Fast vs Safe Battery Charging

Exactly what the title says.
I read somewhere that the proper charging setting for the 7.2V 3000 mAH batteries in use for competitions is Fast mode and that the Safe mode is meant for the old 2000 mAH batteries. Is this true? Is it safe to charge the batteries on fast with regards to the effect, if any, it may have on capacity?

From what I recall, using the standard 7.2V 300 mAH batteries it is perfectly safe to charge on fast. The fact you may be remembering is that it is unsafe to charge the old 2000 mAH batteries on fast

My recommendation: have at least 3 3000mAh batteries and 1 charger to a team for competitions (as in, those 3 batteries and 1 charger are only for that specific single team, no sharing) and only charge on the Safe setting.

This allows you to use a Power Expander and still charge up enough throughout the day to successfully operate all but the most power-demanding robots. And you avoid the Fast setting that generates more heat and substantially decreases the batteries’ overall lifespan.

With that said, I would recommend instead having 4 batteries and 2 chargers to a team if budget allows. That way, 2 batteries are charging at any given time.

Summary and direct answer: the 3000 mAh batteries can charge on either Fast or Safe, but that doesn’t mean you should charge them on Fast. Long-term, the Fast setting will decrease batteries’ usable capacity substantially faster than the Safe setting.

Well with V5, maybe it will be ok for all teams to charge on safe, because we will just be getting rid of our old batteries anyway.

@Dokkaebi Thats an interesting thought, will V5 have totally different batteries? Is that confirmed or just speculation?

@Barin Thanks for your response! The reason I asked the question was because we were at a tournament the other day and had 6 batteries set to charge on safe mode. Our robot is fairly demanding with all 12 motors in use. Because of this we preferred to have fully charged batteries at the start of our matches, however, they were not charging quick enough. Could long term damage be avoided when fast charging by unplugging batteries as soon as the light turns green, or is the damage done throughout the charging process?

Yep. 14v batteries confirmed

If you start the day with mostly batteries that aren’t fully discharged (as in, most batteries were charged fairly recently and not drained since), you should have fully charged (or close enough*) batteries for pretty much every match. We have 3 teams and haven’t had any major issues with the 4-batteries-and-2-chargers-per-team approach.

*I forgot to mention previously that you won’t always get fully charged batteries with this approach. Use a voltmeter when applicable to choose the batteries with greatest charge for use in matches.

The damage is done during the charging. Unplugging after the light turns green won’t actually do much because the chargers are smart and stop charging thereafter anyway. If you do decide to fast-charge the batteries anyway, though, I would recommend ensuring good circulation of cool air between the batteries by way of (a) reasonable air gaps around all charging or still-warm-off-the-charger batteries and (b) one or two fans if possible.