Battery switching without tears

On Thursday, 16 April 2020 02:05:45 UTC+3, Dan Marotta wrote:
This whole discussion is a living example of the old saw:Â* Better is the
enemy of good enough.Â* I flew for years with two batteries, two fuses,
and two switches.Â* When battery 1 gets low, flip on battery 2 then flip
off battery 1.Â* Never had an issue.


Less components means less problems with bad components, less solder joints that eventually break with vibration, all of this is better than good. I run same setup, on-off switch for both batteries, usually only one of them online, except when getting my engine (turbo) out in case battery runs out of juice right then. Zero problems ever. Glider came out of factory with both batteries wired parallel btw.

I'm wondering if the lack of actual problems with, for example, the two switch approach many of us use compared with all the bad things that COULD happen has to do with the circumstances in which we actually use the switches.

I've only been spurred to switch batteries a few times over the years (except to check the voltage). My radio display starts blinking when the voltage gets low. That's not so useful because the radio is mounted low and partially behind the control stick, but I did see it once. My ClearNav vario has a low-voltage warning setting that I think is set at 11.5 v. So between those two devices, I'm fairly sure I would see the need to switch away from an unexpectedly discharging battery before the voltage dropped precipitously (recognizing you don't get much warning for LiFePO4 types). And my backup battery, a gel cell pack all the way back in the tail, usually reads 12 point something anyway. So maybe there would be a 1 volt delta between the two batteries in a most likely failure mode--which hardly ever occurs? Would that be likely to cause a big surge of current from one battery into another?

I don't have a master switch--I use the two battery switches in lieu of that. But normally switching on a battery is the first thing I do and switching it off is the last thing; i.e., there's almost never much of a load across the switch contacts when they separate or meet.

I'm not saying bad things couldn't happen. But the fact that few if any have reported such things might be because they seldom occur in our standard operating mode.

Waiting anxiously for the experts to weigh in. This is more entertaining than arguing about the Coronavirus.

Chip Bearden
JB

Observation of real life events makes this seem to be as frightening as
a comet hitting the earth.Â* I have a degree in electrical engineering
and I don't see the problem.Â* What I do see is people quoting theory.Â*
They are, of course, absolutely correct and their elegant and sometimes
complicated solutions will also work.Â* But it is my firm belief from
practical experience and observation that this is really just ****ing in
a rain storm.

You're right, Chip.Â* Nothing bad is going to happen with your setup.Â*
And yes, this is a lot more entertaining than that virus thing.

On 4/16/2020 11:03 AM, wrote:
I'm wondering if the lack of actual problems with, for example, the two switch approach many of us use compared with all the bad things that COULD happen has to do with the circumstances in which we actually use the switches.

I've only been spurred to switch batteries a few times over the years (except to check the voltage). My radio display starts blinking when the voltage gets low. That's not so useful because the radio is mounted low and partially behind the control stick, but I did see it once. My ClearNav vario has a low-voltage warning setting that I think is set at 11.5 v. So between those two devices, I'm fairly sure I would see the need to switch away from an unexpectedly discharging battery before the voltage dropped precipitously (recognizing you don't get much warning for LiFePO4 types). And my backup battery, a gel cell pack all the way back in the tail, usually reads 12 point something anyway. So maybe there would be a 1 volt delta between the two batteries in a most likely failure mode--which hardly ever occurs? Would that be likely to cause a big surge of current from one battery into another?

I don't have a master switch--I use the two battery switches in lieu of that. But normally switching on a battery is the first thing I do and switching it off is the last thing; i.e., there's almost never much of a load across the switch contacts when they separate or meet.

I'm not saying bad things couldn't happen. But the fact that few if any have reported such things might be because they seldom occur in our standard operating mode.

Waiting anxiously for the experts to weigh in. This is more entertaining than arguing about the Coronavirus.

Chip Bearden
JB

--
Dan, 5J