WattFlyer RC Electric Flight Forums - Discuss radio control eflight

WattFlyer RC Electric Flight Forums - Discuss radio control eflight (https://www.wattflyer.com/forums/index.php)
-   FMA Direct (https://www.wattflyer.com/forums/forumdisplay.php?f=228)
-   -   FMA Cellpro PowerLab 8 regenerative discharge power source? (https://www.wattflyer.com/forums/showthread.php?t=61467)

miernik 04-15-2011 02:08 AM

FMA Cellpro PowerLab 8 regenerative discharge power source?
 
What are the limitations on the power source used in case of using the regenerative discharge function?

Does it absolutely have to be a lead-acid battery, or can I have a chain of 8 LiFePo4 batteries as the power source and it will do fine? Eight LiFePO4 have the same charging voltage (28.8V) as two lead-acid batteries, so it should be possible to do? There will be no BMS, but if I make the source battery larger then the one on the other side of the charger, there should be no risk of overcharging, no?

I read that the Cellpro auto detects the power source, and will not allow me to use regenerative discharge if its not a lead-acid battery. Will it refuse a LiFePO4 instead of a lead-acid?

And what if the power source would be a battery and another 28.8V DC power supply connected to it in parallel, with a small limited current (say C/20) to replace the energy lost in charging inefficiency? Is that possible to do, or will the PowerLab refuse to do regenerative discharge in such setup?

I want to do long-term cycling of 10000 cycles at 4C of A123 and Headway cells. Headways are 10Ah per cell, and I want to charge/discharge them at 4C, which is a full 40A. It'd be problematic to get a large-enough lead-acid battery to accept so much charge, buying a 400Ah lead acid... no way! Much easier and cheaper to get another LiFePO4 and flush the energy back and forth between two LiFePO4 packs.

SteveM732 04-15-2011 04:20 PM

The PL8 determines if the power source is a battery or power supply, it does not know what chemistry the battery is. The PL8 currently assumes Lead-Acid of 12 or 24V and will stop regenerative discharge at a certain voltage when it determines that the battery is full. You can adjust this voltage a little, but I think the max is around 13/26V if I recall correctly. An 8S LiFe would be a good substitute.

I've not done charge/discharge cycles while charging the lead-acid battery, but I read about people doing it all the time, so you should be fine on that front.

Tim Marks 04-15-2011 06:21 PM

1 Attachment(s)

Originally Posted by miernik (Post 801252)
What are the limitations on the power source used in case of using the regenerative discharge function?

Does it absolutely have to be a lead-acid battery, or can I have a chain of 8 LiFePo4 batteries as the power source and it will do fine? Eight LiFePO4 have the same charging voltage (28.8V) as two lead-acid batteries, so it should be possible to do? There will be no BMS, but if I make the source battery larger then the one on the other side of the charger, there should be no risk of overcharging, no?

I read that the Cellpro auto detects the power source, and will not allow me to use regenerative discharge if its not a lead-acid battery. Will it refuse a LiFePO4 instead of a lead-acid?

And what if the power source would be a battery and another 28.8V DC power supply connected to it in parallel, with a small limited current (say C/20) to replace the energy lost in charging inefficiency? Is that possible to do, or will the PowerLab refuse to do regenerative discharge in such setup?

I want to do long-term cycling of 10000 cycles at 4C of A123 and Headway cells. Headways are 10Ah per cell, and I want to charge/discharge them at 4C, which is a full 40A. It'd be problematic to get a large-enough lead-acid battery to accept so much charge, buying a 400Ah lead acid... no way! Much easier and cheaper to get another LiFePO4 and flush the energy back and forth between two LiFePO4 packs.

Hi:

Although I didn't intend for our chief engineeer to spend SO MUCH time on this answer, he did. So I'll just post his reply back without any edits. Here you go:


The setup is pretty simple. A power supply will be required, because of the 10,000 cycle duration of the test. A battery needs to be connected to the power supply to allow the 40 amp discharge current.

Here is the setup.

1) Since the output battery is 10Ah, the supply battery should be 30Ah or higher. This will leave plenty of room to hold the discharge.
2) Connect the power supply in parallel with the supply battery.
3) Set the power supply voltage to 50% state of charge in the supply battery.
For example: The nominal LiFePO4 voltage is 3.3V per cell. This is the 50% SOC voltage.
A 7S supply battery should have the power supply set at 23.1V
4) The supply battery should be drained to 50% SOC before the test begins.
5) Set the data log rate to 120 sec. This will support data files that are over a year long. I haven't tested 1 year data files yet. I did test 1 month long files. I think you should be good to 65,535 cycles, but I am not sure.
6) Of course, you are going to need to dedicate a PC to this task. The PC should be connected to a UPS for power outages, which will surly happen. The Charger should be ok if power is lost because of the supply battery.
7) Turn off windows automatic updates and virus protection updates so that the PC can run for a year without rebooting. It might be a good idea to disconnect from the internet to guarantee that the PC will never try to re-boot.
8) Periodically save the gathered data to the hard drive using the File SaveGraph option in the main screen.

You will find that cycle life capacity decay is quite linear from 100% to 80%. Then cycle capacity drops off a cliff quickly. PL8 can actually predict cycle life based on 20 cycles by comparing the capacity of the 2nd cycle to the last cycle. However, PL8 will not predict cycle life beyond 500 cycles. If you find that after 100 cycles the battery has decayed 1%, the expected cycle life will be 2000 cycles to 80% capacity. If you find that after 100 cycles the battery has decayed 5%, the expected cycle life is 400 cycles.

9) It is very important to do the testing in a temperature controlled room. Cold temperatures really destroy lithium cycle life. Also, if the room isn't temperature controlled, you will see the capacity change from nighttime to daytime and back again. This isn't a big deal if you are running an end of life test. However, if you are trying to predict cycle life based on a linear decay, you will need account for the daily temperature changes and only compare cycles that were done at the same temperature.
10) Testing should be stopped at 80% capacity. This is the industry standard for all type of batteries, because the growth rate of the dendrites in the cell is cubic and very exponential. You will see what I mean if you run to end of life.


I believe the genuine A123 cells will go 10,000 cycles at 4C charge/discharge and room temperature. I have no idea what the Chinese copy cells will do.

I would be interested in seeing your data. I have found that what the cell manufacture says and what really happens are two different things.

kyleservicetech 04-15-2011 07:15 PM


Originally Posted by Tim Marks (Post 801357)
I would be interested in seeing your data. I have found that what the cell manufacture says and what really happens are two different things.

Reminds me of what happened to me in the early 1980's. A friend of mine was an Engineering manager who knew I was into high powered electric models. He got me a brand new 24 volt DC 1.5 Amp Hour Nicad battery Engineering sample from a well known Nicad battery supplier that was rated for 35 amperes continuous discharge current.

I grabbed it, ran a test at 28 Amps, and the voltage immediately dropped to 0.64 volts per cell. It melted the shrink wrapping off the cells. The manager contacted the supplier, who responded "That 35 Amps is a calculated value, we never test at that current!"

antiscab 07-05-2015 08:30 AM

Hi Guys,

I have a powerlab 6

I want to do long term cycle testing on a set of GBS 20Ah cells at 40A continuous

I can't figure out how to do more than one cycle at a time, nor anything other than cc-cv for charge and cc or cc-cv for discharge

is it possible to setup a discharge profile that simiulates regen? (so discharge at 40A for a while, then charge at 40A for a short while, then continue discharge at 40A) in an automated way?

Gregor 07-06-2015 08:32 PM

Yes, you can setup multiple cycles. Its easiest to setup using the CCS. Also, since the cells can ignite during cycling, I would not do this unattended.

kyleservicetech 07-07-2015 01:41 AM


Originally Posted by antiscab (Post 977356)
Hi Guys,

I have a powerlab 6

I want to do long term cycle testing on a set of GBS 20Ah cells at 40A continuous

I can't figure out how to do more than one cycle at a time, nor anything other than cc-cv for charge and cc or cc-cv for discharge

is it possible to setup a discharge profile that simiulates regen? (so discharge at 40A for a while, then charge at 40A for a short while, then continue discharge at 40A) in an automated way?

I did this on an A123 pack several years ago, using my Cellpro PL8 charger and its USB dongle. The attached shows just one charge/discharge out of a consecutive dozen or so cycles.

http://www.wattflyer.com/forums/showthread.php?t=70621

antiscab 07-07-2015 03:09 AM


Originally Posted by Gregor (Post 977469)
Yes, you can setup multiple cycles. Its easiest to setup using the CCS.

Terrific - I should mention that I am already using the CCS, but there doesn't appear to be an option to do multiple cycles - just single cycles that I have to trigger manually

clearly I'm missing something - can you supply a screenshot?

antiscab 07-07-2015 03:12 AM

wait - found it

Turns out you have to have the "advanced Properties" box *unchecked* to get access to more options

bit of an oddity, but there you go

Gregor 07-07-2015 04:04 AM


Originally Posted by antiscab (Post 977498)
wait - found it

Turns out you have to have the "advanced Properties" box *unchecked* to get access to more options

bit of an oddity, but there you go

When the advanced box is checked you'll find the cycles setting on the discharge tab.


All times are GMT +1. The time now is 05:00 AM.

Powered by: vBulletin
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.

Page generated in 0.04209 seconds with 7 queries