The Guide to Testing Your LiPo Battery Health for Your RC Vehicle

Today's video we're gonna be talking about the vital signs of a radio controlled lithium polymer battery pack. We're gonna be speaking about 4 of those vital signs in this blog that will ultimately allow you to understand the health and condition of your pack.

Now there are some visual inspections that you can perform, and all the specifications that we are going to be talking about, go above and beyond the visual inspections.

let's get started and talk about our very first specification here, which deals with capacity. Now capacity is an interesting one because to really ultimately understand capacity, you have to know how much you had when the pack was brand new essentially at day 0, verse the amount that you have today. The way that you do this is you would take that batter you'd run it into your radio control vehicle, and then you'd get that pack down to a voltage, let's assume 3.75 volts and then from 3.75 volts, you're gonna charge it back up to full 4.20 volts, and that amount of capacity that you put back into the pack with an average voltage from 3.75 to 4.20, which is going to be the specification for when your battery is brand new. Then you repeat that exact same test many years later or even a month or two later whenever you feel you want to check the capacity of that pack, and then you would have an understanding of the differences.

If your battery had a certain capacity that you were able to replace back into the pack, let's say it was 3650 milliamp hour that went back in the pack, and now you're only getting 3000 million hour back in the pack many months later, the amount of capacity that you have today VS or divided by the amount of capacity that you had originally on day 0. This is going to be the percentage of capacity that you have today. A number that's less than 75 % or so is telling you that the capacity in your pack is suffering and the pack is definitely showing signs of age.

One thing to note for the capacity check is I don't really recommend using the stickered value on the pack itself checking to see if you have a 5000 million hour pack and you want to check to make sure that you can get 5000 million hour back into that pack. I wouldn't necessarily recommend that, because a lot of packs that number on the face of the battery does not necessarily represent how much actual capacity your pack will accept, and it can be different based off of how far you discharge it. If you're discharging and charging from specific voltage values as our example provided, this is going to give you some hard stop numbers to go by.

Let's talk about the next value that we can check the condition of our battery, and that's going to be voltage. Voltage is a pretty good one, it allows us to check the balance between cells to make certain that all our cells are roughly in the same or similar condition. The best way to do that is to simply just charge your battery pack up, and monitor the amount of cells that you have and the voltages of those cells as you charge the battery. You notice that the cells voltage is deviating by more than a few percent, what you can do is stop that charge and then balance out the pack so all the voltages equalize and are balanced, then go ahead and initiate that charge at about 1.5C or whatever you usually use to charge your batteries.

As you charge up your battery once again and you so to still that your battery is showing one cell to have a higher voltage than the rest of them, chances are the cell or cells that contain the highest amount of voltage are the ones that are performing less than ideal, this can happen for a couple different reasons.

But it does tie into the next parameter, that we're going to be talking about which is internal resistance. Coming back from the same idea here if you are looking at individual cell performance and you have a voltage issue, you can then check your internal resistance on that cell to see if it is much higher than the other cells that are in that battery and charging. If you do confirm that your internal resistance on the highest voltage cell is actually the highest and very different from the other cells in the pack, then you've identified the health of the pack is weak as one of the cells within your pack or possibly more are not performing the same as all the other cells in that pack.

Another thing that we can do to understand the health of our battery pack is take the average amount of internal resistance of all the cells in our battery, and compare that to the average internal resistance of the cells when we had that battery on day 0. This is when we purchased it or on our first charge cycle, you want to compare those internal resistances. If your internal resistances are out by quite a bit, I would say somewhere around 3 to 5 times different, this is a sign that your battery pack is significantly underperforming, compared to when that pack was brand new.

Now there is something to note here if this does happen to you, what it may mean is that for your high performance, your high demand applications that battery pack is not going to give you the best results, you may want to retire that battery pack from that high performance radio control vehicle, and pass it off to a vehicle that does not have as much of a current draw associated with it. That pack can still perform very well in an application where the power draw is about half of what your high performance, high demand radio control vehicle is. This way you can kind of recycle your batteries into different types of applications, extending the lifespan of that pack. If the pack’s resistance is much higher than it has been in the past, this is not an indication that pack is unsafe to use you can and probably should recycle that battery into another application.

The last one that we have here is relating to the C rating of the battery pack, but we don't necessarily want to use the sticker C rating that we have listed on the battery label. What we can do is we can use use a calculation to ultimately determine the C rating that we actually have today, we don't necessarily need pass performance data, although it would help to be able to compare to what you want to do is you can hop on to the Patreon website you have the calculator that will allow you to determine the actual C rating of that battery. Another option that you have is you can go on the radiocontrolinfo.com website and use the Lipo actual C rating calculator there as well.

Mow what you want to do is you want to put in all the parameters that are required on that calculator, and then hit the submit button and get the result. If the calculators telling you that the batteries C rating is less than 10 to 15 C, this is a good indication that the performance of that battery pack is definitely underwhelming, and that battery is not performing up to a significant standard. It could be a sign of age or how experienced in terms of cycle count that battery pack is. If you're seeing C ratings around 20 to 35 C, this goes from low to medium amount of performance that you can get out of that pack up to the high amount of performance that you can get out of that battery pack. If you see a battery pack that goes above and beyond what we're talking about right here 35c or so, this is going to be a pack that shows good signs of performance, and is good for high demand, high current draw applications.

Keep in mind that this is a general rule of thumb. The best way to ultimately compare your pack's condition and health is to compare what that C rate in calculation was when you originally purchased that battery pack. This is the best way to ultimately determine all the different parameters of the battery packs condition by looking at what it was when it was brand new, to what it is when you have it after so many cycle counts or so many years. If you haven't started doing that with your new battery packs, this would be the ultimate takeaway that I hope that you're able to get out of this blog.