All FPV pilots eventually run into the issue of having one of the cells on their lipo batteries get so low that their chargers won’t charge the battery anymore.
Normally, this happens when you fly your battery a little too long, and the voltage drops so much that a cell or two can’t recover by itself.
This can also happen if you leave your battery plugged in to things such as a lipo checker or a charger that isn’t plugged into the wall. These electronics usually take power from only the first cell of your lipo, leaving it completely drained.
Here’s how you can revive your dead lipo cell, using a charger that can charge lead-acid batteries (Pb) and a battery checker.
Is it Safe to Revive
Sometimes it isn’t safe to try to revive a dead lipo cell.
If the cell is at 0V, it will not hold any charge if you try to revive it, and the voltage of the cell will spike and the battery might burst into flames.
If your battery cell is damaged, even if the cell is still revivable it can explode and result in a fire. Here’s a picture of one of my batteries with a damaged 5th cell. It still might be revivable, but it’s not worth it to try.
A good rule of thumb is if your lipo is physically damaged, just dispose of it immediately. Don’t try to fly with it, charge it, or even keep it around.
Lipo fires are hard to put out, and a twenty dollar battery is not worth burning your house down.
Is the Battery Cell Revivable?
Any battery cell that has a voltage of over 1V should be revivable. A properly functioning lipo cell even if it gets drained all the way to 0V should recover to around 1 to 2.5V on its own.
However, some lipo cells can’t be revived.
If the battery cell that you’re trying to revive is at 0V, so dead that your lipo checker and lipo charger can’t detect it, you probably won’t be able to revive it.
This means that it has internal damage, since even a fully drained lipo that’s functioning properly will bounce up to around 1 to 2.5v.
Even if it could be revived successfully, it’s not worth the safety risk, and will be an unstable cell in the future.
How to Revive a Dead or Low Lipo Battery Cell
Normal LiPo charging will not be able to revive your dead cell, because if the cell is low due to physical damage, it can cause a fire and is a safety hazard.
However, if you’ve already calculated the safety risks, you can revive it yourself by using this method.
Step 1: Preparation
Most chargers used for lipo batteries can also charge other types of batteries. We’re going to be using the lead-acid mode (Pb).
Plug the battery into the charger with just the XT60, and plug your balance lead into your lipo checker. It’s important to keep an eye on the cell voltages during the revival, to make sure they don’t get over 4.2V.
Step 2: Selecting the Voltage
Select a Pb voltage to charge at that’s a little higher than the voltage of your battery.
My battery was at 14.3V, so I used the 6s (14.4V). The lipo got to 14.4V very quickly, so I needed to change the charger to 7s (16.8v).
Step 3: Starting the Revival Charge
Once you’ve got the right voltage selected, start charging at 1C. If your battery is 1500mah, 1C IS 1.5 amps.
Charging via the XT60 with the Pb mode charges all your cells up at an equal rate, so keep an eye on each cell to make sure the highest one doesn’t go over 4.2V. If they reach 4.2V, read what to do if cells reach 4.2V below.
Step 4: Balance your LiPo Cells
Once your cell that you’re trying to revive is above 3.5 volts, you can stop the Pb charge, and use the balance charge feature for your lipo.
All your cells will be charging at the same rate, so your revived cell’s voltage isn’t going to be the same until the very end of the charge.
Don’t leave the battery unattended when it’s balancing, and keep an eye on it.
Once it’s finished balance charging, all your cells should be at 4.2V, and your previously dead cell is successfully revived.
What to Do if a Cell hits 4.2V
If your other cells that you’re not trying to revive are at 4.2V or reach 4.2V while you’re trying to revive the dead cell, it’s a little tricker.
You’re going to need to discharge each individual cell.
To do this, I connected a wire to each individual cell through the balance lead, and then discharged each cell one by one using the 1s discharging feature on my charger.
I was able to pull out the little pins from the female side of a balance lead extender I have. They fit perfectly into the balance lead, and I connected them to my charger with alligator clamps.
You shouldn’t need to discharge your cells too much, since it doesn’t take much energy to revive your damaged cell. You only need to go down to about 4.0V to successfully revive your battery.
Dead cells in lipo batteries happen to everybody, so thankfully they’re easy to revive.
Just remember, it’s always better to be safe than sorry. If your lipo is physically damaged, just dispose of it.
Comment below with any questions, and let us know how you got a dead cell in your lipo battery!