25 SC 2014 Battery Bank

[Steadfast]

First time this has happened. Hooked up to shore power for days. Disconnect shore power, start the engine and the ECU alarm is up on the Garmin Autopilot . Battery bank 3 is reading about 8.5-9.0. The Garmin navigation screen won't start up because there is a low amp alarm. I checked the battery cables, they seemed fine. The batteries are only two years old.
All my switches are on expect for the parallel which is off. I think the guy with me turned then OFF and then on again. We notice all of a sudden #3 battery bank is now reading about 13?

We get underway and about an hour later shut down the engine. Go to restart and the # 3 battery bank shows about 8.5 again and the NAV screen is off again.

I'm not sure what we did but a few minutes later the #3 battery bank shows about 13. The guy I was with thought the batteries were probably fine but the #3 gauge or wiring was the problem???

One concern I have is the Nav screen will not power up if it thinks we only have 8.5 amps. Not sure what to do next??

Any thoughts?? Thank you Brian

 

[Red Raven]

Are you sure the battery charger was turned on when you were on shore power? On our boat it is on a separate breaker and is easy to forget to turn on. If your battery is at 9 volts I don't think the ACR will allow it to be charged.

I assume bank #3 is your house bank? On our boat it is #2 the thruster batt is #3. If it is really #3 the parallel switch won't help assuming the parallel switch is between #1 and #2 as in our boat. You could use a jumper cable between it and the start battery (after you start the boat!) to get it charged but it may be damaged beyond hope at under 9 volts.

Curt

 

[Steadfast]

Thanks Curt

I will have to think about this some more. I think it's strange that at one point # 3 bank reads 8.5--9.0 and then a few minutes it reads 14??

Brian

 

[captstu]

The cheapest thing to do is change your batteries.

Alternately have them professionally load test.

Once the engine is started and the alternator begins to try to charge the batteries relays will bring the batteries together and even a dead battery will appear to be charged.

 

[knotflying]

Two year old batteries should not be bad if they were properly cared for. Ranger is known for having different wiring scenarios at different times. First identify your battery banks that your meter is reading. It sounds like, from your description, that bank 3 is the house. The parallel switch should join the start battery and the house. If your friend turned the parallel switch on it would have joined the house and engine. Hence, while the engine was running you would have been getting a charge into the house bank and it would have jumped up to the 13/14 volt range. With batteries fully drained you probably only got what is called a surface charge with a short run and in a short period they went low again.
You need to figure what may have drained the batteries in the first place. As stated earlier you may not have had the charger on. Were you running your refrigerator? That is a big draw and could have killed the house bank depending on how long it was on without the charger. Hopefully this is a matter of owner induced operation and not bad batteries, cha-ching.

 

[NorthernFocus]

Rather than piecing together what you observed/experienced that day it may be best to start from scratch and just try to get things working. Make sure you understand the system and how it works. For future reference:

1) your electronics run off the "house" battery

2) when the engine is running the house battery charges through the ACR switch. If the house batt drops below the minimum threshold(nominally 10V) then the ACR will NOT connect it to the charge circuit. In that case WITH THE ENGINE RUNNING you have to use the house/engine parallel switch to get the house bank to charge.

3) as mike pointed out once a battery has been pulled down that low it takes many hours to get it recharged. running the engine for an hour barely started to do so. with the engine running all three batteries should read 14+ volts. if it was only reading 13V while the engine was running the battery was still pretty much dead.

It sounds like the battery charger was not turned on while the boat was sitting on shore power. The house battery is the only one with significant loads on it so without the charger running the other two banks won't pull down for days/weeks.

If the battery was in fact at 8V and was that low for several days it's capacity has been significantly and irreparably reduced. But it may still be adequate depending on how you use the boat(i.e. how long you need to run on battery power) Figuring out how the system works and how to prevent discharging the batteries in future is a good idea before investing in new ones.

 

[knotflying]

On a positive note, I had Optima on my C-dory. I called them to ask how long were they good for. They told me it is not time, but number of times depleted to a full discharge. I can't remember the exact number, but I seemed impressed that it was so many times. So you may have done some damage, but not enough to have a significant loss of life. Keep your fingers crossed.

 

[NorthernFocus]

...I think it's strange that at one point # 3 bank reads 8.5--9.0 and then a few minutes it reads 14??

As I read your post the higher voltage was while running. You were basically reading voltage of the charge circuit, IOW the alternator output.

As Mike said if you have optima batteries then disregard my comments re.battery damage.