[slijin]

Originally Posted by Tristan Lall

(Are you sure that NS18-12 is even a valid part number?)

Originally Posted by Al Skierkiewicz

Quick correction, last years rules specified the NP18-12 which is also an AGM design.

Typo on my behalf, I was referring to the NP18-12. Sorry!

Originally Posted by Al Skierkiewicz

The charger shown above can be used but I would not recommend (nor was it legal in 2012) to charge at 8 amps.

We won't be getting the BatteryMINDER, but if we had my intent had been to run it at 4A, not 8A. I understand and see the reasoning behind your perspective that 6A is a purely nominal maximum setting, but I still can't help but be mildly uncomfortable charging batteries rated for max charge currents of 5.1A and 4.3A at "6A" (let alone 8A!)

Originally Posted by Joe Ross

The problem with charging batteries in parallel from a single output is that each battery is in slightly different condition and state of charge. They try to work around this by giving the following conditions in the manual. I don't trust that you could ever guarantee this, so I don't think it's safe.

Additionally, notice that this is only to maintain the batteries, once they are fully charged. It won't charge 6 batteries.

Originally Posted by Al Skierkiewicz

Do not try to charge batteries in parallel please. I asked this question of MK and The Battery Association of America (I think that was the name) and both responded that the only way that was acceptable was if the batteries were all purchased at the same time, had been charged the same and had the same loads applied over their lifetime. And then it may work or it may damage all of the batteries. In other words if the batteries were assembled into a larger array and only used that way could other methods of charge and discharge be used. These batteries are not like the large arrays used on electric subs or in large UPSs where the acid is checked regularly and specific gravity is monitored cell by cell.

I thought as much - I was rather skeptical of the method when I noticed it, because I just couldn't see charging them in parallel as a safe method, given that batteries often tend to differ from unit to unit. Thanks for confirming.

Originally Posted by Michael Hill

Another related question...how many years do other teams use the same battery? It seems like after just a couple years of competitions, we've got some batteries that are bad. It can't help charging at such a high charge current during the days of competition (we have maybe 8 batteries total on our team?)

We buy a new batch of batteries every year, since most of our robots tend to err towards ridiculous power consumption. Our competition batteries tend to consist of mostly ones we buy that year, supplemented by ones from the previous two years that have good max charge records (we made a simple battery tester in-house that displays the battery voltage measured across a small load on an LCD screen; a "good" max charge record, with reference to our usage, tends to mean that it consistently charges up to 12.5V or higher).

Originally Posted by alb4h

How many batteries do your teams take to competition?
Ann

We bring 8 with us. During qualification matches, we'll often have as many as 3 at full charge (the rest are either charging, in the robot for practice/testing/matches, or being used for auxiliary 120VAC through an inverter), but we make sure every battery is fully charged (or as many as possible) going into elims, because of the rapid turnaround time between matches.

Thanks to everyone for the outpour of feedback

I'm still curious if anyone has found success with alternatives to the Schumacher and Dual Pro. Speaking of which, it seems that Dual Pro makes an IS3 along the RS3, but I can't seem to identify a difference between the two...