Battery Maintenance

[Persistent]

The battery with two cells dry is suspect as you suggested. The plates corrode when exposed to air. The longer the exposure, the more the corrosion. How long was it exposed? How much was exposed?

Recharge them separately or together. Not much difference when two 12 volt batteries are charged in parallel.

Recheck water level after charging. Always check water level after charging. Filling before charging can lead to overflow while charging. Plates must be covered when you start charging.

Test them. It is more reliable than guessing. Taking the battery to the auto-parts store for a quick test is OK. There are several quick test methods. A quick test will reveal a seriously deteriorated battery quickly. The methods are not particularly accurate.

For more accurate results use the 20 hour discharge method. Measure the current and how long the voltage stays above 11.4 volts (10% SoC or State of Charge).

Start by fully charging the battery for a long period. It takes 14 to 18 hours charging at 13.6 volts to fully charge a lead acid battery.

Let the battery sit disconnected for 4 hours. Static voltage should be above 12.7 volts to start. Static means not charging or discharging for about 4 hours. Check water level after charging.

Try to discharge the battery at its 5% rate. That is 5% of capacity every hour. Try not to discharge below 10% SoC.

So a 100 amp hour battery should be discharged at 5 amps and should last for 18 hours. It should be about 11.4 volts static at that point. You should get 90AH with 10AH remaining in the battery.

Current in Amps time Hours equals Amp Hours or AH.
EX: 5A X 18H = 90AH
6A X 15H = 90AH
4A X 22.5H =90AH

The test would be more accurate if charging and discharging is done at approximately room temperature. However, you do not need a precision test here to see if the battery is still usable.

[HopsBrewster]

When you keep a charger connected in the off season, in this case your converter, you should check the water levels before connecting then recheck them at least monthly.
If the 2 dry cells were completely dry it is possible they're shorted. You should be able to take your batts to the local RV repair shop and they can test them.
As mentioned earlier, you could use a hygrometer to check the specific gravity of the fluid. If it's too low you could add some acid.

[RoadEyePie]

I've ordered one of these hydrometers.

https://www.solarpanelstore.com/prod...hoC0AYQAvD_BwE

We'll see if the link works.

[RoadEyePie]

Originally Posted by HopsBrewster

When you keep a charger connected in the off season, in this case your converter, you should check the water levels before connecting then recheck them at least monthly.
If the 2 dry cells were completely dry it is possible they're shorted. You should be able to take your batts to the local RV repair shop and they can test them.
As mentioned earlier, you could use a hygrometer to check the specific gravity of the fluid. If it's too low you could add some acid.

When at home, the RV is stored under a roof / pole bldg. and plugged into 50 amp shore power. I'm trying to learn more about the converter installed in the Beacon. Not much about it the manual. Someone said I should make sure the converter is a 3 or 4 stage converter. I don't know how it works, but it seems that it has to be a smart device in order to not over charge the batteries, running continuously. Don't know how to tell if the converter is the reason why the relatively new battery had 2 dry cells. Why can't I just ask Alexa all these questions, she's so dam smart.

[Mark_K5LXP]

Unless your battery has a hole in it, the only thing that can cause water to dissolve is an elevated voltage from a charger over a prolonged period of time. So that implies something's up with it. Not that it's "bad", it may be working exactly as designed. Problem is, the less sophisticated ones don't treat batteries well. Or if it's a more sophisticated one, perhaps there's a wrong setting or temperature sensor out of whack. Watching it charge the batteries to see if it's providing the proper profile for your type of battery will reveal what the specific issue is.

There is no question any cells that dried up will be compromised, the question is how badly. Part of the capacity equation is expectation. Do you care if you lost some percentage of capacity? Some folks proclaim how their batteries lasted 10 years or whatever but the reality of that is they can get by with a battery with very little capacity, because after 10 years no battery meets spec anymore, but it might be "good enough". What number would you put on "good enough"? Running the capacity test mentioned above removes all doubt about battery merit and is simple to do. As a plus, after you run that test you can test your charger to see how it brings them back up. With two simple tests you can prove the merit of your batteries and know if your charger is having an issue. A much better way to go than wondering and guessing.

Odds are excellent you don't want to bother with all of this. Who wants to dive into the minutia of battery charge profiles and capacity testing? If not, buy some new batteries and resolve to check water more frequently and get on with your life. But know that you don't have to wonder about the state of your batteries, there's simple tests to run and tons of good info on the internet (and here) about the care and feeding of batteries.

Mark B.
Albuquerque, NM

[153stars]

The batteries act like a big filter /capacitor. A convertor or charger makes DC from AC with diode bridge , trio or rectifiers put out pulsating DC the better the stand alone convertor without a battery the cleaner the DC output . A charging convertor may not have clean DC. I would very leery of removing the battery as a large capacitor to clean up DC output. In some sort of real emergency situation I would still avoid it, by using any battery I could get my hands on or tie into chassis battery as my filter. Most invertor chargers wont put out DC without 7 to 8v on the batteries already. I could wrong the output could nice and clean just too much risk .

Originally Posted by RoadEyePie

Sorry, I did NOT connect the pos. & neg. together. I connected all the leads together just as they were when connected to the batteries. All pos. connected then all negs. together.

I assume every RV out there has to have a converter. It converts 120v AC to 12v DC to charge the batteries when plugged into shore power.

[twinboat]

Originally Posted by 153stars

The batteries act like a big filter /capacitor. A convertor or charger makes DC from AC with diode bridge , trio or rectifiers put out pulsating DC the better the stand alone convertor without a battery the cleaner the DC output . .

Yet the manufactures install a battery disconnect switch that removes the battery from the converter output, leaving it to power all of the 12 volt stuff.

Power converters have been outputing clean DC power since the 90s.

https://www.progressivedyn.com/servi...ked-questions/

[Persistent]

Adding acid to a used lead acid battery to correct the specific gravity is not recommended. Only add distilled or de-ionized water.

The two cells referenced had water level below the top of the plates. I am not sure you can say it was dry to the bottom. The acid stays even if the water "boils" off. Just add water.

Adding a half gallon of water to a battery bank indicates all batteries were low on water. Two cells were apparently lower than the others.

All batteries low on water means water has been electrolyzed ("boiled", actually converted to hydrogen and oxygen). Charging lead acid batteries does this normally.

When charging according to recommended voltage profile, minimal water is consumed. When over charging, large amounts of water are consumed. In all cases, check water level after charging. You will get a feel for how much your batteries consume using your charger.

Adding water to full mark before charging can lead to spilled acid do to overflow. However, make sure the plates are covered before charging.

[bucks2]

I run a bank of 10 deep cycle batteries in my boat, 4 deep cycle in my MH. I've been RVing for 41 years running deep cycle batteries. Having said that, I'll tell you what I'd do, from experience.

Since you don't know how long the batteries were low on water. You don't know how long they "cooked" without water. You had to put an excessive amount of water into the batteries to get the plates wet again. The battery(s) are most likely junk.

You can charge them up and give it a try, but....... if you get out camping and the batteries don't last but 2 hours, will that ruin the weekend? Will you be in a place where it's convenient to go buy batteries and install them? You know of course that brand new batteries might not even be fully charged when you buy them, so even that option isn't a perfect plan.

If it were me in that position, I'd just go buy 2 new batteries, put them in when/where it's reasonably convenient, put the maintenance charger on them and remind myself to take better care of them next time. This way you know they'll work properly when you go to use them next. Enjoy using your RV, don't let questionable batteries ruin a trip.

[hamm2018]

Originally Posted by RoadEyePie

My two 12v batteries in the 5th Wheel are about 2 years old. I decided to pull them out for the winter. RV is under storage (roof only) and plugged into 50 amp service. When I opened the caps on the batteries, one of them had two dry cells. I put 1/2 gallon of distilled water in both batteries, all (6) cells and started them on a 2 amp 12 volt slow charge. Is the one battery with the dry cells likely no good or should I be able to recover it. I know it's possible to get a battery voltage up, but when put under a load, it doesn't hold up.

Also, I turned off the AC breaker 120 v to 12 v converter so it isn't running (hopefully). Everything else should be ok to run just using the 50 amp shore power? Guess I'll find out.

For me a good rule is how much of the battery's plates are exposed is how much you damaged the plates. So if 1/2" of a plate is exposed, you lose that 1/2" for holding a charge.
A method I check my battery voltage is using a multimeter place 1 lead on the terminal and then dip the other lead into a cell. See what each cell reads. If it is down in the 1. something range the cell could be damaged.
So if you already had it load tested and it does not hold the load/voltage it is done for.
You need the batteries to run certain systems in your rig, the batteries are part of the circuit. Especially for the leveling system, slides and 12 volt systems.
You replace one battery you might as well replace both and count this up to lesson learned. Check your battery water at least once a quarter, if not monthly.
I learned my lesson from the US Navy and doing the PMS System, Preventive Maintenance System. Being an electrician in the Navy we had a daily, weekly, bi-weekly, etc.... maintenance we had scheduled on various equipment on the ship. We also had to use certain grease, tools on this equipment. Make a list of your gear and set up a maintenance chart, then follow it.
For example:
generator:
monthly check: ____
oil level check: _____
annual air filter check: _____
annual check/clean terminal for starting: _____
annual spark plug check/replacement: ______

I have several 3 ring binders that I use to track my maintenance schedules,
weekly, monthly, bi-monthly, bi-annual, annual.

I know this got off track but it may help you out in the long run on keeping track of maintenance items.

[RoadEyePie]

Originally Posted by twinboat

Yet the manufactures install a battery disconnect switch that removes the battery from the converter output, leaving it to power all of the 12 volt stuff.

Power converters have been outputing clean DC power since the 90s.

https://www.progressivedyn.com/servi...ked-questions/

I thought the battery kill / disconnect switch removed all output from the battery to keep them from running down the batteries. And I assumed the converter would still supply a charge to the batteries to keep them from going dead.

[RoadEyePie]

I've learned that my converter is a Progressive Dynamic 4500 series (I think). Manufacturer tells me that it's a smart charger in that it doesn't continuously charge to the point of overcharging the batteries. So, I removed the batteries and reconnected all the 12v leads just as they were when connected, then turned on the 120v converter (at breaker box). My main control panel in the RV (controls everything) is reading 13.7v. Is that a good confirmation that the converter is working?

Well I guess confirmation was that all the lights came back on.

[twinboat]

Originally Posted by RoadEyePie

I thought the battery kill / disconnect switch removed all output from the battery to keep them from running down the batteries. And I assumed the converter would still supply a charge to the batteries to keep them from going dead.

That's not how most are wired. It does remove output but it also remove input.

Problem is that on some RV, the disconnect switch doesn't remove all loads. They may leave the safety devices still connected and there have been reports that the gas/electric fridge may be connected to the battery all of the time.

On my 2017 Thor Axis, the battery disconnect switch disconnects everything from the battery.

I later added solar and an inverter. They stay connected to the battery..

[Libero]

Think you might mean Hydrometer that measures specific gravity. A hygrometer measures moisture content. Usually used to check soil for water content.

Likely a typo or a product of an errand spell checker