Battery and Charger for 12V Motor and Wheel kit

Whit

Hey Everyone,

I've been researching SLA Batteries and chargers to use for a Robot with the new 12v Motor and Wheel kit.

It is easy to see the weight to Amp-hr relationship. So I will let the cost/weight/Amp-hr help me choose.··Maybe something like this one, which is 12 amp-hr and ten pounds approx·- http://www.batterymart.com/p-12v-12ah-sealed-lead-acid-battery.html·- too much?

I found this charger which is kind of expensive, but sounds like it has some nice features. http://www.batterymart.com/p-acc-1206s.html·It says that it· will "Blast battery destroying sulfation off your battery plates for longer battery life."

What do you guys think? How do I estimate the recharging time?
·

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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

Post Edited (Whit) : 5/13/2008 12:48:19 AM GMT

Dgswaner

Whit, I purchased a Battery about that same size as the one shown, it looks a little big for 12ah but it is about 1/3 the price I paid.

also for a charger, it's not just charge time but it's amperage also. I have a 25AH 12 battery and I forget the formula they used (10% perhaps) but I was told to charge it at about 2amp, a higher amperage charge will still charge it but you run a higher risk of over heating the battery and ruining it. I bought a cheap O charger from Harbor freight with an analog amp meter and it's easy to tell when it's done charging. I plan on making a self charger with auto shut off at some point.

one thing I wish I would have done differently was to go with a higher voltage, if you went with a 14V battery(s) then regulate the power down to 12V this will make it so you motors won't start slowing down when your battery is not at 100% low, or it at least give you longer before it shows.

I didn't catch this the first time.... from your charger link
"Recommended for maintaining EnerSys ODYSSEY and Optima batteries only. Not recommended for charging EnerSys Odyssey or Optima batteries."

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

Post Edited (Dgswaner) : 5/13/2008 7:18:32 PM GMT

Tom C

Dgswaner,

It also says: "Defender charger will charge any type or brand of lead acid battery fully, sealed or dry battery. The charger will adjust itself as the battery gets old."

I assume that this means that it will charge most Sonic and Panasonic SLAs.

Just a thought.

Regards,
TCIII

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If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!

Beau Schwabe

It sounds like the Lead-Acid charging formula that it's using assumes full current (36 Watts.. or 3 Amps) until the battery voltage reaches 2.4V per cell (or 14.4V) ...When the battery reaches this voltage it drops to a lower voltage 2.25V per cell (or 13.5) and lower current to serve as a float charger to keep the battery topped off.

It says... "DC Output: 12 Volt 3 Amps" ... but if it's expected to charge Lead Acid batteries, then the output voltage needs to be higher than that.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 5/14/2008 4:37:00 AM GMT

Whit

Beau,

Does Parallax have any intention of offering a battery and charger that they recommend to use with the 12 volt motors and wheels?

TCIII said he thought Chris used a 12 volt, 7.5 amp-hr battery on the prototype. Do you know what they used?



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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

Ken Gracey

Hey Whit,

We probably won't offer any batteries since we'd only be adding cost for no real purpose.

We used 12V 7.5 amp-hour batteries with much success - about 2 hours' worth in fact. For the charger, we simply use benchtop power supplies. I highly recommend batteries from http://www.power-sonic.com/. I used many different brands in my testing for the hybrid robot and with the motor mounts and I found these to be well-documented, consistently manufactured and fair-priced. They're all sealed, too. Don't use any of the motorcycle or personal watercraft batteries where you add the sulfuric acid. I've had real issues with these on a robot. A bad robot crash can cause them to open up and spill acid all over the place, causing shorts (and smoke) along with other permanent problems.

Yesterday when I was driving back from San Francisco I nearly stopped at a well-known hardwoods store in Berkeley (McBeath's) to pick up some nice plywood for my motor mount base. Unfortunately, I knew that I wouldn't have much time to do this project so I drove on by the shop and didn't stop. . . sad day!

I'm going to build a robot from these too, and I can't wait to get started.

Ken Gracey
Parallax, Inc.

Whit

Ken Gracey (Parallax) said...

Yesterday when I was driving back from San Francisco I nearly stopped at a well-known hardwoods store in Berkeley (McBeath's) to pick up some nice plywood for my motor mount base. Unfortunately, I knew that I wouldn't have much time to do this project so I drove on by the shop and didn't stop. . . sad day!

Ken,

Thanks for the info on the battery. I'll check out the site.

I know McBeath's. I went to seminary in Berkeley. You'll get it going soon I'm sure!

Ken Gracey also said...


They're all sealed, too. Don't use any of the motorcycle or personal watercraft batteries where you add the sulfuric acid. I've had real issues with these on a robot. A bad robot crash can cause them to open up and spill acid all over the place, causing shorts (and smoke) along with other permanent problems.

Yea. I remember the fire on your desk story.

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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

Post Edited (Whit) : 5/15/2008 11:43:06 AM GMT

erco

Whit: I'd be very interested to hear your opinion of the "sulphate-blasting" charger after you get one. My experience with old SLA batteries in my old robots (Cye, Hero, Hero Jr, and Hero 2000, I have 'em all) is when they're gone, there's little that can be done to revive them.

Actually, even modern-day Roomba Ni-MH batteries take a dive after a year, even under careful use. Affordable long-term, deep-cycle battery technology for cars and robots still has a long way to go. But at $4 a gallon for gas, I'm sure there are many geniuses hard at work on the problem.

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·"If you build it, they will come."

Whit

erco said...


·Affordable long-term, deep-cycle battery technology for cars and robots still has a long way to go. But at $4 a gallon for gas, I'm sure there are many geniuses hard at work on the problem.

Isn't that the truth!

I have noticed the same thing about the battery technology. My dad and I have a lot of battery powered tools. The batteries are always the weak link. The best system we've experienced for rechargers are the type that drain the battery first, then start the recharge process. I think the particular ones we have that work that way·are are NiMH batteries.

I don't know if the same sort of thing applies to the SLA batteries. This will be a new experience for me. I've kind of decided it's just like everything. You have to dive in and just experience it for yourself. It is nice to shortcut some dumb mistakes though!

Hey Ken - the technical info on the Power-Sonic site is fantastic.




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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

GICU812

You dont want to drain a SLA battery before charging, same with Nicad, they do not respond well to deep cycling. You might get 500 full cycles from a nicad at %100 discharge, but 10,000 if you dont discharge it lower than %20. I just pulled those numbers out of my butt, but the real ones are simular.

erco

That sounds about right·for SLA batteries. They're not high tech and sexy,·just cheap and time-proven, properly used. My battery vendor in China just alerted me that SLA battery prices have plummeted in the last month (April 2008), along with the price of Chinese lead. After all the bad press about lead in Chinese products last year, even they can't give it away! But it's nice that some form of energy may be getting cheaper.

I live near Toyota's corporate·HQ near Los Angeles and I'm utterly fixated on the number of Priuses on the road here. It seems like 10% of the cars here are Priuses. It is wonderful to see how successful this venture has been. Everyone wants one. Everything about the car is unconventional. The internal combustion engine operates off the Atkinson cycle, not the Otto cycle. Nice CVT with regenerative braking. Interesting article at·http://en.wikipedia.org/wiki/Toyota_Prius

The Ni-MH battery usage is reliable and well-documented. http://www.cleangreencar.co.nz/page/prius-battery-pack· and http://john1701a.com/prius/prius-misconceptions.htm·.

Enough Prius praise. Power management in our robots is usually much simpler, thankfully. The battery manufacturers keep increasing the capacity of consumer-grade AA cells, I have seen them up to 2800 mAh and probably very soon up to 3000. Personally, I'm still a fan of SLA's for my robots for two reasons: bang for the buck, and I·need·the weight for traction. I'm working on a special new consumer bot that I think will be quite popular with the boys. Details later, but my prototype is doing amazing things using a BS2.

As Whit so elequently noted, just having a battery in a household tool (or robot) that is charged enough to use is a considerable challenge for most of us! Any level of power monitoring and self-recharging in a robot is a big step in the right direction. You may have picked that up from several of my posts, including my self-charging Scribbler robot. I wrote an article on that for Robot magazine, but it got bumped to the next issue. I do hope to see it in print...

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·"If you build it, they will come."

Beau Schwabe

GICU812,

"You dont want to drain a SLA battery before charging" .... Agreed!!

I have a 10Amp Solar Charger design that I have been using over the last year, and the "magic" numbers that I have found for keeping the
Lead Acid battery (<-Standard 630 Cranking Amp Car Battery) healthy seem to be from 2.4-2.5 Volts per cell for charging... (<- Personally
I stay on the lower side of that) .... 2.2-2.3 Volts per cell for float charging....And you never want the battery voltage to fall below 1.8 to 1.9
Volts per cell.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

kelvin james

Regarding the topic of restoring rechargable batteries. I saw this article a while back, and thought some may find it interesting.


www.rexresearch.com/bedini/bedini.htm#6545

Whit

erco and Beau,

I can't wait to see you Scribbler recharging station erco. The video was impressive.

So if you recharge the SLA before they drain, do you monitor the batteries in some way or just learn how to tell by observation?

kelvin, Thanks for the link.

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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

Beau Schwabe

Whit,

I monitor the battery as I'm charging.... The Solar is capable of providing 135 Watts, or just over 11 Amps. So, to a car battery this is fine at this charging rate.... I Charge the battery at maximum current (<- sunshine dependant) until the voltage across the battery reaches 14.5Volts (approx. 2.4V per cell), at that point I regulate the voltage to 13.5V (2.25V per cell) and limit the current to 1 Amp. I continue to monitor the voltage and if it falls below 11.5V (approx. 1.9V per cell), Power to the Inverter is switched OFF, and the output is sourced from the Mains instead. Here is where the "cycle" starts over again, and the battery is allowed to charge at the full 11 Amps. The Inverter is only allowed to come back on-line when the battery has reached 12.5V (approx. 2.1V per cell)

...One of these days I'll post a schematic, since the brains behind the Charge Controller uses a Basic Stamp II.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

sam_sam_sam

Beau Schwabe


One of these days I'll post a schematic, since the brains behind the Charge Controller uses a Basic Stamp II.


When you have time to post this·I would like to see this project to get some····s

I have two 45 watt solar panels and would like a way to control them

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··Thanks for any··that you may have and all of your time finding them

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Sam

erco

For my small robots that use 6V & 12 V SLA batteries and auto-docking, I've had very good results with these inexpensive "smart" chargers that charge at a set rate then switch to a maintenance charge indefinitely.

12V 1 A: http://www.batterymart.com/p-12v-1a-sealed-lead-acid-battery-charger.html
6V 500 mA: http://www.batterymart.com/p-6v-500ma-sealed-lead-acid-battery-charger-2.html

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·"If you build it, they will come."

Whit

Thanks erco! I had looked at that charger the other day. Glad to know that it works well.

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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

Beau Schwabe

Whit and Sam,

Charger Schematic posted:
http://forums.parallax.com/showthread.php?p=727110

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Whit

Thanks Beau!

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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

RobotWorkshop

erco said...
Whit: I'd be very interested to hear your opinion of the "sulphate-blasting" charger after you get one. My experience with old SLA batteries in my old robots (Cye, Hero, Hero Jr, and Hero 2000, I have 'em all) is when they're gone, there's little that can be done to revive them.

I too have doubts about the ability to "bring back" an old SLA battery with the "sulphate-blasting" charger. I suppose that in theory it might help if there is a tiny bit of build-up but I would like to see some test results that actually back up that claim.

Many of the SLA batteries I've replaced seem to have just dried up which I doubt any charger will ever help.. Some of the worst ones make noise if you shake them.

The SLA battery does work very well in the robots and when well cared for can last several years. About what the UPS manufactures seem to get when they are used in UPS devices. After that they may still work for a while but your capacity will continue to drop after that as the internal resistance of the battery increases. When it drops too much it needs to be replaced....

After years of working on all the old robots (HERO 1, HERO Jr, HERO 2000, Androbot TOPO's, RB5X, Gemini, Newton, Hubot, Omnibots, etc) one of the first things that needs to be replaced is the battery. They've usually been sitting for years and that is one thing that kills an SLA. Let it sit without a charge and it will be nothing more than a paperweight after a couple years.

A lot of people have charged up an old battery and after charging may THINK it is fine since they read something over 12v on a 12V battery. A voltage reading alone like this is just about worthless! The only way to get an idea on the battery health is to put the voltmeter across the battery and then watch it when you attach a load. A good battery will drop only a little and then more at a slow rate (according to the load) but a bad battery may drop to half or less!!

On many robots what happens is that it may power up on a questionable battery but when certain parts activate (sonar, drive motor) the voltage drops low enough under high load to cause erratic operation or reset the CPU. If people see that happen I always have them check the battery first before trying to troubleshoot a problem that doesn't exist in their robot.

Overcharging can kill the battery too. I've seen some where the case has expanded (sometimes enough to crack it) which makes them difficult to remove.

Best practice with the SLA's are to not deeply discharge them, charge them after each use to top them off, and don't overcharge them. If you follow that they work very well.

Best Regards,

Robert

erco

This is developing into an interesting thread, and I must admit to chuckling that all the robotics technology, computer chips, IR/ultrasonic sensors, software algorithms, hi-fi, wi-fi, bluetooth &·blackfin·don't do·squat·after the battery dies suddenly & unexpectedly. Same basic problem for the last·hundred years!·In 2008, shouldn't·our problems be too many flying cars in the skies and/or robots taking over the world?

Marine deep-cycle lead-acid batteries·should last longer than·gel cells or SLAs in robotic applications.·I found an informative site at http://www.marine-electronics.net/techarticle/battery_faq/b_faq.htm· All sorts of great data on charging and discharging, but what caught my eye is this authoritative but·disappointing statement:

"A good quality deep cycle lead acid battery will cost between $50 and $200 and, if properly maintained, will give you at least 150 deep discharge cycles."

That's not a lot of cycles, IMHO. Less than half a year of daily deep discharge cycles? Otherwise, carry a much bigger battery than you need and barely discharge it. ·Hope that new A123 battery pans out. Quick. http://www.autobloggreen.com/tag/a123

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·"If you build it, they will come."

Tom C

Hi all,

For those of you who like to roll your own like I do, here are several links to 12 vdc SLA battery charger circuits:

http://www.uoguelph.ca/~antoon/circ/labc3.html

http://www.rason.org/Projects/gelcell/gelcell.htm

http://www.vt52.com/diy/myprojects/other/charger/charger.htm

Regards,
TCIII

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If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!

Whit

Hey Everyone,

I know that SLA are used in Uninterupted Power Supplies (UPSes). What kind of circuitry is used in a UPS? The battery is only occasionally used. I did have a UPS finally go bad a while back, but I just bought another. I removed the battery from the old one and recycled it, but unfortunatly, I threw the rest of it away. I wasn't really up to fooling with something I didn't really understand (especially when there was the chance of a higher voltage).

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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

Beau Schwabe

The SLA's in a UPS must be float charged to keep them from self discharging.· The algorithm used for charging can vary, but typically adheres to something like this...

http://www.batteryuniversity.com/partone-13.htm

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

StampNut2

Yeah, I agree with all of the above info, I have had two SLA batteries go dead because I have left them to discharge for to long, and they are not that old. I think I will stick to Nimh, !2000ma cells for my Motor unit project.

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Never give up when things go wrong, Just work them out.

robosapienv2-4mem8.page.tl/

Whit

Thanks for the info Beau.

StampNut2 - please tell me more - What are you thinking? Do you plan a recharging station?

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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

Tom C

Stampnut\Whit+,

Given the load carrying capability of the Motor Controller & Wheel kit it makes sense to use a very large capacity SLA battery, say, around 10 amp-hr or greater. I do not believe that you can approach the capacity of an SLA battery with NiMH batteries for an equivalent price.

I have built custom 3800 ma-hr and 4500 ma-hr NiMH batteries for my bigger rovers just to get reasonable run times. I don not believe that a 2000 ma-hr battery will give you much run time.

Also, if you select the right charging circuit, the charger will go into a float mode that will maintain the charge on the battery if it is not presently being used.

I plan to build a docking station similar to the Heathkit Hero 2000 robot\iRobot Creat docking stations to allow the robot to recharge the SLA battery without human intevention.

Just a thought.

Regards,

TCIII

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If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!

StampNut2

Tom C: A slight correction to your statement, "I don not believe that a 2000 ma-hr battery will give you much run time". I did state 12000ma !2 amps, not 2 amps, and as you state 2 amps would be usless. This may not be the right approach to this motor system, but At 12 amps it has a reasonable power system depending on load of course, as this motor system is capable of some serious payloads the right batteries need to be implemented for the right conditions. And SLA is a good choice. I just happen to have enough of those 12000, NIMH bateries to form a 12v system. Worth trying for a lighter payload. Your average Gel cell is 12v @7ah

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Never give up when things go wrong, Just work them out.

robosapienv2-4mem8.page.tl/

Post Edited (StampNut2) : 5/27/2008 6:40:28 PM GMT

Tom C

StampNut2,

If you look at your post of 5/27, you will notice that you are typing a ! for a 1 so that 12000ma looks like !2000ma and can be easily mistaken for 2000ma.

Just a thought.

Regards,
TCIII

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If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!

StampNut2

Tom C: Thanks for spotting the typo, did not see that.

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Never give up when things go wrong, Just work them out.

robosapienv2-4mem8.page.tl/