Onboard Battery Charger Understanding

[wright74012]

I recently boat a 25' pontoon. It has three batteries in it and also has a Onboard Battery Charger. Can some one tell me what the Onboard Battery Charger does? If I need to do anything with it? How does it work? The batteries are all tied in to a very complex battery looking Red battery knobs where I can swicth it to power whatever battery I want. I have just been putting the knobs to all and going. Can someone please explain this set up to me?

 

[Fireman431]

Re: Onboard Battery Charger Understanding

If your boat has an onboard battery charger, then there must be a 110v (standard household) plug somewhere also. The idea is that you can plug it in with an extension cord or a shore power stand and the batteries will maintain a full charge whenever the boat isn't being used. It is (more or less) a trickle charger for all 3 batteries when the boat is unattended.

When you're actually using the boat, placing the switch in the 'all' position gets power from all batteries. I would venture a guess that your engine isn't putting out enough power to adequately charge them all if they were low. Generally, people use a switch that is labeled 1, 2, ALL. You can set one of the batteries as a cranking battery (let's use #1). Start the engine with the selector switch on 1 or ALL. With newer model switches, you can start on 1 and then switch it to ALL and while driving, and the engine charges both batteries.

When you've anchored the boat and shut the engine off, switch to 2 (if that's your "house" or deep cycle battery) and run the radio, fish finder, GPS, whatever for the time you're there. If you wind up killing the 2 battery, you can switch back to 1 and you still have a hot starting battery to make sure you get home. Once started, switch to ALL and charge the low battery on the way home. This works even better if you have an automatic charging relay installed. That will tell the supplied power which battery is lowest and needs more charge, but it's not mandatory. If you kill the batteries on the ALL setting, you're dead in the water.

Once back at the dock, plug in the charger and it will top off the batteries prior to the next use. The third battery you have may just be an emergency back up of some sort. We would need to see if it were wired in with the others.

One thing to keep in mind. If you use the on board charger a lot, keep an eye on the fluid level in the batteries.

 

[wright74012]

Re: Onboard Battery Charger Understanding

Thats a great explaination, thanks alot. I think I understand it now. But I have a couple more question to your response. Is there a way to check the voltage on your batteries on that thing? How would you know if you have a bad battery? And if the fluid level needs refilled, what would I fill it with?

 

[Fireman431]

Re: Onboard Battery Charger Understanding

Is there a way to check the voltage on your batteries on that thing?

Do you have a multi meter? They are relatively inexpensive and are a must to have. You can get a cheapy for less than $10. Read the instructions on it's use. It's very handy around the house as it reads hi/low voltage, amperage, ohms, checks continuity, etc. You can test your voltage at the battery terminals (with the selector switch to "OFF"). That will tell you whether or not you have sufficient voltage (look for 12.2-12.6), but to truly test the battery, it has to be under load. This would entail it's ability to start the engine, or at minimum, crank the engine for a short period of time. They also make load testers that you can purchase for less than $50, but you probably really don't need one. Or you can take them to any auto parts store and they will load test them for free.

How would you know if you have a bad battery?

If it won't hold a charge or if it fails the load test. Leaking it's internal fluids out of a gaping hole is also a telltale sign, as is smoke, fire, green clouds of noxious gas, etc....

And if the fluid level needs refilled, what would I fill it with?

A standard marine/auto lead-acid battery contains sulfuric acid as standard fill at initial purchase. That is because sulfuric acid will not destroy lead. To refill any low cells, you would use distilled water. READ THIS: This is not tap water. This is not drinking water. This is not purified water. This is distilled water (no minerals). Fill any low cells to the bottom of the fill port and then charge via trickle charger.

There are other types of batteries (Gel, glass mat), but those usually are sealed so refilling isn't an issue. If your batteries are over 3 years old, think of getting new ones. If they still appear good, then either take your chances or (my preference) is selling them for $25-$40 each on Craigslist to recoup half of your money. A good option, since you have 3 batteries, is to replace one per year. Easy on the wallet and you're assured of having 2 batteries always under full replacement warranty.

 

[wright74012]

Re: Onboard Battery Charger Understanding

Thanks for all your input. Very helpful!