My team had a concern regarding rule R13e. It states that the only legal means for charging a VEX 7.2V Battery Pack is via one of the following VEX Battery Chargers: Smart Charger, 276-1445; Smart Charger v2, 276-2519; 276-2221 (discontinued), 276-2235 (discontinued). All other chargers are strictly prohibited.
A few years back, we were in a competition where we were using the VEX chargers listed. Because of the fast paced scheduling of the qualifying rounds and the amount of loads we were placing on our batteries, we noticed that they were beginning to fade during each match. As a response, we began charging our batteries between each match. The problem with this is that the batteries were getting heated during the event, and as a result, they would not hold a full charge for the next event. The charging also contributed to maintaining the high battery temperatures that crippled our team’s battery capacity. After that event, my teams started using some digital peak chargers that allow us to specify the capacity of the batteries, the current (charge rate), and even battery chemistry. This enabled us to “top off” our batteries between rounds while maintaining lower battery temperatures, thus solving our problems of low power during the event.
The new rule that prohibits other chargers from being used only pushes teams into the paradox of charging batteries to maintain charge but at the same time keeping battery temperatures high thus lowering overall battery capacity and possibly shortening the overall battery life. I know NiMH batteries are fairly robust, but each time they are heavily fatigued, it shortens their battery life and lowers their capacity. I personally don’t like the idea of having to purchase new batteries because they were overcharged, overheated, or completely depleted to try and stay competitive.
If you have a laptop and you lose the power supply, you don’t throw away the laptop. A proper solution would be to find an adequate power supply with the correct specifications.
VEX allows teams to modify VEX parts but they don’t dictate HOW teams should modify them. My team cuts their metal components with a metal bandsaw while another team might use a Dremel tool…how is the process of charging your batteries any different provided it can be done safely?
I understand that VEX is concerned about safety and compatibility of batteries and their chargers, but I know that the “smart” chargers VEX offers are not as “intelligent” as the digital peak chargers available for a nominal price. If teams are capable of charging their batteries safely with “non-VEX” chargers, shouldn’t they be allowed to use whatever charger they want to use?
I don’t want my students to get disqualified for using our non-VEX chargers. I encourage you to re-word the rule to say something like “It is highly recommended that teams use the following chargers for charging a VEX 7.2V Battery Pack: Smart Charger, 276-1445; Smart Charger v2, 276-2519; 276-2221 (discontinued), 276-2235 (discontinued). Using other battery chargers may cause a fire or shorten the life of the VEX batteries if not used properly.”
P.S. - I gave my old VEX chargers to some new teams in our school district because they budgeted for extra batteries but didn’t purchase any extra chargers. We weren’t using them and I was soooo certain that VEX would never make a rule that governed the charging of the batteries…so now I don’t have ANY legal means to charge our batteries.
P.S.S. - Sorry for the long thread