How long will led lights last on 18650 batteries

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

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using 2x 1m led waterproof lights

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Im running and event and want to put on poles but dont have a power source.
I understand the batteries probably arent 4000ma etc but i cant afford $6 plus a battery when i need 20 atleast, If someone could tell me a rough time they think, Also they wont be on full power too, probably half brighness and i only need them on for 2-3hrs .

Thanks

According to the advert for the LED strips they take 1 amp per meter. So in theory a 1 meter length of these LEDs would run for 4 hours on the set of 4 4Ah cells in series. I think the cells are probably closer to 2.4 Ah than the 4Ah claimed. Also I suggest measuring the current rather than just trusting the advertised data.
Another point is that you use BMS modules to manage the groups of 4 cells to balance the charging and discharging of lithium cells.

Les.

ok i might get 4 of the batteries and only run on 4 poles for now, i really dont want to pay $25 per bms in Australia when i can get from china for $3 each. Can would it be bad if i used for the first event without the bms?

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.