External Battery Power


 
J

JNeillIII

TVWBB Member
Does anyone have any experience with using the HeaterMeter/LinkMeter using a battery pack? What would be the minimum requirements to be able to power the HeaterMeter using a battery pack to be able to have enough power to run a complete smoke cycle? I was thinking of getting something like this, but figured I would check here first.
 
I have made mention of powering the HM with a battery in the past and Bryan had laid out the details on power consumption at that time, from which you could calculate how much capacity you need in the battery. Unfortunately I don't recall exactly what thread that was in. It might have been in the development log thread, or you could try to search it out, or hopefully Bryan will chime in here and repeat the details about power requirements for you....

It would be kinda slick to have a battery pack that could run the HM for a whole cook, for those guys who take their smoker out of the back yard to campgrounds and parties etc. I know I take my smaller smoker around a bit and getting power close to where I want to set the smoker is always something I have to prepare for. If I had a capable battery pack all I would need to do is make sure it's charged, that would give me peace of mind when taking the smoker on the road to unknown locations, so I like the idea....
 
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Ballpark figures, but a model B Pi pulls ~700mA with wifi, an A pulls closer to 400mA with wifi.
HeaterMeter and all the LEDs and everything 50mA, add 35mA for RF.
Those are all at 5V, so divide them roughly in half thanks to the 12V switching regulator.

The fan is about 200mA at 12V.

So maybe 500mA for a rPi model A+HeaterMeter? Multiply by the number of hours you think you'll be cooking and that should give you a ballpark number. 24h * 500mA = 12000mAh

EDIT: Using a servo damper with the A model could probably cut that by more than half.
 
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I have a jump pack around that has a cig lighter socket - had plenty of cig lighter plugs around with barrel connectors already on them, so, I use that. If you don't have any in your warehouse, easy enough to solder up.
 
I've got a couple of these that I use for my kids power wheels that I'm looking at using. Just finishing up and ironing out my build but I plan on giving this a real world test and see if I can manage a 15 or so hour Brisket cook.
 
Real world power usage. I just measured my Model A+Wifi+HeateMeter running at 12.0V, LCD backlight 10%.
During boot: 165mA max
Idle: 125mA-155mA
Blower on 10%: 230mA-250mA
Blower on 100%: 330mA-350mA

LCD Backlight 100% adds ~25mA

With the blower off, the power usage drops proportionally with increased input voltage. For example, increasing voltage 10% to 13.2V reduces current usage roughly 10%. Therefore, a lead-acid battery would give you more bang for your amp-hours than a LiPo, because they're actually more than 12V output. The blower is rated up to 13.8V too so that should be ok. The 12V 7.2Ah battery linked above should get you 20 around hours of full fan speed runtime.

Using a servo instead of a fan should increase that time significantly. I have a hard time measuring the servo power draw over time because it pulls somewhere on the order of 700-800mA when it moves, but it only draws that for a short burst.
 
It would be pretty inaccurate I think because (at least the one I have) isn't that great at measuring current that low. It makes sense because their burden resistor is meant to handle up to 10A so it would give us the same ballpark. That and we don't know how efficient these cheapo power adapters are. I think all we can say without trying it is that the servo draws a lot less, but has really high bursts of current.
 
So I guess a real world "plug in a battery and go" will be the ultimate test of how much juice you need to do an overnight cook in the end....
 
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