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ContinuousWave: Small Boat Electrical
Battery: Excessive Water Loss
|Author||Topic: Battery: Excessive Water Loss|
posted 09-09-2005 09:09 AM ET (US)
I have an 2005 170 MONTAUK with 115-EFI engine. I have only one battery onboard so I watch it VERY closely to make sure I don't get stranded. The boat came with an Interstate 595-CCA marine battery and I have been using it without incident for 13 months now of weekly all-day outings. I check the battery water once a month and have had to add distilled water several times. I buy the pint bottles of battery water from NAPA and have had to add perhaps 4-5 of these pint bottles in the past year to keep the water level up above the plates. This does not seem normal to me and I think this is too much water to have to add in a battery over only a 1-year period.
When I am out on the water trolling all day at 2,500- to 2,700-RPM, the regulator is charging in the range of 14.4 to 14.8 volts. I am able to monitor this via my chartplotter. While this seems high, it is within factory specs and is NOT overcharging according to my Merc factory manual. For my engine, the "max" is 14.9 volts.
What the heck is happening here? It seems like I am adding quite a lot of water for a battery (and boat) that are only 13 months old (I have 210 hours on the boat with this original battery). My year-round climate is mid-80's and around 85-90% humidity if that factors in here in any way.
Also, I think I am stuck with Interstate as a brand as they seem to be the only brand of marine battery available on the island (Guam).
I plan on having the battery load-tested once a year to make sure its kept in good shape but do I need to skip that step and get a new battery to be safe given the above symptoms? Its almost as though the battery water is being "cooked" out at a higher than normal rate.
posted 09-09-2005 11:13 AM ET (US)
How many hours?
FWIW, I have to add a little water about every six months, but
I'm running about 100 hours a year.
posted 09-09-2005 11:14 AM ET (US)
Never mind, I missed the 210 hours.
posted 09-09-2005 06:25 PM ET (US)
Using only one battery, which is what I do also, I would strongly recommend a combination dual cycle starting/deep cycle battery. Any brand should suffice, and I would assume Interstate makes one. Starting only batteries are much too suseptible to being run down when fishing under heavy electronic loads. The combo batteries are specifically designed to accomodate house loads without damage in these charging/discharging situations.
posted 09-09-2005 09:09 PM ET (US)
Congratulations on all that time spent boating. My 1990 boat only has 190 hours on her! I better get off the computer and do some boating to catch up.
If you only have one battery, its primary purpose is to start the motor, so I would choose a battery designed primarily for starting.
I think you are running the boat in rather warm temperatures, and with the constant charging you get from the engine, you are probably boiling out some water from the battery. There is probably no way around this, given the use pattern of your boat. You are just putting too much charging into the battery, and once it has reached full-charge its next step is to boil out some water. The higher temperatures probably help the water evaporate, too.
One way to burn off some of that extra charging current would be to turn on a little more electrical load, like the navigation lamps. They might absorb some of that extra current.
Can you pull start your motor? If not, I'd get a second battery!
posted 09-10-2005 08:36 AM ET (US)
Thank you for the feedback. I have no idea what type of marine battery this is (starting or combination) but I guess I should take it out and read the label more closely. I know it says Interstate deep cycle marine but that is just what I remember. The tip for adding some additional "load" by switching on some devices is a great idea. The easiest way for me is to increase the pulse power and pulse length a bit on the 600 watt sonar. If that ends up being too much, I'll try something quite a bit lower like nav lights.
Jim, that is an excellent question on pull starting my motor and I have no idea. Come to think of it, I believe
I also wonder if I am losing a bit of battery through the vent caps when this small boat is negotiating large swells and rough sea conditions.
posted 09-10-2005 09:19 AM ET (US)
If your battery is in a battery box, you should be able to see if there is any water (or acid) in the bottom of the box that might have come from sloshing around in heavy seas.
The Mercury 115-EFI motor is rated at 25-Amps of alternator current. I don't know if this is the net charging current or not. In any case, it is not a huge output. I suspect it is probably an old-style under-flywheel coil and magnet type of alternator, and these are not renown for having fabulous output. Also, I think that the regulator on that motor may just be a simple shunt regulator with a Zener diode and heat sink. These are often set rather high, as you mention 14.9-volts being the maximum output. Hours of charging at 14.9 volts will probably boil out some electrolyte from your battery.
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