Ocean Cheer 36v15ah LiFe pack - DIscharge Graph

[oatnet]

Here is a discharge curve from the OC Life Pack at 2.37ah (.15c?) on a CBA II . The discharge curve is nice and flat, but falls about 1.1ah short of the rated capacity. Voltage was droppiing off fairly quickly so I stopped the discharge, it _might_ have pulled that extra 1.1ah out before flatlining, I didn't see the need to stress the battery.

-JD

 

[oatnet]

And, for good measure, here is the discharge curve of the 10ah FalconEV LiMn agains the 15ah Ocean Cheer LiFe. Note the differences! When I get the 15ah Falcon EV LiMn we will have a very interesting comparison indeed.

-JD

 

[xyster]

Right in line with other charts showing a very flat discharge curve for LiFePO4, and a typical li-ion/lipoly slope for LiMn. LiFePO4's super flat discharge makes it difficult to meter remaining capacity without an energy counter like the CycleAnalyst. I like a slight slope better -- just enough to be able meter the pack with a voltmeter; just enough to be able "feel" when the pack is getting low by the slightly softer throttle response, while not losing too much power as it discharges.

 

[erdurbin]

I didn't really do any looking, but what kind of software/hardware do you use to display the discharge curves? I should be receiving my LiFePO4 pack next week and want to do something similar for comparison to SLA.

Are you just monitoring and recording the numbers yourself, or do you have something set up to record automatically and make a graph?

 

[oatnet]

Are you just monitoring and recording the numbers yourself, or do you have something set up to record automatically and make a graph?

I am using West Mountain Radio's CBA-II, @$110, if you google it sometimes you can get a deal from someone reselling them. I got the temp probe for free with mine, which was useful as an emergency cut0off with NiMh, not so useful with LiFe. This is one of the better investments I have made during my foray into ebikes.

http://westmountainradio.com/RCintro.htm

I got all excited looking this up, they have a new add-on that will let you boost CBA output to 500w (1000w in pairs) - but then I saw the add-ons or $600+ each. Guess I'll keep stress-testing on ebikes!

-JD

 

[Ypedal]

Stress tests can be done very cheap with many light-bulbs in paralell and your CA meter !!! ( no fancy graphs, but allows bench tests at high-amps !! )

The flat discharge curve of the LiFE cells is interesting..

 

[CGameProgrammer]

Computerized Battery Analyzer

I should buy one myself. EDIT: Ah, beaten already.

 

[oatnet]

Computerized Battery Analyzer <---- This is $5 more than direct from the manufacturer.

I first found it with this joker on ebay, at $20 more the WMR - and then googled it back to WMR:
http://cgi.ebay.com/Computerized-Battery-Analyzer-Tester-CBAII_W0QQitemZ4439033793QQihZ001QQcategoryZ42291QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

It is important to note that the features says it will do 150 watts/40amps, it will only do so at lower voltages - like 3.5v. On a 36.0v pack it is only rated to 100w, and even then I have had it overheat on me and time out (really bummer on a 20ah pack) so now I always try to keep it under that. For me, 2.39a on a 42.5v (charged 36v) pack seems to run happily at about 90-94 watts after sag.

-JD

 

[Lowell]

I found that an extra fan blowing on the heat sink helps when running right at the watt limit of the CBAII.

 

[erdurbin]

Ok, that looks like something I could use. I think I saw something similiar on batteryspace.

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3200

Same thing.
I wish I would of seen this before I bought my watts up meter.
Guess I could sell it on ebay and buy this.
http://westmountainradio.com/WhattmeterRC.htm
Anybody used one of these? I have a 36v bike so it should be sufficient. 30 amps is the max I pull.

 

[oatnet]

Ok, that looks like something I could use. I think I saw something similiar on batteryspace.

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3200

Same thing.
I wish I would of seen this before I bought my watts up meter.
Guess I could sell it on ebay and buy this.
http://westmountainradio.com/WhattmeterRC.htm
Anybody used one of these? I have a 36v bike so it should be sufficient. 30 amps is the max I pull.

If you want on-the-fly metering, ebikes.ca 's CycleAnalyst is hands-down the best choice. The "powerlink USB" looks interesting for metering with a light-bulb disharge source like Gaston mentioned, I might look into this.

-JD

 

[oatnet]

For some fluke reason, on one day I was able to get one of the OC batteries to recharge. Since then, I have only been able to get about 3ah into them, which discharges at nice even 35v. I tried 15 times to recreate the charge, swapping cables, and cable ends, starting with the battery connected first, etc

So today, I finally got around to opening one of the cases. Giant Flintstones Case aside, the array of individual cell chargers is impressive; there is a second row of 6 chargers under the first one, in one factory assembled unit. Click on the picture to see a ginormous version.

 

[oatnet]

But, the fatal flaw - a look at where the blue and black power leads terminate on the circuitboard, clearly shows that this was built for 220v operation, not 120v.

Is there any reasonable way (ie cheap, and within my limited skill set) I can convert it to run from 110v? Or supply this with 220v?

-JD

 

[OneEye]

Dryer hookup

 

[Ypedal]

http://www.voltageconverters.com/itemdesc.asp?CartId={FF27ED75-83B1-450D-840EVERESTE-3A9E0DF9DCE0}&ic=VC300W



A " Step Up " transformer.. or a simple plug for the dryer/store/water heater would do..

 

[patrick_mahoney]

To get 220V...

You could rewire a circuit in your house... Most in the houses in the US actually get 220V (110V in two phases, 180 out of phase) in from the street and then the breaker boxes split this into two 110V sets. If you want 220V, you can just tap off of both inbound 110V instead of a 110V and a neutral.

You could buy a large transformer. Get a 220V to 110V transformer from some electronics supply store (or from a electronics surplus, or from Radio Shack), or, if you are cheap and bored, get an old one and wind your own.

You could see if the on-board transformer is center-tapped and see if you could reconnect it to tap from that instead, effectively halving the ratio. This would be the most painful idea, I think, and I wouldn't recommend it.

PS - lest anyone think idea #1 is totally insane - that's probably what I would do. My charging station is close to my breaker box. I'd just put in a new box, buy a dryer plug and breaker at home depot and put in a 220V plug.

 

[fechter]

It's usually pretty easy to hook up a 220v plug to a house breaker panel.
There's almost always at least one 220v circuit for an electric stove or dryer. The problem would be if the panel was located far from where you want to charge. You'd have to run a wire.
The 220v circuit breaker(s) would have to be the appropriate size for the wire used. It would probably be best to add a new breaker if there's space in the panel.

 

[oatnet]

Sad news -

One of the chargers blew cell #11 on both packs before I realized that was the reason they stopped reaching full charge. You couldn't tell to look at cell #11, but when you feel it, it is squishy instead of firm and flat like the other cells. Plus it expanded enough to deform cell #12 - which still gives full voltage - into a concave shape with imprints from the bottom of the case.

Plus I am waiting for new discharge BMS's on both packs, as they will not provide power, I had to bypass them to do my CBA tests.

Plus these 15ah packs only supply about 13.75ah, unlike FalconEV's LiMn that provide more than the rated ah at the max draw rate.

I think the cost savings make up for the fact that they are only 2c, have overrated AH, and probably will fall far short of the cycle life of 'kwality' LiFe. However, while I think these cheap 2c cells have promise, but the supporting electronics is not quite ready yet.

FalconEV's LiMn packs, at a similar price point, are doing very well in my tests - but I'll post that in another thread when I get a chance, I've covered about 100 miles in the past 4 days doing assorted pack testing.

-JD

 

[BiGH]

sorry to hear it

is it covered by warranty of any knd?

 

[oatnet]

sorry to hear it

is it covered by warranty of any knd?

The vendor is still working with me but the responses are getting slower and slower. Earlier they promised new BMS's, they have not confirmed what they are going to do about the Power Supplies.

However, it has been my experience that warrantees out of China (and many in the USA!) aren't worth the paper they are printed on. Shipping the pack there and back would cost half as much as the pack itself. In a long term vendor relationship (like with xylte) you can get credit against future purchases, but in a case like this the integrity of the vendor is what counts - and that we shall see.

-JD