Work-Around for Inverter Charger when batteries dead?

[Jamme]

Apologies in advance if I state the obvious. Boatyards sometimes offer the option to remove batteries and store them in a controlled (?) environment indoors. You can always simply disconnect battery lugs at the source. Obviously this is just a ‘fix’ until you find the culprit draw(s)!
Fair winds.

[Stu Jackson]

How can you learn about this stuff?


Don't listen to anyone who says "...typically..."


Get and confirm the wiring diagram for YOUR boat. Follow each of the wires and learn their purpose. Get the manuals for all of your equipment.


Buy Calder's book.


Depending on how you like to learn, search out more books or use the internet (marinehowto.com is excellent for individual subjects).


Study hard, just like you were back in school.


Good luck.

[Scubaseas]

Sorry I have no experience with Fireflys. If your boat is on the hard I can't imagine a draw big enough to flatten out a what 400AH bank? Unless something got left on. It sounds like one of your cells is dead. But again I have no idea what happens if you completely discharge a carbon foam battery. I know on AGM or Flooded start batteries you can do it maybe twice on the AGM and maybe only once on flooded before you damage the plates and loose pretty much all capacity.

If you're on the hard do you even need the bilge pumps on? Disconnecting everything might be an option?

In addition to Calder's tome and the most excellent Marinehowto site learn how to build a proper diagnostic logic tree. Electrickery is pretty much go from Plus to Minus with something in between and don't let the smoke out of the wire.

[Jweyndling]

I have been in exactly the same situation with a Magnum inverter/charger. All it took was a small amount of power from a car battery jump start device to kick the Magnum into action and then the shore power could take over to re-charge the house battery.

[Redline452]

Originally Posted by Elzaar

Good thought. I wondered if the start battery could be used. Would a basic start battery have enough oomph to raise a 400 amp battery bank up high enough to make the Magnum happy?

Yes, I’ve done exactly this. When the house bank went to 4v (don’t ask) one winter, both the Magnum inverter/charger and the BlueSky solar controller shut down. The Magnum does not connect the internal AC to the shore supply until it has confirmed the voltage is correct, to protect the internal equipment. Just a few moments of ‘bridging’ the start battery brought the house up to 9v when the charger started up and took over.