Boondocking Available AmpHr & Usage Help Appreciated to Confirm my spreadsheet

Awca12a

The spreadsheet image below will get refined over the coming season to narrow down the actual hours that each appliance or device is using and I purposely haven't added the solar input yet just to confirm that the basic approach and calculations are correct.   I'm assuming that the 224 AmpHr rating of the batteries supplied by nuCAMP isn't the number to be using because that's over a slow 20-hr discharge rate.  Fine for some things like the Alde circulator but not for the heater, furnace, water pump and so forth.  Those happen over a much shorter period so I'm thinking I need to use the 10 or 5 hour ratings which are 194 and 179 respectively.   For the moment, assuming the hour run-times are correct on the winter usage, without any solar input these max usage assumptions on the 10 and 5 hour ratings at 50% discharge have to be cut back.   Or, I'm doing the math wrong.

Would appreciate any input either confirming this is correct or pointing out where I've errored.
THanks

Sharon_is_SAM

I think the 5 and 10 hour ratings are designed for consuming large amounts of amperage over a short amount of time, like with a piece of construction equipment.  The TaB useage is more intermittent and relatively brief, so I would stick to the 20 hour amperage rate.  When you plug in numbers for a battery monitor, most use the 20 hr amp capacity.  That is the accepted baseline for comparing batteries for RV and solar use.

Awca12a

@Sharon_is_SAM Thank You for the feedback.
I'm trying to create an easy to read graphic/spreadsheet that conveys what you'd need to know when making a week long boon docking plan assuming some solar but no generator. Can I run the fan all day in summer, or let the heat stay at 65 in winter, run the fridge year round, turn-on the tank heaters in the fall, and so forth.  For a day or two or hooked-up to TV or shore power, no problem.   This is for BLM or other multi-day locations.  

The 20-hr rating according Harris Battery who's equipment is used in the 400, is for equipment that is used all day long with no real variations.  A light bulb left on comes to mind.  For a refrigerator it would also work assuming the unit was not opened all the time and the setting was on 2-3.  For heat, they tell me that I need to use the 10-hr rating because I'm drawing a significant power during an 8-12 hour period, not evenly all day long.   For a light bulb during the same period it wouldn't matter because the draw is so low.  Kind of makes sense but just asking for clarification from the experts here.

Not being an engineer, I'm not sure whom to believe but my experience seems to coincide with the idea that the batteries have less tolerance for a heavy load over a short period of time than a lighter load of same amps over a longer period of time.  Guess I'm trying to find out how far I can push the equipment by planning ahead a bit as opposed to waking-up to 11.9v on a different trailer as I've done more times than I want to think about.

klenger

@Awca12a: Do you have a battery monitor such as the Bogart Trimetric TM-2030-A Battery Monitor.  If not, having one of these is really the only way to truly monitor battery performance.  Using battery voltage to determine battery state of charge is similar to trying to determine how much gas you have in your car by how fast you can drive it.  It goes fast until it doesn't. 

https://www.solar-electric.com/bogart-engineering-tm-2030-a-battery-monitor.html

Amazon sells it also.  You will need the monitor panel, a current shunt, and associated wiring.  Not a difficult installation if you are handy with tools and have a basic understanding of electricity. 

pthomas745

Have you seen JkJenns blog?  She has the same type of spreadsheet, so if you haven't, you might want to compare notes.   Sheets like this are just great tools.

https://jenngrover.com/2015/11/guilty-as-charged-rv-battery-use-management/

As far as battery ratings go, I would keep your thinking to the 20hour rate just for basic user simplicity.  Once you start adding different battery ratings and Peukert effects and the outside air temperature, etc. most of your readers are just going to check out.  The notes and warnings about the different levels of draw from higher wattage appliances might be moved to a separate section or description.  Notes about how fast you can run a battery down with a 800 watt coffee pot (and why) would be an important thing to know.

When I discovered Jenn's spreadsheet, it was the most helpful thing I found to figure out how long my battery could last, because like you, I ran several batteries to their doom not truly understanding what was going on.

This is great work, no matter what.

BrianZ

I'm a little late reading your discussions, @Awca12a, but kudos on the spreadsheet planning, heaters, & adding a battery monitor.  I'm curious if you've been able to put your batteries, solar & winter power usage plan to the test yet. 

I would agree with your "idea that the batteries have less tolerance for a heavy load over a short period of time than a lighter load of same amps over a longer period of time", as that seems to be the gist of what I've been studying about Peukert's law (apologies if I've said a bad word).  Your batteries' 20-hr rating of 224AH implies a usage of about 11A, so you should be able to draw up to your daily 112AH limit as long as you don't exceed 11A max for an extended time.  So, if you can juggle the timing of usage of your big ticket items like frig & 3 heaters, you should be fine for staying under 50% battery usage.

Approaching 100AH per day sounds like a huge amount of power, but then I've never tried to run a bunch of electric heaters.  We have only used about 20AH per day including brief dips into the lower 30's/upper 20's.

I'm no expert, but what I'd be more concerned about in the winter plan is not having more reserve battery power &/or not enough solar.  If you need to recharge 100AH of battery power at 12V, that's 1200Whrs needed.  If you have, say, 200W of solar panels available, then you'd need 6hrs of full sun to recharge your battery, and that may not be possible in the winter or less than perfect weather or location.  Lower usage or more battery power & solar would be a solution, or you might end up needing a generator or driving & finding hookups. 

At least now that you have a monitor, you can get a better handle on what your actual needs will be.  Other than winter, with all those heaters going, I would think you should be fine otherwise.  And maybe you'll still be fine, but once you know your real needs, you might decide to look at some kind of backup plan for winter.
Good luck!

Awca12a

Thanks All.  The BMV-712 is the battery monitor we installed as it works nicely with the solar controller app and is what AMSolar recommended.  We've found the usage to be fairly accurate and decided that the 3 heaters would get used most likely with #1 (Valves) being used all the time, #2 (Grey) being used when it's really cold and #3 (Fresh) being used at the cusp of freezing but at very low temps, either only while on shore power or only while travelling from place to place.   Summer is upon us and will be interesting to see how the spreadsheet changes.  One thing we know is that the fan draws an unacceptable amount of power and will be upgrading it for the Dometic that draws about half.

NorthIsUp

@Awca12a - I also have a BMV-712 in my 400. Do the 400 solar panels from mid-2018 (2019 BL model) come from AMSolar that I would be able to monitor with their app. Are you using one of their solar products and not what came with the 400?
For programming the 712, I just put in the amp capacity for the battery (224) and that was it for me. Should I be doing more? I can maybe help you with your statistics once the season starts. Mine has been in storage since October.  

Awca12a

@NorthIsUp
Mine was built with the new panels in November and I've attached that brochure here along with some file information I gathered on it.  My purchase from AM Solar was due to a purchase of traditional panels for a different trailer I have so I got an additional BMV for the nuCAMP giving me the same monitor for both.   Would welcome any real life input on the statistics.

Sprockethead

I used about 20-25 Amps/day in my R-Pod, with 2 golf car batteries(225 AH).

My new T@B 320 S should be similar... I boondock 90% of the time. In 2 years, I've only had to resort to my backup plan  once (see #3). We can last 7 days pretty easy. 

Conserve power:
1) Run my wife's Hair Dryer off the truck battery, which is a "renewable" source, for short term power.
2) Use Rooftop and Portable solar (both 200 watts total). I use One Hour of solar in my calculations.
3) My Backup Plan is to hook up and drain (some) energy from my truck battery for the camper.
4) Avoid high current drain items!, Forget about Air Conditioning, unless you have a Generator.

Main power uses:
1) Roof & Desk Fans, I actually use them alot 12 amps/day.
2) Fridge on Propane 6 amps/day.
...As you can see, Fans are almost 1/2 my Amps usage.