'Safe' parallel charging boards

I have never charged packs in parallel.
Most battery chargers recommend you connect the balance lead first followed by the power leads. If i were to parallel charge, common sense would be to first connect the power sockets only and allow the overall cell voltages to stabilise before connecting the balance leads which would reduce the initial high current surges but certainly not eliminate them. I don't know what the polyfuse reaction time is but as they are a PTC device they obviously need current to heat before their resistance increases. - Hence your vaporising circuit tracks !

kevinross wrote: I have never charged packs in parallel.

Nor me! I have a 4 channel charger, that is 4 of same or different batteries and technology charging all at same time.

Nor me either , I have 2 chargers & always balance charge after each usage.
However what is "interesting" is the different cell voltages given on the charger compared to
readings on so called battery checkers. Different brands also giving different readings.
It would be interesting to know if anyone has carried out any comparisons using laboratory
grade equipment.

Colin.

I always balance charge, at the end of the day I charge the batteries back up to storage voltage independently, when I come to charge my batteries for a days flying they are all essentially at the same voltage, and so I parallel charge them. I connect the power leads first.

Colin, you'd have thought that voltage readings would be very similar from measuring device to measuring device, but like you I see variations. I guess it comes down to what you're prepared to pay for. If you look at electrical components they will state their accuracy, so a carbon composition resistor might have an accuracy of +/-5%, metal film resistors might be +/-0.1% one will be more expensive than the other. I only use the battery checker to check which is the full battery.

My "battery checker" is only good for a guide. I estimate that the checker is around 10 -15% out. I do find that the milliamps put back in don't compare favourably with the "checker" either. Of course it does depend on the quality/accuracy of components inside the checker and circuitry. I rely on my i306b charger for real cell voltages. And yes, I have verified using a calibrated voltmeter.