Battery Life Problems

[Unregistered]

Over the last two years, I have replaced both of my batteries. After a day of power-sailing, I find that I can run only a fraction of the lights, etc. that other companion boaters are using. My batteries to run very weak, very quickly. I have had the alternator checked/services and it is in good working order. Is it possible that the draw from my engine does not allow enough energy to go towards recharging the batteries to their full state? I believe that I have the standard 35 amp alternator, so will the 55 amp or even the more powerful 120 amp one that you sell make much of a difference to the recharging of my batteries? Lastly, if I get the 120 amp alternator, is it the same size as the 35 amp and would there be any problem having too much amperage being generated?

[Don Moyer]

Before spending any money on a new alternator, I recommend that you purchase a small digital volt/ohmmeter (if you don't already have one), and make a few checks:

1) If you have the ability to connect to shore power to charge your batteries, check the voltage in both batteries after 24 hours of charging to verify that they are both fully charged. A fully charged battery should measure approximately 12.6 volts. For a good check, it's best to disconnect the cables after charging, and let the batteries sit for at least 15 minutes to 1/2 hour before checking them.

2) Leave the batteries disconnected, and check the batteries once each day for several days to determine whether they are maintaining their charge.

3) After confirming that your batteries are OK, reconnect the ground
(black) cables to the batteries, but just before reconnecting the positive cables, check for continuity between them and the positive terminal of the batteries. With the battery master switch on, and all your electrical equipment turned off, you should measure an infinite resistance between the battery terminal and the positive cable (total lack of continuity). If you measure continuity at this point, it would indicate that there is a short to ground someplace in your electrical system. The lower the resistance, the more direct the short would be.

4) Assuming no problems were discovered in (1), (2) and (3) above, start your engine and measure the voltage across the terminals of both batteries. The regulators in standard 35 amp Motorola alternators are biased to maintain approximately 13.4 volts. It's actually a good idea to measure the voltage directly at the output terminal of the alternator and at the batteries. If the voltage measures correctly at the alternator, but reads lower at the batteries, your problem is a loose connection somewhere within the charging circuit, or perhaps the wire is of too small a gauge. Charging circuits are typically 8 gauge orange wire.

NOTE: If you discover a voltage drop in your charging circuit (a common problem within the Catalina 30 fleet), you can connect a short wire from the output of the alternator directly to the positive battery cable on the starter solenoid. This wire will render your ammeter dysfunctional, but you can verify the charging rate by using your voltmeter to insuring that your alternator is maintaining the normal voltage of 13.4 volts.

[dtinder]

Another approach to testing the reliability of the batteries: Borrow a load tester from your mechanic friend. When you first hook it up it will tell you the voltage---12.6 (or 13.2) depending on where you went to school---on your fully charged battery. Now---READ THE INSTRUCTIONS on the face of the load tester-----push the "TEST" button and hold it for the specified time. If the needle goes to some color other than green----look for your warantee card.

Assuming you have two batteries---replace both of them if needs be. If you have an "isolator" in your charging circuitit might be well to have a hard look at that too.
Good Luck,

[Don Moyer]

Dave,

Thanks for the suggestion regarding use of a load tester. If my understanding is correct, this test would save you the day or two of waiting for the batteries to deplete naturally - that is, without an artificial load being applied.

I also like your idea of replacing both batteries at the same time. I know that this can be a rather daunting investment, but it makes managing of the batteries through a manual (Batt 1, Batt 2, Off, Both) switch much easier, and could save the cost of expensive controls to automate the charging rates of the batteries separately. Many of the product descriptions for isolators, combiners, etc. start with the statement: "In the event that one of your batteries develops high internal resistance and tries to draw more current from the alternator......".

At the risk of stretching your advice too far regarding replacing both batteries at the same time, I also like the idea of using batteries of the same type, because it seems to me that it makes management of the charging and usage rates of the batteries easer if you don't have to be concerned about saving one battery only for starting, and the other one only for house use.

Hopefully, we'll hear some other experience based advice on this important subject.

Best regards,

Don Moyer