Best battery for the micro projects.

[mramos1]

I have done 2 projects in the last couple weeks. Both require battery operation.

I have ordered 38Khz Xtals to slow the chips down, waiting on them (glitchbusters has not responded for two days, may never get them). But here is the question.

What is the best small battery? I have searched the net for mha ratings, and all I get are people that are selling batterys and no specs anywhere.

I have about 300-400mha of power now and it is not enough. I need small in size or fairly small. I was looking at the 6VDC photo batterys but could not find the ratings.

Anyone have a good fairly small battery ideas, that have 3000-4000mha? Price is not
major.

 

[audioguru]

www.energizer.com .
Click on Technical Info on the 1st page then select a battery type to see different sizes and detailed datasheets. Their non-rechargable Lithium AAA and AA cells have extremely high mA/hr ratings (and a pretty high price).

 

[dknguyen]

batteries

Look for antweight combat robot batteries. THey have specs. Your choices for rechargeable are pretty much between NiMH, Li-Poly and Li-Ion.

If you are looking at regular Duracell, Energizer-type AA and AAA batteries, NiMH-type cells are probably the best you will be able to get. The Energizer NiMH cells have mAh listed (they have a greenish-silver color packaging). I believe its 1.2V per cell at around 2000mAh for AA (could be AAA, I forget). You would need quite a few though to get 6V@4000mAh.

Beyond that (and other RC hobby NiMH cells) you have to maybe look at Li-Ion and Li-Poly packs. But they require a specialized charger (like all batteries) and cost a lot. Li-poly are small, light, high capacity and discharge, and cost a lot. Expect to pay $85~$120 for a Li-Poly pack 7.2V@4mAh.
**broken link removed**

Economically NiMH is your best bet, just because Li-Poly fits your requirements but they cost a fortune for powering something as low current as a uC. They were made to run motors.

 

[mramos1]

dknguyen: Thanks for the input. I guess I did not get all the info on the post. They are non-rechargable projects. I will look at the bot batts though just to see have crazy they dan go. But when I said price not an issues, it was under $10 as well. hehe..

Audioguru: Right on the money. That is what I was after. You read between the lines. Thanks.

I will get the slower Xtal, that will help a lot as well. Nigel mentioned that in an old post and I read the datasheets and man low speed really save a lot of power.

 

[DirtyLude]

You might want to look at N sized cells as well.

Do you drop the thing into sleep as much as possible? Even if you turn the crystal off for a few short moments, it really cuts the power down. Sometimes you can rely on just the watchdog timer to do some tasks or if you're waiting for input, like a button, or serial input you can do a wake from sleep on the input. I have a project running on a coin cell that's lasted for a couple months.

 

[philba]

This isn't answering the question but I agree with DL - have you spent any time on reducing current consumption? getting better batteries is good but using them less is even better. clearly, there are things that you can't do anything about (like motors) but it's always a worthwhile exercise. makes you a better engineer.

From your OP, I'd gues you have done uC based projects so there are a lot of things that you can do to reduce consumption, like DL said. use sleep when you can, turn off things that suck power, slow the clock down. every little bit helps. Also, look at all your circuits from the perspective of reducing current consumption. For example, if you are using dividers for a reference voiltage, make them higher (a 1K/1K divider produces the same voltage as a 10K/10K but at 10X the current drain). Using lower power parts is always good. Some peripherals have shutdown or low power modes.

Finally, get familaiar with Pchannel mosfets - you can use them to turn off major sub-systems. For example, you can use one to shut power down to things like transmitters when not in use.

 

[mramos1]

DL, was looking at the N, and the photo batteries. I have a (do not recall the letter) 6V, looks like a AA almost cut in 1/2 I am using in one unit.

Philba, Neither one have motors or anything bleeding them, mostly code running in a loop waiting on a counter. One circuit does charge a cap every 1 minute and check it. And I have a regulator on one that I am about to remove since the uC runs 6V to 4V .

I ordered some P and N mosfets from glithbuster if I can get the guy to contact me. I want to use an LDR, pot and P-channel to fire the whole thing up (there would be a small draw, but not too bad). One only needs to run when there is a certain level of light. I also ordered some new 12F509's as well.

I was going to sleep, but I can only sleep 2 seconds at a time with the chip I have, I guess I can do that and keep a counter for when I need to really run the code when I wake up. But 2 seconds seemed like it would save so little. I will try that today, since I took the day off.

 

[Nigel Goodwin]

I was going to sleep, but I can only sleep 2 seconds at a time with the chip I have, I guess I can do that and keep a counter for when I need to really run the code when I wake up. But 2 seconds seemed like it would save so little. I will try that today, since I took the day off.

Using sleep will save you a great deal, it might only be 2 seconds or so (usually around 3.5 seconds max for the WDT), but you only need to run a few uS each time it wakes - mainrain a count of the number of times it's woken up, and only run the program every so many wake cycles.

This should easily drop PIC consumption to less than 1% of what it was.

 

[philba]

this is a big disadvantage of PIC16s - they have very little granularity in what you can turn off to save power. Nanowatt PICs are a bit better. The PIC18s are better still but AVR and MSP430 are much much better.

With PIC16s, you might want to design your application to not run timers constantly. I've seen designs that use low power external timers to wake the micro up periodically.

Something I do - set up a DMM in mA mode in series with the power source while I am debugging and generally fussing with the HW. Keep an eye on the consumption. It's quite instructive in what sucks the power. it also will allow you to catch high current consumption that indicates shorts or other errors.

by the way, linear regulators eat batteries for breakfast. forget them. either size your Vcc needs to run directly off batteries (3 or 4.5V works well) or use a switching regulator.

 

[mramos1]

Philba.

Both projects are AVR. I can drop 6V (4xAA) in the box with it. Do the sleep and counter idea as Nigel mentioned and see what that gets me, it might be enough.

And the regulator is leaving the unit as well. Originally it was going to hook to a car battery, now it is to be standalone.

I like the DMM idea, then I can see the load and see what the sleep and WDT save me as well.

 

[philba]

Philba.

Both projects are AVR. I can drop 6V (4xAA) in the box with it. Do the sleep and counter idea as Nigel mentioned and see what that gets me, it might be enough.

And the regulator is leaving the unit as well. Originally it was going to hook to a car battery, now it is to be standalone.

I like the DMM idea, then I can see the load and see what the sleep and WDT save me as well.

4 AA's fresh will be a bit above 6V (6.4 approx) though load will pull it down. I would use 3 AAAs for 4.5V. AVR makes a lot of difference. There are a ton of things you can do to cut down current consumption. You should be able to run months on a set of batteries.

 

[Nigel Goodwin]

AVR makes a lot of difference. There are a ton of things you can do to cut down current consumption. You should be able to run months on a set of batteries.

No reason not to use an AVR, but I don't see how it makes 'a ton of difference'? - using either AVR or PIC I would expect the batteries to probably last 12 months?.

PIC16F628A running at 32KHz and 5V

Typical running current 28uA

 

[Nigel Goodwin]

AVR makes a lot of difference. There are a ton of things you can do to cut down current consumption. You should be able to run months on a set of batteries.

No reason not to use an AVR, but I don't see how it makes 'a ton of difference'? - using either AVR or PIC I would expect the batteries to probably last 12 months?.

PIC16F628A running at 32KHz and 5V

Typical running current 38uA, typical sleep current 0.2uA

 

[mramos1]

The crystals are on order I think. I hope it goes that long. That would be great. For both units. I ordered 16F628A's as well..

 

[Nigel Goodwin]

The crystals are on order I think. I hope it goes that long. That would be great. For both units. I ordered 16F628A's as well..

They have an internal 32KHz oscillator.

 

[mramos1]

Yes, but I want to drop them on the AVR units as well. They are 1Mhz internal and it is sucking the life out of the batteries.

Looks like Microchip has come a long way.

 

[philba]

No reason not to use an AVR, but I don't see how it makes 'a ton of difference'? - using either AVR or PIC I would expect the batteries to probably last 12 months?.

PIC16F628A running at 32KHz and 5V

Typical running current 28uA

have you looked at the power saving features of the AVR? the PIC16 has very little by comparison. the AVR has multiple levels while the PIC16 has basically one. On the AVR you can power some peripherals while shutting down others. The PIC16 really is a rather dull knife compared to the AVR line. PIC18 is closer but still not as good.

Yes, If you can use sleep in your PIC16 application, they are pretty close but it's not always possible and to do anything more sophisticated the AVR is way ahead.

 

[Nigel Goodwin]

Yes, but I want to drop them on the AVR units as well. They are 1Mhz internal and it is sucking the life out of the batteries.

Looks like Microchip has come a long way.

From when?, the 16F628 is from last century when it replaced the 16F84, the later nano-watt 16F628A is just a later silicon revision - but the original 16F628 had the 32KHz internal oscillator.

Don't some AVR's have it?, they copied everything else (including a three letter name).

 

[bloody-orc]

AVR is way more economical even when running on 8MHz. i did a test on who's gonna run longer, ATtiny26 or pic 12Fxxx. guess who won. avr ofcource. also it's a lot faster when ran on the same frequency. but oh well it is a never ending battle.

PS. avr is way better when it comes to C than PIC and is way easyer to use cause all of them have the same or at least SIMILAR adresses (not like pic, where every pic has it's own way to storage stuff etc, so that before writing anything for it i have to read through the whole datasheel wheres when working with avr everything is the same.

 

[Nigel Goodwin]

AVR is way more economical even when running on 8MHz. i did a test on who's gonna run longer, ATtiny26 or pic 12Fxxx. guess who won. avr ofcource. also it's a lot faster when ran on the same frequency. but oh well it is a never ending battle.

As they don't run the same code, or the same hardware, doing comparative power testing is rather difficult!.

PS. avr is way better when it comes to C than PIC and is way easyer to use cause all of them have the same or at least SIMILAR adresses (not like pic, where every pic has it's own way to storage stuff etc, so that before writing anything for it i have to read through the whole datasheel wheres when working with avr everything is the same.

I believe the 18F series PIC's are also optimised for C, and also run as fast as AVR's do (or faster).

Perhaps you might try counting the number of PIC's in the world and the number of AVR's

You can see why Atmel jumped on the PIC bandwagon!.