Lead Acid batteries (sealed or otherwise) come in varieties for standby use (e.g. UPS) and for deep cycle (e.g. electric vehicle, lighting). When discharged to 100% depth of discharge, the deep cycle variety will last 50% more cycles than the standby variety. Standby should last 200 full cycles, a deep cycle 300-350 cycles. Over discharge (i.e. taking out 120% of rated capacity) will shorten this. The deep cycle typically costs 20-50% more than the standby variety. In practice work on running the light to no more than 50% depth of discharge, to allow you margin as the battery ages (and reduces in capacity), and to extend the life out to 500 or so cycles. End of life is when the battery capacity is down to about 60% of new.TimC said:*AND*, most importantly, your battery will not last very long at all
if fully discharged. Lead Acid batteries, except for the marine deep
discharge variety thereof, take about 20 full discharges before going
kaput.
SLAs presumably can take the same number of deep discharges.
A 4AH 12V SLA (probably standby variety) weight 1.74kg and costs $35. The equivalent in NiMH (10 x 4.5AH C-size) is about $130, but about half the mass (1/3 for LiIon). My 10 cell 3.5AH drink bottle pack is about 0.8kg.
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