You'll find the vent holes along the sides of the top, just over the edge. Another place I've found them is under the labels. The theory being that if the pressure gets too high the label will lift -before- the case bursts. Many of these batteries use recombination technology, so they don't -normally- vent. They will in exceptional circumstances, when something goes wrong. Installing a vent tube may be very difficult. So you'll have to decide if venting is desired yourself.
The vent is there precisely if something goes wrong. You don't want explosive or noxious gases in the cabin, nor corrosive liquids spraying around inside the battery compartment. Leave the vent unconnected at your peril.
Another problem with Gel Cell is that they last long with fast charging(high current). Plus they are slightly more expensive than AGM.
My Prius has been laid up for over a year and a half..I am thinking it was my inverter toasted..but that's for another discussion.. I pulled my dead 12v battery out and got it to take a charge...the digital read out on my charger has it showing at 13.1 Volts.. What should I be hoping for? The Obvious answer is 12V for a 12 V battery..but..sometimes things are not always obvious..My hope is that this is good enough for me to crank her up and put my PC based scan tool on it and get some diagnostic readings to put up here... Also..I KNOW getting my car running is gonna be a project...and I am gonna need help..would you guys suggest I start a thread of my own? I have already ordered and received a Traction Battery with 40k miles on it..
For anyone interested in the longevity of the 12v battery in a 2001 Prius, I am just starting to have problems with mine. It is the original battery that came with the car. I am the original owner, and I purchased it 10-years ago in 2001. Odometer reads 157,300. I use the car for commuting to work (25-miles each way) and various other typical short trips. I've accidentally drained the battery a couple times by leaving the dome light on and had to use jumper cables the next morning. ... But after driving to work, the battery was charged up pretty well. That was a couple years ago. This time, I think the battery is finally on its last leg. But I'm quite impressed by how long it lasted !!
Well, mine is starting to act up. Leave the interior light on overnight and no start in AM. However this is the original battery in my 02 with 203,000 miles. Is there an aftermarket that is as good as the original?