Mountain Project Logo

car battery question


Original Post
JulianG · · Unknown Hometown · Joined Oct 2009 · Points: 130

I know that the acid is bad and manufactures don't want us to store gear in the cars. Is it because Hydrogen-Sulfide? How bad is exposure to batteries fumes for the nylon?

VW Vanagons has the battery under the driver seat and possibly a second one under the passenger seat, both batteries not vented outside. Vanagons have been used by climbers for decades there should be a lot of gear disintegrating.

There are a lot of people having solar panels and big batteries in vans. Is a properly vented flooded sealed battery as safe as a AGM one?

Matt Himmelstein · · Orange, California · Joined Jun 2014 · Points: 125

It is all about air exchange. VWs may not have well sealed batteries, but the car is also not that well sealed. Exposure to fumes will damage your gear. How fast, and by how much, depend on a myriad of variables.

20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,348

It's because of sulfuric acid, which makes up a portion of the electrolytic fluid in the battery. However, Hydrogen-Sulfide will damage gear as well. I do recall reading one study relating to nylon and hydrogen-sulfide exposure from an automotive battery. The test was informal but it concluded that the samples were compromised and they failed at loads lower than the control.

With regard to the solar setups, most of those guys are running AGMs. I run an AGM in my vehicle. Others mount their batteries outside or under the hood. Some build a battery box and vent it outside (the least safe of the options). The uninformed might have a flooded wet cell battery just chilling inside, but it's a really bad idea.

I cant comment on the vans you're talking about, but all modern vehicles I've seen have externally vented batteries if the batteries are kept inside the vehicle. All hybrids have their batteries (both the HV and LV battery) vented outside. You might want to look at getting an AGM replacement if VW dident integrate a proper venting system. Optima makes some good replacement AGMs and they last a long time.

JulianG · · Unknown Hometown · Joined Oct 2009 · Points: 130

I got my info from here batteryuniversity.com/learn…

It looks like hydrogen sulfide is produced only when the battery is overcharged and that is unlikely with solar batteries with a controller.

There are plenty of drafts in the vanagon. I call it AC.

20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,348
JulianG wrote:I got my info from here batteryuniversity.com/learn… It looks like hydrogen sulfide is produced only when the battery is overcharged and that is unlikely with solar batteries with a controller. There are plenty of drafts in the vanagon. I call it AC.
All automotive batteries produce hydrogen when being charged, regardless if overcharged or not. You can visually see this by taking the cap off your auto battery with the vehicle running. Shine a flashlight into the holes and you will see bubbles rising to the surface. That's hydrogen sulfide. You can smell it too if you place your nose close, although I wouldent recommend that. The battery will actually continue to produce hydrogen after the charging source is removed for a minute or two as well.

It is true, however, that batteries produce far more hydrogen when overcharged. If severely overcharged, the electrolytic fluid will start to boil and it will escape out of the cap. If the battery is an AGM, the pressure will activate the release caps and the battery will vent. I actually saw this happen the other day on a boat. The alternator failed and dumped 32V into the batteries (24v system). The AGM batteries vented and spilled acid into the bilge.

So in short, all 12v auto batteries produce hydrogen when being charged, they just produce far more when overcharged. AGM batteries either use a hydrogen filter (e.g. Optima) or they recombine the gases. Flooded batteries just vent the gases (and if needed the acid as well) into the atmosphere. Take note to the below video. The battery was not being overcharged. It was sitting on a 10A charger, which is far less current than your alternator can produce if needed.

youtube.com/watch?v=d_TnsHu…
Guideline #1: Don't be a jerk.

Post a Reply

Log In to Reply