Sand Scorcher electrics help

[tim04 45]

Hi there

I was visiting Tokyo last week and picked up a re-released Sand Scorcher with a Futaba 3PV model set and a Tamiya Lithium Ion battery x2 (6.6v 1100 - the one shown on the box). I really enjoyed building it, and having worked in model shop when I was young it really took me back!

The problem is I assumed the Futaba speed controller MC331CR would cut off the battery when it dropped (it did but below the threshold for the li-ion battery), so the battery is now faulty. I have another one but I assume I will either A) have to change the speed controller to one which is compatible with Li-ion, or buy a Ni-MH hump pack for it?

Any advice would be gratefully received.

 

Thanks

 

Tim

[Shodog 1835]

Or you can stop running it when it gets low

[Juggular 4964]

First of all, welcome to Tamiya Club.  

Tamiya does not sell LiPo (Lithium-Polymer).  I think Tamiya decided that what they sell to children should not catch fire (I applaud their corporate ethics that resulted in millions of dollars less in profit but more in respect).  What you bought is LiFe (Lithium-Iron).  It has a lower voltage, but safer because it does not catch fire.  LiFe's cut off voltage is lower than LiPo, if I remember correctly.  But a complete drain could ruin both just the same.  

1)  You could get a voltage alarm.  Those things are cheap (less than $5).  Just plug it to a balance lead, it will sound an alarm at a set voltage.  You don't necessarily have to get another ESC, if the alarm warns you to stop.  

https://hobbyking.com/en_us/hobbykingtm-lipo-voltage-checker-2s-8s.html?countrycode=US&gclid=CjwKCAiApJnRBRBlEiwAPTgmxB_VuSKFtgeya0PU8rtqBsL20mqbSL9ivCu6RRBNmoFPqUnSPdvw-RoCRAoQAvD_BwE&gclsrc=aw.ds

2)  Investing in a LiPo is not a bad idea.  I don't know what you use for a charger, but if it charges LiFe, it may charge LiPo (but please don't assume: make sure).  

"Shorty" LiPo packs like below may fit. 

https://hobbyking.com/en_us/turnigy-nano-tech-shorty-4200mah-2s2p-65-130c-hardcase-lipo-pack-roar-approved.html

Shorties are... well, short.  It's less than 4 inches in length, about 2 inches in width.  But check the size before you buy one.  LiPo costs about half the price of LiFe.  It gives you more voltage (7.4v = faster speed) and quadruples the runtime.  You may have to solder the connector, though.   

But not everything in LiPo land is a lollypop.  LiPo is a fire hazard --- get a fireproof charger/storage bag (also less than $5).  And with or without adding LiPo to your hobby, every kitchen should have a fire extinguisher, imo.  

https://hobbyking.com/en_us/fire-retardant-lipo-battery-bag-171x60x65mm.html

3) As you've mentioned, you could get an ESC that has a pre-set cut-off voltage.  ESCs don't care if the juice comes from LiPo, LiFe, NiMh, NiCd, Alkaline or button batteries for grandma's hearing aids.  Electrons are electrons.  Just that some have cut-off voltages.  Since ESCs are cheap, you could get one, if you don't want to connect the voltage alarm everytime you run it.  

(btw, I'm not associated with hobbyking. I buy my stuff from ebay or Amazon, but it was just easier to get photos from hobbyking--I don't think they'd mind if they can sell more)  

Anyway, Good luck.