12v questions for furnace in cold weather

[fmplatt530]

So I have a 100Ah deep cycle battery from walmart, and i've drawn it down to zero quite a few times in the last year since i bought it new. That being said, how many nights (in cold weather, like low 40s) should i be able to get out of running the furnace if battery starts fully charged?

Other things powered is the slide-out (multiple times) and the interior and exterior lights ( accidentally left the exterior night on all night the first of two nights). Last night I was super nervous my little kids would get cold so at 3am I hooked up the jumper cables from my tow vehicle to the trailer battery because the trailer battery gauge said "Empty". It was a long, stressful couple days at the in-laws for Thanksgiving.
I will start by taking the battery to get tested at auto shop as soon as I can, but wanted to ask this group anyway.

 

[Rich W.]

Even though you’ve provided more and better info than most, there are still too many variables (such as the quality of the Walmart battery, what you mean by “zero”, how many is “quite a few”, etc) to give you a reliable answer.

The best thing I can offer is this article on batteries: How To Maintain Batteries - Deep Cycle Battery Store . Equipped with this info, and doing the testing and monitoring that goes with it, you can do a pretty good job of predicting battery life, health, and usefulness.

Just shooting from the hip, given the info you provided, I’d be nervous too.

 

[fmplatt530]

Even though you’ve provided more and better info than most, there are still too many variables (such as the quality of the Walmart battery, what you mean by “zero”, how many is “quite a few”, etc) to give you a reliable answer.

The best thing I can offer is this article on batteries: How To Maintain Batteries - Deep Cycle Battery Store . Equipped with this info, and doing the testing and monitoring that goes with it, you can do a pretty good job of predicting battery life, health, and usefulness.

Just shooting from the hip, given the info you provided, I’d be nervous too.

Thanks Rich
Looks like you're in GV. Looking to take my trailer to a friend's place in Alta Sierra soon. We live in Woodland.

I'll get the battery tested and start looking at dual battery rack as well.

Cheers

 

[Rich W.]

Thanks Rich
Looks like you're in GV. Looking to take my trailer to a friend's place in Alta Sierra soon. We live in Woodland.

I'll get the battery tested and start looking at dual battery rack as well.

Cheers

I’m south/west of Alta Sierra, out towards the end of Garden Bar. I have friends in Alta Sierra - it’s a nice location.

Investing in good batteries and then being rather OCD about monitoring and caring for them will serve you well. Many people only get about a year out of their trailer battery(s) and consider this “normal”, but taking care of them will give you 3-5 years of service, maybe more.

If you need to replace your battery, my suggestion is to get the biggest US made AGM (or two as you mentioned) that will fit. Lead/acid batteries are ok, but require diligent maintenance so they are not as good a fit for the RV application, especially if you store it for extended periods.

Off shore manufactured batteries are a gamble, but you can get an idea of their quality by their weight which will tell you if they are scrimping on plate size.

 

[HughA]

Good day,
I just went thru a local power company black out. This is the second one in a month. I cannot make it thru the night without the battery going dead. I have one maintenance free deep cycle battery which is 5 months old. Sorry I don't remember the amp hr rating.
I suspect I use too much battery power even when the heater is off. So I recommend a battery monitor unit. I don't have one so I am guessing at whats using the power and have not found anything so far. I'm sure someone on the thread could recommend one. I was watching You Tube videos and they seem easy to set up if you are not buried in snow!

Hugh

 

[Rich W.]

Good day,
I just went thru a local power company black out. This is the second one in a month. I cannot make it thru the night without the battery going dead. I have one maintenance free deep cycle battery which is 5 months old. Sorry I don't remember the amp hr rating.
I suspect I use too much battery power even when the heater is off. So I recommend a battery monitor unit. I don't have one so I am guessing at whats using the power and have not found anything so far. I'm sure someone on the thread could recommend one. I was watching You Tube videos and they seem easy to set up if you are not buried in snow!

Hugh

I think commonly people barely get by with two batteries using a minimum of power just to run their furnace fans overnight. A monitor is good idea, but it wont help much if you are just relying on one battery.

Here’s a link to a reliable source for good, inexpensive battery monitoring stuff:

Battery Monitors

Any questions, just “Ask Randy”.

 

[TheLooks]

Good info Rich, I think every unit should have a battery gauge built in, mandatory. I have seen the little ones that plug into the 12v plug usually found around the tv. Any thing is better then just waiting for things to stop working.

 

[AbdRahim]

On my old class C, with two group 27 100 AH batteries, a few lights and fans without the furnace, and the batteries were down 50% by morning. I would not even attempt the furnace on just the battery. Lead acid batteries taken below 50%, shortens the battery life each time this is done.

The above article is essential reading.

 

[TheLooks]

Realistically, without many lead acid batteries this is why people move to Lithium. But the cost is enormous. But one good Lithium will replace at least 2 Lead acid or AGM's. Simply because they can be run down to 0% if you like. All the amp hours are available without major damage.

 

[gibsito]

Reminds me of myself about 14 years ago. I had one battery (can't remember the size) and an old 40-watt solar panel on the roof of my truck camper. I didn't know much about anything electrically-speaking, but knew I needed a solar charge controller between the panel and the battery. So I bought a cheap on/off controller (at the time all I knew was that it didn't cost much). After a few days out boondocking, my battery was nearly dead (well below 50%, I'm sure). I had some long jumper cables so I ran those from the truck's battery back to the battery compartment for the camper and left those connected for the 4-5 hour drive the next day. I was sure I'd be all charged up at my next stop. Lol. After running things for about 30 minutes it was down to where it had been the night before. That battery was soon worthless.

The following year I knew I didn't want to go through that ever again. I read up on solar, and put a system together while I was boondocking out in the desert. I bought two 109ah 6V golf cart batteries and wired them in series, put 190 watts of solar on the roof and bought a GOOD PWM charge controller along with a Trimetric meter to monitor the situation. Best thing I ever did. That system is still running today (almost 14 years later) and has never left me without power. Not even once. And the 2 six-volt batteries that are in it now have been there almost 8 years. They're getting weaker, but are still working.

You might want to look into something like this. It's such a relief not to have to worry about batteries going dead.