Coach batteries won't last one night

[DSCHIESSER]

I have a 2011 Monaco Cayman with 7 solar panels and 4 6 volt Coach batteries. I can't even get through one night with just the refrigerator on before they are too low to power it. I had the batteries tested and they are good. Any suggestions on settings or what I'm doing wrong?

 

[Jim]

I have a 2011 Monaco Cayman with 7 solar panels and 4 6 volt Coach batteries. I can't even get through one night with just the refrigerator on before they are too low to power it. I had the batteries tested and they are good. Any suggestions on settings or what I'm doing wrong?

The 4 batteries are probably connected in series and then parallel, so in essence, you have 2 12v batteries. And the amp storage of those batteries is less than the refrigerator is drawing. For instance, the batteries probably have a few hundred amps storage and the refrigerator is using every bit of that during the night.

Take a look at the batteries and let us know how many amps they have. And then look at the refrigerator and see how many watts it draws. We'll do more math when you get back.

 

[DSCHIESSER]

 

[Jim]

So 2 of the 6 volt batteries are connected together, making a 12 volt battery. The other 2 are connected the same way. That's called series. Then the 2 sets (of what are now 12 volt batteries) are then connected together, positive to positive and negative to negative.

When you connect the batteries in "series" you double the voltage, so the 2-6 volt batteries became a 12 volt battery. The amps remain the same at 400.

When you connect them in parallel, you double the amperage, so you now have a total of 800 amps of storage.

If you look at the sticker on the inside of the refrigerator, you find out how many watts the refrigerator is pulling. We'll need to find all the other things like TV's, fans, lights, and add them to the watts that the refrigerator is pulling. Then we'll convert the wattage into amps used per hour, and we'll see what the total draw on your battery bank is.

 

[Jim]

As an example, I have a Norcold refrigerator that consumes abound 500 watts each hour. Converted to Amps, (500 watts / 12 volt) it eats up about 40 amps of my battery storage each hour. If I had a total of 800 amps storage, as you do, then I could run my refrigerator for about 19 hours. Note: This is a total amount of amps that are in the battery bank but you shouldn't drain your batteries beyond 50% as it will shorten their life.

If your refrigerator is using the same amount of power as mine, then you should have plenty of reserve power to run your refrigerator all night. So if it's not, then something else is eating away at that reserve power. TV's? Fans? Lights? And the inverter is getting some as well. My inverter is eating about 4 amps every hour it runs, so over a period of 10 hours, I've lost another 40 amps.

Lots of little things added up can make a big difference.

 

[TJ&LadyDi]

I have a 2011 Monaco Cayman with 7 solar panels and 4 6 volt Coach batteries. I can't even get through one night with just the refrigerator on before they are too low to power it. I had the batteries tested and they are good. Any suggestions on settings or what I'm doing wrong?

Were the batteries tested under load or just static tested for voltage?

@Jim is spot on regarding checking your electrical draws. There are lots of unseen parasitic draws that add up pretty quickly.

TJ

 

[Jim]

Another thing, are you sure the batteries are getting fully charged? Are you completely dependent on the solar panels to charge the batteries?

 

[AbdRahim]

When I had my Class C, it had 2 12 v house batteries and I had a similar problem. Running just a few lights and the fan for a while in addition to the RV refrig, The batteries would be down to 50% by morning. The current A has 6 12 v batteries for the house and residential refrig. When I pull into a truck stop for the night, I automattically turn on the generator and usually just run it all night. Some times I will turn it off at a middle of the night potty trip and then back on in the morning.

 

[Chuggs]

You aren't doing anything wrong...

I don't know who or how they tested your batteries. Most places are looking for an acceptable level of amp delivery in a short period of time...and voltage. Deep cycle batteries require a timed discharge test. Golf Cart places probably have this type of equipment. Like TJ mentioned...the type of test is important.

Your rv is basically a timed discharge test when it cannot make it thru the night. But, it doesn't necessarily mean it's your batteries.

Two tools that are useful are a clamp on dc amp meter...and installing a shunt based battery monitor. Clamp meter will help you trace where these amps are going. The battery monitor usually has a user resettable amp counter. You can use this to see what your use is.

Eliminate loads...

Maybe you need to pull everything, clean up the terminals, look for corrosion, check cables and jumpers...proper torque on terminal fasteners. Double check charge parameters. Make sure flooded batteries have proper water levels. Account for temperature effect...does your charger automatically compensate? If not, if you can manually set parameters...they might need tweaking.

If you pull them...might let them sit for about 4 hrs disconnected completely and take individual voltage reading.

Lead chemistry is prone to sulphation...you might recover some capacity by doing a conditioning or equalization charge.

After tracking these things...the bottom line is batteries do lose capacity over time. It may be time. I am, as we speak, am in the middle of replacing my house batteries. My five year old batteries still charge fully, have great resting voltages, but I notice the voltage drop as I use them....drops faster than what was normal before. It takes less than half the night for them to drop to a voltage comparable to 50% charge...whereas I used to be able to make it thru the entire night
..and still be up around 75%...(928aH bank)...and 70% after my espresso machine heated up...

If you park with shore power...you can milk batteries way beyond their intended useful life. Off grid is where we find out it's either time...or we need to check the system thoroughly for trouble spots.

If you see unexpected loads...the load your looking for can be as simple as a dirty connection. The device pulling the power hasn't increased it's appetite...but the connection is probably stealing energy and creating heat. Carefully check temperatures of your cables and connectors...this may be the culprit.

Wish it were easier...but there are many weak points to be on the watch for.

 

[TJ&LadyDi]

Excellent summary, @NWIP.

TJ

 

[NWIP]

Credit needs to go to @Chuggs, I was gleaning all the info he posted and learning myself?

 

[TJ&LadyDi]

Credit needs to go to @Chuggs, I was gleaning all the info he posted and learning myself?

Oops! Sorry, Charlie; getting things right wasn't my strong suit yesterday. Mea culpa! It was a great summary, nevertheless, @Chuggs.

TJ

 

[Kevin D Pem]

Another thing, are you sure the batteries are getting fully charged? Are you completely dependent on the solar panels to charge the batteries?

@Jim is spot on with the charge. I maintain that the weak link in any electrical system is not the battery bank. No the weak link is the charging system. If your charging system shows the voltage is lets say 14.4 in the morning that only gives about 3 hours of bake time before the sun sets. I like to point out that like a cake in the oven, just because the temp is where it is supposed to be does not mean the cake is done. Did you know that the last 20% of the battery charge for your bank (4x6v bank) if charged in a way as to not hurt the batteries will take in excess of 10hrs?

Lets look at my numbers:

My system has 8 panels (8x250w)
Three controllers
2 x 200 ah AGM batteries set up for 24v system.

because I only have room for 200ah of batteries my controllers will not pump more than 750w of power in them in the morning. By noon the output of one controller has gone to 0w and the other two are producing less than 60w apiece.

There is nothing wrong with my panels or controller they do as they were designed. They were designed to protect the batteries first and being MPPT designed second to get as much power out of the panel when needed. After a week of cloudy skies the controllers require a full week to top of the battery bank, and my bank is considered small.

My refrigerator has a KWYr rating of 345 so it is designed and tested to use less than 1kw a day. (look for a yellow EPA tag online for your fridge). It will run on 280w solar panel with no problem on sunny summer days. I have no idea if that is true on winter days.

You can figure if you have 100w panels you will get maybe 75w mid day. with that info you can guess or if you are really good with math figure the power curve for the number of daylight hours to see how many watts actually make it to the battery bank after the resistance of the battery.
for people with limited solar I recommend the use of a generator for 3 to 4 hours to take care of bulk charging then let the solar do the rest.

 

[Chuggs]

Credit needs to go to @Chuggs, I was gleaning all the info he posted and learning myself?

No credit due...I learned it all from the community. Just trying to help others as I have been blessed with help from others.

Your mileage may vary, @Chuggs cannot be accountable for the accuracy of his content.

 

[AbdRahim]

It makes me wonder how long do these generators last? One year and I am over 100 hrs. They add up fast. Only have 10 w solar.

 

[Jim]

It makes me wonder how long do these generators last? One year and I am over 100 hrs. They add up fast. Only have 10 w solar.

Mine is a 2009 and shows over 6,000 hours.

 

[TJ&LadyDi]

The Onan generators are pretty bullet-proof. I expect that they will last at least as long as the coach.

TJ

 

[Jim]

The Onan generators are pretty bullet-proof. I expect that they will last at least as long as the coach.

TJ

And as an aside, I believe Cummins owns Onan. So I would think their product is pretty solid.

Cummins Power Systems and Onan - the history

www.nooutage.com

 

[Kevin D Pem]

I believe Cummins owns Onan

yes they do.