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

[Doctorbass]

Hey Doc,

Did you ever get a chance to compare Ypedals PSI cells to the newer Headway?

That's on the to do list!

I'm a little busy these times.

Doc

 

[dimitrib90]

might as well buy a ping pack

I dont know if you noticed but pico1 looks like our friend from Falcon-EV. He's uploaded the same graph that our buddy has on his website. Maybe pico1 is taking a peek at our forums.

EDIT ADD: Pico's graph at 3C is no where close to Dr.Bass' graph at 3C. Im going with Doc on this one.

 

[mcstar]

I sent 2 of the recent PSI green sleve cells a few days ago, it would be interesting to see if they are the same as the Grey cells or not..

Just to keep everyone up to date, I sent Doctorbass 1 of the new gray black labeled BMI cells last week, and Armin is sending anther one from his stock in AU as well. These two cells are from two different batches, but made on the same assembly line with the same high quality standard. They should be identical in terms of performance and quality owing to the impressive quality control of the new plant they are being built in. Hopefully soon we'll have some good comparison charts according to Dr Bass' schedule. It's a good idea to have all the different types of cells tested on the same setup as this should give us a good objective comparison baseline.

Thanks for taking the time to do this Doctorbass! (Feel free to keep the cell I sent you for your own use when done)

 

[jimw1960]

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?Vi ... 0271429385

mcstar. Please don't take this the wrong way, but aren't you mistaken to call the graph for your BMI cell a 10C discharge? If I am reading right, it looks to be 35A dropping to 25A, so isn't that a 3.5C discharge rate? Maybe Drbass can show what the BMI does at 10C when he tests the samples you sent.

 

[julesa]

might as well buy a ping pack

I guess Headway's prices must be getting some vendors' knickers twisted...

 

[auraslip]

This thread really reiterates the importance of thermal management. I was looking at the battery pack design in new hybrids, and they've put a lot of consideration into air flow!

If you want to run a headway pack above 3c, you'll need proper ventilation and temperature sensors? I have my current pack enclosed in a wooden box, but I have air vents facing the direction I travel. I thought this would be enough to scoop in all the air I needed, but I think I'm going to need to add some fans as well.

These compare favorably to ping, but it makes you wonder if ping could handle 2c with proper ventilation.

In any case a 72v10ah pack of these at 3c is 2100+watts, which is much more power than my current 48v20ah ping is capable of. When I upgrade to the aforementioned headway pack, I'm hoping I'll get at least to 40mph (up from 33mph). Ping is 1kwh, and the headway is ~750kwh. Ping cost ~$800, headway should cost ~$600-700. Ping weighs 20lb, headway will weigh 18lbs.

So they weigh and cost about the same per wh, but the headway is easier to cool, provides a higher C rate, and is easier to do maintenance on. Really the only thing ping has going for it is the reliability of the dealer, and the smaller size. Arguably the small size is a weakness because it makes it harder to cool.

 

[oatnet]

Wow, that is a gravedig of the very first appearance of Headway 38120s' on Endless-Sphere, when I started buying them for my VW Bus conversion. Funny to think how ubiquitous they have become after only 2 years.

Wood is an excellent insulator and could be inhibiting your attempts to cool your pack.

-JD

 

[Spacey]

Now you've got me worried as I've just put my 2 x 10 cell 16ah Headway pack 66v in a water tight box as the last pack I had was starting to rust on the terminals from the rain in UK.

I pull about 3C from the pack and average 15amps when up to speed, should I be worried about heat?

This thread really reiterates the importance of thermal management. I was looking at the battery pack design in new hybrids, and they've put a lot of consideration into air flow!

If you want to run a headway pack above 3c, you'll need proper ventilation and temperature sensors? I have my current pack enclosed in a wooden box, but I have air vents facing the direction I travel. I thought this would be enough to scoop in all the air I needed, but I think I'm going to need to add some fans as well.

These compare favorably to ping, but it makes you wonder if ping could handle 2c with proper ventilation.

In any case a 72v10ah pack of these at 3c is 2100+watts, which is much more power than my current 48v20ah ping is capable of. When I upgrade to the aforementioned headway pack, I'm hoping I'll get at least to 40mph (up from 33mph). Ping is 1kwh, and the headway is ~750kwh. Ping cost ~$800, headway should cost ~$600-700. Ping weighs 20lb, headway will weigh 18lbs.

So they weigh and cost about the same per wh, but the headway is easier to cool, provides a higher C rate, and is easier to do maintenance on. Really the only thing ping has going for it is the reliability of the dealer, and the smaller size. Arguably the small size is a weakness because it makes it harder to cool.

 

[auraslip]

I don't really know. When I was doing research for the lifespan of lithium batteries, I found heat made difference. Most of the tests were done by NASA and the such for batteries in satellites. Basically heat during discharge (and charge!) had a big effect on lifespan, but I wasn't specifically search for info related to heat. I need to do some more research!

I'm considering something like this to monitor my battery pack.

Or maybe this - http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9744

I really want one that does two inputs. One for motor, and one for the battery. I think some people have found cheap BBQ temps with dual readings.

I also forget to mention about the original test. The first cell performed poorly compared to the second. I know that all lithium batteries undergo a chemical change the first dozen discharges. Lipo needs to be broken in softly, and IIRC a quality battery is usually broken in similarly at the factory. Perhaps headways need to be broken in as well?