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Topic: Arduino Nano v3 - battery power (Read 11351 times) previous topic - next topic

majinjeff

Hello everyone,

What would be the best way to power an arduino nano v3 with batteries for a relatively longer runtime?   I'm liking the idea of rechargeable batteries.

Peter_n

The Arduino Nano still uses 5V, while the microcontrol ATmega328p can run with lower voltages.

You can make a standalone Arduino. For example running at 3.3V with 8MHz.
Or you can buy a board that can run on batteries.
Search at www.adafruit.com for 'wearable' and 'charger'.

You can also use buck-boost converter to convert 3.7V to 5V for the Arduino Nano.

Do you want to use the Nano, or can it be something else ? With other boards, there are many more options.

Bianco


You can also use buck-boost converter to convert 3.7V to 5V for the Arduino Nano.

That's more efficient than stepping down from 7.2 to 5?

majinjeff

I already have 2 nanos, isn't there a way without stepping up or down voltages?  Like AA batteries in series?  I've read many forums about this and everyone seems to have a different idea.  For my usage, I'd like something I can plug in via USB that's rechargeable and lasts a few days.  And ideas?

Bianco

Then maybe you could find a USB powerbank using 3 or 4 Li-ion cells.

tylernt

#5
Sep 12, 2014, 07:38 pm Last Edit: Sep 12, 2014, 07:41 pm by tylernt Reason: 1
An 8MHz ATMega is happy with 2.7V but is still 5.5V tolerant. This allows direct connection to batteries that vary voltage as they discharge. For efficiency, a direct connection is preferred over any sort of regulator because no regulator is 100% efficient (some energy is always wasted as heat). For truly tiny loads (microamps), linear regulators can sometimes be most efficient but in most cases, a buck driver (dropping a higher voltage to a lower voltage) is the most efficient regulator. A boost driver (increasing voltage) is less efficient, and a a buck+boost driver (able to increase or decrease voltage) is the least efficient.

Alkaline batteries typically start out at 1.55V per cell, so using three in series starts out at 4.65V (4 alkalines in series is too much, though 4 NiMH/NiCd at 1.45V/ea or 5.8V is just barely within the 6.0V maximum). Alkaline/NiMH/NiCd batteries are typically done by 1.1V (or 0.9V for light loads), so your ATMega can pull almost all of the available mWh out of them.

There are some drawbacks to using a variable VCC. Your AnalogRead readings, for example, will be relative to battery voltage and not to any absolute reference unless you add an external reference or enable the internal 1.1V reference. Also, the resistor values you choose for external components, such as the current limiting resistor for a transistor base, will have to be a compromise when you use Ohm's law to calculate their values -- make sure it has enough current at 2.7V but not too much current at 4.65V.

Anyways, when it comes to battery power, I'd avoid any 5V/16MHz Arduino and any Arduino with a serial chip on it (Nano fails on both criteria). They're just not efficient. That leaves the 8MHz Pro Mini and possibly a couple others, or rolling your own with a ATMega chip.

majinjeff

Thanks for all the replies, I found a few items on eBay, one takes 18650 batteries and states a maximum of 10,000 mah,  but I wonder if it means total of the batteries or total capacity of the batteries in the series+parallel configuration of the pack

http://pages.ebay.com/link/?nav=item.view&alt=web&id=181164235936

casemod


Thanks for all the replies, I found a few items on eBay, one takes 18650 batteries and states a maximum of 10,000 mah,  but I wonder if it means total of the batteries or total capacity of the batteries in the series+parallel configuration of the pack

http://pages.ebay.com/link/?nav=item.view&alt=web&id=181164235936


I personally feed them with a single 18650 you can use a protection circuit between both.
I had zero issues running at 3.3V but for extreme conditions you may want to get a 8Mhz version or set the fuses to enable the 8MHz internal RC on yours. The second option uses far less power.

If you really need 5V, then same aproach but you can use a boost converter such as the LM2577 or similar. I use them and they cut at about 3V which is a dead cell anyway.

I have a signal generator with a nokia 5110 LCD and backlight that lasts about 72H continuous feeded by a 2000mA 18650 and sourcing 5mA to an external optocoupler. When the voltage gets below 2.7V the whatchdog resets the arduino and the LED's forward voltage is not met so the battery can still last a few days before the voltage gets too low to cause damage.

Just don't buy surefire/trustfire. Panasonic, Sanyo or no brand (OEM) are best.

tylernt

When Li-ion is involved, I'd definitely recommend sticking with a commercial/retail packaged device. All too easy to let the smoke and fire out of a Li-ion cell by overcharging or over-discharging.

casemod

#9
Sep 16, 2014, 12:05 am Last Edit: Sep 16, 2014, 12:07 am by casemod Reason: 1

When Li-ion is involved, I'd definitely recommend sticking with a commercial/retail packaged device. All too easy to let the smoke and fire out of a Li-ion cell by overcharging or over-discharging.


Did you miss:

Quote

I personally feed them with a single 18650 you can use a protection circuit between both.


A cell phone battery already has a protection circuit inbuilt too. Typically the 3 pins are temperature sensor (V+) and (GND)

I hear a lot of this horror stories about lithiums, Since 2005 I never had any issues with cells, unless one really wants to blow them (And during tests they vented before this).

I did had a few cells that got forgotten and went empty, but even if you neglect this a good charger will refuse to charge such cells. If people still charge them they do so at their will with a modified/non approved charger. Its not like they were caught at surprise. An empty cell does not pose any risk at all, unless you force charge on it. As for overcharge, again a good charger wont overcharge them.

I can recommend shoshine chargers.

tylernt

Lithium is fine if you know what you're doing. A lot of people don't, hence my attitude of caution.

Bianco

An empty cell does not pose any risk at all, unless you force charge on it.

If you're forcing a low current (<<1 A) charge on it and cut-off early (around 3.5 V) to switch to a proper charger, you're taking a risk?

casemod

#12
Sep 16, 2014, 01:22 am Last Edit: Sep 16, 2014, 01:25 am by casemod Reason: 1

An empty cell does not pose any risk at all, unless you force charge on it.

If you're forcing a low current (<<1 A) charge on it and cut-off early (around 3.5 V) to switch to a proper charger, you're taking a risk?


Yes. its not about the current. The cell may get shorted inside. If such happens (and you don't know when or if) it doesn't matter if you charged it at 10mA during 100h. You may potentially have up to 1A stored energy released in seconds

I recovered a few good quality cells, but then again i am assuming the risk when I do so. Some are in daily use with no apparent loss in capacity, others slowly self discharge, others never recover and others do short inside!!

There are special cases/envelopes for lithium batteries that are fire proof. The battery also needs to be in a vented place. Lithium can react with water/moisture, so another warning. Don't trow water into lithium. I tested that theory in 2002. Lithium cells were the latest fashion and so reports with fires so I wanted to see by myself. No the video below is not mine ;)

https://www.youtube.com/watch?v=ojGaAGDVsCc

Bianco


I recovered a few good quality cells, but then again i am assuming the risk when I do so. Some are in daily use with no apparent loss in capacity, others slowly self discharge, others never recover and others do short inside!!

One they've been through a few cycles, can you assume they're ok?

I recovered two batterypacks from my parent's electric bikes. Out of ten LI-ion cells in each, two where around 2 - 2.5 V (I think the BMS screwed up). I pushed them to 4 V before switching to an imax B6 chargeur. The ranges of the packs went from 10 km to 50 km and stabilized at that value.
Now...are they going to explode? XD

casemod



I recovered a few good quality cells, but then again i am assuming the risk when I do so. Some are in daily use with no apparent loss in capacity, others slowly self discharge, others never recover and others do short inside!!

One they've been through a few cycles, can you assume they're ok?

I recovered two batterypacks from my parent's electric bikes. Out of ten LI-ion cells in each, two where around 2 - 2.5 V (I think the BMS screwed up). I pushed them to 4 V before switching to an imax B6 chargeur. The ranges of the packs went from 10 km to 50 km and stabilized at that value.
Now...are they going to explode? XD


You need to take care with the self discharge. The BMS itself can hide that from you by balancing the faulty cell after each cell. If after a while the cell has returned to a good capacity and does not discharge or overheat during use, yes I would say its safe enough to use.

2V is the lower value for Li-ion and 2.5 is for LiFePO4. Assuming they were not below that then that is a full discharge and not really motive of concern.

The real danger with lithium batteries is if a pack is not balanced, when a cell capacity is extinguished the voltage drops and it is reverse charged by the current flowing from the remaining ones. This was number one culprit of faulty Ni-Cd and Ni-MH batteries in drills, for example. People had the mentality you should fully discharge the pack and some cells would be reverse charged a bit after each use, losing more and more capacity. This is not dangerous on this chemistries, but it would damage the cell.

On lithium this is likely to cause a fire and it will for sure damage the cell beyond repair. I would never use a cell that had experienced that.

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