TP G8 Pro Lite packs - draw down limit?

[Dennis Toth]

Guys,
Looking at the Thunder Power ads for the new G8 packs seems to indicate that they carry 10% more capacity for the same size as the old packs. As I see it the only way they can do this is to allow the pack to be drawn down to say 90% instead of 80%. They don't give a lot of details about this new chemistry and what makes it so good but if you can go to 90% without damage to the life of the pack that's a big plus. Anyone have the full details on these packs?

My problem has been needing just a little more from the packs then they have in the available size ranges for the weight I can carry. It's like needing a 3 3/4 oz tank and only having a 3 1/2oz one that fits the ship. I've been working with different prop sizes to adjust the load but would really like to have just that 10% more from the same size and weight pack.

Best,      DennisT

[William DeMauro]

Dennis,
 My suggestion would be to look over on RCGroups and look in the battery and charger section Those guys usually get that stuff first and have the scoop on them way before we do.
William

[Dennis Toth]

I checked the RC sites and they don't have a clue about discharge limits. I can't believe that no one on this site has compared the G8 and G6 packs to see if we can drawdown more than 75%. Seems from the info on the TP website we should need less head room. Someone has a connection with TP should be able to get details. Dean, Kim, Bob, Mike?

Best,  DennisT

[Alan Resinger]

Hi Dennis,
I have been using the TP G-8 batteries since they first came out.  When I fist started using them I was using the APC 13" prop with an E-flite 32.  My usual draw on the batteries was between 1800 and 1900 on the 5S 2700 mAh packs.  After Chris Cox and I started making 3B CF props last summer, my current draw moved quite a way up.  During cooler weather, I sometimes draw as much as 2350-2400 mAh, which is a bit over 80%.  Paul Walker and I were talking about the amount of current draw we were experiencing.  Paul said that all last year using the 5S battery, he was using in the 2400 range.  On his new "Predator" he switched to the 6S to help with the problem.  Right now I have 3 of the batteries from last year that have over 100 charge cycles and they are still going strong.  I also have 4 newer batteries with around 20 cycles and just ordered 2 more today for contest flights for the rest of this year.
The G-8 seems to be able to handle the additional draw without damage.  I know I'm taxing my batteries but I just don't want to add the additional weight that a 6S would present.  I just figure it's the cost of competing.
Alan Resinger 

[Mike Haverly]

They seem to be pretty tough.  I accidently double ran one of mine, of course, it quit real soon.  When I charged it, it took 2770 mAh to bring it back up.  Not bad for a 2700 battery.  I know which one it is and I'm watching it.  So far no problems, in fact, it went through an official this past weekend.

[Kim Doherty]

Guys,
Looking at the Thunder Power ads for the new G8 packs seems to indicate that they carry 10% more capacity for the same size as the old packs. As I see it the only way they can do this is to allow the pack to be drawn down to say 90% instead of 80%. They don't give a lot of details about this new chemistry and what makes it so good but if you can go to 90% without damage to the life of the pack that's a big plus. Anyone have the full details on these packs?

My problem has been needing just a little more from the packs then they have in the available size ranges for the weight I can carry. It's like needing a 3 3/4 oz tank and only having a 3 1/2oz one that fits the ship. I've been working with different prop sizes to adjust the load but would really like to have just that 10% more from the same size and weight pack.

Best,      DennisT

Dennis,

The lowest suggested voltage for TP G8 Pro Lite 25C packs is 3.3V per cell under load. How you get to that 3.3 volts per cell is your business. There is no magical extra 10%. If you are having a problem matching battery voltage and capacity to a particular model you are either not calculating the requirements starting with the aircraft weight and desired performance level or you are using an incorrect propeller/rpm. Assuming a TP Pro Lite 2700 mAh 5S pack and a model weighing somewhere around 60 ounces, you should have no trouble achieving a running time of 5:45 to 6:15. (plenty of time for a full pattern)

You will note that 3.3 volts per cell is the suggested Low Voltage Cutoff minimum and is also ~ 80% of fully charged voltage. (4.2 volts per cell)

The life of your battery will be shortened by deeply discharging it repetitively (never deep discharge in the first few runs !!) So if you have deep pockets or you just can not use another setup then the cost is only fewer flights and more money. 

Kim.

[Dennis Toth]

Kim,
Thanks for the information. I called TP and they indicated that although the G8 packs are more efferent at getting power out they still need to have the cells at a minimum voltage for recharge and maximum life. This pretty much means keep 20% in the tank.

My setup seems to draw more amps then what I've seen others using on a similar setup. I'm starting to wonder if my approach is causing higher amp use. My ship is 62 oz complete with battery, Hacker A30-10XL V2 motor, TP 4S-3300 pack, turning an APCE 11x5.5P @9550 rpm. I have a Castle Creation 45, set in control line mode; fixed rpm, with all other settings set to conservative setting. I set all three levels to the same rpm and let the ESC control the rpm. I use an old Zetron timer set to 100% for all level, 20 sec start delay, run time set for 5min, 20 sec. Ground test shows 35amps. With this I have been pulling out  around 2700 mah. Most others I've seen posted are pulling around 2200 - 2300 mah.

Could using the ESC to control rpm be hurting the amp draw vs using say the FM9 time to control it?

Best,     DennisT

[Robertc]

Also note that Dennis is flying at near sea level.  Going from Dallas to Albuquerque, I used about 250mah less.  I'm flying the same set up but APC 12 x 6 and am using
about 2400 at sea level @ 8900 rpm.

[Dennis Toth]

Talking to the tech people at Castle he indicated that we might benefit from using 50C - 70C batteries in our application. The reason given was that there is a significant chemistry change with the high C ratings that provides a flatter discharge curve and could allow us to use a smaller pack size for the same run time. Looking at the various packs available there are some that are very close in weight to the 28C Pro Lites. Anyone look at this?

Best,        DennisT