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Old Sep 14, 2012, 12:27 PM
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Powerlab8 Lipo charging questions

Hello, I want to charge a single 6s1p battery pack and am unsure of some of the charge options in the software. Charger is a powerlab 8.
The batteries are Turnigy 5000Mah, 6s1p, 2c charge, 20c discharge.

http://www.hobbyking.com/hobbyking/s...dProduct=16207



Charge Amps: , Am I better off setting it to 2c? Or should I set it to 10 amps?

C/? Termination: What is this exactly, what should I set this to?

Cold Weather: It is 70-85 degrees in my charging area. Do I need to set this? It defaults to 50F. Should I set this to none or leave it at 50F?

Discharge Voltage: I read where you should not discharge a Lipo below 3.65V. Why does it default to 3.30V? Should I change this?

I just got these batteries new. Is there any reason to discharge them before I charge them?


Here is an optional question if someone has the time to help me out.
This is a parallel charging question. I want to charge 4 batteries in parallel using a board.
Here is my power supply.
http://www.hobbyking.com/hobbyking/s...dProduct=17414
Output Power: 600w
Output Voltage: 17v
Output Current: 0-36A


When charging 4 of these 6s1p batteries using the power supply in the link. What are the best charge settings I should use?
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Last edited by Eddie500; Sep 14, 2012 at 12:33 PM.
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Old Sep 14, 2012, 03:30 PM
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Hi:

Comments below in red...



Quote:
Originally Posted by Eddie500 View Post
Hello, I want to charge a single 6s1p battery pack and am unsure of some of the charge options in the software. Charger is a powerlab 8.
The batteries are Turnigy 5000Mah, 6s1p, 2c charge, 20c discharge.

http://www.hobbyking.com/hobbyking/s...dProduct=16207



Charge Amps: , Am I better off setting it to 2c? Or should I set it to 10 amps?
It all depends on your comfort level with charging. the AUTO C, 2C, 3C modes are convenient, but it takes them a while to ramp up because the unit has to be conservative so it's safe. So a lot of people would rather set the charge rate manually. For the battery you listed above, a 2C charge would be 10A. If you know how to calculate a 2C rate based on the pack capacity, you will ultimately be more happy with the results doing it that way. If you just want the easiest, most convenient approach, use AUTO modes.

C/? Termination: What is this exactly, what should I set this to?
The default presets usually use C/20 or C/10. In this simple formula, "C" is the battery pack capacity. So, when a LiPo charges, it starts out with CC (Constant Current) mode. In CC mode, the unit regulates the current at the set charge rate. After the cells reach approx 90% charge, the unit switches to CV (Constant Voltage) mode. In CV, the unit regulates the voltage to make sure it never exceeds 4.2V per cell (or whatever you have the per cell termination voltage set). It will maintain this voltage regulation as the current falls off further and further. When the termination C/? is reached, the charge is complete. So, if you had termination at C/20 on your 5000 mAh battery pack, and you had set the charge rate to 10A, it would stop at 10A/20 = 0.5A (or 500 mA). This is a simplified answer, but it will give you the idea of how the charge process works and how the charge gets terminated.

Cold Weather: It is 70-85 degrees in my charging area. Do I need to set this? It defaults to 50F. Should I set this to none or leave it at 50F? If it never drops below 70 deg F, I'd either turn this feature off, or set it to 32 deg F. Sounds like you'll never need it. It is bad to charge a LiPo to 4.2v (100%) when ambient temperatures drop below 50 deg F. It does permanent damage to the cells.

Discharge Voltage: I read where you should not discharge a Lipo below 3.65V. Why does it default to 3.30V? Should I change this? You should follow your battery manufacturer's recommendations on this. I am told that a log of newer LiPo cells should not be taken as low as the defaults. In our experience, it doesn't hurt the batteries we've owned, but we are not the experts on battery chemistry, only battery charging. That's why we allow access to 100 or so adjustable parameters in the PL8 open architecture presets. Therefore, trust what the battery manufacturer tells you.

I just got these batteries new. Is there any reason to discharge them before I charge them? I'll let others chime in here and I'm sure you'll hear a lot of different opinions if they do. I think the most common sense answer is, break them in by charging them up at 1C the first couple times, and simply discharging them in the model, but don't go crazy. Just fly, nice, gentle circuits with new packs the first few flights. But again, I'm not the expert on matters of battery break in; just passing along what makes the most since to me from various things I hear.


Here is an optional question if someone has the time to help me out.
This is a parallel charging question. I want to charge 4 batteries in parallel using a board.
Here is my power supply.
http://www.hobbyking.com/hobbyking/s...dProduct=17414
Output Power: 600w
Output Voltage: 17v
Output Current: 0-36A


When charging 4 of these 6s1p batteries using the power supply in the link. What are the best charge settings I should use?
Here's the good news. PowerLab Battery Workstations are extremely smart. They offer you Smart Power Management. Read up on that in the user guide and set your input supply current limit to just below what the power supply is spec'd. In your case, I'd set that number to say 32A. I'd set the input supply low voltage setting at 12v. Now, decide how fast you want to charge each of the packs you will be connecting to the PL8. If there will be multiple 5000 mAh packs, for example, and you want to charge each at 2C, set the preset's charge rate for 10A. Then when you charge, connect up the packs in parallel, call up the preset you set up to use, and answer the question about #P correctly. If you're charging 3 packs in parallel, the answer is "3P". The PL8 will do the rest, and if will charge the packs at the 10A each you selected for the preset, or as quickly as your PSU will allow based on the input current limit you set, without letting your PSU get damaged. Following these steps takes all of the guesswork and worry out of it, and the PL8 will do all the math for you.
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Old Sep 19, 2012, 07:47 PM
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Thanks for the reply, I have read it some days ago and charged my batteries.

I know exactly what you mean when you say that some of the charging methods are opinion based. It is similar to 2500 mile oil changes. I used to do 2500 mile oil changes in the past then I read where Europe does 15,000 mile oil changes and read the controversey on the internet

Now i do 10,000-15,000 mile oil changes for years and my cars never ran better. People will still argue that you need 2500 miles or 3 months, but from my research, it seems that that you can probably go 30,000 miles or 2-5 years on a synthetic oil change and probably be OK. However, I stay between 10,000-15,000 and try and do it at least every two years. But I seem to get lazy as I keep pushing the oil changes longer and my cars seem to run just as smooth as they ever did. My cars have over 150K miles also.
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Old Oct 19, 2012, 11:56 PM
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I have a C/? termination question. I have set my C/? termination to C/3 I blieve so that the charge stops as fast as possible. But this only gets me to around 4.07 volts instead of 4.1 volts.

I was wondering if I can set my voltage to around 4.13 volts and keep the C/3 setting so that it will stop the charge process sooner and this should give me roughly around the 4.10 volts I want.

Is there any harm in doing this? I don't really care if my voltage is 4.09 or 4.11 volts, I just want it to charge as quickly as possible to around 4.1 volts and then stop.

Another question is there anyway to set the C/? termination on the charger itself, or do you need to use the software? I see no option to change it on the charger itself.

Thanks
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Last edited by Eddie500; Oct 20, 2012 at 12:18 AM.
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Old Oct 20, 2012, 01:10 AM
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Because you are not requiring the cells be at 4.2v that gives you some flexibility. You can set the voltage to overshoot your target anticiplating the fallback. As I recall there were some older chargers that did this, charging the cells past 4.2v and letting the normal voltage sag bring the cells back 4.2v.

I'm not a fan of over charging LiPos and would not recommend that approach. But targeting 4.13, for an end result of 4.1v os perfectly safe. However, do note that the voltage sag varies by pack quality and age. The better and fresher the packs, the less the voltage will sag. So you may find that you are not aways hitting 4.1 over time.

As another datapoint I did some tests a while back to see how fast I could charge a 3300 6s pack without changing the charge current. Below are my results which you might find interesting. Also note that i changed the balance deadband and balance set point. Something you might want to play with. Unfortunately you will need the PC interface to do so.

Starting from storage charge 3.84v

C/20
Time 16:55
Mah 1497
V 4.195,200,201, 201,201,196
Delta .006mv
Balance deadband 2mv
Balance set point -1mv

C/10
Time 13:48
Mah 1462
V 4.192, 196, 192,196,192,192
Delta .004mv
Balance deadband 5mv
Balance set point -2mv

C/3
Time 11:51
Mah 1466
V 4.182, 187,184,188,187,182
Delta .006mv
Balance deadband 2mv
Balance set point -1mv

In the end, the default settings are going to give the most predictable results time after time in more scenarios. But you can definitely achieve a faster charge time if you are willing to give up a small amount of 100% fully charged cells. Some insist on thier cells ending at 4.2v. As I said above, the 4.1v target frees you up a little. Enjoy your freedom.
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Old Oct 20, 2012, 03:09 PM
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Haralson County GA. USA
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If your LiPolys are well matched and require very little if any balancing then setting the Blanacing to start later in the charge will trim some time off. I have one Preset where Blancing starts at 4.1 V per cell that I use for my really good 45 to 65C discharge 10-12C charge capable Lipolys and at 5C charge rates it knows a few minutes off even using the C/10 termination.

The Power Labs are extremely versatile and one can do some very serious tweaking.

Charles
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