Electronic – How to recharge a battery with a manual battery charger


What are the best practices for recharging a 12V lead acid battery with a manual recharger.

I have a 12V lead acid battery (7.2AH/20HR MK ES7-12 (PDF)). I've read the advice here on how to check the battery level (I have ~12.2 V under no stress, and when powering the system it still currently reads ~12.2 V on the DMM).

When it starts to run low, I'd like to know how best to recharge the battery. I have a manual battery charger (Schumacher MC-1). I realize the manual part means that I cannot just plug the battery in and walk away. How best to monitor the charge? With what frequency? What likely problems should I be aware of?

Best Answer

Not many issues charging big lead acids. Just hook the sucker up, turn it on, wait a while, test the battery for either loaded voltage or charge current (<0.3A), then disconnect or continue. Some issues I've had with standard sealed lead acids:

  1. Killing the battery separates the water from solute, which can then freeze. This happens if it dies in the cold. It's basically pooched at this point, but there's nothing stopping you from trying to thaw it out and charge it back up. Sometimes they still work!
  2. Don't use the boost function, if there is one, to attempt to charge the battery more quickly than usual. This is strictly for boosting, and will reduce a battery's MTTF. Note that maximum charge current is 2.16A.
  3. Charge it in a ventilated area. I know it's sealed, but I do this anyway, just in case!
  4. Don't put it on a concrete floor -- stick a piece of cardboard or wood under it. This has been proven a myth a dozen times over, but I still do it to keep Murphy at bay.
  5. Don't use too large a maintenance charge. The battery datasheet states 13.5V-13.8V float voltage.

Why did you get a manual charger, anyway? I'd definitely screw that up within a season.

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