Proper method to charge marine battery

I've checked several threads, but didn't come up with the black & white answer I wanted. I've seen several that you remove the battery from the boat, but I keep the boat & trailer in the garage, easy access to the battery. I would prefer to just hook the battery charger to the + & - posts and walk away. I have a 115hp mercury, electric start. Is it possible that I may damage something in the motor by charging the battery this way?
Should I isolate the battery from everything else before charging?

Re: Proper method to charge marine battery

It's best to isolate the battery for storage but just get a "smart" type charger, hook it up and forget about it. If the batt is a flooded cell type check the water level every week or two until you see if any cooks off. If charging GEL cells make sure it doesn't charge at over 14.1V because high voltage eats them.

Re: Proper method to charge marine battery

HONKER1 said:

I've checked several threads, but didn't come up with the black & white answer I wanted. I've seen several that you remove the battery from the boat, but I keep the boat & trailer in the garage, easy access to the battery. I would prefer to just hook the battery charger to the + & - posts and walk away. I have a 115hp mercury, electric start. Is it possible that I may damage something in the motor by charging the battery this way?
Should I isolate the battery from everything else before charging?

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hello,

do u have the oe service manual? in mine for my evinrude, it clearly states to remove the + connection to the batt before charging.

from reading iboats, i gathered best to disc batt before charging. so i discd the - grnd side. but while studying my service manual, i noted the specific advice. so now both sides are off. should be safe now... lol~

in future i will remove + side. your service manual may have specific advice. if it was mine, if in the dark or uncertain,. remove both terminals. not a big thing to do, but a blown electronic item can be.

a batt will charge best at 80F.

Re: Proper method to charge marine battery

I've heard rumors of electrical components damaged by failing to disconnect the cranking battery before charging, it's always "some other guy's friend's dad's boss's son" or something.....and the same people say jump-starting your motor can damage it too. I've done both occasionally to mine with never a problem, don't require it regularly (I boat often enough to not have to recharge the cranking batt).

I'm no electrical engineer, but I don't see how a properly functioning charger can hurt your motor.

Isolating for storage is just good practice, apart from the charging question.

Re: Proper method to charge marine battery

Marine batteries are charged every time you start the engine and that doesn't damage anything so in my view there is no reason to disconnect anything to charge them with a separate charger. I have a smart charger on my boat and its plugged in continually all winter. Same for my last boat. Leave the battery hatch open to provide some air circulation. I would suspect you create more potential for problems by not getting battery terminals tight after having removed them. Running the engine (if it does start) and having the connection loosen up will indeed damage the charging system.

Re: Proper method to charge marine battery

jtexas said:

I'm no electrical engineer, but I don't see how a properly functioning charger can hurt your motor.

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hello,

a properly functioning charger won't hurt ur motor, but it can hurt ur electronics, etc. if and when... the user might switch polarities when he hooks it up.

i agree with u, it shouldn't. but there are enuff posts and cautions here on iboats about polarity issues, that for me at least, i will disc my batt's + side before charging. i dont disc on other applications, but i will on my boat.

sorta like spark plugs. the 'mechanic' should know how to install them if he is going to do so. no doubt loose connections at the batt post can cause problems, but if the 'mechanic' can take it off, then he should be responsible enuff to replace it correctly.

probably will be like many engine issues. a dif thot from every mechanic.

regards
lakester

Re: Proper method to charge marine battery

I feel just as likely to damage something by disconnecting then hooking up wrong. Seen it many times here on I Boats. Hooked up backwards blows lots of motor and electronics.

Leave it connected and ONLY use a smart charger or good battery maintaner, or on board charger. Some trickle charges can continue to charge with no voltage regulator at all and reach 18 to 20 volts. It destroys the battery and any electronics that are not completely switched off. Things like a radio with a hot wire to maintain the clock and memory.

On board chargers great as hooked up right one time then forget it. Just plug it in. You smart charger or battery maintainer install a keyed plug like for your trolling motor so it can not be connected wrong then just plug it in and turn it on.

Re: Proper method to charge marine battery

It doesn't hurt a thing, it can't. Everything is only 12 volts. Electronics have voltage regulators on them which will keep the voltage at the correct amount needed for each item. My 28hp outboard charges at a higher voltage when underway than my charger does, so no way can it hurt it.

Just don't start the outboard and have it charging at the same time, or else you'll cook your rectifier. Don't ask me how I know....

Re: Proper method to charge marine battery

Boatist said:

Leave it connected and ONLY use a smart charger or good battery maintaner, or on board charger. Some trickle charges can continue to charge with no voltage regulator at all and reach 18 to 20 volts. It destroys the battery and any electronics that are not completely switched off. Things like a radio with a hot wire to maintain the clock and memory.

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hello,

i dint know that, but no doubt it is true. i was detained out of town an extra day. i had left a trickle charger on before i left and forgot to disc.

so when i got home i put multimeter on it. read 15.2 volts...

bat was solo, nothing connected. now reads 14.0 volts....

i will soon see how it cranks. it is not for my o/b.

regards

lakester

Re: Proper method to charge marine battery

I am an electronics eng and I can tell you that a regulated charger, or 'smart charger' will not hurt the system if you leave the battery leads connected....

I do it all the time with my car. I work away, sometimes for up to 3 months. If I leave the car the battery is as flat as the proverbial when I get home. I checked the system and with nothing on and all the doors closed it still sucks 170mA. I have a very dumb, unregulated trickle charger, and a mains time clock. I plug the charger into the timer, which is set to run for 1.5 hours every 12. I put the charger on the intake manifold, connect the leads to the primary battery, close the hood and walk away. When I get home, I pull the charger off and drive the car around until I'm ready to go away again....

Sometimes I forget to turn off the isolator in the boat and one of the batteries drops a bit (not when I'm away. I double triple check everything before I go) so I just throw the trickler on for a couple of days.

I have never disconnected leads, never will and don't see a need for it....

As for leaving a charger connected when you start the engine... done that too... no problems. Waterinthefuel, I suspect you had something else amiss at the time. If the voltage from the charger was higher than the engine output, then the diodes would be reverse biased and would not conduct. If the output voltage of the engine was higher, then the charger may have sucked the extra electrons (just like a flat battery does), but the output current of the engine charging coils is way lower than the rectifier rating (typically the rectifier is rated at 25 amps and the output of the engine alternator is about 9 amps).

Chris.........

If anyone disagrees with what I have said, please explain the difference between having a 14.2 volt charger (voltage source) on the battery leads and having a 13.2 volt battery (also a voltage source) on those same battery leads!

The reason the service manuals tell you to disconnect one or both leads is CYA (not yours, theirs), nothing more....

Re: Proper method to charge marine battery

Chris:

I'm so grateful that there are people in this world that are sufficiently educated in their field to become an electrical engineer.......that way, I don't have to burn up MY brain cells trying to figure out that stuff! Believe me, I've tried!

Re: Proper method to charge marine battery

The way I do it!
When in storage ,On my work bench,attached to a 12V auto charger,"Pep Boys" $39.00.
When on the boat-Remove the + termimal & charge .

No problem in many years...

Re: Proper method to charge marine battery

achris said:

I am an electronics eng and I can tell you

If anyone disagrees with what I have said, please explain

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hello,

i wont disagree with you. u prob left out more than i will ever know... ha~

but i would like to know what 170mA is? i assume 170 milliamps? how does that relate to real world?

my multimeter has uA/mA? what is that used for and means?

also 20A. when would i use that?

i thot i was pretty good with 12v elec systems. wired many vehicles from scratch, but have to admit... my boating electrics mgt has been bumped up a notch or two as to batt management with iboats advice, etc. i never kept up on things as to what is the batts volts? i ck boat batt all the time now... and put charger on it to keep up near 13.5v.

ah heck! i even got it out and cked all my tv/stero etc remotes tonite and dumped the 1.113v 1.5s and put in the 1.4s and the 1.586v ones... love those LED #s...

and when would i use frequency as to my multimeter? an %?

i got temp down ok, LOL

regards,

lakester

Re: Proper method to charge marine battery

170ma is as you suggest 170 milliamps or to put another way .17 amps. So 170ma or .17 amps is a very small charge, less than 1/5 of an amp.

Your meter the UA stands for micro amps and the MA for miliamps.

A micro amp is 1/1,000,000 of a amp so it takes 1,000.000 (1 million) Mivro amps to equal one amp.

A milliamp is 1/1000 of a amp so it takes 1000 milliamps to equal one amp.

These two scales would be used to measure very low currents. An example would be you are installing a LED indicator light and it suppose to run on 20 milliamps. You would put the meter in serries with the LED to make sure you have the correct current flow and adjust the size of you current limiting resistor. Too many milliamps and the LED will not last long, too few and the LED will be dim. Many Led will have a chart and and tell you the proper resistor for 12 volts or 120 volts.

Your 20 A is another current scale and it good to measue up to 20 amps. Any time using a amp meter the meter need to be in serries with the load and you must use correct polarity.

Achris
I agree with all that you said but important to note a dump Trickle charger may charge at 2 amps or so and usually not regulated at all. If Put on for the winter and left charging voltages can go much higher then the 13.8 to 14.4 safe charging voltages. I have seen some that will reach 20 volts and kill the battery. Burn out light if turned on and damage some electronics. That why I always recommend some form of a smart charger.

Charger labled Smart, Automatic, Maintainer, and ON Board all that I have seen do have voltage regulators and very unlikely to over charge. With a new charger I would check if I was going to leave on for the winter.

My batteries are charge by a 65 amp alternator on my I/O thru a battery isolator. Still when I get home after a trip I put the charger on and fully charge the batteries. After we pull the Boat out of the waterwe always use some battery. Doing thing like raising the out drive and trim tabs and on days with a lot of wind and spray may hit the bilge pump to make sure dry. also usually leave the VHF Radio on and GPS on until done tieing down.

My routine is when I get home I pulg the charger in to a keyed plug on the front of the bow. Then Unload the gear, clean the Fish and cover the boat. Then check the charger and make sure below 1/2 amp and disconnect. In summer will charge one time a month if we do not take the boat out and in winter every 2 mounth.

Re: Proper method to charge marine battery

not to dispute achris's experience, I'm disinclined to leave a trickle charge on for more than overnight - no doubt under ideal conditions it works fine, but I tend to believe it can overcharge a battery. "maintain mode" is preferable - turns off & on as needed. not the same as "auto shut-off", but auto shut-off is a good feature to have on a charger.

found a portable bench charger for about $40 at Sam's, with 2/10/20A charge automatic maintain mode, 75A cranking, wet/gel/deepcycle, and a desulfate pulse mode. tried the desulfater on a couple batteries didn't help either one.

boatist has a good routine - I do much the same with my trolling battery and check the cranking batt voltage every couple months or so, it never shows less than 100% (12.6V) after I get home.

I also check my batteries with a hydrometer couple times a year, then more frequently when the cranking batt starts showing signs of wear - that way I always manage to wring as much life as possible without ever getting stranded.

don't forget to check the water - low water is the chief cause of premature battery failure. that and storage at less than 100% charge. especially in hot weather. battery self-discharge rates vary with temperature.

the ultimate source of 12V battery knowlege: http://www.batteryfaq.org/

Re: Proper method to charge marine battery

Boatist said:

Achris
I agree with all that you said but important to note a dump Trickle charger may charge at 2 amps or so and usually not regulated at all. If Put on for the winter and left charging voltages can go much higher then the 13.8 to 14.4 safe charging voltages. I have seen some that will reach 20 volts and kill the battery. Burn out light if turned on and damage some electronics. That why I always recommend some form of a smart charger.....

Click to expand...

Totally agree with you... and that's why....

achris said:

and a mains time clock. I plug the charger into the timer, which is set to run for 1.5 hours every 12.

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I have installed an ammeter on my very dumb, trickler charger and it puts out a whole 1 amp.

Chris.........

Re: Proper method to charge marine battery

jtexas said:

not to dispute achris's experience, I'm disinclined to leave a trickle charge on for more than overnight - no doubt under ideal conditions it works fine, but I tend to believe it can overcharge a battery.

boatist has a good routine - I do much the same with my trolling battery and check the cranking batt voltage every couple months or so, it never shows less than 100% (12.6V) after I get home.

Click to expand...

I want to make you aware that no smart charger can overcharge the battery. They have small microprocessors in them that charge the batteries and constantly monitor everything.

And as far as battery voltage is concerned, it really means nothing. A battery can be showing 12.5 volts and as soon as any load is put on it, it drops to dangerous levels. I don't bother checking battery voltage as it is a completely irrelevant number.

Re: Proper method to charge marine battery

Lakester said:

....but i would like to know what 170mA is? i assume 170 milliamps? how does that relate to real world?

my multimeter has uA/mA? what is that used for and means?

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This is the cornerstone of the metric system... Everything is based on multiples or divisions of 10.

If you are referring to current, then the base unit is the Ampere (amp).

The divisions used are:
Milli (m) 1/1,000
Micro (u) 1/1,000,000
Nano 1/1,000,000,000
Pico (p) 1/1,000,000,000,000

Multiples go the other way:
Deca (D) x10
Kilo (K) x1,000
Mega (M) x1,000,000
Giga (G) x1,000,000,000
Tera (T) x1,000,000,000,000

If you look closely you'll notice that anything in the division uses a lowercase letter and everything in the multiple use has an upper case letter. You'll also notice that the multiples are also used in the computer jargon world...

Lakester said:

....and when would i use frequency as to my multimeter? an %?...

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You would use the frequency range when you wanted to find out how often a signal is alternating. Measured in Hertz (Hz). And the divisions and multiples still apply. Your computer will probably be running at about 2MHz. That means the clock for the CPU is cycling 2 million times each second!

Hope this helps you some....

Chris................

Re: Proper method to charge marine battery

My 1.5A shop trickle charger measures 21V open circuit and will easily reach 15 volts when connected to a battery. Needless to say, it is used only to top off my lawn tractor battery that I use for power in my ice fishing shelter and to charge my lithium-poly batteries for my R/C airplane (ski equipped I might add). Just a note about long term storage with vehicles, if it has a radio, 170ma current draw is very normal and will run down a battery. The current draw is from the engine management ECU and the radio station memory.

Re: Proper method to charge marine battery

Silvertip said:

...Just a note about long term storage with vehicles, if it has a radio, 170ma current draw is very normal and will run down a battery...

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Radio memory current is in the order of 2mA. I just put a new radio in the boat and was concerned about draw, so I measured it. ECUs and other extraneous junk, definitely! Vehicles of today are so full of unnecessary rubbish that it's scary! Why on earth do we need a computer to control the windscreen wipers??? I remember the days when we had a ON/OFF switch... No problem with current draw on that puppy!!!

Have a nice day

Chris..............