Hi all, new to this forum and looking a wee bit of advice please.looking to create a power pack from 18650 3.7v batterys to run a 12v heated vest. When fully charged Im getting 4.2v per battery so 3 in series is giving me 12.6v, that much is fine. When I connect heated vest, current drops voltage to 10v, which is not enough to power vest. OK, if i connect a 4th battery in series, giving 16v, connect vest and current drops to 13.8v which is great for running the heated vest. Is this good practice or should I add more batteries in parallel to provide a lower voltage?
Thanks in advance.
Kevin

 

We need to know the specifications of the heated vest in order to give a factual answer. Otherwise we can only guess what will work

 

You need to match the load to the battery and vice versa.
Firstly, determine the current requirement of the vest.
Determine how long you need the vest to be constantly heated.
Multiply the current consumption with the number of hours of operation.
For example, if the vest takes 1A and you need to heat the vest for 1 hour, the current-time calculation is 1Ah or 1000mAh.
A 2000mAh @ 12V battery would be suitable in this case.

 

vest draws 3.5 amps roughly and the 18650 batteries are 3200mAH.

 

With those figures the battery can maintain the vest for about 40 minutes before it is dangerously over discharged.

 

With those figures the battery can maintain the vest for about 40 minutes before it is with the dangerously over discharged.

thanks, but should i run with the 4 18650 in series with 16v to start or have 6 18650 ,3 series with 2 parallel with 12.8v to start with?

 

3s2p would give you almost double the run time 6.4 amp hours.