Suburban RV furnaces s*ck!

[mossemi]

Would it make sense to try running the furnace on another battery, to verify your latest findings.

Mossey

[Rivernerd]

1 hour ago, routlaw said:

Suggestions and thoughts appreciated. 

Regardless of whether the furnace runs on another set of batteries or not, you should replace your 7-year-old wet cell batteries.  They are the same type of battery used on most cars and trucks.  I have never gotten as much as 7 years out of such a battery without failure.  Of course, the failure usually occurs in cold conditions, consistent with your report.

With regard to your 12.7V readings, old lead acid batteries sometimes give unreliable readings.  I expect new batteries will solve your issue.

[routlaw]

58 minutes ago, mossemi said:

Would it make sense to try running the furnace on another battery, to verify your latest findings.

Mossey

It probably would, but the logistics and effort of removing 4 Trojan T-105's just to install one single 12 volt batter of known quantity would be a major PITA. And @Rivernerd makes a good point about their age as well. Thanks

[routlaw]

45 minutes ago, Rivernerd said:

Regardless of whether the furnace runs on another set of batteries or not, you should replace your 7-year-old wet cell batteries.  They are the same type of battery used on most cars and trucks.  I have never gotten as much as 7 years out of such a battery without failure.  Of course, the failure usually occurs in cold conditions, consistent with your report.

With regard to your 12.7V readings, old lead acid batteries sometimes give unreliable readings.  I expect new batteries will solve your issue.

Well there are some technical differences with the 6 volt Trojan T-105 compared to auto/truck batteries. Its my understanding they really are made to a different level with deep cell technology and are meant to last a longer time… maybe. Just had to replace my truck battery this past summer after 8 years of use. And you are correct colder weather puts far more stress on a battery than 60 or 70 degrees. First time I'v heard of unreliable readings for wet cells though, wonder what might cause this anomaly. Thanks

[mossemi]

11 minutes ago, routlaw said:

It probably would, but the logistics and effort of removing 4 Trojan T-105's just to install one single 12 volt batter of known quantity would be a major PITA. And @Rivernerd makes a good point about their age as well. Thanks

I agree that you got pretty good service out your stock batteries, much better than I did.  But I blame myself for their short life span due to poor maintenance.  Although only one of my four batteries tested as failing, I replaced them all.

As far as removing four 68 lb. batteries being a PITA, I totally agree.  I was actually thinking of removing the main positive and negative cables and using jumper cables to connect them to a single 12v battery, like the new one you just put into your truck.

As far as the 12.7v reading goes, it would probably be more accurate if you checked the voltage again after a full charge and then allowing them to rest for about 6 hours.  

But I understand your position.

Mossey

[SeaDawg]

Funny, I was just out in my trailer this morning,  checking some things out, and I was going to ask you what your battery levels were. Now, you've solved the mystery, all on your own. Good on you.

I have friends with a 2009 who still have their original Trojan wet cells in service. (They maintain meticulously, and are plugged in through storage, and most of the time, camping as well.) Theyve defied all odds, imo.

Me? 99 per cent boondocking, solar charging. On our third set of batteries. Our two Deka/east penn agm group 31s are in their 5th season. Hoping for a few more. Fingers crossed. Batteries are so expensive. I  feel your pain.

 

[routlaw]

45 minutes ago, mossemi said:

I agree that you got pretty good service out your stock batteries, much better than I did.  But I blame myself for their short life span due to poor maintenance.  Although only one of my four batteries tested as failing, I replaced them all.

As far as removing four 68 lb. batteries being a PITA, I totally agree.  I was actually thinking of removing the main positive and negative cables and using jumper cables to connect them to a single 12v battery, like the new one you just put into your truck.

As far as the 12.7v reading goes, it would probably be more accurate if you checked the voltage again after a full charge and then allowing them to rest for about 6 hours.  

But I understand your position.

Mossey

As I was writing my reply it occurred to me that was your intention, use the Truck with jumper cables to connect. Unfortunately due to where I live this is near impossible without dragging the entire affair to a parking lot of sorts. Live in an older historical neighborhood and the access just doesn't allow for a side by side setup like that. Good idea though. FWIW I have checked the voltage reading with several intervals after a charge. Last two nights I wanted to immolate what it would be like on a boon docking trip using solar in the day by taking camper off shore power at sundown, check voltage first think after sunrise, then try and start furnace. Got 12.7 volts, furnace would not start until I plugged into shore power again then furnaces starts up immediately. 

[routlaw]

36 minutes ago, SeaDawg said:

I have friends with a 2009 who still have their original Trojan wet cells in service. (They maintain meticulously, and are plugged in through storage, and most of the time, camping as well.) Theyve defied all odds, imo.

Me? 99 per cent boondocking, solar charging. On our third set of batteries. Our two Deka/east penn agm group 31s are in their 5th season. Hoping for a few more. Fingers crossed. Batteries are so expensive. I  feel your pain.

 

2009 amazing, and there in lies the difference. I have not been that meticulous about the battery maintenance. FWIW I have called both Trojan and Lifeline battery companies and both companies have stated I've done well getting 7 years out of these.

To add to that after charging again all day, unplugged battery power started furnace quickly @ 13.0 volts SOC, turned off furnace for a few minutes, SOC @ 12.8 volts and again furnace starts and its freezing cold here with snow now coming down. Did the same thing a few times on Sunday with same results. Looks like time to buy new batteries, because its obvious @ 12.7 volts these batteries do not have enough left to power the fan motor properly. 

1st World problems, we should be so luck. 

Thanks

[SeaDawg]

41 minutes ago, routlaw said:

Got 12.7 volts, furnace would 

12.7 in old weak batteries can drop very rapidly. 

The shore power test you've done probably tells the story, imo.

[topgun2]

So - 

Is it that furnace that s*cks or is it those 7 year old batteries that s*ck? Or both? 😁

Bill

p.s.  sorry - but I simply could not resist. 

My T-105's are also pushing 7 years and I'm hoping to get one more year out of them.

[SeaDawg]

4 hours ago, Rivernerd said:

They are the same type of battery used on most cars and trucks. 

With all due respect,  and you didn't have prior knowledge,  he has trojan t105 batteries, designed for golf carts and rvs, etc. Dedicated deep cycle, not starter batteries. Thicker plates, longer life, deeper discharge.

7 years isn't a bad run. Might be better, but not bad at all. Could be worse, too.

I'm a bit confused,  though. 12. 7 is pretty much full, shouldn't cut off the furnace. Mine runs til much lower, maybe 12.2? Can't remember, as we don't normally let batteries run that low. (That's how we depleted the life of first lead acid  set, in less than a year. 😒. I had to fly out for a family emergency, my husband didn't have my help in monitoring battery status, and it was cold, furnace running, no solar then,  etc. Toast.)

But, if batteries are at end of life, they'll show 12.7, then drop rapidly under load, such as the fan running, to the point where the furnace won't light off. Like @mossemi suggested. 

We routinely get at least 5 years, often more, from batteries.  Even with our heavy use.

 

[routlaw]

50 minutes ago, topgun2 said:

So - 

Is it that furnace that s*cks or is it those 7 year old batteries that s*ck? Or both? 😁

Bill

p.s.  sorry - but I simply could not resist. 

My T-105's are also pushing 7 years and I'm hoping to get one more year out of them.

LOL😂 probably both!

Seriously I stand by my initial statement the Suburban furnace is truly a piece of work which only a deeply troubled mind could have designed and invented. Would like to think the Attwood's are at least a modicum better. Good luck getting past 7 years with yours, hope you succeed. Truth be told based upon my testing while the weather was a bit milder I could probably push it and get at least another summer season out of the ones I have. Doubt they would hold up to a fall season though. 

[routlaw]

27 minutes ago, SeaDawg said:

I'm a bit confused,  though. 12. 7 is pretty much full, shouldn't cut off the furnace. Mine runs til much lower, maybe 12.2? Can't remember, as we don't normally let batteries run that low. (That's how we depleted the life of first lead acid  set, in less than a year. 😒. I had to fly out for a family emergency, my husband didn't have my help in monitoring battery status, and it was cold, furnace running, no solar then,  etc. Toast.)

But, if batteries are at end of life, they'll show 12.7, then drop rapidly under load, such as the fan running, to the point where the furnace won't light off. Like @mossemi suggested. 

We routinely get at least 5 years, often more, from batteries.  Even with our heavy use.

 

I hear what you're saying on these numbers and in fact in the past even with less SOC these same batteries would run the furnace. In milder temps at 12.7 volts once the furnace motor started it would immediately drop to 12.5. I was reading earlier today on the boondocks bible website where aging batteries might not have the ability to fulfill a heavy amp draw even though the battery might be charged. Not sure what to make of this, and at least one of the owners stated on his own website (boondoctor.com) lead acid batteries should be drain to 10.5 at least once per year. As you might imagine when asking about this to Trojan and Lifeline results were a bit different. 

One would think as old as this technology is, there would be no debated about how to maintain them, but this is not the case. I'm inclined to do AGM's but there is not a lot of reputable brands to choose from up here in the Northern Hinterlands other than Interstate Batteries. Shipping on 280 lbs worth of batteries has to be pricey these days.

[SeaDawg]

I personally think the "drain to 10.5" is a ridiculous and very harmful Idea. Asking for trouble, as the battery is pretty much dead at 10.5. 

The drop on the seelevel from 12.7 to 12.5 is expected, under load. A good battery will bounce back, not under load in 20 to 30 minutes. The load applied lowers the voltage numbers, and the furnace fan is a big load.

[Rivernerd]

7 hours ago, Rivernerd said:

They are the same type of battery used on most cars and trucks.  I have never gotten as much as 7 years out of such a battery without failure.

By the phrase "type of battery" in the above-quoted comment, I meant lead acid type, as opposed to lithium type, not car-type lead acid vs. deep cycle lead acid.  

All lead acid batteries, even deep cycle ones, are beyond their useful life at 7 years.  "Most deep cycle batteries can last up to six years with proper care and charging (depending on the frequency of use). " 

https://www.mkbattery.com/blog/how-extend-deep-cycle-battery-life

 

[routlaw]

18 hours ago, SeaDawg said:

I personally think the "drain to 10.5" is a ridiculous and very harmful Idea. Asking for trouble, as the battery is pretty much dead at 10.5. 

The drop on the seelevel from 12.7 to 12.5 is expected, under load. A good battery will bounce back, not under load in 20 to 30 minutes. The load applied lowers the voltage numbers, and the furnace fan is a big load.

This is exactly what I have always thought or been taught too. I will go ahead and post the link to the article keeping in mind I am not promoting this idea or this person just supplying additional information on battery maintenance.

https://www.boondoctor.com

The above is the general website address where you can find numerous articles or blogs this fellow has posted.

https://www.boondoctor.com/knowledgebase/how-far-to-discharge-your-lead-acid-rv-batteries/

He certainly seems to know much more than I do regarding RV boon docking and associated battery information. The article above certainly flies in the face of conventional wisdom. 

[Chukarhunter]

You may have already checked this possibility out but if not, you may want to check the wiring on the back of your thermostat.  The wire to the furnace fan seems to be working fine but if your thermostat has a separate wire that goes to the furnace igniter, this wire connection could possibly be loose or corroded.  In that case, you will get higher resistance across the wire terminal on the back of the thermostat.  It could be that 12.7 volts from the battery is insufficient to overcome this higher resistance.  When you plug into shore power, the converter (or inverter/charger) will immediately send 13.4 volts or more to the battery and will pass that higher voltage through to all the 12 volt circuits in the trailer including the thermostat.  This may be just enough of a voltage increase to overcome the resistance of a bad thermostat connection and would explain why the furnace works on shore power and in warmer weather. 

It is a long shot, but cleaning and re-tightening the wiring connections on the back of the thermostat might solve your problem.  If nothing else, it rules out yet one more possibility.

[routlaw]

@Chukarhunter sounds like a plan, worth a shot and should be a quick and easy investigation. I will say this thus far I've seen no corrosion at all on any of the wiring throughout the camper. Thanks