extra house battery

[Dayhiker]

I know nothing. Here goes.
I could buy a car jump starter that has its own battery. It would connect by its cables to a car's battery to allow car to start when battery is dead.

Why could I not attach the jump starter to my house battery on my popup when it is low and I have no hook ups. I want to run the furnance tonight but a afraid there won,t be enough battery to lower my electric roof tomorrow. Wouldn't the house battery draw from the jump starter battery as the furnance fan cycles on and off? Wouldn't the house battery draw from the jump starter to run the electric roof ?

I am really trying to ask if it would work. I don't need to know how. Of course the jump starter battert needs to have enough amp hours to provide.

I have not seen a jump starter that has an attached trickle charger in a size for by small subaru outback.

Thanks all y'all

[Willhound]

No reason it wouldn't work. A jump pack is meant for a high amp short term draw for starting a vehicle, but yes, will provide 12 volts to run your furnace and your roof.
I wouldn't hook it up until you actually need it though. Unless you've been boondocking with no way to recharge the house battery for a long period of time your furnace will run for days without killing a properly charged battery in good shape. Now, if running a fridge, lights and other stuff that could change.So have it as back up, but don't hook it up until needed. Many have a 12 volt adapter that allows you to recharge from a 12 volt power outlet on a vehicle when running.

[bikendan]

Moved thread from the TT/5th Wheel section's Flagstaff sub-forum to the Tent Camper and Popup section since the OP has a popup, not a TT or 5th Wheel.

[RobbieH]

This is exactly what they do at RV dealerships. They take the batteries off the trailers (theft you know) and then attach a jump pack when someone wants to see the trailer. At least that's what I see where I've been and on YouTube where dealers are showing off new models.

[Aussieguy]

for the same price of that small jump starter you can buy a 12v 100ah Lithium battery

i got this 2 of these ... it has bluetooth so you can see state of charge etc
https://www.amazon.com/Elfhub-Blueto...6004361&sr=8-7

works well
I run my 12v fridge + furnace and all the other 12v stuff I need for camping

One of these will probably do you BUT you still have to find a way to recharge it the next day

I got solar ... 740w of panels gets my battery recharged by 2pm next day
you can probably put a couple of solar panels on your popup?

otherwise you need to get a dc-dc charger or something to allow good charging from your truck alternator

Or a small generator

Or you have to mooch dock ( some shorepower)


Edit additional
2 batteries will allow you a weekend away and then you can charge up at home

[Reverse_snowbird]

My jump start battery will do what it's designed to do.... provide enough charge to get the car battery started. Now mine is pretty basic and doesn't have enough a large battery.
It wouldn't have enough charge to recharge the battery to full charge.

A more reliable method would be to buy a second battery - any type would do, but lithium would probably more reliable. You can totally discharge them without killing the battery like a lead acid.

[tomkatb]

Modern rv’s are getting complicated.

New units are power hungry.

Frankly you need to learn a lot about batteries.

Likely you have the little car battery. Running out of power will happen.

You need a lithium battery with a blutooth battery monitor.

No more flying while blind. You could read power available on your phone.

I would recommend 200 ah. That large you need to make sure it fits somewhere. Plenty of reserve power. You could boondock several nights. 100 would work.

Those jump starters are small batteries. It might not be enough.

Attaching the jump starter to your battery for more than a jump is risky. Parallel batteries need to be matched. The good one will try to charge the weak one. Might not work out well. Likely you would get two weak batteries.

Pricey for what you get.

[bikendan]

The OP has a small popup, pulled by a Suburu. So not much power hungry unless the OP has a 12v only fridge.

[flyflotrtim]

Good Advice above. The car jump battery will be expensive for the amps you get. We don't know what your current battery is but a LiFePo4 battery would give you lots more amps and would be my first consideration. A portable solar panel (solar suitcase) would be a second consideration. A new battery or solar suitcase would each cost a bit over $200

[Reverse_snowbird]

Originally Posted by bikendan

The OP has a small popup, pulled by a Suburu. So not much power hungry unless the OP has a 12v only fridge.

True, but he's planning on running the furnace.

[Aussieguy]

Lifepo4 is the way to go... proven technology

the real question is how long do you camp... to determine what battery size you need

100ah would work for a weekend then adding the solar panel (or 2 panels) would allow some extra days

furnace only pulls about 3 amps..... 12v fridge 5 amps
Run cycles vary by location and temp ...

camped 3 adults with furnace on + the fridge ... used about 30-40% of my 200ah bank .. so if you only get a 100ah battery it would equate to 60-80% .

Perfectly doable ....
I tried turning on lights, furnace, fridge, shower vent, stove exhaust fan and waterpump only saw 10 amps getting drawn from battery...

[Bob K4TAX]

Just remember, most of those jump start devices are used as high current one-time demand devices. Then ask yourself, does this device and method meet my power demands?

Maybe after your house battery is discharged to the point it won't allow lowering the roof tomorrow morning. Why not just connect the tow vehicle and allow it, with the engine running, to provide enough energy to lower the roof? Seems like a very reasonable approach.

More importantly, one needs to know the safe discharge percentage of the house battery. Discharge it too much and likely or eventually permanent damage occurs and one will be replacing the battery. Here are a couple of charts that apply to the type of battery you may have.

Bob

[Dayhiker]

Thanks to all for your comments and suggestions. I will plan short duration camps without shore power so the house battery will be enough. My AGM battery holds 81 amps so could potentially run a furnace overnight for 2 or 3 nights since the furnace would only run part time. I have 100 watt roof mounted solar but limited experience with how much power I can "harvest" with it.

I see now I didn't give enought info originally. My lack of experiende is showing.

Thanks again. Happy Camping

[Bob K4TAX]

Originally Posted by Dayhiker

Thanks to all for your comments and suggestions. I will plan short duration camps without shore power so the house battery will be enough. My AGM battery holds 81 amps so could potentially run a furnace overnight for 2 or 3 nights since the furnace would only run part time. I have 100 watt roof mounted solar but limited experience with how much power I can "harvest" with it.

I see now I didn't give enought info originally. My lack of experiende is showing.

Thanks again. Happy Camping

If your AGM battery is rated at 81 aH, you can only use 50% and feel safe about not damaging the battery. If your AGM is 160 aH rated, then about 80 aH is useable.

If it were a LiFePo you could use nearly 100 % of the aH rating and not damage the battery.

I doubt that one could rely on running the furnace for 2 or 3 nights reliably without some assistance from "ol sol" in the sky.

Bob

[tomkatb]

Historically in North America solar panels installed flat on the roof, on their best day, can supply 25 ah of battery per 100 watt panels. Typically the size manufacturers instal as a learning device for the owner. Will keep the battery up over the winter, maybe. The farther north you are the poorer the performance. Trees, clouds and rain are the enemy.

If you have a compressor fridge an 81 ah battery will be nearly dead the next morning. Use the furnace and the DW will be talking to you about 1 am.

When we had the battery failure I first plugged the TV to the rv. We could not use any lifts or slides. Typical output thru the 7 pin plug is minimal.

We got the generator out to power up the converter. About 50 amps dc.

Jumper cables from the tv would work. Plan ahead.

As most rv’s sold today are intended to be plugged in every night. There are exceptions. There are optional batteries available at the dealer. You got the little Walmart special car battery. Likely free.

.

[jlynn721]

Originally Posted by Dayhiker

I know nothing. Here goes.
I could buy a car jump starter that has its own battery. It would connect by its cables to a car's battery to allow car to start when battery is dead.

Why could I not attach the jump starter to my house battery on my popup when it is low and I have no hook ups. I want to run the furnance tonight but a afraid there won,t be enough battery to lower my electric roof tomorrow. Wouldn't the house battery draw from the jump starter battery as the furnance fan cycles on and off? Wouldn't the house battery draw from the jump starter to run the electric roof ?

I am really trying to ask if it would work. I don't need to know how. Of course the jump starter battert needs to have enough amp hours to provide.

I have not seen a jump starter that has an attached trickle charger in a size for by small subaru outback.

Thanks all y'all

Unless you already own a jumper box, don’t waste your money. Buy a generator and a gas can. You’ll be much better off.

[mnoland30]

My jump starter has a 20AH battery inside. I hooked it to a car with a dead battery, and was able to drive about 3 miles before it ran down. The dead battery pulls lots of current to recharge itself and empties the good battery.

My friend with a popup would hook his vehicle to his trailer with jumper cables to recharge his battery. That is an expensive way to charge, but it worked. It definitely would work to lower the unit.

I have a 100 watt solar panel with extension cord that I can aim at the sun. That works much better than the roof mounted panel.

When we camp, we use sleeping bags. The furnace wakes me up when it comes on, and at my age, I don't get back to sleep. The furnace is the only big load you have, assuming your fridge runs on propane.

[Chuck_S]

Off grid or dry camping can use a lot of power in cold weather. My refrigerator runs on 120vAC or propane so the furnace in my Roo is the biggest power draw.

The universal Group 24 lead acid battery only provides roughly 56 Useful Amphours of power before the voltage under load drops below the point anything will run. Useful Amphours (a conservative rule of thumb) can be estimated by the formula RC/2.4 = UAh.

The furnace in my Roo uses pulls 3.34amps or 3.34 Ah every hour of flame time while burning a pound of propane at the same time.

While a 20 pound propane cylinder is good for 20 hours of heat the furnace will consume 66.8 amphours of power to so it. In other words I'm more likely to run out of battery power well in advance of running out of propane.

Keep in mind the furnace does not run 100% of the time. The pair of T145 Golf Cart batteries on my trailer tongue provide 221 UAh a number I consider essential for our camping style. This much power can be provided by Lithium as well albeit at more expense but less weight.

"I wish I had less battery capacity." said no one ever.

-- Chuck