DIYbanter - View Single Post - Replacing 250mAh NiMH with higher capacity

Theo[_3_]

wrote:
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.

That's true, but it really depends on that cutoff. NiMH cells really don't like
being run flat. If the charging is 40% to 70% then you can get many
cycles on them, but if the charging is 0% to 30% then it isn't very good to
them.

Also garden lights have a habit of being alternately frozen and cooked,
which isn't ideal for the cycle life.

Theo