Accidental overcharge, what do I do now?

[denweny]

Big facepalm today. So I overcharged my lifepo4 battery to 18.8v today (4.7v per cell) with a variable dc charger to top balance it.
The charger was set to 3.7V 5A, but then came back 6 hours later to 4.7 0A. I screwed up.

Is my battery fubar'd now? No swelling or hot temps so far. The voltage is slowly dropping. 16v atm

 

[Picasso]

suck it back down dont let it sit long overcharged

 

[denweny]

Good idea, but I don't have any devices that can eat up 16v atm. What should I buy?

 

[Pierre]

Use 2x car halogen headlamp bulbs in series , then use one when voltage gets to about 14,5v.

 

[Gazoo]

Big facepalm today. So I overcharged my lifepo4 battery to 18.8v today (4.7v per cell) with a variable dc charger to top balance it.
The charger was set to 3.7V 5A, but then came back 6 hours later to 4.7 0A. I screwed up.

Is my battery fubar'd now? No swelling or hot temps so far. The voltage is slowly dropping. 16v atm

How long did it take to drop to 16 volts? By the time you are able to get what you need to bring the voltage down the batteries might be at 14.6 volts or less. Good thing there was no swelling or venting. I think that's a good sign.

 

[denweny]

1-2 hours to get to 16v, now it's 15.78. Since it's midnight, It'll be at least 10 hours before I hit the store.

 

[denweny]

Can anyone explain the worst or most probable case? I'm hoping that I've only lost at most 50% of the 4000 cycles or have 5 years left if I'm correct.

 

[Pierre]

Use 2x car halogen headlamp bulbs in series , then use one when voltage gets to about 14,5v.

‘Borrow‘ them from your wife’s car

 

[Gazoo]

1-2 hours to get to 16v, now it's 15.78. Since it's midnight, It'll be at least 10 hours before I hit the store.

I think you lucked out. So by now they are around 3.9 volts per cell. They should be at there resting voltage before 10 hours. Personally I don't know what the effect on the lifespan is. You said they didn't swell up or do anything bad. After they have reached their resting voltage do a capacity test on them. But get a BMS before you do anything else.

 

[GMB]

Did you top balance with the cells in series or parallel?

Would be good to know how this happened so other members don't make the same mistake. Can you explain how you deviated from the steps this video? Thanks.

 

[denweny]

Good point. I decided to top balanced in parallel but I got a little greedy and set the voltage to 3.7 5A. This turns out to be the 100% setting of my dc variable charger, which increased the voltage as the battery also reached a higher voltage.

tl;dr: stick with 3.6V b/c the charger won't stop increasing the voltage

EDIT: used the UNIROI 5A dc variable charger https://www.amazon.ca/dp/B07D279WR8/ref=emc_b_5_t

 

[denweny]

I think you lucked out. So by now they are around 3.9 volts per cell. They should be at there resting voltage before 10 hours. Personally I don't know what the effect on the lifespan is. You said they didn't swell up or do anything bad. After they have reached their resting voltage do a capacity test on them. But get a BMS before you do anything else.

Do you know where I can get a capacity tester fast and cheap? Aliexpress will take weeks and Idk any retailers with testers either

 

[GMB]

Can you post a link to your charger?

I'm not really understanding. I have the same charger Will is using in his video. When I set it to 3.6 volts, (and let's say the battery is at 3.2 volts when I start charging) the amps keep dropping over time until it reaches zero and the battery is at 3.6 volts. I can walk away and come back in a week or watch it step by step and it's all the same; it won't go over 3.6 volts. So I am trying to understand why yours was set to 3.7 but kept charging to 4.7? Thanks again - this will really help out other members as there have been several post like this in the past few months.

 

[Gazoo]

Do you know where I can get a capacity tester fast and cheap? Aliexpress will take weeks and Idk any retailers with testers either

Lots of them on Ebay. I found one on Amazon not as cheap as aliexpress of course.

Amazon.com

 

[denweny]

Can you post a link to your charger?

I'm not really understanding. I have the same charger Will is using in his video. When I set it to 3.6 volts, (and let's say the battery is at 3.2 volts when I start charging) the amps keep dropping over time until it reaches zero and the battery is at 3.6 volts. I can walk away and come back in a week or watch it step by step and it's all the same; it won't go over 3.6 volts. So I am trying to understand why yours was set to 3.7 but kept charging to 4.7? Thanks again - this will really help out other members as there have been several post like this in the past few months.

I got a different brand at 5A: https://www.amazon.ca/dp/B07D279WR8/ UNIROI 5A
I set mine to 5A 3.7V b/c I was greedy and wanted to charge it faster as I was expecting it to take days from 3.2v.
The dial only allows you to adjust the amperage which also increases the voltage proportionally. I should've gotten the same model as you and will

 

[Sabre36]

Can you post a link to your charger?

I'm not really understanding. I have the same charger Will is using in his video. When I set it to 3.6 volts, (and let's say the battery is at 3.2 volts when I start charging) the amps keep dropping over time until it reaches zero and the battery is at 3.6 volts. I can walk away and come back in a week or watch it step by step and it's all the same; it won't go over 3.6 volts. So I am trying to understand why yours was set to 3.7 but kept charging to 4.7? Thanks again - this will really help out other members as there have been several post like this in the past few months.

It's most likely because the OP adjusted the voltage when connected to the load. A variable power supply voltage needs to be set at 0.00A load with the cells or bank disconnected.. When connected to the load, if you adjust the voltage, it will not be accurate when the battery drops to low amperage. Voltage drop in the wiring also needs to be accounted for and cheap power supplies do not offer a dedicated voltage sensing circuit like higher quality units do. Use the largest wire that will fit on the power supply terminals and keep them as short as possible. Adjust your peak voltage first, using a an accurate DVM to confirm it, as many of these are pretty sloppy, then connect the output wires to the battery or cells. Then do not touch the voltage dials when charging.

 

[Sabre36]

I got a different brand at 5A: https://www.amazon.ca/dp/B07D279WR8/ UNIROI 5A
I set mine to 5A 3.7V b/c I was greedy and wanted to charge it faster as I was expecting it to take days from 3.2v.

Voltagee does not speed the charging here. The 5A limit of the charge source is what controls the speed.

The dial only allows you to adjust the amperage which also increases the voltage proportionally. I should've gotten the same model as you and will

The course and fine voltage adjustments will absolutely work, but they need to be set into 0A load before the cells are connected.. Fine or course voltage cannot be set when connected to the battery or cells, otherwise the voltage on the display will just represent battery voltage, and you will have no idea where it is actually set. Adjusting the voltage, while connected to the load, can be damaging to the cells, as you've now learned.

 

[Ampster]

Voltagee does not speed the charging here. The 5A limit of the charge source is what controls the speed.

It does if the power supply is in the constant voltage stage with Amps tapering (below 5A) and the user increases the voltage. In that scenario the power supply will go back into constant current mode which will be at a higher current (5A) than the previous current which was tapering.

I do agree the likely culprit is adjusting the voltage with a load. The actual setting was obviously in the 4.7 volt range instead of 3.7 volt which the user thought it was set to.

 

[Ampster]

Fine or course voltage cannot be set when connected to the battery or cells, otherwise the voltage on the display will just represent battery voltage, and you will have no idea where it is actually set.

I think this is the critical issue and probably the cause of many cases of overcharging. One power supply I owned had separate voltage leads and a button that could remove the load to check settings. Even that can lead to mistakes because one time I forgot to push the button and reconnect the battery. However the only consequence of that mistake was it was going to take longer.

That reminds me of what one poster said a while ago about patience. The lack of patience, or conversely the desire to speed up the process may have contributed to the overcharging events reported here. I'm not trying to be critical of anyone, but we are all human. As much experience as I have had, I recently over charged 8 cells I had in a parallel string.

 

[Xerxes]

As much experience as I have had, I recently over charged 8 cells I had in a parallel string.

Now its your turn to tell the story
-I wonder
-The forum wonders
-The whole world wonders....

Pray tell the tale of the overcharged "8 cells in parallel"