First some context: I'm building a MySensors node to replace a thermostat.
The board is powered using a 3xAA battery pack, logic use an Arduino Mini 3.3V powered through a 3.3V Step-Up converter. The relay part use a dual coil latching relay powered using a 5V Step-Up booster. Additionaly the booster is enabled on-demand using an high side switch.
At first everything worked fine, then after 2 weeks the relay stopped switching the heater. I replaced the battery using NiMH ones but still no luck. With regulated 5V or brand new alkaline everything works as expected.
After some tests here is what I gathered:
- regulated 5V in input: OK
- brand new alkaline batteries (~4.7V): OK
- NiMH batteries (~3.6V): NOK
- relay starts to fail when VCC < ~4.2V
- whatever the input voltage, the 5V booster act as it should (outputs 4.98V)
- when leaving the high side switch activated (instead of on-demand) tests results are the same.
I'm running out of ideas to debug this problem, everything seems to be within specs, any ideas to investigate this further ?