New Batteries Don't Last Long

Possibility #3 was also mentioned: failing batteries, so their capacity is lower now, even when fully charged.

But this is not always possible to fix, while #1 or #2 is.

From all the various messages, I get these two main things:

1) The batteries may or may NOT get FULLY charged
2) There are various loads on the batteries and it is unknown which of them has the greatest effect on the batteries

My friend will work on both of these items.

Thanks to all who replied for your time, knowledge, and suggestions.

Mex - yes, bad battery will fail sooner. Offtopic here - I recall a research by one boater, he found that deep cycle batts by West Marine brand lasted shorter than few other that didn't have any "marine" in their names :) ...

Bad batteries do not necessarily have to be bad right out of the box. They can fail prematurely. What I am suggesting is to assume nothing, suspect everything. But start with the basics.

full_mosey wrote:
It would be very informative to know Voltage readings BEFORE charging as that would help with confirming a 25 SOC%.

Yes. Check the voltage in the morning before charging, then charge, disconnect one battery and check the voltage on that disconnected battery after 24 hours.

He said that one battery lasts one day until the charge drops to 25% - it's not a good practice to let it drop that low, of course. Try not to run much lights and stereo on that day and don't open the fridge often, to prevent the one working battery from dropping too low, while the other one is resting.

Mex - he said the battery didn't behave like that before. Which might or might not be true, of course. He could've changed something in wiring, like inverter. We are guessing too much and this may go like that for another 4 pages. He needs to measure voltages before and after, WITHOUT LOADS, and measure the current that loads are drawing.

Start with the basics. I have seen many a bad batch of brand new batteries. Too many to simply asssssssssssume "new" batteries mean "good" batteries. Car jar batteries should be load tested as well as hydrometer checked.

It would be a shame to spend excessive time chasing ghosts. Assume nothing and you'll find the problem quicker, a lot quicker.

I think an ammeter will be needed to determine the draw. Especially at idle.

Most RVers seem to have OK luck with the WM batteries. Any chance they sat on the shelf too long? They may need some excercise before they reach full capacity.

A good hydrometer will take the guesswork out of how charged the battery really is vs how discharged during use.

There is no problem at all charging with both the portable and converter at the same time. However I would start an automatic portable first. The batteries will charge better in parallel. For best charging, the RV and portable should be connected + to one battery and - to the other battery to promote better balance.

I assume he has verified connections are tight and both batteries are actually supplying power.

Hi Ron,

Sometimes theory and practise don't fit too well. BFL13 has connected up to five external chargers at once. Some times he has to follow a particular order, but with only adding one charger that would not be a problem.

It likely the batteries need to be fully charged, equalized, and desulphated. This is best done on shore power.

Ron Nielson wrote:
I would think that this just wouldn't work correctly and that my friend should charge with either the external charger or the converter, BUT NOT BOTH at the same time.

It would be very informative to know Voltage readings BEFORE charging as that would help with confirming a 25 SOC%.

Many of us run our own tests with adequate metering to prove that our multiple chargers are cooperating. E.g., what were the charging Amps when the charger light indicated full charge? Also, after! I have observed my automatic charger charging after the light comes on. One useful measure of full charge is when Amps stop decreasing for an hour. That rate could be a good indication of a constant load.

This is most likely one of those mysteries that is most easily solved by taking the batteries out for professional testing.

I don't see any way to use this proxying to get anywhere soon.

My definition of marine is a battery that has been hardened for rough use. It does not mean deep cycle.

HTH;
John

The general populace has a pattern when it comes to batteries and their charging.

1. The alternator is a Magical, near instantaneous battery charger
2. When the green light goes on, the battery is fully charged
3. Since batteries are big and heavy, heavier than a wall outlet, they must therefore be able to store nearly unlimited energy.
4. Any dead battery need only be charged for 6 hours to return to 100% performance.
5. Wally world batteries made by Johnson control are the same JC batteries made for Interstate.
6. The word Marine in front of any battery means the battery has magical powers. It can store more energy, turn over any motor at any state of charge, and completely recover from abuse.
7. Your choice

The more knowledgeable on this forum can spend a lifetime negating 1 through 7, and there will always be someone who will ask a 6v vs 12v battery thread, because nobody nowhere has ever thought to ask that before, so why do a search and do some reading?

In regards to this thread, number 1 the batteries are not being fully charged in the time provided. The sum of all loads are unknown.
and Wally world Marine batteries are not trojans.

Sounds like they've been too deeply discharged too often and need a BFL13 treatment to get the SG back up into the green. Who knows how much capacity has been lost through the abuse of too deep a discharge and incomplete recharging.