# How long could 4 series connected 18650 Li-ion batteries be used to produce a constant 14V 3A supply from a 14V 2Hz pulse train, before failing?

How does switching from charging to discharging at high amperage affect the battery life? The batteries would be fed by the 2Hz pulse train whenever they were supplying power, so they would always be operating at a fully charged state.

• I think this is such an unusual use case that you are going to need to do some experiments and find out for yourself. Your statements are also contradictory...how can the battery ever be discharging if it is always "at a fully charged state"? Commented Sep 22, 2019 at 11:18
• On second thought, what makes you think you will get a "constant 14V" from 4S lithium ion batteries? You certainly can not charge a 4S directly from 14V. Commented Sep 22, 2019 at 11:33
• Certain classes of battery charging and electroplating (same chemistry in a way) use pulsed or alternating charging systems. If you have 7A at a high enough voltage to charge on your supply that has a controlled charge current and voltage then it should work fine for a long time. Having a bank of (super) caps to handle the pulsing may also be an option (they don't wear much, have higher efficiency) if you are guaranteed the pulsed supply but may cost more money and space for more reliability and longevity. Commented Sep 22, 2019 at 12:00
• Elliot: Practically speaking they will be fully charged all the time, since they will only discharge for 250ms before recharging. 4 batteries in series gives 14.4V. Commented Sep 23, 2019 at 13:07
• KalleMP: The pulsing is not by my choice, it's the problem I'm trying to solve. The pulsed voltage is actually a low frequency PWM signal designed for heat control. I'm designing a box to convert from that 2Hz signal to a 2kHz PWM signal so I can control the speed of a DC motor with it. The batteries would be an alternative to a capacitor in the Henry range. Commented Sep 23, 2019 at 13:10