Newbie battery and solar power questions

TerryHutchinson

If the published numbers are anywhere near accurate, either model consumes far less power than the OP originally suggested.

Gbertrand

Good morning all.....and sorry for the long post

I realize that this thread is mostly directed at the 320, that said I thought I would share my experience with our new 2021 400 BDL.........we took possession of our new caravan in mid July, since then we have spent 32 nights and only one night was in a campground with hookups, the other 31 have been totally off grid, with the longest single duration beeing 14 days

Both my wife and I are very accustom to "boondock" camping as we spent many years with our tent (and supplies) on the back of our bikes all over Western Canada, South Western USA, and all of the Baja........however, now with the new T@B we have become, well, let's say SPOILD!!! and never really try and conserve energy much, and so far have had no issues. So just a couple points for those asking "how long can I boondock for"

As many have already said.....prechill the fridge, I normally will plug in at home for min 24 hrs. at around ~4 setting, load the little freezer with 2 ice cube trays (that I modified to fit), and a small baggy of ice, then load with supplies and turn to ~2.5, we are so impressed with the little 12v fridge, both energy consumption, and what you can stuff in that little guy. We also carry a small 3-way fridge in the back seat of our pick-up plugged into the 12v receptacle while on the road, once the Walker tent is set up it goes in the tent with an extended hose outside to a 20 lb propane bottle (as a note....we have used the same bottle all Summer, so 31 nights boondocking) and I just weighed it, 26.5 lb, so ~6lbs left.......very efferent, as it has been extremely hot this summer

As for battery power, as we are normally in non regulated camp sites, so we always try and park with the back of the T@B facing SW, for greatest solar absortion, and as stated above we have become spoiled so we are not real great at conserving .......we find the 12v fridge is very efficient, and we try and keep stuff that we use regularly in the 3-way portable in the Walker tent to lessen the door open/close on the 12v but that is as far as we go for conserving energy, I have mounted a Sirius radio in the cabin and pick it up via BT on the Jenson, this we run ~6 to 8 hr a day (and mostly at night), that said should we have a cloudy day and battery bank is not full we also carry a small BT speaker and play the downloaded playlist of my phone, and beeing were we normal camp there is no cell service so not much need for recharging. Our vent is always open but very seldom use the fan, as we are normally outside, and do most our cooking in the Walker tent, only time the fan is used is if one of us needs a nap in the afternoon after a hard day of fishing😀 We also carry a 10" (rechargeable) battery operated fan, that can be used inside/outside and is wonderful. If we have a good sunny day we even use the inverter to make toast for breakfast, and my wife having long thick hair will use the hair dryer couple times a week. The Alde heater does not use much power at all (again been hot this summer, but does cool down at night hear in the mountains) All this said we just monitor the victron to insure we don't go below 12v (always check mid afternoon to insure enough energy for over night) and have not had any issues power wise, and as mentioned above our longest trip was 14 days........we are going to purchase a "suitecase" solar panel for those overcast days,  or times when the best camp site is in the trees, as we all know these sunny days will not last

As for the 3 holding tanks, we always try and camp by a creek or river, so re-filling the fresh water tank with the new Nautilus system is as simple as it gets, plus we carry 2 (5gal) drinking water jugs, the 2 drinking water jugs last us ~10 days........the grey tank, we only use biodegradable soaps, and never put food or grease down the traps, with the 2 of us, and only short showers every other day, the grey tank lasts ~5 days, in our area we are permitted to dump grey water in the bush, I try to keep it aways from our camp site (lessen the bug attraction) and never close to a water body, but check with your local area as I am sure many places are different........as for the dreaded black tank, again we get ~5 days, this we carry a 5gal tote to empty, many places we camp at have a pit toilets close by, and here we are permitted to dump waste in them, that said even if a pit toilet is not close by a nice scenic drive to the nearest town every 4 or 5 days is not that big a deal as the wine supply is normally getting low by this time😀😀😀

Again sorry for the long post, just thought I would share a.........."just go and do it" prospective

Have a wonderful day

Marceline

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.

TerryHutchinson

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.

CharlieRN

TerryHutchinson said:

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 . . .

MarkAl

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.

TerryHutchinson

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_SAM

360 watt hours / 12 v = 30 amp hours used per day.

(Edited to reflect unit of measure.)

DougH

@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.

ChanW

@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.

DougH

@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.

BrianZ

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! 😉

CharlieRN

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.

ScottG

@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.)

Sharon_is_SAM

@CharlieRN - when you say wireless battery monitor, do you mean one that you access via a phone?

pthomas745

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.

CharlieRN

Sharon_is_SAM said:

@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.

Sharon_is_SAM

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!)

CharlieRN

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!

ScottG

Sharon_is_SAM said:

...

(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...  ;-)

Denny16

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

2WoodsyOnes

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?

pthomas745

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".

pthomas745

@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.