How to install a battery box in your bass guitar

BBG Tech Max

Best Bass Gear tech Max is back with another video guide. This time he takes us through the steps to installing an 18-volt battery box.


What you'll need


  • Battery Box Routing Template


  • Router and router bits
  • Vinyl transfer tape
  • Double-sided tape
  • Drill with depth-stop
  • Hand screw driver
  • Old bar of soap

Planning Battery Box Placement

Step one: Planning out battery box placement

When contemplating placement, you have a few different choices. For this particular install we are going to install it in the center of the bass.

The first thing we want to do is clean off the bass. We use naptha which should remove any waxes or polishes that may have been used on the bass. This with make sure the double sided tape on our routing template does not come loose during routing.

Now we take a piece of vinyl transfer tape. You can pick some up from a vinyl sign professional in your area.

The transfer tape allows us to draw our layout on the instrument with pencil, which makes installation easier. It also means we don’t have to adhere our tape directly to the finish of the bass. That may work fine on a thick poly-finish, but it is a nice precaution to take if you have a delicate finish that may be damaged by pulling away tape.

Since we are installing it in the center, start off with an approximate center line. This bass doesn’t have anything straight on its back, so we just eye ball it to give us something that looks right to work with.

In placing it I want to stay away from the area of the bridge and the pickups. After measuring we can see that our route needs to be about four and three-eighths inches from the butt of the guitar.

We make a mark at that point and use a protractor to draw a perpendicular line.

Placing the battery box routing template

Step two: Placing your routing template

Now we take out the template. Best Bass Gear sells templates made from clear acrylic which allows you to see your lines and to place it exactly where you want it.

Take your time placing it exactly where you are going to want the battery box.

Now break out that double-sided tape. We are going to be nice generous with this because we want to make sure our template stays in place. We put a strip on each side of the template to make sure it’s well adhered.

We place it on where we want it, using our lines as guide, and press down firmly to make sure it stays in place.

Routing the battery box

Step three: Routing the battery box cavity

We’re going to use a router with the standard bearing top router bit that luthiers usually use. You can find them for sale at lutheir supply stores.

This particular is one will make a quarter inch depth cut. It’s a good one to start with because it doesn’t need a lot of the bit buried into the wood in order for the bearing edge to read on the template.

If you have another template cut out of the same material, it’s nice to hold against the base of the router when you are adjusting the table on the router so you can see how deep the bit will be.

Now so that we aren’t just trying to drop the router into the bass, we first drill a couple relief holes to get us started. When you drop in the bit for the router, slowly work clockwise around, enlarging the hole until eventually it reaches the edges of the template.

You are going to want each cut to take out another quarter of an inch. Anything more than that is too much work for the cutter and will cause things to heat up too much.

There is quite a bit of depth to these battery boxes so we’ve still got a while to go. Just take it one cut at a time.

Now the bit that we are using has a half inch radius, which just doesn’t get into the corners very tightly. To get a better fit we are going to use a 3/8” to get into those corners.

And now we repeat the same thing from the first cut, adjusting it so the cutter is just coming through the surface. Now I have slightly square corners and I’m going to change over to my next bit.

This is the bit that should take it to full depth. It’s the same type of bit, a 3/8” radius, but it is extra-long.

After the cut we see we are still not quite at full depth. It’s good to check in-between cuts, holding the battery box up against the depth of the bit, keeping the height of the template in mind.

You want to slightly err on the side of being too deep, because you can’t have the battery box sticking out from the surface of the bass. If anything you want 9it just a little – and I mean just a little – deeper than the battery box.

After the last cut we measure everything to double check the fit. When you happy with it you can take off the template and peel off the vinyl transfer tape that was protecting the bass.

Drilling hole to connect battery box to control cavity

Step four: Drilling your connecting hole

Now we need to drill the connecting hole between the battery box and the control compartment.

Get the controls out of the way so they don’t get damaged by the incoming drill bit. Remove the pickguard and pull out the controls. We remove the battery, since we won’t need that anyways.

Now this is a tricky part. It’s a pretty long drill, and it’s got to be at a really flat angle. Rather than come in straight to get all the way over the control cavity we’re going to angle it over to make a little shorter drill.

Start in spot that’s advantageous to the wires that need to exit the box. And start high up on the wall so when I come out in the cavity I don’t run the risk of coming out the front of the instrument.

The two sets of red and black wires coming from the battery holders on the 18v are not designated, so before we run them through our hole into the control cavity we’ll mark one set which a paint pen.

Mounting the battery box

Step five: Mounting the battery box

You should now be able to nestle the box nicely into your newly routed hole.

That’s all set, but now before we flip the bass over, lets mount the battery box by drilling holes and screwing it in. It’s good to use a depth stop drill to ensure that you do not drill deeper than necessary.

As we have before, we are going to rub a touch of soap onto the threads of our screws before we screw them into the new holes.

Now we are ready to flip it over and start wiring.

Wiring your 18-volt power supply

Step six: Wiring your 18-volt power supply

We are going to take our unmarked black wire and our marked red wire and solder them together to create a series link between the batteries, and create our 18-volt power supply. We slip on a piece of heat shrink tubing onto the wire before we start. After giving a moment for the solder to cool, we slide the tubing down over the connection. Using either a heat gun or your soldering iron heat the tubing to protect the connection.

Then we go over to the jack and disconnect the black wire from the previous battery connection. Here is where you solder the marked black wire. Once again using heat shrink tubing to protect the connection.

That takes care of the neutral connection form the battery to the jack, that’s how the preamp gets turned on and off as you insert the plug into the jack to play the bass. It grounds the battery and turns it on.

Then after that the only thing that’s left is the unmarked red wire, our hot lead, from our new 18-volt power supply.

On the preamp we remove the connection from the old battery setup, solder the hot lead to that tab, protecting the connection with heat shrink tubing.

Testing out your new setup

Step seven: Test it out

Now our battery box is installed and wired, so we want to put in a couple fresh batteries and test it out. Batteries only fit into the battery holders one way, so if it closes, you’ve done it right. Now plug in the bass and see how it sounds.

If everything sounds good and you’re content, it’s time to return everything to the control cavity and screw back in the pickguard. The fit shouldn’t be as compact without the battery in there, but still be careful not to pinch anything off while putting everything back in.

And there you have it. Your bass is now running on 18-volts from a battery box.