the old wet cell batteries.

I would also like one of the battery pack health displays mounted on my dash or steering wheel and need some suggestions where to look for that and how it wires in. Do I buy some type of splitter where the balancer plugs in to the battery pack and run one to the display and one to the charger?

Also, I was told to protect these batteries from moisture and temperature extremes. My intention was to build a water tight box under the operators seat to mount the batteries in and I was considering a small inline 12v water heater and designing a closed cooling/heating system to keep the batteries between 50-90f as suggested. Is this realistic. I was told never to charge the batteries when cold and to charge them slowly when at the lower end of their temperature range.

Can you use them when they are cold? Can I operate the golf cart when it is freezing out or will I need this heating system running anytime the batteries are cold - then drawing on my capacity to run the heating element and water pump).

I could also start the gas motor and tap into the cooling system on it but that defeats the whole purpose of "beefing up" the electrical system so I rarely if ever need to use the gas drive again (Hopefully only if I ever need 4wd).

I'm sure this message is scattered. I tried in my limited knowledge to convey what I've heard and ask questions. I'm a newbie. And I am using the search button but I can't find anyone that has used the tesla packs to convert a golf cart. The only times I've found them being used is in vehicle conversions and they are almost always being used in series to get the voltage up over 100v DC.

Thanks in advance to anyone that takes the time to answer any of this or offer any suggestions.
 

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I converted my Tomberlin Vanish from lead acid to lithium - with your vehicle and lead acid set you have to take into account the Peukert gain, which means that 220ah of Trojan battery is really nowhere near that capacity. To fit 6 Tesla modules on a golf cart would be pure insanity, not to mention salvage prices on tesla modules are over $1000/piece.

My recommendation for this conversion to lithium would be to use Chevrolet Volt modules - a pair of 2kwh modules tied in parallel which are 12S and 50.4V peak. This will get you significantly further than you think when you factor in the weight reduction from dropping several hundred pounds of lead acid cells and going to a pack that weighs 80lbs. The charger fitted to the unit can likely be reprogrammed if it's an Elcon - even though it is a 48V charger and your batteries peak at 50.4V it needs to output that or less. My vanish uses exactly this setup and has around a 15 mile range, but keep in mind it is a full size 4x4 UTV (based off a 700cc polaris ranger). I sourced a custom harness that parallels the BMS ports as well, so it balances both modules when it is charged. If you don't have access to the controller software you will simply need to monitor voltage of your battery so you stop driving it before you get below at minimum about 3V/cell (there are endless arguments on this forum how low to go). I don't remember if I posted the battery build on this forum or another, but you may be able to search for it to see what comes up. Sourcing the cells, passive BMS, harrness, and reprogramming the charger could be done for about $700.
 

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Discussion Starter #3
Thank you very much for taking the time to reply to me. Wonderful food for thought and some new things to search, learn and understand. Unfortunately I have already started acquiring the tesla packs, I was just asking where to stop. And I think with what you've told me, I already have more than enough.

The EV side of my cart is 48 volts. I guess this is something else I don't understand. I know some of the newer carts are now 72 volts but my understanding was I needed to match the voltage or it would require replacing the controller for the motor. (It has the newer AC motor and controller that comes on the new EZ-Go/Triton carts.

I am starting to understand just how much I've over done it with battery packs when I watched a conversion video and someone was converting a minivan with 8 of these same Tesla packs.

My cart is full sized. Initally a 4 seater but I've done away with the back seats and built a skid that holds a full size ambulance stretcher. I've also added patient lighting in the back so it can be used at night when transporting patients and whoever it tech-ing (treating the patient) can see what they are doing.

I am hoping for a VERY long range, or "over done" system. I planned on doing away with the 12 volt system for the gas side of the cart all together and just using a couple of 48v-12v converters with 50a ratings to start and run the gas engine, and run the headlights, emergency lights, siren, patient lights and the low wattage heating system I was speaking of to maintain battery temperature. I will measure to be certain but I don't think the starter pulls more than 100 amps. (I forget the displacement but I think its around 500cc twin cylinder Subaru engine) and I know the rest of the lighting all put together (everything on) pulls under 10 amps. The siren pulls around 20 amps. I want to know for sure that I can use this thing all night - a 12 hour shift wherever I am working, be able to run all my equipment and not have to worry about recharging it. Again, in a worst case scenario I can just switch over to the gas system. It also has a built in regenerative system on the electric side so if you drive it around in gas mode it will recharge its electric side. (I assume this will still be usable).

Thank you again for your reply. I'm here searching and trying to learn some more.
 

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Discussion Starter #4 (Edited)
I guess a better question to ask you guys is: If price were no object and you were converting YOUR golf cart how would you do it? I don't really want to use used packs unless I have to.

I have already started acquiring 24v 5.2 kwh tesla packs but as I get into BMS, wiring that up and the charging system then designing a cooling/warming system I am wondering if I am spending more money than I need to for the same effect.

I started looking at complete kits from batteryspace.com. They have the modules I have seen in other electric conversions. their 200 and 400ah 3.2 giant modules that they ship in packs of 4 - something to do with safety constraints.

What I don't understand, or I am trying to - and please believe I am searching and reading. Is how to compare the different packs.

How does 6 Tesla packs that are 6s74p 24v, 5.2kwh that I would run two banks of 3 parallel and then series the top two 2 for my 48 volts compare with say battery systems 200ah 48 volt system that is composed of 16s 1p 3.2v 200ah packs. they show a total kwh of 10. But wouldn't my tesla packs be a total kwh of 31.2?

The battery systems setup comes with everything. A BMS system and a charger so its literally design and weld up a tray and then bolt all the buss bars together and connect my existing system controls.

The tesla system, I've acquired the chargers (3 to speed up charging time) but I have to create the wiring and wire the system up. - Which is not the end of the world, I'm find with welding, soldering, heat shrink, making good connections and things of that sort. I used to build ambulance electrical systems so I have a decent base of knowledge of wiring, making harnesses and stuff like that.

What I want to understand is what is the strongest system I can or put together for the money. And what will give me the most reserve. This golf cart will be used as a miniature ambulance. It will have a stretcher lock, patient lighting, an inverter to charge the cardiac monitor, emergency lights, and sirens (all of this is already in place). I will probably install a 5000w inverter to run the 120v system on the cart so if its winter time I can add on my rain panels, keep it somewhat enclosed and run a 1500w space heater to keep me and IV fluids and such warm. It may eventually get some type of HVAC Air Conditioning system as well mounted on the roof (a RV type system).

I plan on doing away with the 12 volt battery system completely that runs the gas side of the cart and instead use a 48v to 12v converter for engine starting. I won't need the 12v charging system off of the gas motor anymore I wouldn't think.

The system I build needs flexability. The AC motor has selective regeneration already built in. I would like to continue to be able to use that. I will most likely add on a solar system to the roof of the cart so the system can charge some when I am sitting outside on a gig - or if its just parked outside during the day.

I need MAXIMUM reserve capacity that I can fit into the cart - while hopefully saving some weight. As stated, the system will run several additional high draw components at some point.

I may even use it as a house back up battery system if the power ever goes out. It would be nice to be able to plug the inverter in to a auto switching sub panel at the house. Thats not a necessity - just a thought.

So, if it was yours, and you could spend what you wanted to - and it would all be a tax write off, what would be the MOST ROBUST system you would put together? Which batteries would you use?

And how do I compare the numbers. That is what I'm having the hardest time understanding. The 16s 1p system is 200ah period. Right? It doesn't matter that there are 16 of them. The additional AH comes with parallel batteries added in to the system. Correct?

My level of understanding and skill with 12v systems is between moderate and expert. My understanding of 120v/240v AC systems is moderate.
My understanding of battery capacity, how to understand KWH, Amp hour ratings, reserve capacity, etc. is infant newb.

Any and all help would be appreciated. Again, thanks in advance.
 

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Discussion Starter #5 (Edited)
A small update:

Some of the people that I've talked to say do not run the Tesla (or any) packs in parallel. That you run into problems that you need an Electrical Engineer to solve. They say you wind up needing triple the BMS systems to read and control the packs and that you drastically reduce the amount of usable power due to "that one weak cell" so I've changed my design idea. again. I guess this happens a lot in one of these projects. I also, as stated above started looking at new packs and found that for the price, weight, and strength of packs I won't come close to the Tesla packs without spending triple the money, custom ordering something from china and waiting 6 months for the parts to arrive via slow boat. (or spend 10k in shipping...)

So, my new thoughts are (and this is pack only, I still haven't decided/completed my heating/cooling system or the battery box design)

4 tesla packs total in two separate battery banks. Both batteries in each bank are in series for 48v. and the pack banks are selectable with a battery switch (like what you'd find in a boat, ambulance or RV. So, Bank 1, Bank 2, or both (never using both) are selectable.

Orion's BMS Jr CAN driven design). to balance, charge and monitor the packs, one for each. 2 Delta Q 48v chargers to charge packs controlled through the Orion Jr. BMS. and 4 of the Stealth EV Tesla BMS boards for easy connection to the Orion BMS system. This accomplishes the same concept I was after before, depth of system (extra capacity) for increased range, etc. while avoiding the problems with parallel packs that I don't understand completely.

Does anyone have any thoughts on this set up? I've returned the original chargers I purchased because, while nice, they do not have any type of power supply and the bulk of trying to install a 100amp or two 50 amp 12v power supplies to run the chargers seems foolish when I can buy chargers with the power supplies built in and take up a lot less room, save weight, etc. also, the Orion BMS will talk directly to the Delta Q chargers and control them completely. Also the Orion has a few extra programmable outputs that I intend to use to trigger relays to open and close different portions of the battery heating and cooling system depending on what needs to be done, and they can be programmed to handle the changes to that system automatically when pack temps reach certain temperatures.

Any thoughts?

I hope, when done, to have a very robust,dependable long range system that will work like I want it to, save weight and be completely safe and dependable.

I welcome any opinions. again.
 

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Hi
I would run the Tesla packs together in parallel - you could run them as separate packs but I don't think that you will gain much

Tesla - or Volt packs are simply tons better than "Brand New" batteries! as the OEM's have done a lot of selecting and testing

The general experience with "new" cells from China has been about a 4% failure rate
 

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Discussion Starter #7
Hi
I would run the Tesla packs together in parallel - you could run them as separate packs but I don't think that you will gain much

Tesla - or Volt packs are simply tons better than "Brand New" batteries! as the OEM's have done a lot of selecting and testing

The general experience with "new" cells from China has been about a 4% failure rate
That is very interesting that you say to go ahead and run the packs in parallel. This was my original idea. I’ll post that email that I got from BMS that said it’s dangerous to run the packs in parallel, it’s extremelt difficult to then monitor them with a BMS system and that you’d basically need to run your BMS systems in triplicate to be remotely safe AND I’ll need to hire an electrical engineer to do the math to set the safe charge discharge levels for the packs and that I would lose around 20% capacity doing it this way. I know I’m misquoting a little bit. I’ll find the email and post it here. I’m truly curious to hear the answers from some of you guys that know what you’re talking about. But basically my original plan was to run the packs in 3/3 parallel with the last 2 in series for 48 volts with the depth of 6 packs total. And I was told I’d need a BMS jr for EACH parallel pack (6 total) and then a master BMS 2 over all of those with disconnects between each pack, etc etc. it was going to be a 8-10 thousand dollar charging system.

Then I’ve also heard from some real world people that it isn’t a big deal to run the packs in parallel. My question is how to you accomplish battery management and balancing of parallel packs?
 

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Hi Ditchdoctor

Here is my (minority) view

There are BMS's that are fitted to production EV's
And there are "other" BMS's

The production ones are good - the others are more likely to kill your battery than save it

If you are using batteries from a production EV then they don't NEED a BMS
But they do need to be checked occasionally

Batteries from production EV's don't "go out of balance" - so the balancing feature is not needed

Additionally you CAN'T balance a battery until you charge it to 100% - and that is BAD for the battery!

What you need is warning if something happens to your battery
I use the
http://www.evdl.org/pages/battbridge.html

And I check each cell every six months

With only 48 volts you could have a voltage readout on each cell!

So far I have been using my Volt battery pack for about 3 years - I do abuse it a little - I draw 1200 amps!
But so far it's all still in balance
 

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Discussion Starter #10
Hi Ditchdoctor

Here is my (minority) view

There are BMS's that are fitted to production EV's
And there are "other" BMS's

The production ones are good - the others are more likely to kill your battery than save it

If you are using batteries from a production EV then they don't NEED a BMS
But they do need to be checked occasionally

Batteries from production EV's don't "go out of balance" - so the balancing feature is not needed

Additionally you CAN'T balance a battery until you charge it to 100% - and that is BAD for the battery!

What you need is warning if something happens to your battery
I use the
http://www.evdl.org/pages/battbridge.html

And I check each cell every six months

With only 48 volts you could have a voltage readout on each cell!

So far I have been using my Volt battery pack for about 3 years - I do abuse it a little - I draw 1200 amps!
But so far it's all still in balance
Well this has the potential to be very good news and thousands of dollars of savings. Tell me, how do you charge them? Do you just set a max voltage on the charger and that’s where it cuts off? Say 48.4 volts or something like that? I bought a couple of cheap voltage / amperage monitors, it would be easy to wire one per pack. It’s even better news that I can safely run them in parallel and not worry about it. What’s with the guys from Orion? Do they just want everyone to waste a fortune? They really had me worried. I think I’ll just charge these packs one at a time for now and do exactly what I said, 2 in parallel and 2 in series and hook up voltage monitors to the built in taps and see how it goes. Keep and eye on the thermistors, make sure they don’t get too cold and stop over thinking everything. Thanks for the advice everyone!!
 

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I respectfully disagree with Duncan in the fact that production EV packs don't go out of balance - they will with enough cycles. If they are from the same Tesla battery pack, they will be much less likely to drift apart from each other if you are paralleling. Could you get by without a BMS for your application? Sure!
I personally would create a harness that utilizes the factory ports (I do not know what the Tesla packs have, I haven't personally gotten ahold of a module) that parallels them through the harness. This can only be done when the packs and cells are charged to exactly the same voltage, or you will create a potential difference between modules and fly the small harness wires when you plug them in. Once this is done, you only need to monitor 12 cells as it will bridge across 3 blocks in parallel and treat it like a single cell. Since that much work has been done it is not much extra to add a BMS to the system. Chargery makes a nice unit I've been using for a couple years on a 24S Chevy Volt bank.
To answer your charging question - I had Delta Q reprogrammed to something like 48.3V or whatever that profile was.
 

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I believe the BMS in the modules has to be told what to do from a CAN signal - it would be sweet if it just worked on it's own though... which again I'm pretty sure it isn't.

Ditchdoctor asked what would be the most robust system as well - used Tesla modules would be it IMO. I only use Volt modules/CMAX modules in my projects because they are so cheap! $80/kwh VS $200ish.

I also recently got ahold of a Ford CMAX ENERGI battery - it would be super easy to build a custom pack with the cells in there, since they have a very modular shaped cell with threaded terminals. Could parallel/series with the terminals making for a much safer pack. The cells in there are 26AH.
 

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I believe the BMS in the modules has to be told what to do from a CAN signal - it would be sweet if it just worked on it's own though... which again I'm pretty sure it isn't.
Not CAN, see:
https://www.diyelectriccar.com/forums/showthread.php/fs-tesla-vw-outlander-bms-master-198263.html

I also recently got ahold of a Ford CMAX ENERGI battery - it would be super easy to build a custom pack with the cells in there, since they have a very modular shaped cell with threaded terminals. Could parallel/series with the terminals making for a much safer pack. The cells in there are 26AH.
These are very good cells. just remember a couple of things:
-keep compressed (using original mounting 'racks' would be perfect)
-isolate the cell housings as they can / will show voltage
-if you know that socket fits the strange 12 lobe nuts...please tell me ;)
 

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boekel- good advice on the CMAX cells! As far as the nut, it is an 8mm triple square. NAPA was the only place that was able to even order one for me, and I ended up just using an easy-out that fit them perfectly when I took a bank apart. I never ordered the socket - so it still may not even be correct... but I'm fairly sure that is what it is. Triple square is most common on VW cars, but typically they would need a triple square bit instead of a socket.
 

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Just to make it clear
I am NOT saying don't have BMS
I am saying that I am the BMS for my pack

There are two separate issues
(1) Going out of balance
A regular check will catch that - and then the cells can be rebalanced
(2) A cell failing
This is the problem that can lead to overcharging - and the Batt Bridge will catch that

With production EV batteries both of these will be rare

"New" batteries (not from EV's) die at a frightening rate - 3%+

But "BMS" systems historically have killed at least as many

BMS systems have killed lots of batteries and I don't believe that they have saved ANY
 

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I completely agree with you Duncan that the salvaged cells from major auto manufacturers fail less, quality control is essential in not driving warranty costs through the roof for the big car companies. I think lot of my bias towards using an actual BMS likely comes from the first battery pack I built out of 18650 cells harvested from old laptop batteries... terrible idea! That thing was all over the place out of balance all the time! Definitely no consistency there like an auto pack.
 

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-if you know that socket fits the strange 12 lobe nuts...please tell me ;)
As far as the nut, it is an 8mm triple square.
...
Triple square is most common on VW cars, but typically they would need a triple square bit instead of a socket.
A socket (female, fits over a nut or the head of bolt), or a bit (male, goes into recess in bolt head)?

Triple-square or 12-point internal drive bits are readily available online and in stores with automotive tools (just web search using those terms)... just don't get Torx or spline, which which would be very different.
 

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Brian - you are correct the triple square drive bits are readily available everywhere... the socket is much much harder to come by which is what this requires. As I mentioned, I used an "easy-out" which fit perfectly and didn't seem to damage any of the nuts on the terminal posts. Odd choice of nut for Ford, as Chevy Volt just uses a nice hex fastener...
 

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Brian - you are correct the triple square drive bits are readily available everywhere... the socket is much much harder to come by which is what this requires. As I mentioned, I used an "easy-out" which fit perfectly and didn't seem to damage any of the nuts on the terminal posts. Odd choice of nut for Ford, as Chevy Volt just uses a nice hex fastener...
Thanks :)
I was puzzled because "easy out" usually means a screw extractor, which is a tool which goes into fastener's recess, or a hole drilled in a screw head for this purpose. An extraction tool which goes over a bolt head is normally called a nut extractor or remover, or bolt extractor or remover.

Double-square socket are certainly less common than the bits; even Snap-On only has them in inch sizes, not metric... although a 5/16" might fit those 8 mm nuts. The only 8 mm example that I found quickly online is from Genius Tools and available at Sears (until they go completely bankrupt and shut down).

Odd choice of nut for Ford, as Chevy Volt just uses a nice hex fastener...
In some cases an unusual fastener is used just because it is unusual, and so discourages people other than dealership techs from messing with them.
 
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