Low Engine Voltage?

[asm777]

Hi Tugnuts,

We've just wrapped up 3 years with our Cutwater and been seeing "Low Engine Voltage" warnings last few times out immediately upon starting up the boat. The Garmin display shows engine voltage in the 12-12.5V range. After running for a while, the alarm goes away and engine voltage goes back up to about 14V.

It seems that the engine battery is discharging between outings... but the alternator (fixed, thanks eric) charges it back to "normal" while we're out?

How long are the batteries on our boats good for and should I be thinking about replacing this one?

Thanks!

 

[Eric R]

It would be the alternator on the engine recharging while underway. It sounds like your engine battery might be due for replacement.


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[asm777]

Oops. Thanks eric, fixed.

Is 3 years about normal for battery life?

 

[Eric R]

It really depends. I’ve seen people to say 3-5 years. I’ve also seen people get less, and more, than that. What type of batteries do you have - standard or AGM?


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[tugnnaweigh]

Rangers have a voltage gauge that monitor each battery bank, if you do, put the gauge on the starter battery and see how much voltage is present in the beginning and how much the voltage drops while the engine is turning over this will give you insight into your starter batteries present state of health, easy to do load test.

If your boat has the parallel switch that brings the house batteries into the starting circuit do that, noting voltage before and during engine starting.

Battery life of 3 to 5 is what’s hoped for, over 5 is gravy. Depends on type of battery, type of charger, if charger is also a conditioner, are all contacts clean, all grounds good?

Battery advice is change one, change them all, go over all connections at that time, avoid trouble, enjoy boating.

Tremendous tremendous amount of battery experience and great advice available here on the ‘Nuts.

 

[knotflying]

12.5 V is not a bad charge, about 90% state of charge. 12.6v is a full charge. The starter has tremendous draw. It is not unusual when starting the engine and having your chartplotter on to get a low voltage alarm while cranking. However, if the alarm is staying on once cranking has stopped it could be a sign of a battery on the weak side. As stated, probably a load test is in order to see what may be going on.

 

[Cutwater28GG]

I got that error when the engine battery was close to end of life. worse in cold weather. usually that error however would only appear if the engine failed to crank - really low volts.

I replaced battery all was resolved.

 

[stwendl]

State of charge is a useless number if you don’t know the capacity. If you fill a bottle with sand you can still add some water and think the bottle is full (soc =100%). But the capacity is not the same.

I had a once a battery that fooled all my testers claiming to be 100% full, charged fine, but just had no capacity. Once in a while one has to test the capacity, like emptying a bottle and refilling it to be sure the battery is 100%

 

[Cutwater28GG]

knotflying: why would the chartplotter show low volts when cranking? they are connected to two different isolated batteries?

I though the voltage readout on the garmin is being read from the feed to the garmin unit off the house battery. its not super accurate as its a long run from battery to plotter with potential volts drop off.

 

[knotflying]

State of charge is a useless number if you don’t know the capacity. If you fill a bottle with sand you can still add some water and think the bottle is full (soc =100%). But the capacity is not the same.

I had a once a battery that fooled all my testers claiming to be 100% full, charged fine, but just had no capacity. Once in a while one has to test the capacity, like emptying a bottle and refilling it to be sure the battery is 100%

I would have to respectfully disagree with your statement. One should initially have the proper battery installed for the intended purpose. State of charge is related to the particular battery in question. A battery can have a good state of charge, but be in poor condition and not hold the charge the appropriate amount of time. Your analogy is not correct in this instance because filling a battery (your bottle) with water rather than acid would most likely produce a zero state of charge. Doing one test on a battery is not all inclusive. This is why I tend to tout flooded. Checking the acid condition of each cell with a hydrometer tells a lot about condition of each cell. A load test should indicate the battery condition. If the engine battery was in good condition it should have been able to crank the engine. If it were in poor condition it would have cranked rather slowly and the voltage dropped and not recovered.

 

[knotflying]

knotflying: why would the chartplotter show low volts when cranking? they are connected to two different isolated batteries?

I though the voltage readout on the garmin is being read from the feed to the garmin unit off the house battery. its not super accurate as its a long run from battery to plotter with potential volts drop off.

I am not sure how your boat may be wired. My Garmin also ties into the Yanmar info. Hence, If I have my chartplotter on and then start the engine I will get a low voltage alarm transmitted via the Yanmar info.