Battery requirements for node?

[WRYZ886]

Boefang BF-888 and pi3b+ Node. What size battery would be required to good run time. 5vdc for pi and 3.7 for 888?

Thanks for help

[SteveShannon]

42 minutes ago, WRYZ886 said:

Boefang BF-888 and pi3b+ Node. What size battery would be required to good run time. 5vdc for pi and 3.7 for 888?

Thanks for help

What are the current requirements during receive and transmit?

What duty cycle do you require?

What do you consider a “good run time?”

How do you intend to provide the two different dc voltages from a 12 volt battery? 

[BoxCar]

1 hour ago, Sshannon said:

How do you intend to provide the two different dc voltages from a 12 volt battery? 

Batteries with different voltages and capacities are available from Hobby stores catering to the remote control people. I used 3.2V, 7.4V, 12V batteries in the airplanes I used. Capacity ranged from 250ma to greater than 12A. These batteries do not have an internal balancing circuit, so one has to be provided externally. RC battery chargers have them built in.

[dosw]

2 hours ago, WRYZ886 said:

Boefang BF-888 and pi3b+ Node. What size battery would be required to good run time. 5vdc for pi and 3.7 for 888?

Thanks for help

The PI3B+ uses 2.1A at 5vdc, which is 0.875A at 12vDC.

We don't know what the power draw of the BF-888 is at 3.7vDC, but let's take a guess:

Let's just guess that passive listening, the 888 consumes 150mA at 3.7v, or .0046A/hour at 12vDC.

Let's say it transmits at 5w, so 1.5A/hour of transmission at 12vDC.

Now give a duty cycle of 10% for transmitting (which is a lot but not impossible).  That's .15A/hr.

 

Add it all up. Consumption is 0.875 + .15 + .0046 = 1.03A/hr. Add some overhead for voltage conversion loss (heat), and for just "my paper napkin math is wrong", and you're at 1.5A/hr.

 

A fire alarm battery is usually 7AH or 9AH. You shouldn't run lead acid batteries below 50%. So a lead acid fire alarm battery would last 2.3 to 3 hours. An RV Group 24 battery is 75AH, and with the same 50% safe working range, would last you 25 hours, or roughly a day.

 

A 100w solar panel will get you anywhere from 15-35 amps per day in recharging. So with a 100w panel and a Group 24 battery you could theoretically go indefinitely, though you would be a lot safer with a 200w panel and a Group 31D battery.

 

Sounds like you might need more than a hobby battery, but we don't really know the duty cycle you're anticipating.