When would a lower rated Maximum Discharge battery be recommended?

[Dave Huck]

Hi,

Apologies in advance if these are dumb questions.... I have a Mateminco FW1vn on the way from Vinh. I saw that the Skylumens recommendation is for a 26650 with a 20A maximum discharge cell. What would be the reason for recommending a cell with a lower max discharge rate?

I believe these lights can use 21700 or 26650? My trusted sources for batteries in UK seem to be restricted to 21700 cells rated for 30A (40T and VTC6A).

My question is; if I can't find a battery with a max discharge of 20A, what is the risk associated with using a 30A rated cell (in either size)?

For those wondering why I didn't buy cells from Vinh; as I'm in UK it was easier to buy batteries locally, rather than deal with hysterical couriers when they see a lithium label....

Thanks in advance.

 

[vicv]

The only issue I could see is if the light is being run in direct drive and you're using the reset stance of the battery as a current limiter. A higher discharge cell would allow more current to flow and the led could possibly burn out. I doubt it but that's the only downside I could see. I presume in this case that Vinh doesn't want you to use a too low discharge cell and damage the cell because his light draws so much current. But your best bet would be to ask him

 

[DoctorMemory]

The volume of a cell is fixed. You can load it with electrodes and electrolyte and you can load it with heavy low-resistance conductors to collect the energy. But not all you want of both.

In general, when they spec maximum current for non-protected cells they really spec the cell's internal resistance. The bigger the internal conductors the lower the cells internal impedance, the higher the current spec.

But also less room for electrodes and electrolyte, less energy storage. It's a compromise and why you often see high-discharge-rate cells with lower capacities. A low amps 21700 might be 5000 mAh, a high amps might be 4000 mAh.

So, to answer your question, if a cell is rated for a higher maximum current it likely has lower capacity. If the numbers say it doesn't, they may not be accurate. Buying a cell with more amps capacity than needed (lower internal impedance) will likely result in a loss of capacity.

And, as vicv says, if the light is counting on the cell to have an impedance of a minimum value (like any 2032/LED light) then it might get bright and hot.

 

[bykfixer]

Not familiar with vaping rules in the UK anymore, but a vape shop should sell the batteries you need.

I use low discharge (read 1 amp) in lights with over driven light bulbs. In this case they are solar lamp batteries. But in your case vape batteries should do the trick.

 

[Dave Huck]

Thanks for the answers folks. Vinh actually came back to me directly and said there was a risk that a higher draw battery might damage the LEP module.