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-   -   Batteries? send help! (https://www.rctech.net/forum/radio-electronics/1118334-batteries-send-help.html)

DirkW 11-24-2023 03:04 AM

2-3C was also my personal maximum. Now pretty much all tracks and racing series here have adopted 12A/20A max. charging/discharging rules. On the one hand that fits nicely for most people running shorty packs (them being in the 4000-6000 mAh range, resulting in 2-3C) while on the other hand for people using the bigger stick packs around 8000mAh, it's only 1.5C, but still ok with me. The 20A part however, I don't really get. I mean according to Hobbywing's spec sheets that's only half of what their G3 17.5T motor was able to pull. Half. Of a stock motor. Mod motors go into triple digits (their 5.0T motor is given as pulling 118A - and nobody is afraid of someone's Lipo being driven in Mod with such currents. But let's say a 40A discharge bank, that pulls a mere third of that is apparently to scarily dangerous to be legal anymore. I built mine myself, so it was only a couple of Euros in material and not much work at all, so it doesn't bother me, except I don't understand the reasoning behind it. But for people who bought these things ready made and who paid a whole lot more, this must suck...

staiguy 11-24-2023 10:36 AM


Originally Posted by Roelof (Post 16052642)
…The 1C is just a safe rating but does not mean 2 or 3C can not be done but 10C ????? Nope, not my idea to try it.

I don’t know what voodoo protek does but almost all their batteries say 10c is safe. I don’t even have that much power in my power supply. I follow my r1 battery recommendation of 3c right before a race.


https://cimg9.ibsrv.net/gimg/www.rct...8cdc27132.jpeg



gigaplex 11-24-2023 02:35 PM


Originally Posted by DirkW (Post 16052648)
2-3C was also my personal maximum. Now pretty much all tracks and racing series here have adopted 12A/20A max. charging/discharging rules. On the one hand that fits nicely for most people running shorty packs (them being in the 4000-6000 mAh range, resulting in 2-3C) while on the other hand for people using the bigger stick packs around 8000mAh, it's only 1.5C, but still ok with me. The 20A part however, I don't really get. I mean according to Hobbywing's spec sheets that's only half of what their G3 17.5T motor was able to pull. Half. Of a stock motor. Mod motors go into triple digits (their 5.0T motor is given as pulling 118A - and nobody is afraid of someone's Lipo being driven in Mod with such currents. But let's say a 40A discharge bank, that pulls a mere third of that is apparently to scarily dangerous to be legal anymore. I built mine myself, so it was only a couple of Euros in material and not much work at all, so it doesn't bother me, except I don't understand the reasoning behind it. But for people who bought these things ready made and who paid a whole lot more, this must suck...

That's a burst current. You'd want a sustained discharge current to be comparable to the average draw, not peak draw. If a mod motor was continuously drawing 118A then there's no way it would make a 5 minute run on a shorty.

gigaplex 11-24-2023 02:37 PM


Originally Posted by staiguy (Post 16052737)
I don’t know what voodoo protek does but almost all their batteries say 10c is safe. I don’t even have that much power in my power supply. I follow my r1 battery recommendation of 3c right before a race.


https://cimg9.ibsrv.net/gimg/www.rct...8cdc27132.jpeg

They don't do anything special. They just tell you that it can handle charge rates that will speed up degradation and require you to buy more packs more often. They don't warranty a battery for high charge rates. As long as it doesn't spontaneously explode, they're not liable.

DirkW 11-24-2023 03:01 PM


Originally Posted by gigaplex (Post 16052788)
That's a burst current. You'd want a sustained discharge current to be comparable to the average draw, not peak draw. If a mod motor was continuously drawing 118A then there's no way it would make a 5 minute run on a shorty.

Ok, let's go for an average draw then. Let's just assume they use up 3000-4000mAh in those 5 min. That would equal an average draw of 36-48A (if my math doesn't fail me here). So, actually around the same as with a resistor bank. So a 40A discharge (not talking about 40A charging here!) should still be perfectly safe, just as I don't consider running Mod class to be dangerous. Seems a bit randomly chosen...

gigaplex 11-25-2023 03:02 AM


Originally Posted by DirkW (Post 16052801)
Ok, let's go for an average draw then. Let's just assume they use up 3000-4000mAh in those 5 min. That would equal an average draw of 36-48A (if my math doesn't fail me here). So, actually around the same as with a resistor bank. So a 40A discharge (not talking about 40A charging here!) should still be perfectly safe, just as I don't consider running Mod class to be dangerous. Seems a bit randomly chosen...

Not many chargers can do more than 20A without an external discharge bank, so maybe they picked it based off that? Our rules locally don't specify a discharge rate, they just ban external dischargers. Setting an explicit discharge current doesn't give as big of an advantage to those who have the select few chargers that have a higher rate.

DirkW 11-25-2023 05:45 AM

I dare say most chargers out of the box won't do even 10A, let alone 20A (even my trusty iCharger 406 Duo can only do 10A without external discharge bank - or maybe when used from a car battery, but I've never used it without a PSU). But is that really a good reason to outright ban anything outright? Maybe in a racing series, but on tracks, even for open practice? Doesn't convince me. Someone had an unnecessary idea and the horde blindly followed - at least that's my theory. You yourself have seen the myths spread by people who don't really understand electronics...:nod:

Goof 11-25-2023 06:52 AM

It's more because it's 7.6 and it's Been through, more approvals.
Maybe better materials. HK though has good stuff. I've never had an issue with any of their stuff. I do know the battery you're talking about. But not the 7.6 battery. I have 2 of them that I use for my starter boxes. There are 4s though they work well and they're fairly old and they're still are going


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