How much battery do I really need?

[kb0zke]

I know, I should get a Kill-O-Watt and measure everything. I can also use the electric meter outside and check over a period of time to see what we actually use. That said, when we're boondocking we generally don't use the air conditioner or furnace, so the electric meter will give us numbers on the high side.


I had a pair of 24V (nominal) 200AH batteries in the previous trailer, so 9600WH total. That was more than enough. FWIW, when we bought the trailer two years ago we paid the dealer $2000 for a pair of 12V (nominal) 100AH LiFePO4 batteries. When we did the solar last year we pair just over $2000 for the two batteries I just mentioned. That was the Black Friday sales. Today I can get the same brand, 410AH (12V nominal) for the same price as the sale a year ago. I can get three 280AH batteries (same brand) for $1500.


So, do I really need that capacity? We are full-timers, not weekend campers, so we do need to be able to live normally. For us, that means using the microwave, coffee maker, and toaster oven regularly. What would your experts suggest?

[BGClassic]

Not an expert, but you can estimate your current draw just from the specs. We upgraded to 400Ah BBs for our Alaska trip. We could make it through the night, running the Norcold fridge, the Alde heat and my CPAP (directly off 12V DC). We boondocked several nights. We had enough battery to run the inverter in the morning for coffee and toast. We ran the generator at 6 PM to charge. We never went below 50% SOC.

We have 270 watts of solar, but when you are parked in the trees and/or there is little sun, it does little. The Classic with CZone is power hog. I'm sure others will chime in to provide more info.

[kb0zke]

Just got the electric bill for January. We used just under 25kW/day. That 560AH Li Time battery for $1599 sure sounds interesting - except for the 133 pounds. Fifty years ago that might not have been a problem (except that that's what I weighed). Now I weigh more and can lift less. I'm thinking that maybe a pair of the 280AH Redodo batteries for $490 each and 60 pounds each might be a better idea. Of course, getting a young guy to do the lifting might be an even better idea.


Since we have a Flying Cloud we don't have all the electronic stuff. We also don't boondock a lot, especially in the heat of summer or cold of winter. The plan is to be able to go to Q or the Gulf Coast for a few days.

[BGClassic]

You will figure out what works for you. Requirements, budget, etc.

[PaulBristol]

So, do I really need that capacity? We are full-timers, not weekend campers, so we do need to be able to live normally. For us, that means using the microwave, coffee maker, and toaster oven regularly. What would your experts suggest?

Of course that is a question no one can answer except you. As much as you want an easy way out, it is all on you.

Add lights, charge cell phones, computer & wifi, etc.

Assuming you do not run electric refrigerator, water heater, space heater, etc.

No solar charging.

Shut off the inverter when not in use. Shut things OFF when not in use.

200 amp hours is good for a couple of days with reserve. Not exact of course.

How long do you want to run?

Test camp in your driveway or in a camp site with electric. Plug in when you run out of battery.

Track it while you camp. Start your generator when you run out.

Then you will know.

[uncle_bob]

Originally Posted by kb0zke

Just got the electric bill for January. We used just under 25kW/day. .....

Hi

So, *assuming* that's 25KWH per day (the hour part matters ) ....

25000 / 12 = 2,083 AH. If you want to be able to run for 5 days, that would be just over 10,000 AH or about a hundred 100AH batteries.

Best guess: there's something significantly off in that 25KW number. Likely due to electric heat. (It's also possible I messed up the calculations .... that *does* happen ).

It's likely on a newer trailer that you will have a "background" load of 4 to 6A. That over a 24 hour period gets you to the 96 to 144 AH range. For simplicity call it 100 to 150 AH a day.

If you want to run for 5 days, that gets you into the 500 to 750 AH range.

Now toss in the "using stuff regularly" side of this. Most typical "things" in the kitchen pull about 1500W. If cumulatively they run for a bit under hour a day, that would be another 100AH. You just doubled that "minimum battery".

Play with a CPAP or the furnace overnight and you add into the total.

Do you need 5 days of run time? I'd say you need more than two.

Can you count on solar? Better put, how much can you count on solar? That is highly dependent on where you are and what the season is. 4 "full power" hours a day may be too much to count on. With 400W "on the roof, 4 hours would be 1600W or 133 AH. We rarely get over half that at the places we hang out. I target 1/3 of that number.

So how much battery? How much can you fit in without loosing space you need for something else?

Bob

[Life is a Highway]

The race to be the best just keeps growing

Pretty soon the entire trailer skin will be solar panels interior one big battery that has sleeping quarters of course one must now to be YouTube Cool add on the 2600 frame mount propane gen hysteria which doubles as a foot massager while running.

I believe 300-400 amps is a sweet spot. Solar is up to you. I use a 60 amp dc-dc system to charge while towing and carry a Honda 2200 for back up needs.

[1StreamDream]

Couple things, first is that if you dont have a surge protector in between your trailer and your pedestal 120VAC plug-in, I would recommend you get one with advanced monitoring capabilities and bluetooth data support (can view usage data in real time from your smartphone), and this will give you very good details about your consumption. I picked one up at an international rally a few years ago, it is made by Hughes, https://hughesautoformers.com/product/pwd30/ and there might be other competitors available. My trailer is 30A, so that is the surge unit I have, and I converted my fridge to electric (12VDC/120VAC) last summer, so my DC draw has gone up considerably when we boon dock, and for us I feel like 300Ah of lithium battery is a minimum (and is what we currently have). Note we also have 480W of solar panel on the roof, and 220w of portable panel, to help ensure we can boon dock for extended periods without shore power. This also lets us run the microwave and/or toaster freely but certainly not indefinitely. If you have an LP fridge for boon docking, I feel like 200Ah of lithium is probably adequate (as long as you have some solar or other way to replenish power if necessary).

[uncle_bob]

Hi

It's not just space that this stuff takes up. It also adds weight. Solar panels and mounts are not trivial items. We all have carried batteries around. The stuff all needs to be well mounted, that structure weighs something. Now start looking at all that copper you are going to use to run from here to there and back. We haven't even gotten to the inverter and charger or other electronics (they *do* weight something ....).

You have a *very* finite payload on these trailers. The number on the sticker is with no water in the tanks. Fill up the fresh water tank and you just used up a pretty good chunk of that payload. Fill up the fresh water with the black / gray still full and you used up a *lot* of that payload.

It's not just one number that matters. As you put weight here and there in the trailer you impact hitch weight and stability. Either hitch weight goes up or stability suffers. Indeed you *can* put things on the roof and have both suffer. I have data on this .

Now toss in spending a lot of time in the trailer. There is a *very* finite amount of storage. You do need to have tools and spare parts along. They have to go somewhere and most certainly have weight. If you travel over a range of areas, you will have gear for a number of climates.

You just *might* want to have food along. Some of us *have* been known to carry an inventory of beer . Unless you do laundry every other day, it's going to pile up somewhere. Same thing with the trash if you are boondocking out in the middle of nowhere.

I'd also advise not using up 100% of the rated capacity. You never know when you might find a great deal on that giant rock you always dreamed of owning . (Ok, they were not all that big, but there were a lot of them ),

Fun !!!!

Bob

[JeffKim]

The answer is 4-6. We have 4x100Ah batteries under one twin bed. With our 700W of solar (I know you're thinking of 1000W) this seems to work out pretty well for keeping our frig going and other things like computers and Starlink. We don't have a generator.

The newer higher density 300Ah or greater batteries are nice, but heavy as you point out and you need to find the space. I like having 100Ah, 25lb batteries that fit in the hatches under the bed. The 100Ah are also getting smaller and lighter. Renogy has some small ones where three fit in the battery box when it used to be two. So maybe six of these would work under the bed.

We're not full timers so likely my thought process is different. I've bought into the idea that in a few years or so I'll be replacing the batteries with something smaller, more energy dense, and cheaper. I don't think it's worth spending a lot of money on top of the line which will be obsolete long before the end of their life.

[Jum]

My answer is: as much as you can fit and afford.

I put 2x 280ah Litime plus inverter/shunt/fuse under one twin in our Argosy. They fill the space well with the batteries over the axles inboard of the wheelwell and the inverter just aft of there. That is now our electrical space and I couldn't have done any more unless I added more under the other twin which isn't really feasible due to cabling.

[Saullman]

So I built my 280 ah lifePo4's and they're in my 2023 classic 33. Three of them totaling 810ah and im really happy with how much we have , but there are times when it's cloudy for days and wish we had more battery and more solar. BTW there is 1K of solar on the roof.

[BGClassic]

Originally Posted by Saullman

So I built my 280 ah lifePo4's and they're in my 2023 classic 33. Three of them totaling 810ah and im really happy with how much we have , but there are times when it's cloudy for days and wish we had more battery and more solar. BTW there is 1K of solar on the roof.

That's a clean install in the front locker! Is that the original inverter in there? I am interested in seeing how you brought the solar cable runs into the trailer; do they come down forward of the shower in that void?

[Saullman]

Thank you. Yes that is the original WFCO 1K inverter, it's unplugged and has no use whatsoever. you are absolutely correct sir.!!

[BGClassic]

What brand/model solar panels did you install? I like the setup the more I look.

[sfranklin]

With a 21' 30 FC, you have an absorption fridge. I had this same unit and I could camp well over a week without power issues. It had 180w of solar and didn't have lithium.

If you had a 22 or newer, that has the 12v compressor fridge, yea, you'll need a min of 200ah of lithium and a min of 300w of solar. I am about to find out in 4-5 months if that is even enough as mine came from the factory with 200ah of lithium and 300w of solar.

[waninae39]

it best to get as much Lion as you fit and afford. leave room for more at a future date

next get as much solar on the roof as you can fit

[kb0zke]

Thanks for all of the thoughts. January was unusually cold here, so the furnace ran more than normal (but the a/c didn't run very much). The 25KWh number is from the electric meter. As I think about it, that does include what was used in the casita, so it would be less just for the trailer.


We have an appointment at Livingston for the Smart Weigh, so after that I'll know exactly how much additional weight I can add, and where I might be able to put it. I currently have a pair of AGM batteries in the battery box on the tongue. I'm not looking forward to lifting them out, but I'm guessing that the two of them weigh close to what I'll be putting in in LiFePO4 batteries, but the new batteries will go inside (I hope). If that happens, the battery box will probably just hold the Beech Lane levelers.


A neighbor mentioned that battery prices may be going up. Another one thinks they are coming down. I'll pay what they are when I buy them.


I currently have a pair of 100W (nominal) solar panels on the roof, probably Zamp brand. I'm hoping that when we visit the Airstream park near Hillsboro I can pick someone's brain a bit about what might and might not actually work. I also want to talk to a couple of installers to see what they suggest.


As i said, we don't do a huge amount of boondocking, but as we learn more we may do more. It offers an alternative to FHU sites and can make life a bit easier should some idiot try to run over a power pole. (Yes, we hosted at a park where that happened three times in two months! I thought the power company ought to get smart and move the pole.)

[Saullman]

These are the 100 Watt ZAMP Panels

[uncle_bob]

Originally Posted by kb0zke

.......

As i said, we don't do a huge amount of boondocking, but as we learn more we may do more. It offers an alternative to FHU sites and can make life a bit easier .......)

Hi

Ok, use cases:

1) You're going someplace far away. You drive (say) 6 hours on route each day. That's probably 7 to 8 hours on the road. With traffic At the end of the day you pull into a Harvest Host (or something similar). Typically no hookups but a place to spend the night.

If you have a DC/DC converter (that works ): The TV is charging things for > 6 hours a day. If it's a 15A setup, that gets you about 90AH. You are about 30AH short of your "minimum needed" number of 120 to 130AH for the day. You don't need a lot of solar to make up for that gap. Your two 200W panels likely do the trick.

2) Still on route somewhere. The tanks are full / empty, the fridge is looking bare, it's time to do laundry. You pull into a full hookup place to take care of all those issues. Is that one night or two? Let's say two. If you have a 60A charger and it runs for 24 hours that's well over 1,000 AH. Tanks *might* last you for 7 days ... also could be about 5 days. At 7 days your 1,000 AH battery bank could do 140AH a day. That plus the DC/DC would go *way* more than 7 days. (no solar needed).

3) You "get there" and it's a boondocks site 3 hours away from everything. The same "call it 7 days" stuff applies in this case (tanks do fill up ...). How much more than the minimum power number do you use? Manage things wisely and that 1,000 AH battery bank just might get you through. Decide to run a pair of A/C's off battery ... not going to make it 7 days . If you have to "tow" for 6 hours to dump tanks, that DC/DC gets back in the picture.

4) You are out there and you *do* go into the > 150AH a day range. At 5 days to "go do the tanks" you have 200AH in the battery bank. If you are up above that, I'd suggest better management would be the thing to look into . At 7 days, you are down by 50 x 7 =350 AH with 200AH usage. That (surprise !!!) comes out to 50 AH a day (or 600WH). On a "5 hours full power" basis, your two 100W panels likely do the trick..... maybe ....

What's the point here?

You can do pretty well just with a whole lot of battery. You don't *have* to go to absolute max both on solar and battery for what most would consider typical use cases. If you decide to run A/C, all bets are off ... bring along a generator .

Fun !!!

Bob