50 cal ammo can batteries

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MBF Dan

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May 14, 2021
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35
I have a small farm. I am just starting to collect cells to convert my first small garden tractor to electric. It will have a 4kw motor probably 48volts DC. It is a case ingersoll 448 tractor. I posted a photo of the tractor in my hello world thread. This is the first tractor I plan on converting as it will have the simplest electronics and lowest power requirements but I want a common battery design I can use with my next project tractor which will be a farmall H. That tractor is about 22hp at the pto. I honestly don't know how big a motor I would want to install in it at the moment.

So my plan is to have 20kwh of batteries for the case ingersoll tractor which will give me 5 hours running time about equal to what the current fuel tank will hold in diesel fuel. It will also keep the discharge to 0.5C which seems wise with used cells and no active cooling system.
I have watched a few YouTube videos where people built a battery inside these 50 cal military surplus ammo cans. I like the idea because they are not too expensive and come to about 25lbs when fully assembled. That makes them easy to handle.
I haven't gotten the cell holders yet as I have just been planing and just started collecting cells. But from the videos I saw you can put two packs of about 100 cells side by side in the ammo case.
My concept is to build two separate packs of cells all in parallel then bring a connector outside the ammo case for each pack. This will allow me to connect the packs of approximately 100 cells in any configuration I need for the application. In my first application it would probably be 14S200P meaning I would connect both packs in one ammo case in parallel outside the case.
I would have the BMS system built into the tractor and each plug on the tractor would be wired to the BMS as well as connecting the packs into the serries configuration needed to reach the correct voltage for the system. The only major downside I see to this concept is that I don't have thermal monitoring without adding more hardware.
I have also wondered about charging and balancing at the cell level instead of the higher pack voltage level. It seems to me that if I could unplug the packs and plug them in to a charger for a single parallel group of cells I could ballance the entire pack by simply fully charging each group of cells. I get lower voltage is higher current but 14 separate chargers or 1 14S charger would have the same power requirements. Anyway before going too far down the rabbit hole I just wondered if there was a system with that type of design out there. I could see how it could be done with a multi tap transformer and several charge controllers. But I didn't know if someone had tried it.
 

floydR

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Aug 23, 2017
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I would advise getting the cells in one or two lots. Laptop cells won't be good enough. A icharger 4010duo could charge two 7S sections at once you would need a good power supply ~2000W~2500W The cells would need to be high discharge cells. The icharger is a balance charger. It can be pretty much whatever type of charger that you want. Or a more modular approach is getting 2 Icharger X8/X12 and two ~1000W power supplies. Can you tell I like iChargers? Have an X8 and a 1010b+

Battery powered tool batteries would work. A better option are what I am told are bus batteries https://batteryhookup.com/products/36v-48ah-1776wh-spim08hp-36v-power-moduleSPIM08HP Lipos bhu has in individual cell,packs of cells, a 36v 10S6p blocks. 18650's like I said power tool cells BCH has some 20A cells https://www.batteryclearinghouse.co...h-high-drain-20a-cells-in-a-tool-battery-pack There are many opitions in LiFePO4's too. cool little tractor you have there.
Later floyd
 

OffGridInTheCity

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Dec 15, 2018
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1,706
20kwh useable power is on the order of 2,800 18650 cells. That's a lot of ammo cans. Maybe a larger base container and do 3 x batteries of 14s70p of 2600mah cells (about 1000 cells) for 8kwh each which would be aprox 100lbs each. This would be 14s210p in total and at 0.5a / cell (reasonable) you could deliver 5000w continuous power for 4-5hrs.
 
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cak

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Mar 14, 2021
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49
Hello Dan, I am excited to hear about your projects and am working on similar projects myself. I would love to converse more directly if you are interested. I read your other post as well and very interesting and it seams like you are working on a just slightly larger machine and with a lot me expertise than me :)

A few thoughts and things I have learned as I built my first couple prototype AmmoBats as I am calling them. High Quality Cells that are high drain designed are essential for good amp output. My first prototype I used my low grade cells since I figured I would learn a lot building it and didn't want to waste my good cells and one of the things I learned is that low grade cells have a very high voltage drop under a medium to high (3-5amp/cell) load. My second prototype I used electric bike/moped recovered cells and they are working much better so I am now hitting my designed specs. I love the ammo can form factor and size and it is perfect size for 18650 (13*8*2). I considered a lot of the tradeoffs and right now my primary design is 7s26p with 90amp max discharge(limited by my plugs and wires so maybe some headroom here), 66 Ah capacity at 25.2vdc nominal so about 1700wh. I wanted to keep each AmmoBat at the 24volt range since that is most compatible with chargers and small electronics and since I plan on using the same pack design(and even packs) for other things like portable power station for power tools and a wall tent... I am also planning on converting a walking tractor to electric and in that use would put 2-3 of my AmmoBats in series to get 48 or 72 volts respectively for the big motor. I researched motors and like this one https://www.goldenmotor.com/frame-bldcmotor.htm although it is expense and would probably do 72volts for best efficiency. For my walking tractor I would just have three AmmoBats at a time providing 5kwh which would only run for half and hour at max draw but looking at real world scenarios I bet it would run for around an hour or more. I would rather swap batteries out and save on weight.
 

MBF Dan

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May 14, 2021
Messages
35
20kwh useable power is on the order of 2,800 18650 cells. That's a lot of ammo cans. Maybe a larger base container and do 3 x batteries of 14s70p of 2600mah cells (about 1000 cells) for 8kwh each which would be aprox 100lbs each. This would be 14s210p in total and at 0.5a / cell (reasonable) you could deliver 5000w continuous power for 4-5hrs.
I did look at some bigger cans but I plan on using these batteries with a couple different tractors. So I would rather keep the weight down and move more cans. It also gives me more options on connectors if I have one connector for about 100 cells in parallel i can keep the current draw to 100 amps max per connector and only be at 1 amp per cell which is actually about twice what I want so a 100 amp connector typically seeing 50 amps and 0.5 amps per cell is what I was hoping for. My goal is 5 hours running on a tractor that is a very typical running time on my farm.
I am figuring I will be at either 14 or 21 cans for the 20kwh system depending on what the capacity comes out to. So either 2 or 3 packs inside the cans in parallel for a 14S system. The other advantage of the smaller cans is they fit the frame of my case ingersoll nicely. The bigger ones actually are harder to stack on the tractor.
 

MBF Dan

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Joined
May 14, 2021
Messages
35
Hello Dan, I am excited to hear about your projects and am working on similar projects myself. I would love to converse more directly if you are interested. I read your other post as well and very interesting and it seams like you are working on a just slightly larger machine and with a lot me expertise than me :)

A few thoughts and things I have learned as I built my first couple prototype AmmoBats as I am calling them. High Quality Cells that are high drain designed are essential for good amp output. My first prototype I used my low grade cells since I figured I would learn a lot building it and didn't want to waste my good cells and one of the things I learned is that low grade cells have a very high voltage drop under a medium to high (3-5amp/cell) load. My second prototype I used electric bike/moped recovered cells and they are working much better so I am now hitting my designed specs. I love the ammo can form factor and size and it is perfect size for 18650 (13*8*2). I considered a lot of the tradeoffs and right now my primary design is 7s26p with 90amp max discharge(limited by my plugs and wires so maybe some headroom here), 66 Ah capacity at 25.2vdc nominal so about 1700wh. I wanted to keep each AmmoBat at the 24volt range since that is most compatible with chargers and small electronics and since I plan on using the same pack design(and even packs) for other things like portable power station for power tools and a wall tent... I am also planning on converting a walking tractor to electric and in that use would put 2-3 of my AmmoBats in series to get 48 or 72 volts respectively for the big motor. I researched motors and like this one https://www.goldenmotor.com/frame-bldcmotor.htm although it is expense and would probably do 72volts for best efficiency. For my walking tractor I would just have three AmmoBats at a time providing 5kwh which would only run for half and hour at max draw but looking at real world scenarios I bet it would run for around an hour or more. I would rather swap batteries out and save on weight.
Interesting it sounds like you are much further along in practical experience than I am as far as collecting cells and building.
I did buy 10 lbs of tool batteries from battery hookup and was less than impressed. Maybe it was a bad batch and the 40 volt pack that where all zero volt cells definitely didn't help but in general they where just total garbage. Cells testing too low to be useful mostly about 50% capacity for the cells that where not zero volt cells.
Then I ordered 50 lbs of the medical batteries from battery hookup. Those where pretty good I got 4 cubes with 42 cells each that where all 2900mah cells testing 100% or better. There where a fair amount of sanyo cells I think in red wrappers that didn't test so great but they seem ok. So I ordered more of the medical batteries the order I got today seems high to laptop batteries maybe more than half the order I am not really impressed by that. But since I want to keep the current low I think they should be ok.
Here is my two cents on tractors. If you can upgrade to a riding tractor the weight is a bonus and batteries don't really like heavy discharge so more capacity instead of swapping batteries will improve their longevity I believe. But I am far from an expert when it comes to batteries. But I can tell you weight on a tractor allows it to do more work without breaking traction with the ground. My loader tractors are much bigger 40hp for two of them I use a lot both have loaded tires on the rear to counter ballance the bucket.
Honestly I have never liked using a walk behind tractor they are just brutal to control. That was one of the reasons I bought the case ingersoll 448 in the first place I couldn't stand using a walk behind tiller in the garden.
Oh I noticed that some of the lifepo4 batteries you buy have a commutations connection to hook them in serries and other say very clearly you can't connect then in serries.
I watched a video online a week or two ago about hooking BMS in serries and I wasn't impressed. The person doing the video said see it works one BMS tripped out and the inverter went into a low voltage alarm the 48 volt system dropped to 24 volts. But that was a red flag to me. If the two batteries are in serries and one opens the output contactor I want it to drop the system voltage to zero. I don't want the bad battery to provide a current path for the good one somehow. So I came to the conclusion that I didn't feel comfortable building packs with multiple BMS in one system. It might be perfectly safe I don't know the design well enough to say but I decided one BMS to rule them all was the way I want to go. My other concern was that if I have multiple batteries in parallel and one drops out the others will see a current spike. I didn't want to size my connectors to handle the max system current if I knew each pack wasn't designed to handle the max system current.
 

MBF Dan

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May 14, 2021
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Awesome thread! What kind of connectors are you all using for this application?
I am thinking of using the Amass AS150 connectors I need to look into them more but they are gold plated and anti spark. I haven't ordered any yet as I am a long ways from collecting enough cells. My goal is to spend most of the winter on this project and have it for next spring. Too much other work for me to do all summer so I am just planing and testing a few cells as my schedule allows.
 

cak

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Mar 14, 2021
Messages
49
I use Anderson Power Pole Connectors usually these https://powerwerx.com/anderson-powerpole-colored-housings 45amp ones doubled up for 100amp(well90) and just purchased a few of the much larger 180 amp versions. Not the cheapest option but I like how they are genderless so I have a lot of flexibility about which device is the source vs load, ex I can charge and discharge from the same port etc. I also like how I can align the pairs in a different configuration for other voltages(my main working voltage is 24vdc). For balance leads I use these https://smile.amazon.com/gp/product/B01EVINO72/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 as they are fairly standard on balance chargers and the like(one note here is that you usually want independent wires for balancing not the wire you use for load/charging) I know a lot of the hobby folks use the xt60 or xt90 connectors which I have a couple of for adapters but have not been the happiest with using.
 

MBF Dan

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May 14, 2021
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Just a quick update. I have been buying the used medical cells from battery hookup as the price seemed good. The last few days I finally did the testing for self discharging cells and sorted out about 1350 good cells that can be used in my peoject. I didn't keep great records of the shrinkage but it was more than I was happy with. I got a couple of good orders the first couple I placed and the random nature of it wasn't so good with the rest of the orders I understand it comes with the type of cells I was ordering. But I tried the ring packs from battery clearing house. Much better cells and results so far from the few I have opened. I decided the higher price per cell will more than pay off with better matched batteries in the end and not having the level of shrinkage I see with the other cells. So I ordered enough of the ring packs to finish my EV tractor peoject.
I guess it is time to get my spot welder assembled and start welding up some batteries. At some time I will find enough time all at once to do that. Breaking apart cell packs and testing them has been nice because I can do it for a little while each night.
Anyway figured I would pass along my experience so far.
 

OffGridInTheCity

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Yes sir - I processed nearly 3000 RING cells in the last 12 months and they are the best I've ever done. 1300 of the 'blue' ones are in the cargo trailer battery - running since Feb with daily cycles and working perfectly. Haven't even had to do any balancing beyond the initial 4.0v balance to 20mv - here's what they look like this morning... running 30-40mv max diff 6 months later.
1630341656262.png


The green NCR18650As are also good - I've had these from other sources for a couple of years now and the RINGs tested as good as any I've ever seen. So... let me tell you how I 'really feel' about RING packs from Battery Clearing House :)
 

MBF Dan

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May 14, 2021
Messages
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Thanks for the good review. I am targeting 20kwh for my tractor project so have ordered 1800 of these cells to finish the project. I have already collected about 350 of the green Panasonic cells in these packs from the medical cells i was ordering. They where in some cubes that where downright scary to take appart as the first thing i tried taking apart but those cells tested perfect so it gave me confidence when I saw a supply of them at battery clearing house.
I just wish there was a way to know which end of the pack had the negative side of the battery before I open it so I could lower the chances of shorting them out but it seems like there are two designs and it is random luck which one you have with these packs. Atleast I haven't figured out how to tell them apart before I open them.
 

OffGridInTheCity

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Dec 15, 2018
Messages
1,706
Thanks for the good review. I am targeting 20kwh for my tractor project so have ordered 1800 of these cells to finish the project. I have already collected about 350 of the green Panasonic cells in these packs from the medical cells i was ordering. They where in some cubes that where downright scary to take appart as the first thing i tried taking apart but those cells tested perfect so it gave me confidence when I saw a supply of them at battery clearing house.
I just wish there was a way to know which end of the pack had the negative side of the battery before I open it so I could lower the chances of shorting them out but it seems like there are two designs and it is random luck which one you have with these packs. Atleast I haven't figured out how to tell them apart before I open them.
I crack them with a vice on (about) an 1" off the end with edge of jaw 'just below' the glue line and then use a screw driver to pry it the rest of the way. About 5% won't crack and for those I use a hack saw on the USB end? (the end with the circuit board) to saw just a groove accross the end just into the circuit board and then use screw driver twist to crack open.

1630342873135.png

1630342925654.png


With the vice cracking you have to use a pretty good force but not quite so much to start denting the cells inside - some crack easily and some take squeeze/let-off/squeeze/let-off/etc, and some if one end won't crack I turn it around to the other end and try. :)

I did observe very small dents on just a few of the NCR18650As near the bottom of the canister - e.g. <1mm. At first I thought maybe the vice squeeze did it - but then later on, I'm not sure. The NCR18650A(s) seem to have a 'very thin' canister compared to the Blues... and they may have gotten that during the RING pack build process.

The general consensus on dents is to toss them, but there's also a case to be made that <2mm lateral dents don't cause any harm as there's actually room (inside) for the roll to compress a little. Me - I use <1mm (small) dents and no problem so far. BUT I cannot recommend that to you and I believe the 'official' forum advice is to toss :)
 
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MBF Dan

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May 14, 2021
Messages
35
I will definitely try that vice trick. I have been taking a big pair of cutter pliers I guess is the political correct term for them these days. Almost got fired from one job for calling them the old name..
Anyway I cut in just a little right at the split, holding the pack in one hand as twist the pliers they usually pop but it isn't good if you get the pack with 2 wired and the positive at the wrong end you can easly short the cell. The vice looks far safer.
 
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