House Battery Replace?

[pheasant16]

Greetings from ND. Winter's about had it and time to get camper ready for
use.
House batteries are about 6 years old, plugged in at home and at campsites.
About the only time they are used is traveling.
Meter shows they have about 75% when they've been off a shore line for 4 hours.
Water level is fine.
Should I be replacing them any time soon?
Camper is 97 vintage, so old lead acid or deep cycle
would seem to be best choices based on other threads.
New hip so now I can look for more little DIY things.

 

[Mark_K5LXP]

Wonder and guess, or measure and know. I have no idea what meter you're using or what exactly it's reporting. A static test won't tell you what you need to know. A timed discharge test will tell you the capacity of your batteries and take all the guess out of it. Many would say that at 6 years they're done, don't take a chance. Mine are on their 7th season and still test almost 100% - why would I replace working batteries?

A timed test amounts to applying a load 1/20th of what the batteries are rated for in Ah, starting a timer and seeing how long they will run the load until the terminal voltage hits 10.5V. A battery that can run the load 20 hours is 100%. If it runs 15 hours, they're 75%, 10 hours, 50%, etc. Once you know the merit of your batteries you can then decide if they're up to snuff or have already left the building.

Mark B.
Albuquerque, NM

 

[DonTom]

why would I replace working batteries

Since you asked . . .

Back in year 2020, my two six-volt Trojans were almost seven years old just before my trip to Death Valley. They were both working fine and well charged up before I left.

I was boondocked at the Sunset camp and after the 2nd night there, I had very low voltage and the genny could not charge them up much past ten volts. I then discovered one of the two six-volt batteries had a max voltage of four volts, showing a shorted cell. So I had to drive to the Wally*mart in Pahrump, NV to get a single 12-volt battery to replace them with.

When they are old, they can fail with no advance warning! So that is why.

Not long after, I changed the battery location and ran large cables to the battery box and now it uses a 300AH Lifepo4 battery.

-Don- Reno, NV

 

[Mark_K5LXP]

Anything can happen at any time. Probably safely argued cells can short on old batteries more often than new. But it's not a pervasive problem, of the hundreds of GC2's I've gone through it was a rare occurrence. What is more prevalent isn't a dead short but instead a cell that's been beaten to submission through hard cycling and lack of equalization over it's life, and has diminished capacity compared to it's neighbors. The battery seems to charge up OK and you use it that way, maybe you notice it doesn't seem to have what it used to anymore and maybe not, but that one cell is getting cycled more deeply than the others. It ultimately gets run to 0% a few times or reversed and then the egg is cooked - no matter how many amps you run through it, it will never charge much and just gets warm dissolving water. So it's attributed as a "shorted" cell but really it's just shot. A shorted cell is just that, a low impedance connection through the cell, that when you run current through it doesn't get warm and doesn't use water. A distinction without a difference, the battery is shot either way but the weak cell version of this failure mode is easily revealed through basic capacity testing before it fails. There is no doubt that my 7 year old GC2's are not what they were 7 years ago (higher peukert for sure) but at near 100% at C/20 they're healthy enough to trust, in my opinion. I suspect next season they'll exhibit some decline and at that point it's probably time to stick a fork in it but in my travels running through literally tons of lead acid batteries, well cared for and well performing batteries are pretty reliable at any age. Enough so that I won't replace based solely on "just in case".

Mark B.
Albuquerque, NM

 

[Domo]

Wet cell life is generally as 3-5 years, of course some go for seven years as cited by others.

At that battery age and with a new hip that might not enjoy manipulating heavy batteries, perhaps the question is wether you want to be somewhere and have a failure when it is NOT convenient, or remove a failure from your list of concerns...

My batteries are at five years and I watch them like a hawk in case I see bulging or low resting voltage that might mean sulfation, etc.

 

[Mark_K5LXP]

I watch them like a hawk

A capacity test will reveal when they start to decline or have issues well before the point of failure ("sulfation", et al). Some bulging of the ends over time isn't unusual, it's a consequence of the battery being cycled. Doing periodic testing can reveal charging or storage issues along with establishing the performance baseline. Far more batteries die of neglect or improper use than "bad" batteries. They're inherently pretty reliable, properly cared for.

I trust a new battery less than one that's been in service a while. It takes some number of cycles to prove there aren't any latent defects.

Mark B.
Albuquerque, NM

 

[Professor David]

All good points above. In my younger days, I would never replace anything until it was broken. However, peace of mind is worth a lot to me as I get older. Nothing wrong (and probably a good idea) with replacing any critical component when it is reaching its general life span like tires, batteries, and such.

 

[Gary RV_Wizard]

It's mostly a peace-of-mind decision. 75% (how measured?) isn't good but probably adequate for the use you described. 6 years is OLD for the common 12v marine/RV battery but not so bad if it's a 6v deep cycle and well cared for. You said "batteries" - is it a pair of 6v or multiple 12v?

I'd probably replace it cause it is gonna let you down if you actually need it sometime, e.g. you get stuck on a roadside somewhere or the RV park has a power outage.

 

[Mark_K5LXP]

it is gonna let you down if you actually need it sometime, e.g. you get stuck on a roadside somewhere or the RV park has a power outage.

I continue to beat the drum, measure and know vs wonder and guess. If I test a battery to 90%+ at the beginning of a season there is no doubt in my mind it will carry me through the season. Whether that's at a campsite or during a power outage is irrelevant - Ah's are Ah's. Cycle life is in hundreds, not handfuls of cycles. Even an old battery at 90+% has a lot of cycles left. Any battery suffering from "sulfation", stratification, paste shedding, grid corrosion, et al will not deliver 90+%, and there's your litmus test. 75% is a different story - that's on the steeper part of the degradation curve and at the beginning of a season I would think twice about just how far I want to push that set. So, 90% or 75% - big difference at 6+ years. But you don't have to wonder or guess - measure and know. Not only does it offer an opportunity of incremental savings by not abandoning serviceable units, you have confidence the lights aren't going to go out. That applies to any stage of service life. If my 2 year old batteries are wounded for some reason I want to know that too.

Mark B.
Albuquerque, NM

 

[DonTom]

I test a battery to 90%+ at the beginning of a season there is no doubt in my mind it will carry me through the season.

Exactly what I used to think, but I now know better. But I have even seen a new L-A battery do really weird stuff, such as go completely dead (zero volts right on the terminals) and come back to life in a few seconds at full power. Even NEW batteries can become intermittent. So I have my doubts with any L-A battery, but I would trust a five-year-old battery even less.

Many years ago, Tom was driving to work and stopped to get gas at a gas station after a good ten miles of freeway driving. After stopping, the windows would not roll up, car would not start. The five- to six-year-old battery had zero volts and never recovered a single volt. Totally dead. It started with a fast crank that morning before he left. Not the slightest symptom of anything being wrong with the battery.

Which reminds me--I need to replace the Engine battery in my Y2K RV as well as in my pickup truck. Both of them are more than five years old, but both are still working fine.

-Don- Reno, NV

 

[Kirk]

A timed test amounts to applying a load 1/20th of what the batteries are rated for in Ah, starting a timer and seeing how long they will run the load until the terminal voltage hits 10.5V.

While I very much agree with what you have said, very few RV owners have the equipment or the expertise to do that sort of testing A major factor in the lifespan of a lead-acid battery is the way that it has been treated over it's life. I suspect that a 97 year model RV that still has the original converter installed has received the best possible charge level maintenance when plugged in most of the time. Another factor is the degree of risk involved in not replacing the battery in question. If you never spend the night without shore power, the failure is not nearly as critical since the converter will still supply 12V power even with the battery removed. If it were me, I'd at least take the batteries to a battery selled that you know and ask them to load test them.

 

[Lou Schneider]

Exactly what I used to think, but I now know better. But I have even seen a new L-A battery do really weird stuff, such as go completely dead (zero volts right on the terminals) and come back to life in a few seconds at full power. Even NEW batteries can become intermittent. So I have my doubts with any L-A battery, but I would trust a five-year-old battery even less.

-Don- Reno, NV

On the first trip in my Safari Trek motorhome the starting battery did the same thing, went stone dead but it stayed that way. Fortunately I was able to hit the boost switch and start the engine from the house batteries.

When I replaced the starting battery after the trip I found it had full voltage and power on the top terminals but an open circuit going to the GM style side terminals - an internal open inside the battery.

That's probably what happened to you - an internal fracture that contracted and began conducting again when the battery cooled down.

 

[pheasant16]

Will take it over to Interstate to have tested when we get it back this spring. Prof David point that being older(me) and piece of mind is worth replacement. 75% according to the 97 model control center that tells you water tank levels, lp level, battery level is the only way I've ever tested it, and like Gary says not great but adequate if on shore power nightly. Terminals are all clean and water has been full when checked, usually monthly if I remember. Last summer was a challenge with arthritic hip. Yes still has the original converter humming all summer long at home and campsite. It's 2 12v lead acid.
Gramma doesn't like generator running EVER, so replacing batteries no matter what condition of current ones are is probably best outcome here.
I do so appreciate all the different ideas given.
Thanks guys.

 

[DonTom]

When I replaced the starting battery after the trip I found it had full voltage and power on the top terminals but an open circuit going to the GM style side terminals - an internal open inside the battery.

That's probably what happened to you - an internal fracture that contracted and began conducting again when the battery cooled down.

Yes, it was a GM battery with side terminals. Was in the late 1990's? Was that when it happened to you? Perhaps a bad batch?

I wasn't curious enough to look inside the battery to find the cause, but that sure sounds like the same issue. Either full power under full load or nothing at all. That was in my 1997 Saturn.

But I cannot remember what car Tom was using when his windows would not roll up. But I think it was a lot longer before, in the 1980's or so in a Chrysler. So that had to be a different issue. And that was an old battery, unlike mine that was only a few months old.

-Don- Reno, NV

 

[CharlesinGA]

My one group 24 battery was in the trailer when I bought it in 2019. It has worked fine, giving me power for one or two nights with no shore power (and not running the generator), however recently I noticed when I shut off the shore power and turned off the battery for a couple of days (while storms passed thru the area) the battery was close to 12 v when I turned it back on. Finally decided to replace it the other day with a Duracell AGM deep cycle.

I've changed batteries in everything I own in the past 6 months or so.

Charles

 

[Mark_K5LXP]

I have even seen a new L-A battery do really weird stuff, such as go completely dead

Acknowledged, first sentence in my reply "Anything can happen at any time". The point I'm making, and I have far more than statistically significant numbers to back it up, is a battery that has greater than 90% capacity rarely fails. The conditions that can cause sudden catastrophic failure, while increasingly present as batteries get older, aren't yet significant because if they were, the battery could not inherently achieve that level of performance. Many draw a line in the sand at say 5 years or whatever but in my experience running these tests thousands of times over decades, the test reveals the stinkers. Show me a battery with a shorted or reversed cell and 99.5 times out of 100 that battery had already showed compromised performance. Just that few people periodically test and know that there's something up with their battery before the conditions converge and it craps out. If this was a complicated or difficult test you could make an argument for repair by replacement, but the test is trivially simple - why not?

very few RV owners have the equipment or the expertise to do that sort of testing

If you have a battery monitor that shows current and voltage and something to tell time, you have the equipment. If not, a $10 harbor freight DMM and a sun dial would work. The loads are what's already in the RV - fans, lights, TV. Determine the load you need per the Ah rating of the battery, come up with a combination of loads that achieves that level, then start the clock. Watch the meter until it hits 10.5V and look at elapsed time on the clock. It's that simple. You can do it any time, anywhere you want. For extra credit, every hour or so make a note of what the voltage is for future reference. That would allow you to compare to future tests and do an abbreviated test just as a quick check. Yep, most folks would rather buy new batteries than learn or do anything new. But beyond the economy of not replacing working batteries, doing this simple test you'd gain the confidence of the performance of any age or type of battery. You never have to wonder the first trip of the season if there's a problem - to include wiring and converter - or at a given load how long they can go. You have the numbers and don't have to guess.

Mark B.
Albuquerque, NM

 

[Adventurous Traveler]

To the OP, if it's not hard to remove the batteries and something that could be done at a campsite, run the batteries until they exhibit failure. You could run out to a Walmart (freshest batteries sold, I've read) and replace them. If it ain't broke, don't fix it.

I replaced my tow group 31 starter batteries two years ago in my motorhome because it was getting harder to crank the engine over, so I took that as a sign to replace them.

Now, my four GC2 Interstate house batteries have been in the rig since I bought it in 2019, and they are not easily accessible to check water or anything else, but they seem to be working fine up to this season, so I'll be keeping an eye on them.

 

[Scarypat]

I’m a newbie here (just bought a new to us 2005 Newmar Kountry Star DP) and I’m farther along the dead part than the OP. re. my house batteries. The ex-owner never put water into them so they are completely shot. i could waste my time and try to add electrolytes then desulfate them with my shop repair charger. I’m not willing to spend the money on lithium yet, mostly because of the cost, all the asides you need to add to make sure you don’t overcook your alternator and the special winter care you need to take = I live in Quebec, Canada. I’m a cheap b*st*rd, so I’m looking at the best bang for the money in term of house batteries. One of the constraints I need to answer is that the ex replaced the standard LP/120 fridge with a house Hisense fridge. I’d like to have enough battery power to run that fridge without using the genset 24h when boondocking in Harvest Host stops. If the set-up would run the fridge and few other things for 12 hours at a time and have some reserve to run other things, that would work.

I’m considering a 4 x 6V set-up. What would be the minimum Ah per battery I need to look for? I suspect the fridge to pull 600w when the compressor is running, with probably a 800W peak at compressor start. I have a Magnum 3000w inverter, and a 200w solar which is currently only hooked up in a way to run a TV set-up - I don’t even know what battery is there to balance that load…

 

[Mark_K5LXP]

The startup current isn't significant because it's so brief. It would be useful to get some actual data on the fridge as WAGing it could send you down an energy use rabbit hole. 600W sounds too high. That's a nominal 50A draw which is a C/10 load on 2 pairs of GC2's. WAG fridge duty cycle of 50% and decent GC2's would make it about 16 hours. If you need a little more capacity and have the vertical room you could go with slightly taller batteries and pick up 10 or 20% with the same number. But before you get too far get some hard watthour numbers on that fridge so you can get a better read on operating time.

Mark B.
Albuquerque, NM

 

[Adventurous Traveler]

Scarypat's Newmar should have come with four GC2 batteries already, and he already has a nice 3000W inverter.

My Sportscoach has four Interstate GC2 batteries rated at 200ah each and a Magnum 2000W inverter. Our rig has a GE 19.5-cube residential fridge. We haven't had any problems overnighting at HH or Walmarts and other big box stores. We camped for 5 nights at a NYS state park with no hook-ups and did fine. What we do for overnights is turn the fridge down to its lowest setting before bed. By doing this, we rarely hear the fridge compressor run. For longer no-hook-up stays, we'll turn off the fridge when we go to bed, and the first one up turns it back on. At night, if we're making dinner in the RV, we'll run the generator for as long as we need it, and then in the morning, we'll turn it back on to make coffee.

Contributing on forums like this and others and watching YouTube RV'er videos, all the talk is about lithium and solar. If we lived out West with the plethora of boondocking locations or spent more travel time seeking out similar spots in our travels, maybe my DW and I would spend the thousands of dollars needed to upgrade, but for us, our old style GC2s and generator work out just fine.