On Tuesday, 31 March 2020 14:10:11 UTC+1, Theo wrote:
tabbypurr wrote:
On Tuesday, 31 March 2020 12:13:58 UTC+1, Grumps wrote:

Hi All
So, as per subject. This is for some solar lights that have 250mAh NiMH
1.2V AA cells, but would 2500mAh cells work too?

sure no problem. They'd last longer too as they only see part of a cycle
each day. If the things contain more than 1 cell, do your best to
capacity match them or they'll see repeated reverse charging which kills
them much quicker.

Beware that higher capacity cells can have lower cycle life (number of
charge/discharge cycles before they die). Given solar lights only get a
certain amount of energy per day you might find the extra capacity isn't
much use, and yet they die faster due to the lower cycle life.

For comparison, Eneloop Pro have 500 cycles life, Eneloop Lite have 3000
cycles life. So the Pro would last 1.5 years and the Lite 8 years.

Theo

You ignored the fact that the bigger cells won't get fully charged.

If the 0.25Ah cells are 3k cycle & the 2.5Ah are 500 cycle:

0.25Ah: 3k cycles of full charge = 3k [summer] days of life expectancy. More days IRL because winter only part charges them.

2.5Ah: 500 cycles of 1/10th charge gives 5k days of life expectancy.

These assume no reverse charging due to unequal capacity + total discharge. Hopefully the controller stops discharging before they're fully flat.


NT