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Date: 2 January 2019. Battery Check and Cheater Method.

© janice142

Aboard Seaweed I inspect my batteries the first week of each month. But checking each cell, load testing, and more all takes time. Sometimes I just want the job done. It is important to do this monthly, at least for folks like me using inexpensive lead acid batteries from Walmart. After six months of testing I am confident my  "cheater" method  is working well. Here is what I do.

Years ago a good friend used the word batts as a substitute for batteries when speaking with me. I got used to it and do the same in real life. As I write the way I speak, below you will see the word batts used interchangeably with batteries.

I am happy when my batteries show 12.75 volts.

Note: First I am going to cover how to properly test the batts. At the end I will tell you my Cheater Method.

Yes, I am sure most of you know all this. It is covered extensively by Real Experts.

Originally I would do the Full-On testing program every month. That meant I would separate each batt out from the system individually. Now experts will tell you that you need to do this 12 hours in advance of the testing. That is true, however this is real life. Batteries power my life so the whole Perfection Mode does not happen aboard Seaweed.

#1) Keep all batteries separate for the tests. Otherwise you get an average for the voltage. That figure will not help you isolate and correct any problems.

I wanted to show my multimeter with the two probes. Ignore the 5.43 number please. (It's an old picture.)

#2) The first check for my batteries is to determine the voltage via my multimeter. I place the red probe on the positive terminal of the battery, and the black on the ground. By comparing with the others in my bank I will know how the battery is doing.

Presuming all of your batts are approximately the same age, they should "wear out" aka lose their ability to fully recharge at about the same rate. What I am looking for are anomalies. A battery that is not the same as the others has a problem.

This was a trouble light for a car. It originally had a cigarette plug at one end.

Note: I removed the cigarette plug gizmo and attached alligator clips. In retrospect, I should have used larger clamps. Instead I utilized what was on hand. They work, but it could be better. Larger clamps would be easier to attach to the battery studs.

#3) Next attach a light (power drain) to the battery and watch as the voltage decreases. For a 1A bulb such as shown above, the voltage will usually decrease by .5 volts. In other words, the battery would start at 12.7 volts and while the light is on the voltage will decrease to 12.2 volts. When the light is removed the voltage resumes the original 12.7 volts reading.

This is called LOAD TESTING. That means I am placing a load (power drain) on a battery. Some batteries will show a full charge and yet not have power available to perform. The experts will call this a Surface Charge. Surface charges are not good. There is not really any power available to use.

Surface Charge for the gals: You've mixed your cake batter and poured it into a pan. The bowl still looks full from the side, but there is nothing in it. A similar thing can happen with batteries. The Surface of the battery plates will test fine, but when you try to use the power there is none!

What I look for: The voltage on a battery that is going bad goes down farther and faster than the rest. I then know I have a problem with that particular battery.

Lead Acid batteries require "topping up" (re-filling with DISTILLED WATER only) on occasion. A battery that is different from the rest could be low on fluid. Or out!

This battery had no fluid in the CELLS. You can see the plates that store the power are flaking and icky.

The above 12-volt battery was aboard the yacht with the 32-volt system I worked
on last year. Details can be found in the
Diagnosing a Bad Battery article.

Measuring the individual cells on Lead Acid batteries is easy. First remove the battery cap. Using a multimeter put one probe on the ground post of your battery. The positive probe is stuck into the fluid of your battery. Write down the voltage. Do this for each cell in the battery. The total is the voltage for the batt. Most of the time for a 12-volt battery I see 2.1 volts in each cell.

NOTE: IF there is a difference of more than .2 volts between the cells in a single battery, I know that within three months that batt will be toast. Each time one cell starts to go bad it seems like the rest will soon follow suit.


UPDATE. 5 January 2019. My friend Fred is a genuine electrical guru. He said he would not use a multimeter to test the individual cells. Instead he utilizes a hydrometer.


This is my hydrometer:


To use the hydrometer: Squeeze the bulb with the smaller tube in the battery acid. The liquid goes into the top of the hydrometer. Beads inside will float. By reading the markings, I can tell how healthy the battery is.

The problem with a hydrometer for me is that I want to know the specific number, not a percentage rating. Like my method of looking for anomalies or differences between the cells, the hydrometer will provide that information.

Another issue I have when using a hydrometer is that I seem less graceful with the battery acid. Too often some comes out of the tube gizmo. The bulbs do not last forever so if you chose to go with a hydrometer, be sure to buy a spare.


That said, many folks do prefer the hydrometer. Both provide information as to the health of our batteries. I'm not an expert, so will continue to do what I have done for years.

Real experts do utilize a hydrometer, and I
should copy those folks who are smarter than me.


Memory Lane: Aboard the 40'er I grew up aboard we did use a Hydrometer for many years. Then we switched over to a multimeter. I do not recall why, though Daddy was a numbers man too so perhaps that is why he preferred the multimeter. We did have one particular pair of probes for the battery cells.

The battery acid does damage the probes during testing. They will not last forever even when you wipe off the battery fluid immediately. Therefore my advice should you chose this route would be to pick up a free Harbor Freight multimeter. Use that unit just for your batteries.

Sometimes a person just needs a boat ride. This is Treasure Island which is on the west coast of Florida.

Treasure Island is a pretty area. It was nice to be underway again after the Red Tide abated.
My musings on red tide algae can be found in the
Red Tide and Forest Fires article.

Gosh it was good to be underway... soon I will have to head over to the American Legion for a visit.
For the record, yes my batteries are all okay now, though there is one I am keeping my eye on.

Eye Candy, aka another picture from my recent voyage:

But I digress...
The above battery testing method works very well. It provides precise information for those who desire it. Sometimes though I simply want the job finished and without a whole lot of hassle and effort. Here is the Cheater Method I use aboard Seaweed.

It is important to regularly check your batteries. When one batt stops accepting a charge, the automatic chargers will detect that lower voltage. The charger will keep plugging in power. All your batts can become damaged because one goes bad.


The Cheater Method - Battery Testing

One thing that is important to know is that at this point I have access to AC power. Thus, it is easy for me to turn on the breaker for my Battery Charger. I do this (power the charger) two to three hours before I want to check my batts.


Then I open up the bilge. I shoot the top of each cell (NOT just the battery or the studs, the individual caps) and check for temperature discrepancies.

My readings through the bilge for every battery except one was close to 82 degrees.


Recently I found one batt that was a lot hotter than the rest of my bank. One cell showed 102!

That battery got special attention. When I opened the cap I could see the fluid was low:

The water is down 1" from the top. The plates are still covered. That means that permanent damage is unlikely.

I topped off the battery with distilled water.

The following day I rechecked that battery, again turning on the electric battery charger preceding the test. All was well.

What you should know: Heat is ALWAYS bad.

Anytime something is hotter than it should be I investigate. It is important to figure out why that is happening. Daddy used to say "Things don't burn out. They burn up." We always paid close attention to unusual heat. I believe that is why so many items lasted us for decades.

To this day, I check for undue heat when I am running any powered device.
I will stop and allow a tool to cool off before continuing to work with it.

It is entirely possible that I am too cautious when it comes to using my tools. I rely on what is aboard my boat. Therefore I take care of what I own. For me that means not overstressing a motor nor running it hot.

In case you wondered: I write the date of purchase and warranty information on paperwork. Details on how I keep track of that sort of thing can be found in the Warranty Paperwork (SeaSense bilge pump) article.

 This is my infrared thermometer. You'll note the purchase details written on the paperwork.

 I always remove the 9-volt battery when I put away my Etekcity infrared gun. Otherwise the batt will die.
Affiliate link:
 Etekcity® Infrared Non Contact Electric Laser -58 to 716°F, -50 to 380 C

Besides my Vise grips, the infrared thermometer is my most used tool. You need one too, especially since they are now in the $15 range. Remember though when checking batteries to shoot the caps not the battery itself. That part is very important.

Affiliate link→

As for me, I will individually check each cell every quarter now instead of monthly. I am using the infrared thermometer gun every month. That's my take on the whole battery testing process.

I am posting this specifically for you fellows without easy access to your battery banks. The Cheater Method has been tested aboard Seaweed since last summer. The humidity of summertime was not conducive to me wanting to spend loads of time in the bilge, in case you wondered...

Please note that I am not an ABYC certified expert.
Therefore, follow in my wake at your own discretion.


The rest of my batteries,
82 degrees
The bad batt,
at 102 degrees
Low fluid level,
102 degree battery

Using the infrared thermometer did detect the battery with low fluid on one side of the batt this past month. The other side I did open and it was fine. As an aside, the temperature on the good side was 82 degrees just like the rest of my battery bank. When I did the full-on test for the new year all was well, including that battery which needed fluid last month. Knock teak!

My advice is this: Check once thoroughly and then
 use the infrared gun to monitor how things are.

To you and yours, I hope to see you along the waterways.

Thank you for reading.

How often do you check your batteries?
And, have you any other battery checks that you implement regularly?

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