I have one of these:
Hooked up to this:
Weirdly, the charger doesn't charge the battery over 92%. But this charger:
charges the battery to 100%.
For both, I am checking the battery with this:
Any ideas? It's not a big deal, mostly just a curiosity.
When I hook a DMM onto the battery when charging with the BQ24074 charger, it caps the voltage at 4.14V, rather than the Waveshare one, which caps the voltage at 4.22V.
I'm guessing the BQ24074 is capping too low as I believe these batteries are fully charged at or around 4.2V. I wonder if this is due to a resistor somewhere in the circuit being mildly out of spec? Maybe the ITERM resistor (R2 on the schematic, which is 9.99k [10k] currently)?? The max this resistor can be per the datasheet is 15k. What would happen if I changed it to 8k?
Datasheet:
Schematic:
Datasheet gives:
In the other input current limit modes (EN1 ≠ EN2), the termination current value is calculated as:
ITERM = 0.03 × RITERM/ RISET
So if you have ISET 1A (1k resistor)
and you wish to terminate at 0.05C, 200mA for 4000mAh battery
then the RITERM should be 0.2*1000/0.03 = 6.7k ohm.
So try with lower value resistor if you feel that's the problem.
But if the charge voltage doesn't go above 4.14V anywhere in the cycle, your problem is somewhere else. What is your input voltage?
The input voltage is 6v 5A
So are you suggesting 6.7k ohm resistor?
Depends... Not to charge battery up to 100% has benefits as well, but if you want full battery try if 6k8 resistor change something.
If the problem is charge voltage, it doesn't help, neither hurt.
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That is a good set of parts to experiment with. On this forum are topics that have investigated these types of components in great detail. There are a lot of components sold that are inferior.
It might be interesting to see if the maximum voltage it's charging at after it shifts into constant voltage mode is 4.2v or 4.14V. In other words, is the problem that the charging voltage is too low, or that it's not charging long enough (which would be a termination issue). But I don't know if either can be modified. I have a variety of TP4056 chargers, and they vary a good bit in the voltage the battery is left at after termination - just part to part variation I think.
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