I am relatively new to flying and have been on a struggling crusade to keep voltage as consistent as possible for more confidence to push the envelope on ballsier moves. 

Doesn't seem like too difficult of a standard, yet I'm surprised. I only fly 4s, and have been using the same fast charger for the past 8 months of my flying career (more like 3 with winter being a stupid brutal thing), yet for some odd reason, one or two of my packs would sit not-quite-fully charged forever, only for me to find out it flies for less than 30 seconds before losing all but negligible flying abilities. Like just enough power to bring it back most of the way to reduce the walk, but any more gas and even the video starts to cut out. Furthermore, the rest of my packs seem to have significantly more voltage sag . I just got OSD abilities a month ago with my new quad setup so it's hard to tell here, but it seems like the sag causes the status to get dangerously close to dead in only a minute of pushing it relatively hard, limiting me to cruising for the other 3 minutes or so just to avoid unexpectedly losing a quad to voltage sag.

I'm not above thinking I may have killed a couple of my LiPos by mistake. I just need to be clear as to why. There's only 2 real possibilities i came up with.

1) I know there is plenty to do in betaflight to prevent fully draining a LiPo fully, which i understand is unsafe and may be one of the reasons for the now struggling LiPos. I just assumed betaflight would have the LiPo-safe settings by default. Probably worth mentioning, I also don't have a beeper at the moment, which i would hope isn't the only safety net between you and a fully fried LiPo.

2) I have a EVPeak E4 fast charger. It is a simple budget friendly single-lipo charger that hit all the dings in my cheap-ass amateur brain. As a result of doing this and charging/flying rather infrequently (no more than 10 times in the past 8 months), I haven't much researched fast charging and when it is necessary to use a balance charger, but i know it's generally healthier to balance when you can. This second possibility would be best case scenario so that hopefully I can restore what I think are dead LiPos and get that voltage sag to appropriately delay itself.

So if it's a matter of fixing something in betaflight, I'm all ears and may need to pick up a couple more packs. 

If there is still a chance a balance charger will resurrect my problematic packs, I will order one ASAP.

I guess the first few questions are:-

1. What brand and capacity of LiPos are you using?
   
2. What voltage are you flying them down to before landing?
   
3. When storing them between flying sessions, are you storage charging them at the 15.2V storage voltage, or are you storing them discharged or fully charged?
   

(10-Jun-2019, 10:37 PM)SnowLeopardFPV Wrote: I guess the first few questions are:-

1. What brand and capacity of LiPos are you using?
   
2. What voltage are you flying them down to before landing?
   
3. When storing them between flying sessions, are you storage charging them at the 15.2V storage voltage, or are you storing them discharged or fully charged?
   

I'm using 3 Goldbat 4s / 1500mAh / 100C. These seem to be the ones that take the longest on the fast charger because i also bought cheaper Gartpot 4s / 1500mAh / 75C packs that give me consistently quicker charge times despite initially performing worse than the Goldbats (assuming because of the 75C rating). Nonetheless I tend to store them charged and seeing if i need to top them off or anything.

I never really was able to keep track of specifics on voltage since I never had OSD until last month and now generally just watch the battery percentage bounce up and down on the OSD until it gets uncomfortable to fly. I have had it die fully in the past where it just dropped from dropping below a threshold for video input. That could be a clue that it's betaflight that needs to tell the quad to quit sooner. Maybe.

I generally keep them charged in my bag. I have had sessions get cut short where i finished a pack or two and had to make a repair or run home to replace a prop cuz I left my wrench at home.  Those were times I may have stored some already drained LiPos.

What also makes things difficult from a numbers perspective, is that my charger doesn't have a readout of any kind, it was just the thing that seemed the easiest to skimp on financially. I'm probably gonna end up buying a decent balance charger whether or not it was to blame for the LiPos getting so weak.

I never heard of Goldbat or Gartpot batteries. I certainly wouldn't believe the 100C or 75C rating from such unknown brand names which are likely just fictitious marketing numbers. Both brands seem to be sold on Amazon marketplace, eBay and AliExpress, but not by any of the reputable online RC hobby stores from what I can see which probably tells you something.

Storing LiPos fully charged all the time is going to kill them prematurely. Likewise with discharged LiPos. They need to be kept at storage charge when not being used. And if you've not been able to keep track of the voltage you've flown them down to then there is a strong likelihood that you have run them down to less than the absolute safe minimum of 12V below which the cells then become permanently damaged. Ideally you should never run a 4S LiPo below 14V which gives a 0.5V safety margin per cell.

So the above reasons are probably why your LiPos have now pretty much had it. From the sound of the state they are in, I would just discharge them all to zero volts and take them to the recycling centre, then get yourself some new ones that are by a reputable brand.

I had a look at that EV Peak E4 charger and it's probably one of the most basic chargers you can get. It has no ability to do storage charging and the charging is done via the balance lead alone and not via the XT60 connector which is quite a poor design. Plus as you say, no proper readout telling you voltages or cell resistance values. You really need to get yourself a proper charger. If you're on a budget then you can't go wrong with one of the SkyRC iMAX B6AC chargers (an original with the SkyRC logo on, not a non-logo'd clone). They are well proven with a rich feature set and are pretty much bullet-proof.

If your quad is dropping out of the sky because of voltage, you took the voltage too low and damaged the lipo. Signs of bad lipo is high internal resistance (your charger doesn't have feature to read this), puffy lipos and severe sag even after a full charge.

Betaflight does not have any thing that prevents you from running the lipos too low. There is warning you can setup for beeper alarm, OSD warning or radio telemetry warning. But if you don't have or bother to pay attention to these things, then it is likely you have damaged most of your packs.

good and healthy lipos make a lot of pleasure. bad lipos destroy flightdynamics, give crashes and in the end time on the workbench. also the „durability“, cycles you can use, or how they get worse depends on the quality. i try to save money,but lipo quality have priority. quality lipo= power, max controll, savety, charging cycles = pleasure
spending time for care the lipos with „storagemode“ is importent for the same points, in the end pleasure at fly.

Thanks so much for the replies and to snowleopardfpv for the very clear explanation. So it's clear I have underestimated LiPo safety. I also didn't realize amazon batteries have such a high potential of fake ratings from manufacturers. I definitely am due for a getfpv cart-full, i obviously have a bias for amazon due to prime despite getfpv having relatively decent shipping as well. I definitely will purchase a proper balance charger and go back to that Bardwell video i recall glazing over on how to parallel charge and get proper storage voltage.

(11-Jun-2019, 12:15 AM)voodoo614 Wrote: If your quad is dropping out of the sky because of voltage, you took the voltage too low and damaged the lipo. Signs of bad lipo is high internal resistance (your charger doesn't have feature to read this), puffy lipos and severe sag even after a full charge.

Betaflight does not have any thing that prevents you from running the lipos too low. There is warning you can setup for beeper alarm, OSD warning or radio telemetry warning. But if you don't have or bother to pay attention to these things, then it is likely you have damaged most of your packs.

It makes sense I haven't had this problem until recently. I just built my quad without the beeper a couple months ago, my first quad was the x220s that had the beeper which i adhered to as soon as it would start going. Sounds like the LiPos I had weren't that great anyway.

Oscar has several good articles on the "care and feeding" of lipo batteries. Well worth a read.

here are a few

https://oscarliang.com/lipo-battery-guide/

https://oscarliang.com/parallel-charging-multiple-lipo/

https://oscarliang.com/when-retire-lipo-battery/

But from your description I think you have damaged your batteries and they need to be replaced.
I would spend a little more for known quality and take good care of them.

Scott