Newbie battery and solar power questions

CharlieRN

Greetings all from a soon-to-be 320 OB owner. My order is in, but demand is apparently very high and delivery won't be for quite some time. The wait is a bit of drag, but it does give me the opportunity to learn about the TaB.

I'd particularly like to find out more about what I need with respect to the 12v system and boondocking. I did a search through the forum and found a lot of helpful information, but still have a few questions. I’ll apologize in advance if my questions are ones that have already been discussed to death on the forum and I just didn't find them.

My best guess that our dry camping will not be for terribly extended periods; probably no more than three consecutive days. There is quite a bit posted on the forum about the current draw for most of devices in the Outback, and I also found a number of discussions on how long the various devices would be drawing current each day (e. g., 8 hours for the Isotherm refrigerator). Based on this, I came up with what seems to be a conservative estimate range of 40 to 55Ahr per day. Not being and electrician and as a newbie in the RV world, I have no idea if this in fact reasonable. Any and all feedback on this point welcome.

If that estimate is OK, the upper end of the range (55 Ahr/da) would equate to 165 Ahr consumed in three days of dry camping. Assuming a worst case – too much shade or too cloudy for the solar panel to charge – the safe bet would seem to be to go with a dual 6v AGM system in the 220 Ahr range. From what I see online, AGMs have an 80% depth of discharge limit, so a 220 Ahr AGM system would yield 176 Ahr before hitting the battery discharge limit. Again as an RV newcomer, I’d welcome any feedback on this.

Other related questions for TaB owners. Can AGM batteries be used with the factory solar setup or is a different controller or modification to the system needed? I see that many owners have added more elaborate battery monitors to supplement the rather basic stock one. I don't think I saw anything other than Victron mentioned in the posts though - should I take this as a sign to not bother wasting time with others? Staying with the battery monitor, where do folks mount theirs? One video I saw had it on the same wall with the Alde and the AC panels. That wall is the back side of the bath though – how do you get access to run the wiring?

Sorry for the long post and for the many questions. Any and all comments, suggestions and criticisms are welcome.

Denny16

A 100amp hr AGM or Lithium battery with solar charging available should be all you need for three days of camping.  The fridge is your biggest load, and the solar should replace the current used overnight by the fridge, to keep the battery in the 80 percent charge state.  You are not going to have much room for two 100-110 amp hr batteries in a 320 TaB, and while they may fit in the new front tub, you are adding an extra 100 lbs of weight to the front of the trailer, unless you use lithium which is lighter in weight and size.  For a 200amp setup in the. 320 lithium would be the way to go.

The factory TaB 320 controller is a Victron MPPT 10-amp which works with AGM and Lithium batteries in the 100 amp range and a 100-watt solar setup, it sets battery type and size with the Control app on a smart phone.  

For 200  amps you should ask, to upgrade to the 15amp controller and 200 watts of solar panels to keep then
larger battery charged.
cheers

Deb55

I have a 2018 T@B 400, so my answers may not be as pertinent to your situation as someone with a 320, but I'll answer what little I can! We just had NuCamp install a 190 watt solar panel on the roof of our camper, and we have the dual 6 volt AGM batteries. Personally, I would aim for no lower than 50% discharge because from what I've read, that will keep your batteries healthier and give them a longer life. We also had the Victron battery monitor installed at the same time NuCamp did the solar and it's great for keeping track of your usage. We have it physically installed on the outside of our wardrobe closet next to the bed, but you don't have that same configuration. Some people don't actually install the physical monitor on any wall--they just use the app for their phones, which works really well. I mostly wanted the physical monitor in case my phone broke, or for trailer resale purposes down the road. We just got back from a 4 night stay in a state park with no hookups, and I wrote it up under a post called Trip report--2018 T@B 400 no hookups, if you want to see how our experiment went. Enjoy your camper! 

Denny16

Yes, adding the Victron Battery monitor is a grand idea.  On the 320, many owners mount the monitor in the front tub above the batteries, alongside the monitor shunt.  

Cheers

ckjs

... The factory TaB 320 controller is a Victron MPPT 10-amp which works,with AGM and Lithium batteries in the 100 amp range automatically, once set up with the Control app on a smart phone.  For 200  amps you should ask, to upgrade to the 15amp controller.

The best fit for the solar controller is to the panels, rather than the battery bank size. The 10 amp controller is good for up to 140 or so watts of panels, for charging at ~14 volts and 10 amps. The 15 amp Victron better fits a 200 watt solar setup. Mind you, the 10 amp one would still be safe; it just isn’t capable of providing more than 10 amps of charging current. 

pthomas745

55 amp hours per day seems.....a lot.  Be a little more specific on how you came up with that number. Fridge and movies all day?    

Victron is the new hotness on battery monitors, and suddenly the old fashioned, worked for 50 years multimeter has been tossed in the dustbin.  They still work.  They still can give you plenty of info (after you get used to it.)  Love my Victron, but it was learning how to use a multimeter that really showed me how useful it is.  If that makes any sense.

Anyway, show your work on how you came up with your amp hour use numbers.

PS: Bluetooth has made the physical "dial monitor" inside the trailer redundant.  You will wind up using your phone, it is much more useful.

jkjenn

I cannot get more than 2 days from 225ah of battery (dual 6v, AGM) and the 105w factory solar. I have an additional 100w solar panel on order, now, to hopefully give me a little more breathing room. 

4ncar

2@ 6v flooded golf cart batteries easily fit in the tongue box. Weight is only the net value of one battery, not 100 lbs as previously stated.  My 2 batteries equate to 235ah(1/2 usable).

MarkAl

I've been dinking a lot with solar this summer learning both how to camp with electricity and how to collect solar energy. Much has been learned in the dark forests of the PNW that I hope to use this winter. I seriously doubt even with the roof 105 watt and 2 series 100 watt pannels, two 6V batteries I'll do better than 4 days unless I can get 4-5 or so hours of sun on any of them every 2 days or so. Anything less and you're not recovering your energy store. So suck it up and have a 1500 - 2000 watt generator stashed someplace unless you turn off the refrigerator (I keep it set to 3). Jenn's comment about these refrigerators using more power when the ambient is hot concerns me as I haven't been in a hot situation this summer. Note that a bunch of people who've commented on this thread are way more knowledgeable than I on this subject. BTW my wife and I love the new T@B overall though I wish I would feel more comfortable taking it on some more gnarly forest service roads, has the ground clearance mostly but the bumping...

By the way just installed the fan mod for reducing current usage. Easy to replace the power sucking resistor with a 10Kohm variable resistor with power switch and the PWM module.

elbereth

We have a 235 Ah dual 6V GC2 (not AGM, just flooded lead acid) setup in our 320 with the old style tub and we still are under 200 lbs tongue weight.  So it is definitely do-able.  

We don’t have rooftop solar, only a 100W portable suitcase panel.  This seems to be our summer of shady campsites and cloudy days so my best charging day this summer according to the Victron app has been 80 Wh (6.7 Ah) - A pittance!

Our usage is typically around 35-40 Ah per day.  We are not profligate with our electricity usage (we’ve actually removed the TVs) but we also don’t skimp too much - we run the 2 way fridge, typically on level 1, use lights and water pump freely, keep the fan running much of the time when it’s warm out, charge our cell phones overnight, etc.

3 nights of overcast boondocking has been no problem with this setup, but it does get me down around 65%.  I am glad for my 235 Ah battery bank, wouldn’t want less, but with a similar camping style to yours I haven’t wanted more.

If you pick them up from Costco or Batteries Plus, you’re looking around $100-$110 each for the 2 batteries, so it’s not a huge investment to upgrade.  Don’t go all out on your first battery bank - killing it in the first year or two as you learn seems to be a rite of passage!

I would suggest the new Victron SmartShunt, which lets you have the sophisticated battery monitoring on your phone without having to run any wires to a display.  It is not much more expensive than the BMV-712.

CharlieRN

Thanks to all for the very informative replies.

Rising to the challenge from pthomas745 to "show your work on how you came up with your amp hour use numbers", my spreadsheet is excerpted below. As mentioned in my original post, I'm new to the RV world, so don't really know if my estimates of usage are realistic. I'll also point out that both the low and high of the range are hopefully conservative and that I rounded up to get to 40 - 55 Ahr.

I'd also like to specifically thank jkjenn - many of the current draw values in the table were taken from her informative postings. It looks like she spent an enormous amount of time collecting data and I'm grateful that she so freely shared it. Her response in this thread regarding her recent battery/charging experience is also a bit concerning. It begs the question about as to what the culprit(s) may be.

I would think that two likely suspects are the refrigerator and the always-on devices that I grouped together in my table as parasitic draws. Perhaps the refrigerator draws more current than the 3.6 Ahr value I ballparked in the table, or perhaps it runs more often than 8 or so hrs per day? I've also read that the some BT enabled devices tend to use more power than their published values would indicate. So maybe something like the Victron draws more than a trivial amount of current as it  measures and transmits power usage information?

			Low Estimate		High Estimate
		Draw (Ahr)	Usage (hrs)	Usage (Ahr)	Usage (hrs)	Usage (Ahr)
Alde	Comb Heat/HW	0.6	2	1.2	8	4.8
Water pump		2.2	0.5	1.1	0.5	1.1
Refrigerator		3.6	8	28.8	10	36
Radio/stereo		0.41	2	0.82	3	1.23
TV		1.57	0.5	0.785	0.5	0.785
Fan	Low speed	1.25	1	1.25	4	5
	High speed	2.3	1	2.3	1	2.3
Lights	Outside	0.3	0.5	0.15	1	0.3
	Kitchen - Low	0.2	1	0.2	1	0.2
	Kitchen - High	0.45	0.5	0.225	3	1.35
	Reading (2 lamps)	0.1	2	0.2	3	0.3
	Shower	0.3	0.5	0.15	1	0.3
	Overhead	0.1	3	0.3	1	0.1
Parasitic draws		0.05	24	1.2	24	1.2
	TOTAL			38.68		54.965

pthomas745

@CharlieRN Thank you for donating your time and effort to Tab Science!

I admit to being completely baffled by the 2 way fridges and their power use.  It would seem to me that if the power on the fridge has a "duty cycle:, that the panel (on a good day) should reasonably replace some of the 3.6 amps, and that most of the power draw from the battery would take place in the nighttime hours.  But, I have a propane fridge and will defer to the actual users.  It is very interesting to see all the investigations.

CharlieRN

Thanks to all for the comments and suggestions. It looks like a two-pronged approach needs to be adopted if you intend to boondock with the Boondock more than a day or two: Increase power storage capacity and reduce power consumption.

The most power hungry devices on the stock 320 are the Isotherm refrigerator and Fantastic fan. It’s difficult to get a handle on precisely how much power the refrigerator uses. The Webasto Marine web site states that “power consumption (W/24h) is 360.” If this means average power consumed in the course of day, 360 watts means 30 amps of current used. This is consistent with what I’ve seen in the postings here and elsewhere online that put the Isotherm’s consumption in the range of 2.75 to 3.6 Ah, with typical run times of 8 to 10 hours.

The Webasto Marine website states that “power consumption can be reduced by up to 50 % with the use of an Isotherm Smart Energy Control Kit.” That would be a great, relatively low-cost upgrade (retail for the kit is $150 -  WestMarine presently has them on sale for $90) but unfortunately, installation looks to be real PITA. Based on the video on the Webasto site, not only do you have to completely remove the refrigerator for the install, you also have to drill through its walls in several places. I’m pretty handy, but think I need draw the DIY line at drilling holes in a brand new $1,500 refrigerator. I’m going to ask the dealer if the option can be installed at the factory.

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.

Staying with the fan, I've seen several recommendations for the Maxxfan 5100  because of the built-in rain hood. While the ability to use the fan in the rain seems like a very desirable feature, the Maxxfan seems like an even bigger power hog, drawing over 4 Ah on high. Would be great to hear from any T@B owners familiar with both units.

On the other side of the equation is storage. I think that elbereth’s suggestion to use a pair of inexpensive 6v batteries as a newbie start point makes sense. The weight penalty is not that great (looks like a pair is in the 150 lb range) and should not present an issue for the XC-90 TV. It looks like I’d need to upgrade the solar charging controller however.

Comment and criticism on my rambling and long-winded posting both sought and appreciated.

ScottG

Good discussion, @CharlieRN--you are clearly thinking through your own situation carefully.

FWIW, I don't use the Fantastic Fan all that much for comfort purposes--it's loud and doesn't really point the breeze where I want it. Instead, I have a couple 5" battery fans that I can place where I want and run several nights on 2 D batteries. I also have a repurposed computer fan on an adjustable ball mount that is wired to the trailer's 12V system.

The fridge I suppose is another story. I have a 3-way and use propane when don't have shore power, so the 12V demand is very low. Since the switch to the 2-way fridges in the non-CS units, there has been quite a bit of debate regarding energy usage while boondocking. I think the final verdict on that is a ways away, but my intuitive sense is that more battery capacity will be required by those who want to camp extensively and not be entirely dependent on good solar on a daily basis.  

VictoriaP

Having had both multiple Fantastic Fans over several RVs and a Maxxfan now, I’ll never own another Fantastic Fan. Ever. The Maxxfan is quieter, has more speeds, and that sleek, low profile, built in rain hood makes it a no brainer. Because it has so many speed options, I rarely have to run it on full power, so the fact that it draws 4 amps at that speed is irrelevant to me. Just my 2¢ worth. Don’t opt for the remote control versions if you’re concerned about parasitic draws on the battery though, any device with a remote must use at least a little power listening for commands.

Additionally on the lowering consumption side of things, you can buy 12v powered fans for additional airflow.  Several of us carry oversized battery packs like the Goal Zero Yeti or Jackery models, which will power such a fan for days. Most of us carry at least one solar powered lantern of some sort too. You can add in line kill switches pretty easily to the Jensen stereo and TV (so easily even I managed it!) to decrease the parasitic load as well.

One option it appears you’ve left out of your equations is a generator. While I deeply hate the noise they make, it’s an easy solution for any boondocker. Just run for a couple of hours as needed here and there to further charge the battery. I opted for a tiny 20lb Ryobi as my power backup that runs off 1 pound propane bottles (or off a 20lb tank via a hose adapter) because I don’t want to have to have to lug around cans of gasoline. It’s not big enough to power the A/C, but it’s plenty capable of boosting the charge on the trailer batteries. Gennys have their drawbacks—additional weight, noise, fuel, maintenance, and limitations on operating hours. But they’re good to have around as backup when solar just isn’t cutting it. I can also use a smart charger (NOCO Genius) running off my GZ Yeti to charge the trailer, and have plugs to charge the Yeti off my portable solar panels.

If I were buying a 2021, I’d not only load it up with as much battery as I could find room for, I’d have them add a second solar panel at the factory. While you can relatively easily boondock for days with an older 320 on a single group 27 battery and a mere 100 watt panel due to the propane powered fridge, on a 2021, it’s increasingly looking to me like you’ll do best to max out both your energy storage and generation capabilities.

Sharon_is_SAM

@CharlieRN - we have the MaxxFan Deluxe 7500.  We never use it on the highest settings and it is quite effective on the quiet, lower settings where it sips amps.  But, did you see the thread where owners have altered the Fantastic Fan to make the speeds more variable?  Cheap and effective and uses a lot less amps.

https://tab-rv.vanillacommunity.com/discussion/7200/variable-speed-pwm-ceiling-fan-mod-10-bucks/p1

Your frig will be your largest draw, so if you really only need 3 days of boondocking I would consider more power conservation:

1. If you are not inside the TaB during the day, turn off the fan.  Turn it on before going to bed.
2.  Leave the lights off and use Lucci solar lights.  They are a softer light than the TaB.
3.  Bring a cooler with ice for beverages.  It reduces the amount of time that you open and cycle the frig.
4.  Get a solar charger for phones and devices or charge in your car if you are out and about during the day.
5.  Use a solar shade on the side of the TaB in the sun.  It will help reduce cabin temperature.
6.  Use another device for music or entertainment.  We have a portable DVD player that we charge up before travel.

And, if you get the AGM batteries, the occasional discharge to 80% is not going to reduce your battery duration to the extreme.  Check out the link below.  

https://tab-rv.vanillacommunity.com/discussion/9940/agm-battery-depth-of-discharge-myth-busted

So, I think for the short periods of dry camping that you plan, 235 amps of AGM batteries and a good battery monitor is all you need.

TerryHutchinson

I  also have a new 320 on order.  I also am most attracted to taking it into off-grid territory, so the ability to dry camp is essential for me.  As ordered, the dealer is going to replace the standard 12v battery with 2 6v AGMs.  No modifications are necessary for this change, the two battery boxes fit fine in the larger box.

Your figures for the small isotherm refrigerator are high, it is quite efficient and it only draws power, of course when it is running.  Have the refrigerator well chilled and filled before you leave for your trip, and put frozen blue-ice pack into it where you can fit them.

The 3 way  Fantastic fan as installed is unfortunate.  It uses resisters to lower voltage to the fan when running it at reduced speed - this wastes energy as heat.  You can upgrade the fan to a variable speed unit by installing this:https://www.amazon.com/gp/product/B00F839VNQ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1   It controls fan speed in a completely different way that doesn't squander energy.

The fan upgrade is not complicated if you are comfortable with a soldering iron and have a rudimentary understanding of wiring electronics.  It can make the fan substantially efficient - as well as give you working speeds well below the lowest available with the 3 way switch, which many say is still too fast.

I will also be traveling with a Honda generator that is fairly quiet.  I figure if all my plans go haywire, I can bail myself out with judicious use of the generator.

jkjenn

Hi @CharlieRN

I should point out that my chart was based on the 2015 T@b and I will be updating on the "off season."

A couple of points:

1. I have mostly used the fridge in full sun, pointing south, with hotter temperatures. The weather pattern on PA appears to be moving back towards its usual of more cloudy weather. On my first day of all cloud cover, it did draw less energy. 

2. I have the Isotherm Smart Energy kit installed. I don't have enough conclusive data to share, but early tests have not shown a huge impact. I typically prechill the fridge and stock with cold food before leaving. I have some boondocking on my near future.....More to come. 

3. The Victron BT draws hardly any power at all and the overall phantom parasitic draw for everything (minus the fridge),  is around .80ah, which is very small. My quick tests indicate if there is a big draw in that number, it might be from the Jensen units. Again, more to come.



I have a 100w suitcase panel on order which should arrive before my upcoming trip. I think this will be the solution needed to supplement the factory solar.

CharlieRN

Thanks again to all for the helpful comments and suggestions.

I'll put together a more detailed posting in the coming days but to those who think my estimate for the fridge is high, that information comes directly from the Isotherm website. Here is what it says verbatim for the Cruise 65 Elegance:

"Power consumption (W/24h) = 360"

Perhaps I'm using the wrong model fridge?

TerryHutchinson

The one I saw in a 2021 320 S Boondock at the dealer was the smaller Cruise 49 Elegance - 1.75 cu ft.   Can't say what will be delivered with my order.

jkjenn

TerryHutchinson said:

The one I saw in a 2021 520 S Boondock at the dealer was the smaller Cruise 49 Elegance - 1.75 cu ft.   Can't say what will be delivered with my order.

Are you sure? They would have to change the cabinetry for a smaller fridge.

Denny16

I believe the Isotherm Cruise 65 EL is what the TaB 400 is using for the two-way compressor fringe option.  

Cheere

TerryHutchinson

Well the 520 I saw had the 1.7  12 volt only Isotherm - the model CR49.  I looked at it closely because it was in black, and my wife was not happy with the look.

*** - this is interesting though, the one I saw had a black plastic frame around the refrigerator proper, maybe an inch wide.  I just looked at a couple technical reviews of the new model and there was no frame around the refrigerator. (sadly the cubic volume wasn't mentioned)

jkjenn

This is what the 65 looks like:

jkjenn

FYI, the 320 on the Apache website, if that is where you saw the 320 looks exactly like mine. Did they tell you it was a 1.75 fridge or did you see it on the sticker? 

TerryHutchinson

It was on the sticker - as was the model cr49

TerryHutchinson

Look at this - from youtube it is Nucamp's own walkthrough of the new TAB320 and the guy identifies it as a new 1.7 cu ft Isotherm.  5:50 into the presentation.   However, barely visible on the label before the camera turns away is a model number that I think does say CR65E- though it is not clear.

Sharon_is_SAM

The YouTube video by Princess Craft also says a 1.7 cubic foot which equates to a CR 49 with 340 watts/24 hours.

jkjenn

TerryHutchinson said:

Look at this - from youtube it is Nucamp's own walkthrough of the new TAB320 and the guy identifies it as a new 1.7 cu ft Isotherm.  5:50 into the presentation.   However, barely visible on the label before the camera turns away is a model number that I think does say CR65E- though it is not clear.

There were a couple of small details that weren't quite right in the video and I suspect this was one of them. Perhaps thry were considering the 49 and ended up with the 65. You can tell the difference between the 49 and 65 by looking g at the inside door. 

Sharon_is_SAM

The CR 49 has aluminum brackets to secure bottles on the inside door rack.  The CR 65 brackets are all plastic.

CharlieRN

From the standpoint of power consumption, it does not much matter which model is in the T@B. From the Indelwebastomarine website:

Cruise Elegance 49 - Power consumption (W/24) = 340

Cruise Elegance 65 - Power consumption (W/24) = 360