Battery upside-down [Archive]

Squillo

08-02-2012, 21:56

There is no rule specifically prohibiting mounting the battery upside down. We have had our battery upside down for several hours without any sign of leakage. It is called a 'non-spillable' battery. It would be helpful if we could mount it this way on the robot.

Do you think the inspectors would ding this as "unsafe"? Or for any other reason?

dez250

08-02-2012, 22:19

I suggest you take a look at this thread (http://www.chiefdelphi.com/forums/showthread.php?t=99944) from earlier in the season, a lot of useful information including an answer to your question is in there.

MrForbes

08-02-2012, 22:20

I would not do it just because it will be cumbersome to remove and install it between matches for charging. There's a "handle" on top of the battery, so you can grip it easily, how will that work if it's upside down?

I guess I'm getting old, I have no sense of humor about battery position and mounting...I like them to be secure, easy to access, easy to connect/disconnect, etc.

Kevin Sevcik

08-02-2012, 22:22

You can mount the battery on your robot in whatever orientation you like, it won't create any hazards when discharging out of position.

You DO need to charge the batteries only in the upright position. When over charged they can generate gases that need to be vented, which happens best when upright.

Ether

08-02-2012, 22:28

Tristan Lall

09-02-2012, 02:11

I think it's AGM, but does anyone know for sure what technology is used in this year's battery? On the only datasheet I've been able to find, it doesn't say.

http://www.batteryplex.com/sheets/NP18-12R.pdf

They are AGM. (See especially pg. 4 of the second link.)

http://www.enersysreservepower.com/documents/US-NP-RS-006_0611.pdf
http://www.enersysreservepower.com/documents/US-NP-AM-003_0111.pdf

Ether

09-02-2012, 02:42

They are AGM. (See especially pg. 4 of the second link.)

http://www.enersysreservepower.com/documents/US-NP-RS-006_0611.pdf
http://www.enersysreservepower.com/documents/US-NP-AM-003_0111.pdf

also on Page 4:
Not recommended for use in inverted “vents down” position

FrankJ

09-02-2012, 10:33

I not sure what upside down buys you. It is the same dimension right side up :)
You also want to install it so that you are not stressing the cable lugs by forces on the battery cables.

Kevin Sevcik

09-02-2012, 10:56

also on Page 4:
Not recommended for use in inverted “vents down” position

Vent position only matters when you're charging, though. At high overcharging currents, electrolysis produces oxygen and hydrogen which can build pressure and requires venting. There's no gas production or need for venting at any other time. Those datasheet are just assuming you're using them in a standard application, where a battery is semi-permanently installed and is discharged and charged in place. As long as he isn't charging his battery on the robot, he'll be fine.

Ether

09-02-2012, 11:12

Vent position only matters when you're charging, though. At high overcharging currents, electrolysis produces oxygen and hydrogen which can build pressure and requires venting. There's no gas production or need for venting at any other time. Those datasheet are just assuming you're using them in a standard application, where a battery is semi-permanently installed and is discharged and charged in place. As long as he isn't charging his battery on the robot, he'll be fine.

I can't argue with you on theoretical grounds, and my guess is you're right about the datasheet assumption.

Nonetheless, I'd follow the manufacturer's recommendation. There might be other reasons for it. To pick one example: Does the vent ever operate during large swings in battery temperature and barometric pressure? (and could that ever cause some sort of acid leakage?) Can any battery gurus comment on this (or other reasons)?

Al Skierkiewicz

09-02-2012, 12:06

In most cases, dangerous gasses are mostly generated during charging. Although normal use (discharge at 1/10-1/2 C) shouldn't produce increased pressure within any cell, our use can cause some additional heat to be generated. While acid leakage is not a huge concern, these batteries do tend to produce some internal condensation. If the battery is used upside down, and the internal pressure were to cause a vent to open, some of this condensation would be lost. Over time, this will reduce the available current from a given cell.
My usual recommendation is never charge upside down and don't use upside down if at all possible. When the battery is inverted, you can see where the terminals are located in relation to the robot structure or other electrical connections. This is a possibility for battery failure either through shorting to structure or damage to the terminals on the battery.
One must remember that this battery is manufactured such that a variety of terminations can be used with the same basic battery configuration. The terminals on our battery simply push over two round terminals inside the battery and then are soldered in place. It is possible to break the solder bond internally without any visible external damage. The result is significant voltage drop and heat. The battery may test good with a voltmeter, it may even charge normally but will fail either intermittently or through voltage drop on the field.
Finally, I have to remind all teams that securing the battery is part of the inspection checklist. You have to demonstrate this during inspection. If you are on the field and the battery drops out of your robot, you will be disabled for the remainder of the match.

Ether

09-02-2012, 12:23

While acid leakage is not a huge concern, these batteries do tend to produce some internal condensation. If the battery is used upside down, and the internal pressure were to cause a vent to open, some of this condensation would be lost. Over time, this will reduce the available current from a given cell.

My concern was more centered around safety than reducing available current over time. Student gets trace acid on hands; rubs eyes; medical emergency.

Squillo

09-02-2012, 15:29

Thank you all very much for your thoughts and info. Sorry I didn't think to search first - it never crossed my mind that anyone other than my nutso electronics team would have come up with such a crazy idea.

nitneylion452

09-02-2012, 15:41