Batteries

What is the best kind of batteries to get? I'm just getting into robotics and plan on doing it for a long time (going to university for mechatronics) and was hoping to get some nice batteries to use. So... What size/type would be best? I heard Lithium ion is good, anything else?

I plan on mostly using it for smallish projects, most of them with Arduino most likely. What voltage do I need? 6? 9? 12?

Price is no problem as I plan on using them for a lonnnnng time. (but hopefully they're still reasonable, Im still on a student budget haha)

With robotics the battery time, size, voltage output, current output and all of that will very based on you project's needs and your budget. The different battery types have different characteristics. So it all comes down to the projects power requirements. How much voltage is needed to run it? How much current does it draw? How long do the batteries need to last? What conditions will they have to endure? Are there weight restrictions forcing you to use smaller batteries?

The arduino doesn't need allot of power. Anything between 7V and 12V is all thats needed. But the motors you use in the project will be what dictate the kind of power you need. You may find you will need to have a couple different types and sizes on hand.

The type and size of a battery ultimately depend on what the end application will be; you have to size your battery based on what it will be running.

Since all we know right now is that you are going to run an Arduino, we can take that as a starting point.

First off, the Arduino for simple development can be powered off the USB port, which is 5 VDC @ 500 mA. The Arduino itself can be powered externally by between 5-12 VDC, and I would stick to a source that can supply at least 500 mA (but you can probably go lower, it just won't run as long before the battery dies).

If you plan on driving servos or other higher-current needing devices (relays, motors, really anything beyond an Arduino and a few LEDs), you are going to want a larger source of current with a voltage size to match what you are driving, depending on what it is. Since we don't know any specifics, I won't give you anything here; depending on the end application, you could be looking at anything from a small LiPoly 3 VDC battery with a booster to 5 VDC, to a large glass-mat lead-acid monster pushing hundreds of amps at 12 VDC, or larger.

Something to keep in mind: If you are on a budget, and don't expect to be carrying your project around much, for an external power source, a 6 VDC pack composed of 4 "D" alkaline cells works wonderfully; you can push an amp or two with those, and it is cheap to buy anywhere. A quad AA pack works almost as well (or two such packs wired in parallel for double the current capability).

If you must use rechargeables, NiCad, NiMH, and SLA are the "safest" for hobbyists (easier to build chargers and such, but as with anything you should keep an eye on it while charging - also, SLAs shouldn't be charged in a sealed enclosure; despite their name, they do still give off small amounts of hydrogen while charging); LiION and LiPoly give you a lot of current (and sometimes voltage) for their size and weight, but if you fail to use the right charger, you can have a pretty amazing fire/explosion on your hands very quickly (watch some of the YouTube videos out there). They can be fairly safe with a well engineering charging system, but even there you can see failures (remember the cell phones and laptops that burned people?).

Hope this helps...

Good point. You need to be cautious when dealing with some of these newer tech batteries and how they charge. If you charge them the wrong way they can explode on you. Also if they are used in the wrong way, say your trying to pull more current from them then they can handle, they can explode. There are some very nasty chemicals used in theses newer batteries.

For small robotics, I suggest NiMh because they are almost as durable as NiCd, but higher capacity and lighter weight. For most purposes, a 4-pack of AA NiMh batts will serve you well. If you need more capacity, run multiple 4-packs in parallel. A NiMh AA can deliver several amps without any trouble.

Lithium (LiIon/LiPo) batteries are even lighter and higher capacity, but charging them is dangerous if you don't have a very well-made charger. They are also dangerous if you discharge them too quickly or physically damage one. AND lithium batteries must never be trickle-charged (once fully charged) or over charged, which makes them poor candidates for solar charging and that sort of thing.

Sealed lead acid batteries are great for heavy duty applications, such as motor power. They can deliver hundreds of amps if necessary. But they should be recharged right away for the best overall life. SLA batts are very heavy. They are almost always what you find in wheel chairs, PowerWheels, electric scooters and such.

And don't forget about super capacitors. They usually can be charged and discharged at hundreds of amps. The combination of a 10 farad or larger super cap and a DC-DC step-up regulator make for a great solar/thermal/piezo energy harvesting project.

Ok i'm mostly going to be making smaller projects for now, so I'll get a bunch of NiMh AA batteries. Are there special ones to get? Or just regular AA batteries.

And should i get as high amps as i can?

Regular AA from any store should be good. Name brands are generally better quality. You want the highest mAh rating you can find for the money. Never mix different mAh ratings or different brands within a 4-pack. And get yourself a good quality 4xAA charger.

I would get name brand myself; you might also see if there is a Batteries Plus near you, they might be able to make you some custom packs (may not be cheap, though). Stay away from Harbor Freight (or any other discount tool seller) rechargeables; I haven't had too much luck with them lasting.

I once actually had pretty good luck with some rechargeable alkalines (yes, they do exist) made by Eveready, IIRC. I don't know if they still sell them or not, but they are available.

Something else: At one time, it was possible to get SLA (sealed lead acid) in C and D cell form (a long time ago, All Electronics carried them surplus). I don't know if they are still made or sold, but that is another option.

Lastly, realize that NiCd and NiMh (and maybe LiIon and LiPoly, but don't quote me on it) only have 1.2 volts per cell, not 1.5; so four cells will give you 4.8 volts, not 6 volts - that may not run the Arduino on the external power connector (I think the onboard 5V regulator needs at least 6-8 volts to work?). A better bet would be to use 7.2V (6 cell) or 9.6V (8 cell) R/C car batteries; some can be "quick charged", and there are really good ones out there that can take a beating - check out your local R/C car hobby shop, let them know what you need/what you are doing, and they can easily hook you up (pick up some servos while you're there!)...

With 4 NiMh batteries, you can run directly to the 5V in pin. You don't use the regulator.

Pretty much everything there is to know about batteries can be found here. http://www.batteryuniversity.com/

I was looking around and I found some rechargable batteries. They are as follows:

4x AA Infinicell with 1.2V and 2600mAh

4x AAA infinicell with 1.2V and 850mAh

1x Energizer 9V that says 7.2V-150mAh.

Good? Bad? Ugly even? Or shall I get more of the same?

With what you have said I sounds like the AA's are good, just need more to get the required volts, would 6 work? And the 9V seems to have really small mAh... Is that normal or am i reading something wrong?

EDIT:: And they are all NiMh batteries.

EDIT AGAIN:: And this is the charger I have, not planning on making my own. http://www.robotshop.ca/energizer-universal-family-charger.html

Go LiPo! check out modern r/c car racing. I use 2s 5000mAh 30C LiPos now. 7.4V, 30 minutes chargetime, up to 150A discharge burst, weight ca 400 grams, infinite storagetime, costs 20 dollars. A nice charger costs 80. Use it within the specs and you are safe. Even NiMh explodes if you handle them to hard, I have tried!

If you are planning on running on the on-board regulator (say via the external voltage jack), then you are going to need at least 6 volts (you can go all the way up to 12 volts, IIRC); or 5 1.2 volt NiMH cells wired in series (here is where going with a standard R/C car 7.2 volt NiMH pack makes sense; tons of current available, and easily within the spec for the on-board regulator).

If you are going to bypass the regulator (as noted by koyaanisqatsi) by connecting to the 5V input pin on the Arduino board, then a 3 or 4 cell pack (3.6 or 4.8 volts, respectively) would work fine; just note that without a regulator, once the battery voltage drops below 3.6 volts, “strange things” will occur (everything from wrong readings on analog pins, spontaneous resets, to just turning off). Also if there are other loads connected to the battery, their power needs may cause the voltage to fluctuate to the Arduino, which could cause similar strange issues; the purpose of the regulator is to deliver the exact voltage needs, regardless of the level of the input voltage (within certain parameters, of course).

I am currently doing a project on a two wheel cart jus lik the segway. I am using the AXHD100k DC brushless motor from the oriental motors.The rated voltage required by the motor is 24V, i use 2 Np7 12V7AH batteries to power the motor, but unfortunately, the motor controller fused out when i connected the batteries in series to the controller. I dont know why it happened, because i believe the battery alone meets all the specifications of the motor.Is it because there was a large surge of current provided by the batteries to Motor. and also How much current can 7AH battery generate??.... Thank you, would appreciate if some one could help me out in this

You don’t need to cross post. Stick to the thread you already started.

How would a 6v 600 mA NiCd battery work for an arduino?
How would it work for driving 2 dc motors and 2 servos compared to 4 regular AA 1.5v batteries?
Just wondering.
I have been having decoupling issues with the dc motors and the servos, the servo moves erratically. (heh heh inside joke) ;D
Would it be practical to power the dc motors thru one power source (6v NiCd or 4 AA) and the servos thru the other power source, and which should be used for which?
(Sorry for the bazillion questions on someone else’s topic)

How would a 6v 600 mA NiCd battery work for an arduino?

The same as any other battery or battery pack connected to the Vin or power connector on the Arduino.

How would it work for driving 2 dc motors and 2 servos compared to 4 regular AA 1.5v batteries?

How do you have these connected to your Arduino? Are you using some sort of motor shield or controller?

Would it be practical to power the dc motors thru one power source (6v NiCd or 4 AA) and the servos thru the other power source, and which should be used for which?

I could be wrong but i think the only difference between that NiCd battery and the 4AA battery pack is one will last longer then another. I’m thinking the NiCd will be the one to last the longest. I’m also thinking the motors will drain a battery faster then the servos would. So its up to you which ones get which battery but i would defiantly give the motors and servos there one power source seperate from the Arduino. Just be sure to give everything a common ground.

Servos have their signal pins connected to arduino, and motors driven by an h bridge. Each motor draws less than one amp. Two separate power sources will solve noise from the dc motors, right?

Don't know for sure but i think you will need some filtering for that. Looking at the motor shield i have there are a couple of caps, 1 ceramic, 1 electrolytic, tied in with each H-bridge and the shift register on the board. It looks like the +5 from the arduino comes in threw the ceramic, to the electrolytic and then into the voltage in on each IC. On the optional external power source there is a larger electrolytic cap between it and the H-bidges on the board. I'm pretty certain these are for filtering any noise feedback to the arduino.

I tried some arrangements of capacittors , an I got the servo to generally be in the position I want. Maybe I'll try some other values and placements to improve it. Thanks for the advice

Lets see the ceramic caps are 0.1uF and the electros are 47uF/ 25V. The larger elecros are 100uF/ 6V.