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Topic: Confused about Lithium Ion (Read 1 time) previous topic - next topic

robert_tork

Guys, thanks for your replies.

It is true that my requirements might seem off the cuff but I'll build up on that in just a bit.

When I said lipstick-size I meant this, so no, I'm not coining up any new terms as you see ;)

And when I mentioned both Arduino boards and the Pi I wasn't necessarily meaning I'd run both on the same power source (except if we take those dual-charging -aka dual output- external batteries, like one of the products in Anker's Astro line). I just wanted to state I'd be requiring both the nowadays oh-so-common 5V (RPI, Uno) and the back-in-the-day common 3.3V (Due). Although I do know 3.3V is common for microcontrollers.

The deal about this is, and yes, I might be "off the cuff" here or a little keen, but it's simple:
1. I can't spare the money to make small orders from US. (other countries I've ordered with success is China, which is cool but shady for this purpose, and the UK, who screwed me over -to put in very mild words- with the amazing service of UPS International that basically charged me more in handling taxes than the price of the product itself, so no more UK EVER for me, unless it's Element14, who shipped via International Airpost -no extra price- but that could have been a fluke and they just use UPS).
What this means is that I must order things in a way that I won't be requiring extra, or else I have to resort to obtain them locally, because of real high shipping costs. Locally I cannot obtain anything worthy (here you ask for microcontrollers and they show you all variations of PIC, you mention Arduino and they think you are making a term up).
With that said, I'm going to order some parts from SparkFun and Digikey, and I'm ordering the batteries as well. I know for some of you that might seem ridiculous as you can make 10 orders a month from several "local" shops (local being Amazon, Digikey, etc etc) and you don't worry for anything else. For us, people who import, things are different, so just try to imagine it's hard, that's all.
2. I'm not worried that this project (or projects actually) will run 24/7 for a year, so I don't need crazy requirements like the guy who used a solar panel powered thingy the size of two car batteries and had his RPI run for months, except for some days when there were no sunny skies (I think he's Canadian) and the RPI just turned off while the battery power would recharge.
So.. with that said... I think even for a n00b like me at electronics, it's no rocket science to google the literally hundreds of tutorials on the subject "how much power you need" and make all the calculations and else. That is the easy part and I already researched on similar projects, hence my current "knowledge" on the matter and my affirmation that anything around 3000 mAh (could be 2000 mAh as well) with different "average" voltages (3.3, 5, 7.4) will work no matter what. Yes I might add more servos later and so on so forth but that got me no worried, I won't be making a Terminator nor a QuadCopter, so... I'm fine.

With that out of the way you guys might be right in that I might be throwing away the opportunity to give NiMH a chance.
I read a little more on Lithium-Ion and apparently, I'm lucky my cellphone hasn't exploded on my face?  :smiley-roll:
So yeah, I think I answered my question (unless that article is BS), and basically, Li-Ion is as dangerous as Li-Po.

So I guess, with Li-* out of the way (LiPo don't have good reputation and I don't want to buy some 80 USD charger, tho' I know Adafruit sells some cheaper breakout chargers but those are for single cell LiPos and for some reason I ruled them out earlier on), the only choices are
1. Use external batteries like the Anker Astro lines (which I don't like so much because of size that might impact mobility, although they could probe to be great on the protoboard, aka, the design phase).
2. Use regular AA or AAA non-rechargable batteries, which I totally rule out because I don't use a non-rechargeable battery since the dawn of time, except for those funny-branded ones that come shipped with remote controls and so on. And yeah, I just don't like non-rechargeable stuff.
3. Use NiMH batteries, but I think I'll have to investigate if I can get something like 7V by running them in serial (and is it safe???) and it they pack enough amperage, around 2000. And of course, if they are safe to use or they are as dangerous as LiPos and Li-Ions or what...


James C4S

Are you just trolling?


And when I mentioned both Arduino boards and the Pi I wasn't necessarily meaning I'd run both on the same power source

"And later on I wanna use the same alternative for a Raspberry Pi"
That sure sounds like you want to use chose a power source and use it for both Arduino boards and a Raspberry Pi.


I just wanted to state I'd be requiring both the nowadays oh-so-common 5V (RPI, Uno) and the back-in-the-day common 3.3V (Due). Although I do know 3.3V is common for microcontrollers.

I think you have your timeframes backwards.


who screwed me over -to put in very mild words- with the amazing service of UPS International that basically charged me more in handling taxes than the price of the product itself

UPS doesn't charge Taxes, Governments do.


What this means is that I must order things in a way that I won't be requiring extra, or else I have to resort to obtain them locally

For the second time, where is locally?


With that said, I'm going to order some parts from SparkFun and Digikey, and I'm ordering the batteries as well

"I don't live in the US and getting stuff is not that easy wherever I live."  So US sources are back on the table?


I know for some of you that might seem ridiculous as you can make 10 orders a month from several "local" shops (local being Amazon, Digikey, etc etc) and you don't worry for anything else. For us, people who import, things are different, so just try to imagine it's hard, that's all.

You're making some pretty big assumptions in these statements which isn't true for most of the people on this forum.  You seem to like guessing at what people are thinking.  Maybe that's why you won't give any actual details because you expect everyone to guess what you are thinking/doing?


I'm not worried that this project (or projects actually) will run 24/7 for a year

This might be the first actual requirement you've stated so far.


Your long strings of useless commentary and seemingly contradictory statements is making it difficult to find your actual questions. Good luck on your project, whatever it is since you apparently won't say.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

robert_tork

No, don't say that, I'm not trolling, and I apologize for your time wasted trying to help.

When I say I wanna use the same alternative for the RPI, it means I wanna use, say, TWO NiMH, one for Arduino and one for RPI, two Li-Ion, one for the Arduino and one for the RPI. Catch my drift?
I would want to use both RPI and Arduino in the same project, hence i mention the RPI. And I just want to state that I know, using the same power source for both is a mess, so I'll just use separate power for either, but likely with same technology, that's what I mean.

Yes governments charge taxes, I know.
I'm just stating that I wanna get this done with and pick a technology of batteries and make the order, because I know people would recommend things like "state your exact -with a +/-1% miscalculation- power requirements and then worry later on about the batteries and first just run them via AC", so I want to explain this is not necessary and I don't need to spend 2 years on the project to already know this won't be a web server running 24/7, nor something that is going to save lives and cannot, for any reason, shut down and so on.
Projects include "starter" robots and music-related things. It's not really important.
It won't be anything that flies, so I don't need for instance the "help" of those LiPos that "would rather die than limiting voltage" or something that I read are popular in the RC world so that the plains tend to crash less often.
So, even if it sounds crazy that a n00b like me is making assumptions on what power I'll require, those are based on lots of other user experiences that I've read, with similar projects. The problem being they tend to use LiPos or when they use Li-Ion they obviously just quickly explain the power consumption and not the steps to take the decision (except for some projects with servos).

Locally doesn't matter where it is. I'm not asking for help on shipping or anything, so it's completely irrelevant.

I never said US was "out the table". I just said it was not easy for me to order "cool stuff" from overseas, that's what I mean, and that (as I explained later) when I do, I must make an "all-star" order with all I'll require. Ordering a 7 USD battery a month later is not an option because of taxes and shipping costs.
It is irrelevant as well, just put there to explain why being so keen on sorting out the battery "technology" I'll be using, now, and not later.

You're right that I might be over-generalizing but since my reply was given towards you... a texan.. I assume, and lemme make a wild guess that you have no problem ordering from say, Amazon or Sparkfun and just getting done with it, not worrying if your order is divided in 5 small shipments that will arrive at any given time over the course of a couple weeks and so on... which is a problem for me, and my US courier.
I know that this is an international forum with users in a similar position to mine, in countries where technology is hard to come by, specially if we're talking about electronic parts for hobbyists.

You're absolutely right that I'm making "useless comentaries", it's just I'm a long time forumer, and just didn't want to obtain the tipical answer "Oh, just use LiPos". Not that it's a bad answer, just that, like I explained before, I already ruled out by choice.

Leaving aside my useless, sometimes kinda retoric gibberish, I thing the original question was:
Are Li-Ion reliable? Are they less/more reliable than LiPos? Will I get the same chances to have them explode my apartment if I don't oversee the batteries while they charge? Can I use regular cellphone/camcorder ones with the original charger? And do their use in my circuit, needs special needs like a voltage regulator that does A or B to avoid them going under voltage and exploding or burning my protoboard or something along those lines?

Then I think I answered myself by researching more and basically kinda discovering that being Lithium-based, Li-Ions are just as dangerous as LiPos (I might be wrong, I don't know for sure).

So, you guys suggested NiMH.
I ask the same, are they more/less reliable than LiPos? Do I need special considerations when using them in my projects? Do they stand a chance to explode?
And since I don't know much about them, can they provide voltages up to 7.xV? Can they provide a "cool" amperage such as 2000/3000 mAh.

wizdum

#8
Jan 06, 2013, 01:18 am Last Edit: Jan 06, 2013, 01:21 am by wizdum Reason: 1
Ok, I have a bit of battery background from my Airsoft experience, so i'll give it a shot. The primary difference between LiPo and NiMH batteries is the  power density. You can store a lot more in a LiPo of equivalent weight to a NiMH. This is particularly useful for RC airplanes and lightweight portable electronics. LiPo batteries also have the advantage of being able to deliver all of their power more quickly, which is useful for running electric motors. They also hold their charge much longer (low self-discharge rate).

The biggest downside to LiPo is the charging circuit. You need to carefully monitor every LiPo cell during charging and discharging to ensure that they discharge evenly, and do not fall below a certain threshold (usually 3.0v is safe). Once a LiPo cell becomes discharged below 3.0v, it can be difficult, dangerous, or impossible to recharge it. This is where the "LiPo fires" come from that you have heard about. If one cell is damaged, or its voltage falls below the voltage of the other cells, the other cells can discharge rapidly into it and cause a fire.

A typical NiMH cell is 1.2v, a typical LiPo cell is 3.7v. You can chain NiMH cells together easily. LiPo cells should never be chained together, you need to purchase a pack that can provide the appropriate voltage.

Personally, I would not use a LiPo battery pack in anything that I do not watch during charging. The LiPo packs in most consumer electronics go through a lot of testing, have substantial monitoring hardware, and have very specific charge/discharge rates. Even then, fires are not unheard of.

For NiMH cells, I recommend Sanyo Eneloops. They seem to have the best life/low self-discharge rate.
"Anyone who isn't confused really doesn't understand the situation."

Electronic props for Airsoft, paintball, and laser tag -> www.nightscapetech.com

lemming

#9
Jan 06, 2013, 02:50 am Last Edit: Jan 06, 2013, 09:21 pm by lemming Reason: 1
The current requirements of the RPI and the Arduino are at two different ends of the spectrum, therefore if you do not want to consider different battery types for either then there will be a big compromise optimising the weight & power.

Without specifying what your project is (why the secrecy?) it is hard to get a handle on what you require. 'Mobility' for your project could mean anything from the device embedded in your clothes to one sitting in your car/boat/mower etc.  If mobility is not critical and you need to run this thing for more than 1-2 hours without charging, you may want to consider using a 12v 7.2 AH gel-cell battery like those in alarm systems. Heavy but can deliver the grunt required for a project that with all parts included may be pulling >800 ma. There is no memory effect either.

The problem with running LiPos in series is highlighted in the previous post but running NiMh in series can result in balancing problems and memory effect problems over time.

I know that you don't like Li* batteries but I have used over 20 of these:
http://www.hobbyking.com/hobbyking/store/__18560__Turnigy_5000mAh_1S_20C_Lipoly_Single_Cell_.html
coupled with these:
https://www.sparkfun.com/products/11231
to provide a safe charging solution with a stable 5 or 3.3v (selectable) irrespective of the charge state of the battery. You would need two for the current needs of your project or use separate, high current buck-boost converter.
These setups have had not had any failures or meltdowns to date.

By using a single cell the danger highlighted by the previous comment "If one cell is damaged, or its voltage falls below the voltage of the other cells, the other cells can discharge rapidly into it and cause a fire" is obviated.

P.S. the parts listed above have very cheap postage if you do not select express options. Where do you live? The South Pole?



 

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