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| 12V DC UPS |
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| tom66:
I did something similar for our CCTV DVR. Modded the power supply to output 13.2V instead of 12V (within the +10% range for the ATX hard drive) which kept a small lead acid battery semi-charged. It's sufficient to keep the system going for about half an hour in a power cut, and it backpowers the cameras too through the 12V socket. The only problem I've found is the hard disk is the first thing to cut off, but if the power comes back before the DVR dies, it takes a while before the DVR detects the HDD again. I need to add a 'UVLO' circuit to properly reset things. |
| NiHaoMike:
--- Quote from: beanflying on July 25, 2022, 05:58:44 am ---Number of times you have FALSELY posted about BMS circuitry and charging Lithium cells is now +1. Please go learn once and for all how Lithium batteries are charged and a tip that is NOT USING A BMS. STOP IT ! Lithium Batteries are a multi step charge process so that is neither just constant current or using a Diode on a random power supply as some sort of :bullshit: limiter. --- End quote --- https://www.electronicsweekly.com/market-sectors/power/float-charging-lithium-ion-cells-2006-02/ --- Quote ---In float charging, current entry beyond full charge is prevented by choosing a charge voltage less than or equal to the voltage naturally produced by the cell at full charge – which depends on the cell’s exact electrochemistry and temperature. “It is all related to battery voltage,” says Robin Cloke, UK MD of GP Batteries. As a general rule of thumb, “if you choose around 4.0V it is fairly safe for the cell”. --- End quote --- |
| beanflying:
--- Quote from: NiHaoMike on July 25, 2022, 12:46:31 pm --- --- Quote from: beanflying on July 25, 2022, 05:58:44 am ---Number of times you have FALSELY posted about BMS circuitry and charging Lithium cells is now +1. Please go learn once and for all how Lithium batteries are charged and a tip that is NOT USING A BMS. STOP IT ! Lithium Batteries are a multi step charge process so that is neither just constant current or using a Diode on a random power supply as some sort of :bullshit: limiter. --- End quote --- https://www.electronicsweekly.com/market-sectors/power/float-charging-lithium-ion-cells-2006-02/ --- Quote ---In float charging, current entry beyond full charge is prevented by choosing a charge voltage less than or equal to the voltage naturally produced by the cell at full charge – which depends on the cell’s exact electrochemistry and temperature. “It is all related to battery voltage,” says Robin Cloke, UK MD of GP Batteries. As a general rule of thumb, “if you choose around 4.0V it is fairly safe for the cell”. --- End quote --- --- End quote --- 4V is 'safe' for most Lithium options BUT you do not get there by ANY METHOD in your initial post! Don't randomly Google for answers YOU WANT to suit your argument instead do some actual reading on how done safely to suit the Lithium Technology in question. Start with understanding what a BMS board is and is not. |
| tom66:
Float charging Li-ion batteries is simply not possible: you cannot apply a fixed 4V if the battery is at say 3.5V, the current drawn during charging will be excessive which will overheat the cell. You need both current limiting and voltage limiting. Now, you can modify a standard li-ion charger IC with an external comparator so that it shuts off once the cell goes over e.g. 4V, which will create the 'effect' of float charging, but the result will be that the charger cycles on and off around that point, so not really float charging. It will certainly extend the cell's lifespan, the rule I have heard is doubling calendar life for every 0.1V less than 4.25V. It is NEVER permissible to charge a li-ion cell with only a resistor or simple current limiter, cell voltage will increase until the cell is destroyed, if the current is high enough this may well result in thermal runaway. |
| Siwastaja:
--- Quote from: beanflying on July 25, 2022, 05:58:44 am ---Number of times you have FALSELY posted about BMS circuitry and charging Lithium cells is now +1. Please go learn once and for all how Lithium batteries are charged ... Lithium Batteries are a multi step charge process so that is neither just constant current or using a Diode on a random power supply as some sort of :bullshit: limiter. --- End quote --- How about you dropping your attitude and go learn how lithium ion batteries are charged. But if you can't even get the name (lithium ion; lithium batteries are a different thing) right, I guess there is very little hope for you. I see no big issues in NiHaoMike's suggestion. Of course, he leaves out the detail what he exactly means by "BMS". But he often leaves out details to be worked on. Clearly, you don't have any idea about the "multi-step process" you are talking about. Also the battery does not know or care if current is limited using a resistor or something more fancy, and I think it's quite revealing you can't understand even this. In the future, you might want to consider this: if you think someone is giving poor or dangerous advice, learn the thing first, and then properly explain what is wrong. And remember, to be able to teach others, you need to have quite solid understanding. |
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