Isn't 6 batteries better than 4?

[RV Vagabond]

My 4 month old class A came with 4 house batteries and I added solar panels 900 watts. Last week I added 2 more batteries, expecting the 6 battery bank to last 1/3 longer at night boondocking. However, it does not seem to have made any difference at all. Any clue to this mystery

[ByeTheWay]

Since you mentioned solar I assume you are not plugged in.

1. One rule of thumb is not to add new batteries to an old set. The old ones tend to draw down the new. This could be part of the problem.

2. If your monitor checks voltage, it can be misleading because of what is know as a surface charge/discharge. If this is the case, the best time to get an accurate reading is during the night when the batteries have been at rest for a few hours.
A more accurate monitor checks amps in and amps out. And gives a reading of SOC State of Charge. From 100% to whatever.

Perhaps this would help: RV Electrical

[MtnTrek]

Hmm, well that's a sizable amount of PV panel capacity.
We're not sure you've provided enough information.
What does your battery monitor (watt meter) tell you is going in and out of them?
What are all the batteries rated at?
How are they (batteries) configured?
What charge controller, and how is it set up, wattage?
What is the voltage and AWG cabling from the panels to the controller?
Is the battery array really fully charging?
Have the batteries been equalized?
How have the current batteries been maintained? Poorly used batteries even only 4 mo. old (deeply discharged) can be well into their useful service life.
Often mixing different types and aged batteries can yield less than optimal results.
The array will revert to the lowest common denominator.
Many would wait and make the change you made when replacing their current array with all new matching array.


Be well.

[l1v3fr33ord1]

Jerry-

I'll add to "MtnTrek's" questions:

Do you have a battery monitor panel? If so, what make and model is it? Did it come with the coach, or did you add it?

[twinboat]

Since its 4 months old, adding 2 batteries shouldn't be a problem.

The problem comes with the condition of the old batteries. How were they performing before you added the new ones ?

Dealers have a way of ruining batteries while on the lot. They let them sit dead, for weeks at a time, and just jump things to get it going.

You could do some tests by running things on the new batteries "only" to compare how long they last. If the 2 new ones out perform the 4 old ones you have your answer.

All batteries are the same voltage, 6 or 12, so hooking new to old does not drag one down to the other, unless it is failed and shorted.

The issue with old and new is that the new one will do more of the work then the old and seem to last less time.

If you don't have a battery monitor, you should add one to your system. It will give you valuable infomation of what's going on.

Here is a web site that has some good infomation about charging, discharging and maintaining batteries. It is a battery combiner site but look over the FAQ section for helpfull info.

Yandina.com

[vsheetz]

From you comments sounds like the battery bank was not lasting through the night before installing the two additional batteries. You then installed the additional batteries and still are not lasting through the night. I suspect that maybe the original four are not healthy, creating the original problem and thus keeping the two additional from performing as a hey should. I would suggest to do a specific gravity check (if wet cell batteries) and a breakdown box test on all six batteries to help understand condition of the batteries.

The other thought is one of what are your expectations? What all are you operating through the night? If lots of non LED lights, televisions, residential refrigerator, furnace fan, etc. maybe too much consumption.

[pcurt23]

Originally Posted by RV Vagabond

My 4 month old class A came with 4 house batteries and I added solar panels 900 watts. Last week I added 2 more batteries, expecting the 6 battery bank to last 1/3 longer at night boondocking. However, it does not seem to have made any difference at all. Any clue to this mystery

I have the same issue with my battery bank.

You need to determine how many amp hours you have installed. If you are using 220 amp hour batteries that means at full charge you could have 600 or so amp hours available. You can only use about half of that at one time without damaging your batteries. So now you have 300 or less amp hours available. If you are running the refrigerator then it is using 50 amp hours all by itself. So you get 6 hours out of your batteries. That is not over night. (my numbers are just examples for understanding) The example is if your battery bank is at 100% which is doubtful. Your solar array would have to be pretty big to recharge the batteries and run the coach during daylight. The generator would have to run several hours to get you to 90%.

Battery

Charge 14.2-14.6v
Float 13.2-13.7v

Full 12.6v
75% 12.4v
50% 12.2v
Discharged 11.7v

When all's said and done you are probably starting the night with about 75% charge on your batteries so you may have 2 hours of run time available.

This is a very simplistic example of battery life. There are people who spend a lifetime studying this topic. I turn off the inverter at night when I am boondocking and that seems to do the trick.

[TQ60]

First we need "clues"

What batteries are there now and what loads are you using.

Please search the forum for battery design, testing, charging and maintenance to get a lot of information to review.

A full discharge of MOST but not all lead acid batteries is when the terminal voltage is 10.5 volts or 1.75 volts per cell.

Many do not believe in using that part of the battery as it does cause a lot more wear but other issues may also wear out the battery so one could either add more and use less of them for price of battery space and weight or use more of less batteries and replace them a bit sooner.

Your needs and goals need to be determined.

Others mentioned dealers often abuse batteries and yours could be bad.

If only 4 months old then under warranty but be sure to have copy of coach bill of sale as warranty STARTS on that date.

Without the bill of sale the manufacturer of the battery uses the battery date code which is like much older.

Back to issue...

Are your batteries going dead in one night?

What are you operating?

[twinboat]

Originally Posted by pcurt23

I have the same issue with my battery bank.

You need to determine how many amp hours you have installed. If you are using 220 amp hour batteries that means at full charge you could have 600 or so amp hours available. You can only use about half of that at one time without damaging your batteries. So now you have 300 or less amp hours available. If you are running the refrigerator then it is using 50 amp hours all by itself. So you get 6 hours out of your batteries. That is not over night. (my numbers are just examples for understanding) The example is if your battery bank is at 100% which is doubtful. Your solar array would have to be pretty big to recharge the batteries and run the coach during daylight. The generator would have to run several hours to get you to 90%.

Battery

Charge14.2-14.6v
Float 13.2-13.7v

Full 12.6v
75% 12.4v
50% 12.2v
Discharged11.7v

When all's said and done you are probably starting the night with about 75% charge on your batteries so you may have 2 hours of run time available.

This is a very simplistic example of battery life. There are people who spend a lifetime studying this topic. I turn off the inverter at night when I am boondocking and that seems to do the trick.

Are you sugesting your fridge draws 50 amps, every single hour.

If it's a gas fridge leave it on gas. They use 3 times the energy of residential units.

My residential fridge used 10 amps, 12 volt DC, thru my inverter. It only runs 25% of the time. That is 2.5 AH.

In 24 hours, it uses 60 AH. The, always on, inverter uses 12 AH in the same 24 hours.

I am presently running on 800 AH of batteries. I shut down the charging source at 3 PM, yesterday. At 9 AM this morning, 18 hours later, my monitor was showing 80% charge. We watched Sat. TV last night and this morning, used lights as needed, kept 2 cell phone charged and made coffee, with a 700 watt Mr. Coffee, 3 times. We may have run the small Microwave for a minute or so.

Your 3 batteries should last, at least, overnight.

[RV Vagabond]

My question is based on SOC panel lights with FULL, 2/3, 1/3, EMPTY. With 3 months observation, it would not get down to 1/3 until around midnight. At sunrise it would still show 1/3, but twice it got down so low that it shut down the inverter, turning off my refrigerator. My solar would get it back to FULL before noon. Adding 2 batteries has not improved it as I was hoping to go to bed still at 2/3 and not get to 1/3 until just before sunrise.

[TQ60]

A short charge period indicates low capacity or huge charger.

Have the batteries tested and replaced if needed.

[Sehc]

Those State of charge lights are worthless. They really can't tell you anything about your batteries. If you connect new batteries with abused batteries the whole bank will be abused batteries. You could try giving each individual battery a full charge with a good battery charger.

[twinboat]

Originally Posted by TQ60

A short charge period indicates low capacity or huge charger.

Have the batteries tested and replaced if needed.

I agree. When they go down fast and then charge fast, the capacity is way down.

If you are running them until the inverter cuts off, that is pretty low.

Think of a battery as a bucket of water. You take 5 gallons out and put 5 gallons back in. Every time you run them down, it's like putting a hand full of dirt in the bottom of the bucket. Add 3 gallons of dirt in the bottom and the bucket will empty and fill faster. The lower you run them down the bigger the hand full of dirt you add each time.

[ByeTheWay]

I like the bucket analogy. Great way to put it.

I have always heard not to go below 50%.