What Is A Good IR For A Battery

So when internal resistance is too high that's bad when internal resistance is low, that's good but what is a low versus a high internal resistance, that is impossible to say exactly because the internal resistance of a cell depends on the size of the cell. In other words the million hours. So in order to discuss internal resistance, for example I can easily talk about like a 1300 million hour cell, I deal with 1300 million hour cells all the time, something around the 1000 to 13 million hours, very common size for 5 inch freestyle, depending on if you're using 4s lipo battery or 6s lipo battery. So I can tell you that for a cell in the range of about 1000 to 13 million hours, an internal resistance of let's say around 20 is not that great, but probably still usable. An internal resistance of around 15, and I think the the unit is milliums an internal resistance around 15 is okay but not really impressive, and then an internal resistance of down around 10 and into the single digits is very very good. So if you deal with a particular size of batteries all the time like if we were to ask Aaron Sciati, what's a good internal resistance for an 850 million hour battery, because he does a lot of stuff with Cinnawops and Micros. I guarantee you he could rattle that off, I can't. I'm sure Internal resistance is in the milliome ranges. I know Millie is tiny, the internal resistance is tiny . If it was mega ohms, then the battery would just waste all its energy as heat, because of the resistance.

Here's what I would recommend you do, when you buy batteries, whatever size batteries you buy, start to notice the internal resistance of the batteries when they are brand new, and you will start to fill in for yourself, what a good versus a bad milleon value is. Now bear in mind that when you measure internal resistance two things affect the internal resistance that must be controlled for:  No. 1 is the temperature a cold battery has much higher internal resistance, a warm battery has much lower internal resistance.The best thing to do is to have the batteries inside at room temperature and in in most of the world in much of the world that flies FPV anyway you'll have climate control of some kind and your internal temperature will be relatively stable, that's not always going to be true but what you want to do is you want to always have the batteries at approximately the same temperature when you measure the internal resistance, otherwise you'll throw off the results. You should know that when people talk about internal resistance like manufacturers, the standard is to measure the internal resistance at a temperature of about 19 degrees Celsius, I I couldn't guarantee you that everyone uses that standard but that's sort of the standard room temperature and that's what I would assume if somebody said my battery has a certain internal resistance, I would assume they were talking about 19 degrees Celsius or very very close to that. So, the other thing is the state of charge of the battery, an empty battery will have higher internal resistance a full battery will have lower internal resistance, so the standard is to measure internal resistance at full charge, if you look at your batteries, if you have a charger that shows internal resistance while it is charging at the beginning of the charge, you'll see ridiculously high numbers and then as the battery fills up the internal resistance will go down, now some chargers have a separate internal resistance function that will measure the internal resistance independent of charging the battery, in that case you would just complete a full charge then you would measure the internal resistance good done. Many chargers though, only show internal resistance while they are charging which is annoying because you have to like catch the battery at the end of the charge cycle or you could take a fully charged battery and set the if you charge the battery to 4.2 volts tell the charger to charge it to 4.21 volts, that way, it'll do just a little bit of an additional charge cycle and show the resistance. But then measure the internal resistance controlling for temperature and at full charge, and then just start to you build a mental or even you could make notes and physically write it down of what your battery's internal resistance is when they are brand new, and what I would do is I would write down the C rating the internal resistance, and then as the milliamp powers, and then as the battery ages you'll see that internal resistance go up and when you have a battery that you're like damn this thing sucks I can't fly this anymore, do that again and note its internal resistance and you will sort of build a range for you. It is both a safety issue and a performance issue it's a safety issue because when the internal resistance is too high the battery will heat up during charging and could overheat and go into Thermal overload.