Arlo Battery Needs & Battery Question

popnbrown

Quick background (just 2 lines...i promise): I've done robotics through FRC (http://www.usfirst.org) but for the most part electronics is generally set. Specifically when it comes to batteries and total power consumption of the robot. (2 lines...I DID IT)

I was wondering what power consumption for the Arlo system is like, specifically the Wheel/Motor Kit (http://www.parallax.com/product/28963). .It's listed as 2.5-8Amp, but wondering what kind of current usage is typical for flat/carpetted surface?

I'm debating whether I need to go above 16Ah for it to be used for 4 or 5 hrs. Thoughts?


My second Battery Question is in regards to general theory on how long batteries last? What is the optimal draw on a battery? What happens if there is a greater draw on battery, how does that affect how long it would last?

Hal Albach

The answer is really dependent on several factors. One way would be to actually measure the current drawn while the Arlo is running it's intended application over the actual surface that it will encounter. With all sensors a-sensing, blinky lights a-blinking, and death rays a-firing while rolling across the carpet, read the current draw on a DVM placed in series with the battery on a suitable Amp setting. As for batteries with the longest run time I would suggest Lipo, they have very high energy densities. Check out the offerings at Hobby King, I'm sure you will find what you need.

Matt Gilliland

HI popnbrown - Welcome to the Forums :thumb:

Standby current of a Fully loaded Arlo as shown in this video is about 400ma or so,depending on lights, which controller board you're using, how many sensors are activated, etc.

This is a pretty simple current draw test...but it should give you a ball-park estimate on how much power the robot consumes.

[video=youtube_share;VuKEAeZdfo4]

The SLA batteries are rated at 12v 8Ah.

-MattG

Ken Gracey

Matt Gilliland wrote: »

HI popnbrown - Welcome to the Forums :thumb:

-MattG

Oh my, you have attracted the attention of the Lead Acid Queen Bee! He knows batteries and Arlos better than anybody.

The Arlos I run for trade show events use two 12V 7 Ahr batteries in parallel. They run all day, fully loaded with ten ultrasonic sensors, LED tape, and electronic doggie collar guts to stay inside of the buried wire fence zone. I build these up as current pigs, so they're probably pulling an amp @12V at any given time, maybe double that when the little kids hang on to them and get dragged around to clean the floor.

Ken Gracey

popnbrown

Thanks for the replies all.

For reference for others:
I found this awesome post that detailed the entire build - http://forums.parallax.com/content.php/111-Building-Arlo and going off there I investigated the batteries he was using. So I just googled for the PS-1290 and the specs sheet (http://www.atbatt.com/power-sonic-ps-1290-12v-9ah-sealed-lead-acid-battery.asp) answered my second question of how discharge rate changes, the answer to which is depends on the battery and manufacturers spec that out.

So back to my first question, which is really, how much power does the Arlo draw, looks like MattG totally hit it on the nail. So while running the draw from both motors + control system is hitting at about 1.5A, pushing 2A...interesting.I'm now wondering if the 2.5A-8A range was for both sets or for each. I've been calculating using that as the draw for each motor.

You mentioned it wasn't going at full speed, how fast relative to full speed was it going in the video?

Yet another question, I've got a warning to be careful about batteries in parallel. Any thoughts on that? I'm going to buy two brand new ones so I'm not terribly afraid but wondering if I should be more cautious/concerned.

ChrisL8

Hi popnbrown, I see you already found my post, so I think everything I could tell you is there. I can only say that with the motors, a prop board, some LED light strips and a USB relay board connected I have never paid the slightest attention to the power draw. The thing just goes and goes. The laptop I have on board dies after five or six hours at the most (it runs off of its own batteries), so the SLA batteries that run everything else are never the issue for me.

My understanding of SLA (Sealed Lead Acid) batteries in parallel is that they are a lot more easy going than Lithium type batteries. When I first got mine I charged each one to full charge with my charger, then I hooked them up to the power supply in parallel and they are always drained and charged in parallel. My understanding is that as long as the load and charge are both always parallel that it is fine.

P.S. Here are my notes from before I started building. I have intended to make a "parts list" post someday, but I haven't gotten around to it yet. Remember I made these notes BEFORE I built the robot, so I was researching.

"Battery:http://www.parallax.com/product/28960 says that the base includes "a battery shelf designed to carry one or two 12 VDC, 8 amp hour, SLA batteries"
"SLA" = Sealed Lead Acid
These are the kind of batteries used in UPSs, battery powered string trimmers and such.


This thread talks a lot about the issue: http://forums.parallax.com/showthread.php/153150-Arlo-Batteries-and-Charging?highlight=arlo+battery


Looks like use 1 or 2 PS-1270's or 1280's or 1290's for more capacity. The PS-1270 was the original "design" though I don't see that listed anywhere other than in this thread.
The thread also indicates you can use and drain two of them in parallel. The only concern is having one "hot" and one lower, but if you always run them together that shouldn't happen. Remember, depending on how you wire you double voltage or amps, we want more maps, not more volts.


The number tells the story:
1270 = 12v 7 Amp Hour
1280 = 12v 8 Amp Hour
1290 = 12v 9 Amp Hour


The PS-1290's are $24 each on Amazon. Cheaper for packs of 2.
The PS-1270's are $18 each. I really just need to compare the size, and weight.
The 1270 WILL fit in the included holder, so if the others are the same dimensions I'm good. Weight is a matter of the robot's payload and my ability to carry it.


Here is size and charging info on the 1270 & 1290, they are the same size/weight and they seem to charge just like any 12v SLA battery:
http://www.batteryconcepts.net/yuasa/sla-7-12.html
http://www.batteryconcepts.net/yuasa/ub1290.html


These are "AGM" batteries, so I think anything that will charge an AGM 12v battery is fine."

jeevan

Hi all,

• I would like to know if we can replace the 2x 7Ah Power sonic SLA batteries that came with the Arlo with 2x 10Ah LiFePO4 batteries, and if yes, would that have any negative effects on the system ?
• Also, if we were to hear creaking noises from the system, where would you believe the sound to be coming from – the motor, the wheels, etc. , and causes? Does exerting a lot of weight upon the Arlo cause any such effects ? These sounds are akin to loud creaking sounds.
• What is the maximum load that the robot can carry, and does that weight include or exclude the weight of the robot itself.
• I have seen people mentioning that the robot lasts a whole day with a few sensors and the Motor running - i assume this is without any additional weight beyond this. Does anyone have a number on it, and the extent to which it gets affected with additional weight placed on it.

Thank You!