Hi I have a SF 3.7v 1000mah lipo and charger board.
Also I have a bluetooth transmitter on a piece of kit I abs cannot destroy. The case is marked 3.7v 450ma, internally its blue shrink wrapped flat cell marked 3.7v 3.7wh terminated with a jst of opposite polarity of SF cell. it tests at 3.7v, probably isn’t fully charged. since I dont know the cell chemistry, is my device at risk from the extra 0.5v the SF lipo will start at if I swap these cells after fixing the polarity? (this is all as I cannot charge the original and want to swap with cell I can charge easily) thanks in advance
I’m not certain what it is that you are asking. Does your system have to run on 3.2V maximum, or is there any tolerance? Do you know if there is an onboard voltage regulator on your target module?
If the battery is rated for 3.7V and tests at 3.7V, then it is most likely fully charged. Every battery has tolerances, so a full charge state could be 3.8V, 3.9V or I’ve even seen 4V.
My strongest suggestion would be that you should double check the datasheet for your module for Absolute Maximum Values. That should tell you the highest your voltages can be without high risk of damage.
I cannot identify the original battery charging regulator, it has no markings at all so I can get no data sheet for it or the module itself, access to which is limited to the underside traces so I can t do any detective work there either. All lipo’s I’ve seen are silver wrapped. This one is blue with no obvious protection circuitry. if it’s a li-ion cell nominal at 3.7v (it’s not fully charged) will the initial 4.2v before drop to nominal 3.7v of my replacement lipo cause damage or is the 0.5v diff too small to matter in modern eqiup? it’s an Italian thing, they’re not working so I cant get the info I need or a replacement.
If we can’t identify the circuit that will be powered from the battery then there is no way we can definitively guarantee that the battery will work for your uses. I would suggest using a variable power supply to try testing your system before integrating the LiPo battery.