Batteries and Charging

[gregb49]

I'm not an expert on batteries but there have been several comments on this forum regarding charging rates etc and I cannot find any general advice here. I'm more used to Lead acid, NiCads or the newer Nickel Metal Hydrides NiMH, so I did a little investigation and have come up with the following. I hope it is useful and not in error.

My conclusions are:
1) Stick to the supplied charger.
2) Do not overcharge or leave on charge for too long.
3) Try to avoid discharging completely as this will destroy a LiPo cell.
4) Let a battery cool before recharging.

Lithium-Polymer-Batteries LiPo are replacing more traditional NiMH batteries because of lower weight, increased capacity and greater power delivery, but at a cost, not just the higher price. Not only is there a risk of fire when the batteries are not used in accordance with the instructions, but they are easy to destroy through overcharging, charging too fast or over discharging.

An aside.
Sometimes you will see 95c or some such notation. Apparently the C-rate is a measure of the rate at which a battery is being charged or discharged. It is defined as the current through the battery divided by the theoretical current draw under which the battery would deliver its nominal rated capacity in one hour. (Wikip)

 

[holtneil]

 

[gregb49]

Thanks, that was so useful, even for those who only buy a complete drone package as it contains some essential information about looking after LiPo batteries. (I should remember that YouTube has the answer to almost everything.

The 'C' rating (Continuous?) is a new rating to me, put in this form, but an essential rating.
He should say that a 1,000 mAH battery has a capacity of 1,000 mAmps or 1 Amp for an hour. So some of these tiny batteries can supply up to 25C ie 25 Amps continuously, which seems quite amazing. So this in theory, is for 1/25 of an hour ie 2.4 minutes, although no battery should be run completely flat. That will destroy it.

I find his charging instructions technically dubious. He states that LiPos can be charged at the capacity figure ie 1,000 mAH, at 1,000 mAmps and a 5,300 mAH at 5,300 mAmps or 5 Amps. That is probably a safe figure as the higher capacity cells will be larger so can take a geater current, but he should explain that. But he does go on to say that charging at a low figure will prolong the life of the battery. As he says more sensibly, many of these batteries have recommended charging rates on the back. He does another, very informative, video on charging LiPos for those who want more details.

The instructions about storing batteries and why they shouldln't be stored fully charged or fully discharged were also very important. In simple terms, if you are not using your drone for a week or so, don't store the battery fully charged, for both safety and longevity reasons.

 

[LoneRCRanger]

The one thing that impressed me from the video was the 3.8 v storing charge. So, having a score (20) of LiPo batteries, fully charged and stored, makes it sound like I have a bomb waiting to go off in my storage case. So, to be safe, he states that I should discharge each battery until it reads 3.8 v on the watt meter. It doesn't sound safe to have a whole lot of batteries; and a lot of work prepping them to store. Like the old NMHi batteries are safer.

 

[holtneil]

Never store at full they are a fire bomb this is why

 

[holtneil]

And this why we don't leave a lipo while charging ,really all lipos should be stored outside in an ammo tin they should be charged in a lipo sack I know we don't been in this hobby for years I have never had a lipo catch on fire but it only takes one to burn the house down

 

[LoneRCRanger]

Scary! I just checked the LiPo batteries for each of my quadcopters. So far, they are cool and not swollen. I don't know their charge state right now but I will check them. I need to get a steel ammo box I think. I have two now but they are in use. Again scary!

 

[gregb49]

It sounds as if we should be pushing for these cells to be made out of Lithium Iron Phosphate and accept the slight reduction in the power to weight ratio.

Like thermal runaway, Lithium-ion cells have a different level of safety depending on the shocks or mechanical treatments they may undergo during their lifetime.
The nail penetration test is the most revealing way to qualify the safety of a cell technology.

The test presented below is performed by perforating a Lithium Ion NMC cell and a Lithium Ion LiFePO4 cell.
We find here the same extremely stable behavior of Lithium Iron Phosphate cells while the NMC cell ignites almost immediately.

For information, the LCO, NCA, or Lithium Polymer cells have a similar behavior to the NMC in a perforation test (immediate inflammation)
From Safety of Lithium-Ion batteries

So next time you see a Tesla, just remember that it is powered by NCA: Nickel Cobalt Aluminium, cells, and take suitable action.

(I'm off to move my LiPo cells out of the house!)

 

[holtneil]

I didn't want to scare you guys but it's important you know what these lipo bombs can do , if you fly with a full charged battery when you land it will be on or near store charge rate
Happy New year everyone

 

[Jeff Neese]

...
My conclusions are:
1) Stick to the supplied charger.
...

Not really. Most of us have "real" chargers which are almost always far better than what comes with the quadcopter. Look into something like the SkyRC B6. It's one of the best investments you'll make in this hobby.

 

[gregb49]

Not really. Most of us have "real" chargers which are almost always far better than what comes with the quadcopter. Look into something like the SkyRC B6. It's one of the best investments you'll make in this hobby.

I should have qualified that comment, if you don't have a proper LiPo charger.

I would prefer to charge my JJRC X11 (Bugs 4W) battery with something like the SkyRC B6 but the connections don't appear suited to such a charger. Before putting my drone away for any length of time, I'll follow Holtneil's advice above.

 

[MJW]

So if I fly my drone until the drone shut's itself off, that's the storage charge?

 

[holtneil]

Not always you need to be careful if you go to low on voltage per cell the battery will be damaged , it's not so bad on a single cell battery but 2 cell and above don't go less than 3.2 volts per cell , I never go below 3.7 a cell and I have batteries that are in there 4th year but that's me gentle on my batteries
If your battery has a balance lead you can get a tiny battery alarm so you can use this to tell you when you hit this voltage

Low Voltage Lipo Battery Tester LCD Warning Indicator Checker Alarm - ESC RC UK | eBay

These are perfect for most multi cell batteries and are a battery saver, use these and save you batteries as they will alarm you of low battery levels when you check them. They are suitable for the following.

www.ebay.co.uk

 

[MJW]

I notice on my charging lead from the battery container there are three wires, one black and two white, are those to the individual cells, it's a twin pack, so like the black is a common ground to the two cells and the reds are independent positive leads to each cell?

 

[holtneil]

Yes that's right

 

[wafflejock]

Good write up here particularly see the discharge graph shows how at different loads or current how much actual capacity can be drawn.

RC Lipo Battery Guide: Explanation, Safety, and Care • LearningRC

An in-depth guide to lipo batteries containing everything you need to know about lipos - from ratings to safety.

learningrc.com

Think the non obvious things when learning about batteries is the voltage rating is the "nominal" or average voltage the cell is designed to put out but it grows as you charge and shrinks as you discharge, also the battery like all components has some resistance and that "internal resistance" is what determines the C rating or max discharge (and max charge rates) the internal resistance is based on both the chemistry used in the cell, the anode, cathode, electrolyte, lithium ion mix, and the interface layer between the positive and negative side.

Battery University website is pretty good if a little dated for most of this info as well. Agree with previous safety precautions I generally use "lipo safe" bags that zip up or have flaps to seal and use a "batbox" fire safe box from hobbyking for charging.

---

Just to clarify I am talking with 3-5S batteries and anywhere from 1.3Ah to 5Ah per battery, for the smaller ones I am a little less paranoid but good to keep them in a lipo safe pouch at the least.

 

[MJW]

I did a pin check at the three wire connector, 1.8v one one side, the other was at 2.4v, took the battery & charger to work and plugged in, monitored battery temp, no change in the time it was charging, when done 4.1v per side.

Center wire is the common, outside pins are to the separate cells.

 

[wafflejock]

Anything below 3.0V isn't really ideal and below 2.5V is typically unsafe not sure you were getting a good measurement initially usually chargers just refuse to charge if below the low limit, some batteries also have a low voltage cutoff or LVC circuit board built into them within the pouch so the leads coming out are hooked to that instead of directly to the tabs on the cells if that's the case they will stop outputting voltage or may look like very low output voltage even though the cells inside are at 3.0V if you have a charger that shows the voltage while charging per cell then can see it jump to 3.0V or higher as soon as charging. Could also just check with voltmeter a few minutes after starting charge, there is no memory effect so can partial charge with no issue (better to keep 20% in there and only charge to 80% for long term use like in Tesla cars but for us going closer to the limits makes more sense for flight time but push it too far and kill your cells immediately, assuming no LVC)

 

[gregb49]

Low Voltage Lipo Battery Tester LCD Warning Indicator Checker Alarm - ESC RC UK | eBay

These are perfect for most multi cell batteries and are a battery saver, use these and save you batteries as they will alarm you of low battery levels when you check them. They are suitable for the following.

www.ebay.co.uk

Thanks Holtneil, I've ordered one, but for others, please note that this comes without leads. A more expensive, more comprehensive product might be:
HTRC iMAX B6 AC 80W Digital LCD RC Lipo LiFe NiMh NiCD Battery Balance Charger

 

[MJW]

I think you misunderstood my post waffle, so let me clarify,
I just purchased my first drone and this is my first venture into Lipo batteries, I did some research here and else where on the net.

Here there seemed to be a paranoia about battery explosion, I did a search on Youtube of any video's about it, there seemed to be a lot of guys damaging their cells just to blow them up, they are basic stupid people as far as I can tell, driving nails through the cells or throwing them down on the ground.
Intentional destruction of the cells integrity for the camera.,

I also understand that there can be overcharging issues that can cause the cells to swell and possibly explode.

My post is stating that I used the pack as it came from the manufacturer and gave my drone it's first flight, then when it set back down I turned it off, removed the pack and took voltage measurements and those are what I posted.
I then took the pack and factory supplied charger to work and charged it.

Using an infrared temp gauge I monitored the cells temp during charging.

The batteries voltage ended at 4.1 volts per cell, now I'm waiting two days and then I'm going to take another reading on the cells before my first flight then I'll take another reading when the drone is done with the pack to see where it drains them to.

These batteries have gone through extensive testing by the manufacture to insure product safety and use.

They set charging times and charge amperage's well within safe parameters, when we exceed those parameters that's when damage to the cells can happen.
Cells can also be damaged in crashes so due care must be taken during inspection of them after a crash,

Other than those situations these battery packs are safe, other wise there would be reports of these packs blowing up on the shelf in stores waiting to be purchased.
Ever hear of a drone kit blowing up in a store waiting to be sold?

I raced RC trucks for years, the only guys having problems with their Ni-Cads & Lith's were doing stupid things with their trucks and chargers.

Take this for what it is, if you stay within charge limits and proper treatment of your cells you can expect them to last, and yes, use a bag to charge the battery in and after that if the cell should be safe to store, and yes I'll store them in a safe bag.

During charging with the stock supplied charger the battery didn't even warm up, matter of FACT it did not change in temperature at all, not 1 degree.
Manufacturer said 5 hrs charge time and that's what it took, I have two more packs and another charger coming and that manufacture states 3 hrs to charge, so that's what I'll test those at the same way.
So if i want to go out and fly for several hours then I'll have to buy a lot more packs, that's ok, that's the price I'm willing to pay for a nice safe long day of flying.

My drone flies for 15min on one pack, so for three hours of turn around flying I'll need twelve packs, so that the first pack given it's not warm after the flight can then come off the charger and go in the drone.

At first it seems like a large pay out to fly for a whole day, but how many whole days will they provide?
How many breaks in that day, lunch, chit chat and so on, so I'm thinking realistically eight packs, and that's what I had when I was racing RC trucks.
And dude's, I can only do this for a few hours a day at most now at my age anyway.

Am I going to own a fleet of drones?
Not likely, so for now if I find out other wise I'm going to target six packs, other wise I won't stop to eat and that's more important than flying,,,,,,,