LiPo Charge Times? BC6 v. TP1010

[creightoncarr]

This may have been answered somewhere, but I didn't find anything helpful after searching, so here goes:

I am new to the electric world and recently built a Trex 450SE so that I would have something to fly in the backyard. I have three TP Extreme 2200 3S packs, each with about 10 cycles on them. I use both an e-station BC6 and a Triton 2 with Equinox balancer to charge the packs. I have not over discharged any of these packs, usually flying between 4 1/2 to 6 minutes on a full charge (no hard 3D, mostly lazy FF). I've always balance charged each of the packs at 1C, or 2.2 amps for the CC phase of the process. Depending on the flight times, I'm putting between 1600 - 1750 mah back into the packs during each charge. It's taking between 90-120 minutes to charge each pack, regardless of whether I charge with the Triton or the BC6. The charge times do not seem consistent - I can put 1600 mah into a pack in 90 minutes during one charge and then the next time it will take 120 minutes to put 1600 mah back into the same pack. What gives? I've had the BC6 time out a couple of times after two hours and while the charge was almost complete, it was not quite. Are these normal charge times? I had expected the charge cycles to be between 60-90 minutes.

And is 6 1/2 minutes of hovering time with a Trex 450SE (stock with 430L 3550kv motor and 13T pinion) about all I should expect from these packs? I had hoped I would get closer to eight or nine minutes, but that does not seem possible now. My gear mesh is fine and the belt is as loose as I can get without it slipping on me.

Thanks for the help. I know that the electrics require a lot less maintenance than the nitros, but I like that they don't require 2 hours to refuel. And I can but a lot of fuel for the cost of several of these LiPos. If this is what I can expect then I will make the best of it, however, if the performance should be better I would like to find out what I may be doing wrong and what I can do to improve the battery performance and cycle life.

[kgfly]

Balance charging can take longer than you might expect. Balance charging my HXT 3S 2200 12C/16C packs from the TRex usually takes 75 to 85 minutes. The CV portion of the LIPO charge cycle delivers approximately the last 10 to 20% of charge but can take 30 to 50% of the total time. When you add balancing (which selectively discharges cells) that can slow it down further.

While it is no suprise that my $35 cheapo packs are out of balance on every flight, I would expect TP Extreme packs to be better behaved, but perhaps not. Do the packs look out of balance when you review the per-cell voltage on the BC6 ? If you have the USB cable for the BC6 I suggest you log some charge cycles to your PC and take a close look at what's going on, it should become clear what is taking so long.

I would say 6:30 is short for just hovering but it depends upon your power train setup. On my 430L+11t running 325 Pro blades at 2400-2600rpm I would easily get 7:30 for a 1750mAh recharge. If you are running 430l+13t/2800-3000rpm then 6:30 is probably right.

To maximise flight time you could use 335 blades and a lowish headspeed. Lower headspeed is less stable in wind but needs less power and is less twitchy (aka responsive). I wouldn't recommend under 2200rpm but some people fly as low as 1800 for just blobbing around in calm conditions.

[creightoncarr]

Any thoughts on the BC6 vs. the TP1010 with the 210 balancer? I won't be charging any packs over 6S so that limitation with the BC6 is not an issue. I like the fact the BC6 has a built in power supply so I can run on AC power without having to carry around an external power supply and I like the fact the BC6 has a built in balancer. Both will log data to a computer via USB, correct? I do use all TP packs. If the 1010 and 210 are clearly superior to the BC6 for what I need I will make the switch, but otherwise, I like that the BC6 is all-in-one. I watched Finless' videos on the TP1010 with the balancer and Bob indicated that 100% charge ended when the amperage in the CV cycle was near 0.2 - 0.25 amps. With my BC6 the charge continues all the way down to 0 amps. The full charges can take nearly two hours at 1C and during the last 20-30 minutes only about 20 maH are put back into the pack. I assume there is no harm in ending the charge early and forgetting about those last 20maH?

[tppjr]

Instead of ending the charge early, do a "fast charge" in the first place. It bypasses the balance portion and gives a much faster charge time. It is the balancing portion that is taking up all the time. Check the cells before charging, if they are not out of balance then just fast charge. Balance charge the last charge for the day to settle things out.

You can get a fair amount of gas for the price of a good LIPO but you have to figure in the life of the LIPO too. How much gas would you have to buy to get the same fly time over the life of a LIPO? I would also suggest not being so decisive on using TP batteries especially since you are not flying to the level where you really need them. There are several packs out there that are much more reasonably priced and are getting good reviews, DN for one.

If you are thinking about switching to a TP1010 you will end up loosing money on the BC6 if you sell it, maybe invest in a second BC6 so you can charge two batteries at the same time.

Just some thoughts but I am just starting out in all this so I could be way off base,

Thomas

[kgfly]

The TP1010+210 is only superior to the BC6 if you need the hgher output power (220W/10A vs 50W/5A on BC6) or higher voltage (10S vs 6S). Otherwise it currently supports fewer chemistries and is less convenient. I think they have much the same features, although I don't know if the TP1010 has the equivalents to the BC6 Fast Charge and Storage Charge modes.

The last 20mAh doesn't count for much in terms of flying time (hovering a TRex is 8 to 10A so at most this adds 9s!

Thomas makes an interesting point, try a BC6 fast charge and let us know how long that takes.

[creightoncarr]

I have not tried the BC6 fast charge, but will tomorrow and post results. I flew two packs tonight, a TP Extreme 3S 2200 and a TP Extreme 2S 2070 to monitor the charge progress with the BC6. Hovered the 450SE four 4 minutes on each pack. Both packs had been balanced and fully charged prior to use.

Both charges were at 1C.

Pack 1 (2070) results:

Before charge voltages: Cell 1: 3.89; Cell 2: 4.03; Cell 3: 3.89 (surprisingly out of balance by a large margin)

At 40 minutes entered CV phase --> 1089 mAh added
At 97 minutes, charge finished --> 1196 mAh added


Pack 2 (2200) results:

Before charge voltages: Cell 1: 3.88; Cell 2: 3.93; Cell 3: 3.93

At 37 minutes entered CV phase --> 1095 mAh added
At 83 minutes --> 1204 mAh added
At 110 minutes --> 1222 mAh added
At 134 minutes --> 1232 mAh added
At 154 minutes --> 1241 mAh added (I ended the charge at this point)


The total draw on each pack during the 4 minutes flights was approximately 1200 mAh. Seems a little high (300mAh per minute) so I may try using a 12T or even 11T pinion and adjusting my pitch and throttle curves. I do like the higher headspeed, however, I don't need it for the type of flying I'm doing in my backyard.

154 minutes for 1241 mAh seems way off. Perhaps there is something wrong with the pack? Of the two, however, it was the one that was most in balance after use. I will try the fast charge tomorrow and see what sort of difference it makes.

[kgfly]

Certainly seems odd.

300mAh/min is 18A, seems way too high for hovering although I have never measured mine on 13t/3000+rpm. Is your motor/ESC/battery hot ?

Of course one problem with balance charging is that you cannot tell how much of the reported recharge was dumped by the balancer. Hence your actual discharge was less than 1196/1241 but we cannot tell by how much. With the integrated balancer I am guessing that you get no feedback about how hard the balancer is working. With the external ones there is usually one LED per cell that comes on whenever the balancer is active. Thus the occasional blink tells you not much is being bled off, while steady/bright leds and lots of flickering back and forth between cells tells you that the balancer is sucking charge a lot of the time.

I suggest you contact Evan at www.rcaccessory.com, maybe point him at this thread and ask his advice.

[creightoncarr]

The batteries are warm after flight, but not hot. The motor is warm/hot, but not to the point I can't hold my finger on it for several seconds. The ESC barely seems to break a sweat.

[RC Accessory]

The BC-6 by default has a Time Cut off of 2 hours. You can very easily change this setting in the User Setup. You can change the time higher or lower as well as Null the feature. That is why the BC-6 timed out.

Everyone is correct about the balance charge time. Balance charging does take longer. When you use the balance charge function on the BC-6, once the charge is started, use the middle buttons to bring up the cell voltage display screen. This will not only give you the cell voltages but you will see the imbalance if any.

If there is an imbalance the BC-6 will balance the pack but it will take longer. Same goes for the 1010 with balancer.

I can tell you that if you charged at 1C and it took longer than 2 hours (charger time out) you have a imbalance in the pack.

2 of my test packs for trade shows, one had a SEVERE imbalance. Using the BC-5 charger at the time, the charger timed out. Watching the cell voltages, the first 2 cells were nearly complete and another 1:30 went by before the pack was balanced and finished. The reason it takes so long is that the charger is dropping the charge rate as the pack voltage increases. The out of balance cell is trying to catch up and charge at a slower rate.

The comment about the Fast charge program is also correct. This program will the CC portion on longer and terminate the charge a bit early. As indicated the last portion of the charge process takes the longest time and puts in the least amount of energy. This program will not balance the cells but you can still monitor them by connecting the balance tap to the balance port.

With all that said, the BC-6 and 1010C are working the same, working properly, and at the smaller charge rates they would work identical. Hope that helps.

[creightoncarr]

The BC-6 by default has a Time Cut off of 2 hours. You can very easily change this setting in the User Setup. You can change the time higher or lower as well as Null the feature. That is why the BC-6 timed out.

If there is an imbalance the BC-6 will balance the pack but it will take longer. Same goes for the 1010 with balancer.

I can tell you that if you charged at 1C and it took longer than 2 hours (charger time out) you have a imbalance in the pack.

With all that said, the BC-6 and 1010C are working the same, working properly, and at the smaller charge rates they would work identical. Hope that helps.

Evan, Thanks for the reply. I increased the charger time out to three hours. The second pack noted in my post above started with two cells at 3.93v and one at 3.88v, a slight imbalance. At 37 minutes, all cells read 4.20 volts and the charger entered the CV phase. After nearly two more hours (154 minutes total) the charge had not completed. During the last 2 hours only ~150 mAh were added. Is this possibly a problem with the BC6 or does this suggest a problem with a cell in the pack? I don't have the USB cable or software - if I did would I be able to see what was being bled off of cells during the charge process to keep them in balance?

[RC Accessory]

I think that is suggests an issue with the pack. I will see if I can recreate such an issue myself on a BC-6 with my test packs. Part of how cc/cv works has to do with the resistence of the pack and wiring and as well as the impedance of the pack.

Have you tried other packs, one that you know is 100% good or new?

[creightoncarr]

I think that is suggests an issue with the pack. I will see if I can recreate such an issue myself on a BC-6 with my test packs. Part of how cc/cv works has to do with the resistence of the pack and wiring and as well as the impedance of the pack.

Have you tried other packs, one that you know is 100% good or new?

The tested pack (TP Extreme 3S 2200) is brand new, and only has about five cycles on it. I will try another pack this evening which I know charges and balances fine on the Triton/Equinox. Re: the USB cable and software, if there was a problem with the pack, would the data plots help me pinpoint the problem?

[RC Accessory]

The software would allow you to see the cell voltages through out the whole charge. You would slide the mouse in the cell voltage graph and the voltages would display for that moment in time.

[creightoncarr]

Certainly seems odd.

300mAh/min is 18A, seems way too high for hovering although I have never measured mine on 13t/3000+rpm. Is your motor/ESC/battery hot ?



I swapped to the 11T pinion, used a less aggressive throttle curve with more pitch and the draw and the battery was reduced from 300 mAh/minute to 225 mAh/minute. Even at 225 mAh/minute, on a 2200mAh pack I would get less than 8 minutes of hover time. Is the 430L motor extremely inefficient? Plus, I gotta say, even for my backyard flying with this bird, I don't like the lower headspeed. I prefer a much more aggressive throttle curve, even in normal mode, and a HS around 2700-2800rpm. What kind of power consumption are others getting running around that HS with the stock 430L motor and Align 35A speed controller?

[kgfly]

With Trex450SE/430L/11t at about 2600rpm I easily get 7:30 hovering or 8:00 FF with ~1800mAh consumed and batt/esc/motor just warm to touch. So that is about the 225mAh/minute level. At 2800rpm I would not be suprised to say the flight time fall back a bit so I guess 6min makes sense.

The 430L is not especially inefficient but there are more efficient motors. Take a look at the 3S motor tests on trextuning.com for a comprehensive analysis.

[creightoncarr]

With Trex450SE/430L/11t at about 2600rpm I easily get 7:30 hovering or 8:00 FF with ~1800mAh consumed and batt/esc/motor just warm to touch. So that is about the 225mAh/minute level. At 2800rpm I would not be suprised to say the flight time fall back a bit so I guess 6min makes sense.

The 430L is not especially inefficient but there are more efficient motors. Take a look at the 3S motor tests on trextuning.com for a comprehensive analysis.

Thanks for the reply. I'll check out trextuning.com.

I tried out the fast charge on the BC6 this evening at an initial 1C rate. Where a full charge was taking approximately 95 minutes for 1200mAh, a fast charge takes about 35 minutes and puts back in approximately 1120 mAh on a TP 2200 3SX, or just over 95% capacity.

I've read posts re: charging the TP packs up to 3C with no degradation in cycle life. Anyone been charging at more than 1C?

[kgfly]

Charging above 1C shouldn't be done without an inline balancer that can terminate the charge if any one cell runs too far ahead of the rest. It can also be wise to use a temperature probe to terminate the charge if the battery starts to overheat.

I am skeptical of the claims that charging over 1C has no affect on cycle life but would certainly be very interested to hear of users' experiences.

[RC Accessory]

I just confirmed this with Bantam.

When using the FAST charge program, if you connect the balance tap to the balance port, the cells are balance charging.

This is not documented in the manual! Now you can FAST charge and balance your cells quickly and get 95% charge capacity in a short period of time.

[creightoncarr]

I just confirmed this with Bantam.

When using the FAST charge program, if you connect the balance tap to the balance port, the cells are balance charging.

This is not documented in the manual! Now you can FAST charge and balance your cells quickly and get 95% charge capacity in a short period of time.

That's great to know. I've been averaging about 29 minutes for a fast charge and getting close to a 96% full charge each time.

[kgfly]

Evan, can you confirm for the BC5, BC6 and BC8 that in all LiPo charge programs, if the balancer cannot keep up and any one cell rises over 4.2V the charge cycle will automatically halted ? The manuals seem unclear on this to me.

[RC Accessory]

That is correct. The manual states that if any one cell during the balance program acts abnormally, the program is shut down. Also in normal mode, if the pack is over the 4.2V per cell it will shut down.

[kgfly]

Great, thank you.