I wrote:

> I would bet the 18650s in Dewalt's 9 amp hour FLEXVOLT

Actually they are 20700 or 21700 style batteries, all sorts readily
available on FleaBay from a few reputable sellers. Used in the
FLEXVOLT maybe because the larger batteries have higher discharge
current. 

Using a Bugs 3, a cheap 2 cell non-racing drone that can easily
carry an FPS camera and transmitter. Hovering indoors. Battery
rundown... 

Samsung INR21700-50E (5 AH, 10 A max current) 17 minutes
Sanyo NCR20700A (3.1 AH, 30 A max current) 19 minutes
Sanyo NCR20700B (4.2 AH, 15 A max current) 18 minutes
Sanyo NCR20700C (3.6 AH, 35 A max current) 23 minutes
New batteries were used after one charge-discharge-charge cycle. 
Measured capacity was higher. Current sourcing is approximate. 

Apparently current sourcing made all the difference. Seems the
batteries had maybe 25%-35% left over charge (I'll note that
later). Imagine using the whole battery. If weight (and maybe
electrical efficiency) weren't critical, increasing the voltage
output would be a no-brainer.

I do not quite understand the current sourcing versus longevity
thing. For total flight time, I guess it matters near the end of the
discharge. That would mean a different left over charge, obviously
since the highest capacity battery failed sooner. 

I wrote:

> I'm using a Bugs 3, a cheap drone that can carry a little weight.
> 
> Using Sanyo NCR20700A I got at least 19 minutes.

Tried some HUGE capacity (5 amp hour) authentic Samsung INR21700-50E. 
After their initial charge, a disappointing 17 minutes run time. Maybe 
they are crap, or maybe it's the low 10 amp hour discharge rate. The 
other Sanyo batteries (NCR20700B and NCR20700C) are on the way. Hoping 
for an improvement with at least the C model.

I wrote: 

> I'm using a Bugs 3, a cheap drone that can carry a little weight. 
> 
> Using Sanyo NCR20700A I got at least 19 minutes [in near ideal 
> conditions]. Still had the same problem of discharging to only 3.6
> volts. 

> Two parallel batteries [four batteries total] 

It was fun. The flight time wasn't impressive (13 minutes for 2.1 
amp hour batteries). I could hear the thing straining under the 
weight of the extra batteries. Might be worth trying small 
batteries. 

Cordless tool makers sell a 12 amp hour battery pack, apparently 4 
amp hour per cell. That probably would rock (especially if it's 
higher current), but it's expensive, seems they have trouble 
sourcing those batteries. 

If the left over charge of the NCR20700A is too much, I might try
putting a light as possible, high enough current, and very efficient
"DC booster" on it (good luck). 

Apparently Sanyo makes an even higher current-sourcing lithium ion 
battery, sold somewhere. Need to find out what exact batteries they 
use in DeWalt FlexVolt battery packs. Maybe I will buy a 6 amp hour 
version. Shurly wouldn't be less than the regular 20 V max 6 amp 
hour batteries NCR20700A. 

DecadentLinuxUserNumeroUno@decadence.org wrote:

>   I would make a front end circuit that can still make output even 
> as the input sags down.
> 
>   It seems you drive circuit senses too low a voltage and stops 
> asking, and then the batteries never go below a certain point in 
> their discharge curve.  A switcher between the battery and the 
> circuit input can fully deplete the batteries while providing the 
> voltage the circuit demands for a longer period.

Naturally I forgot about the required input voltage...

I might try increasing the voltage, but critically important is 
efficiency and weight.

John Doe <always.look@message.header> wrote in
news:q6ib0b$81p$1@dont-email.me: 

> I'm using a Bugs 3, a cheap drone that can carry a little weight.
> 
> Using Sanyo NCR20700A I got at least 19 minutes. Still had the
> same problem of discharging to only 3.6 V.
> 
> Assuming that problem arises because the current sourcing isn't
> enough when the voltage drops to 3.6 V, I'm wondering if
> paralleling smaller batteries will help.
> 
> It cut off at 3.6 V. I think it should be down to at least 3 V. I
> felt the batteries immediately after use, they were barely warm.
> 
> Question: I guess the answer is obvious, and I will test, but...
> Two parallel batteries will source greater current at a low
> voltage than a single battery?
> 
> Will see. Hopefully it will be more than the additional current
> draw required for lifting the additional batteries. I have 10 pair
> of 18650 batteries that are factory paralleled. A pair fits into
> my charger as if they are one battery. It will fit into a battery
> holder the same way, four batteries in a 2X battery holder (with
> additional support). Testing pair capacity now, should be over 4
> amp hours. 
> 
> 

  I would make a front end circuit that can still make output even 
as the input sags down.

  It seems you drive circuit senses too low a voltage and stops 
asking, and then the batteries never go below a certain point in 
their discharge curve.  A switcher between the battery and the 
circuit input can fully deplete the batteries while providing the 
voltage the circuit demands for a longer period.

I'm using a Bugs 3, a cheap drone that can carry a little weight.

Using Sanyo NCR20700A I got at least 19 minutes. Still had the same 
problem of discharging to only 3.6 V.

Assuming that problem arises because the current sourcing isn't enough 
when the voltage drops to 3.6 V, I'm wondering if paralleling smaller 
batteries will help.

It cut off at 3.6 V. I think it should be down to at least 3 V. I felt 
the batteries immediately after use, they were barely warm.

Question: I guess the answer is obvious, and I will test, but... Two 
parallel batteries will source greater current at a low voltage than a 
single battery?

Will see. Hopefully it will be more than the additional current draw 
required for lifting the additional batteries. I have 10 pair of 18650 
batteries that are factory paralleled. A pair fits into my charger as 
if they are one battery. It will fit into a battery holder the same 
way, four batteries in a 2X battery holder (with additional support). 
Testing pair capacity now, should be over 4 amp hours.

















-- 

I'm putting it in this old thread because it's appropriately titled. 
If the consensus were I should start a new thread, that would be fine.

<698839253X6D445TD@nospam.org> wrote: 

> BTW I use a MASTECH MS2108 Digital True RMS Clamp Multimeter AC DC 
> Voltage Frequency Tester 

Is that or the Mastech MS2109A clamp meter sensitive enough to
meaningfully measure changes in total current like when you add or
remove a video transmitter? 

Thanks.

Joseph Gwinn <joegwinn@comcast.net> wrote: 

> Jeff Liebermann wrote 
>> "Carl" <carl.ijamesXYZ@ZYXverizon.net>  wrote: 

>> > Weirdly, I clicked on your contact link and got a 404 page in
>> > Chinese. Then tried just "www.uni-trend.com" and got the home
>> > page in english, as always. 
>>
>> Just to clarify things, I was able to get the home page at: 
>> <http://www.uni-trend.com>  on all my machines and with all
>> browsers. The home page worked. What doesn't work for me are any
>> of the links and buttons on the home page. 
> 
> For me (Boston area)

I doubt the area makes any difference.

> <http://www.uni-trend.com>  works 
> but<https://www.uni-trend.com>  does not. The difference is http
> versus httpS. If the Chinese want to listen in, it makes sense to
> forbid https. 

Yes that works. And your explanation makes sense.

You do want buffers when dealing with Chinese stuff. A small percentage 
difference is worth it. And branding is critical, no matter how hard 
China tries to destroy it.

On Dec 16, 2018, Jeff Liebermann wrote
(in article<dknd1epbl8r0repr0basd1b1g3u1oc8757@4ax.com>):

> On Sun, 16 Dec 2018 15:53:07 -0500, "Carl"
> <carl.ijamesXYZ@ZYXverizon.net>  wrote:
>
> > Weirdly, I clicked on your contact link and got a 404 page in Chinese. Then
> > tried just "www.uni-trend.com" and got the home page in english, as always.
>
> Just to clarify things, I was able to get the home page at:
> <http://www.uni-trend.com>  on all my machines and with all browsers.
> The home page worked. What doesn't work for me are any of the links
> and buttons on the home page.

For me (Boston area), <http://www.uni-trend.com>  works 
but<https://www.uni-trend.com>  does not. The difference is http versus 
httpS. If the Chinese want to listen in, it makes sense to forbid https.

Joe Gwinn

Jeff Liebermann
>I also tried 
><https://www.uni-trend.com>
>but it would not connect.  I also removed all cookies associated with
>uni-trend.com, but the 404 error persisted.  I also clicked on most
>everything possible on the home page.  Everything I tried resulted in
>a 404 error.

http://www.uni-trend.com
is working OK here in Europe, automatically changes from Chinese to English somehow.
Linux Seamonkey, but the menus give a Chinese text and error 404.
It is not your browser

BTW before I bought that MS2108 I did some googling and watched some youtube videos
about both the uni-trend and the Mastech meters,
the choice was not hard to make.
It is funny if you see somebody advertising a meter by comparing it to an other one and the scale tips the other way all the time :-)
Hey, I have no shares in either ..