Assembled Hi-Power LiPo battery packs - any interest?

[Jaack]

OK so 2 lots of 22s4p boards and copper busbars would cost $484 AUD - or about $370 USD. Shipping will be on top of this, maybe about another $70-$100 because of the weight of copper.

These can be for either the 8.2 mm thick cells from FEP or the 9 mm thick cells, both of which are 50 mm wide.

I suggest you buy the cells first then measure their thickness - we can assess which boards to use if they are too far away form either of these two measurements.

Cheers,
Chris

i didnt consider the weight/cost of the copper by mail..ill source the copper here locally ... so ill need only the boards/nuts....ill also source the matching bolts here as well to save weight..charge?

[jonescg]

Sure - best to get them water jet-cut, but if you're patient you can drill the holes yourself. It's important to get the holes drilled as accurately as you can because a misaligned screw will push the nut off the back and will be impossible to recover. I can send it complete with screws and washers, just leave the copper out. That puts the cost at only about $134 AUD. The copper is by far the most expensive part.

[Jaack]

Sure - best to get them water jet-cut, but if you're patient you can drill the holes yourself. It's important to get the holes drilled as accurately as you can because a misaligned screw will push the nut off the back and will be impossible to recover. I can send it complete with screws and washers, just leave the copper out. That puts the cost at only about $134 AUD. The copper is by far the most expensive part.

ok that sounds good..i just may have sourced my batteries .. i need to think about weather or not i can trust buying them where im buying them from..if it pans out they are 9mm x50mm x135mm 5ah at 35c...after i get the boards and ready to start building would you help me with instructions on building the polycarb enclosure that you build with your batteries?...whats your opinion on compressing the batteries inside the enclosure(to prevent puffing) with 2 compression boards 1 on each side of the case compressed with a threaded rod connecting the 2 boards?

[jonescg]

Cool. the 50 mm wide bit is a little forgiving, but the slot spacing is critical. If the cells are 9.1 mm thick on the 9.0 mm slot spacing, you can almost get away with it.

The enclosure is easy enough to sort out. Polycarbonate is light, strong and clear, so you can see shit about to happen, if it does. Compression is essential, but threaded rod is possibly overkill. Being 22s4p, the pack would be almost 400 mm long.

Happy to advise where I can.

Cheers,
Chris

[Jaack]

Cool. the 50 mm wide bit is a little forgiving, but the slot spacing is critical. If the cells are 9.1 mm thick on the 9.0 mm slot spacing, you can almost get away with it.

The enclosure is easy enough to sort out. Polycarbonate is light, strong and clear, so you can see shit about to happen, if it does. Compression is essential, but threaded rod is possibly overkill. Being 22s4p, the pack would be almost 400 mm long.

Happy to advise where I can

Cheers,
Chris

..yeah your probably rite but over kill gives you that extra bit of security....i absolutely dont want to deal with puffing batteries....they are very expensive and a lot of effort to build.

[jonescg]

Hi all, Aussies in particular,

There looks to be a bit of interest in some of these 9050135 format 7000 mAh pouch cells. They are typically 9.2 mm thick and are good for 5 C bursts, 3C continuous. Usual LiPo rules apply - halve these figures for daily use.

9050135_7000mAh.jpg (112.33 KiB) Viewed 2913 times

The cycle life is good - looks to be 1000 cycles to 80% capacity based on my little bit of cycle life testing in a highly artificial environment but with good heat management and modest C rates they should be okay. 131 g per cell - so at 1C it's about 200 Wh/kg.

Now the price is about AU$20 a cell landed. GST has to be added to this by the way. Not cheap, but on a $/Wh basis these are actually a bit cheaper than the 30C/60C cells I normally use for high powered packs (AUD$800/kWh).

The MOQ is 1000 cells, so that's a huge investment. The more we order the merrier, so if you are interested let me know. I'm devising a new product for market and I'm confident they will do well. Not cheap of course - nothing I do is cheap

Cheers,
Chris

[jonescg]

I just put another 2s2p pack together for testing using these 7000 mAh cells. I'd tested them over a year ago, but thoguht I would set them up for some cycle testing. First job was to do a capacity test.

I pulled them out of the box where they'd been sitting for over a year and tested their voltage - 4.1 volts Great storage voltage for a hot climate like Perth

20180318_165026.jpg (248.95 KiB) Viewed 2863 times

Still, they are in good shape (no puffing). The only load I could devise was a length of steel wire, giving me about 11.3 amps over the course of a discharge. So 0.77 C isn't much, but it's close to what the capacity is normally rated at. Anyway, last time I did it, I used 1 C.

Capacity test.jpg (36.18 KiB) Viewed 2863 times

I've set it to cycle 100 times at 0.77 C charge and 0.77 C discharge. I will repeat the capacity test again at 100, then again at 200 cycles, up to 500 cycles. I should know how it's looking by that point. At these low rates, any tendency for degradation reactions to happen will be obvious.

Edit - after 12 cycles my mild steel wire load failed I'll set up a decent load wire this afternoon

[Arlo1]

Nice multimeter. I have like 4 of those.

[jonescg]

Finished a quick 14s3p battery for an ES member. I'll leave the balancing / monitoring up to them, but the 8mm2 cables will have XT90s put on them.

20180324_170137.jpg (207.36 KiB) Viewed 2750 times

[jonescg]

My shipment of 7000 mAh pouch cells is due to arrive in a few weeks time.

Unfortunately all of 1100 of them are spoken for, but if you want more let me know - minimum order is 1000 unfortunately, and at $20 AUD landed they aren't cheap (but no worse per Wh than the other FEP cells).

Stand by for some very cool packs

[jonescg]

I have almost finished this battery pack for a cool supermoto build.
I'm using a prototype BMS from EV-Power - does balancing as well as reports pack cell voltages and temperatures. Very cool.

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PS That 200 A fuse is for show. It will need to be at least 600 A...

[jonescg]

Looks like there is some interest in more of these high power LiPo cells. So it's time for another order!
MOQ is 550 cells, but I can get a 5% discount if I order 1000. That makes the landed price $15.45 + GST
Australian orders only, sorry.

I am happy to build a battery and ship it to anyone in the world, but it gets expensive real quick - about $2000 per cubic metre. Minimum shipment is 1 cubic metre...

[jonescg]

I've been working on a 96s2p battery pack for some uni students. The battery will eventually be used for dyno testing their powertrain but it's just as likely to end up in the car. 3.5 kWh, 355 volts and 10 Ah. It has a vestibule with contactors, fuses and precharge hardware.

Three of the four modules:

EV-Power BMS to manage the pack:

[Rodney64]

Nice project Chris.

[Mywpn]

I’m after a 96v nom. lipo pack capable of delivering up to 1000 battery amps eventually. 109v fully charged. I have just had a very bad experience with 18650 cells. Was my own fault for overpowering this pack with at least 30v of voltage. It was Samsung 25r @23ah. This pack was very under done for where I’m looking to be. In all reality I never really travel over 20km per trip and have chargers at a couple of regular places. It also needs to fit into a eeb enduro frame. I’d like to hide the controller in there but it’s not the end of the world
Thanks in advance. It would need to be shipped to aus.
Regards Heath.

[Rube]

Hi Chris, did you fill your recent order MoQ and complete the order? Let me know if you didn't, thanks

[jonescg]

Heath - Sounds like 26s4p might work well for you then (96 V nominal, 20 Ah). The extra 3 Ah might not be needed considering the sag your Samsungs would have experienced.

You can have any shape as long as its a rectangle A 26s4p pack inside a polycarb enclosure would measure 446 mm long, 106 mm wide and 168 mm tall (if it's to include a BMS) otherwise it can be about 8 mm shorter.

Ryan - I ordered 550 cells but I have about 80 not spoken for. They should be arriving in the next 3 weeks.

[Volts]

Am I to surmise that storing lipos at anything below 4.2 is fine? how goes the cycle tests so far? I've also read and tested (not at any great lengths yet) that if you compress lipos they work better as the partials are forced closer to each other

[jonescg]

Am I to surmise that storing lipos at anything below 4.2 is fine? how goes the cycle tests so far? I've also read and tested (not at any great lengths yet) that if you compress lipos they work better as the partials are forced closer to each other

Storing any Li-ion cell at high states of charge will shorten its useful cycle life. It will be made worse by high temperatures.
I tested 600 cycles to 80% of original capacity on the high discharge cells but I had to stop the high energy cell testing as I moved house. Should set that up again sometime soon...

Compression is good - but it doesn't need to be massive. Enough to keep it snug is fine for the most part. The cell's internal resistance will increase if the cell is able to puff, but you should also be using them in such a way that puffing doesn't happen.

[Mywpn]

Heath - Sounds like 26s4p might work well for you then (96 V nominal, 20 Ah). The extra 3 Ah might not be needed considering the sag your Samsungs would have experienced.

You can have any shape as long as its a rectangle A 26s4p pack inside a polycarb enclosure would measure 446 mm long, 106 mm wide and 168 mm tall (if it's to include a BMS) otherwise it can be about 8 mm shorter.

Ryan - I ordered 550 cells but I have about 80 not spoken for. They should be arriving in the next 3 weeks.

The lack of ah would be no issue. It’s only the current draw I’m worried. It’s a lot of amps to get from a pack.

[jonescg]

The 96s2p pack I built for the university team is finally complete.
I have a tiny bit more testing to do making sure it charges up and balances properly, but all told it's a complete unit.

You get this lovely display when you supply the BMS with power:

Power up.jpg (197.28 KiB) Viewed 1601 times

And if the monitor is plugged in, it cycles through each stack of 12 cells with temperature and voltages.

BMS info cycling.jpg (193.93 KiB) Viewed 1601 times

The vestibule contains a contactor on both the positive and negative ends of the pack, a fuse in the middle of the pack (first thing to be removed when servicing the pack) and a 10 amp HV fuse for protecting the charge circuit. It's got a precharge Minitactor and a 50 W, 200 Ohm resistor for precharging up to 700 uF and 400 V worth of capacitance o the inverter.

It's glued in place with polyurethane adhesive so it's not serviceable as such. But I wouldn't expect it to need servicing under normal use.
Will post some more pictures in better light soon.

[jonescg]

Slightly more glam photos:

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[jonescg]

Okay, time to share a really cool development.

12s10p_finished.jpg (172.95 KiB) Viewed 1454 times

I've been working on these liquid cooled, 3.2 kWh modules for a Honda Prelude I'm converting for a friend. The car will have 8 of them in series for a 355 V nominal system voltage, for a total of 25 kWh.

Modules.jpg (167.26 KiB) Viewed 1454 times

Each module is ~340 mm x 200 mm and 180 mm tall, and weighs in at just over 18.5 kg, so that's a pack level energy density of 175 Wh/kg. It uses the 7000 mAh pouch cells I tested earlier which are a genuine 208 Wh/kg at 1C. The module is a 12s10p arrangement, so ~45 volts nominal.

Most importantly the whole baseplate is liquid cooled, and a thermally conductive epoxy bonds the cells to the base for a respectable thermal path. The 3/8" hose will form a manifold for all 8 modules and be circulated through a heat exchanger. The aircon refrigerant can be pushed through an exchanger as well for Perth's signature hot days.

12s10p_nearly done.jpg (188.63 KiB) Viewed 1454 times

I expect to see 4C peaks from this pack (100 kW) but most of it's life will be spent under 1C.

I hope to develop them a little further, but I expect them to retail for about $3800 each. Best of all, it can be used with any pouch cell making it possible to build a racer using the high discharge cells with rapid charging too. The thermal management means they should be still functional after 7 or 10 years. I'll add more photos as they appear.

Now, I have an AEVA national conference to get to in Brisbane - see you there!

[Hillhater]

I have been meaning to ask you chris,
...why have you chosen these 1C rated cells rather than a higher (5-10C) cell ?
Is it cost ?, cycle life ?, quality ?, size ? ???

[jonescg]

Technically they are a 2C continuous, 5C peak, but I wouldn't push them that far (usual LiPo rules). At 2C they are more like 190 Wh/kg, which is still entirely useful.

The manufacturer of the cells does any chemistry you like, so I might see if they can do NMC in the same size format. There will be a slight hit on the specific energy, but the power should improve a bit.

I like the 9050135 format as it means you can build up in capacity more easily. 20 Ah cells are too big for many spaces but 7 Ah seems like a good compromise.