Battery Alternate

[jibes138]

Is it acceptable practice to run all your 12 volt stuff on the boat without batteries installed by using the battery charger? Since the charger is providing a source of say 14 volt DC power can you just connect it to the battery switch. Just wondering if there are any issues with this? I'm thinking the batteries are removed for winter storage and you are working on the boat and want to listen to tunes, or make coffee on the stove and need to actuate the solenoid, lights, etc.

 

[Don S/V ILLusion]

For short periods, this may work for you but there are some cautions:

1. making coffee in a traditional maker can draw significant amps so make sure the charger you choose has a "starting" capacity (vs. "charging" capacity) sufficient to run this load.
2. many auto chargers are simply rectified unflitered AC (i.e., pulsed DC) which some motors don't like and can, especially over time, heat up and burn out the winding - be careful.
3. A regulated 12V power supply with 20A out isn't that hard to come by - many computer power supplies could handle it fine. Be careful not to use a switching power supply.

Some marine chargers, e.g., Xantrex Trucharge 20, 40, etc are designed to be both a charger and a 13V power supply and are popular for those of us who have our refrigeration running 24/7 which is essentially what you want to do omn a small scale.

 

[Ross]

The safest approach would be a little lawn tractor battery clipped into the system and carried back home when you close things up.

 

[sailaway78]

Some chargers

Some chargers need the battery to control the output voltage. I agree with Ross, in using a small tractor battery in the very least. Even a small motorcycle battery should suffice. Even the small battery will help the charger keep a constant voltage.

 

[Ross]

Re: Some chargers

Some of the lawn mower batteries will fit in a child's lunch box. The output from a battery charger is full of the ripples from raw rectified AC power the battery will smooth those out.

 

[Chuckbear]

As Don said, some chargers are designed for this and some not. Don't try to use the ones that are not designed for this. We use the Iota Chargers and they can run the 12 volt system forever with no batteries attached. Chuck

 

[kloudie1]

The Xantrex that I have has a switch on it that allows it to work as a 12V power supply. They warn against doing that without setting the switch.

 

[Ron20324]

The Xantrex manual says the "fixed voltage mode" (13.5 v) may be used as a "power supply or battery eliminator". BUT, it does not say whether a battery needs to be in place, though it sounds like it doesn't.

 

[jibes138]

Forgive my ignorance but...

When the battery charger has the batteries installed and the charger is operating you can run 12V systems on the boat. The charger is either connected at the battery switch or directly to the battery posts (my set up) . So if I draw a schematic it will look like two power supplies connected at the same point. It seems like you are already running your 12V systems on the boat off the charger voltage whether the battery is there or not. What does having the battery there do to the supplied power as compared to not having it? I am only asking this question hypothetically and my tone in this is one of curiosity. Not being an EE (sparky as i call them) electrical systems are my big weakness.

 

[jibes138]

Another question....hijacking my own post....My battery charger is as old as the boat, about 24 years. Should I upgrade to a new one? It works A-OK but I wonder about anything that old and whether the newer units with advanced circuitry and smart charging is worth it?

 

[Ross]

Re: Forgive my ignorance but...

Jibes, If you viewed the output of the battery charger on an oscilloscope you would see a series of half sinewaves with the peaks all in the same direction and valleys that drop to zero. The peak voltage would be about 17 volts. Normally a power supply will have a circuit called a filter, this consists of a large capacitor and an inductor, these smooth the output to create a steady voltage without the hum that could be present in an unfiltered output. The battery will serve the same purpose as the filter

 

[Timo42]

Jibes, a charger that old most likely won't have any voltage regulation and needs the battery, Just get a battery jumper and bring it with you, would work as well as a tractor or motorcycle battery, and has a handle.:dance: It would come in handy for other things too. Running too much voltage through boat systems can cause damage, I started my outboard with the battery switch off the first time after I installed the alternator and zorched my c/d player and I do this stuff for a living.:bang:

 

[Ron20324]

Another question....hijacking my own post....My battery charger is as old as the boat, about 24 years. Should I upgrade to a new one? It works A-OK but I wonder about anything that old and whether the newer units with advanced circuitry and smart charging is worth it?

Jibes, depending on the design of the charger, it takes a "reading" of the battery voltage/current before it caluculates what it's output will be. The lower the battery voltage (to put it simply), the higher the charger output. Every once in a while (maybe just minutes apart- depending on charger design) the charger takes a new reading and would change the charge to the battery. I can actually hear mine doing that cycle. In short, this is how multi-stage chargers work, down until there is only a minimal trickle/maintenance/float charge. SO, if the charger is on and there's no battery, the charger will likely see a "low" battery condition and crank out it's maximum charge (15+ volts) forever.

That said, if your old charger is not a multi-stage one, you might want to be be on the lookout for a new one at a good price. Older ones probably use more AC to perform their job, but unlike a home power-sucking appliance, we're probably not paying for AC by the kilowatt. My neighbor replaced his old charger with massive heat sinks and noise for a TruCharge 20 that's about half the size. A happy camper.. er, boater.

 

[jibes138]

Thanks guys. My old charger hums quite loudly, it is in the engine compartment that is insulated so it is pretty loud. It is a searanger 10A charge with analog gauge that drops the amps down to maybe 1.5 - 2A when the batteries are charged. I'm not worried about saving electricity, my AC bill for the boat is usually about $2.50 a month. The new chargers seem much smaller, higher amperage, LED readouts of status, multi stage charging. on the other hand the unit I have works so is spending the money justified? I have a sears charger at home and it seems a lot more advanced than the one on the boat for way cheaper than these marine units. The marine units probably have conformal coated circuit cards adding a bit of cost.

 

[Stu Jackson]

Battery charging basics

It is a searanger 10A charge with analog gauge that drops the amps down to maybe 1.5 - 2A when the batteries are charged. ...The new chargers seem much smaller, higher amperage, LED readouts of status, multi stage charging. on the other hand the unit I have works so is spending the money justified?...

That's not really the issue. What you have is an OLD single stage constant voltage tapering charger. This charger is KILLING YOUR BATTERIES. The cost of a new charger has an immediate payback 'cuz your expensive batteries will last much longer.

If you haven't already, read more about how all this stuff works, please read these things:

West Marine Advisor on battery charging: What batteries need: http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/Battery-Charging.htm

Ample Power Primer, download it from the Tech tab at www.amplepower.com

First thing I did when we bought our (used) boat in 1998 was ditch that old charger.

 

[jibes138]

OK I am convinced I have a good way to spend my 10.00 rebate certificate from West Marine. So what battery charger do you guys recommend? I have two deep cycle batteries and a 1-2-Both switch. I use one of the group 27 batteries (both are lead acid batteries) as a house bank and one for just starting.
I checked Defender and West and find prices and capacities all over the place. The Xantrex units look pretty pricey, and West seems to focus on ProMariner. I'm thinking a 20A ProMariner with dual outputs and multi stage charging? Any recoomendations out there?

 

[Dan Johnson]

Jibes...

I run a Guest dual battery smart charger on my H34. It puts out 5 amp for the starter battery and 10 amps for the house battery. It is a three stage charger and allows you to "float" your 12 volt DC use while at the dock off it. Requires its own dedicated AC line off the breaker panel. This model is no longer in either of the two marine catalogs you mentioned.