Low Battery Alarm

[Pony]

I have a Huminbird 997c and a Huminbird 597ciHD at the helm, and both have low battery alarms. I had it set at 12.0 volts at the start of this season. On the first couple of trips, it never went off. My starting battery (which also runs all of the accessories) started to go bad sometime after that. Usually I never check that battery because the main motor keeps it pretty well charged unless I am really running a lot of extra stuff and not using the main motor a lot. I generally check in the driveway by turning the key to "ON" and listening for the beep and seeing the needle above 12 volts on the dash. At the end of one of the trips the low voltage alarm came on when I started the main motor to head back to the landing. I didn't think anything of it, sort of figured that the voltage dropped from the main engine starting. The boat sat a few weeks, and the battery was dead (could run electronics but not turn the motor over) when I got to the landing in the morning on the next trip. I did my normal key/beep routine in the driveway....which is now obvious to me not enough to think the battery is charged enough to start the boat. Clearly a sign the battery is not holding a charge correctly. I was able to run jumpers to one of the deep cycles to start the motor, and then ran it awhile to charge the starting battery....which it did....we were fine the rest of the trip. Next trip out, battery was charged the night before, and after a couple hours on the lake, the low battery alarm was sounding again....so i ran up the lake a few miles to charge it up.

I have now replaced the battery with a larger group 27 deep cycle, and have added a battery tender maintainer/charger that has a quick connect for when we get back home. The other deep cycles are connected to a two bank on board charger.....previously the starting battery was not on anything, With a good battery now, I doubt that it will drop to 12 volts on any given trip. I know that last season I had the alarm set to 11.5 volts, and I was able to start the motor on that when the alarm went off. I don't think that is an accurate reading as I doubt I could have started the Optimax if it were really that depleated.(That battery was replaced with a random starting battery I had laying around) I don't want to set it at 12.0 and have it going off all the time when the battery is really at 12.3 or something like that.

Do I set it at 11.5 or 12? under the assumption that 11.5 is really not 11.5 and proabably higher. The volt reading on the dash panel was close to 12 when the alarm went off at 11.5. Is this chart accurate?

 

[Silvertip]

You check the battery voltage with a "known accurate" meter. This will verify the error factor and you then set the low voltage alarm accordingly.

 

[Pony]

You check the battery voltage with a "known accurate" meter. This will verify the error factor and you then set the low voltage alarm accordingly.

I guess I will have to see how high I can set the alarm and see if I can get the alarm to sound and then check the voltage with a good tester and see what the difference is. Might have to just run the radio awhile in the driveway to use some battery to get that to happen.

Is that chart accurate? I have seen a couple of different charts. Some would consider 11.5v dead or red, some say 20% others 25%

 

[Silvertip]

The voltage being measured by a hand-held meter, your boats voltmeter, or the voltmeter in the locator will not likely read the same. Whatever reading you see will depend on what devices are running at the time and can affect operation of the alarm.

 

[Pony]

The voltage being measured by a hand-held meter, your boats voltmeter, or the voltmeter in the locator will not likely read the same. Whatever reading you see will depend on what devices are running at the time and can affect operation of the alarm.

That much I understand. If I set it to 13,0 volts and then run the radio until the alarm foes off, would I be able to somewhat accurately get the degree of error on the locator voltmeter if I checked the battery at the terminals with a tester at that point? So if the tester read 13.3 the moment the alarm sounds then I know its a 0.3 difference?

I guess this may not matter too much since I have already started the boat at 11.5 on the locator voltmeter and in theory my now healthy battery should never get that low in a day of fishing.

 

[dingbat]

Measure battery voltage on terminals with voltmeter and compare with locator voltage. The difference is the error. If it's like mine, the locator voltage is about a 0.5 volts off. Called garmin. They said they had never heard of such a thing but they would look into it. Called back 1/2 hr later. Voltage being read off unit's power supply, not line voltage

 

[Pony]

Measure battery voltage on terminals with voltmeter and compare with locator voltage. The difference is the error. If it's like mine, the locator voltage is about a 0.5 volts off. Called garmin. They said they had never heard of such a thing but they would look into it. Called back 1/2 hr later. Voltage being read off unit's power supply, not line voltage

Thats what I plan to do. I wish the locator read the voltage in real time to make it easier to compare. I have to set it to something and get the alarm to sound to know the voltage the unit is "showing"