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Lifepo4 will not charge or discharge

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pault

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May 28, 2021
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Hey all,

Ive got a 100AH Ampere time Lifepo4 battery. It reads ~12.8v. When a load is connected it drops to 5v, will not accept a charge from multiple working chargers,

I tried connecting chargers and then also connecting a dc power supply set to 14.2v. The charger will kick on but immediately goes into float charging.

Bad BMS?
 
As far as load goes, im just connecting an inverter. drops to 5v when connected:

The chargers Im using.

Amazon.com: 14.6V 6A Charger 14.6V LiFepo4 Battery Charger for 4S 12.8V 14.4V LiFepo4 Battery Charger Smart Charger with Crocodile Clip : Electronics

Buy 14.6V 6A Charger 14.6V LiFepo4 Battery Charger for 4S 12.8V 14.4V LiFepo4 Battery Charger Smart Charger with Crocodile Clip: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
 
pault said:
I tried connecting chargers and then also connecting a dc power supply set to 14.2v. The charger will kick on but immediately goes into float charging.
Click to expand...
This may be part of the problem. You should just use the AIMS charger. Make sure it is set to LiFePO4 and let it charge until it holds over 13.45V.
Connecting the power supply may confuse the AIMS charger: when it sees 14.2V, it is probably doing as it is set to go to float as it should.

If you cannot get more than 12.8V, connecting an inverter will quickly pull the voltage down to where the BMS cuts off, as it should.

Sorry, that's all i got.
 
The AIMS charger will not turn on at all when connected, nor will my other charger FWIW.

I got the idea of kicking the charger on with the power supply via tis video

The difference between my battery and his is that my power supply will not push any AMPs when connected to the battery.
 
The inverter input capacitors may be overloading the battery with the BMS detecting over current. Use a precharge resistor.

Once you have woken up the battery, test the battery voltage off charge , expect 13.4 volts or over, for a fully charged battery.

Regarding no amps flowing, if the charge volts are too high the BMS may shut down the charge path due to cell over volts.

If a charger goes to float volts perhaps the battery is fully charged.

Mike
 
pault said:
The AIMS charger will not turn on at all when connected, nor will my other charger FWIW
Click to expand...
Please verify you are connecting + to+ and - to -.

With ONLY the Aims charger connected to the battery, nothing? Connect it first, then power on.
 
TomC4306 said:
Please verify you are connecting + to+ and - to -.

With ONLY the Aims charger connected to the battery, nothing? Connect it first, then power on.
Click to expand...
correct, connect aims charger. with charger unplugged. turn the switch on. nothing.

  1. Battery sitting on a counter all alone. Battery Voltage == 12.85v
  2. Attach AIMS Charger (charger unplugged). Battery Voltage == 4.18v
  3. Plug in AIMS charger, attached to battery. Battery Voltage == 4.18v
  4. Turn On AIMS Charger via switch. Nothing happens. Battery Voltage == 4.18v
  5. Apply 14v leads from power supply to battery terminals, (charger and battery state same as step 4)
    1. AIMS Charger kicks on and measured voltage == 14.45v
    2. Remove leads from power supply. measured voltage == 14.45v
    3. ~10 seconds later charger switches to float mode (green light solid, yellow light flashing) measured voltage 13.56
Can we also assume im a moderately intelligent individual who is "connecting + to+ and - to -"?
 
That's a standalone Ames charger correct? Not an inverter charger. What happens if you don't connect the charger and only connect the power supply?
 
When you connect to an inverter the battery may be overloaded, the BMS shuts down the charge path but the voltage will show a value slightly lower than a typical reading, by about 0.5 of a volt .
In the above statement after wake up the battery reads 13.56, that's fully charged.

I guess you then connect to the inverter, this gets you to stage 1 on the sequence.

As suggested you need a precharge process for the Initial connection to the Inverter.
 
there is no inverter except that small one i posted about in the first post that was only a test. can we remove it from the equation. im going to run with "the BMS is toast", idk or care why at this point. I do appreciate all the help though guys
 
When you connect that charger unplug from the wall to the battery and it draws the battery down to four volts it should not do that. Hook up the power supply all by itself to the battery and see what that does. That's not in your list of troubleshooting
 
Plug the power supply in disconnected from the battery set the voltage to 13.8 turn off the power supply leave it plugged in connect the battery turn on the power supply. What happens
 
mikefitz said:
When you connect to an inverter the battery may be overloaded, the BMS shuts down the charge path but the voltage will show a value slightly lower than a typical reading, by about 0.5 of a volt .
In the above statement after wake up the battery reads 13.56, that's fully charged.

I guess you then connect to the inverter, this gets you to stage 1 on the sequence.

As suggested you need a precharge process for the Initial connection to the Inverter.
Click to expand...
It's a $35 Walmart modified sine wave inverter. I doubt that that is the problem with a 100 amp hour battery
 
TomC4306 said:
When you connect that charger unplug from the wall to the battery and it draws the battery down to four volts it should not do that. Hook up the power supply all by itself to the battery and see what that does. That's not in your list of troubleshooting
Click to expand...
Was done, yep. PS set at 14v connected to the battery terminals does nothing. Will not push any amps. Like the battery resists it
 
TomC4306 said:
Plug the power supply in disconnected from the battery set the voltage to 13.8 turn off the power supply leave it plugged in connect the battery turn on the power supply. What happens
Click to expand...
 

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