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post #1 of 10 Old 01-10-2008 Thread Starter
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Battery question

My sailboat is a 1972 Cal T/4 (24í, fiberglass). The boatís electrical system consists of a 12V battery and the electrical consumers (lights, speed & depth and a VHF) there is no charging system installed on the propulsion system which is an 8 hp outboard gas engine. When I bought the boat (four years ago) I replaced the battery with a new Interstate Marine/RV deep cycle battery. At the same time I also bought a Guest (model 2611 three stage) 10 amp battery charger to recharge the battery from the electrical source at the dock.
My electrical usage is extremely limited. When I sail I have the depth sounder on (minimal draw) and the navigation/position lights go on after dark (probably three times a year) thatís about it. This winter I took the battery out and brought it home to store it. I just checked the voltage and the (12V) battery was reading 8.5 volts; it has not been used in months. The last time I had it on the charger was probably August. I just hooked the battery up to the charger and the charger was indicating that it was delivering a 10 amp charge (LED lights on the charger) and I measured 13.8V at the battery. A half an hour later the charger is delivering something less than 10 amps (LED light out) and I am reading 13.4V at the battery. Here is my question; I seem to remember reading recently here on this forum that if a (12V) battery reads less than 10.5 volts it is ďshotĒ and itís useful life is over is that correct? At what point is this slightly used marine battery finished? It is probably the least used 4 year old 12V marine battery on the planet.
Second question; the Guest model 2611 battery charger ownerís manual states that it will not boil off the electrolytes in lead-acid batteries when left unattended. Does anybody leave these battery chargers on all the time when the boat is at the dock? I see lots of power cords going to unattended boats at our marina. I live in the Pacific Northwest (Seattle area) so we seldom get very cold weather. The salt water never freezes and the larger lakes donít freeze either and it is seldom below freezing (32F/0C). What are these power cords powering? Are they running heaters? Or are they powering up the battery charging systems. Iíll ask one of the owners the next time I see them but in the mean time Iím asking you folks.

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post #2 of 10 Old 01-10-2008
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A lead acid battery left alone will discharge at about 3% per month IIRC. So it's not so surprising that your unused battery is down. Try recharging it overnight. Your battery charger is unlikely to harm the battery when left on, but to save a bit of shore power cost, put a timer switch plug between it and the shore power.

A lot of boats have not only chargers but also dehumidifiers and even heaters running over the winter months.

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post #3 of 10 Old 01-10-2008
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Most of the boats with Shore Power cables running are running the chargers, fridges etc...whatever appliances are hooked in.

As for your battery questions - if it reads 10.4V AFTER it is charged - then you have no holding charge and a dead battery (which will be evident when you try to turn over your motor if it is an inboard.

Typically, if you leave the charger on - as a battery will self discharge left unattended - you'll be ok until the battery just dies. Typical battery life however for a marine battery is only about 2 years however (at least that is the average).

I live in Seattle as well - and as of late we have had freezing temps and that can kill a battery if a charger is not running on it. Marine batteries are not really designed for freezing temps..

I would see if your Guest Charger has a equalize function and reset however...


But - if you are reading 13.4 after charging you should be fine. If after charging it is 10 something or the charger just seems to charge continuously...its time to replace.

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post #4 of 10 Old 01-10-2008
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"It is probably the least used 4 year old 12V marine battery on the planet."

And therein, my friend, lies your problem!

Batteries don't just die. They are murdered, usually by folks who don't know much about them. I don't mean to be critical of you, here. Most people don't know much about batteries.

A lead-acid battery (including flooded, gelled, and AGM types) will deteriorate if it is left in an undercharged state. Damage begins when the battery leaves the factory. Lead-sulfate crystals begin building up on the plates and, unless the battery receives a full charge, will continue to accumulate and will embed themselves in the plates, thereby reducing the battery's ability to accept and maintain full capacity. New batteries -- off the shelf -- can have a very considerable variation in their capacities due to this factor alone.

While there are other factors which contribute to battery deterioration over time (contamination, corrosion, PbSO4 buildup under the plates, running dry, over discharging or charging, etc., etc.), lead-sulfate buildup is by far the #1 culprit. And, it is the result of undercharging or leaving batteries in a less-than-fully-charged state.

As was correctly stated above, flooded batteries have a high self-discharge rate...as much as 3-5% per month. You must keep them fully charged to maintain their capacity. And, occasionally, it is useful to "equalize" them (i.e., to hit them with a charge voltage exceeding 15.5V for a 12V battery) for a few hours and let them gas vigorously. This helps to equalize the charge in each cell and to knock easily removable lead-sulfate crystals off the plates.

If your battery is four years old and has been treated as you say, I'd toss it. Get a new one and treat it right: keep it fully charged. Yes, keep the charger on when at dockside (assuming it's a marine multi-stage charger and that your electrical wiring is up to the job). Check the electrolyte level in each cell frequently, judiciously adding only distilled water when needed to keep the level about 3/8" above the plates.

If you treat your battery well, you should get much more than 2 years out of it. Five years is about right for a flooded battery which has been well cared for. Premium flooded batteries (e.g., the Rolls/Surette line) will give you about twice that much service -- or more -- but they are costly.

Hope this condensed primer helps a bit.

Bill

Last edited by btrayfors; 01-10-2008 at 05:53 PM.
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post #5 of 10 Old 01-10-2008
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I entirely agree with Bill's comments but would like to add some about your charger since that will be what keeps your NEW battery from dying early:

1. Though it is a 3 stage charger it does not go over 14V in bulk charge stage and you should really charge at around 14.5V for maximum reduction of the sulfation Bill describes.
2. It has no EQ cycle capability which means that you have no way to "knock off" sulfation after the fact.

Given your use, it is hard to justify an expensive new charger. You may be better off just leaving the charge plugged in full time and topped up with distilled water as Bill suggest.Given your charging system, I don't think you can expect real long life from your battery...but you can certainly avoid killing it as quickly! (g)

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post #6 of 10 Old 01-10-2008
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I had the same problem as you. I put a SE 400 on my rail and solved the problem.
I bought mine at a auto store called Pep Boys for about $60, same unit. It doesn't need a regulator because of its output. I always have a charged battery now instead of a partially charged battery. Plus, with the small amp draw we use, the panel makes it up as we use it. About a 1/2 amp.

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post #7 of 10 Old 01-10-2008
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I have to disagree with some of the advice given by PPs based on my experience:

My previous boat had a 9.9HP OB with alternator which charged my battery while the engine was running -- about 1 hour each day that I took the boat out, perhaps twice a week from May to October. That was the only charging it got. It was drained by cabin and nav lights, navigation electronics and VHF.

During the winter I removed it from the boat, kept it at home connected to a Guest 3-stage charger. The battery was 7 yrs old when I sold the boat last summer and still alive and healthy.

Before I bought the 3-stage charger I could never keep a battery alive for more than 2 years.

Given the light use the OP makes of his battery, I think it could last forever -- at least, from my experience.

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post #8 of 10 Old 01-10-2008
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I have an outboard with electric start also and it had an alternator for charging. The major difference is Northbeach doesn't have a charging system on his outboard and I ran mine 2 minutes to the bay before the sails went up. The solar panel solved the problem without being hooked up to power and take it off the boat in the winter and connect it to the battery for full winter charge.

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post #9 of 10 Old 01-10-2008
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Something to consider for light, infrquent usage like you have is a portable power pack. About the same cost as a battery, but can be put to other uses. Sears Die Hard

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Last edited by CapnHand; 01-12-2008 at 12:43 AM.
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post #10 of 10 Old 01-10-2008
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Pegasus (arf!)...

Your experience differed because of the frequent use of your boat ("about twice a week from May to October"), and because you kept the battery on a smart charger over winter. Letting a flooded battery rest for a few days is OK. Letting it sit for weeks or months is not OK.

A solar panel, properly sized, can help a lot for a boat which is infrequently used.

Bill
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