Discharge Curve: Headway 38120S (screw terminal) 10ah cell

[Doctorbass]

dr bass, these are much better, remember flip was reading 2.47V at 35A. this is almost .6V higher, more important, flips cells were within .3V of shutting down the BMS with a LVC around 2.1V.

spectacular results. how hot did it get?

It got up to 43.1 degrees Celsius which is 109.58 degrees Fahrenheit. I would like to see what she can do at 10C. I wonder how hot it will get since 3.5C it got to 110 degrees.

Please guys pay attentions to an important detail! the temp indicated is the temp exactly toke at the end of the discharge. BUT like i often observed with cell dishcharge is that the heat transfer from the center of the cell and the external envelope is not fast.. So usually the cell temperature will continue to increase!.. that cell if i remember correctly increased up to 51 degree C.

From now i did not cooled the cell for the discharge but i may consider doing it for the 10C test.

That cell temp at 35A revelate that the main limit of 50A continuous or 100A peak IS THE TEMP OF THE CELL.

Now the 0.1C discharge test is running.. and should take like 11hour max so tonight i shold be able to post that result.

Also, i calibrated the CBA temperature sensor with the ambiant but i suspect that the magnet and shrink tube attached to it to stick on the cell is not a good thermal contact. I'll test with another temp meter.

I want this CBA perfect for my tests!!

Doc

Doc

 

[ZapPat]

Please guys pay attentions to an important detail! the temp indicated is the temp exactly toke at the end of the discharge. BUT like i often observed with cell dishcharge is that the heat transfer from the center of the cell and the external envelope is not fast.. So usually the cell temperature will continue to increase!.. that cell if i remember correctly increased up to 51 degree C.

From now i did not cooled the cell for the discharge but i may consider doing it for the 10C test.

That cell temp at 35A revelate that the main limit of 50A continuous or 100A peak IS THE TEMP OF THE CELL.

I guess that's it, Doc - it's the cell temperature rise that is the real limit of these cell's current capabilities! At 50A continous I would imagine that the cell might get up to over 65oC during discharge, something that I would never do with cells I want to keep (they'll degrade much faster over 60oC). I'm looking forward to the 5C test for sure!

Also, i calibrated the CBA temperature sensor with the ambiant but i suspect that the magnet and shrink tube attached to it to stick on the cell is not a good thermal contact. I'll test with another temp meter.
Doc

I've thought about this a few times, and it might help also if you insulate the backside of the temperature sensor, so it doesn't loose too much heat into the room and give a lower reading.

One thing about these tests is that single cells will cool much better than a whole pack during use, specially for the cells inside the pack. One more test to do someday...

 

[Doctorbass]

One thing about these tests is that single cells will cool much better than a whole pack during use, specially for the cells inside the pack. One more test to do someday...

that'a what i observed when measuring makita and dewalt cell in their pack.. this is difficult to keep every cells in the pack away from having a temp rise when te cell next to the one you test can be affected by it.. I mean as the individual discharge test porgress from one cell to another, the entire pack temp will rise , making some capacity and IR measurement influenced and making impossible to get a great absolute measurement for every cells!

Doc

 

[dnmun]

i saw jozzer has a discharge graph for the new 14Ah lifebatt, don says it will be available next year Q2, expect $70-76/cell myself, but it could be cheaper. too bad they don't exactly specify the current so we don't have to assume 2C=28A. looks like it is .15V stronger at 35A.

it will be good to understand why it has the knee at the end for the low discharge:

http://www.endless-sphere.com/forums/download/file.php?id=15974

 

[Doctorbass]

it will be good to understand why it has the knee at the end for the low discharge:

http://www.endless-sphere.com/forums/download/file.php?id=15974

Ah haaa.. that'S one of the "beautifull" features of the CBA at 35A.. it does that each time i do 35A.. I need to specify that set the 35A an d that the software accept it in the parameters, i NEED to set the capacity of the cell to lower than 10Ah cause it will calculate that the time needed to discharge it at 35A is too long for 10Ah and the CBA heat dissipation is not made for that.. But in my CBA, i corrected that problem of heat.. so i just bypass the restriction by seting it to 1Ah.. it's just a data.. it not affect the discharge curve...

At the section 7 of the getting started the wrote:
CAUTION: DO NOT CHOOSE A HIGHER DISCHARGE RATE THAN THE BATTERY IS CAPABLE OF. SEE THE BATTERY MANUFACTURE’S SPECS. Note: If the no load battery “Voltage” multiplied times the “Test Amps” selected (Volts x Amps = Watts) exceeds the wattage rating of the CBA, or the default recommended maximum discharge rate for a given battery type, our software will prompt you to lower the discharge current before starting a test. The CBA will run tests at up to 150 watts with a battery that has a rated capacity of 1 Amp-Hr or less, up to 125 watts below 3.5 Amp-Hrs and 100 watts for any capacity battery.




Doc

 

[pgt400]

Since everyone else is showing off their flat curves.... Here's what the BMI cells can do at a 10C discharge.
Notice, you get > 10AH at that discharge rate.



http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MESELX:IT&item=130271429385

Mcstar, the BMI cells are great for sure. But for a motorcycle very, very expense....maybe if I only needed 24 cells for e-bike is one thing. But 96 cells...no way. E-bikers can use Pings and have great results for much less then BMI but their (pings) C rate is not enough for motorcylces. Thats why many of us are interested in the Headway cells, at around $18 each with improving quality they are starting to look real good. I've mentioned to Ping about carrying them....maybe in spring.

 

[ZapPat]

I actually would tend to question if even these improved headway cells could really do anything over 3C continous once assembled into a complete pack. If a single cell's temp hit 51oC while doing 3.5C, I could imagine it could get quite a bit hotter than this if it's situated inside a battery pack (specially in the middle). A cell inside a pack is not able to cool itself using ambient air like a single cell, PLUS it also has to cope with added heat being generated by surrounding cells. I think this something to be well thought about, and I guess it's why testla uses liquid cooling in their battery pack too.

I guess it's time to install a number of temperature sensors right inside my ping pack, and redo a couple discharge tests! Ping's v2 cells have about 40-50% more internal resistance than these new headway cells, and thus generate more heat while being used, which is what mostly limits the C rate according to a few people here (Doc Bass included).

 

[Doctorbass]

In large battery pack, like for the tesla, plugin prius, etc, they use some fans ro make the air circulating around every cells.
That create many advantages:

that prolong the battery life,

that help alot for keeping the balance state of them,

that avoid cell overheat.

Just a small fan like 3" that could be activated by a load sensing could be great for pack larger than 0.5kW..

Otherwise i would recommand to arrange the cell in two row.. so the surface to the exterior is optimized and would help for heat dissipation!

Doc

 

[Kurt]

I am not sure if this is relevant but when pulling 2.5c from my headway pack 5304 50A controller going up through the hills in my area. After the ride I cant feel by hand any significant temp increase over ambient.I have 24 cells arranged in a brick shape.They are also seal up in a cooler bag.

Perhaps when running the cells in a electric car/motorbike you could pull 5 or 10C constant for your entire trip and they would get hot. But wouldn't you run a much bigger capacity pack in a car anyhow like 50 or 100AH ?

kurt.

 

[dimitrib90]

it will be good to understand why it has the knee at the end for the low discharge:

http://www.endless-sphere.com/forums/download/file.php?id=15974

Ah haaa.. that'S one of the "beautifull" features of the CBA at 35A.. it does that each time i do 35A.. I need to specify that set the 35A an d that the software accept it in the parameters, i NEED to set the capacity of the cell to lower than 10Ah cause it will calculate that the time needed to discharge it at 35A is too long for 10Ah and the CBA heat dissipation is not made for that.. But in my CBA, i corrected that problem of heat.. so i just bypass the restriction by seting it to 1Ah.. it's just a data.. it not affect the discharge curve...

At the section 7 of the getting started the wrote:
CAUTION: DO NOT CHOOSE A HIGHER DISCHARGE RATE THAN THE BATTERY IS CAPABLE OF. SEE THE BATTERY MANUFACTURE’S SPECS. Note: If the no load battery “Voltage” multiplied times the “Test Amps” selected (Volts x Amps = Watts) exceeds the wattage rating of the CBA, or the default recommended maximum discharge rate for a given battery type, our software will prompt you to lower the discharge current before starting a test. The CBA will run tests at up to 150 watts with a battery that has a rated capacity of 1 Amp-Hr or less, up to 125 watts below 3.5 Amp-Hrs and 100 watts for any capacity battery.


Doc

So does this mean that you cant test the battery at 10C? BTW I like how it says "Doctorbass CBA PRO" on your CBA II program.

 

[Doctorbass]

it will be good to understand why it has the knee at the end for the low discharge:

http://www.endless-sphere.com/forums/download/file.php?id=15974

Ah haaa.. that'S one of the "beautifull" features of the CBA at 35A.. it does that each time i do 35A.. I need to specify that set the 35A an d that the software accept it in the parameters, i NEED to set the capacity of the cell to lower than 10Ah cause it will calculate that the time needed to discharge it at 35A is too long for 10Ah and the CBA heat dissipation is not made for that.. But in my CBA, i corrected that problem of heat.. so i just bypass the restriction by seting it to 1Ah.. it's just a data.. it not affect the discharge curve...

At the section 7 of the getting started the wrote:
CAUTION: DO NOT CHOOSE A HIGHER DISCHARGE RATE THAN THE BATTERY IS CAPABLE OF. SEE THE BATTERY MANUFACTURE’S SPECS. Note: If the no load battery “Voltage” multiplied times the “Test Amps” selected (Volts x Amps = Watts) exceeds the wattage rating of the CBA, or the default recommended maximum discharge rate for a given battery type, our software will prompt you to lower the discharge current before starting a test. The CBA will run tests at up to 150 watts with a battery that has a rated capacity of 1 Amp-Hr or less, up to 125 watts below 3.5 Amp-Hrs and 100 watts for any capacity battery.


Doc

So does this mean that you cant test the battery at 10C? BTW I like how it says "Doctorbass CBA PRO" on your CBA II program.

The new version include an option to use the cba as a monitoring graph.. without drawing any current if i remember.. so i'll use my CBA to monitor the curve and my Astroflight wattmeter to measure at 70-100A and to count the Ah... since the CBA can't go higher than 35A.

But.. from now.. the version 2 is bugged and now i can't re-open a previously recorded graph to overlay it to the nexts dish curves....... so i need to keep my CBA open 24h/24...

Doc

 

[powermed]

"I actually would tend to question if even these improved headway cells could really do anything over 3C continous once assembled into a complete pack"

I wouldn't question it too much from my experience over the last week. Ran them deliberately hard the other day on my mid-engine at "24v" on a 1000watt powerpack ride - they performed similarly to my 29v Prius pack which can do 10C and performs (on my rig) much like an A123 pack. From my past experience the ride would have been = about a 4-5C rate, and I ran for a solid 20 minutes. No problems, as another has reported, I didn't notice any warmth to the pack (my pack is 4x2 with plenty of ventilation). I have no easy way to test them at higher draws than 4-5C though.
z.

 

[ZapPat]

"I actually would tend to question if even these improved headway cells could really do anything over 3C continous once assembled into a complete pack"
I wouldn't question it too much from my experience over the last week. Ran them deliberately hard the other day on my mid-engine at "24v" on a 1000watt powerpack ride - they performed similarly to my 29v Prius pack which can do 10C and performs (on my rig) much like an A123 pack. From my past experience the ride would have been = about a 4-5C rate, and I ran for a solid 20 minutes. No problems, as another has reported, I didn't notice any warmth to the pack (my pack is 4x2 with plenty of ventilation). I have no easy way to test them at higher draws than 4-5C though.
z.

Ok, I'll soften my blunt statement above in the light of bill's and kurt's experiences. I guess smallish packs have no problem because of exposed surface each cell has to the outside, and larger packs will fare well with some adequate ventilation to help the cells in the middle stay cool. However, I do question bill's observations a bit, since the math doesn't quite fit together: Running 4-5C constant for 20 minutes is quite impossible! Plus I assume there was still some charge left...

I had said this because DocBass's 3.5C test yielded an end temperature of about 50oC according to him - which is starting to get close to the degradation zone for LiFePO4. One interesting observation that Doc made is that it takes a fair amount of time for heat to move from inside the cell to it's outside surface. Too bad we can't have a temp sensor inside a cell to see what temperature differential this causes the cell to have at something like 5C!

I must say these newer headway cells do sound quite improved compared to the old ones. There seems to be less quality issues too so far. Can anyone give prices for recent purchases of the newer cells?

 

[pgt400]

There was a large group buy on yahoo, its taking forever for them to get the cells, but supposed to be end of month. Prices were around $18 per cell. I recently bought 4 for $23 each just to test and Victoria quoted me less then $20 ea for 100 a couple months back. I've been waiting to see how the new cells work out.

 

[ZapPat]

There was a large group buy on yahoo, its taking forever for them to get the cells, but supposed to be end of month. Prices were around $18 per cell. I recently bought 4 for $23 each just to test and Victoria quoted me less then $20 ea for 100 a couple months back. I've been waiting to see how the new cells work out.

After following that group buy discussion a couple months back, I wouldn't even touch it with a long stick! Nothing was clear, and the organiser didn't help make anything clear either. Something wes said one day, and a couple days latter something else contradicted it (from the same person!). And all this to save 2 bucks a cell?? Someone must have skimmed off some overhead for sure no matter what they say. If only that overhead was really going to an EV developement fund (as stated once on the group), I would forgive all the crazyness involved!

At 20$/cell, this comes to about 0.66$ per watt for 5C capable cells... pretty good! Just wish I had some spare money right now to try a couple out myself.

 

[dimitrib90]

There was a large group buy on yahoo, its taking forever for them to get the cells, but supposed to be end of month. Prices were around $18 per cell. I recently bought 4 for $23 each just to test and Victoria quoted me less then $20 ea for 100 a couple months back. I've been waiting to see how the new cells work out.

After following that group buy discussion a couple months back, I wouldn't even touch it with a long stick! Nothing was clear, and the organiser didn't help make anything clear either. Something wes said one day, and a couple days latter something else contradicted it (from the same person!). And all this to save 2 bucks a cell?? Someone must have skimmed off some overhead for sure no matter what they say. If only that overhead was really going to an EV developement fund (as stated once on the group), I would forgive all the crazyness involved!

At 20$/cell, this comes to about 0.66$ per watt for 5C capable cells... pretty good! Just wish I had some spare money right now to try a couple out myself.

Yeh these cells look like the real deal but I wish that they would have some sort of connectors to connect these cells together. I guess I can always go to the local hardware store though.

 

[dimitrib90]

There was a large group buy on yahoo, its taking forever for them to get the cells, but supposed to be end of month. Prices were around $18 per cell. I recently bought 4 for $23 each just to test and Victoria quoted me less then $20 ea for 100 a couple months back. I've been waiting to see how the new cells work out.

Was that price shipped or just for the cells?

 

[dnmun]

there are a few people who have paid for their headway packs in the group buy who now find they no longer can use them, but they will arrive in ft lauderdale next week or the week after. if you are interested, go over and ask on the group buy website if anyone is interested in selling you their pack. and gaston wanted to sell some of the loose cells and a battery pack he was getting in the group buy too. the one 48V20Ah pack with charger and case i remember was $758 with the shipping included, sounded like a really good deal, and it is now obvious these will be first class batteries, not like the useless stuff people got off ebay. lifepo4-purchase@yahoogroups.com should get you there. worth the wait i think.

 

[dimitrib90]

there are a few people who have paid for their headway packs in the group buy who now find they no longer can use them, but they will arrive in ft lauderdale next week or the week after. if you are interested, go over and ask on the group buy website if anyone is interested in selling you their pack. and gaston wanted to sell some of the loose cells and a battery pack he was getting in the group buy too. the one 48V20Ah pack with charger and case i remember was $758 with the shipping included, sounded like a really good deal, and it is now obvious these will be first class batteries, not like the useless stuff people got off ebay. lifepo4-purchase@yahoogroups.com should get you there. worth the wait i think.

$758 sounds pretty expensive. At $20 a cell, a 48V 20ah should only cost 640 dollars.

 

[pgt400]

The packs came with cases and a BMS as I understood. The price I was quoted was $19 a cell plus $140 for shipping for 96 cells. I also got a price from PSI that was $24 per cell, but that was from Raymond, who now works for Lifebatt.

 

[julesa]

Huh, I seem to remember a quote direct from Victoria saying she would send a 48V 20Ah Headway pack, including BMS and a 3A charger, for $630 plus freight with no minimum order. So if that's what ol' Joshua Goldberg was charging for slow-boat shipping, I feel sorry for everyone involved in that group buy. I chose not to get involved because Joshua attacked me when I asked him some simple questions about how the group buy process was going to work, when he expected payment, how much was needed up front, etc. Ypedal probably remembers this. Goldberg ripped me a new one, saying basically how dare I ask questions, how rude of me it was to question his reputation when he wasn't making one red cent on the deal and was doing it out of the goodness of his heart, blah blah blah. What a crackpot. And $758? If that's true, he's a crackpot AND a jerk for lying about not making any money on the deal. I could probably order the same pack, BMS and charger today and have it delivered via air freight by Christmas for $800.

 

[Ypedal]

Well.. it's like this.. I have known Joshua for over 4 years now, member on " Power-Assist " and on " E motor assist " and the Lifepo4 group.. and this forum.. and the V forum.. and other forums.. you get the idea.

Joshua is an old man, his heart is in the right place ( I do worry about his mind some days tho ) and is a good person, the answer you got was from an old grumpy man who was likely having a bad morning.. he's usually in a pretty good mood. I assure you he's not making a dime on this group buy, quite the oposite actually.. it's costing him out of his own pocket because he did not include extras to cover the inevitable.. This i know for a fact.

I have dealt with many people over the years.. Joshua may not be the best person to manage the group buy but he certainly has experience dealing with importing stuff from china. Not everyone is willing to send money to another country, having someone deal with all the details is a comforting thing for many.. the group is also a source of help when need be.

All that said.. there was a problem that has resulted in my not getting my pack and cells on this shipment, i just found this out recently.. not the first hickup i have dealt with.. won't be the last. .. but what'cha gonna do.. :|

 

[dnmun]

sorry to upset you guys, i was just repeating what i read from the group buy digest. someone said they needed to sell their pack, with charger, and case and shipping and i remembered 758, that could be wrong, also i guess paypal fees, so $630+50+15+42+2.5%, but like i said go there if you are interested in getting a cheap and powerful pack, i got a quick response the only time i ever contacted joshua, he seemed helpful, most would have hard time hanging their reputation on so much money, and i can't fault him for the problems which started with don originally since the original deal was gonna be for lifebatts until michelle pulled the plug on that and don had to screw everybody over, so joshua got the blame. i am a crotchety old man too so don't be lecturing me when i just tried to help someone pick up a cheap 48V20Ah pack. it does appear these cells are superior and the quality of the headway BMS that kurt showed pictures of was very high, imo. seems like the best deal around imo.

 

[Doctorbass]

Hey guys....

Just about group buy.. I MAY HAVE A CONTACT FOR SOME OF A 4000 cells from a container... I mean 4000 of these 38120 10Ah Headway with terminal screw.

I can not confirm from now but i asked to the guy if he would accept selling some of them and he said he will see.

I dont want to name it to avoid rumours but I know he was using some for a large car audio battery. I respect this person and he also have alot of respect from the SPL car audio community.... and had some old SPL world record too !

He also visited the factory of the headway cells! and sent me some pîcs. I still wait to know if he would accept that i share them here.

By the way, My Doctorbass nickname came from these SPL contest community whne i was competing...

Doc

 

[dnmun]

wow, that would be neat. then we could build 24S2P packs with the new open source BMS, you had built a huge amplifier as i remember, 2000W?