[450] The link on batteries

[John Foege]

Yea the discharge curve (at least on NiMh cells) looks approximately like a
long, stretched out S-curve on it's side.

I'm betting that:

1) your Idc,avg was higher than you initially estimated with intermitent
WLAN bursts, etc.

2) once the cells' voltages started dropping as they got into their more
fully discharged state the total voltage was below the regulator cutout
voltage and it kicked out.

3) no converting regulator is truly 96 percent efficient! :-) depends on
good design, loading, etc....if you measured the efficiency ...I bet it'd
be 85-90...

All that sound approximately reasonable? Just my ideas on the possible whys
and wherefors...

John
On Oct 11, 2013 3:24 AM, "David McKenzie" <k1fsy at vhfwiki.com> wrote:

> made it 5 hours 8 minutes.
>
>
> On Thu, Oct 10, 2013 at 7:33 PM, David McKenzie <k1fsy at vhfwiki.com> wrote:
>
>> i dont think the link sees much stress. the wifi is transmitting and
>> reeving and the sound card is blinking, though.
>>
>>
>> On Thu, Oct 10, 2013 at 7:25 PM, John Foege <john.foege at gmail.com> wrote:
>>
>>> Nice load averages...but is anyone actually stressing the link??
>>>
>>>
>>> On Fri, Oct 11, 2013 at 1:10 AM, David McKenzie <k1fsy at vhfwiki.com>wrote:
>>>
>>>>  23:09:52 up  3:23,  1 user,  load average: 0.40, 0.38, 0.40
>>>> Thu Oct 10 23:09:52 UTC 2013
>>>>
>>>>
>>>>
>>>> On Thu, Oct 10, 2013 at 4:38 PM, John Foege <john.foege at gmail.com>wrote:
>>>>
>>>>> I'm curious what the objective of this whole experiment is??
>>>>>
>>>>> I could understand hooking up a deep-cycle gel cell marine battery or
>>>>> something + a charging system + a 13.8V PSU = the link electronics /
>>>>> transceiver would run 24/7 and have battery backup for power outages...
>>>>>
>>>>> But, I'm just curious in general what the point of fooling around with
>>>>> a step-down converter and a long line of AAs is?? I'm not understanding
>>>>> what the idea is.
>>>>>
>>>>> And, secondly, is it really a concern whether or not the link can run
>>>>> on battery power? Or are you still thinking about Chris' suggestion of
>>>>> using a big fat solar panel + a gel cell + charging system and making a
>>>>> portable unit that can be hoisted up into a tree, etc. ?
>>>>>
>>>>>
>>>>> On Thu, Oct 10, 2013 at 10:27 PM, David McKenzie <k1fsy at vhfwiki.com>wrote:
>>>>>
>>>>>> I'm currently testing it with 8x generic AAs in series. So that's
>>>>>> probably about 2500mA @ 12v. The raspi with wifi/soundcard running the link
>>>>>> with my ssh session open is drawing around 275mA average from the batteries
>>>>>> measured on the battery side of the dc/dc converter. It's been up for about
>>>>>> 40 minutes and the batteries are reading a steady 12.01 volts. I don't know
>>>>>> how long it will take before Vin < Vout (it just passes through lower than
>>>>>> set voltage) will be enough to turn off but a back of the hand calculation
>>>>>> of 2500mAh / 275mA = about 9 hours of run time.
>>>>>>
>>>>>>
>>>>>> On Thu, Oct 10, 2013 at 12:05 AM, David McKenzie <k1fsy at vhfwiki.com>wrote:
>>>>>>
>>>>>>> no, ~5.6v (because AAs run hot) down to 5v.
>>>>>>>
>>>>>>> that's a LM2596 switching regulator board; Vin > Vout only. I have
>>>>>>> 10 of them now. Supposedly something like 95% efficient. That's an 8-cell
>>>>>>> battery pack I should load it up and give it another test.
>>>>>>>
>>>>>>>
>>>>>>> On Wed, Oct 9, 2013 at 11:50 PM, John Foege <john.foege at gmail.com>wrote:
>>>>>>>
>>>>>>>> 4 AAs in series? 5.2V to 12V DC-DC regulator?
>>>>>>>>
>>>>>>>> Can you set it for 1.3V to 13V and run the batts in parallel?
>>>>>>>>
>>>>>>>> I'm assuming this doesn't make any difference in run-time due to
>>>>>>>> either having a 1800 mAh 5.2V cell or a 1.3V 7200 mAh cell with the
>>>>>>>> converter...unless I'm having a massive brain fart...
>>>>>>>> On Oct 10, 2013 12:04 AM, "David McKenzie" <k1fsy at vhfwiki.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>>  Got the switching regulator modules from China. It ran for 3
>>>>>>>>> mind on those 4 nearly dead AAs :)
>>>>>>>>>
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