Looking for an electronic speed controller (ESC) for your R/C car than can handle both 1-cell (1S) and 2-cell (2S) lithium polymer (lipo) batteries has proven to be a difficult landscape to navigate. Some of this has to do with what the market will bear. Typically if you’re running a 1/12 scale car, you’re only running 1S batteries. If you’re running a 1/10 scale car, it’s 2S.
The 1S need for me comes from the fact that here in Minnesota, the local track runs a variant of Vintage Trans-Am (VTA) that uses a 17.5 turn motor and single cell battery. It was a carry-over from 1/12 scale cars that ran on 4-cell NiCad or NiMH batteries. The idea was to keep the VTA cars relatively slow, and to keep the cost down.
As the Vintage Trans-Am rules evolved, the national standard moved to a 25.5 turn motor / 2S lipo standard, while the Minnesota locals stuck with 17.5T & 1S. I’d like to be able to run either/both, but more importantly, I’d like to be able to move into the USGT class once my driving has improved enough to warrant it – which uses 2S.
There are a few important aspects to supporting 1S batteries when it comes to ESCs:
- Input Voltage (from the battery)
- Output Voltage (to the receiver and servo)
- Low-voltage cut off
Some manufacturers, like Novak, have supported input voltages down to 3.0v since their inception:
All of our products, for over 33 years (!), servos, receivers, speed controls, have always been designed to operate on low voltage—4 NiMH or 1S. When Bob first started designing for R/C cars, 12th scale racing on 4 cell was really popular. So it was crucial that the electronics worked in those applications.
For a while now ESCs have been passing along a little juice from the battery to the power the receiver instead of having to rely on a separate battery pack to do so. This feature is called a BEC or Battery Eliminator Circuit. It makes things very simple and intuitive to hook up.
But receivers and servos typically want 6v instead of the 3.0-4.2v that a single lithium polymer cell will supply. Will your receiver and servo still work at this lower voltage? Possibly. Go ahead and try it. You may find a reduced range and slightly slower servo response, but you might not.
To overcome the desire for the receiver and servo operate at 6 volts, a voltage booster can be added between the ESC and receiver to get the voltage cranked up.
Low Voltage Cut-off
To protect lipo batteries from discharging too far, many ESCs have a low-voltage protection feature. to accommodate 1S, it must have a setting that goes low-enough for one cell, typically 3.0-3.3 volts.
I find the simplistic wiring a boon, so I was looking for an ESC that could support 1S & 2S input voltages with low voltage protection for both. Also, a built-in BEC with a voltage booster would keep things running smooth. Through my research I found the following models:
- Core RC Pace 45R – $67
- Core RC Pace 60R – $80
- Yeah Racing Hacktronic – $85 with programming box
- Graupner GM-Genius 120* – $130
- Airtronics Super Vortex Stock* – $130
- LRP Flow* – $170
- Airtronics Super Vortex Zero* – $185
- Speed Passion Reventon Pro Ex* – $200
- ORCA VX3 1S* – $220
* indicates ROAR approval. Sadly it seems like you have to pay to play in the ROAR domain. The Core RC Pace and Yeah Racing Hacktronic units are BRCA approved.
These following models are discontinued but seem to support both 1S & 2S but have been discontinued. You may be able to find one of these models used for a great price, especially the HobbyKing 1S (Gen1) which appears to be a re-branded Toro 1-cell – it sold for a mere $40 before it was discontinued.
- Toro One Cell
- TrackStar One Cell (Gen 1) 120A
- HOBBYWING XERUN-120A-1S
- Mamba Max Pro 1 Cell
- Reedy Blackbox 410R*
- Calandra Racing Concepts Advanced Black Diamond*
- KO Propo VFS-1*
- Almost all Novak ESCs*
Low Voltage Detection, but no Battery Eliminator Circuit
- Tekin RS GEN 2 SPEC* – $130
To fulfill my desire to get racing as cheaply as possible, I settled on a Toro 1-cell from rcmart.com. While it works good I first want to share my story about shipping…
Shipping from RCMart
Many RCMart items ship from Hong Kong, including SkyRC products such as the Toro 1-cell. I ordered mine on February 9th and was told to expect 7-30 days delivery time. You should consider 30 to be the more accurate number. When going to track the package, I saw this notice on the Hongkong Post website:
Also, somewhere in there was the Chinese (Lunar) New Year. Whatever the case was, I didn’t receive it until March 9th, 4 weeks later. It truly was on a slow boat from China.
I’m happy to say that I’ve done 4 races with this speedo, and it has been working great. I skipped the active cooling fan that was supplied and instead added some passive heat sinks. I’ve never had temps greater than 115°F after a 6 or 8 minute main, so I think I’m good to go!
If I’ve missed any 1S-2S capable ESCs, let me know in the comments and I’ll update this list.