Charging the 7.2 Volt Batteries

[BrianBSL]

I believe the standard IFI battery charger says 9.0V on the outside of it, as it likely uses that as the charging voltage. If the connectors match, then that's probably the charger you have.

[Alan Anderson]

The charger we received in the Kit of Parts is approximately half as wide as the OI power adapter, and has a connector matching the backup battery pack. It came in its own little white cardboard box. A red/green LED on it indicates that the battery is charging/charged.

I think the voltage listed on it was 8.something, which is perfectly appropriate for charging a 7.2 volt NiCd pack.

[Stu Bloom]

Historically there have been many matches lost due to a weak/drained 12v battery. I would not want to add ANY un-necessary load on my primary power source. It shouldn't be that difficult to design-in easy access for replacement of your 7.2v.

[Cory]

thread merged with other backup battery thread to reduce clutter.

[roboticsguy1988]

For one to stop backfeed just simply add another diode.

Two, why waste time taking the backup battery out and putting new ones in, and buying extra ones, when you can just put this little circuit together and it will keep it charged enough to do what is was ment to do. Which is provide power for a short amount of time like when a motor sraws to much current or something.

If you think about it the normal use of the servos and camera which draw there power off of i wouldn't really be coming from the battery anymore as much as it would the little charger.

The backup battery is a major part since the servo's and the camera depend on it. It also help the OI and radio modem, out in case there was a real small cutout in the power.

So in fact its not just for the purpose of not wanting to take it out and charge it. It's also for the fact that there will be times that it won't be fully charged and having the little charger on the robot will help in those situations.

Besdies, its a good learning experience for the students, isn't that what FIRST is about?

[royalfire]

Our charger (makubesu, I and our team) is as big as the IO converter and says 9.0 volts. Is this safe tpo charge a 7.2 volts battery with?

Cory, this is a different subject than this other thread you merged it with.

[BrianBSL]

Originally Posted by royalfire

Our charger (makubesu, I and our team) is as big as the IO converter and says 9.0 volts. Is this safe tpo charge a 7.2 volts battery with?

Cory, this is a different subject than this other thread you merged it with.

The 9V charger is the charger IFI has been shipping for years for the 7.2V batteries, so it's fine to charge them with it.

[Craig Roys]

Originally Posted by roboticsguy1988

Ok, everyone knows the common way fo charging the 7.2 Volt Backup Battery, taking it out and connecting it to the charger. Although while reading through the 2006 FIRST Encyclopedia (Rule Book) I noticed Rule R53 in Section 5 on page 16. It States:



Now where is this design? I spent about a half hour looking through IFI's website.

In case you haven't found it yet:

http://www.ifirobotics.com/docs/firs...up-charger.pdf

This is all they had posted - it's a link in the small print at the bottom of the ifirobotics home page.

Craig Roys

[Makubesu]

The 9V charger is the charger IFI has been shipping for years for the 7.2V batteries, so it's fine to charge them with it.

Thanks for your help, the 9v one worked perfectly.

[Al Skierkiewicz]

It is important to remember that when a robot is involved in pushing or is running with motors near stall, the main battery gets down to 7 volts or even lower. We have observed conditions on robots where they regularly drain the main battery down to 4 or 5 volts. It is for these reasons IFI began using the backup battery. Remember that the backup keeps the main proc alive and keeps the radio modems talking, no matter what voltage the main battery has fallen to. If you are on my alliance, I hope you are using a charged backup battery with no ties to the main battery and no attempt to compete with the bachup battery disabled.

[eugenebrooks]

Originally Posted by Mike Betts

A couple of references have been made to the "memory effect" of Ni-Cad batteries. I did a lot of research into this in the late 80's and can state that it simply does not exist.

Now before someone ups and quotes a university, technical or other "knowledgeable" source, I would ask you to read the sidebar article, Memory effect? No, voltage depression, in this article from EDN magazine. It does as good of a job of explaining the phenomenon in (almost) layman's terms.

The "memory effect" has been bantered about for so long (over 40 years) that it is accepted as fact by many very smart scientists and engineers. I had a devil of a time trying to explain this to my to management... But that's another story...

Regards,

Mike

Yes, Mike. It is more appropriately called voltage depression, but it is widely known as memory effect and the early quit of the equipment that sees the voltage drop is what matters. Putting those sleepy NiCds through a couple of cycles of a charger that conditions them through a proper discharge, watching the voltage, will usually get good performance out of a battery. Using such a charger, as opposed to a trickle charger, is a good idea to avoid these problems.

The notion that NiMh batteries dont suffer from these problems is also incorrect, on top of all of this. Their problems are not as severe, but NiMh also can get a bit sleepy after storage and a couple of cycles from a good conditioning charger will wake them up.

The Maha MH-C777PLUS charger, or its equivalent, will allow you to keep on top of this, and will tell you what your battery capacity is.

Please recycle batteries properly when they die...

At our first regional with a back up battery, I think two years ago, the tech inspector did not allow a larger radio shack battery and insisted on the IFI backup battery, in spite of the written rules. We compiled...

[devicenull]

If it's such a problem removing the battery from the robot.. charge it on the robot. I'm sure you can set up some sort of circuit/mechanical device that will disconnect the battery from the RC when you plug the charger into it. Then just mount a battery socket somewhere easily accessible on the robot, and when you get back to the pit, plug the charger into it.

Or, mount a robot battery with this circuit on your cart, and when you put the robot on your cart, plug the charger in. No drained battery during the match, but you also don't have to switch the battery out. Because it doesn't seem to be that much of a load.. you should be able to replace the cart battery once a day, and be fine.

It also seems to me that to use this circuit, you would have to have your robot powered on in the pits.. which doesn't exactly seem like a good idea. No one should be using radio's there, but what if someone has a misconfigured OI, and it manages to link up to your active robot? If you don't have the robot on in the pits, your battery gets charged for what? 3-6 minutes at the most (set up for match, match, clean up from match). And it would be a bad idea to have the robot on in the pits, because, at least from my experience, you are always working on the robot.

[roboticsguy1988]

Well i don't think its as much of the fact of a full recharge as make sure that the camera and the servo's and other stuff don't take most the batteries energy when ther may come a time where you need that extra boost.

Besides if it is charging all throughout a match wouldn't that mean a faster recharge in the pits?

Besides in a way this also would help (according to how you wired it) if like a team member forgot to put a new backup battery in there at least the servo's and the camera could run off of the circuit..... or purhaps it comes disconnected suring a game.

There are several advantages especial for a little circuit that take a VERY SMALL amount of weigth and space.

[DonRotolo]

Originally Posted by eugenebrooks

<snip>We compiled...

Spoken like a true software guy...

BTW, the best tool I have found for really testing the condition of your battery (main or backup) is this. I have one and it is very cool.

Don