![]() This can lead to a battery pack showing 16v, but only 4 of the cells actually working and hence, very likely, the FETs being off. After measuring individual cell voltages, there is a massive difference in cell voltages. After going thru about 30 of them, I've noticed that the previous owner had already tried jumping the batteries which involves bypassing the BMS. I recently picked up 100+ 18v batteries that all "failed". I will say that failed 18v packs usually have just 1 cell that is damaged if any. I'm not exactly sure how this occurred, but I'll be trying to figure that out tonight. Last night while comparing a repair and functioning battery, to a repair and failed battery, the failed battery came back to life after taking a few voltage measurements and using the continuity checker on the FETs. As mentioned previously, if the FETs are off, the Batt- and GND do not connect, no current will flow. Reassembled, and still a number of the batteries failed to work. I disassembled the pack, recharged/tested/recharged the cells (all still had great capacity). I presume the internal battery circuits will take care of cell balancing, but I suggest checking the individual cell voltages periodically. Might want to put a ~4.7 K resistor in series for protection. I suggest applying between 1 and 2 volts. When the voltage was 0.5v or higher, the main +/- "opened" and it was possible to charge the battery. It was linear from 0.5 to 2.0 volts suggesting a pure resistance. The battery continued to charge when T2 was disconnected, but the light on the charger was red. Voltages with a half-charged battery inserted: I couldn't read the numbers well, my best guess is 10266A J1A4B Two 3-lead semiconductors, I presume they are MOSFETs. Lots of pictures and information on the web so I won't repeat. Maximum current of AH / 4 is safe, more might be possible if you know the battery specificationsĬharge in a fireproof container and don't charge unattended. Maximum of 21 volts (better is 20.5) for a 5-cell battery Use at your own risk: I suggest the following: If the yellow LED has started flashing, the charger is defective. Some models use a yellow LED to show that the battery is charging. It becomes solid and stable when the battery is fully charged. Warning: Using the following could bypass the thermal and electrical protection circuits. With many Ryobi chargers, the yellow light flashes when the battery is charging. I did a teardown on the battery and a (borrowed) charger and found out how to bypass the Battery Management System (BMS). Hope this helps.I bought a Biswaye P103 (Chinese) battery to power my Ryobi drill, but when I tried to charge it using my bench power supply, it wouldn't work. For your approach, you would need to remove the cells if both the stronger and weaker cells come from the same battery pack. At the end of the day, you would likely have 2 depleted cells.Įd’s original intent was to rebalance the cells without removing them from the Ryobi battery. For item c), I would not be surprised if it takes an extra Wh to charge an cell by 2Wh. For item b), the resistors would dissipate <0.1Wh in one hour at say 0.3 amps. For item a), the weaker cell would need about 2Wh charging from 3.6 to 3.8V. That energy would be distributed to a) the charging of the weaker cell, b) the heat load of your resistors, and c) the charging inefficiencies. In your example, the 4.1V cell would lose about 1Wh of energy while discharging to 3.9V, based on what I’ve read on the internet. This lithium battery charger is capable of charging at a rate of 2.0Amps/hour meaning you can charge a 2.0ah battery in 1 hour. Cells in a Ryobi battery are normally cycled from 3.5 to 4.1V, resulting in 4.8 Wh output/cell. Kenton, you need to consider your application from the energy perspective. After reassembly, I was able to charge the battery up to about 19.8V, a bit less than usual (20.5V). In less than a half hour, all cells were charged. During this procedure, it is important to monitor the voltage across the cell. If the wire is hot, then increase the interval between sparking. This means touching the wire to the cell tab long enough to see sparks and repeat the contact every 5-10 seconds, depending on how fast the wire heats up. ![]() With the free end, I made frequent intermittent contact with the other cell tab. Aside from the 40V Lithium battery replacement, you can also find Ryobi lithium replacement batteries for your. I then attached one end of another bell wire to the other terminal of the spare Ryobi. The polarity is critical (negative-to-negative, or positive-to-positive). I connected one cell tab to one terminal of the spare Ryobi using thin bell wire (it's like speaker wire). I charged the 4 lowest voltage cell pairs, one at a time, to the same level as the highest voltage cell (3.48V) using a spare 18V Ryobi battery.
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