Discuss Battery charge counter in the Electrical Forum area at ElectriciansForums.net


New EF Member
Hi guys,

I hope someone could help with my problem.
First of all i am zero when it comes to electric.
So my issue, i have a rental company for little underwater scooters here in spain. I work with beach rentals who rent out my scooters to their clients. I charge the beach rentals per 30 min run(one battery charge).

For me not to be constant at the beach and count the amount of times the beach rental uses my scooter i want to put some sort of counter into the charging mould for the battery. But the inverter from 240v to 12.6v sends constant juice to the battery charging mould...therefor to build in a simple impulse counter wont work.

Would you guys have another option for me to count each full charge cycle on this charger?

Thank you so much !

Lucien Nunes

Respected Member
London / Tallinn
To count the number of charge / discharge cycles you need a circuit that can recognise either a significant charge or significant discharge occurring. You wouldn't want to register a rental just because they powered the machine on for two seconds to test it, or when the power to the charger was momentarily cut and the charge occurred in two sessions.

To detect this using the battery voltage, you would need to find one threshold voltage below which it will not fall unless in full use, and another higher threshold above which a used battery will rise when well charged. A rental cycle would be registered when the voltage falls below the lower threshold, then rises above the upper threshold.

Better would be to measure the current (and its direction), and average over say one minute. Any continuous discharge of a reasonable fraction of the motor running current for a minute, would probably indicate it's in use. Then when the current reverses, it's on charge, which would complete the rental cycle and trigger the counter.

This is not difficult but needs custom electronics. There might be other easier ways to identify a usage cycle than monitoring the battery specifically.

static zap

Regular EF Member
west midlands
It is possible ,your batteries will be less well maintained.
(if there is a financial penalty for keeping them topped up)
As topped up is good for customer experience / safety !


Control System Engineer
Respected Member
Small micro PLC connected to a relay and a push button.

Press the button to start charging, the relay energies the charging circuit for x amount of time say 35min.

Each time the button is pressed, add 1 to a counter in the PLC.

Button is locked out of function until the charging time has expired.

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