View Full Version : cx li-po charge rate question
12-15-2005, 02:39 PM
Hi all i got the cx about a week ago and have been using the charger/blancer and the ac adapter the adapter was like $19.00 but i use the hobbico mkII quick field charger for my cp my qusetion is what rate should the volts be set at to charge it on the hobbico i want to charge a few battries at the same time as they don't last long at all another dissapointment with the cx i guess. its the stock 7.4 800 Mah stock battery
ps: i don't want to max it out so a little under the normal volt rate would be all i need
12-15-2005, 03:02 PM
LiPolys should normally be charged at no more than a 1C charge rate. That means, one times its capacity in mAh. Your pack is 800mAh, so it should be charge at a rate of no more than 800mA, or .8A.
You should always use a 1C charge rate, or as close as you can get without exceeding 1C. Running at a lower rate does not help the cells balance. Running at a lower rate does not increase the battery's life expectancy. Running at a lower rate is not "safer" in any way shape or form. In fact, some chargers will incorrectly detect the number of cells you're trying to charge if you don't set it for a 1C rate.
If the Hobbico has a voltage or cell count setting, set it for 2 cells, 7.4V or 8.4V, depending on if the charger goes by cell count, nominal capacity, or fully-charged capacity, respectively. Read the instructions to find this information out.
12-15-2005, 03:28 PM
You should always use a 1C charge rate, or as close as you can get without exceeding 1C. Running at a lower rate does not help the cells balance. Running at a lower rate does not increase the battery's life expectancy.
Excellent advice from Matt. The only thing I want to add is some "battery experts" claim that charging at .7 C is easier on the cell and can increase cell life. I can not verify this, but I do usually charge at a little less then 1C with good results and cycle life.
12-15-2005, 03:40 PM
thank you for the reply guys so if i understand this i should have the volt rate at 0.7-0.8 on my charger it doesnt have a cell counter just volt rates
thank you very much
12-15-2005, 03:52 PM
Ask six knowledgeable users and get six different answers.
I have used 0.7C as my standard charge rate for LiPolys for the past 18 months and thousands of charges. The only problem(?) this has ever charged is that the AstroFlight 109 will time out if stage 2 does not complete in approx. 45 minutes. This will happen if the battery is more than 70% discharged. Charging at 0.7C takes very little longer than charging at 1C which has been considered the maximum charge rate for most LIPolys. I have never seen 1C listed as a minimum. Many of the factory life cycle test cells are charged at 0.5C throughout the testing. I will supply a link to one such test only. There are many more for those who care to search for such data.
Note the Discharge Characteristic Graph here. Legend charged at 0.5C .
Most agree that 1C is the max(soon to be changed for many LiPolys IMO). With some chargers there are limited rate choices such as 250 / 700 / 1500 / 2500 mA. When questioned if 750 mA rate can be used for a 700 mAh battery most everyone screams no! Well 750 rate is only(?) 7% to high and if you use 1000 mA rate for a 1000 mAh LiPoly which has lost 10% or more capacity then you are charging it at greater than 1C ,no?
12-15-2005, 03:58 PM
The only problem(?) this has ever charged is that the AstroFlight 109 will time out if stage 2 does not complete in approx. 45 minutes. This will happen if the battery is more than 70% discharged.
Charles..............Did you know you can get a "chip" from Astroflight to fix this annoyance?? I got three of them and they work fine.
rmbler..........I think you are confusing volts and amps. You need to charge a 2S pack at 7.4-8.4 VOLTS and keep the AMPS under .8
12-15-2005, 04:09 PM
Charles..............Did you know you can get a "chip" from Astroflight to fix this annoyance??
Yep I have been aware of the 10 hour Bob's special chip for a very long time.I rarely run my LiPolys down low enough for it to be an annoyance(?) and restarting is not a biggie to me. My AF 109 may end up not being used nearly as much when my TP-1010C arrives but only time will tell.
I feel like a kid on Christmas Eve.
Added: Some will read post at that link and become confused perhaps. Fact is I have had a pre production 210 since Aug. . which should explain my post on such.There were bugs to be eliminated. Charger was revised numerous times to add useful feactures.
Full discloser ,I do some Beta / field testing for Charlie Wang of Thunder Power.
12-15-2005, 04:14 PM
. My AF 109 may end up not being used nearly as much when my TP-1010C arrives but only time will tell.
I feel like a kid on Christmas Eve.
And the rest of us simply anxiously awaiting your feedback on the charger. Some guys have all the luck;)
12-15-2005, 05:52 PM
thanks for correcting me Doug your are right i did confuse volts for amps.
thanks for the reply
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