Quote:
Originally Posted by FrankJ
My preference is to charge upright. Truth is it really doesn't matter 99.9% of the time. My UPS has one of its batteries permanently upside down. The battery manufactures generally do not recommend this. Flat is OK. AGM & glass mat batteries have very little free liquid in them. Using a smart charger & charging at recommended charge rates is more important then battery orientation.
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I would still charge upright if at all possible. Venting isn't really a concern with FRC batteries but gas pockets can be. At full charge ideally each cell has a plate of pure lead(Pb), one of pure lead oxide(PbO2), and sulfuric acid(H2SO4) as the electrolyte(in practice diluted with H2O). When you discharge both plates turn into lead sulfate(PbSO4), giving up electrons and creating more H2O. Sulfuric acid is completely soluble in water so that mixes just fine.
This is not true while charging. Hydrogen gas is created and there's a chance a pocket gets trapped against a portion of a plate that can't react with it. That portion doesn't charge, slightly reducing total capacity. Do this enough and you start real damage to the battery. This is negligible at trickle charge rates like a UPS sees, but we at FRC like to charge our batteries as quickly as allowed.