# Short Battery Life

#### Nigel Goodwin

##### Super Moderator
Thanks. mike. The usage is down below 1ma now and wondering what may be the best way to power the thing. I would like to use AA batteries because they are easy to come by.
1mA is till fairly high, where is it going?.

As for batteries, how long do you want it to run before changing them?.

#### jack0987

##### Member
1mA is till fairly high, where is it going?.

As for batteries, how long do you want it to run before changing them?.
Well, I said below 1mA. It is actually 0.17mA under normal operation.
If put in sleep forever possibly less.

This is going on the mailbox. Easy to get at.
Six months or more would be nice, I guess.

#### Pommie

##### Well-Known Member
AA alkaline batteries are typically 2500mAh so they should last 2500/0.17 = 15 thousand hours = 612 days or nearly 2 years.

Did you manage to put the transceiver into sleep mode?

Mike.

#### jack0987

##### Member
AA alkaline batteries are typically 2500mAh so they should last 2500/0.17 = 15 thousand hours = 612 days or nearly 2 years.

Did you manage to put the transceiver into sleep mode?

Mike.
Thus far the only hardware change I have made is to remove the power LED.

In software, in a nutshell, this is what has been done:

Code:
#include <RFM69.h>
#include <SPI.h>
#include <LowPower.h>

// my code here

void setup
{
//my code here
}

void loop
{
// my code here
}
Presently, 4 AA batteries in series are being used for power connected to the RAW voltage input.
Since this will be outdoors, I intend to use lithium AA batteries to withstand the cold of winter.

Last edited:

#### Nigel Goodwin

##### Super Moderator
Presently, 4 AA batteries in series are being used for power connected to the RAW voltage input.
Since this will be outdoors, I intend to use lithium AA batteries to withstand the cold of winter.
I presume you're aware that Lithium AA's are 3.6V?, so you don't need 4 in series.

Here's some I've used today on some boards I've been building up:

These are Tadiran batteries, Lithium 3.6V, 2.6Ah and used for their long life (in excess of five years) and good in cold conditions - the boards will next be fitted in boxes, wired, and then potted.

The boards with no batteries are because I used all we had - but I think we ordered what we needed for this job? (it's hard to be sure, as we've already supplied part of the order from ready made stock - and I'm not sure how many that was). But I started populating boards until I ran out of 100K resistors, on the grounds we'll have some ready in stock for next time, rather than bothering counting the boards.

#### Pommie

##### Well-Known Member
Nigel, please swap the two boards in row nine so my OCD is happier.

Mike.

#### Nigel Goodwin

##### Super Moderator
Nigel, please swap the two boards in row nine so my OCD is happier.

Mike.
The RHS one is a single board (which I rather foolishly fitted the battery to first), the rest are all 3x2 panels.

Anyway, I've split them all apart now, and dropped them in the boxes (and wired 5 so far), the boxes have been drilled already, and the correct number - same as the number of batteries I had.

#### jack0987

##### Member
I presume you're aware that Lithium AA's are 3.6V?, so you don't need 4 in series.
Thanks. I did not. Have not got that far yet and just working with what I have on hand.
Using lithium, what might be the be best way for me to do it?

BTW: nice work on your boards.

#### Nigel Goodwin

##### Super Moderator
Thanks. I did not. Have not got that far yet and just working with what I have on hand.
Using lithium, what might be the be best way for me to do it?
The lithium batteries hold their voltage really well, and then suddenly die quite quickly - it's a far flatter discharge curve than most other types of batteries. You could quite probably feed your design directly from the 3.6V battery, or use a LDO regulator to provide 3.3V from it.

#### jack0987

##### Member
The lithium batteries hold their voltage really well, and then suddenly die quite quickly - it's a far flatter discharge curve than most other types of batteries. You could quite probably feed your design directly from the 3.6V battery, or use a LDO regulator to provide 3.3V from it.
Hi: I need to revisit this topic. After my previous work here, I only extended my battery life about 50%. so, instead of them dying in about a week and a half, I am getting about three weeks.

The first thing I would like to do is try to power my device with lithium rechargeable batteries.

Can I safely power it directly from the 3.7 volt ones wired in parallel?

#### dknguyen

##### Well-Known Member
Hi: I need to revisit this topic. After my previous work here, I only extended my battery life about 50%. so, instead of them dying in about a week and a half, I am getting about three weeks.

The first thing I would like to do is try to power my device with lithium rechargeable batteries.

Can I safely power it directly from the 3.7 volt ones wired in parallel?
Weren't you using four AA batteries before? That's probably 1.5V per battery unless they were NiMH then they are 1.2V. Either way that works out to be 6V or 4.8V, both of which are higher than 3.7V so I would think would be okay as long. At the very least, no damage should occur even if it doesn't work. Whether or not it will function work on whether your boards are using LDOs or regular linear regulators, and whether anything on them actually needs ~5V.

#### jack0987

##### Member
Weren't you using four AA batteries before? That's probably 1.5V per battery unless they were NiMH then they are 1.2V. Either way that works out to be 6V or 4.8V, both of which are higher than 3.7V so I would think would be okay as long. At the very least, no damage should occur even if it doesn't work. Whether or not it will function work on whether your boards are using LDOs or regular linear regulators, and whether anything on them actually needs ~5V.
Yes, I am currently using 4 AA batteries wired to the RAW power input.
My thinking is to wire the lithium batteries to the 3.3 volt power input and this may be a better way.

#### dknguyen

##### Well-Known Member
Yes, I am currently using 4 AA batteries wired to the RAW power input.
My thinking is to wire the lithium batteries to the 3.3 volt power input and this may be a better way.
Oh, so you're worried that if you bypass the regulated input and direct wire the 3.7V Lithium cells to the 3.3V components it might damage them? I've never done that so I'm not sure but it seems to be common practice. At least, Nigel said you might be able to get away with it. If you're worried just toss a schottky diode in series to remove 0.5V, or an LDO.

#### Pommie

##### Well-Known Member
Remember fully charged lithium are 4.2V.

Mike.

#### dknguyen

##### Well-Known Member
Remember fully charged lithium are 4.2V.

Mike.
Right. You could also use LiFe or A123 cells. Fully charged those are 3.6V

#### jack0987

##### Member
I have two objectives. Add more amp hours and use rechargeable lithium batteries.
Originally, I thought I could get AA rechargeable lithium batteries, but I now believe that to be a mistake.

From what I am reading, the Arduino pro mini RAW input can be powered from 3.4 volts to 12 volts.
Using 18650 cells wired in parallel connected to the RAW input may be the best way for me to go.

Also, the 18650 cells seem to come in a range Amp Hours.
Should I choose the ones with the most?

#### dknguyen

##### Well-Known Member
I have two objectives. Add more amp hours and use rechargeable lithium batteries.
Originally, I thought I could get AA rechargeable lithium batteries, but I now believe that to be a mistake.

From what I am reading, the Arduino pro mini RAW input can be powered from 3.4 volts to 12 volts.
Using 18650 cells wired in parallel connected to the RAW input may be the best way for me to go.

Also, the 18650 cells seem to come in a range Amp Hours.
Should I choose the ones with the most?
Yeah, the more industrial-type of batteries come in cell sizes different than those the consumer normally sees.

As for choosing the most amp-hours...that's up to your wallet...I guess. If the chemistry is the same and the cell size is the same I wouldn't expect mAh to vary that much between manufacturers. Sometimes there is a tradeoff between C-rating and capacity, but C-rating definitely isn't a priority in your case. Can you link the cells you're looking at?

#### Nigel Goodwin

##### Super Moderator
A lot of the claims for 18650's seem to be fairly imaginary, the 'standard' sort of rating is about 2.6Ah.

Have you done nothing to reduce consumption?, other than remove the unwanted power LED?.