BK warrior 9920 Has Lipo protection?

[Demon-TC3]

Hi all,
i contacted BK a few days ago to see if they can either part exchange me a bk 9920 with lipo cutoff or if they could give some advice on running a BK 9920 on a lipo and the responce i got was...strange.


APPARENTLY, the BK warrior 9920 HAS a low voltage warning set for 4s use - when the voltage gets too low the BK limits throttle to about 30 - 40%, this is the email i got:

the warrior series had a automatic cut off..by 2,72 volt......but for different cells is this to low......but

by 3,0 voltage.,...the controller going down approx. 30-40 % for his power.....and you see defenitly
than in the moment is 3,0 voltage....

i hope you understand me ?

i asked if he could elaborate on what he meant ans asked if the warrior has a lipo protection:

yes...you see ..when you drive....when the power going 30-40 % down...you see that is 3,0 voltage



SO, can anyone confirm? i have been running 14NIMH cells and at the VERY end of the pack it does seem to SUDDENLY get low, also i ran 12NIMH cells yesterday and it seemed the difference between wheelies on command and sluggish was a single lap - since 12 nimh cells and 4s lipo (supposably what the LVC is set to on the 9920) are similar voltage it would indicate that they are right....


Let me know what you think,
Demon

[Demon-TC3]

Anyone out there? someone must know?

[ElectricThunder]

Maybe it does have a cutoff, but it's a "soft" cutoff? This behavior is what I've experienced with my MM set to 3.2v per cell. It seems to soften up and power drops off rapidly. I wonder if I do really hit cutoff, or if the pack just dumps though...:confused:

[GSMnow]

I set my Mamba Max to cut off at 6.2 volts for my 2S packs. It will not make a lap on my 6 cell NiMh packs. With the Max Amps 2S 3000HV LiPo's though, it runs very strong, no hint of any power limiting at all until it goes real soft. And from the first hint of slowing until it stops dead, it is less than a lap. The reall odd thing is how different the LiPo's act from the NiXx packs. Withthe NiXx's I can let off the throttle and ease in and drive it for a couple minutes. Pull hard and it stops, and you can keep rolling in and get it around the track. With the LiPo, it just STOPS. If you let off and wait a while, you can roll in very light and maybe get a few feet until it just parks again. I could not make 1/4 lap after the cutoff stopped it. After a couple minutes (walking back to my pit and pulling the pack) I measured the voltage on the pack and it was at 6.6 volts. I put the pack on charge and it took 3175 mah to top it up according to the readout on the TC-1030 charger. Not bad for a 3000 mah pack. Just as a test, I had to try it once. After it hit cutoff at 6.2 volts and stopped cold, I set the cutoff down to 6.0 volts. It had strong torque again and pulled hard for almost a lap, and then stopped dead again. I would not be surprized if the cells will keep pulling just fine down to well below 3.0 volts per cell, and that is the real danger. If you don't have a low voltage warning, they will keep putting out strong current to well below the point where the cells are destroying themselves. DON'T RUN WITHOUT A LOW VOLTAGE CUTOFF! When you notice it running any slower, the cells are already being damaged. I like the idea of a 2 stage cutoff. It would be nice if you could set a voltage where it limits throttle as a big warning, but it has enough to let you make at least a full lap before the full cut kicks in. When I am practicing and run my packs to cutoff, it get's hairy when it stops at the end of the straight and a truggy is coming at 40+ mph.

[Demon-TC3]

thats the thing though, im not sure if the guys at BK are implying that the cells themself will be so low that it gets slow or that there is a soft cutoff. i really am stumped! i will wait till i gete my 4s lipo monitors (dont do anything for control but just monitor pack voltage and balance) and see what happens when it does slow and what voltage is at.


Take care,
Demon

[Mr. Constructor]

The BK Esc´s are programmed to Cut of at 0,9 Volt´s per Nixx cell, this implicates (and has functioned in my 1:8 Buggies) that the Cut-of Voltage for Lixx Cells is at 2,7 Volt´s per Cell. The use of Li-Fe-Po4 Cells (such as the A123) is NOT recommended by these esc´s and will lead to a much earlier cutoff.

But i can definately say that there s a new esc series planned and this should be launched earlier this year. I will get a test sample within the next 1-3 weeks and see how they perform. The overall concept - special metallic housing, PC or Prog-Box, many parameters to setup and minimum 4 types of Amp ratings (70, 100, 150 and 200A) are the way to look at !
(Sorry that i cannot say any more more but i gave them my word - wich i would not break!)

I will inform you all what these new esc´s are all about, my first "test-objects" would be the 70 and the 150A Version.

[Demon-TC3]

Hi bud,
If it is 0.9v/ Nixx cell then isnt that 2.7v/ lithium cell? if so, isnt that too low? i thought lithium was 3.0v / cell cutoff.

can you give me more details on the cutoff, i just dont understand how it works with Lipo cells. is it pre-set for 14 cells or does it automatically detect the Number of cells?


is the cutoff a total cutoff or a soft cutoff that limits throttle?


thanks.
Demon

[GSMnow]

Could you set ot to cutoff at 14 cells? That would be 12.6 volts or 3.15 per LiPo cell.

[Mr. Constructor]

Sorry for the mismatch with the 2,7 Volt above, you´re right and i slightly changed it in my post - so that nobody other will get confused.

As for the Cutoff, it uses the voltage and the inner resistance of any battery to try to "count" the number of cells (the more cellsthe more inner resistance it will be) and uses some given values to check these taken Numbers back (sort of a "List" with some variables in it.
The software now does check the voltage too, if this is within the given cell count (that value will be checked together with the one out of the resistance) and then the battery cells are selected.
The cell cutoff voltage of 2,7V per Lipo Cell is always measured under load, therefore it is OK as the cells manufacturers quote that their cells could be used down to 2,5 Volt/cell. Please have this checked if you´re NOT using one of the major brands of Lipos (Kokam, Eagle Picher/Polyquest, Maxamps, Saehan)

Normally the Cutoff Voltage has to be between 2,7 and 3 Volt´s, the use of the lower value doesn´t mean that the battery will get destroyed, the only thing that might come into trouble is the internal BEC of a esc if only a 2S Lipo Battery is used. The Voltage might be too low to feed the BEC permenently and the esc will shut of due to this reason only.

Normally the BK controllers will shut of slightly hard, not fully into the brakes, but the Motor will be reved down within some seconds - but normally (if the Voltage gets below 3 Volt) the driver recognises this fall down rapidly, therefore a little extra "listening-to-the-power" cannot be very wrong.

I will soon show a How-to for making your own customized battery housings to create a hardcase lipo out of any lipo battery back, i will post the pictures and everything else soon here in the forum - i will add the link here too when everything is done.

Here it is:

http://forums.radiocontrolzone.com/showthread.php?p=2330882&posted=1#post2330882

[Demon-TC3]

Mr constructor thanks very much for your help, its greatly appreciated.

So far BK has been an excellent company to me and i appreciate the customer service they have given me - although i must say, the english is sometimes a little difficult to understand (and im even living in the UK :P )

by the way, did BK ever release updated softwares for the 9920? if so how is it possible to update the software on the 9920?


thanks.
Demon

[Mr. Constructor]

The BK 9920 Controller could be updated but only in the Factory.
As far as i know there are no updates out yet, the new ESC Line (soon to be released) will have the opportunity to update the firmware by yourself via a download.

This feature was implemented into the ESC´s circuit board, but it isn´t released the same time the esc´s come out - it will come, but a little later on.

[porra]

The BK 9920 Controller could be updated but only in the Factory.
As far as i know there are no updates out yet, the new ESC Line (soon to be released) will have the opportunity to update the firmware by yourself via a download.

This feature was implemented into the ESC´s circuit board, but it isn´t released the same time the esc´s come out - it will come, but a little later on.

Mr. C,

Do you know when the new controllers will be available? I contacted Barbara and she didn't reply back.

[Mr. Constructor]

There are a few last changes on the esc design, normally i would get the first samples till end of april, maybe begin of may.

The shops could get them a little later on, but i think it will not be that long.
Of course you could also get them from me, i ordered a few ones too.
(the 150A Version seems to be the ideal ESC for both (Buggys and Truggys) cars to power up a good Electric Car.

Prices for the 150A Version are around 150-160 Euro !!!
(But without Prog-Box or PC Connection as these Items will be released later on)

[porra]

Do you have pictures of the controller?

[rccardude04]

If you're still trying to interpret the Engrish...
The way I understand it is that it drops you to 40% throttle at 3.0v/cell just so you can still drive the thing back to you. At 2.7v/cell, it stops entirely.

Personally, I don't like it that low and I still can't understand why manufacturers do that. I always set it +.1v/cell. MM is at 6.2 for a 2s pack.

-Eric

[Demon-TC3]

hey ET - if thats the case it would be ideal. i will need to test it when i can and get back to you all,


take care,
Demon