Using cordless tool batteries to power a drone

John Doe wrote
>A measly six minutes in the air.
>The batteries were still cool.
>With no load they measured 3.86 volts.
>I will note the charge.

Yes, quite similar what I had, lipos are better.

<698839253X6D445TD@nospam.org> wrote:

> John Doe wrote

>> A measly six minutes in the air.
>> The batteries were still cool.
>> With no load they measured 3.86 volts.
>> I will note the charge.
> 
> Yes, quite similar what I had, lipos are better.

All three charges were about 950 mA hours. So less than one third of
their capacity was used. I don't get it, but for now I'm stuck. 

John Doe wrote
><698839253X6D445TD@nospam.org> wrote:
>
>> John Doe wrote
>
>>> A measly six minutes in the air.
>>> The batteries were still cool.
>>> With no load they measured 3.86 volts.
>>> I will note the charge.
>> 
>> Yes, quite similar what I had, lipos are better.
>
>All three charges were about 950 mA hours. So less than one third of
>their capacity was used. I don't get it, but for now I'm stuck. 

To what voltage level did you charge?

<698839253X6D445TD@nospam.org> wrote:

> John Doe wrote
>> <698839253X6D445TD@nospam.org> wrote:
>>> John Doe wrote
>>
>>>> A measly six minutes in the air.
>>>> The batteries were still cool.
>>>> With no load they measured 3.86 volts.
>>>> I will note the charge.
>>> 
>>> Yes, quite similar what I had, lipos are better.
>>
>> All three charges were about 950 mA hours. So less than one third of
>> their capacity was used. I don't get it, but for now I'm stuck. 
> 
> To what voltage level did you charge?

To the level it was before use, the usual level it is charged to, about 
4.2 V (no load).

Why don't we use a simple single pole single throw (SPST) switch instead 
of plugging/unplugging the battery? What switch ratings will do for 
that?

Thanks.

John Doe
>>> <698839253X6D445TD@nospam.org> wrote:
>> To what voltage level did you charge?
>
>To the level it was before use, the usual level it is charged to, about 
>4.2 V (no load).

Yes, I use 4.2 V too, use the lab supply with current limit.

>Why don't we use a simple single pole single throw (SPST) switch instead 
>of plugging/unplugging the battery? What switch ratings will do for 
>that?

My drone takes a little over 10 A full throttle at 7.4 V (2 cells).
Switches for that much current are heavy.

Switches for that much current are heavy.
And you want to be able to quickly change batteries,
I have several lipos so I can fly longer,
so you need the connectors anyways,
and there is for the lipos the charge balancing connector.
for charging, use a special charger for that.
The liion I charge one at the time.

On Wed, 05 Dec 2018 16:24:11 GMT, <698839253X6D445TD@nospam.org>
wrote:

>Switches for that much current are heavy.

A couple of FETs shouldn't be too heavy.  OTOH, good ones (milliohm
RDS(on)), to minimize the heatsink, may be a little heavy on the
pocketbook.

Well this seems interesting...
I bought some lipos, slightly larger than stock. The first flight was 
too short, so I applied the drone's voltage level fix so the low-
voltage indicator does not start flashing until it reaches 10 V or 
whatever lower realistic voltage. The next flight or two was a good 15 
minutes. Then I applied the drone's flip of death fix which makes the 
propellers spin up immediately when the drone is armed (ready for 
takeoff). Strangely, apparently that fix undoes the low-voltage level 
fix. I noticed after a short flight time when the lights started 
flashing. So I kept flying until it started losing power, figuring it 
would be at least 15 minutes. But it was only about 11 minutes until 
it started losing power. So I'm wondering if the low-voltage cut off 
does more than just flash lights, but also somehow cripples itself. 
Maybe there's some odd electronics scheme going on to do with how it 
operates at less than high-voltage. Forcing a landing in order to 
protect the batteries from discharging too much?

So I measured the battery voltage after that 11 or 12 minute flight, 
at 3.73 V per cell (no load). Seems it should be lower than that. 
That's not much less than the lithium ions when the thing could no 
longer fly. So I might try plugging the lithium-ion's back in and 
using the low-voltage fix. Even if it's double the flight time (12 
minutes) that's not enough, but it would suggest the thing is 
crippling itself. That would explain, oddly, why there was so much 
charge left in the lithium-ions.







I wrote:

> A measly six minutes in the air.
> The batteries were still cool.
> With no load they measured 3.86 volts.
> I will note the charge.

On a sunny day (Fri, 14 Dec 2018 22:20:06 -0000 (UTC)) it happened John Doe
<always.look@message.header> wrote in <pv1aam$8ge$1@dont-email.me>:

>Well this seems interesting...
>I bought some lipos, slightly larger than stock. The first flight was 
>too short, so I applied the drone's voltage level fix so the low-
>voltage indicator does not start flashing until it reaches 10 V or 
>whatever lower realistic voltage. The next flight or two was a good 15 
>minutes. Then I applied the drone's flip of death fix which makes the 
>propellers spin up immediately when the drone is armed (ready for 
>takeoff). Strangely, apparently that fix undoes the low-voltage level 
>fix. I noticed after a short flight time when the lights started 
>flashing. So I kept flying until it started losing power, figuring it 
>would be at least 15 minutes. But it was only about 11 minutes until 
>it started losing power. So I'm wondering if the low-voltage cut off 
>does more than just flash lights, but also somehow cripples itself. 
>Maybe there's some odd electronics scheme going on to do with how it 
>operates at less than high-voltage. Forcing a landing in order to 
>protect the batteries from discharging too much?
>
>So I measured the battery voltage after that 11 or 12 minute flight, 
>at 3.73 V per cell (no load). Seems it should be lower than that. 
>That's not much less than the lithium ions when the thing could no 
>longer fly. So I might try plugging the lithium-ion's back in and 
>using the low-voltage fix. Even if it's double the flight time (12 
>minutes) that's not enough, but it would suggest the thing is 
>crippling itself. That would explain, oddly, why there was so much 
>charge left in the lithium-ions.

Important is the voltage under load where the system cuts off.
This is very different from the no load voltage you measure after flight.
In my case with the H501S I can read battery voltage from the remote,
it is displayed there, else you need ground testing with a voltmeter:
 http://panteltje.com/pub/hubsan_h501s_current_test_full_throttle_IMG_6290.JPG
 that is with amp meter, but adding - or only using a voltmeter should be easy. 
Did you try flying with 2 lipos in parallel?
Oh, and do not connect a full and an empty lipo together in parallel,
things may go up in flames as a huge current can flow, charge both to full first.

I have never done any mods to the battery sensors, not even sure such a mod exists for the Hubsan.

<698839253X6D445TD@nospam.org> wrote: 

> John Doe <always.look@message.header> wrote in
> <pv1aam$8ge$1@dont-email.me>: 
> 
>>Well this seems interesting... I bought some lipos, slightly
>>larger than stock. The first flight was too short, so I applied
>>the drone's voltage level fix so the low- voltage indicator does
>>not start flashing until it reaches 10 V or whatever lower
>>realistic voltage. The next flight or two was a good 15 minutes.
>>Then I applied the drone's flip of death fix which makes the 
>>propellers spin up immediately when the drone is armed (ready for 
>>takeoff). Strangely, apparently that fix undoes the low-voltage
>>level fix. I noticed after a short flight time when the lights
>>started flashing. So I kept flying until it started losing power,
>>figuring it would be at least 15 minutes. But it was only about 11
>>minutes until it started losing power. So I'm wondering if the
>>low-voltage cut off does more than just flash lights, but also
>>somehow cripples itself. Maybe there's some odd electronics scheme
>>going on to do with how it operates at less than high-voltage.
>>Forcing a landing in order to protect the batteries from
>>discharging too much? 
>>
>>So I measured the battery voltage after that 11 or 12 minute
>>flight, at 3.73 V per cell (no load). Seems it should be lower
>>than that. That's not much less than the lithium ions when the
>>thing could no longer fly. So I might try plugging the
>>lithium-ion's back in and using the low-voltage fix. Even if it's
>>double the flight time (12 minutes) that's not enough, but it
>>would suggest the thing is crippling itself. That would explain,
>>oddly, why there was so much charge left in the lithium-ions. 
> 
> Important is the voltage under load where the system cuts off. 
> This is very different from the no load voltage you measure after
> flight. 

As written, it just happened with the lithium polymer battery, as
well. 

I'm sticking the lithium-ion 3x battery holder back onto the thing.
Then I will flash it for the low battery indicator fix. Then I will
run outside and do a flight and see what happens. 

I should have done the low battery fix before removing the
lithium-ion holder the first time, but oh well. 




> In my case with the H501S I can read battery voltage from the
> remote, it is displayed there 

I will be observing battery voltage when FPV is working. Both new
cameras I ordered have on-screen display of battery voltage, instead
of using my crap flight controller. 

> else you need ground testing with a voltmeter: 
>  http://panteltje.com/pub/hubsan_h501s_current_test_full_throttle_I
>  MG_6290.JPG 

Yes, a current meter would be cool. My old Digi-Key B&K Precision
multimeter goes up to 10 A. 

Seems like maybe a clamp-on amp meter would be good. 

>  that is with amp meter, but adding - or only using a voltmeter
>  should be easy. 
> Did you try flying with 2 lipos in parallel? 

You mean ions. No. I'm not that bullheaded. 

> Oh, and do not connect a full and an empty lipo together in
> parallel, things may go up in flames as a huge current can flow,
> charge both to full first. 

That's one concern about adding a capacitor to a lithium-ion
battery. Even if a sufficient capacitor were light and compact
enough, I guess there would be potentially damaging current every
time the battery is connected.