Author Topic: A solar supercap powered Moteino (15Farad charged by BQ25504)  (Read 38947 times)

perky

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Re: A solar supercap powered Moteino
« Reply #15 on: February 09, 2017, 10:49:46 AM »
The rated ESR of the supercap is 1.8 ohms.  The nominal Tx current drawn is between 30-40ma.  So, that alone doesn't account for it.  I got an impression that the voltage drop seems to get progressively bigger as the voltage declines.  Perhaps that's a clue.
I'm not aware of an ESR dependence on voltage, however if the power remains constant for transmission I suppose the current could increase a bit. This effect you're seeing is very large though.

Just a thought, but have you tried setting the current limiter for the transmitter? Is seems there's something else going on to cause such a large drop.

Mark.

WhiteHare

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Re: A solar supercap powered Moteino
« Reply #16 on: February 09, 2017, 02:51:37 PM »
Just a thought, but have you tried setting the current limiter for the transmitter? Is seems there's something else going on to cause such a large drop.

Thanks for the suggestion.  I'll look into that.

« Last Edit: February 09, 2017, 02:56:21 PM by WhiteHare »

WhiteHare

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Re: A solar supercap powered Moteino
« Reply #17 on: February 10, 2017, 12:31:18 PM »
More good news: we're finally having an overcast, cloudy day here.  Even with that impediment, the charger is charging just fine based on the ambient light that comes in from outdoors.  This is something I just wasn't able to do with other chargers I've tried.

I realize I need to quantify this better, but it's certainly encouraging.   :)

WhiteHare

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #18 on: February 15, 2017, 01:48:50 PM »
I created an alternative to radio.send where:
1. First, it samples the supercap voltage using TomWS's double match algorithm.
2. It then initiates transmission of that voltage measurement using the RFM69HW.
3. Then, immediately after initiating the transmission, it does single shot voltage measurement in a loop--storing each measurement in a list--until the transmission completes.
4. Finally, it does another voltage measurement on the supercap using the TomWS double match algorithm.

Once the above data is collected, it sends the above measured voltages using the regular RFM69 library radio.send method.  However, I spaced the transmissions at 1 second intervals or else it runs out of juice before it can transmit all the data.  Why?  Well, the measured voltages tell the tale:


10,[Sender:2],352,[RX_RSSI:-34]  //double match measurement
11,[Sender:2],352,[RX_RSSI:-34]  //single shot measurement
12,[Sender:2],336,[RX_RSSI:-34]  //single shot measurement
13,[Sender:2],335,[RX_RSSI:-34]  //single shot measurement
14,[Sender:2],335,[RX_RSSI:-33]  //single shot measurement
15,[Sender:2],327,[RX_RSSI:-33]  //single shot measurement
16,[Sender:2],327,[RX_RSSI:-34]  //single shot measurement
17,[Sender:2],327,[RX_RSSI:-34]  //single shot measurement
18,[Sender:2],327,[RX_RSSI:-33]  //single shot measurement
19,[Sender:2],327,[RX_RSSI:-34]  //single shot measurement
20,[Sender:2],327,[RX_RSSI:-34]  //single shot measurement
21,[Sender:2],327,[RX_RSSI:-34]  //single shot measurement
22,[Sender:2],327,[RX_RSSI:-33]  //single shot measurement
23,[Sender:2],323,[RX_RSSI:-34]  //single shot measurement
24,[Sender:2],323,[RX_RSSI:-33]  //double match measurement

So, to summarize, a total of 13 single-shot voltage measurements were taken during Tx mode, which lasted about 950uSec.  Over the course of that 950uSec, the supercap voltage droped from 3.52v down to 3.23v.  That's nearly a 0.3v drop over the course of 950uSec.

If given a chance to rest before repeating the cycle, it will experience voltage recovery.  I haven't yet developed the data on how long it needs to rest before resting longer has reached diminishing returns.

Felix

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #19 on: February 15, 2017, 02:00:23 PM »
3. Then, immediately after initiating the transmission, it does single shot voltage measurement in a loop--storing each measurement in a list--until the transmission completes.
How exactly do you do this part?
The RFM69 lib waits for the transmission to finish (ie the sends are blocking).

WhiteHare

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #20 on: February 15, 2017, 02:17:35 PM »
Yeah, that's why I had to create an alternative to the regular radio.send.  I could post the code if you like.  However, as I wrote the code in a hurry, it's brute force and not very elegant.

Felix

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #21 on: February 15, 2017, 02:23:23 PM »
Yeah, that's why I had to create an alternative to the regular radio.send.  I could post the code if you like.  However, as I wrote the code in a hurry, it's brute force and not very elegant.
OK I see. I think it would have some value to see your method, a non-blocking send could be useful to add to the main lib, just an idea. I am interested in trying it also while I'm doing some coin cell ADC readings myself.

perky

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #22 on: February 15, 2017, 02:51:31 PM »
Using dV = Idt/C and with C = 15F, dt= 1ms and I=50mA you get dV = 3.3uV. That's many orders of magnitude below what you're seeing.

Do you have a datasheet for the cap? OK, I saw the other post.

I'm not convinced by this. The ESR of the spec sheet says around 7.5 ohms, which at 50mA gives about 375mV drop. I suspect the fall from 3.52V to 3.23V during actual transmission is a result of the ESR causing a source voltage drop, and the time it takes for the ADC input capacitor to discharge through the pull-up/pull-down resistors, and if you left it transmitting for longer it would settle out (in fact I think you can see it levelling out in your data, the drops are getting smaller as time goes on). That also explains the recovery at the end when the ADC cap charges back up.

Mark.
« Last Edit: February 15, 2017, 03:43:17 PM by perky »

WhiteHare

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #23 on: February 15, 2017, 05:32:01 PM »
OK I see. I think it would have some value to see your method, a non-blocking send could be useful to add to the main lib, just an idea. I am interested in trying it also while I'm doing some coin cell ADC readings myself.


You can easily get a non-blocking sendFrame by taking your regular sendFrame code and deleting:
Code: [Select]
  uint32_t txStart = millis();
  while (digitalRead(_interruptPin) == 0 && millis() - txStart < RF69_TX_LIMIT_MS); // wait for DIO0 to turn HIGH signalling transmission finish
  //while (readReg(REG_IRQFLAGS2) & RF_IRQFLAGS2_PACKETSENT == 0x00); // wait for ModeReady
  setMode(RF69_MODE_STANDBY);

Let's call that nonBlockingSendFrame(...).

Assuming the sequencer is active (which it is by default), the RFM69 will automatically go into standby mode after the Tx completes.  For that reason, I don't believe you need 
Code: [Select]
millis() - txStart < RF69_TX_LIMIT_MS

nor do you need
Code: [Select]
setMode(RF69_MODE_STANDBY);
afterward.

So, in essence, what I do is call nonBlockingSendFrame(...), which initates the transmission, and then do a  loop which repeatedly reads raw voltages and stores them in a list until there's proof the packet was sent.

Afterward, I convert the raw voltages into real voltages and then send each one in the list, one by one, using the RFM69's regular radio.send method.

WhiteHare

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #24 on: February 15, 2017, 05:41:46 PM »
Using dV = Idt/C and with C = 15F, dt= 1ms and I=50mA you get dV = 3.3uV. That's many orders of magnitude below what you're seeing.

Do you have a datasheet for the cap? OK, I saw the other post.

I'm not convinced by this. The ESR of the spec sheet says around 7.5 ohms, which at 50mA gives about 375mV drop. I suspect the fall from 3.52V to 3.23V during actual transmission is a result of the ESR causing a source voltage drop, and the time it takes for the ADC input capacitor to discharge through the pull-up/pull-down resistors, and if you left it transmitting for longer it would settle out (in fact I think you can see it levelling out in your data, the drops are getting smaller as time goes on). That also explains the recovery at the end when the ADC cap charges back up.

Mark.

That's an interesting analysis.  I like it.  So, if I understand correctly, you are predicting that if I were to send a packet with a much larger payload (which would be easy to arrange), then the list of voltages would pretty soon approach the 375mv drop caused by the ESR, and not continue to drop.  Is that right?

perky

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #25 on: February 15, 2017, 06:09:36 PM »
That's an interesting analysis.  I like it.  So, if I understand correctly, you are predicting that if I were to send a packet with a much larger payload (which would be easy to arrange), then the list of voltages would pretty soon approach the 375mv drop caused by the ESR, and not continue to drop.  Is that right?

Yes in a nutshell.

Mark.

ChemE

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Re: A solar supercap powered Moteino
« Reply #26 on: February 16, 2017, 07:53:48 PM »
For that test, all you need is the supercap, which is: https://www.digikey.com/product-detail/en/vishay-bc-components/MAL219691203E3/4701PHBK-ND/5015885
You can simply hook it up to a power supply to charge it to 3.6v, disconnect it, and then connect it to a moteino just as you would a battery.

I tried a number of supercaps, and some superficial testing suggested this one seems to have a very low self discharge rate.

Took your suggestion.  I'm hoping that these 15F caps are a good way to compare power strategies to see which has the least area under the curve.  My initial testing shows really large variability in how many cycles I get before the voltage gets too low.  For instance, I get 87 or 52 or 66 cycles from a breadboard 328p waking up every 8s getting a temp/RH/Vcc and dumping the whole lot to the UART.  Not sure if it is because my cap is new (the same Vishay you have) or if it depends on how long it soaks at 3.6V prior to the test or if they are just that variable.

WhiteHare

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Re: A solar supercap powered Moteino
« Reply #27 on: February 17, 2017, 05:57:16 AM »
Took your suggestion.  I'm hoping that these 15F caps are a good way to compare power strategies to see which has the least area under the curve.  My initial testing shows really large variability in how many cycles I get before the voltage gets too low.  For instance, I get 87 or 52 or 66 cycles from a breadboard 328p waking up every 8s getting a temp/RH/Vcc and dumping the whole lot to the UART.  Not sure if it is because my cap is new (the same Vishay you have) or if it depends on how long it soaks at 3.6V prior to the test or if they are just that variable.

Exactly so.  I'm not even sure yet how to label what this issue is.  Whatever it is, I do get the impresson this is true for supercaps generally and not just this particular model in particular. 

Ultimately I want to somehow measure, or somehow track, how much usable current I can expect to get out of a supercap.  But how?  A single snapshot of the unloaded voltage alone doesn't appear to give good answers.  That's not surprising, as ESR is clearly a factor.  The rate of self discharge is going to be a factor, but there seems to be no industry standard for measuring that.  Are there other significant factors?  My gut tells me yes, but at present I just don't know.

 


ChemE

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #28 on: February 17, 2017, 09:46:13 AM »
Variability aside I do seem to be getting some useful results out of my ultracap.  Rather than 50-80 cycles leaving the sensor on, I only get 20ish cycles when I depower the sensor while sleeping.  Also, setting my clock divider to 2 is still running even now and currently at 129 cycles.  So maybe they aren't repeatable enough to differentiate between subtle code changes but the bigger things seem to be testable.  Still early days and there is a lot more playing to do but these seem useful as integrators.

EDIT: Clk_div_2 is at 218 cycles and really not dropping very quickly at all.  Certainly a remarkable improvement and much more than I would have expected!

EDIT2: Good God, 651 1,019 cycles and still going strong.  I have to think that something else is at play now like maybe the cap needed to be charged/conditioned and it just had not happened until this run.  Don't know, more investigation is needed.

EDIT3: I should just start my own thread b/c I don't want to spam this one.  I stopped my CLK_DIV_2 test at 1,400 packets convinced that something had changed internally in the ultracap and went back to CLK_DIV_1.  That trial died after 70 cycles!  So at least regarding this cap there is a massive difference between running at 16MHz and 8MHz.
« Last Edit: February 17, 2017, 12:55:46 PM by ChemE »

WhiteHare

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Re: A solar supercap powered Moteino (15Farad charged by BQ25504)
« Reply #29 on: February 17, 2017, 10:13:40 AM »
Yes in a nutshell.

Mark.

I just now did the experiment using a 60 byte payload on the supercap, which I had just finished charging for more than a day using the charger circuit powered by a couple of AA's (so that it could charge at night as well).  Here are the early results:
Code: [Select]
101,[Sender:2],352 ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789,[RX_RSSI:-36]
102,[Sender:2],352,[RX_RSSI:-36]
103,[Sender:2],344,[RX_RSSI:-35]
104,[Sender:2],344,[RX_RSSI:-34]
105,[Sender:2],335,[RX_RSSI:-35]
106,[Sender:2],335,[RX_RSSI:-35]
107,[Sender:2],335,[RX_RSSI:-34]
108,[Sender:2],335,[RX_RSSI:-35]
109,[Sender:2],335,[RX_RSSI:-35]
110,[Sender:2],331,[RX_RSSI:-34]
111,[Sender:2],327,[RX_RSSI:-35]
112,[Sender:2],327,[RX_RSSI:-35]
113,[Sender:2],327,[RX_RSSI:-35]
114,[Sender:2],327,[RX_RSSI:-35]
115,[Sender:2],327,[RX_RSSI:-35]
116,[Sender:2],327,[RX_RSSI:-35]
117,[Sender:2],327,[RX_RSSI:-35]
118,[Sender:2],327,[RX_RSSI:-35]
119,[Sender:2],327,[RX_RSSI:-35]
120,[Sender:2],327,[RX_RSSI:-35]
121,[Sender:2],327,[RX_RSSI:-35]
122,[Sender:2],327,[RX_RSSI:-35]
123,[Sender:2],327,[RX_RSSI:-34]
124,[Sender:2],327,[RX_RSSI:-35]
125,[Sender:2],327,[RX_RSSI:-35]
126,[Sender:2],327,[RX_RSSI:-35]
127,[Sender:2],327,[RX_RSSI:-35]
128,[Sender:2],323,[RX_RSSI:-35]
129,[Sender:2],323,[RX_RSSI:-35]
130,[Sender:2],323,[RX_RSSI:-35]
131,[Sender:2],323,[RX_RSSI:-35]
132,[Sender:2],323,[RX_RSSI:-35]
133,[Sender:2],323,[RX_RSSI:-35]
134,[Sender:2],323,[RX_RSSI:-35]
135,[Sender:2],323,[RX_RSSI:-34]
136,[Sender:2],323,[RX_RSSI:-35]
137,[Sender:2],319,[RX_RSSI:-36]
138,[Sender:2],318,[RX_RSSI:-36]
139,[Sender:2],352 ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789,[RX_RSSI:-35]
140,[Sender:2],352,[RX_RSSI:-35]
141,[Sender:2],344,[RX_RSSI:-35]
142,[Sender:2],335,[RX_RSSI:-35]
143,[Sender:2],335,[RX_RSSI:-35]
144,[Sender:2],335,[RX_RSSI:-35]
145,[Sender:2],335,[RX_RSSI:-37]
146,[Sender:2],335,[RX_RSSI:-41]
147,[Sender:2],327,[RX_RSSI:-47]
148,[Sender:2],327,[RX_RSSI:-45]
149,[Sender:2],327,[RX_RSSI:-46]
150,[Sender:2],327,[RX_RSSI:-47]
151,[Sender:2],327,[RX_RSSI:-44]
152,[Sender:2],327,[RX_RSSI:-46]
153,[Sender:2],327,[RX_RSSI:-44]
154,[Sender:2],327,[RX_RSSI:-46]
155,[Sender:2],327,[RX_RSSI:-46]
156,[Sender:2],327,[RX_RSSI:-45]
157,[Sender:2],327,[RX_RSSI:-45]
158,[Sender:2],327,[RX_RSSI:-46]
159,[Sender:2],327,[RX_RSSI:-45]
160,[Sender:2],327,[RX_RSSI:-46]
161,[Sender:2],323,[RX_RSSI:-44]
162,[Sender:2],323,[RX_RSSI:-45]
163,[Sender:2],323,[RX_RSSI:-45]
164,[Sender:2],323,[RX_RSSI:-44]
165,[Sender:2],323,[RX_RSSI:-46]
166,[Sender:2],323,[RX_RSSI:-44]
167,[Sender:2],319,[RX_RSSI:-45]
168,[Sender:2],319,[RX_RSSI:-45]
169,[Sender:2],319,[RX_RSSI:-44]
170,[Sender:2],319,[RX_RSSI:-45]
171,[Sender:2],319,[RX_RSSI:-45]
172,[Sender:2],319,[RX_RSSI:-46]
173,[Sender:2],319,[RX_RSSI:-44]
174,[Sender:2],319,[RX_RSSI:-44]
175,[Sender:2],319,[RX_RSSI:-46]
176,[Sender:2],318,[RX_RSSI:-44]
177,[Sender:2],352 ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789,[RX_RSSI:-46]
178,[Sender:2],352,[RX_RSSI:-46]
179,[Sender:2],344,[RX_RSSI:-45]
180,[Sender:2],335,[RX_RSSI:-46]
181,[Sender:2],331,[RX_RSSI:-46]
182,[Sender:2],331,[RX_RSSI:-46]
183,[Sender:2],327,[RX_RSSI:-46]
184,[Sender:2],327,[RX_RSSI:-45]
185,[Sender:2],327,[RX_RSSI:-46]
186,[Sender:2],327,[RX_RSSI:-45]
187,[Sender:2],327,[RX_RSSI:-46]
188,[Sender:2],327,[RX_RSSI:-47]
189,[Sender:2],327,[RX_RSSI:-46]
190,[Sender:2],327,[RX_RSSI:-47]
191,[Sender:2],327,[RX_RSSI:-46]
192,[Sender:2],327,[RX_RSSI:-46]
193,[Sender:2],327,[RX_RSSI:-45]
194,[Sender:2],327,[RX_RSSI:-41]
195,[Sender:2],327,[RX_RSSI:-36]
196,[Sender:2],323,[RX_RSSI:-36]
197,[Sender:2],323,[RX_RSSI:-36]
198,[Sender:2],323,[RX_RSSI:-35]
199,[Sender:2],323,[RX_RSSI:-36]
200,[Sender:2],319,[RX_RSSI:-37]
201,[Sender:2],319,[RX_RSSI:-37]
202,[Sender:2],319,[RX_RSSI:-36]
203,[Sender:2],319,[RX_RSSI:-37]
204,[Sender:2],319,[RX_RSSI:-36]
205,[Sender:2],319,[RX_RSSI:-37]
206,[Sender:2],319,[RX_RSSI:-36]
207,[Sender:2],319,[RX_RSSI:-36]
208,[Sender:2],319,[RX_RSSI:-36]
209,[Sender:2],319,[RX_RSSI:-36]
210,[Sender:2],319,[RX_RSSI:-36]
211,[Sender:2],319,[RX_RSSI:-36]
212,[Sender:2],319,[RX_RSSI:-36]
213,[Sender:2],319,[RX_RSSI:-36]
214,[Sender:2],316,[RX_RSSI:-36]
215,[Sender:2],352 ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789,[RX_RSSI:-36]
216,[Sender:2],352,[RX_RSSI:-36]
217,[Sender:2],344,[RX_RSSI:-35]
218,[Sender:2],335,[RX_RSSI:-41]
219,[Sender:2],327,[RX_RSSI:-44]
220,[Sender:2],327,[RX_RSSI:-40]
221,[Sender:2],327,[RX_RSSI:-36]
222,[Sender:2],327,[RX_RSSI:-36]
223,[Sender:2],327,[RX_RSSI:-36]
224,[Sender:2],327,[RX_RSSI:-36]
225,[Sender:2],327,[RX_RSSI:-37]
226,[Sender:2],327,[RX_RSSI:-36]
227,[Sender:2],327,[RX_RSSI:-36]
228,[Sender:2],327,[RX_RSSI:-36]
229,[Sender:2],323,[RX_RSSI:-36]
230,[Sender:2],323,[RX_RSSI:-36]
231,[Sender:2],323,[RX_RSSI:-35]
232,[Sender:2],323,[RX_RSSI:-36]
233,[Sender:2],323,[RX_RSSI:-36]
234,[Sender:2],319,[RX_RSSI:-36]
235,[Sender:2],319,[RX_RSSI:-36]
236,[Sender:2],319,[RX_RSSI:-37]
237,[Sender:2],319,[RX_RSSI:-37]
238,[Sender:2],319,[RX_RSSI:-35]
239,[Sender:2],319,[RX_RSSI:-35]
240,[Sender:2],319,[RX_RSSI:-35]
241,[Sender:2],319,[RX_RSSI:-35]
242,[Sender:2],319,[RX_RSSI:-35]
243,[Sender:2],319,[RX_RSSI:-35]
244,[Sender:2],319,[RX_RSSI:-35]
245,[Sender:2],319,[RX_RSSI:-35]
246,[Sender:2],319,[RX_RSSI:-35]
247,[Sender:2],319,[RX_RSSI:-35]
248,[Sender:2],319,[RX_RSSI:-35]
249,[Sender:2],319,[RX_RSSI:-35]
250,[Sender:2],319,[RX_RSSI:-35]
251,[Sender:2],316,[RX_RSSI:-35]
252,[Sender:2],352 ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789,[RX_RSSI:-35]
253,[Sender:2],352,[RX_RSSI:-35]
254,[Sender:2],344,[RX_RSSI:-35]
255,[Sender:2],335,[RX_RSSI:-38]
256,[Sender:2],327,[RX_RSSI:-44]
257,[Sender:2],327,[RX_RSSI:-36]
258,[Sender:2],327,[RX_RSSI:-35]
259,[Sender:2],327,[RX_RSSI:-34]
260,[Sender:2],327,[RX_RSSI:-35]
261,[Sender:2],327,[RX_RSSI:-34]
262,[Sender:2],327,[RX_RSSI:-34]
263,[Sender:2],327,[RX_RSSI:-35]
264,[Sender:2],327,[RX_RSSI:-35]
265,[Sender:2],327,[RX_RSSI:-35]
266,[Sender:2],323,[RX_RSSI:-35]
267,[Sender:2],323,[RX_RSSI:-35]
268,[Sender:2],323,[RX_RSSI:-35]
269,[Sender:2],323,[RX_RSSI:-35]
270,[Sender:2],319,[RX_RSSI:-35]
271,[Sender:2],319,[RX_RSSI:-35]
272,[Sender:2],319,[RX_RSSI:-35]
273,[Sender:2],319,[RX_RSSI:-35]
274,[Sender:2],319,[RX_RSSI:-35]
275,[Sender:2],319,[RX_RSSI:-35]
276,[Sender:2],319,[RX_RSSI:-35]
277,[Sender:2],319,[RX_RSSI:-35]
278,[Sender:2],319,[RX_RSSI:-35]
279,[Sender:2],319,[RX_RSSI:-35]
280,[Sender:2],319,[RX_RSSI:-34]
281,[Sender:2],319,[RX_RSSI:-34]
282,[Sender:2],319,[RX_RSSI:-35]
283,[Sender:2],319,[RX_RSSI:-36]
284,[Sender:2],319,[RX_RSSI:-35]
285,[Sender:2],319,[RX_RSSI:-35]
286,[Sender:2],319,[RX_RSSI:-35]
287,[Sender:2],319,[RX_RSSI:-36]
288,[Sender:2],313,[RX_RSSI:-35]
289,[Sender:2],352 ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789,[RX_RSSI:-35]
290,[Sender:2],352,[RX_RSSI:-35]
291,[Sender:2],344,[RX_RSSI:-36]
292,[Sender:2],335,[RX_RSSI:-35]
293,[Sender:2],327,[RX_RSSI:-35]
294,[Sender:2],327,[RX_RSSI:-36]
295,[Sender:2],327,[RX_RSSI:-35]
296,[Sender:2],327,[RX_RSSI:-35]
297,[Sender:2],327,[RX_RSSI:-35]
298,[Sender:2],327,[RX_RSSI:-35]
299,[Sender:2],327,[RX_RSSI:-35]
300,[Sender:2],323,[RX_RSSI:-34]
301,[Sender:2],323,[RX_RSSI:-35]
302,[Sender:2],323,[RX_RSSI:-35]
303,[Sender:2],323,[RX_RSSI:-35]
304,[Sender:2],319,[RX_RSSI:-36]
305,[Sender:2],319,[RX_RSSI:-35]
306,[Sender:2],319,[RX_RSSI:-35]
307,[Sender:2],319,[RX_RSSI:-35]
308,[Sender:2],319,[RX_RSSI:-35]
309,[Sender:2],319,[RX_RSSI:-36]
310,[Sender:2],319,[RX_RSSI:-35]
311,[Sender:2],319,[RX_RSSI:-36]
312,[Sender:2],319,[RX_RSSI:-36]
313,[Sender:2],319,[RX_RSSI:-35]
314,[Sender:2],319,[RX_RSSI:-36]
315,[Sender:2],319,[RX_RSSI:-36]
316,[Sender:2],319,[RX_RSSI:-36]
317,[Sender:2],319,[RX_RSSI:-36]
318,[Sender:2],319,[RX_RSSI:-36]
319,[Sender:2],319,[RX_RSSI:-36]
320,[Sender:2],319,[RX_RSSI:-36]
321,[Sender:2],319,[RX_RSSI:-36]
322,[Sender:2],319,[RX_RSSI:-36]
323,[Sender:2],319,[RX_RSSI:-36]
324,[Sender:2],319,[RX_RSSI:-36]
325,[Sender:2],319,[RX_RSSI:-36]
326,[Sender:2],313,[RX_RSSI:-35]
327,[Sender:2],352 ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789,[RX_RSSI:-36]
328,[Sender:2],352,[RX_RSSI:-36]
329,[Sender:2],336,[RX_RSSI:-36]
330,[Sender:2],335,[RX_RSSI:-36]
331,[Sender:2],327,[RX_RSSI:-35]
332,[Sender:2],327,[RX_RSSI:-35]
333,[Sender:2],327,[RX_RSSI:-35]
334,[Sender:2],327,[RX_RSSI:-36]
335,[Sender:2],327,[RX_RSSI:-36]
336,[Sender:2],323,[RX_RSSI:-34]
337,[Sender:2],323,[RX_RSSI:-35]
338,[Sender:2],323,[RX_RSSI:-35]
339,[Sender:2],323,[RX_RSSI:-35]
340,[Sender:2],323,[RX_RSSI:-34]
341,[Sender:2],319,[RX_RSSI:-35]
342,[Sender:2],319,[RX_RSSI:-35]
343,[Sender:2],319,[RX_RSSI:-36]
344,[Sender:2],319,[RX_RSSI:-37]
345,[Sender:2],319,[RX_RSSI:-36]
346,[Sender:2],319,[RX_RSSI:-36]
347,[Sender:2],319,[RX_RSSI:-36]
348,[Sender:2],319,[RX_RSSI:-35]
349,[Sender:2],319,[RX_RSSI:-35]
350,[Sender:2],319,[RX_RSSI:-35]
351,[Sender:2],319,[RX_RSSI:-36]
352,[Sender:2],319,[RX_RSSI:-36]
353,[Sender:2],319,[RX_RSSI:-36]
354,[Sender:2],319,[RX_RSSI:-36]
355,[Sender:2],319,[RX_RSSI:-35]
356,[Sender:2],319,[RX_RSSI:-36]
357,[Sender:2],319,[RX_RSSI:-36]
358,[Sender:2],319,[RX_RSSI:-35]
359,[Sender:2],319,[RX_RSSI:-35]
360,[Sender:2],319,[RX_RSSI:-36]
361,[Sender:2],319,[RX_RSSI:-35]
362,[Sender:2],319,[RX_RSSI:-35]
363,[Sender:2],319,[RX_RSSI:-35]
364,[Sender:2],313,[RX_RSSI:-35]
365,[Sender:2],352 ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789,[RX_RSSI:-35]
366,[Sender:2],352,[RX_RSSI:-35]
367,[Sender:2],335,[RX_RSSI:-35]
368,[Sender:2],335,[RX_RSSI:-35]
369,[Sender:2],327,[RX_RSSI:-35]
370,[Sender:2],327,[RX_RSSI:-35]
371,[Sender:2],327,[RX_RSSI:-36]
372,[Sender:2],327,[RX_RSSI:-37]
373,[Sender:2],323,[RX_RSSI:-36]
374,[Sender:2],323,[RX_RSSI:-37]
375,[Sender:2],323,[RX_RSSI:-36]
376,[Sender:2],323,[RX_RSSI:-34]
377,[Sender:2],319,[RX_RSSI:-37]
378,[Sender:2],319,[RX_RSSI:-35]
379,[Sender:2],319,[RX_RSSI:-35]
380,[Sender:2],319,[RX_RSSI:-34]
381,[Sender:2],319,[RX_RSSI:-36]
382,[Sender:2],319,[RX_RSSI:-36]
383,[Sender:2],319,[RX_RSSI:-37]
384,[Sender:2],319,[RX_RSSI:-36]
385,[Sender:2],319,[RX_RSSI:-36]
386,[Sender:2],319,[RX_RSSI:-36]
387,[Sender:2],319,[RX_RSSI:-36]
388,[Sender:2],319,[RX_RSSI:-35]
389,[Sender:2],319,[RX_RSSI:-36]
390,[Sender:2],319,[RX_RSSI:-35]
391,[Sender:2],319,[RX_RSSI:-34]
392,[Sender:2],319,[RX_RSSI:-36]
393,[Sender:2],319,[RX_RSSI:-36]
394,[Sender:2],319,[RX_RSSI:-35]
395,[Sender:2],319,[RX_RSSI:-36]
396,[Sender:2],319,[RX_RSSI:-36]
397,[Sender:2],319,[RX_RSSI:-36]
398,[Sender:2],319,[RX_RSSI:-35]
399,[Sender:2],319,[RX_RSSI:-36]
400,[Sender:2],319,[RX_RSSI:-36]
401,[Sender:2],319,[RX_RSSI:-36]
402,[Sender:2],313,[RX_RSSI:-36]
As before, the very first and the very last voltage measurement in the series is a double-match.  The ones in-between are all single-shot. 

Here's another piece of data that may (?) have relevance: the time needed to purely Tx the 60 byte payload (not counting the time it took to load the payload into the FIFO, but purely the Tx part) was about 2160uSec, or a little bit more than twice as long as for a 3 byte payload.  That is to say, with the FIFO already loaded, it takes 2160uSec from the moment the command is given to the radio to enter Tx mode to the time the PacketSent flag is detected.  That is the same interval over which all of the single-shot voltages are measured.  So, a bit more than twice as long to send a 60 byte payload than a 3 byte payload, even though the 6 byte payload contains 20x as many bytes.  Obviously, the frame size itself is bigger than the payload itself, but apparently the RFM69 takes quite a while (relatively speaking, given that the bitrate is 300kbps) to spin up and be ready to Tx.