Here's a great 20 Amp battery charger/maintainer that can be left on indefinitely. It's internal circuitry monitors charging voltage and maintains a safe voltage.

IMHO, the Guest Marine Model 2620 is an excellent 24v choice for maintaining your batteries. It will not boil or overcharge your battery and has a 20 amp capacity (10 amps per battery).

I've been using mine for 4 years and my Concorde batteries are still quite healthy.

A good choice for doing gear swings or when at the avionics shop or in cold weather climates for that extra "edge" in cranking power!

Here is the latest model style available for $165:

Unit comes complete with pre-wired 6-foot AC cord and 2 6-foot DC outputs with ring terminals. Waterproof, fully-encapsulated electronics. Lifetime warranty against internal water damage.

• Components are completely sealed in durable, corrosion-proof, waterproof thermal potting compound.
• Full 3-stage charging for fast, full charging and maintenance.
• Potted components are fully impact protected.
• Shockproof and vibration-proof.
• Built-in electronic overload protection, with automatic reset.
• Reverse polarity and ignition protected.
• LEDs indicate state of charge.
• "Smart" technology can be left on without harmful effects to battery.
• All models may be used for storage/maintenance.
• Thermal protection for extreme ambient temperatures.
• Models for 12, 24 or 36 volt systems.
• For flooded or gel cell batteries
• 2 year limited warranty

Download the Guest Marine Catalog HERE