Electric Vehicle Frequently Asked Questions

DC TO DC CONVERTERS

What is a DC to DC converter and why do I need one?

A DC to DC converter is the EV's electronic equivalent to the alternator on an ICE-powered car. While the motive power, heat, and probably AC for the EV are now powered by the high voltage battery pack, this pack is isolated from the rest of the car for safety reasons, and the rest of the car is still wired for 12 volts. Running things just off of the accessory 12V battery is possible, if you remember to charge it after every trip. However, a DC to DC converter adds a great measure of convenience and confidence, especially for long trips. It uses PWM to step the high voltage from the battery pack down to what an alternator would usually put out (13.5 to 14 Volts), to keep the accessory battery charged. There are even some EV'ers that do away with the accessory battery completely. This is possible if the converter is left on all the time, and provides the 12V to engage the main contactor when you turn the key.

What DC to DC converters are available?

This question has not yet been answered

Why can't I just tap the battery pack?

You can. However, the voltage will be a little lower than the 12V components are used to, so lights will be a little dimmer and wipers a little slower, etc. Also, this unbalances the battery pack. Unless you separately charge your batteries, or you have a battery balancing system like "Powercheq" modules or a Zivan "Smoother", you range will decrease to that of the battery you have tapped. Except for the separate chargers, these devices have low current capacities, so it will take a while for the pack to come back into balance. If you try to charge your batteries while the pack is unbalanced like this, the tapped batteries will be undercharged, while the others will be overcharged. This situation shortens the life of the battery pack. Either a separate 12V battery and/or a DC/DC converter will be much better for your battery pack.