hello everyone in this video i'm going to be talking about batteries i'm going to try and cover most of the basics that you need to know to use batteries in your application a lot of this video is going to be very much focused towards combat robotics since that is my audience but a lot of this information is going to be universal for anyone using batteries and applications from robotics to rc to hobbies things like that so let's get started and talk about different types of batteries and different battery chemistries so before we get started i did want to mention that in this video i'm going to be saying generally speaking a lot because this information is generalized and it's more to give you just kind of a basic understanding of some of these concepts there of course will be exceptions and other use cases and things like that so talking about battery chemistry in front of me i have several different types of batteries and these are things that you might be using in your applications primarily a lot of the stuff here is going to be lithium polymer or lipo or lipoly i've heard it called that is one chemistry that is probably the much the most common if you're going to buy a battery on you know ebay or amazon or hobbyking something like that most likely it's going to be a lithium polymer or a lipo battery there are other variants of lithium batteries we also have i think this is a life battery which is a lithium iron phosphate and then i don't have oh yeah i do have some lithium ion batteries here these are typically going to be a hard shell battery they're used in different applications but for the hobbyist you're generally going to be using a lipo now over on this end you might see some good old classic nim batteries nim is nickel metal hydride i don't have any cads here but that is another type of rechargeable battery these are largely out of fashion right now they just don't have the discharge rate they don't have the power density and if you're using any type of these batteries for combat robots or other robotics applications you might either a have a very specific reason for doing so or you maybe might be outclassed if you're using these in a combat robot situation you're probably not going to have the current delivery they're going to be way too heavy they just don't have the power density and the current delivery of the new modern lithium batteries the different types of battery chemistries have a multitude of different characteristics to them we could talk about how many times a certain battery likes to be charged and recharged and discharged and you know how long it can be discharged for and what the charging profile looks like and all that good stuff but that is beyond the scope of the video but what we are going to talk about is how the chemistry affects our use of them for instance a lipo battery has a nominal voltage of 3.7 volts that means that each cell inside of this battery is 3.7 volts nominally nominally basically means that is just kind of the baseline level of the voltage it can go up and it can go down from there a fully charged single cell lipo is going to be 4.2 volts and i think fully discharged it's like 3.2 3.3 something like that a life battery the nominal voltage is about 3.3 so a little bit lower lithium ion 3.7 and then your nims and nicads are going to be about 1.2 volts so how do we get a battery that is like 24 26 volts well each one of these is made up of individual cells so by taking those individual cells and running them in series plus to minus plus to minus plus to minus we can get different voltages out of them so let's take a closer look at cell voltages and discharge rates and all that good stuff i have a variety of different battery packs in front of me and all of these batteries here are made up of several individual cells wired together in series to get various different voltages now a battery is going to have basically three ratings it's going to have the capacity which you can see in these big numbers here on the front and then it's also going to have an s rating and then also a c rating the s rating is going to tell you how many cells are inside each battery this is a 3s battery and if we look inside we can see one two three individual cells i like this one because you can clearly see the individual cells wired in series and if we look at the label we can see it's an 11.1 volt 11.1 divided by 3 is 3.7 3.7 is the nominal voltage for each one of these cells now if we look at one of these bigger batteries this is a 6s and that gives us 22.2 22.2 divided by 6 is 3.7 volts so there's six individual cells inside this battery so now we know that the s rating corresponds to how many cells are in the battery what is the capacity rating that we see on all these we got 5.0 3.0 1.5 400 milliamp hour what do these numbers mean well that is just simply the capacity how much juice is inside of one of these so if we look at this big one it is a 5.0 and you see maybe in smaller writing here 5 000 milliamp hour that basically means that if you had a 5 amp load on this if you were drawing or pushing 5 amps worth of current out of this battery it could last for one hour doing that you will see it in amps or milliamps milli is one thousandth of an amp so 5 000 milliamp hours is the same as saying 5 amp hours typically a smaller battery is going to be rated in amp or milliamp hours but you know it's all over the board this smaller one is rated 1.0 which is 1 000 milliamp hour and of course this little guy is only 400 milliamp hour so if we look at this we can say that it can deliver 400 milliamps worth of current for an hour or you can simply do the math it's not perfectly linear but if we had a half an hour we could do 800 milliamps over that whole time or if we had 15 minutes we could do 1.6 amps so that begs the question we know the capacity we know the voltage what is the peak amount of current that these batteries can deliver well that's the c rating for most robotics applications and combat robots definitely you're going to want to pay attention to the c rating of the battery the c rating is going to tell you just how much current your battery is going to be able to provide the rest of your electronics all these batteries have very different c ratings but they're all calculated the exact same way so if we look at this big battery it has a 75 c discharge rating and that just means that 75 times the capacity which is 5 is going to be the maximum amount of current or amps that this battery can provide your electronics 75 times 5 is 375 so that means this battery can produce 375 amps worth of current it can do that instantaneously it's not going to be able to do that for a extremely long time but that is the maximum current that this battery can't provide all of these batteries are going to have different ratings they're going to range anywhere from 20 c all the way up to 75 you may see some batteries with a peak rating of 100 or more but about 100 is going to be about your max and 20 is going to be on the very low side if you're doing the math in your head you're going to realize that the higher the capacity of the battery the more discharge you're going to have the more current you're going to be able to provide because it's always the discharge rate the c rating multiplied by the capacity so generally speaking the bigger the battery the more current you're going to be able to provide so now that you have a perfect understanding of the s rating the c rating capacity cells and all that good stuff now you needed to connect it into something so let's talk about the connectors this is a pretty good sampling of all the connectors that you're going to encounter with batteries over here i'm going to start with this little guy that red connector right there that one is a jst rcy connector jst is actually not a type of connector it is actually the manufacturer or the brand behind it so that is what that connector looks like and this is really only going to be useful for your smallest robots think of like 150 gram the um fairy weight i guess and then a us ant weight one pound anything beyond that you're just going to run into current limitations with that connector i'll talk about these in a second then you're going to be moving up into the xt connectors and you have a couple different varieties here don't mind the different colors of these they're effectively the same connector you have an xt60 or i'm sorry xt30 which is this little guy xt60 and an xt90 and this is also an xt60 xt30s are going to be good for like your three pound robots and probably that's about it or maybe drive applications and bigger bots the xt30 can definitely be used in a three pound or maybe even up to a 12 pound bot and then the xt 90 is going to be pretty much in all of your bots and bigger for the really big bots you might even want to re-terminate this with a different connector so that leads us to these little connectors that are hanging off of all the batteries what are these guys well these are the balance charge leads and we'll get to that in a second when we talk about the charger and the thing that you'll notice is there's one more wire for however many cells there are so this is a three cell battery and we have one two three four wires this is a six cell and we're going to have seven wires these are basically wired into each one of the individual cells these use a jst xh connector if you want to extend these these are not really used for power delivery they're only useful for charging but sometimes you might want to extend these out just to make it easier to get a bunch of these batteries into the charger so once again these are a jst xh connector and they can come in any number of different pin configurations anywhere from two all the way up to you know 10 or 12 or whatever so now we need to actually charge the batteries and there are specific chargers for lipo batteries of course there is why couldn't it be easy so i've got a couple chargers in front of me and there's a couple things that you need to look out for when choosing a charger they can be pretty inexpensive and pretty simple so let me run it through the biggest thing you need to pay attention to is is it going to be able to charge the battery that you have if you have a 25 cell battery or something like that you might need to get a specialized charger but generally if you're in the you know two to six or eight cell range most chargers are going to be able to handle that right on the front of them and in the description it's going to tell you this can handle one to six cell it's going to do nim nicad lead acid all that good stuff and the other thing that you're going to need to look for is the charge rate how much power are you going to be able to put into the battery we'll get into that in a second but generally speaking you're going to want to charge the battery at 1c so basically one times the capacity in amps so this big one we're going to want to charge this at a rate of 5 amps and then this smaller one over here 1.5 so you're going to push 1.5 amps into it and depending on the voltage of the battery that is going to ultimately determine how much wattage or how much power you're going to be pushing into the battery to charge it that is the first factor the second factor you see these two chargers look nearly identical to one another the biggest difference is this one has a built-in power supply this one does not most battery chargers do not have any power supply whatsoever so you're going to need to supply an external power supply to this that either plugs into the wall or get this is going to be battery powered to charge your you guessed it batteries so be sure to be on the lookout for that some people like the ones without a power supply i'm not really a big fan i kind of like the all-in-ones there are also chargers that can charge multiple batteries at a time all sorts of stuff like that i actually just have this really cheap one plugs into the wall charges one battery at a time always worked out fine for me and i just have this other one as a backup the next thing that you might want to look at is one of these cell voltage monitor things it is a very simple little device i think there's a 15 or 20 dollars and you can take the balance cable plug it directly into the side of this and i'm not sure if you're going to be able to see that but it'll give you the voltage and the capacity so right now we're at 79 of a charge and 16.07 and we can even use these buttons to look at each individual cell voltage so something like this is extremely handy because you're at a competition you're doing whatever you throw all your batteries into your toolbox and you need to know what the charge is so something like this is a very handy tool to have so i wanted to do a very quick walkthrough on how to charge a battery there's a lot of settings and a lot of stuff going on in these chargers thankfully almost every single interface is nearly identical between all the chargers i've used so from this main screen you can select all your different types of batteries you got life lie low high voltage nims nicads all that since this is a lipo battery we're going to go ahead and go to lipo we're going to hit enter and you see we have a couple different selections we've got balance we've got discharge we've got storage fast charge things like that we are going to be doing a balance charge so a battery typically does not like to be stored at its maximum voltage and it also doesn't like to be stored when it's fully dead so that is why you have these storage so you would just plug this in and charge it but you would do the storage and it would bring it down to the appropriate level so let's talk about connectors on the side of here we've got a couple banana plugs and then all of the balance charge ports with these chargers you're generally going to get a lot of cables so it's going to be a banana cable that goes into there black to black red to red and then it's going to be terminated with a dean's connector this is what a dean's connector looks like and then you're going to have a bunch of mating ones that go to your battery so you got an xt60 i've got an xt90 i've got the one of the rcys that we talked about it's going to come with all of these so you just simply plug that in it's keyed so you can't get it wrong we're going to plug this side into the battery and then we're going to plug the balance leads into the corresponding balance leads on the charger and that's pretty much all there is to the connection side so you can see where you might want this to be a little bit longer if you have a really big battery or a big battery pack so from here we've got a few settings we're just going to hit enter and now we can change the charge current and we can also change the voltage which is how many cells the battery is earlier i said that i always charge at 1c that is generally the best way to do it this does not damage the battery it does not ruin the life cycle of it you can certainly charge a lot higher if you want if you're in a time crunch but honestly if you're in a time crunch and you just have to get a battery charged just make sure you have a spare battery i always have about three batteries just so that i don't run into that situation but you can charge a lot higher you will degrade the life of the battery by doing so so i always charge at 1c so that is 1.5 since this is a 1.5 amp hour battery we're going to hit enter and then here you can select how many cells the battery is this one is a what is this this is a four cell so we're going to go up to four cell and then you just click and hold it's going to check the polarity and make sure that there's something plugged into here and then we just hit enter and it's as simple as that it will start charging and you can even use the left and the right to actually view these cell voltages we've got one two three four cells and they're all right around four volts and if we go through we can see that the battery is at 87 percent it's not going to tell you how much time is left but it will give you some other little stats like that so it's really that easy to charge a battery so the last thing i want to talk about is safety lipo batteries are inherently pretty dangerous things if you think about combat robots or robots in general think about like an rc car think about what those things can do think about how fast an rc car can drive or think about a combat robot you know how much they can smash and hit all of that energy was at one time contained within one of these little batteries and here is a nice example of one that is super puffy and nasty i'll get a closer shot of that and then here is one that has a little nick in it and as you can see i am handling these very very delicately because lithium batteries lipos in general are pretty delicate things any kind of puncture or any kind of impact can cause them to rupture and once they burst open into the air it's just like this chemical chain reaction and things get really nasty as you can see from something like this so general safety you should always charge inside a lipo bag i always charge very safely therefore i don't have a lipo bag i am not claiming this is the best way to do it it is just kind of my practice i always charge attended i am always out here when it is charging sometimes i even charge on the concrete i do not use any battery that has any compromises whatsoever like this one has a little cut in it i will not use this this is just for demonstration purposes if you have a battery that has any puffiness to it or has like um air or gas inside of it if it's not solid don't charge that battery toss it and when i say toss it make sure that you dispose of these responsibly and properly usually at robot combat events there is going to be some bin specifically for lipo batteries or check with your local county or city for the proper way to dispose of lipo batteries but please absolutely do not just toss these into the trash because if they get compressed they will set on fire and it could well literally create a dumpster fire so be mindful of that um don't try and charge batteries that have any issues with them whether it's puffiness whether a little bit of break in it or you know whatever this is going on um you can get lipo bags as i said earlier which is basically a fireproof bag that you can put the lipo batteries inside of to either transport or charge or store whatever that is generally a good idea they're pretty cheap get them on amazon i should probably get a couple and i think that's all there is to know i think the last thing is life batteries which is the lithium iron phosphate are basically a much more stable version of the standard lipos so if you have children or if you're doing robotics with kids you might want to look at life batteries they have a significantly lower discharge rate so they can't provide the current delivery they don't have the current density as a traditional lipo does but they are a lot more stable and a lot more safe um this is to my knowledge the only lithium battery that can and legally will be used in like kids toys things like that so life batteries are going to be a lot more stable and if let's say you have a robot that has issues with battery fires a lot and maybe you want to look at a life battery instead of a lipo so hopefully you have a much better understanding about lipo batteries in general you know hopefully you now know what the c rating is the s rating the capacity and all that other stuff and you can use that knowledge to calculate the appropriate size battery for your application there is of course more to talk about on this topic and you know judging on the interest in this video i might end up doing like an advanced battery tutorial because you can certainly create custom battery packs by wiring things in series and parallel and you can start using individual cells to get the exact battery that you need for instance on what i did for low low man i need a very slim battery so i created my own pack also like a lot of advanced charging techniques you will not always be in a situation where every single cell in the battery is exactly the right voltage you might need to kind of tweak that a little bit sometimes cells die you might need to jump them back to life so let me know if you're interested in kind of the advanced battery tutorial but hopefully this gives you everything you need to know to start with combat robots and other robotics in terms of knowing how the batteries work and how to use them thanks for watching be sure to check me out on facebook for any updates and thanks for watching see you next time that's two one fight robots both robots up to speed very quickly this is gonna be a heck of a first hit huge sparks flying what a hit and blood pressure just exploded that's a tough tap out and we have a battery and we got smoke