Mount/battery mystery.

[Peter B]

I wasn't sure which forum to put this in - I hope this is OK.

 

I wondered if one of the lithium polymer batteries I use for flying radio controlled model aircraft would drive my AZGTi GOTO mount. There’s no reason why it shouldn’t because fully charged the 3 cell battery provides 11.1 volts with a capacity of 5 Amp hours and these batteries are the ones used in expensive power banks. So this was effectively a power bank without the fancy case and other bells and whistles.

 

I made up a lead to connect the battery to the mount, as shown, plugged it into the mount and switched the mount on. The hand controller lit up and worked as normal, I went through the initializing procedure as normal and all seemed well. Before I tried slewing the mount I thought I would check the battery voltage so went to UTILITY > SHOW INFORMATION > BATTERY POWER and to my surprise it showed only 7.4 volts. I switched of, disconnected the battery and checked the battery voltage with a multimeter. It read 11.37 volts. I reconnected the battery to the mount and checked again and it read 7.4 volts again. This voltage was enough to slew the mount in azimuth or elevation, but not both at the same time.

 

These RC model lithium polymer batteries have a nominal 3.7 volts per cell hence this 3 cell battery provides a nominal 11.1 volts. So 7.4 volts is a 2 cell output implying that one of the cells in the battery dies when current is demanded, but it worked fine with my 12 volt radio controlled models so all 3 cells in the battery were providing output as normal.

 

I’m a retired electronics engineer but I can think of no reason why this battery apparently gives a low voltage to my AZGTi mount and would be most grateful for any suggestions or ideas why this is the case.

[TerryMcK]

You could try connecting the output to boost buck voltage regulator like this https://www.amazon.co.uk/gp/product/B08FC4DWBC and use its output connected to the mount.

I have one fitted to my HEQ5Pro and it works well.

[Peter B]

Thanks for the tip, I'll definitely look at that.

[Carbon Brush]

The obvious check is to measure the voltage from the battery pack while it is connected to the mount.
If your meter has insulation piercing probes, that is easiest way.

 

I assume in powering the model aircraft, you mean the radio kit and (probably small) servo motor.
The drive requirement of a handset display and mount motor when slewing is somewhat higher.

 

I don't know what mount you are using, but check the spec and check performance on a bench PSU.
Some mounts aren't too happy when powered from <12V.