I have updated the chart on the models to include the voltage<div>
</div><div><div style="font-family: Helvetica; font-size: 14px; ">20 4#  Model A-01 6V</div><div style="font-family: Helvetica; font-size: 14px; ">20 4# Model A-01 6V</div><div style="font-family: Helvetica; font-size: 14px; ">20 3# Model A-02 8.4V</div><div style="font-family: Helvetica; font-size: 14px; ">30 3# Model A-01 6V</div><div style="font-family: Helvetica; font-size: 14px; ">35-RA 6# Model A-02 8.4V</div><div style="font-family: Helvetica; font-size: 14px; ">55-RA 5# Model A-02 8.4V</div></div><div>
</div><div>I have been using 2S 8.4V Li-ion batteries without any regulators on the engines that can take 8.4v.</div>