I have a battery that says it has a working current of 4.6A and rated voltage of DC 12V I need the battery to power a motor for a fan that says it has a voltage of DC 3.7V Will it work? What will happen?
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\$\begingroup\$ Welcome to EE.SE. It will work spectacularly, then definitely blow up. Use Batery Management System + Motor Driver Module suitable for your system instead. \$\endgroup\$– Unknown123Jun 3, 2019 at 18:12
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1\$\begingroup\$ This question is unanswerable without more specifics of the devices; the numbers you have posted so far are very unusual both in their values and their alleged meaning for example "working current" is most never a primary specification of a battery, but only one derived under certain conditions. Nor is 3.7v almost ever the rating of a motor, since nominal 3.7v batteries start their discharge at 4.2v... \$\endgroup\$– Chris StrattonJun 3, 2019 at 18:30
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1\$\begingroup\$ use a buck module like mini360 \$\endgroup\$– Jasen Слава УкраїніJun 3, 2019 at 19:03
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\$\begingroup\$ @ChrisStratton motors designed to be powered by a single Lipo cell are usually designated as '3.7V' motors even though the initial voltage will be a bit higher. In typical applications this small 'over-voltage' is not a problem. 12V OTOH... \$\endgroup\$– Bruce AbbottJun 4, 2019 at 0:07
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It will work until something overheats or otherwise fails. The speed of a DC motor is proportional to voltage. If a 3.7-volt DC motor is connected to 12 volts, it will try to run at 12/3.7 = 3.2 times the normal speed. The mechanical power required to drive a fan is approximately proportional to speed cubed. That means the fan will try to load the motor to about 10 times the rated operating power.
If the motor is a brushless motor, it has electronic circuitry that might limit the fan speed or current. However that circuitry is probably not designed for 12 volts input. There is no reason to expect it not to fail.