Assembled Hi-Power LiPo battery packs - any interest?

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by Hyena » Tue Feb 17, 2015 8:05 pm

haha well played. I've thought the same when people in the US want me to build them whole raptors. With 2 people keen it's better to actually fly there and assemble on location!

You've told them lipo doesn't like cold weather right ? Seems like it'd be much better off keeping it here in Au :wink:
I guess I'll reluctantly put my name down for a test flight :mrgreen:
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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sun Mar 29, 2015 12:12 am

So I finally found the time and inclination to test these FEP8048135 cells.

They have been sitting here at my desk for a good 2 months or so. I was sent 5 cells, although I only wanted 4. Just as well they sent 5, as one of them was staring to puff and read 0.7 volts on the multimeter. Gotta love Chinese CQ :lol:

So I soldered a 2s2p pack together as before, using the same copper termination system I've always used. I taped them up with some clear cellotape and put the coil of galvanised wire in a bucket of water. The average discharge current was 36.77 amps for the duration of the run, which is a little over 3.5 C. I stopped the run at ~3.4 V per cell, which was after about 17 minutes.
FEP8048135 cell testing.jpg
FEP8048135 cell testing.jpg (95.92 KiB) Viewed 3103 times
After the run the cells were resting at 3.45 V each.
FEP8048135 at 36 amps.jpg
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So an impressive 10.7 amp hours from the 2p pack, and an average cell voltage of 3.77 V. This translates to 80 Wh in total, which for a 108 gram cell affords 186 Wh/kg!

Now, the cells were too hot for me to hold the back of my fingers against for any longer than about 5 seconds, which means they got pretty darn hot. Personally I'd call these cells a 4 C continuous rating, with perhaps 8 C bursts for no longer than 5 seconds. Given their temperature I won't be trying them at any higher currents.

For a car conversion, or motorcycle with an imposed power limit, they would offer impressive range for their size and weight. Some kind of cell cooling would be wise though.

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sun Mar 29, 2015 8:02 pm

Should add here - Alisa from First Energy Power said that they were rated for just 300 cycles. Which is pretty piss-weak for any modern LiPo cell. I mean, at 1 C you should be able to get at least 500 cycles, and ideally over 1000.

The search continues....

Edit - I asked her to confirm that 300 cycles was correct, and she replied that after discussing with her engineer, the cycle life was more like 800-1000 cycles, 1C discharge and 0.5 C charge.

Hmmm. I suspect she's saying stuff I want to hear, rather than stuff that's true. I wish I could set up a test rig for automating this stuff. Run 100 cycles and see how it looks, kind of thing.

Edit #2 - I was quoted US$12.50 each, with a minimum order quantity of 500 pieces. Shipping is in addition to this; about $350 usually. So for an Australian buyer you're looking at AU$17.50 each, plus GST, plus 4% customs fees. Or about $10,000 for a 500 cell order. AU$20.82 per cell, or $1.08/Wh.

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by RobertEMellish » Sat May 23, 2015 1:39 pm

Hi Chris,
I was wondering, do you still have PCB's made to order? I've been thinking about a 48s4p configuration of 40C cells on a CBR600RR frame with a modified 72V 365aH forklift motor and a Soliton Jr as a controller. I'm going for raw power. Desired range would be 10Km as the bike is mainly built as a "show and ride" project for the motorcycle parts store i'm working at. Any additional input from someone who knows his way around high performance electric motorcycles would be appreciated! The PCB's will need to be shipped to Cyprus.
Best Regards,
Robert E. Mellish

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Tue Jul 14, 2015 8:29 pm

Hi Robert,
Sorry about the late reply, I rarely check in on this thread any more. I have a handful of 5p boards, but if you would like a stack of 4p boards I can easily get another bunch made up and sent to your address. What layout would you be going for with this pack? One large rectangular pack?
Cheers
Chris

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by Arlo1 » Tue Sep 08, 2015 7:58 pm

I like this design I think its great.
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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sat Oct 31, 2015 11:38 pm

Well the innovations keep ticking over here at Voltron Motorcycles :D

I have been trying to find a way of using high energy density LiPo in very large capacity packs. The biggest pack I can conveniently solder is 5p, or 25 Ah. Depending on the cells you use, this could mean discharge currents as high as 700 amps! Nonetheless, lower C-rate cells in large formats are ideal for cars and low voltage motorcycles, but soldering 12 cells together in one hit is really hard - and the odds of a lacklustre cell bringing down the group are higher (there's more of them).

You might recall I had devised a termination system for EIG cells using M3 screws and water jet-cut busbars. Well I am considering this for the LiPo packs. It requires being able to hole-punch the tabs of the cells as accurately as possible, which might be a tough ask. But with the right jig, I reckon you can make a go of it.

I took one of my 7s2p boards for the 40C cells from Herewin. This has the BMS trace from the inner busbar pad extended out for a neater assembly. I drilled some 3.2 mm holes and soldered a couple of brass nuts to the underside. Then I took a LiPo cell which hadn't had it's cell tabs trimmed and punched some ~4 mm holes (it's imperial, so who TF knows) to account for any misalignment and screwed a bit of 2 mm busbar down onto the PCB.
screw terminated LiPo 001.jpg
You would get these busbars jet-cut to suit and tinned.
screw terminated LiPo 001.jpg (96.71 KiB) Viewed 2660 times
screw terminated LiPo 002.jpg
10 mm screws clear the cell below. Thankfully :D
screw terminated LiPo 002.jpg (86.58 KiB) Viewed 2660 times
I think it's a winner! I personally wouldn't do this for 2p or 3p boards because the soldered busbars give a much better connection. But for 4p and bigger, or situations where you're not demanding too much from the cells because the capacity is already 40 Ah or so, it's a pretty neat solution. It also gives you a decent screw terminal to mount balance wires to, if you want really high balance currents or just find it more convenient. Otherwise the solder pads are still accessible.

So I will be experimenting with a few cell formats. At least if you don't want to screw terminate, you can still solder them as before. These cells are 9 mm thick, so there's plenty of real estate. If the cells were 7 mm thick, it's a bit tighter, but provided they were all in parallel I can't see an issue with potential shorts.

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sun Apr 17, 2016 2:28 am

Hi everyone,

I decided to finally get around to doing a discharge test on these FEP8042125 cells. These cells claim to be 6.1 Ah in capacity, and are a 1C continuous (3C burst) cell. I have my doubts :)
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My usual test rig was set up - a resistive load, a current meter (digital ammeter this time) and a CellLog8 because my multimeter was being used as an ammeter. It worked out pretty well - I stopped the discharge when one of the cells hit 3.00 V.
20160417_131237.jpg
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The average load for the duration of the discharge was 3.24 amps. Over the course of 97 minutes, that equates to 5.24 Ah. Far cry from the 6.1 Ah I was quoted. So using my newly calculated capacity of 5.24 Ah, this was a 0.62 C discharge. However, based on the alleged capacity of 6.1 Ah, it was only 0.53 C. Call it 0.55 eh?
FEP8043125 capacity test.jpg
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So, depending on how you calculate it, these cells offer between 18.5 and 19.2 Wh per cell, or a general 0.5C energy density of 180-190 Wh/kg. Nothing flash!

Try again I think... :(

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sun Apr 17, 2016 6:32 am

I repeated the test at about 1C (give or take) and rn the cells down to 2.8 V each. This squeezed about 5.4 Ah from it.
FEP8043125 1C test.jpg
FEP8043125 1C test.jpg (27.46 KiB) Viewed 2448 times
Still nothing flash. I think their first 10C/20C cells I tried were the best.

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sat Apr 23, 2016 5:58 am

I'm going to repeat a capacity test of the first cells I tested some time back. These are the FEP9043125 cells which were a pretty solid 8 C continuous cell with 177 Wh/kg. Perfect for a car project. Or a race bike?

I'm also using it as a chance to test the screw termination system. All this was done by hand, so its rougher than a Stanthorpe red. But went together surprisingly easy. Will report back soon.
20160423_184108.jpg
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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sat Apr 23, 2016 8:46 am

I'm still impressed with these cells, although I suspect my current measuring multimeter was a bit more reliable than the clamp.
FEP9043125 1.5C.jpg
FEP9043125 1.5C.jpg (21.64 KiB) Viewed 2414 times
So 5.08 Ah from a cell at 3.78 V (average) is about 19 Wh from a 108 g cell. Or 176 Wh/kg. Interesting that this figure hardly changed even when doing 8 C or even 13 C discharges.

My next two problems are 1) will it maintain these numbers after 300 cycles? 900 cycles?

And problem 2) can I get the termination system made for large batteries? I reckon this should be fairly easy provided you get them water jet cut and tinned. Gotta be careful assembling them though!

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by Ratking » Mon Apr 25, 2016 6:42 am

Jones, thank you for updating us on the progress, I always rear the testing you do, because it helps a lot of us that want to use rc-lipo.

What is the price per cell of the 8c cells you tested?

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Mon Apr 25, 2016 9:16 am

No worries. I wish I could cycle test them to 600+ cycles, but I still need to learn how to code first :lol:

From memory, I paid about $12.50 US per cell before shipping. It's probably about the same now - cells got cheaper, exchange rate got worse.

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by galderdi » Tue Apr 26, 2016 10:09 pm

Jones,

Very impressive work to date. I have had a look back through this thread but now I'm a little confused because I don't know what information is still current or what has been superceded.

I need a replacement battery pack. Mine is a bit bigger than a bike. Its for an motokhana car. See here : https://endless-sphere.com/forums/viewt ... 34&t=76189

Ideally I would like about 5-7 kwh at around 150v nominal. But they need to handle 20 second bursts of 250-300 amps.
What do you suggest?
What would be the costs of such a pack?
Where can I get a charger for it (I am happy to charge it in sub sets. I charge my current pack 6 cells at a time)?
I currently have cooling around my Holden Volt packs. Do you think cooling would be necessary on the replacement packs?

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Wed Apr 27, 2016 12:48 am

Yeah, lots of improvements and refinements over the years. My main principle of copper busbars on top of cell tabs is consistent, but I'm pretty excited about the screw terminal idea, especially for larger batteries.

150 volts nominal and say, 6 kWh means 40 Ah. I'm working on a 50 Ah battery cell using the screw terminals (1s10p). This would be with the 8C cells, so 300 amps burst easily achievable.

Cooling wouldn't be necessary with these cells, but as always you'd have to put them inside a sturdy enclosure made of polycarbonate or something similar. Can't say how much it would cost, as the water jet cut copper won't be cheap, but at least if a cell goes bad it's not impossible to repair the pack.

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Thu Apr 28, 2016 7:09 am

So I decided to bike the bullet (well, having just come back from the dentist, I might not bite anything :( ) and get some of these new boards made up.

I have made orders the following boards:

9043125_7s3p - these are the 10C cells I tested a few posts ago.
9043125_1s10p - same again, except 10p will make a good alternative to a common CALB cell application.

9048135_7s2p - This is the configuration I use on the 6 kWh race bike battery pack.
9048135_7s3p - This is the configuration used on the 9 kWh battery.
9048135_1s10p - Did somebody ask for 1000 amps from a single cell? :twisted:
PCB options.jpg
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All of these will come with screw holes, so if you wanted to use screws and hole-punched cell tabs instead of solder, the option is there ready to go. Of course they can still be used with solder as always.

Yet to get the busbars made though...

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Fri May 20, 2016 11:58 pm

Sigh. frocking sigh.
20160521_121534.jpg
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For some reason the drill layer didn't come through. What on earth can you use these for, apart from maybe holding short table legs up? :roll:

Another long wait ahead...

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Wed Jun 08, 2016 7:13 am

YAY! They got it right :)
screw terminal PCBs sml.jpg
screw terminal PCBs sml.jpg (95.31 KiB) Viewed 2171 times
Interestingly the holes have their own Vias separate to the copper pad below. Not all though - one side has a gap where solder can't bridge, but the other side is uniform. Weird. Not that it matters in this case, but if you were soldering balance wires on you'd have to make sure they were bridged properly.

Now the next step is to get the busbars water jet cut. I can hand-drill a few trial bars, but it's the kind of thing you really want done accurately on a CNC.

Then finally I need to make sure the tabs of the cells can get hole-punched at exactly the right spot. Another sub-project...

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sun Jun 12, 2016 2:45 am

So far so good. The trick is in getting the hole in the tab punched neatly and accurately. You'd set it up in the jig as if you were about to use the soldering method, but screw them down carefully instead.
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Like I said, this method is a time consuming method which is better for high capacity packs, like 5p to 10p. Any smaller than 5p I'd just solder them. After all, solder gives a better contact and is far more compact - this method would make for a final package that's at least 7 mm taller.

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by Rodney64 » Sun Jun 12, 2016 3:19 am

New design Chris. Looks good

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sun Jun 12, 2016 3:43 am

Rodney64 wrote:New design Chris. Looks good
Cheers mate! I think despite the time consuming assembly, it will be popular because you can repair the battery if you get a dud cell in the mix. Again, it's a big effort, but you can theoretically do it with no damage to the battery.

Just a shame the screw heads add so much height - otherwise I could make a Voltron pack with these kits and repair cells trackside if I had to. Fortunately my batteries don't need trackside repairs :D ...yet :?

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by Tats » Wed Jun 15, 2016 4:20 am

Very neat. I was toying with ideas about using veroboard but this looks much much better. Nice one.

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Thu Jun 16, 2016 4:46 am

Cheers mate.
Nice work on the spotwelder too ;) Looks like a few folks have had some raging success with it. I did look at fitting 18650s in the race bike but the pouch cells just work better. I think I could fit a maximum of 12 kWh in there using cylindrical cells, but pouch cells would fit almost the same and offer a bit more discharge.

I should be able to get close to 200 Wh/kg in a 9048135 cell with 10C continuous and have it fit within the existing size limits. The screw terminals won't fit, but I'd be soldering a pack of that size anyway.

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sat Jun 25, 2016 1:10 am

jonescg wrote:I'm still impressed with these cells, although I suspect my current measuring multimeter was a bit more reliable than the clamp.
The attachment FEP9043125 1.5C.jpg is no longer available
So 5.08 Ah from a cell at 3.78 V (average) is about 19 Wh from a 108 g cell. Or 176 Wh/kg. Interesting that this figure hardly changed even when doing 8 C or even 13 C discharges.

My next two problems are 1) will it maintain these numbers after 300 cycles? 900 cycles?...

Well here's my answer after 75 cycles at 1.5 C:
FEP9043125 after 75 cycles.jpg
FEP9043125 after 75 cycles.jpg (25.24 KiB) Viewed 1940 times
Red data points are the result of a balance charge and ~7.4 amp load.
Slight decrease in capacity, but they look pretty good so far. Will see how they look after 100, then 200.

This is after a constant recharge current of 5 amps, all the way up to 4.2 V per cell, then a discharge at about 6 amps (1.4 C).

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Re: Assembled Hi-Power LiPo battery packs - any interest?

Post by jonescg » Sat Jun 25, 2016 7:56 am

I've made some progress on the screw terminal batteries. This battery is destined to power another rather cool bike :)
hole punch tabs.jpg
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Stack the boards.jpg
Stack the boards.jpg (69.46 KiB) Viewed 1920 times
align the holes.jpg
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Screw down the busbars.jpg
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Almost done.jpg
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The pack comes together really quickly. The trick will be making sure the holes get punched at exactly the same spot on each cell. A tray made of Delrin (Acetal) with adjustable sides will work to hold the cell in exactly the right spot while a pair of hole punches can be used to make the 5 mm holes at the right spacing. For little prototype jobs the shitty RS components hole punch will work but you really need something a bit less unwieldy.

Total height at the moment is about 150 mm, but with a cover and BMS wires it will be closer to 160 mm, especially if the modules are to sit on top.

If anyone's keen on a pack made like this let me know!

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