With battery banks getting larger & larger and battery technology becoming more and more expensive a quality battery charger is not the place you want to skimp on features or quality.
For this article I am installing a Sterling ProCharge Ultra . When selecting a marine battery charger there are certain things I believe to be important, and the sterling ProCharge Ultra hits most all of these buttons.
The ProCharge Ultra is not the only good quality charger out there, but there really are not as many as folks assume there are. Sure some old school ferroresonant chargers will last 30 years, due to very simple technology, but they'll murder 27 sets of batteries in the process. A compromise needs to blend healthy charging characteristics with a respectable service life. Some three-choice (AGM, GEL,Flooded) dip-switch battery chargers may do a good job charging one particular brand of battery but they'll fail to charge properly for other batteries on the market.
When buying a quality marine battery charger, one that will be HEALTHY for your batteries, it's up to you to do your homework. Beware that many charger makers do not even give you enough information to make an educated and informed decision this is because the "smart" charging industry is pretty full of snake oil & BS.
UL Marine / ABYC Compliant:
The charger should be built to ABYC / UL 1236 standards. These standards are specific to the marine industry, though I think the emergency market such as rescue and ambulance also use UL 1236. This standard is created around safety and isolation of AC & DC. A UL 1236 charger has undergone a 1500 volt test to ensure there is adequate AC/DC isolation inside the charger. 1500 VOLTS !!!!! While there are some non-marine chargers that can do quite well in the marine environment the UL 1236 or "ABYC" compliant statement or logo will be a good guide and won't leave you guessing if the charger you chose can handle the environment or is well suited to a marine application.
This quote was published in an ABYC referenced article and written by corrosion survey specialist Stanley Konz.
"WHAT WE FOUND
Ø Burnt and corroded shore power cords
Ø Improper AC Neutral to DC negative connections
Ø Reversed battery cables
Ø The failure of an automatic inverter ground switch
Ø Oversized breakers
Ø A BATTERY CHARGER INPUTTING 110AC INTO THE BATTERIES
Ø Wire nuts used
Ø Undersized wire
Ø Hard (house type) untinned wires"
A BATTERY CHARGER INPUTTING 110AC INTO THE BATTERIES......OUCH! It is critical you choose a well built charger and wire it properly. If you don't fully understand the above points made by Mr. Konz you should consider consulting a qualified marine electrical systems specialist for this install.
That article goes onto say that nearly 1/3 of the boats in that marina were leaking AC current directly into the water! DIY wiring mistakes, even by those meaning well, can often be a major player in these "leaks". Please be careful and follow acceptable safety guidelines.
What makes a charger Smart?
World Voltage Input:
The charger should work on varying input voltages and not suffer from output limiting. This Sterling ProCharge Ultra is a "World Voltage" power factor corrected charger and will work on any voltage from 90-260 volts/ 40-80 hz and still supply 100% of its rated output. You can plug this charger in to voltages in just about all countries on the planet. If you're a cruiser this is a critically important feature. If you have a US voltage charger you're stuck charging at US voltage/hz docks.. There are MANY docks out there with voltage drop issues and even at 90 volts AC, with the Sterling ProCharge Ultra, you're still getting the full rated charger output.
All marine battery chargers should utilize on-battery temperature sensing and ideally come with the sensor as standard equipment, not as an "extra". Trojan, Deka/East Penn, Lifeline, Odyssey, Optima, Rolls, Crown, Exide, Firefly, Northstar, Prevailer, Gel-Tech, Full River, US Battery, Interstate etc. all require temp compensated charging of their batteries. How many so called "smart" chargers do you see that actually include or offer an on-battery temp sensor? If a marine charger does not at least offer on battery temp compensation as an option then walk away.
The charger should have a good warranty and the manufacturer should have a good reputation for customer service/support. The Sterling ProCharge Ultra carries a 5 year warranty and the Support at Sterling Power USA has been outstanding in backing them up.
Multiple Charge Profiles & Custom Charge Profile:
The charger should include multiple options for charging voltages/programs. It should also include the ability to create a custom program for any battery you choose. Chargers with two or three dip-switches and the typical AGM, GEL & Flooded settings are NOT smart chargers.
The charger should be multi-stage with at least Bulk, Absorption, Float. I prefer them to also include a Conditioning/Equalizing program.
Smart Charging Algorithms:
Far too many so called "smart" chargers utilize what I refer to as simple egg-timer algorithms. Egg-timers are anything but "smart". Egg-timer chargers work off of a very basic timer that begins when the charger either boots up or attains absorption voltage. Some offer as little as 1 hour at absorption voltage and this can range up to 2 hours and occasionally as much as 4 hours. Once the time clock runs out the charger drops to float regardless of the SOC of the battery bank. A few chargers even start the egg-timer from the point where the charger boots up. regardless of SOC or attained voltage or how long it spent at absorption voltage the charger drops to float based on the egg-timer running out. Egg-timer charging is an absolutely pathetic method for charging deeply cycled batteries, especially when combined with partial state of charge use, but it is very cheap to produce then slap a "smart" label on.
The absorption voltage duration is an absolutely critical aspect of charging your batteries and keeping them healthy. Inadequate time spent at absorption voltage, 14.1V for gel to 15.0V for some others, will lead to chronic under-charging and battery murdering sulfation. A considerably smarter method, to determine the absorption duration, is to look at multiple parameters and then calculate the absorption time on the fly and for each cycle. A good smart charger may often measure the time spent in bulk charging, percentage of power supply being utilized, current decline vs. time during absorption voltage etc. in order to determine an adequate and healthy absorption cycle duration. Ideally you do not want your bank dropping to float before it is 98%-100% full. Sadly most "smart" chargers grossly miss this mark. When we use smarter charging logic we get better absorption duration's that are better tailored to our bank.
The charger should work well with marine generators. Many chargers, especially non-marine units, do not work well with a marine generator as the generators do not always output clean power due to variations in RPM etc....
Any charger that does not offer an equalization feature for flooded or Lifeline AGM batteries is simply not smart.
Re-Absorbtion Cyclic Feature:
For charging wet cell batteries I prefer a charger that will revert to an absorption voltage periodically when left in standby/float mode. This programmed absorption voltage cycle helps to minimize electrolyte stratification. Float current alone is often not enough to prevent the electrolyte from stratifying. An absorption voltage, run periodically for a short duration, very often prevents the effects of stratification.
Stratification is when the acid sinks to the bottom of the battery case and the water rises to the top of the battery case. It creates uneven plate wear and can lead to premature death of the battery. A cyclic absorption voltage will get the electrolyte moving again and minimize any effects of stratification. Not all chargers offer this very useful "cyclic absorption" feature.