Thought you guys might like to see how I shoehorned a UPG 75 Ah battery under the hood of my 2008 Tacoma

andrew61987

Observer
I knew going into this that the ATO dual battery tray was designed for two Optimas which are smaller than the batteries I intended to use. I figured the tray would still be a good starting point and it was. My Interstate starting battery (stock group 24 for the 4 cylinder) was still good and I didn't want to replace it. I also wanted to use a true deep cycle not a dual purpose batt like the Optima yellow top or similar. I also wanted a solid, non-hack job install that I could rely on because I frequently take this truck way out in the Sierras for days at a time. I think I accomplished that the best I could.

Point 1: Height. I test fit everything and discovered that my Interstate was a hair too tall, and the UPG battery was even taller. The problem was the negative terminal was barely contacting the hood. While not as bad as the positive touching the hood it still needs to be fixed. I did this by cutting about 3/8" off the standoffs that come with the ATO tray. I filed them to clean up the cuts and made sure they were all the same length. Because of the shape of the hood near the edges changes I didn't need to worry about the taller UPG battery touching.

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Point 2: Dimensions. The Interstate battery fit perfectly in the tray which has tabs that are 10 inches apart. The UPG battery however was about 10-1/8" so I did a combination of slightly bending the tabs out and grinding. Filed off sharp edges and painted of course after, don't want sharp edges slowly vibrating a hole in the battery over time.

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Point 3: Fuse box. There was no way to avoid moving the fuse box an inch or so. The wires have the required play, I just put self tappers into the two lower bolt holes into the fender well and created a simple bracket to use existing bolt holes to relocate the upper mounting point. Helps to use a metric tap (I forget the size) on one of the bracket holes to re-use the Toyota fuse box bolt.

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Point 4: Factory battery cables. These need to reach the starting battery. The negative was long enough to reach without putting it under tension, I did however have to relocate the ground (see pic). The positive was not long enough so I had a nearby audio shop fix me up with a 1 foot section of 2 gauge that I used to extend the factory positive. I did some bending, cutting, and grinding on the factory end to make a nice connection to the extension which I attached to the factory lug which was bolted to the post like stock. Of course this wire needs to be well protected to prevent accidental shorts.


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Other than that all I had to do was create custom J hooks (the ones in the kit were too short) by bending and threading a 1/4" rod from the hardware store with a 1/4 by 20 die and put a spacer (thin piece of wood with rubber feet taped on) between the hold-down plate and the shorter interstate battery to make sure they were both held snugly by the hold-down plate.

Overall I'd recommend the ATO tray for this purpose, obviously it's not a direct fit given the batteries I wanted to use but it's a solid base that's positioned just right and fabbing something custom given the tight clearances around the stock battery area would have been a nightmare and not nearly worth the savings.

Might not be the best or easiest way to do this but I'm really happy with how it turned out and hopefully this helps somebody or at the least conjures up some ideas for how you want to do your setup.

I believe everything I did is equally applicable to the V6 depending on year, I know some years have room to stash it passenger side up near the firewall.

Ready to be wired in!

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nyrixx

New member
I was initially looking at batteries like this when I was shopping around for my dual battery setup and I ended up going a different route because I was unable to find one with a good operating temperature rating for under the hood installation. Then again I live in Texas and will primarily be traveling the southwest so your use case May differ from mine.

Nice looking install regardless.

Sent from my Pixel XL using Tapatalk
 

Dopesick

Does a bear..........
View attachment 447995
Point 4: Factory battery cables. These need to reach the starting battery. The negative was long enough to reach without putting it under tension, I did however have to relocate the ground (see pic). The positive was not long enough so I had a nearby audio shop fix me up with a 1 foot section of 2 gauge that I used to extend the factory positive. I did some bending, cutting, and grinding on the factory end to make a nice connection to the extension which I attached to the factory lug which was bolted to the post like stock. Of course this wire needs to be well protected to prevent accidental shorts.

The extension of the battery cables, is a really bad idea. You've created a possible failure point, and a resistance (voltage drop) point. Personally, I would NEVER return back to the audio shop you visited. They should have either talked you into removing the factory cables and replacing them with the correct length and gauge cables, or not touched your truck at all.

FWIW: I am a (now expired) MECP Certified Mobile Installer, and retired Mechanic.
 

andrew61987

Observer
The extension of the battery cables, is a really bad idea. You've created a possible failure point, and a resistance (voltage drop) point. Personally, I would NEVER return back to the audio shop you visited. They should have either talked you into removing the factory cables and replacing them with the correct length and gauge cables, or not touched your truck at all.

FWIW: I am a (now expired) MECP Certified Mobile Installer, and retired Mechanic.
What do you propose will happen? I understand that resistance in series is additive, but I have a hard time believe that the additional resistance I've created through that connection significantly adds to the existing resistance through the entire wire and the connections on both ends of it that already exist. The extension is really only taxed during cranking, and is of larger gauge than the existing wire. Are you saying the added connection may heat to the point of danger during cranking? Is there any reason I can't confirm the quality of the connection by measuring resistance from A to B, then A to C, with A being the starter and C being the battery, and comparing the difference to the total?
 
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Dopesick

Does a bear..........
Correct. You introduced an additional mechanical connection point, which is an additional failure point for three reasons.

1: The mechanical connection itself. - Additional Resistance, vibration (slightly mitigated with lock washers).
2: Galvanic corrosion between the (what I see as a minimum of 3) different metals.
3: The weight of the connection, movement, heat, and reliance on just electrical tape.

What should have been done, while installing the battery, was a Modified "Big 3" upgrade. https://jlaudio.zendesk.com/hc/en-us/articles/204374080-The-Big-3-Wiring-Upgrade
 

DaveInDenver

Middle Income Semi-Redneck
? Is there any reason I can't confirm the quality of the connection by measuring resistance from A to B, then A to C, with A being the starter and C being the battery, and comparing the difference to the total?
You can in theory measure the resistance change using that bolted connection. You'll need a very sensitive meter to do it accurately, but even a handheld meter will show you've probably doubled the resistance by doing this.

The order of magnitude here is tens of milliohms and if your stock wiring had 20 mΩ and you doubled that to 40 mΩ during cranking the difference could be you reduce the voltage at the starter by a couple of volts.

FWIW, I don't like that solution either but it can be made reliable (anti-corrosion grease, a lock washer, etc). Think of this way, what you've done is essentially made a small bus bar and people do that often. A bus bar can be an improvement over trying to cram 4 cables on a battery post terminal, for example. When people do this, though, they are usually replacing all the cables with larger gauge as well, which reduces the resistance of each branch so the addition of some in the bolts on the bus bar isn't a big deal.

The problem is you didn't replace the factory cable, which is already undersized, and have added the bolted connection to make it worse. Like @Dopesick says, you should have just replaced the whole wire.
 

andrew61987

Observer
Ok, thanks for the suggestions. In the meantime I will add additional vibration support to the harness, replace the bolt with stainless, add terminal grease, check it frequently, and take another look at full cable replacement.

I did look into it to begin with actually, but FWIW the reason I went the route I did was because it wasn't just the starter cable I needed to replace. There were one or two others that would also need to be remade, and the thought of regularly inspecting/maintaining/worrying about the quality of 4-6 non-factory crimps and 4-6 non-factory connections in hard-to-reach locations was more concerning to me than 2 non-factory crimps+connections in an easy to inspect, easy to maintain location, even if I do end up servicing them every oil change.
 
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Dopesick

Does a bear..........
So instead of worrying about the crimps, do what I would do. Crimp them, and then solder the crimp terminal. This is how I treat ALL of my electrical connections that would normally be crimped. Solder will do you a couple of favors. Make a better mechanical and electrical connection, and increase corrosion resistance by "sealing" the joint.

As DaveInDenver mentioned, the factory cables are usually "bare minimum" to get the job done safely in Most cases. Well Most case solutions suck, and the factory will always side with lowest cost vs over doing it. This is why the "Big 3" upgrade is damn near required for any of us doing modification to the vehicles when it comes to additional electrical load. Hell Toyota even had a recall on the Tacoma and 4runner for "long crank" condition. The fix was replacing the battery to starter and main electrical with a larger gauge.
 

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