Battery Sag

[coyote_dc5]

I'm seeing a wild read out on my OSD with voltage. It's up and down like crazy although i don't feel it on flight. I have witnessed sag when I push the cells beyond their C rating but readings are irratic even under normal flying conditions.

I've got a mixture of Emax 1 and 2S and some GNB and Tattu cells but the issues are exhibited on all so I'm not convinced its the battery choice and the issue is elsewhere

The drone is a TH2 using the factory PH2 connector and here is some footage

 

[HighTechPauper]

Looks pretty normal to me, it isn't just a matter of sag, a battery under load will dive pretty quick especially during hard throttle and then recover a bit when you back off.

 

[coyote_dc5]

Ok thats reassuring, thanks for responding.

 

[HighTechPauper]

One other thing to keep in mind is that PH2 connectors have a very short life comparatively to their BT2.0, XT30, XT60, XT90 cousins even if they are solid pin instead of folded pin design, but solid pin design holds up much better than folded. Both the batteries and the quad connectors performance can degrade fairly quickly, you can put a new pigtail or connector on the quad side, the batteries though are not feasible to change out. For this reason I try to not plug in any more than needed, like constantly putting them on the 1s battery checker, since these connectors wear quickly (female sockets spread out). This is also a big factor in the sag your seeing, but the performance of 1s connectors and 1s batteries on these relatively high performance small quads like the TH series is what it is.

 

[HighTechPauper]

BTW, my TH2 has folded pin, yours likely does too, you can get better performance if you swap it out for a solid pin connector.

 

[coyote_dc5]

Yes I did read that somewhere. When I upgrade my usb chargers to a proper hobbygrade I'll butcher the ph2 sockets from that and solder on

 

[Primoz_Horvath]

What do you mean with this?: " I have witnessed sag when I push the cells beyond their C rating ".
What or how much is the C rating?

 

[tevek]

What do you mean with this?: " I have witnessed sag when I push the cells beyond their C rating ".
What or how much is the C rating?

Since you can’t see the amps being drawn on the screen, I’m assuming the OP is referring to the drop/sag in voltage during punch outs, flips etc. The C rating refers to the continuous discharge rate. Multiply that number by the battery capacity and that is the maximum current draw of the battery.

 

[graywoulf]

I too see the same thing with my TH2's batteries. To me, I don't see any more flight time with a 2S battery than withe a 1S battery. All of my batteries and the quad have the PH2 connectors on them. I wish there was an XT15 connector for the tiny whoops.

 

[L0stB1t]

If the constant warnings bother you, you may want to set a small delay in Betaflight. I have set the following:

set vbat_duration_for_warning = 20
set vbat_duration_for_critical = 5

This means the voltage has to be below the warning voltage for 2 seconds before the warning is shown, and half a second below the critical voltage before the "land now" message is shown. This way I don't get unnecessary warnings during a punch out in the middle of my flights anymore, only when the battery is nearly empty. Keep the values low in order not to kill your batteries, I'd say 3 seconds is the absolute maximum anyone would need.

 

[coyote_dc5]

That's great advise, appreciated

 

[HighTechPauper]

I too see the same thing with my TH2's batteries. To me, I don't see any more flight time with a 2S battery than withe a 1S battery. All of my batteries and the quad have the PH2 connectors on them. I wish there was an XT15 connector for the tiny whoops.

If you could get a battery with 2 times the mah and keep the same weight, or 2 times the cells and keep the same weight you could get a longer flight time, but as cells go up and mah go up they get heavier and that reduces the flight time. This ratio between weight and mah of a battery is at the point of diminishing return, heavier battery, harder to lift and fly with agility, lighter battery, easier to lift and fly with agility, it is always a balancing game. I could put a 5,000 mah battery on my 5" quad and actually lift it, I could fly for 15 minutes, but it would be a slow and lumbering pig compared to the same quad with a 1,300 mah battery. They did try to make an "XT15" like connector for small micros, they are called BT2.0 made by BetFPV, but they too have issues and are not doing well. Most have found that solid pin PH2.0 connectors along with one size larger gauge wire on the pigtail makes all the difference in performance.

 

[graywoulf]

I was wondering if a regular red JST connector or a Deans connector would be a viable replacement.

 

[HighTechPauper]

I was wondering if a regular red JST connector or a Deans connector would be a viable replacement.

Red JST isn't really any better than PH2.0 for connector surface area and current carrying ability, and Deans (or T-Plug as they are often called) are way too big and heavy, might as well use XT30's at that point since they are smaller and lighter than Deans connectors.

 

[coyote_dc5]

Because I've got heaps of LIPOs with the PH2 i think the best route here is just to go thicker gauge on the FC bigtail and go solid pins so thanks for everyone's input. I'll find some time to do this on the bench in the next couple of weeks

 

[Deleted member 3641]

For those wanting to get the most from the TH, I stumbled across these two vids awhile back...

 

[Deleted member 3641]

I too see the same thing with my TH2's batteries. To me, I don't see any more flight time with a 2S battery than withe a 1S battery. All of my batteries and the quad have the PH2 connectors on them. I wish there was an XT15 connector for the tiny whoops.

BetaFPV has a new tiny connector out that supplies twice the amperage of the PH2.0 connector.
BetaFPV BT2.0 1S Whoop Connector Male/Female Set 5 Pack

 

[graywoulf]

BetaFPV has a new tiny connector out that supplies twice the amperage of the PH2.0 connector.
BetaFPV BT2.0 1S Whoop Connector Male/Female Set 5 Pack

I am considering converting over to those connectors. Seems like a lot of work but worth it. There are mixed reviews on them but I think they look more solid myself. The other thing is that I am going to need a lot of the adapters to charge the batteries on my multi charger as well. Thanks for the link to those.

 

[Deleted member 3641]

There are mixed reviews on them but I think they look more solid myself.

I have come to trust JB's info and he did a proper test to show the results.

I have a 6 port 1s charger myself so I will need half a dozen adapter cables.
I almost bought a TinyHawk 2 yesterday, and if I do, I will use these connectors.

 

[graywoulf]

I had watched that video a couple of times myself. However, speaking of the Tinyhawk II, I was following JB's video on installing the popular "Project Mockingbird" PID's in it a while ago and I think it bricked my FC. When it is connected to Betaflight it says it is connected but there are no lights on the FC as there usually is. I tried connecting a battery and it lights up for the first part of the beep tones but when it should give the last two tones, it stops beeping and goes dark. It does not connect to my Tx as well. So, I am at a loss on how to fix this. I tried rolling it back to a different setup but that didn't help and doing a reset in BF didn't help either. Bummer.