Coming Soon A123 Hymotion Modules for ES and ALL

[steveo]

i sold the same packs a while back..

great cells...

not the greatest design for high current discharge ..

i remember talking to one of the hymotion battery pack designers.. he told me that they where designed for 100amps current continous due to tab design limitations! great cells otherwise!

-steveo

 

[wb9k]

i sold the same packs a while back..

great cells...

not the greatest design for high current discharge ..

i remember talking to one of the hymotion battery pack designers.. he told me that they where designed for 100amps current continous due to tab design limitations! great cells otherwise!

-steveo

That sounds about right actually. The Hymotion pack has a DC/DC converter between the battery stack and the pack output. Pack voltage has to be stepped up a bit to work in the car. This also limits the pack's output current, so there was no reason to build modules that could withstand the same abuse the cells themselves can take. The Sybesma's test includes 10s pulses at 125 Amps, so they can definitely do more than 100 Amps for brief periods of time at least. I suppose you could beef up the output capability by filling in that notch fuse on the negative terminals with some metal, but it's not something I would recommend.

 

[energyi]

I'm using some recycled first gen. Hymotion A123 bricks on my bike. I cut one cell out of the middle of each 11p group, making two 5p groups. I have a 10Ah 16s pack about the size of shoebox.

Fechter: revisiting this old post because trying to figure out what to do with L5 Hymotion system. Your approach seems insightful. Two questions, what BMS did or do you use for 16s scenario. And, do you just leave the one cell in place, cut out of the electrical string? Thanks again for your knowledge base.

energyi

 

[fechter]

Fechter: revisiting this old post because trying to figure out what to do with L5 Hymotion system. Your approach seems insightful. Two questions, what BMS did or do you use for 16s scenario. And, do you just leave the one cell in place, cut out of the electrical string? Thanks again for your knowledge base.

energyi

The BMS I used was DIY home made. It is still working. There are 16s LiFePO4 units out there now that are fairly inexpensive (and a lot less work to make).

I removed the cell in the middle and used the empty space to put the interconnecting wires. I used a Dremel tool to cut through the strips.

 

[energyi]

Amazing, you make your own BMS. Thanks for the additional pictures. I had mapped out the cut scenario for qty-2 4s11p to 16s5p scenario leaving 8 left over cells, 56 left over cells if all 14 4s11p still have life. Your photos help confirm the cut scenario.

I will probably get some ping BMS but check another vendor (bestechpower.com) that will enable monitoring. I know ping is best.

 

[fechter]

I've had good results with Bestech Power also but only tried Li-ion versions.

Search eBay for "LiFePO4 BMS" and you will see some very inexpensive ones.

Here's one: http://www.ebay.com/itm/48V-30A-LiFePo4-Battery-BMS-LFP-PCM-SMT-System-16S-16x-3-2V-eBike-Battery-16x-3V-/112488768436?hash=item1a30da63b4:g:6ewAAOSwaGFZcLww

Looks much like the Ping versions. These could be modified for higher current by replacing the discharge FETs and changing the shunt resistance.

 

[energyi]

Thanks again for your support Fletcher. I ordered a Ping, but am going to need more so your inexpensive suggestion is well taken. Seems to me that your homemade BMS is actually a balancing board, correct me if I'm wrong. That is probably what is needed in one of my scenarios because I have a motor controller that will limit output on minimum voltage, and my battery charger has a high-end voltage limit so that isn't going to be exceeded. I think balance is all that is needed in that scenario.

I re-read this whole Hymotion thread from 2013, some really interesting discussions, even some intriguing off topic stuff.

energyi

 

[energyi]

16s11p using the salvaged electrical straps between sub-assemblies and some zip-ties. Copper wire moved from the center lug. Just have to wait on BMS shipment.



energyi

 

[energyi]

Werks! As shown with ping gear.