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There’s a lot of confusion around AGM battery venting, especially for interior or under-seat mounting. They all say “no liquid to spill, etc” but the gas can still escape.
So the OEM AGM in the Defender has a vent tube requirement. That is not cheapness, it’s OEM safety engineering for worst-case events.
All AGM batteries, including Odyssey and Optima, do in fact have vents and designed to vent under overcharge or thermal events (not normal usage or charging tho).
I wasn’t familiar with Odyssey having never owned one but their technical manual states that the battery should not be mounted with the vents inverted and then also see Page 13 of their technical manual: https://www.odysseybattery.com/wp-content/uploads/AMER-EN-TM-ODY.pdf. So venting external is possible under problem conditions.
So I personally would not choose an AGM battery under-seat or interior mounting where there is no way to route a venting event outside the cabin. I’d go either stock setup or Lithium Ion (Antigravity, etc).
Last edited by nashvegas; Jan 21, 2026 at 07:08 AM.
Reason: I ghtought you were talking about Optima, you were talking about Odyssey
There’s a lot of confusion around AGM battery venting, especially for interior or under-seat mounting. They all say “no liquid to spill, etc” but the gas can still escape.
So the OEM AGM in the Defender has a vent tube requirement. That is not cheapness, it’s OEM safety engineering for worst-case events.
All AGM batteries, including Odyssey and Optima, do in fact have vents and designed to vent under overcharge or thermal events (not normal usage or charging tho).
I wasn’t familiar with Odyssey having never owned one but their technical manual states that the battery should not be mounted with the vents inverted and then also see Page 13 of their technical manual: https://www.odysseybattery.com/wp-content/uploads/AMER-EN-TM-ODY.pdf. So venting external is possible under problem conditions.
So I personally would not choose an AGM battery under-seat or interior mounting where there is no way to route a venting event outside the cabin. I’d go either stock setup or Lithium Ion (Antigravity, etc).
Thanks, I'll look into it. Maybe I just never noticed but I'm going to check the 2 under the hood in my LR3. They are the PC1350 and PC2150 extremes
Topo Side Window Panel Overlays installed, I'm digging the look of the overlays and I may black out the A-pillers next...I want the floating roof look. I would buy them again, the vinyl is top quality and very robust.
I installed the topo design with the clear topo lines to pick up the body color (they offer gray, desert sand, and clear line colors) and the come with passenger and driver side overlays.