I have a lot of old camera batteries lithium 3.7 V rechargeable accus (1s), because such handheld cameras keep dying due to lens failures (lots of sand and wind here).

I want to be able to reuse those batteries for something useful (just any projects that need rechargeable small batteries but do not require high power or capacity).

My question is: do I need to add a separate battery protection circuit to any device I would make that use those batteries? Or do they have a battery protection circuit build in?


From a cannon camera which had a 2s battery (7.2 V) I noticed that one had a battery protection circuit build in, and they where charged using an external charger so I could use them normally. With these 1s batteries however I couldn't safely open them to check if they have protection circuits inside so I didn't open them. I tried to measure the voltage a camera gave when charging it, connected to a power cable(to see if it gave a voltage over 4.2 V since that would indicate a bps has to be in the battery) but it would use the sensor pin to determine if it should charge or not, and when the battery was connected I couldn't measure the voltage since then it shows battery voltage. I couldn't find datasheets for the specific batteries I have.

So currently I have 2 main options left to figure it out, one was to try and solder 2 wires to the camera board to connect the ground and T pin of the battery to the board without connecting the + pin, but that can easily go wrong and is a lot of work since I need to set up my soldering place first, and I would need the right weather for it. The other was to ask it here, since most such batteries seem to all follow a standardized principle, replaceable 1s camera batteries, so there might be someone who happens to know what is inside such batteries.

  • 1
    \$\begingroup\$ What's a "cannon camera"? I've used shot cameras when shooting trap, is it something like that? \$\endgroup\$ May 22, 2023 at 19:42
  • \$\begingroup\$ ”With these 1s batteries however I couldn't safely open them to check if they have protection circuits inside so I didn't open them.” Good lad! Google “spicy pillow” to get an understanding of what can happen if you open a battery. \$\endgroup\$
    – winny
    May 22, 2023 at 20:44
  • \$\begingroup\$ a cannon camera is a camera from the brand cannon. and a accu turning into a spicey pillow indeed isn't good, even worse if instead it directly turns into a fire fountain. \$\endgroup\$ May 23, 2023 at 13:18

1 Answer 1


You can use this LiIon-cells for your projects!

If they have a third pin (NTC-resistor), then they must have a charging electronic. This thermal pin is not needed for charging if the current is low.

The electronic is a simple under/over-voltage protection, but you have to use a real charging electronic to load the LiIon-cell. This electronic is only for the case of an error as last line of defence!

  • My cheap way to get a matching voltage with this cheap charging-modules:

I use the TP4056 charger-module with the protection-chips (3 chips on the module) to load my LiIon-cells.

This module is charging the cell till it reaches 4.2V, but this is to much for long term devices. The high voltage of 4.2V is destroying the electrodes of the cell. I want to load my cells only till they have around 4.0 Volt. So I reduce the charging current to 70mA and added a 3A Schottky diode, which create in this way a voltage drop of very exactly 200mV.

If the current is high, for example 100mA at the end of the loading process (if it is set to 1000mA loading current), then the voltage drop over the diode is higher and the cell only reaches around 3.85 Volt.

This is a cheap and fast solution to reduce the cell-charging-voltage, but it depends on the Schottky diodes and their voltage drop.

TP4056 modification

  • \$\begingroup\$ I like the reducing of the maximum charge voltage, due to the same reason of that last 0.X volts both on the high and the low sides contibute only a small amount to the capacity but greatly reduce lifetime(so often actually after a few times you would have the same capacity as when you just directly used it safer). but since there is voltage protection is there a real danger in not using a special charging cirquit(when charging at a quite low current), or is it actually really not recommended, since I noticed many ultralight rc planes just charge at 5v and rely on the buildin chip \$\endgroup\$ May 23, 2023 at 13:29
  • \$\begingroup\$ that last part is just for extra info, or for very seciffic cases that might happen, II see that a dedicated charging cirquit can be desirable overall due to many reasons \$\endgroup\$ May 23, 2023 at 13:32
  • \$\begingroup\$ @TeDvanLoon - You should use a charging device. 1. this electronic what is inside of this cells stopps charging at ~4.35V sometimes and this is very close to burn&destruction, this voltage should never be reached. 2. The protection electronic has no current limitation. LiIon-cells should be loaded with maximum 1C (load a 1Ah cell with max. 1A). But to prevent the building of Lithium dendrite growing, use so low current as possible. \$\endgroup\$
    – MikroPower
    May 23, 2023 at 13:44
  • \$\begingroup\$ @TeDvanLoon - The charging must be controlled with a external voltage and current regulation. Discharging is often possible with a high current, but charging is critical. This dendrites can (and will) destroy the separation layer between the electrodes and cause to internal discharge or destruction of the cell if the loading current is to high. \$\endgroup\$
    – MikroPower
    May 23, 2023 at 13:52
  • \$\begingroup\$ thanks, for the clarification, 4.35v indeed seems way to high. I might still have some charging cirquits laying around, and otherwise will order some(first gotta check my drawers since often I still have parts from old projects). \$\endgroup\$ May 23, 2023 at 16:46

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