Hello everyone,
I am using these batteries and Foxtech claims max discharge is 2.7 (I guess this is cutoff), but I assume that this low voltage would damage it. Any recommendations on the critical voltage point that I shouldn’t go below?
Also, trying to figure out what should I set in my battery parameters for the following:
BATT_CRT_VOLT
BATT_CRT_MAH
BATT_LOW_VOLT
BATT_LOW_MAH
MOT_BAT_VOLT_MIN
Any help is highly appreciated
Gal
yes with semi solid lipo batteries you can go below 3v per cell but 2.7 is near completely empty and note that how much lower you go in voltage, usage in ampere will increase and its could harmful for a semi solid lipo because C rating in semi solid lipo is lower than normal lipo batteries.
also 2.7 * 6 will be 16.2v at all and its low for a 6s motor , so your drone will be under-powered if its a multi rotor
its hard to say because with more ampere current your voltage will drop soon but you still have capacity to use
i always measure with a current module
for example on my F450 i land on 3.2v per cell but on my Daya 550 i land on 3.5v per cell both drone using same Gens Ace 5500mah 4s
i suggest to start with 3.2v per cell then compare CurrTot with battery capacity
Good advise! I mostly use pack capacity for flight time but I did have a 10C battery that sagged low as it was approaching ~85% of capacity so I used 80% for that one.
Thank you Hosein @hosein_gh and Dave @dkemxr, I totally agree, better safe than sorry.
So until logs are available, crt shall be 3.2 and low 3.6
Much obliged
Gal
EDIT: of course also charger measures
Hey @gnitzan. When I was looking into these batteries I asked for a testing document from Foxtech. The document they sent me included the following graph. Should help with setting the best values.
Wow, that is indeed a low cell voltage at the rated capacity. But I don’t have any experience with this battery chemistry. It occurs to me that if you are going to attempt to fly it down to that pack voltage you may want to lower the MOT_BAT_VOLT_MIN value but again no experience with that.
Thank you @manavgandhi17 when I spoke to them they were not clear so I think I shall follow @hosein_gh and @dkemxr By setting the critical voltage at 3.2 per cell and run a few flights and collect every bit of data I can both from the logs and also of each charge. Than I shall post it here and than we can figure out the correct numbers. I am in no hurry so even if it takes a few days to accumulate enough info that is good for me.
BTW, I use the Mauch PM so I believe the logs will be pretty accurate.
Gal
Dave, for $420 brick it should be…
Using the data that @manavgandhi17 posted you should get ~18Ah at 3.2V/cell which close to where you would want to be anyway (85% of capacity). The data you collect should be interesting!
Definitely agree with all the precautions you guys mention. Definitely think 3.2V (or slightly higher) is a good stopping point until further data is acquired.
My bricks are fully charged, setting already set… fly tomorrow morning 
Hello to all,
So this morning flight went really well 26 minutes to 28%
(log file)
charger reported 15655ma.
What do you think ?
Gal
Looking good! What was your landing voltage and how much sag did you experience?
Hey @gnitzan! Hope all is well. Just wanted to check in and see if you had acquired more data on these batteries. Looking to add them into my current bird sometime in the future and would like to figure out any shortcomings/nuances before placing an order.
Hi Manav @manavgandhi17, it is good to hear from you.
This batteries are awesome! You can see the sag in the image
I am attaching the log of this morning flight where I achieved 30 minutes flight time!
Hope this helps
Gal
Looks like around 1.5V of sag at around 35A draw (around 1.5C). Not too bad.
Our current bird uses 6s 22Ah in series to make a 12s 22Ah pack so I am between purchasing the 30Ah or 22Ah Diamond batteries. One one hand, using 30Ah will keep my bird at the same weight but with an extra 35% of battery capacity (wow) - which is nice because I don’t need to re-tune or anything. However, the batteries are quite a bit more costly. Using 22Ah will result in approx 1kg of weight savings with the same capacity - all at a lower cost as well. Might need to re-tune everything though.
Leaning towards to 30Ah right now just because of the extra range they will give - and I believe I will be drawing at a lower C rate on them (when compared to the 22Ah). But more flip-flopping is needed on my side (as with all decisions) before I pull the trigger.
The price tag on those batteries is steep, no question about that. I do however got my money’s worth to fly a 6.3 kg X8 for 30 minutes with 30% juice left in the brick I can say honestly it is worth it, at least for me and I plan to add 1.1kg more for gimbal and camera (sony a6400).
About re tuning are you sure you would need to? Actually I did all my tuning axis by axis with an 8000mah battery and used the instructions on the advanced tuning instructions math to set the values after.
Gal
You are right that we may not need re-tuning, don’t know exactly how the decrease in weight will effect the bird. We cruise at approximately 30 knots (with plans to increase) and have the WPNAV_ACCEL parameters set to maximum. So we often have to spend time fine-tuning the aircraft for minimal vibrations and overshot. Nonetheless, I can easily take off 1kg of the current payload and see how the bird acts. The emphasis of this aircraft is quick payload delivery or mapping so here is a bit more info about the quadcopter
AUW (w/ 1.5kg Payload): 10.25 kg
Thrust to Weight Ratio (at full charge): 3:1
Batteries: Dual 6s 22Ah Tattu in Series (12s 22Ah)
At our current weight and a cruise speed of 30 knots we draw approximately 1600W - so roughly 35A at nominal pack voltage. At an 85% usage, this allows us to fly 17.5 miles of straight distance before needing to land. Now, if I were to place the 30Ah Diamond onboard with no increase of weight - this would lead to approximately a 30% range increase (so around 22.5 miles). I don’t know what the range increase would be with 22Ah Diamond - but I can test this in house to see what the power draw would be at the lower weight. Either way I would probably be pulling close to 1.1 to 1.4C from the battery - so I assume I would be experiencing a similar voltage drop to you.
