House batteries

[Jeremy Parrett]

I have 6  6 volt 225 amp hr Interstate batteries that make up my house battery bank.  They are 2 years old.  I have completely discharged them a couple of times ( C12 computer) as well as running the electrolyte level down to the plates.  
All this aside,when I am on the road the volt  meter on the dash runs up to 16 volts........the Silverleaf computer    reads 14.4 volts  DC ......which is correct.  
I noticed that the battery cases have a slight bulge at the ends and after running all day there is a mess of dust mixed with wet electrolyte all over the battery tops which is a very messy job to clean up.......the electrolyte levels are all correct.
 Question : will sulphated batteries cause the alternator to over charge said batteries or could the overcharging be caused by something else.
Why would the dash voltmeter read 16 volts when the Silverleaf reads 14.4 volts ??

[Gerald Farris]

Jeremy,
The dash volt meter reads 16V because it is wrong. The Silverleaf reading is virtually always correct, however the dash gauges are so inaccurate that the term used for them is "For entertainment purposes only".

As for your question about sulfated batteries causing the alternator to overcharge, the answer is no. Sulfated batteries do not cause an alternator to overcharge. The charging voltage is regulated by the voltage regulator that is built into the alternator.

Gerald

[Jeremy Parrett]

Gerald,
   I agree completely .   The dash voltmeter reads chassis battery voltage......correct?  The alternator  output voltage is correct at 14.4 volts  as per The Silverleaf.  How can  the chassis batteries be overcharged  to cause them to overgas when the 2 chassis batteries are doing fine !!   Puzzling........
I am going to replace all 6 house batteries when I get back to Florida next week hoping the problem is with the house batteries.  
For instance if one of the 6 volt batteries has a dead short would that cause the house battery bank to be over charged while the chassis batteries remain at 14.4 volts.  
How is the alternator connected to both battery banks  for charging? Is it hard wired?  
Is there a device that distributes  the charge between the 2 battery banks??
        Jeremy

[Gerald Farris]

Jeremy,
When the engine is running, the house batteries are receiving the same charging voltage from the alternator that the chassis batteries are on your coach.

The two battery banks on your coach are separated by a large diode called a battery isolator. The battery isolator lets the alternator charge both battery banks evenly, but the current can only flow in one direction, from the alternator to the batteries. Since the current can only flow in one direction, one battery bank can not discharge into the other bank. Therefore the batteries are isolated from each other while still being charged from the same source.

You said that your engine alternator was charging at 14.4 volts. Is that cold, when first started, or is that when the alternator is hot after running a while?  Although that is within the range for an alternator. It is on the high end, especially if the engine has been running a while and the alternator is hot. I like to see 14.1V to 14.2V when cold with good batteries and 13.8V to 14V when hot. Your cold charging voltage will be less if your house batteries are discharged, and they have to be recharged before the alternator can produce maximum voltage.

You said that your coach batteries were only two years old. A set of good quality coach batteries that are properly maintained should last 6 to 8 years. As your coach has 6 coach batteries, you may want to check the batteries before you discard $600 to $1,000 worth of batteries.

Gerald    

[Jeremy Parrett]

Gerald,
  Checking the coach batteries will be the first order of business on our return to Florida on the 15th April.  
   If I have to replace the 6 coach betteries it will cost $565  for 225 amp hr from Costco.
         Jeremy

[Ken Buck]

Yes. A bad cell in one battery will make the regulator think that the bank needs charging and will keep voltage at the max which in your case is 14.4 that you're reading. It will also cause the other cells to boil because they are continuing to be overcharged, which is the moisture on top of the batteries. If you tried to run on the house bank for any length of time you'd find greatly reduced capacity. You really need to run a hydrometer thru the cells and see that you have a bad one. Even a cheapie model will let you compare one cell to another. You're going to find one cell is dead. (or maybe more)

While a set of maintained batteries will last many years as Gerald says, yours have been run dry which is very often a cause of early death, and been run totally dead, another killer. All the things you've said lead to the conclusion you've reached which is replacement. Before I threw $500 at it, I'd spend the $10 for a hydrometer at O'Reillys and prove to myself a cell was bad. (and I'd put battery water on my list of things to do each month, but I think you already learned that part)

Ken

[Bill Sprague]

And, to make it really easy, buy a Plews 75-030 Auto Shut Off 2 Quart Capacity Plastic Battery Filler at the BAC Amazon store here:  http://beaveramb.org/Amazom%20Ad/AmazonAd1RVProductsStore.htm.  On my computer it shows up on page 7.

[Ken Buck]

Bills idea is a good one if you have any trouble seeing into the cells. I use a battery filler on my boat for the batteries that I can't see into. On my coach the tray rolls all the way out so I can look directly into the cell and fill from my gallon jug of distilled water, pouring straight in. Roll out trays are really nice!

ken

[Harvey Ziegler]

I have a somewhat related issue. On our return trip from Idaho last week my voltmeter on the dash was swinging back and forth from about 13.7 volts to 14.3 volts about 30 times a minuite. I am in the process of replacing the voltage regulator as I have one on order.

When removing the alternator I found that the small wire that is the control wire for the regulator was 2 wires in the wire loom about 3 inches from the regulator but only 1 was connected. The wires are labelled ignition and battery. Should these wires be connected together or is for a mattter of choice as to what to use to control the voltage regulator.

Also found the output terminal of the alternator still hot with the chassis batterys completely disconnected and the coach batteries disconnect switch turned off.