AGM Battery Mounting sideways?

Pretty sure I know the answer to this one already but just want to run it by the learned collective here. I just bought a small foot-print AGM/SLA battery for my '54 Velocette that fits inside the Lucas rubber battery box. If I try to fit it inside in the upright orientation, it is a very tight fit, such that trying to remove again one day might be near impossible without cutting the rubber box away. It does however fit nicely oriented on one end. I understand there is a venting system in the otherwise sealed battery and some cautions I've come acrss warn about mounting them upside down. Why would sideways be OK but upside down be a no no?

I found: "Yes, you can mount an AGM battery sideways or vertically. Make sure it is secured to prevent movement. Do not mount it upside down due to the vent at the top. This vent allows gas release and can lead to fluid leakage if blocked. Ensure proper pressure relief for safety considerations."

marshg246 said:

I found: "Yes, you can mount an AGM battery sideways or vertically. Make sure it is secured to prevent movement. Do not mount it upside down due to the vent at the top. This vent allows gas release and can lead to fluid leakage if blocked. Ensure proper pressure relief for safety considerations."

Click to expand...

Yes, that's sort of what I've been seeing...but can't wrap my mind around how a vent at the top can work in batt on the side but not upside down?

Tornado said:

Pretty sure I know the answer to this one already but just want to run it by the learned collective here. I just bought a small foot-print AGM/SLA battery for my '54 Velocette that fits inside the Lucas rubber battery box. If I try to fit it inside in the upright orientation, it is a very tight fit, such that trying to remove again one day might be near impossible without cutting the rubber box away. It does however fit nicely oriented on one end. I understand there is a venting system in the otherwise sealed battery and some cautions I've come acrss warn about mounting them upside down. Why would sideways be OK but upside down be a no no?

Click to expand...

I own two modern motorcycles with AGM batteries on their side. No problems.

Tornado said:

Yes, that's sort of what I've been seeing...but can't wrap my mind around how a vent at the top can work in batt on the side but not upside down?

Click to expand...

It can work anyway, but upside down means it may be sitting on the vent blocking it.

marshg246 said:

It can work anyway, but upside down means it may be sitting on the vent blocking it.

Click to expand...

Yes that seems to be the only explanation I can find.

Mine should be fine on its small end with the terminals vertically one above the other. There really were no other formats that fit the rubber casing, with terminals at the top. The bike came with a pair Lucas-branded 6v batteries in series to make 12v. These had spade connectors and appeared to be more like as used for building emergency lighting backup power or alarm systems...not like any automotive battery I've seen before. The pair have unknown history so maybe some years old, but were working fine for a season and a half before starting to show loss of storage/not charging on my maintainer. 4-Ah each batt...so is that 8-Ah when in series? Replacement AGM is 6-Ah...must weigh 2x what the old pair weigh.

In series they would be 4ah at 12 volts. In parallel would be 8ah at 6 volts.