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Discussion Starter · #1 ·
I got this portable battery charger from West Marine to charge the deep cycle / starting batteries (a pair of Walmart-brand 12V cells, model no. "24-DC", 75 Ah each) on my boat. I got it instead of the $10-more-expensive "onboard charger", not knowing that the instructions said that a marine battery must be removed from the boat and charged onshore.

What's the reason for this requirement? I figure if the 6A alternator on my outboard is okay to use on the boat, why not a 6A charger? Is it because there's a power cable running from shore or something?

So the first time I used it, I lugged the batteries to shore. Egads, were they heavier than I expected. Also they are not stowed in super-accessible locations (like, under the v-berth). I really really want to just attach the alligator clamps to the terminals in the engine compartment. Will Ι create any micro black holes if I do this?
 

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I would say the danger would be from leaving it in a gasoline powered boats engine compartment WHICH would require and ignition safe charge

If your just charging a battery on a boat i am not seeing the danger
 

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Adam-

Which battery charger did you get? Is it an intelligent three-stage charger? If not, it will probably likely fry your batteries...

Most portable battery chargers aren't recommended for use on a boat as they can be a fire hazard. The alligator clips can come loose unexpectedly, and that can be bad. Also, it requires you to open the battery box to have the clips attach to the battery posts, and if you leave the battery box open and something falls across the posts...bad things can happen. :)

If you want to charge the batteries on the boat, you're much better off hardwiring in a proper marine battery charger into the system.
 

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Battery Caharging on board

In addition to the dangers of heavier than air volotile gases such as gasoline vapour and propane; a battery, while being charged also generates a small amount of equally explosive hydrogen gas (think Hindenberg) any of these volitile gases could be ignited by a connect / disconnect spark. If you must charge on board, ensure adequate ventilation to remove all of these gases (think bilge blower) prior to connection or disconnection. Also to limit the possibility of sparking near the battery, make charger leads fast to battery terminals then plug it in at farthest reach of it's power cord. This should eliminate sparking at the battery (assuming the red is to + ,black is to - terminals).
 

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Adam-

Which battery charger did you get? Is it an intelligent three-stage charger? If not, it will probably likely fry your batteries...
I'm not understanding why a regular old battery charger is going to "fry" my batteries. I've charged car batteries all the time and haven't fried anything. I've also charged the boat batteries with the same result. A battery is a battery. If you're not permanently hooking up the charger for long-term constant use I don't see the problem. I think this guy is just charging up as needed.
 

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Sander-

An older style battery charger will not have bulk, absorption and float stages... and as such will generally run at a higher voltage than the battery requires when it is nearly fully charged... and doing so generates excess heat and boils off electrolyte in the case of wet-cells, and just fries the gel in gel cells and AGMs.. :) If he leaves an old-style battery charger connected for any significant period of time... which is necessary to get the batteries up to 100%, he runs a much higher risk of frying them if it isn't a smart charger.
 

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I'm not understanding why a regular old battery charger is going to "fry" my batteries. I've charged car batteries all the time and haven't fried anything. I've also charged the boat batteries with the same result. A battery is a battery. If you're not permanently hooking up the charger for long-term constant use I don't see the problem. I think this guy is just charging up as needed.
Basic, cheap battery chargers generally charge at only 14.4 - 14.6 volts regardless of the acceptance rate of the battery being charged.

A "smart" charger will charge at, depending upon the battery type setting, 14+ for the bulk phase, 13.8 for the absorption phase and 13.2-13.4 for the float phase thus causing no damage to the batteries.
 

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I think most of the replys assume you will attach the charger and leave it connected for the winter. If so, they are correct. You need a smart charger that will not overcharge the batteries.

If the intent is to periodically top off the batteries by attaching the charger for a couple of hours, then I see no problem. I use this technique when my boat is on the hard for the winter.
 

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HerbDB-

If you're using a "dumb" charger to top off the batteries, you should check the water level more often than if you're using a smart charger.
 

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I got my batteries through last winter on the hard using an old automotive charger. I might have had it plugged in for 5 or 6 hours every few weeks or so. Didn't notice any more frying than they already appeared to be :) I only used the charger while I was there doing work or hanging with the boat, never left it running unattended.
 

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The Guest Charge Pro that Tommays pictured above is a portable 3 stage charger. It is extremely useful in that it can be used to charge your batteries over the winter periodically or in Spring when they are removed from your boat. It is also a marine charger that will not fry your batteries if left connected so can be used in the summer.

I purchased one of these in Spring 2000 and have used every year since. I did this in place of the built in Guest charger that was also 6 AMPs and the same price at the time. I would leave the alligator clips connected and plug in the charger when at dock.

As the boat I had at the time did not have 30AMP shore power and had an outboard motor with no alternator this was the main source for recharging the batteries. I would attach one terminal to the back of the battery switch and the other to the ground in the lazarrette and could in that manner charge battery 1, 2 or both according to the setting of the battery selector switch.

I had no problem with this charger hurting the batteries and have left batteries plugged in for weeks at a time both on board the boat and when stored in my garage.

It is a great little charger and I am glad to see it is still available. I would not hesitate to buy it again,

Mike
 

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I would caution against leaving any alligator clip type charges on the boat and unattended. I have personally been witness to a boat next to me burning to the waterline when the charger shorted out and the owner was not aboard.
I don't think there is any problem using short term and while you are on board the boat.
 

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Discussion Starter · #13 ·
Thanks for the responses, folks. The way I've been planning on using this charger (which is indeed of the intelligent three-state variety, delivering 13.5-14.4 volts as necessary) is to top up batteries occasionally as I notice that its voltage has dropped too low. I've always attended closely to the process as I've never been quite sure what to expect. Prior to April of this year, the batteries were alternator-charged but then I swapped in an alternatorless (and pull-start) motor while the old one was under repair.

The boat's wiring is as follows: cables from the two batteries run to a Perko battery selector and thence to a pair of terminals in the engine compartment. What I'd really like to do is hook directly (and temporarily) to the terminals in the outboard engine compartment or, failing that, to run battery cables out of that compartment to someplace free from potential gas buildup (unlikely due to the enormous hole in the transom that the motor sits in) and not fire-prone. In my ignorance of such things, my concern there was that running a charge through the switch or other boat circuitry might be hazardous to that circuitry. The instructions were detailed on how to avoid the risk of spark using leads (basically, establish the final connections as far from the battery as possible).

What I've learned from your replies is twofold:
1) Not a problem to charge onboard if attended and for short periods of time (like a couple of hours).
2) My batteries should be inside boxes.

New questions that have been raised are somewhat more theoretical. I've seen wiring diagrams of, and mikehoyt mentioned, circuit hooked up to one terminal of a voltage source, and thence to ground. I was under the impression that current only flows in closed circuits, so what gives? On the practical side, when charging a battery, what's the difference between clipping on to both terminals, or to just one terminal?
 

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I have used a household lamp timer to turn on and off automotive chargers. As a liveaboard for awhile, I calculated my amp hour usage to calculate how many hours a day to set the on position for. As for maintenance charging, a few hours a day was enough to come back to a fully charged but un- boiled battery bank.
 

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I have a Guest Charge Pro Model 2613. It is only connected to one deep cycle battery right now. The red LED on "Trolling Batteries" is blinking. I have unplugged the unit and stopped using the battery for the time being.

Does anybody know what a blinking red LED means in this situation?

Voltage Reading:

Battery at terminals (charger off) 11.4 V
Charger at terminals (charger on) 11.5 V
 

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I would not leave such a charger unattended.
Hook it up to the batteries if you wish, but stay on board when the charger is active. Spend the night on the boat is the way I do it. If you leave for any reason, just kill the power and pull the leads off. Kill the power first..... don't pull the leads off when the charger is live. I have recollections of neglecting that advice in open air in a workshop (no compartment).... bang! ... and acid spray everywhere.

Hydrogen does not collect in bilges, as it is lighter than air, so reasonable ventilation of the battery compartment and you should be OK. I just leave the cover off it while charging.

Watch the electrolyte level. It tends to drop.
 

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I went through this when I bought my boat. ABYC regulations don't allow alligator clips on board as they can not only pop off but the springs die and then don't clamp at all. Portable chargers are not ignition protected and can ignite the hydrogen gas coming off the battery or other vapours in the bilge as in gasoline fumes.

Buying a good charger means you reduce the odds of the above happening but it also extends the run time on the battery and the life span of the battery.
 

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The West Marine 30A portable is a nicely priced smart charger that I have installed on several occasions where ignition protection is not an issue. 30 amps with a sizeable (1/2") volts / amps display, and front panel charge profile selector is very attractive. Of course, the clips need to be replaced per ABYC.
 

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OK. I solved the problem. The PO was kind of stupid when it came to wiring, which is incredible considering he once had this boat as a totally electric powered vessel (big solar panels, wind generator, no sails, no motor).

Everything was wired direct to the battery terminals.

After about an hour of wiring things to the built in terminals, I disconnected the battery, and put in a new one. Same problem. I went to the 110 receptacle on the boat exterior, and realized that whoever installed it seemed to neglect drainage, and rainwater had collected in it. Ostensibly, there was a short here, because clearing it out solved the problem.
 

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I have my outboard charging wired to the the output of the perco battery switch with a trowling motor plug.

In the days when before installing an onboard charger I just added a male plug from the charger to the to the boat just like it was the outboard.

Charger set outside and by using the battery select switch I could charge one--two--or both.

If you don't remove you motor as I do you might just "T" into these wires.
 
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