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Overcharge club- new member ?‍♂️

Sharky722

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May 8, 2020
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Didn't think this would happen to me but it has.
While under supervision and charging a single LF105 being impatient I cranked up the psu.
I take a reading off the multimeter we've just hit 3.42v.

The phone rings I'm distracted for about 25mins.

I return to the cell to find 4.5v on the psu ?.
Immediately disconnect and employ a resistor on the terminals, takes a further 30mins to reduce down to 3.5v.

Cell is slightly swollen and has lost 3ah on next capacity tests.

Im not taking any chances with the cell it will be discarded and replaced.

I would just like to say again if you've made an adjustment to psu while connected to load do not leave unattended EVER or when close to the knees.

RIP my cell, you were destined for great things. ?
 

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From another thread.....

Maybe I should make some of these. Cheap insurance.

1607300630534.png
 
From another thread.....

Maybe I should make some of these. Cheap insurance.

View attachment 29508
Great idea
 
To all planning to do top balancing, repeat this three times before beginning.

"I will not set unloaded power supply above 3.65v".
"I will not use small gauge power supply cables havng more than 50 mV voltage drop between power supply and cell(s)."
"I will be patient and expect to wait more then 50% AH of cell x number of paralleled cells / by power supply amps, in hours."

Sixteen paralleled, 280AH cells, at 10 amps charge current will take over 9 days! Consider that time against the total order time from China on getting a replacement for a bloated cell.
 
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NO PETS OR KIDS IN VICINITY !
That is just Asking for Murphy's Laws to be applied.
You cant put em on a high shelf out of their reach, or in a latched cabinet?
How have some of you been gettin by with bleach and drano and stuff around the house?
 
You cant put em on a high shelf out of their reach, or in a latched cabinet?
How have some of you been gettin by with bleach and drano and stuff around the house?
Maybe you have little to no exposure to Children & Pets and can't grasp the potential of what they can do intentionally or not.
Accidents happen because an opportunity exists for it to happen. Have you never heard of "Murphy's Laws" ?
 
From another thread.....

Maybe I should make some of these. Cheap insurance.

View attachment 29508

I’ve been using a circuit like that for a decade. It’s staggering how many people think it’s OK to connect a charger to a LiFePO4 cell without a high and low level voltage disconnect.

To the OP, i’m sorry you received bad advice on commissioning your battery.
 
Dont' feel bad. Many of us have been there. It is so tempting to just goose-up the voltage on a programmable PSU to get more current, and then even if set for 3.65v, find out at the end of charge, it was far greater!

RCinFLA got it right emphasizing an UNloaded voltage setting at first. And then leave it alone. This is especially important when doing "stepped" top-balance also. Disconnect, make the voltage change (preferably with a good voltage instrument, not the psu display), and reconnect for the next voltage step.

If you don't do this, and just wing it with a psu knob tweak, all it takes is one phone call to be distracted.

Sorry it happened, but is not unknown to many of us.
 
Maybe you have little to no exposure to Children & Pets and can't grasp the potential of what they can do intentionally or not.
Accidents happen because an opportunity exists for it to happen. Have you never heard of "Murphy's Laws"
Thank you sir obvious. Yeah I have no exposure to children or pets. A poor debate tactic, prefacing a post with a thinly disguised personal insult.
The point is if you have unruly misbehaving children or unrestrained pets, put your equipment on a high shelf or in a secured cabinet. You seemed to imply the solution is simply dont do it if they're "in the vicinity". If you have them, theyre in the vicinity.
 
I’ve been using a circuit like that for a decade. It’s staggering how many people think it’s OK to connect a charger to a LiFePO4 cell without a high and low level voltage disconnect.

To the OP, i’m sorry you received bad advice on commissioning your battery.

I ultimately decided not to make this dedicated disconnect circuit. Fortunately, I have a stack of GPIB programmable power supplies and used Python to manage the charging.

I cannot imagine trusting an analog off-brand low-cost power supply with an expensive battery bank.
 
And I cannot imagine trusting SOFTWARE to do the job of analog :ROFLMAO:
(Similarly, the policeman's job is to write up a report of your loss so you can give it to your insurance company.)

The things I designed, where it mattered (heated filament exposed to vacuum, hopefully) had digital setting of analog safety shutdown circuits.)

But yeah, "off-brand", "low-cost"
I have some better supplies with digital setting of voltage, and of over-voltage shutdown.
When I charged/equalized batteries with an analog bench supply I put tape over the voltage knob.
 
And I cannot imagine trusting SOFTWARE to do the job of analog :ROFLMAO:
(Similarly, the policeman's job is to write up a report of your loss so you can give it to your insurance company.)

The things I designed, where it mattered (heated filament exposed to vacuum, hopefully) had digital setting of analog safety shutdown circuits.)

But yeah, "off-brand", "low-cost"
I have some better supplies with digital setting of voltage, and of over-voltage shutdown.
When I charged/equalized batteries with an analog bench supply I put tape over the voltage knob.

The same hardware and software is used for extremely consequential tests and experiments. GPIB has been around since the 70's. My Agilent power supplies cost around $5,500 each - mainly because of the crazy focus on reliability.

A dedicated disconnect circuit can also fail - especially a custom designed 1-off. A custom circuit was simply not worth the time for me. My day job is (in-part) designing/building/testing power electronics so I could do it, but the GPIB automation approach was a LOT faster and a lot more flexible. The chances of failure are extremely low, so whatever latent risk is ok for me.

Nothing is going to be 100% reliable.
 
The cell monitor is a backup for the PSU.

Like having a high voltage disconnect as well as using the programming in a charge controller to prevent cell overcharge.

I don’t know many people that rely on the charge controller alone to protect their cells against overvoltage, but many of these same people forget about that when they connect a charger for balancing. It makes no sense to me.
 
The same hardware and software is used for extremely consequential tests and experiments. GPIB has been around since the 70's. My Agilent power supplies cost around $5,500 each - mainly because of the crazy focus on reliability.

Yes, I have the same/similar HP supplies (or maybe an earlier generation.) I haven't used them for battery charging. I assembled a test and calibration system for prototype PCBA of my employer's analytical instrument.

One thing I discovered using two outputs to make a bipolar supply like +/-10V was that during power-up sequencing, one pulled the other past ground an caused it to shut down. A clamping diode limited that, and I had to loosen over-voltage limits so they were greater than the diode drop - same voltage limit was applied to going beyond the opposite rail while output was supposed to be zero.

I've read that for these supplies a diode is needed when charging batteries so they don't dump current into its crowbar circuit. Another vendor's supply said when the diode is used, remote sense can't be. But my supplies allow sense to be up to 1V beyond the power rail, so should be OK with a low diode drop.

Do you use diodes or remote sense?


Software - I just like to get a dig in at it when I can. Some software is very well written, but so much has issues. And anything on Windows platform with GB of code, processes, updates I don't trust. Would be better to have a stable platform with real-time response. Have to offload any real-time tasks to the instruments themselves or a PXIe chassis. For fast shutdown my designs used a hardware circuit. Slow stuff like temperature rise pulled an interrupt line.
 
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