Yet Another Battery and Alternator Question

[Marc14857]

As I indicated in earlier posts, I replaced my (2) 4D batteries this year with (4) 6 volt Crown batteries. I am not 100% sure that the batteries are operating correctly as when they are off the charger and under light load, the highest voltage I ever see is about 12.2 to 12.4 volts. I think based on other threads this is a little low. Most of the time the batteries are on shore power with the Freedom Inverter Charger at the float voltage of ~ 13 volts. I also notice that when I start the engine getting ready to leave the dock the low voltage alarm light is on until I rev up the throttle to about 750 to 1000 RPM. Belt tension is good. I have a new Balmar 100 Amp alternator and Balmar ARS 5 regulator. The low voltage setpoint is set at 12.7 volts.

Finally I have started to get a "NO DATA SOURCE" error on my Raymarine radar just as i am leaving the dock and the radar shuts down until I restart it. Raymarine says this can be related to a low voltage issue.

 

[Mac Smith]

I had similar problems on my earlier boat, when I had mixed battery types. The wet cell and the golf cart type mixed caused charger/regulator to be confused, and not top of the golf cart battery, until I swapped the starting battery to golf cart type also.
Golf cart batteries have limited "draw down" lifes causing earlier replacement also, whether discharged 10% or 90%, there is a limited count for the golf cart type.
I now simply use the least expensive marine battery with acceptable amp hours, and get 3+ years out of them.
Sorry I don't have a technical answer to your situation, but this solution worked for me.

 

[Maine Sail]

I had similar problems on my earlier boat, when I had mixed battery types. The wet cell and the golf cart type mixed caused charger/regulator to be confused, and not top of the golf cart battery, until I swapped the starting battery to golf cart type also.
Golf cart batteries have limited "draw down" lifes causing earlier replacement also, whether discharged 10% or 90%, there is a limited count for the golf cart type.
I now simply use the least expensive marine battery with acceptable amp hours, and get 3+ years out of them.
Sorry I don't have a technical answer to your situation, but this solution worked for me.

Mac,

Your issue probably had little to do with the golf cart batteries and more with the wiring of the system. There are thousands and thousands of boaters using 6V GC banks with 12V thin plate starting batteries who don't have these issues. Also 6V deep cycle batteries will last longer than just about any 12V deep cycle battery due to their thick plates that survive lots more cycling than do most any 12V batteries.





Marc,

You may want to check the specific gravity of the individual battery cells. Allow the batteries to rest for 24 hours completely disconnected then take SG readings. Any reading that is off by more than 0.50 is a strong indicator of a bad cell.


Bad cells can happen even on new batteries but Crown's are very, very well built and are usually a very reliable product. Also double and triple check your wiring, especially where your grounds are pulled off the bank.

 

[Marc14857]

Maine Sail

I do intend to check the SGs next time I am at the boat and will also check the grounds with a digital VOM. I guess that I am looking for < ?? ohms from the negative batt cables to ground?

Also if the batteries were fully charged, what would I expect to see for battery voltage?

Thanks Again
Marc

 

[Bill Roosa]

Agree with MS, probably a wiring issue.
There is a very easy way to track down voltage drops caused by corroded terminals. Did I mention that 99.44% of all electrical problems on boats are corroded terminals?
WITH THE LOAD TURNED ON take your volt meter and set it to the lowest voltage range. Test across each terminal/connector in turn in the circuit. A good connection will only show 0.1 volts drop or less. A bad connection will show more than 0.1 volts drop across the connectors. Clean/replace as needed.
By testing across the terminal/connector I mean probe the wire on each side. The concept is from V=IR in that the voltage "drop" is equal to the current flow times the resistance between the probes. Clearly measuring with the load off means 0 current and 0 times any resistance is 0 volts “drop”. That is why the load has to be on for this technique to work. The higher the current to the load the more important it is to have low resistance connections.

Your radar is seeing low volts (resetting) and your panel volt meter is seeing low(ish) volts and you are getting the radar reset right after starting the engine (when charging current is highest)(and any voltage drops will be greatest also) so I suspect that the problem is either in the battery terminals or the power/ground circuit of the radar set.
Is the radar resetting when you throttle up for the first time leaving the dock and the alternator “low voltage” alarm goes off? If so then you have a battery terminal problem. Otherwise I’d be looking in the radar circuit proper.

WARNING if there is alternating current (shore power) circuit breakers on the panel you will want to disconnect from shore power and turn off any inverters. 110 AC can kill

The “low voltage” alarm from the alternator is normal and only indicates that the alternator has not “fired up.” Once it starts to produce you should be able to throttle back and it will still keep operating.

 

[Marc14857]

Bill

Thanks for the advice. Hope to be up to the boat this weekend and will try to track down the bad connection using your technique The radar does not auto reset as I have to turn it off and on again to get it back on line. You are also correct that alternator light goes out after I throttle up but will come back on when i throttle down unless I have been running the engine for awhile.