By Petra PaulsonA swelling battery tends to result from overcharging and should immediately be removed from its charger or the device to which it's currently connected.Continuing to charge your Yuasa NP7-12 battery after it's reached full capacity can cause water in the electrolyte cells to deteriorate. At its worst, excessive charging can actually lead to a drastic temperature increase inside the battery. Hot batteries draw more current, which causes internal pressure to build up. The battery will eventually expand as a result of this "thermal runaway." This can be extremely destructive to a battery's internal cells, and render it unusable in a matter of hours. For that reason, make sure never to overcharge sealed lead-acid batteries.
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