Maintain your batteries over the summer break

[DeMentor]

This year we had a lot of trouble with batteries from previous projects -- especially the 2009 ones. Three of the 4 batteries from 2009 were bad by the time we got to robot testing for this year's project, and additional batteries from previous years were also failing. We were not alone in this experience -- scanning the forums I find many other comments about poor experiences with some sets of batteries. This is getting to be a costly problem as I believe we need 4-6 batteries to be fully prepared for the championship rounds in the regionals, and veteran teams are now getting only 1 new battery in the Kit of Parts.
Therefore, we plan to spend more time on battery maintenance during the off-season, and you should do this too. This includes keeping all of our good batteries on float charge during the summer break. A float charger can be left on a battery forever with no risk of overcharging. A trickle charger (which is different than a float charger) can be used periodically, say 1 day a week -- but needs to be disconnected most of the time to avoid overcharging (which also shortens battery life). The "2A" setting on the chargers most of us use is sufficient for trickle charging -- but again, be careful not to leave batteries connected to a 2A charge all summer.
I've found float chargers listed online for as little as $10/each, and some float chargers claim they can be used for batteries connected in parallel as long as those batteries are of similar condition (I interpret that to mean the same battery manufacturer and model, and able to hold a charge).
There's a relatively new battery charging technology called "desulphation" that is claimed to be capable of recovering some of the lost battery storage capacity. I plan to test it against both good and bad batteries over the summer and will report results in a future posting.

Have a great summer break!
Mike

[Wayne Doenges]

Hey Mike

Have you ever tried a charger called "The BatteryTender"?
It will charge your batteries, to full charge, and than go to trickle charge. If the bateries fall below a set threshhold, the charger will go to full charge until the battery is fully charged and then go back to trickle.
I've been using the BT for ten years on my motorcycle battery when I store the bike during the winter. Haven't had a battery go bad yet.

[Vikesrock]

Information about the charger FIRST has provided in the last few KOPs seems to suggest that it does float charge on at least the 4A and 6A settings and perhaps the 2A setting as well.

[Alan Anderson]

Originally Posted by Vikesrock

Information about the charger FIRST has provided in the last few KOPs seems to suggest that it does float charge on at least the 4A and 6A settings and perhaps the 2A setting as well.

The Shumacher SC-600A manual says explicitly that the charger goes into "maintenance mode" once the battery reaches a fully charged state. It shuts off the current, then periodically checks the voltage and starts another charge cycle when the voltage has dropped below "full".

[Al Skierkiewicz]

Originally Posted by DeMentor

and some float chargers claim they can be used for batteries connected in parallel as long as those batteries are of similar condition (I interpret that to mean the same battery manufacturer and model, and able to hold a charge).
Mike

Mike,
That means same model, same purchase date, same charge/discharge life.

[DeMentor]

Originally Posted by Al Skierkiewicz

Mike,
That means same model, same purchase date, same charge/discharge life.

Al: thanks for your comment and agreed. I was trying to simplify the guidance thinking that most teams would be dealing with 2010 batteries now. The best approach is to use one charger per battery because that eliminates mix-and-match confusion and risk.

[DeMentor]

Originally Posted by Alan Anderson

The Shumacher SC-600A manual says explicitly that the charger goes into "maintenance mode" once the battery reaches a fully charged state. It shuts off the current, then periodically checks the voltage and starts another charge cycle when the voltage has dropped below "full".

Alan: good info (I couldn't locate our SC-600A manual...). This feature appears to make the SC-600A charger safe for long-term connection to a battery. I saw another comment online that perhaps the SC-600A also has desulphation capability -- does the manual say anything about that?

[DeMentor]

[quote=Wayne Doenges;963997]Hey Mike

Have you ever tried a charger called "The BatteryTender"?
It will charge your batteries, to full charge, and than go to trickle charge.QUOTE]
Wayne: thanks and that's a good example of a float charger. There are many different models available, some of which are now less expensive than the BatteryTender. As the additional comments above indicate, some of the chargers teams already have are probably good enough for long-term connection and maintenance of batteries.
On that topic, I did further investigation on the Midtronics CXC-2005 chargers that were in FIRST KOP's until at least 2006. According to the documentation, these chargers simply turn off once the full charge is reached -- so they won't perform long-term charge maintenance (i.e., a float charge) of the connected battery and won't help the problem. I plan to do a full test of chargers, charging and discharge rates, desulphation, etc. over the summer and provide a full update in a later post.

[rtfgnow]

Mike do you think the float charge will solve all your problems? I doubt that was the main reason you had problems. Some common problems that get mentioned are:

-Storing batteries uncharged
-Storing batteries on their side
-Constant charge/discharge cycles (overuse)
-pulling on the leads or carrying them by the wires
-keeping them in adverse conditions (extreme hot or cold)

While there are reasons to keep a float charge on your batteries, it may be like giving your son a flu shot when he has the measles.

[Alan Anderson]

Originally Posted by DeMentor

I saw another comment online that perhaps the SC-600A also has desulphation capability -- does the manual say anything about that?

All it says about sulfated batteries is that they might fail to charge properly.

[DonRotolo]

There are two "kinds" of lead sulphate, which I have come to call "soft crystal" and "Hard crystal". Soft crystal can be worn away by a certain charging pattern, and this is what I feel these "desulphators" can attack. Hard crystals cannot be broken down, and thus are permanent.

Over time, my theory is that the soft turns to hard as the crystal structure has time to stabilize. Think of the atoms lining up a little bit better.

This may be a lot of hooey, but with 20+ years in the lead-acid battery world, this is what I have observed. The above are opinions, not necessarily facts.

By the way, it is a fact that lead-acid batteries' failure mechanism is through sulphation. Lead oxide (the battery plates are coated with a paste of this), as the battery is discharged, turns into lead sulphate, drawing the sulphur from the sulphuric acid electrolyte (and freeing electrons in the process). Recharging pulls the sulphur atoms from the lead and puts them back into the electrolyte.

Or, said another way: Leaving your lead-acid battery discharged for any time at all leads to permanent, irreversible damage. Keep a lead-acid battery at 100% charge and it will last decades. A reasonable time between charge cycles is 2-3 months.