# How long will led lights last on 18650 batteries

#### isoking

##### New Member
Hi, i want to know roughly what you think 4 of these batteries in series will last for

using 2x 1m led waterproof lights

Im running and event and want to put on poles but dont have a power source.

#### Les Jones

##### Well-Known Member
If you charge the cells one at a time and monitor the charging current and voltage CONTINIUSLY to make sure the values are within the safe values for Li ion cells. And while discharging them have a voltmeter connected to each cell so that you make sure no cell drops below the low limit for the cell voltage it should be OK. Why not do the testing using a bench power supply or a battery that is more tolerant to abuse. (Such as primary cells ,lead acid. or Ni-Mh.)

Les.