Venting a modern battery in a C3

[Mark E.]

What's the best practice for venting when using a modern replacement battery in a C3?

I searched the Forum and the most relevant post I found is this entry by KEN BUTCHER in this 2005 thread:

"...if you have a modern battery and not the repro you can still put the two vent tubes on. Because the modern batteries don't have caps on top and are considered maintenance free, they still have vent outlets, which if you look closely are on the top to the side. They look like small oval tubes. If you want to attach the rubber tubes to the small oval tubes, here is an idea. It worked for me. Go to a parts store that sells electrical connectors and you should be able to find a connector that has a sleeve that is the same shape and will fit over the vent tube on the battery. The other end is round like the rubber vent tube. Since it is an electrical connector you will have to remove the metal clip inside the connector. When you get that done the rubber tube fits over the round end of the electrical connector and the oval end fits over the vent tube on the battery."

I don't believe all modern batteries have vent ports, but some do. I own a '93 Cadillac Allante which uses a sealed, side terminal battery installed behind the seat. Its battery has a vent port on each end near the top, which connects to these vent tubes on the Allante:



The Allante's ACDelco battery part number is 78VPS; its description on the ACDelco website:

Silver BCI Group 78 Battery
Part Number: 78VPS
BCI 78 CCA 770, Battery is vented to outside of the vehicle

Its dimensions, 10" long x 6.7" wide x 7.5" high, are close to the dimensions of R89W Corvette Reproduction Battery for the '70 Corvette

[Terry M.]

Re: Venting a modern battery in a C3

What's the best practice for venting when using a modern replacement battery in a C3?

I searched the Forum and the most relevant post I found is this entry by KEN BUTCHER in this 2005 thread:

"...if you have a modern battery and not the repro you can still put the two vent tubes on. Because the modern batteries don't have caps on top and are considered maintenance free, they still have vent outlets, which if you look closely are on the top to the side. They look like small oval tubes. If you want to attach the rubber tubes to the small oval tubes, here is an idea. It worked for me. Go to a parts store that sells electrical connectors and you should be able to find a connector that has a sleeve that is the same shape and will fit over the vent tube on the battery. The other end is round like the rubber vent tube. Since it is an electrical connector you will have to remove the metal clip inside the connector. When you get that done the rubber tube fits over the round end of the electrical connector and the oval end fits over the vent tube on the battery."

I don't believe all modern batteries have vent ports, but some do. I own a '93 Cadillac Allante which uses a sealed, side terminal battery installed behind the seat. Its battery has a vent port on each end near the top, which connects to these vent tubes on the Allante:



The Allante's ACDelco battery part number is 78VPS; its description on the ACDelco website:

Silver BCI Group 78 Battery
Part Number: 78VPS
BCI 78 CCA 770, Battery is vented to outside of the vehicle

Its dimensions, 10" long x 6.7" wide x 7.5" high, are close to the dimensions of R89W Corvette Reproduction Battery for the '70 Corvette

C6 Z06s use a vented battery because it is installed in the right rear corner of the passenger compartment. Vented flooded and AGM batteries are available for this application.

IIRC (working from memory here) the CCA is 800 for this battery. Not nearly enough IMO, but it is what it is.

[Joe L.]

Re: Venting a modern battery in a C3

C6 Z06s use a vented battery because it is installed in the right rear corner of the passenger compartment. Vented flooded and AGM batteries are available for this application.

IIRC (working from memory here) the CCA is 800 for this battery. Not nearly enough IMO, but it is what it is.

Terry------


C6 Corvettes use a top terminal battery; all C3 except 1968 and most 1969 use a side terminal battery. So, the C6 battery, for this reason alone, would not be compatible with a C3.

The 78VPS battery is a group 78 battery which is the correct size for all C3 applications AND it's a side terminal type battery. So, if one is concerned about external venting for a maintenance-free battery, then the 78VPS is the way to go.

[Mark E.]

Re: Venting a modern battery in a C3

Thanks guys.

Is using a modern vented battery like 78VPS a common practice for us C3 owners?

The impression I have is there are two main categories of C3s: show cars with reproduction batteries and original style vents, and drivers with sealed batteries that are not vented to the outside. Not venting the battery in these cars doesn't seem like a good practice, and it looks like using 78VPS is a good way to go for drivers.

[Joe L.]

Re: Venting a modern battery in a C3

Thanks guys.

Is using a modern vented battery like 78VPS a common practice for us C3 owners?

The impression I have is there are two main categories of C3s: show cars with reproduction batteries and original style vents, and drivers with sealed batteries that are not vented to the outside. Not venting the battery in these cars doesn't seem like a good practice, and it looks like using 78VPS is a good way to go for drivers.

Mark-------


Best practice or otherwise, I expect the number of C3's that have been equipped with the 78VPS by their owners you could count on the fingers of one hand. I don't think it's a bad idea, though. I might even do it myself next time PROVIDING I can get a 7 year Delco battery in this size.

By the way, after GM went to maintenance-free batteries in C3 Corvettes in 1976, no external venting was provided.

[Mark E.]

Re: Venting a modern battery in a C3

Mark-------
I might even do it myself next time PROVIDING I can get a 7 year Delco battery in this size.

By the way, after GM went to maintenance-free batteries in C3 Corvettes in 1976, no external venting was provided.

The ACDelco 78VPS has a 30 month free replacement warranty, which isn't bad for a $112 battery.

So the batteries in 76 - 82 Corvettes are not vented?? That's curious because GM vented the maintenance-free batteries for Allantes (87-93) and C6 Z06s, as Terry pointed out.

Is this tacit acknowledgement by GM that it was a mistake to not vent batteries located in the interior??

[Michael F.]

Re: Venting a modern battery in a C3

Mark, any car shows you know of in DFW area this weekend? I am coming over to see family. thanks.

Mike

[Leif A.]

Re: Venting a modern battery in a C3

Mark, any car shows you know of in DFW area this weekend? I am coming over to see family. thanks.

Mike

Cars & Coffee at Classic BMW, Dallas Parkway and Spring Creek Blvd. Typically over 800 cars, of all types, on display. Saturday, July 4th,from 7:30am-11am but most will be gone by 10am. Come on by...great time, great cars. Held the first Saturday of every month.

[Terry M.]

Re: Venting a modern battery in a C3

Terry------


C6 Corvettes use a top terminal battery; all C3 except 1968 and most 1969 use a side terminal battery. So, the C6 battery, for this reason alone, would not be compatible with a C3.

The 78VPS battery is a group 78 battery which is the correct size for all C3 applications AND it's a side terminal type battery. So, if one is concerned about external venting for a maintenance-free battery, then the 78VPS is the way to go.

Good point Joe. I forgot all about the change back to top terminals.

[Gene M.]

Re: Venting a modern battery in a C3

For what it's worth (free) I have an Optima battery (red top) in my 68. It has both top and side terminals. There is plenty of cranking power and it is sealed no vents needed. Not a good choice for judging but very functional for driving.

[Joe L.]

Re: Venting a modern battery in a C3

For what it's worth (free) I have an Optima battery (red top) in my 68. It has both top and side terminals. There is plenty of cranking power and it is sealed no vents needed. Not a good choice for judging but very functional for driving.

Gene------


Delco has a group 78 battery with both top and side terminals. It's a 78DT. Of course, it's not sealed like an Optima.

[Mark E.]

Re: Venting a modern battery in a C3

I have an Optima battery (red top) in my 68. It has both top and side terminals. There is plenty of cranking power and it is sealed no vents needed. Not a good choice for judging but very functional for driving.

Gene, A "sealed" battery means there are no caps to add water; it does NOT mean it won't gas. Most modern batteries are sealed, but only a few are designed for sealed battery compartments like we see in C3s. Those sealed batteries (like the 78VPS) have provisions to connect vent tubes which exhaust gasses to the outside.

With that said, I believe (maybe someone can confirm) that AGM batteries tend to gas less than conventional batteries, so that's good. But they still gas. From Optima's website:

"Does an OPTIMA battery ever gas? When used with a properly regulated constant voltage charging system (such as an alternator), the OPTIMA will not emit hydrogen gas. However, gassing can occur when charging at excessive voltage levels or in extreme high-temperature conditions. In automotive applications, this typically will not happen if the alternator/regulator stays below 15 volts."

So maybe you're ok if everything is working properly, but it can gas if there's a malfunction or it encounters "extreme high-temperature conditions" (whatever that is... over 200 deg?... 100 deg?... leaves me wondering...)

[Mark E.]

Re: Venting a modern battery in a C3

Cars & Coffee at Classic BMW, Dallas Parkway and Spring Creek Blvd. Typically over 800 cars, of all types, on display. Saturday, July 4th,from 7:30am-11am but most will be gone by 10am. Come on by...great time, great cars. Held the first Saturday of every month.

There may be other events in North Texas, but it's so hot that the early morning venue of Cars & Coffee is usually the most bearable in the Summer. My '70 has its interior out, so maybe I'll take the Allante and look for Michael and Leif. I should be easy to spot- probably the only Allante there.

[Gene M.]

Re: Venting a modern battery in a C3

Gene, A "sealed" battery means there are no caps to add water; it does NOT mean it won't gas. Most modern batteries are sealed, but only a few are designed for sealed battery compartments like we see in C3s. Those sealed batteries (like the 78VPS) have provisions to connect vent tubes which exhaust gasses to the outside.




With that said, I believe (maybe someone can confirm) that AGM batteries tend to gas less than conventional batteries, so that's good. But they still gas. From Optima's website:

"Does an OPTIMA battery ever gas? When used with a properly regulated constant voltage charging system (such as an alternator), the OPTIMA will not emit hydrogen gas. However, gassing can occur when charging at excessive voltage levels or in extreme high-temperature conditions. In automotive applications, this typically will not happen if the alternator/regulator stays below 15 volts."

So maybe you're ok if everything is working properly, but it can gas if there's a malfunction or it encounters "extreme high-temperature conditions" (whatever that is... over 200 deg?... 100 deg?... leaves me wondering...)

Interesting, so as long as the operation conditions remain "in spec" the Optima should work ok. I have not noticed any venting issues on my 68. Most rides are fairly short to the cruise and such. When it sits in the garage it is always on the battery tender with windows down just because it seems the smart thing to do.

[James B.]

Re: Venting a modern battery in a C3

Just wondering if anyone has any updates on this topic, including actual installation experience of the 78VPS battery.


James