Heatermeter on battery success!


 
ScottS said:
if i was just using the heatermeter as a thermometer and have no fans how long do you think this would last?
Click to expand...

Simple math says you should get about ~15 hrs if you run the battery flat and the voltage stays close to 12V till the end.

Heatermeter without a 12V load will consume about 250ma at 12V with a Wifi dongle installed and backlight set at 100%.
(You can reduce by 40 or 50ma by turning off backlight off or setting at 10%)

Battery rated at 3800mah @ 12V.

3800/250=15.2
 
I've been grabbing old laptop batteries from work that would otherwise end up being discarded. Most of them have 6 x 18650 Lithium Ion 3.7v cells in them.

Here's my haul so far. I'm thinking of making some high amperage 12v ( 14.8v ) packs with them. Should be able to power my heatermeter for a few days!

yqqXRz2l.jpg
 
We use to use 2 batteries per buoy called 12 volt longpacks. They where 10"across by36" high and had 100's of D cell's in them, weighed 95 pounds and would run the 12 volt buoy lite for a year and where changed out each winter with lots of life left in them. We would run old car radios off 1 for 4 years with no problem, wish I still had one to run my HM.
 
Chris B_Aus said:
I've been using one of these:
https://www.amazon.com/exec/obidos/ASIN/B00MF70BPU/tvwb-20

Using a rotary offset damper i get about 24 hours at 220 - with 100% fan it lasts about 14.
Click to expand...

Was looking at those, and will probably get one, however, one of these multi-function jobbies is also appealing. My only question is the Ah rating. It's advertised as 26,000 mAh, but how do you tell at what voltage that is? I would hope it's at 12v, since that's the natural voltage of this thing (in/out), but I suspect that it's marketing, and the true value is 0.85*5/12*26000 = 9208 mAh. I guess that's bigger than the one Chris B_Aus listed, but want to be certain.

Thanks.
 
I've just tested the current draw on my build from a 12V SLA battery. Figured it might be useful to someone. Had to use the meter at amp range rather than milliamps, so allow a little variance.

Setup: HM 4.3 mated to a RPi v3 using the internal WiFi. Standard blower attached - no damper.

LCD at 0% brightness, fan speed at:

100% = 370mA
90% = 350mA
80% = 330mA
70% = 300mA
60% = 280mA
50% = 250mA
40% = 230mA
30% = 220mA
20% = 190mA
10% = 180mA
0% = 120mA


Idle with LCD brightness at:

0% = 120mA
10% = 120mA
20% = 130mA
30% = 130mA
40% = 135mA
50% = 140mA
60% = 140mA
70% = 150mA
80% = 150mA
90% = 150mA
100% = 160mA
 
RalphTrimble said:
I never noticed that about rechargeables... At any rate, my point was 8 X 1.2V = 9.6V, not 12V. I guess that just means the blower will run slower at 100% output, 'cause I can't think of anything else that uses 12V in the HM.
Click to expand...

yikes, I was about to create a new thread then found this oooold one which has the exact stuff I was looking at!

so 2ish years on... apart from the blower not running at full steam, are there any other negatives to running 9.6v?

Here's where my head is at the mo:

Plan A
I was thinking of running two of these in parallel to get longer life:
https://www.amazon.com/exec/obidos/ASIN/B00VE7HBMS/tvwb-20
(I was about to start wiring that up when i realised my 1.2v math was waaay off.)

Plan B
https://www.aliexpress.com/item/12V...-with-Free-Charger-and-Extra/32409744274.html
 
Jeremy_Pickett said:
so 2ish years on... apart from the blower not running at full steam, are there any other negatives to running 9.6v?
Click to expand...
It should be fine anywhere from about 6V up to 14V, but the Pi/HeaterMeter draw appears higher at lower input voltages in a roughly proportional manner. So like 160mA at 12V is 214mA at 9V (160mA * 12V / 9V).

The newer HeaterMeter kits with the white LCD draw a lot less current than the yellow-green LCDs too. The old ones were about 100mA (at 5V) for full backlight and the new ones are only 20mA at full backlight. That's only 8.3mA from a 12V supply vs 41.6mA.

Still, the math checks out that a pair of 8x AA holders in parallel may run the pit for 10-12 hours or so. The SLA 12V battery is a lot more practical I feel though because the higher voltage means less current draw for the Pi/HeaterMeter and you'll get full fan speed through almost the whole battery life. Even at full fan speed the whole time, a 4.5Ah 12V SLA battery will run at least 12 hours and isn't too giant a battery pack. 3S or 4S RC battery packs are also an option I suppose and a Pi Zero W draws less than half the power of a Pi 3 (just checked and a Zero W + 4.3 at idle with 0% LCD brightness is 61mA at 12V or 75mA at 9.6V).
 
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