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Hey Crew,

Hope all is Well. Was looking for a little insight on my Turbo Optima Mid Se. Just got it running again after, damn, gotta be 15 years or so. needed an ESD and Motor, picked up a NOS 240St and a used MC 112B. Worked out great, got it running with a little tweekin to the ESC.

I am using my original kyosho battery from 1988 (HA!). it is tapped up so i can't read the label but I believe it is a 7 cell, (8.4V ? ). I checked out the manual and it calls for a 6 cell (7.4) 1200 MAh niCd.
Have my old school trickel charger with option for 6 or 7 cell.

I want to pick up a new battery but not sure if i have to get a 6 (or 7) cell 1200. I seen some that are like 4200. Will this work with my the car. Any help on what kind of battery would be best would be appreciated.

(as a note, car seemed slower than i recall) can that be cause of the battery and/or the ESC setting. ESC setting seemed to go faster when i had no reverse set.

Thanks in advance.

Your old battery is probably the reason it's not performing well. If you're not making the move to LiPo battery technology yet, pick up any 8.4V 7-cell NiMH battery. The higher the mAh rating, the more run-time you'll have. Long gone are the days where you barely eked out 4 minutes on a 1200 mAh pack. I would get one over 4000 mAh, which should give you approximately 4 times the run-time as your old batteries did, when they were new.

LiPo battery chemistry is a huge improvement, but making the switch is a bit of a cost. LiPo batteries don't lose their charge just from sitting around, and can be stored for years with no change in output, if stored correctly. They also don't slow down as their capacity decreases, and don't have issues with charge/discharge "memory" like older batteries do. When you switch to LiPo, you'll need a new charger and a cut-off, which turns off the car when the battery reaches a certain minimum voltage-per-cell. LiPo batteries can cause a fire or explode if over-discharged. You don't run them until they're totally dead, as with NiCad/NiMH batteries.

A fully-charged 2-cell 7.4V LiPo outputs the same voltage as a 7-cell NiMH battery does, give or take; about 8.4V. The cut-off voltage would be something like 3.4V per cell, or 6.8V; so, when the battery reaches 6.8V, it's considered discharged.

Thanks for the info, very appreciated. Will my trickel charger work on a 8.4V 7-cell NiMH battery (15 minute charge)??

Lipo sounds like the way to go. I may end up modding it (brushless) eventually. If i put anything major into the car, i'll give Lipo real consideration. For now, just looking for low cost/high value option that will let me rip it around my yard again

The NIMH batteries take a different peak detection than nicads. If your charger is strictly trickle, and no peak detect, then just be careful, and check battery temps often during charge, untill you get a feel for how long it takes to charge.

If you end up having to buy a new charger,, then might as well consider lipo. The weight savings, and higher average volt during running will make an amazing difference in speed. Its almost more difficult and more expensive to keep running round cells, rather than switching to lipo. However for fun running, It dosent really matter. Optima mid can handle modern power. Especially if its got an upgraded center gear. You can push them pretty hard!

been checkin out Lipo the past few days. I may go that route considering the NiMH i saw was comparable in price anyway.
What discharge Rate (would a 35C be too much for a mid to handle?

omegaprime1 wrote:been checkin out Lipo the past few days. I may go that route considering the NiMH i saw was comparable in price anyway.
What discharge Rate (would a 35C be too much for a mid to handle?

Does not really work that way. The motor draws current from the battery. You can have too low C-rating but never too high. High C-rating just makes sure that the battery doesn't get stressed out.

I'll add a little clarity to the C rating thing and how it is applied if I can.

For example a 4000mAh battery discharging at 1C will take an hour to discharge. 60 / 1 = 60 minutes

The same battery discharging at 30C would take 2 minutes. 60 / 30 = 2. So 4000mAh (4 Ah) x 30(C) = 120 Amps current draw.

Now throwing in Voltage of say 7.4V average for a 2S Lipo you'd need a motor pulling 7.4(V) x 120(A) = 888 watts to actually get the full discharge of the battery's potential.
A higher C rating could potentially handle a larger motor. Say if the C rating were 35 then the watts could increase to 1036. Runtime would decrease to 1.7 minutes.

Most 540 motors are much less powerful than that. Say a decent brushed motor coming in near the 200w mark. That would equate to a 6.75 C discharge rate roughly.

So with our 4000mAh Lipo at a discharge rate of 6.75C we'd be pulling a constant 27 amps on the battery. In that case you'd want the C rating to exceed the potential
draw from the electronics. Don't forget to factor in the ESC if you have one as well as the receiver and servos if they are tied into the battery power as well. Plus there's
loss in the wires, but that's small.

Hope this helps.

Might have to modify things slightly to secure lipo pack in the SWB mid. I have a set of battery cups that are sanded flat to allow a fat lipo to fit in there. Somebody else did it, and its a solution to fit the lipo pack between the belt and top deck.

Boost,

That clarification was just a tad to technical for me, but damn thorough...thank you. I do have a futaba Mb112c ESC with a Lemans 240ST in it. Guess i'm just looking to have someone tell me a specific battery to use (say LiPo 5000MAH 25C or say ..NO, you need the 5000 MAH 35C. From what you are saying, i am thinking the 25 is fine, but i'm still not 100% sure.

I do have a setup in mind:
(Venom 25C 2S 5000mAh 7.4V Hard Case LiPo Battery with Universal Plug (EC3/Deans/Traxxas/Tamiya))
Tenergy TB6-B 50W Balancing Charger
Bluecell 1-8 Cell Lipo Digital Battery Voltage Checker with Warning Alarm + 2-6 cell Lipo Digital Battery Voltage Checker



Sal. any way you could post what you have rigged up , so i can get an idea what i will need to get.


Thanks again guys, very appreciated and informative

Whats a good charger for charging any kind of battery?

Wahrsuul wrote:Whats a good charger for charging any kind of battery?

I like the iMax B6AC, it'll do NiCad, NiMH, LiPo and other kinds of batteries. It has balance and storage modes, important for LiPo batteries. And it's affordably priced.

http://www.hobbyking.com/hobbyking/store/__58285__IMAX_B6AC_V2_Professional_Balance_Charger_Discharger.html

I run a Venom 15085, which is 20c / 4000 mah and I have run it with a lemans 240st. I am definitely no expert in lipo but the major draw for me for that specific model venom pack is it fits in optimas, mids, etc without modification as it is a stick pack with rounded profile, and no longer than the old 6 cell nicad packs. I have also run it on 17.5 brushless and it hauls ass. I suppose for racing you might want a higher c rating but I haven't seen that in a stick pack size.

Thanks for the info, i'll pick that one up. How much run time you get on that 4000?

I haven't timed it. Something usually breaks or comes lose on my optima runner before I use a whole pack. My scorpion on 17.5t brushless just keeps going. Just bashing around the park with my boys but seems longer than 15 minutes. Not all full speed. I also got a charging sack and an alarm - little thing that beeps if the voltage goes too low. I use it on the vintage esc since they don't cut off at low voltage. Not necessary for new escs.

Coelacanth wrote:

Wahrsuul wrote:Whats a good charger for charging any kind of battery?

I like the iMax B6AC, it'll do NiCad, NiMH, LiPo and other kinds of batteries. It has balance and storage modes, important for LiPo batteries. And it's affordably priced.

http://www.hobbyking.com/hobbyking/store/__58285__IMAX_B6AC_V2_Professional_Balance_Charger_Discharger.html

Thanks, that is a good prices. On Amazon I was seeing $90+ for some chargers.