Community Member Credit: Aaron92SE

First off, I just want to say that I got this idea from Jime. He purchased a 300amp battery jump box and used the battery out of it for his car. It weighed 6 lbs. I believe he had problems with it starting. So he purchased a 400amp battery jump box with a 12lb battery and has been using that ever since without issues. Jime, please correct me if I say anything incorrect. Thanks.

So I found that Harbor Freight had the best deal on a Battery Jump Box. So I purchased a couple of them. One to keep in the trunk of my car and one to use the battery out of.

The jump box I used was a 650amp one found here (Item #40615):

It’s the largest one they had. But before I ripped into this one, I looked at the manual and simply decided to order the replacement battery direct from Harbor Freight by calling their customer support at 1-800-444-3353. The battery cost $32.70. I order another battery for my HF drill, so that increased shipping costs to $7.99 instead of approximately $6.00 I think. The item number printed on my receipt for the battery is 26307. But you shouldn’t need that. Just give them the item number for the Jump Box and tell them you want the replacement battery.

The battery weighs 14lbs.

Here is what the battery looks like:

First I had to install “flag to post” adapters. I ordered them through my local Napa store (Part # NW 728219) for $6.29. They come in a pair and were cheaper than ordering them online from a battery supply store.

I had to slightly drill out the flag terminals on the battery with a step drill bit in order to use some spare M6 bolts I had laying around.

Next, I had to figure out a way to mount it in my 3rd gen. I really wanted to get rid of the battery tray as well for further weight reduction. But this posed several other problems. One being, the coolant tank attached to one of the battery tie down bolts. Plus, a couple relay boxes attach to the battery tray.

Out with the old battery. It weighed in at 40lbs and the tray is 3lbs.

I zip tied the coolant tank to the coolant tube on the VQ35. I know it’s ugly, but it’s ok. I’m only worried about performance here.

I put a fresh coat of paint on my OEM tie down. I found two bolt holes already in my frame that I was able to use. So I had these long M6 bolts laying around that I was able to use.

Here is what the battery looks like installed. I put some rubber bands on the bolts to prevent the bolts from ever dropping through the bolt holes. The bolt holes in my frame were threaded for M8 bolts and I didn’t have any M8 bolts that were long enough or I would have used those.

I was able to zip tie the relay boxes securely.

I installed a cheap Harbor Freight multimeter inside my car so I can always keep an eye on battery voltage. So far, this battery cranks my car up just fine. I have noticed that sometimes, the engine has to turn over one more time to get it to fire up. But this is not a concern. I believe this may be due to the engine turning over a tad slower than before. My old battery was the largest and highest CCA Duralast battery that Auto Zone had to offer. But it’s served it’s life as I bought it back in 2003.

Well that’s it. A weight reduction of 29lbs for under $40! I hope this helps somebody in the future. Thanks Jim for the idea!

I went to Advance Auto Parts today and bought a battery for $31.99. It has 230CCA and 275CA and weighs 15lbs. It works just fine in the summer. So I’m happy. I just had to make a new tie down since it sits higher than the jump box battery. Car starts with plenty of power.