Deep Cycle Batteries Feel Warm and Smell Bad

When deep cycle or lead acid batteries get close to their end of life, it is noticeable that the energy storage becomes quite small and they don't last as long as they used to. When they reach their end of life, they can start to exhibit odd symptoms while charging such as swelling, heat, and a rotten egg smell.

When you notice this happening, the battery is essentially boiling on the inside. Due to the sulfuric acid in lead-acid batteries, they begin to off-gas H2S which is flammable, or explosive, and toxic in high enough concentrations. The likelihood of it reaching a dangerous level is low, but never zero, which is why you need to ventilate the battery compartment immediately. Do not touch any electronics or other potential ignition sources until the compartment has had time to ventilate, even turning a switch off can create a small arc with the potential to ignite any built-up gasses.

If your batteries are exhibiting these symptoms you will need to replace them, or at very least remove them, before using your trailer next. We also highly recommend that when you replace the batteries and charge them up for the first time, check the charging voltage that is being applied to the battery. It is incredibly rare for this to happen, but a faulty charger that outputs too high of a voltage could have caused the batteries to overcharge, and could ruin your new batteries as well. This is easy to check with a voltmeter or multimeter by setting it to DCV and checking the voltage across the batteries while the charger is operating.

We recommend upgrading from lead acid batteries to at least AGMs, but preferably lithium batteries. Both of these battery types offer a greater lifespan (more charge cycles), especially lithium batteries. Lithium batteries will also allow a greater depth of discharge which means more usable power while off the grid!