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Maybe new battery time questions

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 04/03/2009 : 22:33:52

Another forum I post on has a censor - I forgot where I was.

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/06/2009 : 15:12:23

Well, it looks like I might be in the clear. When we got to the boat yesterday, my battery meter was very happy in the "green" section, reading 13.3 VDC. Of course I just realized that we may have left the cabin breaker on and the meter running.

Carp...

Oh well, it's a nice sunny day, they solar panel should be able to make up any losses due to the meter running. <Sigh>

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 04/06/2009 : 15:36:12

...And where should we be happy?

After a week with the charger on my Batteries, one shows 13.8V and the other shows 12.6. I thought th egoal was to get them up around 14.1. Should it take a week to get them there with a 2Amp trickle charge?

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/06/2009 : 16:18:19

From Wikipedia:
The following is common for a six-cell automotive lead-acid battery at room temperature:

Quiescent (open-circuit) voltage at full charge: 12.6 V
Unloading-end: 11.8 V
Charge with 13.2–14.4 V
Gassing voltage: 14.4 V
Continuous-preservation charge with max. 13.2 V
After full charge the terminal voltage will drop quickly to 13.2 V and then slowly to 12.6 V
Wait at least 12 hours after charging to measure open circuit voltage, the resting time allows surface charge to dissipate and enables a more accurate reading.

[url="http://en.wikipedia.org/wiki/Car_battery"]Full article here[/url].

It looks like you might want to give your batteries a day to rest before checking their voltage as indicated above.

I know at 13.3 volts indicated on my cheapo battery gauge ($15 at Walmart), my outboard will start right up. If it gets down to 12.1 volts, it won't even turn over, it'll click a bit, then go dead.

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 04/06/2009 : 16:37:12

So if I read this all right, the unconnected batter just sitting there after a day or so should be reading around 12.6 - 12.8?? Then they've been charged all along. I better never become an electrician.

Thats what Quiescent Voltage is, right?

Why is it that most gauges show the "green zone" going right up to 14 V? I thought that fully charged was at th etop of the green, and discharged was at the bottom of it. I have a cigarette lighter battery gauge which gives a digital readout and has a series of LED's that show where you are in the green or red zones (I need a reference since I am a dunce when it comes to all things electrical). I know, buy Don Casey's book. I'm getting more convinced every day.

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/06/2009 : 16:46:28

Chris,
If it makes you feel any better, I used to be an electrician in the USN. I dealt with batteries on a daily basis, but we always used a hydrometer to check their levels, no meters, except maybe our Simpson analog multimeters. Most of the battery technology we talk about on here didn't even exist the last time I used a hydrometer. I have several books on boat electricity and still get confused. Since I can't check my batteries (on ANY vehicle I own) with a hydrometer, I have to depend on meters to tell me what I need to know. It's not that I miss dripping acid on my dungarees, but at least when you measured them that way, you knew exactly what the state of every cell in your battery was. Even the ones today that have the built in "eye" hydrometer only measure one cell, the other five could be on their way to checking out, and you'd never know from the eye.

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 04/06/2009 : 16:58:02

Oh no David, now you help me embarass myself even more.

I took a bettery out of the boat, and with a hygrometer, checked every cell. I taped a piece of tape to the battery and wrote down the readings as I worked my way through.

Cell 1: 1200
Cell 2: 1200
Cell 3: 1200
Cell 4: 1200
Cell 5: 1200
Cell 6: 1175

Then I looked up what the numbers mean: The hygrometer readings show you the state of battery discharge. Great. I coulda told you that before I took the caps off... it was pretty much dead.

What tells you whether the acid needs replacing? Or if the plates are worn out?

At this point I don't know whether to trust the batteries, the voltmeter, the AC charger's readout, or the solar charge controller.

A man with one watch always knows what time it is. A man with two watches is never sure.

Edited by - Prospector on 04/06/2009 17:00:38

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 04/06/2009 : 17:03:39

I just cut and pasted this. I think I'll take it home tonight:

6. Battery Testing can be done in more than one way. The most popular is measurement of specific gravity and battery voltage. To measure specific gravity buy a temperature compensating hydrometer and measure voltage, use a digital D.C. Voltmeter. A good digital load tester may be a good purchase if you need to test batteries sealed batteries.

You must first have the battery fully charged. The surface charge must be removed before testing. If the battery has been sitting at least several hours (I prefer at least 12 hours) you may begin testing. To remove surface charge the battery must experience a load of 20 amps for 3 plus minutes. Turning on the headlights (high beam) will do the trick. After turning off the lights you are ready to test the battery.

State of Charge~~~~Specific Gravity~~~~~Voltage
100%~~~~~~~~~~~~~~~~1.265~~~~~~~~~~~~~~~~~12.7
*75%~~~~~~~~~~~~~~~~1.225~~~~~~~~~~~~~~~~~12.4
50%~~~~~~~~~~~~~~~~~1.190~~~~~~~~~~~~~~~~~12.2
25%~~~~~~~~~~~~~~~~~1.155~~~~~~~~~~~~~~~~~12.0
Discharged~~~~~~~~~~1.120~~~~~~~~~~~~~~~~~11.9

*Sulfation of Batteries starts when specific gravity falls below 1.225 or voltage measures less than 12.4 (12v Battery) or 6.2 (6 volt battery). Sulfation hardens the battery plates reducing and eventually destroying the ability of the battery to generate Volts and Amps.

Load testing is yet another way of testing a battery. Load test removes amps from a battery much like starting an engine would. A load tester can be purchased at most auto parts stores. Some battery companies label their battery with the amp load for testing. This number is usually 1/2 of the CCA rating. For instance, a 500CCA battery would load test at 250 amps for 15 seconds. A load test can only be performed if the battery is near or at full charge.

The results of your testing should be as follows:

Hydrometer readings should not vary more than .05 differences between cells.

Digital Voltmeters should read as the voltage is shown in this document. The sealed AGM and Gel-Cell battery voltage (full charged) will be slightly higher in the 12.8 to 12.9 ranges. If you have voltage readings in the 10.5 volts range on a charged battery, that indicates a shorted cell.

If you have a maintenance free wet cell, the only ways to test are voltmeter and load test. Most of the maintenance free batteries have a built in hydrometer that tells you the condition of 1 cell of 6. You may get a good reading from 1 cell but have a problem with other cells in the battery.

When in doubt about battery testing, call the battery manufacturer. Many batteries sold today have a toll free number to call for help.

Edited by - Prospector on 04/06/2009 17:08:48

David Scott
1st Mate

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USA
74 Posts

Response Posted - 04/15/2009 : 23:24:48

Prospector- your comments about sulfation got me thinking of what many of us forget... the importance of "equalizing" batteries. I will include myself in this because now that I am back sailing a C25 again I seem to have returned to my basic battery charger which doesn't have a "equalizing" mode. Finding my 4-5yr old batteries not holding their charge I started thinking about buying new ones. And I realized that I have never applied equalization to them. Maybe its too late now but I have tried in the last week to charge at a higher rate, 14.4 volts or higher for short period of time. Time will tell whether its too late to bring these batteries back to life. Rather then going on about the virtues of equalizing your batteries I will suggest the reader google "equalizing battteries" for more info.

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