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If your RC battery doesn’t seem to be charging at all and it keeps rejecting a charge or showing an error, there are a number of possible reasons why this may be happening, and we’re going to talk all about it in this article.
There are a lot of possible reasons that your RC battery might not charge. Those reasons why will vary depending on the type of battery that your RC car has. We will begin with the reasons why for a LiPo battery and then will go into the NiMH battery further into this article. If you have a NiMH battery you will want to scroll down to that section.
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Possible Reasons Your LiPo Battery Isn’t Charging
Here are some of the things that may be the reason your LiPo battery is not charging:
A faulty Li-Po charger
Even though this is about the least likely reason for your LiPo battery to not charge properly, it is still a possible reason. It is, therefore, worth it to find out if the fault is with your charger by trying to charge another battery pack with it. If it charges another battery pack without any issues then you know that your charger is fine. If it won’t charge multiple batteries then you have a faulty charger and need to replace it.
A broken connection
The possibility of a broken connection somewhere is another possible reason your LiPo battery isn’t charging. There may be a broken connection in your charge lead/wires, the battery connector, or the LiPo wires. You can use a continuity tester or multimeter to check any wires, connectors, or plugs.
Check your connectors and clean them to make sure that there is a good low resistance connection. If there are any frayed wires, the performance of the batteries will also be affected, so you might want to make sure that these wires are repaired if they are cut or re-soldered.
Over-discharged battery or cell
Another possible reason your battery is refusing to charge is that you may have over-discharged your battery pack or one of its cells. This can lead to the charger not recognizing when the battery has been connected, or it may show you an error message.
There are a number of factors that can cause cells to be over-discharged. Here are some of those reasons:
- Always running your RC vehicle for very long periods with no voltage cutout set on the ESC
- Not balance charging the battery pack, which can result in one cell having a lower voltage.
- One cell becoming faulty, especially when the battery has been either used a lot or abused.
Over-discharging can typically cause permanent damage to a Li-Po battery or one of its cells if it is over-discharged. It is best for you to set your ESC voltage cutout in a way that makes sure that the battery can not drop below 3.0v or 3.3v per cell. The battery manual or paperwork can provide good information on what voltage is the lowest safe voltage.
When you’re not using your LiPo batteries for more than just a few days, make sure you store them at the correct storage voltage. 2s batteries, for example, should be stored at 7.6v.
Possible Reasons Your NiMH Battery isn’t charging?
The possible reasons your NiMH Battery is not charging are much the same as the reasons a LiPo may not be charging.
Discharging your NiMH batteries too far may lead to the charger mis-detecting the number of cells, and this could be a reason for your battery to reject charging or not charge properly.
A faulty charger
This is also another possible reason for your battery to reject a charge. To check if your charger really has a fault, try to charge another battery pack with it and see how well the charging goes with that pack.
A broken circuit
A broken circuit somewhere is another possible reason why your NiMH battery pack isn’t charging. Make sure you check for any broken circuits and if you locate them then you can repair or replace the damaged spot.
How to Revive Your Dead LiPo Battery
For starters, never discharge your LiPo batteries below 3.0V/cell to avoid permanent damage. Many chargers don’t even let you charge a LiPo battery below 2.5V/cell. So, if you mistakenly run your vehicle too long, leave the power switch on, forget to unplug the LiPo, get your plane stuck overnight in a tree, etc. you may find that you’ve discharged your LiPo down well below 3.0V/cell. When that happens, here’s what to do:
If your LiPo is below 3.0V/cell
When your battery is below 3.0V/cell, charge the LiPo at a significantly reduced rate of 1/20~1/10 C rate (1/20~1/10 [0.05~0.10] x it’s capacity) until it is above 3.0V/cell.
More charge setting notes
Recharging a LiPo below 3.0V/cell may require you to use a NiMh or NiCad charger setting on the LiPo batteries since most smart chargers include safety features to prevent a user from charging a LiPo that is below 2.5V/cell because it can be very dangerous using a standard charge rate. Use a NiMH/NiCad setting to get a low and constant charge current and charge until the battery is above 3.0V/cell. Never leave the NiMH or NiCad charger unattended when using them to get the LiPos above 3.0V/cell. This is because the NiMh/NiCad end-of-charge detection method is incompatible with Lithium-based batteries.
If you leave it on the charger till it’s full, you can’t detect the end-of-charge state, which means the battery will overcharge until you remove it or it bursts into flames (not a good option obviously).
LiPo is 3.0~3.7V/cell
As soon as it’s above 3.0V/cell, you may increase the charge rate to 1/10~1/5 C rate [0.10~0.2 x its capacity] until the LiPo is ~3.7V/cell or more. Now, set the charge rate for your 1300mAh 3S LiPo to 0.2A. This equates to a 0.2/1.3 = 0.154C charge rate.
You may now choose to keep the LiPo in a fireproof container or LiPo-safe charge bag.
LiPo is 3.7~4.2V/cell
Approximately above 3.7V/cell, you may raise the charge rate again to 1/2 C rate [0.50 x it’s capacity] until the LiPo is full (4.20V/cell). Now, you may set the charge rate for your 1300mAh 3S LiPo to 0.5A. This is equal to a 0.5/1.3 = 0.385C charge rate.
You can also watch the video below to see how to revive your LiPo battery.
How to Revive Your Dead NiMH Battery
Here are a few steps to reviving your dead NiMH battery:
First step: Checking the battery
The first thing for you to do is check if there’s any juice left in the battery after a while of charging to find out if it is dead. If it is, then the next step would be to revive the battery.
Second step: Reviving the battery
Take a fully-charged similar battery of the same mAh. Next, connect the positive terminal of the fully-charged battery to the positive terminal of the dead battery and, in just the same way, connect the negative terminals.
Allow the batteries to stay connected for a few seconds, about 20-30 seconds should be fine. Right after this time connected, check the battery voltage of the dead battery. If the reading you see is higher than the 0 value, then you know that the battery is revived.
However, if the battery is still dead after you have done all of these, repeat the process and try it a few more times if it is still giving you issues. Most NiMH batteries will come back to life after a few tries. Make sure that it’s actually a fully-charged battery you’re using to revive the dead one. As soon as the battery is revived, charge it until it gets full.
The video below gives you additional things to try to revive your NiMH battery pack as well.
There are a variety of different reasons why your LiPo or NiMH batteries won’t charge but hopefully the information above has been helpful to determine the exact issue and what you can do to fix it.
If none of the above steps work to fix the issue then unfortunately it is time to go out and get a new battery pack. Thankfully batteries for RC cars are not incredibly expensive so you won’t break the bank even if you have to replace it.