Permanent Charger Connection

[Sandy]

I have a house supply of 3 AGMs and a cranking battery of 1000 CCA

My system has a combination rotary switch, but Im trying to keep the systems as independent of each as possible.
I want to charge the start battery by a small solar cell on the hatch cover, and the engine alternator while running. The boat has to travel at least 30 minutes under engine to get out to sea from the present marina, so an hour there and back. And I want to charge the house supply from shore power

Alternative sources will become available in time, the boat is rigged with a solar cell management system and I have some panels, around 400 watt.
I think the engine alternator and start battery can look after themselves.
Intended use short term is cruising probably not exceeding 200 NMiles

What I think I want to know is,
.... is it possible to take a decent charger like a CTek and permanently connect it to the 3 battery house supply?
tia

[kevin barber]

Hi Tia,

I would recommend a hard wired charger such as the PowerMax 45A charger available from Amazon.

https://www.amazon.com/dp/B00F8MC42C/ref=psdc_10967761_t2_B00F8MC440 

I have owned several expensive chargers over the past 14 years, and the Powermax has performed just as well if not better than the $400 variety from West Marine. 

The PowerMax chargers are designed to charge a single bank, and maintain the batteries while you have a load on them, such as a refrigerator.  You could make it charge another bank if you add an ACR automatic charging relay or a combiner.

-Kevin

[Dale Tanski]

How a battery charger performs can mean several things to different people.  One positive rating for a battery charger maybe that it works every time it is required, year in and year out. 

Home chargers like the ones made by Schumacher available at your basic big box store would fall into that criteria.  They are robust little buzz boxes that will charge a dead or weak car battery in a heartbeat. Chances are you may have inherited your fathers old Schumacher charger and it is ready to go on a shelf in the garage at a moments notice.  They work fine but in terms of clean DC power output they are borderline.  The typical Schumacher passes a fair amount of AC power along with that DC charge.  Once in a blue moon to charge a weak battery not a problem.  Everyday in a battery circuit, it is a battery killer.

Step up a notch or two in battery chargers and the filtering circuits on the DC side start to become works of art.  Clean regulated DC becomes the norm.  The better unit you get, the more the charger looks after your batteries needs. No under charging and more importantly no over charging.  Good battery chargers have equalize programs in them to greatly extend the life of your expensive batteries by not months, but in many cases years.

Multi bank chargers have built in outputs for charging many banks of batteries.  The cost of adding isolators to a one output battery charger can become costly.

If you own AGM's you must install a good charger and in this case a good charger means it preforms not for a long time but makes the battery last a long time.  Don't just look at the initial cost of the charger, look at the cost of the connected batteries and the anticipated life cycles you expect to receive from them. 

I talk to my customers all the time about a combination charger/inverter instead of just purchasing a charger.  Often for just a few bucks more you can get clean 120VAC power out of your batteries and then automatically recharge them when you plug into shore power. 

Think long term, think about the cost of the batteries and do your homework.  If you would like some help just drop us a note and we will assist you.

Dale Tanski
Obersheimers 

[Dale Tanski]

Bob,
Because your house batteries are connected in parallel, it doesn't matter where you connect your charger, all three batteries will charge to the same level. Because all three batteries are interconnected, installing three separate battery chargers, one to each battery is not the way to go.  The three chargers will sit there and fight between each other to see which one is going to charge the batteries. Who ever gave you that advice, that should be their last bit of advice taken at least on electric systems.

As for your house battery system, don't over complicate it.  The house batteries supply power to your 12 volt devices. If you run short of power away from the dock, you do not have enough battery capacity. If that is the case, add more batteries.  When you plug back into shore power a popular sized charger should be sized to  recoup your batteries needs in 24 hours or so. The slower you charge your batteries the better (cooler) as long as you put in a full charge before you shove off again.  It is also advisable to allow your batteries to cool room temperature after charging before you start to discharge them again. 

As far as solar and wind, each of those systems just plug and play into your battery system.  Each will have a charge controller that independently adjusts the charge rate as required.  Don't worry about them just plug and let them do their thing.

As I recall, CETK battery chargers do not make large capacity chargers. I think 25 amps was one of their biggest.  If you have 3 house batteries each with a capacity 200 amp hours for a total of 600 amp hours and you discharge them by 35% you will need to replace 210 amp hours.  If you had a charger that put out 25 amps it would theoretically take 8.4 hours to recharge. In reality, the charge rate is variable and the last amps put in are at a much slower rate. I would guess to top off the 210 amps using a smart charger with a 25 amp output it will take over 20 plus hours.  If there is equipment running on board while all of this is happening, (refrigeration, lighting, fans) the charger will have to supply that running equipment and charge at the same time which means it will take even longer to recharge your batteries. 

I am not a big fan of offshore equipment one relies on day in and day out.  If you have a problem with it parts and repair maybe a long way away. I have a customer that owns an Oyster 53. Every item aboard is an offshore brand except the gen set.  He is currently waiting for parts for his water maker from France - month #3. 

If I were buying a charger or Inverter/charger for my boat, my first choice would be a Xantrex.

Dale

[PeteW]

I can honestly say that everything I believed about charging batteries went out the window with the introduction of AGM batteries. Charging AGM batteries is not so much about current but rather voltage. Beyond the initial high current bulk charge period the long term survival of your AGM batteries requires that all of your charging circuits maintain a proper float voltage.

Float voltage for AGMs is in the range of 13.4 - 13.8 VDC. This is a specification that must adhered to by the Charger/Inverter, the Solar Charge Controller and the Alternator.

So if you have AGMs and run an old style one terminal alternator that puts out 14.5 volts your AGMs will be ruined in no time flat. Used to be you could gas a flooded battery motor cruising all day at 14.5 VDC and simply add water as needed. Gas an AGM and it will be ruined.

I've learned this lesson the hard way. I now have programmable smart everything in my arsenal of charging gear. The Xantrex charger/inverter is easily programmed to AGM voltage via the remote panel. That something I recommend getting. The MPPT Charge controller allows one to set the float voltage in .1V increments. Monitor your charger float voltage and make sure its in the safe range. I set the Solar charge controller to float to the same level.

I recently installed the Gasser Smart Charge One Alternator Regulator. It can be set for AGM and if you don't want to cook your batteries when you motor out of the harbor you can switch it to manual float mode. Keeps you from overcharging your expensive AGMs unnecessarily.

With all the float levels set to the same proper voltage for AGM's there is no problem with running the solar while the engine is running. One system may supply more current than the other depending on how close the float levels are set.