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Old 10-12-2010, 14:32   #1
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House Batteries

I installed 6 deep cycle 12v batteries in my catamaran a year ago, and now after 5 months in the Bahamas last winter and having just moved the boat to the Virgin Islands last month, the batteries are a year old but with 6 months of cruising use on them. I was expecting 2 or 3 years life out of them. For my transit to the Virgin Islands last month, I was having trouble maintaining good charge on the batteries. With a full charge from the engines at night, and minimal draw overnight (fridge only) I was seeing a charge of only 12.2 volts in the morning.
Now on the hard in the BVI's, I had the batteries checked and was told I have two batteries with weak cells that are drawing all the batteries down. The mechanic recommended I buy 6 new batteries for dependability as I will be cruising the Caribbean for the next 6 months.
Several questions for the Forum experts please:
1. Does it make sense to replace all 6 batteries for the reasons stated?
2. What is the recommended battery for daily extended cruising use? Deep cycle is what I have now (from West Marine). I don't have a gen so need to charge the batteries with the engines and also have the benefit of solar and an Air X wind gen to assist with maintaing battery charge.

I have to advise the BVI company as to the type of battery I want and then see what is available for them to access for me.

Your advice is appreciated.

s/v afLOAT

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Old 10-12-2010, 14:50   #2
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I think you may have another problem in that batteries in constant use should last more than 2-3 years. More to the point, your charging system is probably slowly killing batteries and simply replacing them without looking into how they get charged is repeating the cycle.

Can you provide more info on the charging circuit, voltage readings under charge, regulator settings, recharge intervals, etc?

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Old 10-12-2010, 15:00   #3
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Very common problem, unfortunately.

BTW, I had my boat in Tortola for 11 years and had my share of battery problems, especially since I was often away for 3-4 months at a time.

OK, here's my prescription.

1. Use deep-cycle golf-cart batteries. Trojan T-105s can be had there for a not unreasonable price. Ask around.

2. I assume you have six 12-volt West Marine batteries. If so, that's about 600AH total capacity. To match that, you'll need six 6-volt golf-cart batteries (225AH each), totaling 675AH capacity. They will need to be connected in series/parallel, i.e., as 3 pairs of 12-volt batteries.

3. How you charge them is important, but most important is to keep them as fully charged as you can. Unless you power everywhere, you can't do that with your engine(s). Solar and wind generator sources will be needed to give those batteries a full charge. Happily, both sun and wind are freely available in the BVI :-)

4. Be sure to watch the electrolyte level...check it frequently. WaterMiser or HydroCaps are a very good thing to have as they help to reduce water loss and they make it easier to check the levels. Add ONLY DISTILLED WATER, when needed, until the level is about 3/8"-1/2" above the plates.

5. Make sure all your connections are clean and tight. Do voltage measurements with a good multimeter AT THE BATTERY TERMINALS, until you are sure that whatever meter you're using now is providing accurate information.

6. You didn't say how your battery charger(s) and alternator(s) are set up. External regulator(s)? Temp sensors? Capacity of alternator(s)? Capacity of battery charger(s)? How are they wired? Do you run all batteries as a single house bank? It would be good to know.

If you take good care of the new batteries, you should get 3-5 years out of them.

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Old 10-12-2010, 15:31   #4
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My Experience

Replace all six. Keep the one's that are good, I'm sure you can use them else where...windlass, separate bank for fridge.....etc.

I've spent a fortune on batteries, wet & sealed, and finally have got it configured right.

Charge management is critical, I have four charging sources, shore, engine, wind & solar. All managed with source controllers and combiners.

Two dead cells will kill it all.

Good luck, Cheers
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Old 10-12-2010, 16:17   #5
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s/v illusion, thank you for your reply. I am so "untechnical" I will not be able to answer your questions. All I know is that I have oversized alternators (which I have been told is "good") and the charging system is controlled by a Balmar smart regulator, which I know nothing about other than I had to have the centerfielder replaced last year.

The voltage readings while under charge can get up to 14.2 volts after running the engines for an hour prior to bedtime. By morning the reading will be down to as low as 12.2 volts so I usually fire up the engine(s) to charge the house batteries first thing in the morning.

I don't know the regulator settings as you have asked.

And the charging intervals for most days at anchor will be an hour morning and night with the solar panels and wind gen assisting during the day.
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Old 10-12-2010, 16:51   #6
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If you can reduce the size of the bank you can charge it back to a more full level than you do now. Too many batteries is actually a curse. Bottom line is you don't charge enough and in the process trash batteries. It's a sure thing no matter what you buy. Types of batteries won't matter that much if you don't recharge them properly. Cruising makes it hard to do but you need to cut the difference with more charging and/or less batteries. The power you can avoid using saves you more money than you think!

A battery monitor can help you keep an eye on how much power you use, waste, or just never thought about. When you can track usage you can match the size of the bank accurately and balance the charging. You have to pay back the debt every day in full in a perfect battery economy. Any day you miss costs you just a little bit of battery life. After you buy 6 batteries the 2nd time it starts to be real money.

Your charging interval is what it needs to be and has nothing to do with what you want it to be. Ideal is to drain to no less than 50% and always charge back to 100%. The last 10% on a recharge is hard. It looks like you probably don't get close to 90% when you charge. You are trashing batteries way too soon. Bill sums it up quite well.

I would add - Need less power!
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Old 10-12-2010, 16:52   #7
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Yeah, replace all 6 at over $100 each...........but you still most likely have the same problem.

How do you know you have fully recharged the batteries running your engine? Your engines more than likely have automobile style alternators that cannot output large currents for long time periods.

I recommend that you try charging the batteries with a smart charger, one with 3 stages. After charging, test them with an hydrometer. Voltage readings do not give a realistic indication of charge conditions.

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Old 10-12-2010, 16:58   #8
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Four pairs of Interstate 6 volt batteries while cruising last us an average of 7 years per pair. So there is obviously an issue with charging or maintenance or possibly a defective battery in the mix running down the entire bank. But only a complete analysis of the charging system and testing of the batteries can determine what is going on. Chuck
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Old 10-12-2010, 17:03   #9
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I agree with Paul. Too many batteries is not a good thing. Your bank, your charging system, and your energy budget need to match. Keeping an oversize bank half-charged is just begging for the batteries to sulfate.
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Old 10-12-2010, 17:14   #10
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12.2 is low?? Doesn't sound too bad for the hot tropics. The reference voltages will drop 0.022V/degreeC. (12.6 in the north can be the same charge as 12.2 in the heat of the day. (Plus many boat voltmeters are inaccurate)

...or 0.012/degreeF for the citizens of the imperial forces.
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Old 10-12-2010, 17:21   #11
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Paul, not sure that my house battery bank is excessive, given the potential draw of power every day (fridge running constantly, chest freezer turned off only at night; electric toilets in both heads; and a full whack of electronics, etc.) I do achieve a full charge when I recharge with a reading of 100% capacity if I can believe the battery meter on the electrical panel, which displays voltage, amp draw and battery capacity for both the house and starting batteries.
s/v afLOAT
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Old 10-12-2010, 17:25   #12
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Originally Posted by daddle View Post
12.2 is low?? Doesn't sound too bad for the hot tropics. The reference voltages will drop 0.022V/degreeC. (12.6 in the north can be the same charge as 12.2 in the heat of the day. (Plus many boat voltmeters are inaccurate)

...or 0.012/degreeF for the citizens of the imperial forces.
There is only one good way to test a battery and that is to use a temperature compensated hydrometer.
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Old 10-12-2010, 19:51   #13
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I have to agree with those who say too many batteries, too much draw and your charging system is suspect. If you are charging off of the alternators you batteries will never reach 100% especially if you have a few bad batteries amongst the group.

Go with true deep cycle. Either 6V golf cart type batteries or 8Ds. Expensive yes! But they will last longer if charged properly.

You need a three or four stage charger. That is the only way your batteries are going to be fully charged. Meters are good but they don't give the full picture. Use a hygrometer. Smart chargers sense the battery's condition, they don't just pour amps into the battery, which is what alternators do. A good three stage charger then adjusts it's output to the battery's condition. Four stage chargers will even equalize the charge among the cells in an individual battery so that each cell is at max and the same charge as it's neighbors.

Batteries (all batteries) require maintenance. Liquid electrolyte batteries must absolutely be checked for fluid level periodically. Mine are used continuously and I check the fluid levels monthly. But you may need to do this more frequently especially if those alternators are over charging. Over charging cooks the batteries and results in fluid levels dropping rapidly, and it damages the cells in the battery. I use a Xantrex three stage charger. But there are a lot of other good ones available. It keeps the batteries at 100%.

Running a refrigerator all the time will drain batteries rapidly. If you aren't using it at night (that is, taking food and drink in and out) shut it off. It will hold it's chill for 8 hours as long as you don't open it. Maybe not in the topics, but put a timer on it so it comes on every four hours during the night. And set the temp in the fridge a degree or two higher. It will save a lot of electricity and not affect the food.

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Old 10-12-2010, 20:09   #14
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Running engine to charge batteries at anchor is going to damage the engine as well.Diesels don't like idling without load on for hours on end as it glazes cylinder walls and shortens life of an expensive vital component on board.Why not buy a Honda generator,it will put way more juice into batteries quickly.I run 240 watts solar ,wind gen.,and as last resort a small Honda when nature doesn't provide enough amphours for my 600 AH bank.I would rather wear out a $1000. generator than a $15000. engine,much easier to change as well.The fridge is a huge draw in warm climates,not to mention computer, autopilot etc.,etc.Use your engine to get you places,when wind doesn't.
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Old 10-12-2010, 23:29   #15
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Yah, like they said... but also, shutting down the freezer at night does not save energy and the big temperature swings spoil the contents way faster.


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