A complicated question about LiFePO4 batteries, - and switching.

On Tuesday, June 19, 2018 at 9:30:32 AM UTC-7, Andy Blackburn wrote:
John,

Have you tried any of these?

https://www.ebay.com/itm/15A-Solar-P...sAAOSw-0RbApaz

They claim almost zero voltage drop compared to Schottkey diodes. Of course with the rapid voltage fallow of LiFePO4 batteries, it may only make a tiny difference in effective capacity.

Andy Blackburn
9B


On Tuesday, June 19, 2018 at 6:23:07 AM UTC-7, OHM Ω http://aviation.derosaweb.net wrote:

- But I do have Schottkey diodes in each bus. Why, you might ask, do I have diodes if I have two separate electrical buses? Because I can bridge the two buses with another switch for that "just in case situation" (belts and braces engineering over design). I have never have to use this switch but then again you never know ...

Thanks, John OHM Ω

Being pedantic for a moment, the diode drop is proportional to the endurance reduction, and has little to do with the battery voltage characteristic. If you drop 0.7V on a 13V battery, you're going to be drawing 5% more power and have 5% less endurance. 0.3 across a Schottky is starting to look pretty small and across those virtual diodes not much at all.

The explanation is that almost all modern electronics are using switching power supplies to produce the required amount of power at 5 or 3.3V. Less input voltage to the power supply just means it draws more current to get the same output. On that basis alone a 13.5V LFP will last 10% longer than a 12.5V SLA, at the same AH.

If it weren't windy, I'd be flying instead of pedantic .