Is it safe to substitute rechargeable batteries for primary cells, e.g., RCR123s for CR123s? I sthere any danger of damaging the bulb/LED or circuitry?
That depends entirely on your specific light. It will destroy some lights, not function correctly in others, and work just fine in lights designed for them.
Is it safe to substitute rechargeable batteries for primary cells, e.g., RCR123s for CR123s? I sthere any danger of damaging the bulb/LED or circuitry?