Still flying Nitro? Time to Re-build your starter

Extreme Makeover of the Dynatron starter

We have this starter for about 8+ years, it is a great product and the motor is running very strong. Originally converted it to NiCd cordless (15.6V) system but during years of usage, the NiCd have passed their life span and no longer take/hold charge well. Starting helicopter has becoming more and more a frustration process. Emmm… Time for a new design.

Here is the current setup.

  • Sullivan Dynatron S603 Super Power Starter
  • Custom plexiglass bracket battery holder
  • Multiple no-name NiCd batteries are from the nineties ( 2 x 7.2 in parallel) + (2 x 8.4 in parallel) in serial

If you need to view larger photos, go to our Flickr page.

Worth mentioning was the plexiglass mount , loved the design and fabrication. The K&S rubber battery holder mount underneath it securely. Anyhow, it is now retired. Did I mention there were a couple of times the switch blade arc welded itself together?

Here are the new requirements

  • Replace the starter rubber strip with a push button momentary switch
  • Reduce weight and rid of those old, heavy NiCd battery packs
  • Power the starter with higher current (> 12V) and eliminate the arc weld situation
  • Don’t mind the weight as long as it is not on the starter itself
  • Easy to charge and maintain battery system
  • Provides a 12V circuit to power panel

Research Time

Always a reliable work horse, we decided to switch the primary power back to lead acid. These batteries are widely available; Many float chargers on the market specially designed to provide TLC of these batteries; They are forgiving and allow you to set, charge and forget during off season.

The new starting system is powered by two flooded wet-cell lead-acid batteries. A combination of 12 and 6 volts, they are not maintenance free and require regular top up charge.

AhChanging AmpCharging TimeElectrolyte VolumeSpecific Gravity of electrolyte
Energizer (Distributed by Johnson Controls Battery Group Inc.)12N9-4B-11290.915 ~ 20 Hours0.6 Liter1.260 ~ 1.280
Yuasa6YB8L-B680.815 ~ 20 Hours0.3 Liter1.280

Power Relays

Power relays are widely used in all high current starting applications, most common are in automobiles. Turning your car key activates the power relay which starts the engine of your car. There are many different designs of power relay available, handling a wild spectrum of voltage and current. Here is a link to describe some terms used to describe relays, in layman’s language and a FAQ on relays, How they work and how to wire it up.

  • A single-pole single-throw (SPST) relay
  • Omron Electronics Inc.
  • Panasonic Electrics Works
  • Tyco Electronics

New schematics

Switching from NiCd to lead acid with different voltage and requirements will need a new power schematic. (Diagram coming soon)

Building the new battery tray

Building the battery tray is easy. First add the bottom rubber mounts at four corners. The MDF board is a side panel from an old stereo system, the board is strong enough to hold two lead acid batteries while small enough to have everything sitting on top. Just put a couple of “L-brackets” to hold everything in place.

The main circuit (aka the batteries are) wired together in serial (thus 18V) and terminated to a Anderson Multipole Connector (SB 2 pole connector – 50 amps).

Mentioned previously, we need a separate circuit to drive the power relay. The 2nd circuit which is also 18V circuit (2 x 9V batteries located inside the candy box) are wired to the relay and goes to RCA female jack. This circuit will become active when the momentary switch is engaged.

Stripping the Sullivan Dynatron

While removing the original rubber & contact blade off of the Sullivan Dynatron, we found a perfect location to install the replacement switch. This metal replacement switch is made by Gardner Bender and is a SPST momentary switch.

After trimming some material off the plastic starter end cover, we installed and wired up the switch. Now the starter has a pig tail (Power cord terminated to Anderson Multipole Connector (SB 2 pole connector – 50 amps) and momentary switch is wired to a RCA female jack.

While you have the starter opened up, mind as well check starter and brush condition.

A corded starter system

The main power cord is 4 feet in length, it is made up of 12 gauge electrical wires braided together a signal cable. The electrical wires are terminated to Anderson Multipole Connectors (SB 2 pole connector – 50 amps) at both ends. The signal cable is a video RCA cable (Yellow RCA jacks).


We have this setup running for the entire summer and very pleased with the result. Lead acid certainly required less maintenance than NiCd, giving ample of power to start all types of nitro engines. Although the starter switched from a cordless back to a corded setup, the unit itself is much lighter and we love the momentary push button.

At the time of writing, the RC world is switching from Nitro to Electric. Some of us still enjoy the fumes of burning Nitro and Nitro engine tuning, a good starting system is a must! We hope you enjoy this article and have fun flying.

Team BTF.

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