batterieschargechargingdischargelead-acid
I have a small, 12V sealed lead-acid battery. I know regular lead-acid batteries can be dangerous to use or charge indoors, due to the fumes they release and the potential for acid to leak out or spill. A sealed lead-acid battery wont release fumes or spill though, correct? Does this make it safe to use/charge indoors?
Thank you!
Water shouldn't be able to get inside sealed lead-acid cells. The terminals are not environmentally sealed, though. If you backpack gets soaked, they battery could discharge through the wet cloth.
Cold increases the internal resistance of the batteries. As a result, you lose more energy on the internal resistance. You will get less charge back from the battery. Max output current also decreases*. At 00C, you should still be able to get few amperes necessary for charging your gear.
* BTW, vehicle starter batteries are rated for Cold Cranking Amperes. So, they are rated for the worst case.
Neither approach is good.
See http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery
Most stationary batteries are kept on float charge. To reduce stress, the so-called hysteresis charge disconnects the float current when the battery is full. As the terminal voltage drops due to self-discharge, an occasional topping charge replenishes the lost energy. In essence, the battery is only “borrowed” from time to time for brief moments. This mode works well for installations that do not draw a load when on standby.
Lead acid batteries must always be stored in a charged state. A topping charge should be applied every six months to prevent the voltage from dropping below 2.10V/cell.
I believe the main issue, relevant to this question, is sulfation
Solar cells and wind turbines do not always provide sufficient charge, and lead acid banks succumb to sulfation.
...
During prolonged charge deprivation, however, the amorphous lead sulfate converts to a stable crystalline that deposits on the negative plates. This leads to the development of large crystals, which reduce the battery’s active material that is responsible for high capacity and low resistance. Sulfation also lowers charge acceptance.
Best Answer
Actually SLA batteries have a vent... so the name "sealed" is a bit of a misnomer. VRLA (valve-regulated lead-acid battery) is actually a name for the same tech.
Practically every UPS (uninterruptible power supply) I know of has one [or more] SLA[s] inside, so it's generally safe for indoor use. Here's a snippet from an APC white paper on the issue:
And bit later in the paper the difference in gas output is quantified as 60 times less for VRLA:
And the reason for this is that in a "sealed"/VRLA battery:
The fact that they're pressurized explains why in extreme cases of misuse or abuse they end up seriously bulged. The plastic container is actually designed to cope with that scenario.
Also, small SLAs (almost certainly the one you have) use gel as electrolyte suspender so won't spill liquid[s] even if cracked. The larger ones use a glass mat instead (gel is rather expensive).