Battery at 2.7V for 3 weeks. What should I do?

[Eachine98379872]

I have a 4s 75C lipo battery and one of the cells is at 2.7V. I have ordered an ISDT Q6 nano thanks to recommendations from the forum but it's going to take a couple of weeks to come. In total it will have been at 2.7V for 3 weeks and I have no way to charge it until my new charger turns up. The other cells are at roughly storage voltage.

What should I do? Can I slowly charge it with the Q6 and continue to use it? Is it safe or have a permanently damaged it? If I have damaged it does that mean it's unsafe to use or just won't give the drone power for as long?

As a side note the battery is 75C. As coulombs is amps per second does that mean it provides the drone with 75 amps? That sounds like an unreasonable amount.

 

[droneguy]

Extended periods at voltages below 3v usually damage the battery due to altered chemistry within the battery often with permanent consequences, but normally it's not a huge issue for a few days or a week. You can try an see. You'll have to test the battery afterwards to see if it is still reliable enough to use. Because one cell is much lower in voltage than the rest, this may indicate a failing cell in which case you may be out of luck, but there's no harm in trying a long as you do it safely.

What charger do you currently have? Do you have a cell balancer like the ISDT BG-8S or FlyRC type? There's a ton on knock off out there by many other brands.

The process for recovering a battery below 3v is to balance it and charge it at a very low current. A good smart charger will also indicate the cell's impedance which is helpful in seeing if the battery is damaged. The impedance should be similar across all cell, if not it will result in an uneven discharge and an unreliable battery. A 2-5ohm difference is ok but anymore and further testing should be done. It is very important that you do not leave the battery unattended while you charge it. The current must remain around 120mA or lower. If there is damage to the battery, the current can spike up sharply and quickly resulting in a high current situation, burst cell and even a fire. The good news is that if the cell is ok, it will take the low current charge and slowly get past 3v. I usually unplug the charger at 3.2-3.4v and give the battery another pass on the balancer before charging the rest at 1C. If it all worked according to plan, your battery should be ok. You will not be able to trust it during the first couple flights as the low cells may sag abnormally quick if there is permanent damage so be careful.

 

[Eachine98379872]

Extended periods at voltages below 3v usually damage the battery due to altered chemistry within the battery often with permanent consequences, but normally it's not a huge issue for a few days or a week. You can try an see. You'll have to test the battery afterwards to see if it is still reliable enough to use. Because one cell is much lower in voltage than the rest, this may indicate a failing cell in which case you may be out of luck, but there's no harm in trying a long as you do it safely.

What charger do you currently have? Do you have a cell balancer like the ISDT BG-8S or FlyRC type? There's a ton on knock off out there by many other brands.

The process for recovering a battery below 3v is to balance it and charge it at a very low current. A good smart charger will also indicate the cell's impedance which is helpful in seeing if the battery is damaged. The impedance should be similar across all cell, if not it will result in an uneven discharge and an unreliable battery. A 2-5ohm difference is ok but anymore and further testing should be done. It is very important that you do not leave the battery unattended while you charge it. The current must remain around 120mA or lower. If there is damage to the battery, the current can spike up sharply and quickly resulting in a high current situation, burst cell and even a fire. The good news is that if the cell is ok, it will take the low current charge and slowly get past 3v. I usually unplug the charger at 3.2-3.4v and give the battery another pass on the balancer before charging the rest at 1C. If it all worked according to plan, your battery should be ok. You will not be able to trust it during the first couple flights as the low cells may sag abnormally quick if there is permanent damage so be careful.

Thank you very much. I'll be honest my current charger is awful it's an eachine one which is why I've brought the ISDT Q6 nano one to replace it. Once the ISDT one turns up I'll have a go slowly charging it and see what happens.

I've put a link to the eachine one as I have a couple still. Do you reckon they're safe to use on my working batteries or is the best option to bin them?

[£8.74 33% OFF]Eachine Wizard X220S FPV Racer RC Drone Spare Part 4S 14.8V Battery Charger RC Parts from Toys Hobbies and Robot on banggood

https://banggood.app.link/1Tf7Vgeu0db

 

[droneguy]

Do not attempt to charge this battery with that charger!!!! you will blow something up in a high current situation. This charger has no over-current limit protection.

 

[Eachine98379872]

Do not attempt to charge this battery with that charger!!!! you will blow something up in a high current situation. This charger has no over-current limit protection.

Do you think it's ok to charge my good batteries with it?

 

[droneguy]

You can but I personally wouldn't trust a $10 charger with a LiPo battery. There is too much that can go wrong without the proper safety features of a good charger.

 

[droneguy]

Thank you very much. I'll be honest my current charger is awful it's an eachine one which is why I've brought the ISDT Q6 nano one to replace it. Once the ISDT one turns up I'll have a go slowly charging it and see what happens.

I've put a link to the eachine one as I have a couple still. Do you reckon they're safe to use on my working batteries or is the best option to bin them?

[£8.74 33% OFF]Eachine Wizard X220S FPV Racer RC Drone Spare Part 4S 14.8V Battery Charger RC Parts from Toys Hobbies and Robot on banggood

https://banggood.app.link/1Tf7Vgeu0db

I see you bought the Q6 nano. Hopefully you are aware this one needs and external power supply. ToolkitRC make a couple brick style power supplies that are ok but there are tons out there. Just make sure you don't go to small since the Q6 is 200W