Battery basics

[Flydigital]

I've read a number of threads with do's and dont's for LiPo but still have a few questions...

I have a brand new 4S 5C battery. When I plug it into a charger it says 1: 50%, 2: 44%, 3:56%, 4:61%
I assume this is the current storage of the battery and is in a middle 'storage' level.

So do I have to 'discharge' first. Just use it as is or charge it up to 100%

As for discharging, there seems to be all sorts of techy ways to do it involving rigging up circuits connected to light bulbs etc. All very confusing and no one saying what the standard simple approach is!

Can anyone offer the idiots guide to the above?!

Many thanks

 

[Flydigital]

UPDATE:
re: discharging…found this gadget. Is this the solution for the discharge routine?
http://www.ebay.co.uk/itm/3-in-1-RC..._Measurement_Equipment_ET&hash=item20d3f80fa7

 

[Bartman]

UPDATE:
re: discharging…found this gadget. Is this the solution for the discharge routine?
http://www.ebay.co.uk/itm/3-in-1-RC..._Measurement_Equipment_ET&hash=item20d3f80fa7

a lot of battery chargers have discharge cycles built into them but they are very slow so they are impractical for larger packs. that's why you see custom discharge set-ups using light bulbs and stuff. they're more to take an unused fully charged pack back to a storage charge level of about 3.7 volts per cell.

your new pack should be fine for a charge without any discharge beforehand but keep an eye on the individual cell voltages to make sure your charger is bringing them all to an equal voltage as it's charging the pack. Also, don't expect full flight times until the pack has been charged and discharged a half dozen or so times.

that little discharge device might work ok if you only have a few packs but to discharge a bunch of packs it could take a while unless you buy a few of them.

Bart

 

[COMike93yj]

From one "idiot" to another.....LOL.....I joke Flydigital.....

I was in the VERY SAME boat and still don't know all the in's and out's of batteries....I am STILL learning. Can you tell us what charger you are using? That might help the experts assist you more.

Bart is correct in what he is saying. He also made a really good tutorial on LiPo batteries that I still refer to......------> http://www.multirotorforums.com/showthread.php?12819-Understanding-Lithium-Polymer-batteries

I fly my little Nano QX quad all the time for practice so that when I get my 450 built I should be ahead of the power curve. It has 1s 160 to 180 mAh batteries that I charge with the little USB charger. I use a multimeter to check the cel voltage when I am done flying. I do my BEST to keep the charges at the "storage charge" to get into a good habit of taking care of my batteries. Batteries are EXPENSIVE and are the "heart" of your multirotor so keeping them as healthy as they can be is something I strive to do.

There are some people that use the "lightbulb" devices to bring a battery into its "storage state".....I don't do this yet but I may in the future. You can accomplish the SAME thing by flying your batteries in your aircraft. Might as well have some fun while getting them ready for storage! I have my little NanoQX down to a science and with the way I fly, I can fly it for 4.5 minutes and the batteries all are at 3.75-3.8v.....good enough for me to put them away.

 

[Flydigital]

Thanks guys, yes I read Bart's excellent thread on this and will read again so it can sink in a bit more.
At the moment I have 2 hefty looking bricks - 4S 5000mah 30c. The discharging gadget is only £7 so will give it a try.
Re: Flying to discharge. That's really what I intend to be doing! But saying that I had assumed that once flown to a point that the multicopter has to land then are the batteries at that point not already at a suitable storage level?
So COMike, are you saying you fly to point at which the craft could still continue to fly but you stop at what is an optimum point for storage?

My charger is a Turnigy 420 allowing charging of 2,3 or 4 cell combinations. It gives readouts of each cell in percentage terms. I flew the with the new battery as it was out of the box and got a few minutes of charge off it. When I did a volt meter reading it was around 9-10 volts I think but on the charger it read all cells as 0%. I assume the 0% is reading capacitance even though voltage is still there. My physics is poor on this (it's been about 25 years since my last Physics lesson!)

 

[COMike93yj]

Fly,

You hit the NAIL ON THE HEAD!!!!

I fly the little NanoQX on my last flights of the day/afternoon and I do NOT fly them to their full potential. AKA....I land them at 4.5 min of flying time. I could get another 2 min or so out of them and still be well within the "safe" range...aka not hitting the low voltage cutoff (LVC).

SO what I have done is to fly the little batteries and then after many flights determined where the flying time EQUALS the storage charge. Does this make sense?

This way I can still fly and have fun but when I am wrapping up my practices, I simply fly all the batteries at 4.5 min in my case so that I KNOW they are at storage charge.

This can be done with bigger packs and takes some experimenting but it keeps me flying (my goal) and when I wrap up my sessions I am done. NOTE: I always check the packs with the multimeter to see just what the remaining charge is but it works for me.

I am not familiar with the Turnigy 420 but some folks may be able to help. For what it is worth, I DONT trust percentages on a charger. I just don't. I trust what the multimeter says and I go with that.

I hope that helps....trust me I am still trying to learn all the in's and out's of chargers but my multimeter has never failed me and KNOCK ON WOOD I have never had a battery puff or ignite.

Mike

 

[Carapau]

Ref using the last flight of the day to get to storage voltage- personally I make full use of the flight as more stick time is only a good thing. Remember that putting charge INTO the battery to get to the storage voltage is a lot quicker than taking charge OUT of the battery. Of course, if time is tight, then only doing a half flight is a great way to quickly get to storage voltage

 

[Flydigital]

Really useful info thank you.
So the basics as I understand them are:
Charge battery, making sure each cell goes no go greater than 4.2v (chargers are supposed cut off at this rate)
Start flying. Don't drain below 3.3v
Top up to 3.7v for optimum storage or discharge to that level if batteries not used.

One question: I have to charge while supervising for safety. If I need to go out, can I stop and resume or does that damage batteries?

 

[jbrumberg]

I generally rest the batteries for a few minutes after charging them to let them cool down. I, like mike, also fly my batteries down to a ~storage charge which still is around 6 minutes of mixed flight with my 600mAh batteries and my X1's.

 

[Carapau]

You can happily stop a charge mid way through without causing any ill effect. Ideally you should not discharge to 3.3 v per cell. Better off to discharge to 3.7v per cell in use as this will be approx 80% of the batteries capacity. Storage v is about 3.8-3.9v per cell.

 

[Flydigital]

That's good to know. You say it can be run down to 80%. 80% of 4.2v (the max) is 3.36v (nearly in the 'too low' zone.) I notice on the NAZA control panel via PC that their presets for Second level protection - i.e. 'Shutdown' is 3.7v which is the same as your recommendation. The reason I'm asking is if it can go a bit lower than 3.7 and still fly then that means more flight time.
I'm yet to see this all working in the real world but will do some tentative flying this weekend hopefully. Maybe I'll understand the figure better with experience flying!

 

[CrashMaster]

I run all my lipos down to 3.4v per cell to kick the DJI WKM first stage starts to warn me by entering return home. I also have a Lipo Alarm set to 3.3v per cell. My machine draws about 0.5v per cell under load so when the DJI setting starts the RTH I have 3.9v left - well within safe limits. I can then either let it return and land or take over by flicking GPS to Atti and back to GPS I then have control my self and can carry on flying for another 2 minutes.

The reason I have it set up this way is that the voltage drop while flying fast or in wind is far higher but in hover is only 0.5v. This means that the DJI kicks in too early but allows me time to either let it return or take over fly more efficiently to finish the job and slowly return manually. (My iOSD suggests that if flying in Atti mode and fast into a 15mph wind the draw is almost 0.7v or 0.8v)

 

[Carapau]

You say it can be run down to 80%. 80% of 4.2v (the max) is 3.36v

No, you can use 80% of the batteries capacity ie for a 10,000mAh battery you can use up to 8,000mAh which normally brings the battery cell voltage to 3.7ish volts. Lipos do not discharge in a linear fashion. They are fully charged at 4.2v a cell and pretty much empty at 3.2v per cell.

When you recharge your battery note how many mAh it puts back into the battery. Tie this into how long that battery was flown for and you can work out how many mAh per minute your aircraft uses and hence the flight time you can achieve by using 80% of your pack.

 

[CrashMaster]

Carapau,
That is fine if doing consistent flying but sitting in a hover in light or no wind the draw is far less than flying flat out or in heavy wind. However, as a safe mark I would advise everyone to invest in a Lipo alarm. This can be set to whatever voltage per cell you want the alarm to go off at. The problem with Flight Controller settings is that they take to total voltage delivered and not the per cell voltage:- this could mean you have one cell delivering below the safe voltage while the others are higher. This could result in damaging your cells or even causing a fire. The alarm removes this risk going off at the set voltage for the lowest cell matching the setting you make. This also means time never comes into it and is all to do with individual cell voltage.

 

[Flydigital]

Alarm sounds useful. Is that a device with audible alarm that sits on the aircraft or is the data fed back to the transmitter somehow?

 

[Carapau]

However, as a safe mark I would advise everyone to invest in a Lipo alarm

Couldn't agree more. The optimum mix I feel is use the timer to get you into the 80% ish zone and the alarm as your final warning so to speak.

That is fine if doing consistent flying but sitting in a hover in light or no wind the draw is far less than flying flat out or in heavy wind

I agree with this too, to a point. It depends on why you are flying to a certain extent. For fun and FPV this is certainly the cast but for AP I find the wind plays very little difference. I have been flying in winds in the 15-20mph mark on my Octo and there is not a great deal of difference in mAhs I have to put in after a 10 min flight v doing the same on a windless day. Sure there is a touch more but not a great deal. The reason why it is different in AP is that the flying style has to be smooth and consistent not just during a flight but from one flight to the next.

The best solution of the lot is get a mAh used sensor and then you can forget about timers and to an extent, low battery alarms altogether and you just fly until you reach 80%. With my single rotors my mAh sensor means I average about a 4- 4.5 min flight if doing 3D but near 6.5 minutes if doing gentle sport flying

 

[CrashMaster]

Alarm sounds useful. Is that a device with audible alarm that sits on the aircraft or is the data fed back to the transmitter somehow?

That is exactly right it plugs into your balance lead and cycles through each cell and total voltage. You set the desired voltage per cell and when any cell drops to that voltage it goes off with a piercing squeal audible for at least 500 feet.
I use this one http://www.amazon.co.uk/Battery-Tes...TF8&qid=1389389698&sr=8-1&keywords=Lipo+Alarm

Carapau I think we talk from the same hymn sheet. Although I monitor flight time only with a trigger on the throttle on the TX so when it goes over 20% the clock starts counting down to zero from 16 mins. An alarm starts to go off at zero. The reason for 16 mins is that I can get 17 to 19 mins flight from a pack of 8000mah lipos so have plenty of warning. The alarm on the TX is not very intrusive having set the alarm quite low. The next to go off will be the RTH set in the FC which shows up on the iOSD and I can see the craft suddenly ignoring my input, then when I know I really must return and land is when the lipo alarm kicks off. However, by that time I have had two warnings so if I were daft enough to ignore them all I deserve to crash. Oh and by the way my rig is set up for AP too so safety of my rig and camera is paramount - time out of the sky is lost money for me. Even more so as I am going to sling an NEX-7 up there with it as soon as I have the gimbal sorted so can use zoom in flight. Just now I just use a GoPro H3 Black.