3.0 v or 3.7 v rcr123a why is that?
- Thread starter Lou Maan
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Hi Lou. I assume you are referring to LiCo (ICR) "3 Volt" RCR123A cells. These cells have two diodes installed under the positive (+) nipple. One of them drops the voltage of the cell under load to "3 Volts" (this voltage depends on a number of factors, but usually the voltage is actually around 3.2-3.6 Volts, depending on the current load applied). The second diode allows current to pass into the cell for charging purposes.
Anyway, when an open circuit voltage measurement is taken, depending on the resistance of the meter used, a fully charged cell (eg. 4.20 Volts) will either read 4.20 Volts, or ~4.00 Volts. The later voltage varies somewhat, depending on the brand of the cell and the specific diodes used. So, what your reading is either the voltage of the cell behind the diode, or the voltage with the diode. If the diode is "active", you will read the ~4.00 Volts. If the diode is not active, you will be reading the voltage of the cell behind the diode, in this example, 4.20 Volts.
If you are measuring the voltage of a LiFePO4 (IFR) cell (the "other 3 Volt" cell chemistry), and are reading 4.09 Volts, the cell has been charged in the wrong charger, and has been overcharged. Both types of "3 Volt" RCR123A cells require different chargers from each other and also from "normal" 3.6-3.7 Volt LiCo cells. LiFePO4 cells require a 3.6 Volt CV, "3 Volt" LiCo cells 4.4-4.5 Volts CV (to overcome the diode), and normal 3.6-3.7 Volt LiCo cells 4.20 Volts CV.
DO NOT ATTEMPT TO CHARGE A "NORMAL" 3.6-3.7 VOLT LiCo CELL IN A CHARGER INTENDED FOR "3 VOLT" LiCo CELLS. THESE CHARGERS WILL CHARGE NORMAL 3-6-3.7 VOLT LiCo CELLS TO A DANGEROUSLY HIGH VOLTAGE!
Any other incorrect combination will either result in under, or overcharged cells, but there is little danger involved. In the case of overcharging a LiFePO4 cell for example, it only damages the cell, there is little risk of explosion, or "venting with flame".
Hope this helps,
Oh, and welcome to CPF! :thumbsup:
Dave
Anyway, when an open circuit voltage measurement is taken, depending on the resistance of the meter used, a fully charged cell (eg. 4.20 Volts) will either read 4.20 Volts, or ~4.00 Volts. The later voltage varies somewhat, depending on the brand of the cell and the specific diodes used. So, what your reading is either the voltage of the cell behind the diode, or the voltage with the diode. If the diode is "active", you will read the ~4.00 Volts. If the diode is not active, you will be reading the voltage of the cell behind the diode, in this example, 4.20 Volts.
If you are measuring the voltage of a LiFePO4 (IFR) cell (the "other 3 Volt" cell chemistry), and are reading 4.09 Volts, the cell has been charged in the wrong charger, and has been overcharged. Both types of "3 Volt" RCR123A cells require different chargers from each other and also from "normal" 3.6-3.7 Volt LiCo cells. LiFePO4 cells require a 3.6 Volt CV, "3 Volt" LiCo cells 4.4-4.5 Volts CV (to overcome the diode), and normal 3.6-3.7 Volt LiCo cells 4.20 Volts CV.
DO NOT ATTEMPT TO CHARGE A "NORMAL" 3.6-3.7 VOLT LiCo CELL IN A CHARGER INTENDED FOR "3 VOLT" LiCo CELLS. THESE CHARGERS WILL CHARGE NORMAL 3-6-3.7 VOLT LiCo CELLS TO A DANGEROUSLY HIGH VOLTAGE!Any other incorrect combination will either result in under, or overcharged cells, but there is little danger involved. In the case of overcharging a LiFePO4 cell for example, it only damages the cell, there is little risk of explosion, or "venting with flame".
Hope this helps,
Oh, and welcome to CPF! :thumbsup:
Dave
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Thanks Dave 
Actually thanks very much. I was just about to do the !Poof! thing the next day. I thought well if it can charge a 3v battery to 4.2, surely it can charge a 4.2 to 4.2. There should be more info out there for dummies like me. You saved my anatomy. I owe you my life. Cheers and all the best!
Actually thanks very much. I was just about to do the !Poof! thing the next day. I thought well if it can charge a 3v battery to 4.2, surely it can charge a 4.2 to 4.2. There should be more info out there for dummies like me. You saved my anatomy. I owe you my life. Cheers and all the best!
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