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post #1 of 23 Old 04-15-2011 Thread Starter
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Equalizing, cooking or over charging batteries

I have three everstart 115 amp marine grade Everstart batteries. Here in Roatan Honduras I got to talking with people about getting new ones because now when I turn on a flourescent light or change the contrast on my GPS I can see a voltage drop on my display.

A friend suggested equalizing them or cooking them for five or six hours with abot 14 volts . Anyone have suggestions for such a procedure? I am not sure that my on board grid connect charger has such an option.

Tomorrow I plan to get a liquid density tester for each of the banks. I hope that this will tell me something about the acid in the batteries.

Also someone else told me that because I am in Honduras its possible to dump all of the acid out and replace it with new Sulfuric acid bought from the autoparts store.

If I need to replace them I will probably go with two standard 6 volt batteries and one 12 volt marine grade deep cycle and separate them with a toggle. The 12 volt will be my designated starter battery and the 6 volts will be for running everything else.
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post #2 of 23 Old 04-15-2011
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For a flooded battery the bulk/absorption stage of charging should be about 14.4 volts. Equalizing is about 16 volts, but very low current. Without either a charger with this option or an external regulator for your alternator with an equalizing setting I don't know how it can be done on board.

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post #3 of 23 Old 04-15-2011
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Quote:
Originally Posted by akin_alan View Post

1, A friend suggested equalizing them or cooking them for five or six hours with abot 14 volts . Anyone have suggestions for such a procedure? I am not sure that my on board grid connect charger has such an option.

2, Also someone else told me that because I am in Honduras its possible to dump all of the acid out and replace it with new Sulfuric acid bought from the autoparts store.
You could full field the Alternator and use the engine RPM's to adjust the voltage. Be careful, it will go really high on the volts if rev'ed too much

Never ever replace the Acid, just use water to top them off only or it will turn the battery plates to mush.

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post #4 of 23 Old 04-16-2011
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I think the batteries were in a state of discharge for months and are sulfated and will not take a charge. The hydrometer (liquid density) readings will tell if this is the case, the readings will show completely discharged. You will then need new batteries. And, why are the batteries not being charged? Something must be wrong with the charging system unless the batteries sat for a year unused.

Last edited by LakeSuperiorGeezer; 04-16-2011 at 10:40 AM.
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post #5 of 23 Old 04-16-2011 Thread Starter
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LakeSuperiorGeezer, they were not in a state of discharge for even 20 minutes. I have been living on the boat for a year and half. This morning when I woke up and checked the voltage they were reading 12.5 with no load. Upon turning on a small flourescent light however they drop to 11.6. This has been going on for some time. The battery hydrometer that I am borrowing I am afraid is junk. I will search the net for the temperature tables and see if someone has a descent one. A friend said that he has a charger that he can loan me to equalize the batteries.
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post #6 of 23 Old 04-16-2011
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You've been using them pretty hard for a year and a half. Discharge/recharge cycle is important to some batts, but I can't keep track of which. How old are they? Could it just be end of life denial?


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post #7 of 23 Old 04-16-2011
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Quote:
Originally Posted by akin_alan View Post
LakeSuperiorGeezer, they were not in a state of discharge for even 20 minutes. I have been living on the boat for a year and half. This morning when I woke up and checked the voltage they were reading 12.5 with no load. Upon turning on a small flourescent light however they drop to 11.6. This has been going on for some time. The battery hydrometer that I am borrowing I am afraid is junk. I will search the net for the temperature tables and see if someone has a descent one. A friend said that he has a charger that he can loan me to equalize the batteries.
Alan,

Neither voltage nor specific gravity (as measured by a hydrometer) are indications of the capacity of the battery. Rather, they are indications of state-of-charge (SOC) of the battery. These are not the same thing.

Sounds very much like your batteries are at the end of their useful life. Those with a high SOC will show near normal resting voltage but won't be able to deliver significant amperage for very long. Think car batteries: you can have an older car battery which is fully charged, has a "normal" resting voltage, but can't turn over your engine. It's capacity is shot (see below).

Before concluding that this is the case with your batteries, either borrow a real battery tester which measures capacity (like the Midtronics series...these cost $600 and more, so most boaters don't have them), or do a controlled load test over time.

What kills battery capacity?

. sulfation (formation of PbSO4 crystals on the plates, which become embedded and limit available plate area)

. contamination of the electrolyte

. corrosion and erosion of the plates

. stratification (different concentrations of electrolyte at different levels)

. physical damage to plates or connecting rods

. buildup of sluffed-off material in the bottom, causing intermittent shorts, or worse

. etc.


Bill

Last edited by btrayfors; 04-16-2011 at 12:44 PM.
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post #8 of 23 Old 04-16-2011
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Alan, without any information about how old your batteries are, how deeply and how often you cycle them, and what your charging system is, we can only guess.

But a typical battery system comes up to 13.6 volts "hot charged" which drops to 12.6 or 12.7 volts after the surface charge has gone away (overnight or after a small use) and when it shows 11.6 volts under any load--that's a dead battery.

Could be normal wear, could be sulphating. Equalizing will not really help a battery that is shot, it will just help keep good ones in best condition. I would suggest that you check the web sites of some battery makers, as they all pretty much give the same advice, and sned your "replace the acid" guy off to someplace where he can't do any harm. Someplace far away from your boat, where there are no batteries.

A hydrometer is not expensive and shouldn't be hard to find, even in Honduras. A good quality multimeter is also quite useful in finding out what your batteries and charger really are up to, but again, you'll find plenty of existing threads here and elsewhere about how to check this out.
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post #9 of 23 Old 04-17-2011
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I Could Be Wrong

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Originally Posted by LakeSuperiorGeezer View Post
I think the batteries were in a state of discharge for months and are sulfated and will not take a charge. The hydrometer (liquid density) readings will tell if this is the case, the readings will show completely discharged. You will then need new batteries. And, why are the batteries not being charged? Something must be wrong with the charging system unless the batteries sat for a year unused.
To prove that I am wrong, put a battery charger on your battery bank and see how long it takes to charge, that is see how long it takes for the voltage while charging to reach the absorption voltage. The absorption voltage varies by temperature: 40 degrees Celsius, 13.98 Volts; 30 C, 14.19 Volts; 25 C, 14.34 Volts; 20 C, 14.49 volts. Lets take 30 degrees Celsius as you average temperature so it's 14.19 volts. So your multimeter has to stay constant 14.19 volts for charging to reach 70% charge. At that point you are at the topping off (absorption) part of the charging and the current will decrease and the voltage will stay the same. The rise will happen rather abruptly. Time how may hours it takes to get to the absorption voltage. Also, write down the average current (amps) that are going into the batteries. Multiply the amps times hours to get amp-hours that went into the batteries. Divide that by .7 (70%) to get the actual amp-hours your batteries will hold after charge is complete with the topping off (absorption). You can also multiply by 80% because battery charging is not 100% efficient. Since you have three 115 amp-hour batteries, you will have 345 amp-hours to charge up if the batteries are not sulfated. If you get more than 170 amp-hours into the batteries but less than about 345 amp-hours, you can try force charging, but keep a careful eye on the hydrometer readings because force charging is likely to erode the battery plates and cause material to fall off the plates into the bottom of the battery. If enough falls off and reaches the bottom edge of the battery plates, it will short the battery cell. Of course loosing active material also reduces the amp-hours a battery can hold.

You can also do this the other way around, charge the batteries, turn on lights in the boat, say 12 watts total which would be about one amp. Will the light go for 345 hours, or for 69 hours at 5 amps or 60 watts.

Last edited by LakeSuperiorGeezer; 04-18-2011 at 09:16 PM. Reason: Changed wording from single stage to multi stage charger
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post #10 of 23 Old 04-17-2011
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Lake

I don't see how that can be done. With a proper 3 stage charger, when in bulk or absorption stage the charger will be at about 14.4 volts, and as long as the charging continues the voltage at the posts will be the same - 14.4 volts.

I would charge them with a good charger, with no loads on them, let them sit for half a day and then measure the voltage. Should be 12.6 volts or higher. Apply a load of 5 to 10 amps for up to an hour. Turn off the load and measure the voltage again. If it is low as before (11.6 volts) I would suggest new batteries.

Brian
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Last edited by mitiempo; 04-17-2011 at 10:03 PM.
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