Plug Bug: Auxillary 12 v Battery

Electric Bug

A typical gas powered car has a large 12 volt battery mainly for the purpose of turning the engine over during starting. That usually takes a lot of amps to crank it over. Since my electric car won’t have that problem, I figure I can go with a significantly smaller battery. I heard people can get away with really small batteries, since the DC-DC converter will be doing most of the power providing, and the aux battery just provides some startup power to turn on the contactors and even out the draw for other accessories.

I went with a Powersonic PS-12180NB – 12 Volt/18 Amp Hour Sealed Lead Acid Battery. I’m hoping 18 Ah will be enough. I’ll find out! It was only $35 on amazon, plus shipping. It turned out to be cheaper than buying it locally at Batteries Plus.

Here it is mounted in the car. I fabricated a little hold down strap out of some thin steel and bolted it down. It is solid!


You can also see some silver sound dampening material applied to the car. It is just some roofing sealant stuff, and apparently it helps quite down the ride quite a bit.


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Mike wilson

Very impressed with your work, great job. I have a question – I’m also converting a bug (’72 convertible) and now starting to look at the electrical. Is it necessary to continue the connection from the regulator to the battery? Seems to me it only benefited the generator. If not needed then I will option to put my aux battery in the front trunk. thanks, mike


hey mike, thanks!

I actually removed the regulator; I know it is still in the above pictures. The problem I had is that I wanted to run voltage to the rear section and run it off the DC-DC converter, and have that also charge the 12v battery. I don’t think the regulator is needed, since the DC-DC converter should be fairly regular (I hope!).


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