Throw an inverter on this thing and you have group ride hosting vehicle
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We got cables. I think those are 10AWG.
EDIT: checked and they were 6mm^2, so 10AWG, but considering the DC load is at max 160W, it means a max current of 4 amps at 40V, so I don’t think were cable limited for testing purposes.
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oh my lord, how even are you even going to be able to make it ride comfortably or be comfortable yourself ?
The module is going in the battery trailer, it isn’t gonna be on the board itself.
MTB setup with pneumatics isn’t too bad on even a slightly rough ground and I’m also upsizing the wheels from 8" to 10" just to improve the ride a bit. Just stretch every once in a while just to make sure you keep the blood flowing in your feet and legs, otherwise I get cramps with my toes.
EDIT: also charging atm.
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For all your ring terminal needs, I’ve always found using “One-Hole Lug Compression Connector, Straight Barrel” to be a bit nicer than standard copper marine grade lugs. The yellow 10-16 ton hydraulic crimpers for ~$30 are also great for the crimping part. However, you can always drill a tiny hole in the barrel of a lug, heat w/a blow torch/butane torch, and feed solder in until it peeks thru the entrance of the lug/completely fills in the drilled hole.
A lot of argument to be had on why soldering lugs on 8 awg or lower is bad… But I’ve seen enough real world experience of crimped & soldered and either method is fine if you’re not going to space lol.
EB-Flex by Electronbeam is also amazing wire for 8 awg or lower heavy duty needs. Can tie my 2/0 in pretzels with ease.
Sweet battery.
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Doing a capacity test now.
Running on a Maynuo M9711, which is a cheap chinese clone of a HP electronic load.
I have an arduino in the back that hooks up to the RS232-port of the load and then uses modbus-protocol to control the load settings and measure what the voltage is on the input, which is the battery in this case.
It then echoes back the voltage and a timestamp to a serial terminal on a PC.
Current test cycle is as follows:
- Constant current load @ 3.2A
- Load ON for 15 minutes
- Load OFF for 5 minutes
- Repeat until battery hits 41.4V (more on that later)
The three values seen on the serial terminal are voltages sampled at different points. The first one is the voltage at the end of the 15 minute ON period, but before the load is turned off (under-load voltage), next voltage is the voltage about a second after the load has turned OFF (immediate release voltage) and the last one is the voltage at the end of the 5 minute rest period (resting voltage).
Okay, the DC load is a max 160W load, so it doesn’t really stress the battery so in this case all the voltage are going to be pretty near each other, but for example in the case of my 10S6P pack there is a bit of a difference between these voltages, as is shown in the graph below. This helps to get a little bit better picture of what the SoC is based on the resting voltage.
Now here’s some data I dug up on the battery pack, because I needed to figure out what the discharge cut-off voltage was before starting the capacity test.
The 12 cells are manufactured by Samsung SDI and are meant for electric vehicle use. They also upgrade their design and chemistry over time, but keep the same cells dimensions so car manufacturers don’t need to completely redesign their battery modules, but can just upgrade the cells to a higher capacity one.
This also explains the little confusion I had as I had looked at the 4,15kWh and 5,3kWh i3-modules, as they had the same dimensions based on their product pages. I even contacted the shop about this and they confirmed that the dimensions were correct, but now knowing this upgrade thing happening to the cells on the manufacturer side it makes sense, especially as I found this little sheet that reported the different cells based on their manufacturing date. This would also mean that the 4,15kWh i3-module uses the 94Ah cells, which then lowers the energy capacity to the 4kWh mark.
But boy oh boy, if they are gonna release those 150Ah and 180Ah cells sometime in the future 
I was still missing the datasheet for the cells, which specify the cut-off for both charging and discharging for the cells and no matter how hard I looked I couldn’t find the datasheet for the 120Ah cells in the module I have, but I did find the datasheet for the 94Ah cells, so I guess I’m gonna go with that info.
So it looks like operating voltage is specified at 2.7-4.15V but looks like effective SoC is 0% at ~3.4V, so I then decided to stop at 3.45V at the cells, so this then lead to the 41.4V termination voltage for the capacity test.
EDIT: it’s gonna take like 2 days to get the full discharge done on the battery
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1st world Esk8 problems. 
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Trailer hitch, should attach with rod end, to the back of truck. Middle.
Level to ground.
Possibly surge brake mech, on hitch, and a foot brake made from a caliper cut or split in two. Shoves a puck into tarmac.
ahem
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this project is like got my mind blow so hard…its also very inspirational 
I thought my 18s12p tesla pack was huge…loooool, its like a drop in the bucket compared to this 
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What the hell have i just walked into
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Okay, so the first capacity test is finished and I’ll post the discharge curve later today. I did discover that the 3.45V cell voltage that I used for the cut-off voltage (41,4V for 12S pack) is actually way above the practical cut-off voltage, but I was confused by two different voltage values found in the datasheet.
First of all the general summary information on the cell says 2,7V-4,15V
But then there’s this OCV charge and discharge chart, but I don’t understand for what reason they only discharge down to ~3,40V… a quick google search tells that OCV stand for open-circuit voltage (no-load/resting voltage), so does this graph actually tell what the resting voltage is at different stages of SoC.
Looking closer at the testing method it looks like the discharge current is 1/3C, which for a 94Ah cell (datasheet is for the 94Ah cell) is ~31A, so I wouldn’t actually be that surprised if the voltage did rise quite a lot at the low end, but I’m a bit annoyed that they don’t specifically tell what their cut-off discharge voltage was.
Then there is the an actual capacity test chart also in which they do discharge down to 2.8V, which is quite a bit lower than the 3.45V than what I did for this first run and got quite a bit lower capacity rating therefore.
So I’ll graph the first test and post the results and start charging the pack back up for a second test.
EDIT: here’s some videos for the i3-pack for the time
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So, first capacity test results: 103Ah, 4,6kWh. Test current 3,2Amps, 15min/5min (ON/OFF), stop at 41,4V pack (3,45V cell)
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Was that you involved in the three man looooong distance ride with trailers awhile back?
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Could it be discharged down to 2.7 rest for 24h then check the resting voltage with every thing disconnected voltages can increas and with the heavy drop off at 3.4v it’s possible the cells could bonce back that high
Car packs probably dont cycle 100% like we do in our boards to increase the life span of the battery.
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Agreed.
The depth-of-discharge, charge voltage, and temperature ranges are very limited for EV packs to help increase the cycle life. People would definitely get pretty pissed at replacing a $15,000 pack every year.
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