Hummer H3 For the Hummer driver who wants the rugged look and off road capabilities of the Hummer, but in a smaller size and with a more fuel economy friendly engine.

2020 GMC battery fits H3

Old Mar 4, 2025 | 11:42 AM
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Default 2020 GMC battery fits H3

I had my GMC dealer replace the battery in my wife's 2020 at no charge with my gm rewards & received the old battery since it still tests good.
It's a group 48agm battery 2" longer(11") than the H3 group 86(9") battery with the same width to fit into the wedge mount hold down.
After removing the old battery, the lower plastic battery cover pulls out after removing 2 wiring harness connector clips attached.
Underneath the plastic cover the steel tray has an extra 2" length for an 11" long battery to set on. Then install the strap & wedge hold down to hold the battery secured in place.







 
Old Mar 4, 2025 | 04:25 PM
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Anything will fit if you remove the darn batter tray! Why is this news?

I have 2 huge Optima Yellow Tops in the same location.




 
Old Mar 4, 2025 | 05:47 PM
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Fits without modification is the reason for the post.
6-7/8" width fits secured in between the wedge hold down bracket mount. 11" length fits inside the metal edging border. Larger would require modification.
 
Old Mar 5, 2025 | 05:59 AM
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Originally Posted by hummerz
Fits without modification is the reason for the post.
6-7/8" width fits secured in between the wedge hold down bracket mount. 11" length fits inside the metal edging border. Larger would require modification.
Ahh, removing the battery cover and the battery base is NOT a modification. Sure!
 
Old Mar 7, 2025 | 11:53 AM
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Originally Posted by TAINTER

Anything will fit if you remove the darn batter tray! Why is this news?

I have 2 huge Optima Yellow Tops in the same location.
Got some pictures or thread on this mod?
 
Old Mar 7, 2025 | 06:46 PM
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Originally Posted by Happy Hummer
Got some pictures or thread on this mod?
Originally Posted by TAINTER

Anything will fit if you remove the darn batter tray! Why is this news?

I have 2 huge Optima Yellow Tops in the same location.


 
Old Mar 10, 2025 | 12:54 PM
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I'm thinking it looks just like this.....................

 
Old Mar 10, 2025 | 02:09 PM
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The tray is big enough to take much larger than the stock battery.

The stock battery is rinky dink and "bigger is better"...
 
Old Mar 10, 2025 | 04:45 PM
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That's my "T", Thanks Doc!
reran all of the OEM wires after separating them from the OEM loom. re-loomed and heat shrank all the hydraulically crimped connectors.
Fuse cover still come off easily.


Originally Posted by Doc Olds
I'm thinking it looks just like this.....................
 
Old Mar 10, 2025 | 06:11 PM
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Originally Posted by TAINTER
That's my "T", Thanks Doc!
reran all of the OEM wires after separating them from the OEM loom. re-loomed and heat shrank all the hydraulically crimped connectors.
Fuse cover still come off easily.

YOU MODDED WITH PLASTIC BASE PLATES TO HOLD THOSE BATTERIES SECURED ON THE METAL EDGING BORDER FRAME BELOW!
BTW, OPTIMA BATTERIES R UNABLE TO HANDLE EXTREME TEMPS!
 

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