leaving a battery on the floor
 

there is alot of truth to a battery going dead from being on the floor. I have been working in body shops for quite some time and have learned 2 important things about automotive style batteries. 1 is commonly known the cold and the second is leaving a battery on the ground not just cement. the battery looses power thru its plastic casing its not the positive charge that it looses its the negitive charge that is why the battery goes bad! I have seen many remidies for it such as cardboard under the batt and putting the batt on a shelf with rubber feet. my team keeps its batteries in a foam containers that one of my fellow team mates made during the 00 season because we had lost our battery the year before due to leaving it on the floor. I hope this helps you out.

Dr. Bot,
After going to the website you listed here is what I surmise. The statement that sulfation is the death of batteries is true. In most cases of liquid lead acid, the sulfate builds up as a normal byproduct of charge/discharge and falls to the bottom of the cells. When the buildup is sufficient enough to touch the bottom of the plates then they short out, killing the battery. The sulfation of the plates themselves is more due to the length of time a battery is charged and the current at which it is charged. By using "pulse" technology, the charge current is fed in high current pulses rather than in low constant current charging. All rapid charging devices use some form of pulse charging since it is able to achieve the electro-chemical reaction needed to charge and it is more easily controlled to prevent battery overheating. I think that their claim to be able to remove plate contamination might be possible if the charger were able to pulse a high current load on the battery between charge pulses thereby forcing the sulfates back into solution in the acid inside each cell.

The battery specs says it can be operated in any position - what about storage? Should it be alway upright? What about charging?
Upright? Not sure if a gel cell is different from an older style.

If you look close, you can operate the battery in any orientation but there is one position you should not charge it in as it blocks the breathers (over pressure valves)in the cells. As for storage, it just seems to make sense to store upright with all batteries facing the same way. This prevents shorting batteries together and/or causing high voltage source. Two batteries connected in parallel but opposite polarity are shorting each other. Batteries in series add so it is easy to get a 60 volt 17amphour battery. if the right terminals touch.
As to the story about batteries on concrete, I have not seen anything on this lately. I do remember reading about this occuring back in the old days when batteries were not made in a plastic case. Batteries were at one time constructed of a variety of insulating materials some of which were permeable to some extent. It would make sense that contaminants could enter the cells from the floor through this material and disrupt the acid solution rendering the battery dead. During the forties and fifties is was a common practice to rebuild you own car battery by opening the cells replacing the seperators and cell plates as needed. You would then replace the plates, seal the cell with parafin or asphalt and refill with fresh sulpheric acid.

O.K.

I am running an experiment - I am going to charge up two batteries and see if the self discharge rate is different on a concrete floor or a wood bench!

Can you e-mail your results, please?
Are you going to just measure terminal voltage or do you have a load tester?
Many Thanks

spare battery sources
 

Having expereinced a weak or damaged battery condition last season, I want to take along the 4 or more extras this season. I had planned to have four last year but somehow the extras got left behind in the packing:(

Battery sources conti.
 

Sorry must have hit a wrong key there:confused: I don't trust any of our old batteries and would like to purchase a set of four or more just for competition. Are local sources an option for batteries? Must it be the Yusika??? brand or can any exact amp*Hr rated battery be accepted? So can I pick up the spares at say Interstate battery shops or must I find a local dealer for the brand supplied in the kit?

You will need to buy the exact model that is provided in the kit by FIRST. You may want to wait until we have received the kit to make sure that we have the same model battery, so you dont waste the money on an illegal battery.



(Psst. There is an edit post button right under your post so that you dont have to make a new one. Or you could use the delete button:D )


Cory

I don't think there will be a change in the battery. It's tried and tested for our competition. The availability is very good from so many sources but as the season wears on the batteries may get hard to come by. This battery is very commonly used in emergency lighting and therefore is replaced on a regular basis by maintenance people all over the country. I know that the battery is available off the shelf from some battery stores, McMaster Carr, Newark, Allied and other electronic houses and industrial suppliers.

Battery chargers
 

I have used the 17Ah batteries in Battlebots and in my airplane. The ones that are supplied for FIRST do not have the high amp capacity like the Hawker Odessey PC680s, but they are the same technology and form factor. The PC680 will deliver enough current to crank my 200HP Lycoming over just fine. The inexpensive 17Ah batteries would melt themselves internally if you tried that.

One thing you don't want to do with these batteries is us a standard car type charger with them. They will continue to climb in voltage until they go into thermal runaway and bulge out. Been there, done that.

The charger I use now is a Deltran On Board Battery Tender 12V 6A unit. Deltran also makes a high frequency version that is capable of 20A. :yikes: A lot of the Battlebots teams use the 24V 20A chargers to recharge their batteries when the time was really short. I don't see any need for us to push the batteries like that. The Hawkers will take it, but I'm not sure the Yuasa (or whatever brand) batteries that FIRST supplies will take it.

I don't remember what the rules were on chargers last year. We brought previous year batteries along, but only as a backup. The older batteries tend to drop off capacity. So we would use the new batteries and recharge them between matches, and keep the previous years batteries ready to go just in case we failed a new battery.

Sources for batteries and chargers: For practice only, you can get these batteries from meci.com. $15.95 each, they are the same form factor. These are cheap, but they may have already dropped some capacity. We tried some of these before we bought Hawkers, and they were real pooches. But they may have been good enough for the FIRST robots. The last Hawkers I bought came from batterymart.com, also the Deltran chargers. There are links to the documentation there also (batterytender.com). Good info about what is going on for voltage rise and such.

A comment about the story of not storing batteries directly on concrete: The only thing that I ever saw that could make sense dealt with the temperature differential between the floor (and thus the internal bottom of the battery) and the air temperature. As the air temperature would cycle, you would have a temperature gradient between the top of the battery and the bottom. This could cause circulation inside the cells, and somehow accelerate the discharge of the battery.

Here is a link for a battery capacity testing rig http://aeroelectric.com/articles/battest.pdf.

Enough for now!

My team has def. done this, we call it the "High Octane" line, and it loks pretty cool. Never had a problem in using it for 3 years and def. charges faster than just one charger. Guess we are playing with fire.....

-Rc

Using two 4 amp chargers results in an 8 amp charge current

Thats a pretty high current, and it is not legal during competition. The rules regarding the battery are pretty strict, and they aren't arbitarry. Its best not to do. Besides, I'd say that in most cases, two mostly charged batterys are better then one quickly fully charged battery.

If you want to use it during the off season or for testing, thats just fine, but use caution.

The same rule about boiling pots fits here, a watched battery never finishes its charge cycle.

-Andy A.

Brian,
Don't do this!!!!!
Just because you haven't had a problem yet doesn't mean that it's not going to blow up in your face the next time. You have been extremely lucky! The specs published by the manufacturer comes from testing in environmental chambers where catastrophic failures can be correctly handled. They test to destruction to prevent your injury in actual usage.

Anyone notice that the list of kit parts says we get a 6 amp charger this year?