Battery Charging And Safety
I'm curious whether our audience here in the studio, how many of you fly drones currently so yeah got a couple of you guys cool. And I guess some of you are wanting to get into it for your business, taking... We were chatting earlier what was it that you guys do? I just want everybody else to kind of know kind of.
That we do architectural photography and we work with residential, model homes, we work with Irvine Company, (mumbles) so we do model homes and residential. The drone business is just booming right now but there's not enough people to fly and the work that is being created could be better.
And that's where we want to be.
Yeah for sure, what would be one of your hesitations about getting into using drones? Or do you have any?
For me personally, is actually flying it (laughs) that's why I have him (laughs).
(mumbles) going to probably do the camera.
Composition and the editing, so but other than that it's why I'm here.
Awesome. Well this next section that ...
we're going to get into is actually may seem a little bit tedious, I don't want to undersell the section, but we're going to get into battery safety and I guess it's just like we have flight safety these batteries that we're using, they're lithium polymer batteries. Or lipos as we call them. Now with a lot of these batteries with the Karma and all the DGI batteries now. You'll see them they look more like this and DGI calls these smart batteries. Whereas what we're used to is RC Hobbyist RC meaning remote control, those are just your standard lipo batteries you get at a hobby shop or online at a hobby dealer. They have an incredible amount of power to weight and the reason why we're probably even talking about drones today is partly due to the technology that exists today with cameras and small electronics but it's actually all because of these batteries right here. If we were trying to fly these drones with the old (mumbles) batteries that we tried to fly with, our flight times would be no where near what they are now and our drones' power systems wouldn't be as powerful. But with great power, like I said before, with great power comes great responsibility and some of you may know that lipos are to blame for a good amount of house fires, building fires, if you just don't know sort of the basics of how to deal with these batteries. The potential energy in them is huge and that's why companies like DGI are making these smart batteries and they are they're more expensive. Buying a battery like this that doesn't have any of the circuitry in it is cheaper and it's safe if you know what you're doing but the nice thing about these smart batteries they mitigate their any risk and they sort of as you see they're a lot easier to work with. So moving on to some lipo facts, not liposuction but lipo batteries. So this right here I'm holding is a 30 amp hour battery, that thing is huge. I was at NAB and this company Tattoo is trying to manufacture lipos they specialize in lipos, small lipos but also big ones for guys that are doing heavy lift work. The nominal voltage of lipos is 3.7 volts so that's just sort of like, nominal just means what they're named but when you charge them you'll see that each cell will read 4.2 volts, so that's a fully charged lipo cell (mumbles) these will have multiple cells, that one I think is a six cell battery, so there's six individual cells in there and in the case of DGI's batteries you can go in and look and make sure that all the cells are at whatever voltage they are, whenever a cell that's down a little bit, it probably means that your battery's on the way out, maybe there's a phase change in one of the cells or whatever and that's not just safety for making sure that they don't burn up or anything like that but make sure that your copter stays in the sky. With fixed wing aircraft, if your motor goes out you can glide it safely to a landing but with these copters the only reason they're up is because our power systems are working. So that's one thing to consider. Minimum voltage before damage, this is a little bit debatable three volts is kind of the minimum that you would want to run them to at under load. I think after you've shut the copter off it would probably read somewhere closer around 2.8 volts and certainly you can write this down, I've tried to put it all together in one spot in this course instead of having to go through all the different websites. And another thing you should do is obviously whatever battery you're using read any kind of manufacturing guidelines you have on it and again with the DGI batteries in particular, they just give you hey come home, or hey I'm going to land if you don't come home, sort of thing. And we'll get into that in the app. But for those of you that are starting to experiment with maybe your own DIY solutions making custom copters maybe heavy lift works like the Alta I think the Alta we're still using standard lipo batteries, so we're not using intelligent batteries, I could be wrong on that, we still fly the DGIS1000 and that doesn't use intelligent flight batteries, it just uses big lipo batteries standard. The rule of thumb I don't know if I put it in the presentation, but the rule of thumb for keeping your lipos healthy is to not run them past, you don't want to use more than 80% of their capacity, as soon as you go lower and lower and lower for one, the chemistry in the batteries doesn't like it too much but also you could lookup on the interwebs lipo discharge curve and there's like this slope it's like the battery goes goes and then there's like this curve and then it just plummets. So you could have plenty of power plenty of power and then nothing. So that's why like the DGI will say hey at 30% we want to remind you to come home, at 20% okay I'm going to return home on my own unless you tell me not to and at 10% sorry guys we're coming down. And even then it gives you wiggle room it's not going to discharge a battery to actual zero, like zero in the DGI business is actually going to be something like I don't even know, but it's going to be a safe cutoff voltage before you damage the battery, we could actually look at that. Typically they're arranged in series, series versus parallel parallel you typically are increasing your capacity, series you're increasing your voltage, so typically there are like 6S you'll see 6S on the battery pack or 4S. In a little bit here we'll take some of these out. That just means that there's six cells in series. Power to weight ratio like we talked before, it's much better than previous battery solutions. C Rating this is an important thing, typically what's recommended is that you charge your lipos at a one C Rating. Meaning one time the capacity. So if we've got in this case a 30 amp hour battery you don't want to charge it at more than 30 amps per hour if you can find a charger that will charge a battery that fast. But with these smaller batteries like this one here over on the Inspire is 5700 milliamps so that's 5.7 amps 5.7 amp hours, so you would want to charge the battery at 5.7 amps. Now that's if you're using a standard hobby charger, the thing with the DGI batteries now, is that they come with their own chargers, you don't really have to deal with that as much. But there are two different chargers you can get for the Inspire batteries, there's the one that's standard it comes with standard it's a 100 watt charger and then there's a 180 watt and we try to run the larger ones they charge a lot faster. With great power comes great responsibility. I don't know how DGI does this but I've seen that typically the useful range before you start seeing deterioration in these batteries is around 300 cycles. So you want to monitor your batteries however you can. We used to stick these voltage readers... There's a balance port that comes out of some of these lipo batteries and you put that on there and it tells you the individual cell voltages, some chargers will tell you the internal resistance of each cell. So anytime you see something that's off that's typically when you've got a phase change, also if you ever see a battery swell that means there's been a phase change. I still have some batteries that I'll fly in some of my helicopters that maybe they're a little puffy, they've swollen a little bit, but if I'm flying them in a noncritical thing like I'm out in the park and there's nobody around and whatever whatever, then I'd still use them, but the moment I start noticing a deterioration in performance and flight time like if your flight times or your capacity that you can put back into the battery is like 20% less that's when it's time to retire the battery, that's a rule of thumb. You don't want to run the battery down more than 80% you want to leave 20% reserve and also you can remember that 20% for if you start putting, even with these DGI batteries if you're only getting about 80% of what you used to get that probably means it's about time to retire the battery. So lipo charging and safety. What the smart batteries do is they have all the balancing features in the battery itself, so you don't have to... I keep referring to these batteries let me grab one here. So this is the Inspire battery and right here what's really nice is you click on this and it tells you voltage. I have these set so that after I'm done flying within a day it'll go back to storage voltage which we'll talk about here in a sec. But all I have to do is plugin the charger to this thing and it charges it up and what happens is it's supplying power to this and then this is essentially balance charging the cells, this is a six cell is it not, or does it say, I should know that. So it's basically balancing each cell to make sure that they're the same voltage. But if you're not using a battery like this you do need to use a special charger for lipos and what you do is you connect the power to the power leads then there's also a balance port where you plug in also the balance port and make sure that the voltages are all the same so that's very important with lipos 'cause there's separate cells there (mumbles). One C recommended charge rate, some batteries are known to be more high performance and will take more than a 1C rate so if you've got a battery where you can double charge at 2C that can be good but we tend to if we're not in a hurry just charge at 1C it's potentially easier on the batteries. This is honestly the main thing that I wanted to get across is yeah I mean, I've never honestly had an issue with charging but you hear stories from guys that have been in the hobby a long time or you can watch videos on YouTube of guys actually showing how these batteries can short and catch fire. You want to charge... You don't want to go to sleep and have these things charging chances are you'll be fine but there's always the odd chance that maybe you won't be. At our office what I do is down in the basement I've got it's concrete and I have an area where if one were to catch on fire everything around it's concrete, so it might catch some of the other lipos on fire it might be a big blaze but at least we're not around other combustibles. That's really the main thing is being safe with these guys. And then storage voltage this is also one of the other main points is these lipos they don't like to be at full capacity or under capacity. If you leave a lipo battery fully charged and don't discharge it to storage voltage which is about half capacity the DGI batteries will do it automatically you set it in the app we'll look at it either after a day or after ten days or whatever it'll go back to storage voltage. But if you don't do that, they'll just die on you the lifespan of these batteries will just be gone. So you'll go to it to the next day and you won't be able to get a charge out of it. Store a room temp or in a cool place basically I store my batteries where I myself would be comfortable. You get brownie points for storing them in a cooler location some people put them in the fridge and stuff like that, what I think about putting them in the fridge is that then you have condensation issues so I don't bother with that and I use my fridge for steaks and stuff like that (laughs). And yeah you're going to want to retire especially first commercial operators when we start seeing puffy batteries that's just a little warning sign to start retiring some batteries. Yeah.
How long do the lifespan of these batteries usually last?
You know, if you're caring for them if you're putting them at storage voltage when you're not using them I'd say about 300 cycles but it could be double that. If you're monitoring that's the nice thing you can see if you're monitoring and you're still getting even 95% 90% what you used to get out of them and the voltages are staying the same then I would feel safe flying with them. But when you start seeing it markedly coming down in capacity that's when it's time to do it but 300 cycles is a good amount of cycles. That's a guideline. In the DGI app it actually will say it'll give you a percentage for the lifespan of the battery, I'm actually not sure what it does when it says sorry there's no more. I don't want it to be so smart that it's not letting me use a battery that I paid for that's still good but I haven't come to that yet on these batteries so maybe somebody out there on the interwebs could tell us that. This is common story it's like the guys are out flying and they're flying and then you crash your airplane or whatever and then you dejectedly walk over to the car and you put all your stuff in the car and then you come back out and you're talking to your buddies like yeah just crashed my favorite airplane and they're like hey look at your car and the car's up in flames. That's not a one off story that's a common story with hobbyists is if you do have an accident don't just... Like really inspect the battery leave it out for a while make sure that there's not an internal short that's smoldering and about ready to go. So it really is pretty exceptional, it might've been cool if we could get the insurance clearance to go up on the roof here and puncture one of these batteries 'cause it's a light show. And if you're lucky enough to have some manufacturing guidelines some of the Chinese manufactures of lipos they're just like here you go, don't poke your eye out with it, but the DGI does come with an instruction sheet that tells you some of these things. Yeah flying with these, this is big for us folks that are traveling. You can have up to two that are 100 watt hour with you. This is how it is now and it seems like it's what it's going to be for a little while. You have up to two that are over 100 watt hour and then anything under 100 watt hour you can have as many as you like but they can't be checked under the plane you've got to have them in your control. You hope everybody's abiding by that because you know it's not a great feeling thinking that there's lipos being tossed around, you're just trusting how people packed them. So it's better that they be in your control and that's the case, some people print out the sheet from the airline when they travel 'cause sometimes if you're stopped it's good to have that on the ready and say well this is actually your guys' policy and you cannot check these they need to be on the airplane.
I had a question about the number of batteries that you would have for spares. Is it better to cycle them through, have two or three extras to prolong their life or because you have to actually get them to storage level and that sort of thing, is it better just to use two batteries all the time until one dies and then get a replacement.
I would only base like how many batteries did you use based on how much you need to fly. So I would just, if you typically want to go out and fly for an hour I would just get that many batteries, maybe one extra just in case. All you're going to do is you're going to go out and fly you're going to evenly distribute the use over them. A lot of us will number them so we just cycle through them. And just go fly have fun work with them but make sure that they're going to storage. The default setting with DGI is ten days I feel like that's a long time to wait for them to go into storage, I would set that to one to two days. One thing I heard is that when you tap on the little light here this actually resets the timer, so if you're always checking then maybe it won't go back to storage which is what I'm doing right now. What this can do too, some of you interrupt correct me if I'm wrong but that's something I heard from the interwebs is that if click on that it will start your timer over. So if you're like I was going to go flying today but the weather's bad, go through and click through them and maybe it'll give you another day before they go into storage voltage. So I just wouldn't leave it to ten days unless you had a real good reason to do that 'cause I think it's going to wear out your batteries faster. They don't like to be at full charge. Cool. So that's that monster of a battery.
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