Newbie battery and solar power questions

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  • TerryHutchinsonTerryHutchinson Member Posts: 45
    If the published numbers are anywhere near accurate, either model consumes far less power than the OP originally suggested.
  • MarcelineMarceline Member Posts: 1,497
    CharlieRN said:

    The precise fan model is not listed on the invoice for my Boondock, but I believe it’s the Fantastic 1250. I could not find any information on its power consumption on Dometic’s website or in the pdf of the owner’s manual there. Based on what Jenn G posted, however, the fan draws 1.2 to 2.75 Ah depending on mode and speed. That’s a fair amount of power for a device that will likely need to be used quite a bit. I understand that installing upgrade kit will provide more speed controls and lower power usage but at a considerable cost.


    This mod is an inexpensive alternative to installing a whole new fan: https://tab-rv.vanillacommunity.com/discussion/comment/140981/#Comment_140981

    I also installed this vent cover: https://amzn.to/3mr1N0A

    So for about $50-60 I have a fan that I can run a very low speeds (little energy) and a vent that I can leave open on the road and in the rain.

    San Francisco Bay Area
    2013 CS-S us@gi
    Battered but trusty 3.5l V6 Hyundai Santa Fe
    2015 Toyota Tacoma PreRunner Double Cab
  • TerryHutchinsonTerryHutchinson Member Posts: 45
    Here's a link to the variable speed PMW device that is well reviewed and works:https://www.amazon.com/gp/product/B00F839VNQ/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

    For a few bucks less Amazon also lists an very similar device that is sourced directly out of China and will takes weeks to deliver.  It is very poorly reviewed and looking at it briefly it is clearly not the same unit (note the missing fuse).

    If you peruse the Amazon link posted above, one of the people who upgraded the 1250 Fantastic Fan posted photos of how it should be wired to work.

  • CharlieRNCharlieRN Member Posts: 438
    If the published numbers are anywhere near accurate, either model consumes far less power than the OP originally suggested
    The 3.6 Ah for the refrigerator came from what I saw posted in one of the threads I looked at. The table I then put together gave totals for 8 and 10 hours of run time using that current value. I think that means about 29 Ah for the former (3.6 * 8) and 36 Ah for the latter (10 * 3.6). Watt-hours would be 348 (29 * 12) and 432 (36 * 12).

    The info on indelwebastomarine.com gives power consumption over 24 hours, which I take to mean mean the total consumed over the period. For the Cruise Elegance 49, the website states that power usage is 340 watts/24 hours and for the CE65 360. I think that this equates to ~28Ah (340/12) and 30 (360/12)Ah respectively.

    Of course, there is always the possibility that, just like G.O.B Bluth in Arrested Development, I've made a huge mistake . . .
    2021 T@B 320 S Boondock / 2022 Telluride - Phillies/Eagles/Flyers Country
  • MarkAlMarkAl Member Posts: 455
    So about 30 A*H per day for the refrig on the 320 that makes a tight 3 days with two 6Vs or 1 lithium. But solar charging 4 hrs of excellent sun could be doable to replace the day's usage.... Now about the other loads.... Keep lights/fan/pump usage low. But you're hurting on a smaller Grp 24 for more than a day is my W.A.G.. This matches my experience without solar help but I've only been mid 70s or less during the day at a setting of 2 or 3. If the refrig needs to work harder because of higher ambient temps maybe 2 days.
    Snohomish WA, 2015 Diesel Grand Cherokee
    Sm@ll World: 2021 320S Boondock, 6V Pb-acid
    Shunt, Roof & Remote solar & 30A DC-DC Chargers
    managed by VE Smart Network
  • TerryHutchinsonTerryHutchinson Member Posts: 45
    You lost me there somewhere.  CE65 per manufacturer's projected usage is 360 watts per 24 hours - or an average of 15 watts per hour.  Dividing watts by 12 volts gives 1.25 amps/hr.   To rephrase,  360 total watts per 24 hr = 30 amps in 24 hours running at 12 volts - - - so again 1.25amp/hr.  Am I figuring wrong? This is far from my specialty.
  • Sharon_is_SAMSharon_is_SAM Administrator Posts: 9,460
    edited September 2020
    360 watt hours / 12 v = 30 amp hours used per day.

    (Edited to reflect unit of measure.)
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
  • DougHDougH Member Posts: 1,110
    edited September 2020
    @TerryHutchinson A reminder...  when you see a manufacturer say 200 or 300W per 24hours or day... they mean Watt-hours (Wh) per day.

    As I ranted in a previous post:

    "Watts are Joules per second and is a rate of power consumption.  Why would you divide that by a time unit again, unless measuring how quickly, or with what acceleration, a device can ramp up to full power?  The amount of energy used is more commonly measured in Watt hours or kW hours.  When analyzing solar system sizing you often look at how many Wh per day all your loads use, versus how much sun you can collect in a day."

    Similarly you cannot say you used 30A per day.  But you can say you used 30Ah on a average day.  And if everyone knows you're talking about a 12V or 48V based system they know how many Wh or kWh that is.  Look at a utility bill.  You get charged for kWh of energy used in a given month.  NOT kW/month.  Look at any Renogy or Victron battery monitor and your state of charge.  You start at 100% or 240Ah.  Then slowly over the course of the day you use up 50Ah of those 240Ah.

    This is why the calculations may not make sense when starting with an erroneous manufacturer specification with mislabeled units.

    So in this case remembering P=VI, 360Wh on a average day divided by 12V is 30Ah per day.

    My tiny fridge has a 22W mode and a 40W mode.  That's Watts which is a rate.  If it was constant in the lower rate mode, and if there's 24 hours in a day I'd use up 528Wh every day.  Divide by 12V and that's 44Ah every day. But it's not constant.  It cycles on and off.  So it ends up using around 9Ah a day.  Multiply by 12V again and that's 108Wh/24h or 108Wh per day.  But it's a tiny ICECO GO20.
    2021 Jeep Gladiator, 2021 tiny toy hauler, Austin TX
    Former steward of a 2017 T@B S Max

  • ChanWChanW Member Posts: 3,158
    @DougH, thanks for your clear explanation. (It drove me a little batty when folks would refer to Amps as though they were Amp-hours, but then it's happened so often that I've started automatically translating it)

    It certainly helps to understand the full picture when you're getting down to the details of power usage.
    Chan  -  near Buffalo NY
    2014 S Maxx
    2011 Tacoma 4cyl ... edit: 2022 Tacoma 6cyl - oh yeah! 

     A_Little_T@b'll_Do_Ya
  • DougHDougH Member Posts: 1,110
    @ChanW I blame my high school physics teacher.  He would get super frustrated if we got the units wrong in our work.  He'd say he didn't care if we were off 10 or 20 percent numerically (after all there were no calculators back then, and they'd just recently invented the slide rule and abacus), but we'd get a zero on that question if the units were wrong.
    2021 Jeep Gladiator, 2021 tiny toy hauler, Austin TX
    Former steward of a 2017 T@B S Max

  • BrianZBrianZ Member Posts: 1,763
    edited September 2020
    Amen, @DougH
    People's misuse of units has been driving me nuts too, so thanks for your postings.  People often say something like a "fridge draws 4Ah" or "uses 75A per day", neither of which actually make any sense because the units are inappropriate & it leave you (or me) second guessing what the heck they are actually trying to say.
    "..recently invented the abacus.."  haha -good one!  You must be pretty old! 😉
    -Brian in Chester, Virginia
    TV: 2005 Toyota Sienna LE (3.3L V6)
    RV: 2018 T@B 320S, >100 mods 
  • CharlieRNCharlieRN Member Posts: 438
    edited September 2020

    Thanks again to all the T@B owners who populated this thread with so many helpful comments and suggestions. Special thanks to DougH and BrianZ for keeping me on the straight and narrow WRT to terminology. Here's an outline of my tentative plans, based largely on this thread's informative feedback:

    Battery - upgrade stock 12v to a pair of 6v, 200 - 225 Ah batteries. For this initial outfitting, the plan is to use less expensive flooded cell batteries as suggested by elbereth. I think the battery change will also require an upgrade to a 15 amp solar controller. A sure addition is a [wireless] battery monitor.

    Fan - take delivery with the standard Dometic 1250 and upgrade it with an aftermarket PWM controller as suggested by among others, Sharon_is_SAM and Terry H. Also add the Camco vent hood per recommendation by Marceline.

    Under consideration: Isotherm Smart Energy Control Kit. Cost is modest but install requires drilling into a brand-new $1,000+ refrigerator. Based on JennG's experience, the factory claim of a dramatic (up to 50%) reduction seems questionable. If it's such a good system, why isn't it standard in a small refrigerator with a list price over a grand?

    Possible later addition: Supplementary power - option 1 is a portable solar system such as the Renogy or Jakery; option 2 is a small propane generator and second storage tank.

    2021 T@B 320 S Boondock / 2022 Telluride - Phillies/Eagles/Flyers Country
  • ScottGScottG Administrator Posts: 5,396
    @CharlieRN, I think the size of your solar controller is driven by the maximum output of your panels, so you may not need to upgrade the controller unless and until you add more panel capacity. (Which is something you might need to do to charge those big batteries up quickly.)
    2015 T@B S
  • Sharon_is_SAMSharon_is_SAM Administrator Posts: 9,460
    @CharlieRN - when you say wireless battery monitor, do you mean one that you access via a phone?
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
  • pthomas745pthomas745 Moderator Posts: 3,605
    For those of us who were/are not engineers or had any electrical training, getting over the hump of how to consider amp hours and watts, etc. is a big big leap forward.  When I realized my battery was rated in amp hours, and the fan used x many of those amp hours and I could just do the math and it would "add up", it was like a lightning bolt hit me.  Same thing with how watts divided by 12v would give me the estimated amps and I could figure out the amp hour use that way of devices I wanted to use.
    So, it might drive a "trained" person crazy (and I understand) but sometimes a really elementary, dirt simple computation might open the floodgates for someone.

    2017 Outback
    Towed by 2014 Touareg TDi
  • CharlieRNCharlieRN Member Posts: 438
    edited September 2020
    @CharlieRN - when you say wireless battery monitor, do you mean one that you access via a phone?
    Yes, and had in mind something like the BT-enabled Victron Smart Shunt.
    A battery monitor is essential but I am not convinced that wireless is the way to go (and hence the brackets.) They're convenient but there's the added power draw for the transmitter to consider and they are much more expensive than their conventional bretheren.
    This is all new territory for me, and I'd welcome any input from experienced folks.

    2021 T@B 320 S Boondock / 2022 Telluride - Phillies/Eagles/Flyers Country
  • Sharon_is_SAMSharon_is_SAM Administrator Posts: 9,460
    edited September 2020
    Since you said your boondocking was probably only going to be 3 days, I would try a simple plug in 12v meter first.  Depending on where you are camping, a supplemental solar panel may be more worthwhile (coupled with some electric conservation) than the Smart Shunt.  The extra amp hrs draw from the Victron is minor in the bigger scheme of things.  

    (Did I get it right... amp hrs?  You know I wanted to say amps!)
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
  • CharlieRNCharlieRN Member Posts: 438
    ScottG said:
    @CharlieRN, I think the size of your solar controller is driven by the maximum output of your panels, so you may not need to upgrade the controller unless and until you add more panel capacity. (Which is something you might need to do to charge those big batteries up quickly.)
    It's a good thing that my Outback won't be here for a few months since it gives me time to fill in the many gaps in my knowledge base relative to trailer camping. I've been trying to get up to speed WRT to solar, but am a long way from being there, as my comment/question about the controller indicates!
    2021 T@B 320 S Boondock / 2022 Telluride - Phillies/Eagles/Flyers Country
  • ScottGScottG Administrator Posts: 5,396
    edited September 2020
    ...
    (Did I get it right... amp hrs?  You know I wanted to say amps!)
    ...
    I think in this case either would be technically correct. However--since amp-hours are really more about battery capacity--I would also have been inclined to just say "amps" when referring to how much current a device draws.

    Discuss...  ;-)
    2015 T@B S
  • Denny16Denny16 Member Posts: 5,420
    edited September 2020
    There is however, a difference between a device drawing 4 amps, and one drawing 4 amps per hour.  A 4 amp current draw is a lot more than something using 4 amp hrs of stored energy.

     In the measurement of electricity, amps are a unit of electrical current; amp-hours are units of current storage capacity. ... An Amp-Hour is a more abstract idea, multiplying an amount of current by a period of time: one AH is defined as an amp of current flowing for one hour.”
    Cheers
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
  • 2WoodsyOnes2WoodsyOnes Member Posts: 6
    If the 320S is stored indoors and isn't being used for long periods, do you need to keep it plugged into a power source?
  • pthomas745pthomas745 Moderator Posts: 3,605
    A fully charged battery will hold a charge for months.  Charge the battery, turn off the battery switch, and just have a look at the state of charge every once in a while.  The a fully charged "healthy" battery will be fine.  If your battery is 6 years old, etc, you may want to check it more often!

    But: many owners do just keep the trailer plugged in. Just remember the battery won't charge from shore power unless the battery switch is "on".

    2017 Outback
    Towed by 2014 Touareg TDi
  • pthomas745pthomas745 Moderator Posts: 3,605
    @2WoodsyOnes I should have asked, but I just noticed your other posts about battery charging, and noted you have dual lithium batteries.
    The same thing applies to just turning off the battery switch.   A lithium will hold a charge just fine, and apparently "likes" being stored at about 80 percent capacity.

    There is a big bucket o' worms when talking about "Lithium Batteries and The WFCO Converter".  So, have a good look at the model of your converter, so we can figure out if it has the "lithium switch" which will "properly" charge a lithium.  The converter in my 2017 is the "non-lithium" type, and will only charge my lithiums to 85 percent or so on shore power.  I get around that with a Noco smart charger that can charge lithiums if I really need to charge it up...which I did once.  I usually just have my portable solar do it for me.
    2017 Outback
    Towed by 2014 Touareg TDi
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