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opinion:frater_secessus:lifepo4_charging_voltage [2023/06/28 23:12] frater_secessus [why the problem occurs] |
opinion:frater_secessus:lifepo4_charging_voltage [2024/02/10 11:33] frater_secessus [the full process13.6v example |
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- | ====== Problems caused by excessive | + | ====== Problems caused by lithium charging profiles ====== |
+ | |||
+ | You'd think that a " | ||
+ | ===== excessive charging voltage ===== | ||
[[https:// | [[https:// | ||
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* voltages in the system are spiking, perhaps tripping your inverter | * voltages in the system are spiking, perhaps tripping your inverter | ||
- | It's fairly common for **excessive charging voltage** to cause these symptoms. | + | It's fairly common for **excessive charging voltage** to indirectly |
- | ===== TLDR ===== | + | ==== TLDR ==== |
- | If this is the problem then reducing the charging voltage | + | If excessive charging voltage |
- | [[[opinion: | + | [[opinion: |
- | ===== the full process ===== | + | |
+ | ==== the full process ==== | ||
- | | + | |
- | - observe for a few days. Charging will be slower and may not finish by sundown((you may have to define or increase an Absorption/ | + | |
- | - if they do clear up you can start to raise the charging voltage back up gradually (13.65v, 13.7v, 13.74v, etc) or you can leave it low. {note from secessus: | + | - observe for a few days. Charging will be slower and may not finish by sundown((you may have to define or increase an Absorption/ |
+ | - if symptoms | ||
- if it starts acting up again drop charging voltage back down a notch or two | - if it starts acting up again drop charging voltage back down a notch or two | ||
- | ==== why lower-voltage charging works ==== | + | === why lower-voltage charging works === |
- | LiFePO4 will fully charge at voltages as low as the mid-13s, but it will take more time at lower voltages; | + | LiFePO4 will fully charge at voltages as low as the mid-13s, |
- | * ≥14.0v will charge to 100% SoC with zero absorption: hit the voltage setpoint and //stop//. Cell voltages tend to diverge as charging voltage increases. | + | * ≥14.0v will charge to ~100% SoC with zero minutes of absorption |
- | * 13.8v will charge to 100% SoC with token Absorption (10-30 minutes) and cells tend to stay in balance. | + | * 13.8v will charge to ~100% SoC with a small amount of Absorption (10-30 minutes?) and cells tend to stay in balance. |
- | * 13.6v will charge to 100% SoC with several hours of Absorption | + | * 13.6v will charge to ~100% SoC with several hours of Absorption |
- | * 13.4v will // | + | |
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- | + | ==== why the problem occurs ==== | |
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- | ===== why the problem occurs | + | |
{{ https:// | {{ https:// | ||
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- the BMS sees the runaway and shuts down charging to avoid damaging the cell((if the charging is gentle enough the BMS may be able to stop the runaway by " | - the BMS sees the runaway and shuts down charging to avoid damaging the cell((if the charging is gentle enough the BMS may be able to stop the runaway by " | ||
- which stops **all** charging of the battery((and a voltage spike because the charger "went away", from the charger' | - which stops **all** charging of the battery((and a voltage spike because the charger "went away", from the charger' | ||
- | - if the cell imbalance is bad enough the battery can't charge anywhere near full because the misbehaving cell is causing | + | - if the cell imbalance is bad enough the battery can't charge anywhere near full because the misbehaving cell is causing |
So we ease up on charging which encourages the cell to stay in line with the others, which allows for a full battery charge. | So we ease up on charging which encourages the cell to stay in line with the others, which allows for a full battery charge. | ||
- | The bigger question is this: [[electrical: | + | The bigger question is this: [[electrical: |
- | ===== further reading | + | ==== further reading ==== |
* [[electrical: | * [[electrical: | ||
+ | |||
+ | |||
+ | ===== lack of pseudo-float ===== | ||
+ | |||
+ | So your charge controller isn't charging even though battery state of charge is dropping? | ||
+ | |||
+ | This can be intentional behavior, caused by a Li profile that | ||
+ | |||
+ | - charges to a high voltage (see above) | ||
+ | - then allows the battery to discharge until it hits the [[electrical: | ||
+ | - at which point it charges to the high voltage again... | ||
+ | - rinse and repeat until the sun goes down | ||
+ | |||
+ | During the discharge stage the controller will appear to stop working. | ||
+ | |||
+ | To avoid this problem. configure a " | ||