Need guidance for 1977 VW camper battery & solar arrangement

MRMATT · May 2019

Greetings!

I think I am getting too much information, so am turning to this site for guidance.
Have a well preserved 77 camper bus with aux battery to manage refrigerator and small (8" ) fluorescent tube light.

Camping is planned with family, the current "house" battery that is in the camper is a deep marine battery (EverStart 625MCA) which I am sure is not the best option..

However, I did read the above battery can be fully discharged and charged without much consequence. - surprised me

Refrigerator in camper runs off 12V, draws 60 Watts = ~ 5 amps. Will have 1 small fluorescent (~ 8") light.
When the refrig is not plugged in, it aims for a set warmer temperature ( will still say 60 watts).

I am believing the above EverStart battery is not the best option to have, I was looking at:

Vmaxtanks Vmaxslr125 AGM Deep Cycle 12v 125ah SLA rechargeable Battery
"MAX. Charging Current: 30A MAX. Charging voltage: http://https//www.amazon.com/Vmaxtanks-Vmaxslr125-rechargeable-Solar-Inverters/dp/B00ACNO2AO

Or a Renogy Deep Cycle AGM Battery 12 Volt 100Ah / 10Hr.s http://https//www.amazon.com/Renogy-Battery-Marine-Off-grid-Applications/dp/B075RFXHYK/ref=sr_1_fkmr0_1?keywords=KU%3A+RNG-BATT-AGM12-100&qid=1556923365&s=automotive&sr=1-1-fkmr0

And either this or another similar solar panel
Renogy 100 Watt 12 Volt Monocrystalline http://https//www.amazon.com/Renogy-Monocrystalline-Foldable-Waterproof-Controller/dp/B079JVBVL3/ref=sr_1_3?keywords=renogy+portable+100+watt+solar+panel&qid=1556925573&s=automotive&sr=1-3

And looking at this controller Victron BlueSolar 75/15 MPPT Charge Controller - 15 Amps / 75 Volts, as it will disconnect the load either intermittantly or longer to allow the battery to charge fully by solar, and will disconnect load if battery is drained to a set point.
http://https//www.amazon.com/Victron-BlueSolar-MPPT-Charge-Controller/dp/B00U3MK0CI/ref=pd_cp_86_3?pd_rd_w=UBXAg&pf_rd_p=ef4dc990-a9ca-4945-ae0b-f8d549198ed6&pf_rd_r=JVGEGV1YC47P86KA7KCK&pd_rd_r=43d62aa1-57ef-11e9-9d06-a332060cea22&pd_rd_wg=7UtlK&pd_rd_i=B00U3MK0CI&psc=1&refRID=JVGEGV1YC47P86KA7KCK

I have not looked at any inverters, thought this would be far enough in going until I get feedback if my plan is going ok, or am waaay off base.
Likely will be camping no more than 2 nights at a time ( other night in hotel to keep wife comfortable and happy)

Thanks for any feedback, i tried to keep the above as brief as possible to save reading.

Thanks so much
Matt

billybob9 · May 2019

Hi Matt
If you look at the post right under yours called " how low can you go " the diagram is replacing your 3 way Dometic Which I have done on all my older camper/trailers with a dorm type 4 cubic foot fridge 48W. Everyone will tell you need more power then this but if you pre-cool the fridge and pack it with lots of water/soda you'll be fine, if the sun is shining. The point here is you'll need to get to the temperature where the fridge is cycling from on for 15minutes to off for 45 minutes as fast as possible. I gave up on all my old 12V fridges and would only run them with propane. After you're done using it , It could be your emergency power outage unit. The cost will be about $150 Fridge, $150 Inverter, $100 Panel, $20 Controller , $120 Battery/or just use your vehicle battery. So about $500. Remember keep the panel in total sun light .The slightest shade will bring down your Amps to ZIP.. BG

mcgivor · May 2019

billybob9 said:

Hi Matt
If you look at the post right under yours called " how low can you go " the diagram is replacing your 3 way Dometic Which I have done on all my older camper/trailers with a dorm type 4 cubic foot fridge 48W. Everyone will tell you need more power then this but if you pre-cool the fridge and pack it with lots of water/soda you'll be fine, if the sun is shining. The point here is you'll need to get to the temperature where the fridge is cycling from on for 15minutes to off for 45 minutes as fast as possible. I gave up on all my old 12V fridges and would only run them with propane. After you're done using it , It could be your emergency power outage unit. The cost will be about $150 Fridge, $150 Inverter, $100 Panel, $20 Controller , $120 Battery/or just use your vehicle battery. So about $500. Remember keep the panel in total sun light .The slightest shade will bring down your Amps to ZIP.. BG

The reason " everyone " says more power is needed is because to do it right, more power is needed, making a bandaid solution may work for a short period but will ultimately end in dissapointment, refrigeration is a high demand load, if done properly. No disrespect intended.

mcgivor · May 2019

@MRMATT
If the refrigerator is a thermoelectric type 12V unit, it will run continuously which will require 120Ah itself for a 24 hour period, there are some 12V compressor types available, but even with them a higher battery capacity and array will be needed. Then again raiding the motel ice machine with a large cooler may get you through a couple of days, speaking from experience, only I didn't stay at the motel, you would be legit however. Things done in my youth.

billybob9 · May 2019

To do it right costs too much money and nobody is going to pay $1500 and up just to run a dorm fridge. Not for just a camping trip any way. So last night we had a black out and I looked down the street to see how many emergency systems went on ( lights ). The answer is none. So if this were the whole city for 7 days I'd hate to tell you what would happen. Today I'm running my little Dorm fridge off my very week car battery and one 100W panel with no problem. No disappointment here and if the black out was still going I would be very disappointed if I had nothing. I respect your opinion very much but in this case survival is might be more important than doing it the right way. Sorry for Highjacking the post..

Estragon · May 2019

AFAIK, running any lead acid battery down to dead will lead to a short life, especially if it's left in that state for any length of time.

Generally speaking, "marine deep cycle" batteries are a sort of hybrid between a starting battery and true deep cycle.

To run a DC compressor fridge on my boat, I have a pair of 6v flooded GC2 batteries in series which is ~225ah at 12v. The fridge uses ~100ah/day keeping precooled food cold. 50% discharge is about as low as you want to go regularly, so that means about 1 day before recharge is needed.

With the 100w panel, and in good weather, you might offset ~1/4 to 1/3 of the fridge consumption, so with that and a bit of ice you may get 2 days to 50% discharged on a pair of GC2s. I suspect using a single 100ish ah 12v battery for 2 day trips will mean frequent battery shopping though.

billybob9 · May 2019

I must make a correction on my one panel system. If you're camping in Death Valley and the temperature is 120 degrees F then you would want to bump it up on the panels and batteries as your fridge is running constantly (maybe). My test is at 81 degrees max. As you can see from my photo the air temperature is 41degrees F and the thermometer is 38 degrees F. This was done by turning the fridge to Max and shutting it off for 12 hours. So it stayed cold for a pretty long time thanks to the Corona's.

MRMATT · May 2019

Thanks for all of the information, I really do appreciate it!

BillyB, I have heard of people replacing the refrig ( and it would have been great if mine ran off of propane) but I am wanting to keep everything stock in the vehicle   ( I am a stock guy). The camper was stored for more than 30 years, everything in it is original except for the front seat fabric being redone.

Any additional cooler detup would take space, and space is at a premium on camping trips, with a few people, - so am wanting to maximize the ability to use this Dometic.

The last campout I did, I did get the refrigerator cold, by an overnight plug in to my garage outlet. Went on a 2 hr road trip, where we stopped for hours at various places, and the battery was still measured to be ok, by an onboard meter. (What the meter is calibrated to, I am not sure), but the food was still cold, but then again, when the camper was running it was charging the aux battery, feeding the refrig.

Perhaps i just need to do a real test with refrigerator, plug in overnight with it packed with some freezer bags, and food, then take it off power and measure refrg temp and battery V, and outside temps..However,.... the AH on this battery is not known.. .so it it worth doing?

Estragon  My space for the aux battery is limited to the size of a traditional car battery size, so having 2 6v flooded GC2 batteries looks absolutely great for AH, there is no space in the aux battery area for two of these.. I could scavenge a storage area under the bench seat, but that area is needed for items.

It is hard to determine true needs of amp supply from the battery,due to times expected in taking road excursion to visit sites while camping so there the aux battery is being recharged, which is feeding to the refrig ( to whatever extent) while driving. Guess looking at worse case scenario would be 24 hours of not driving.

Excellent concise and informative drawing BillyB. in your "How low can you go" post. thanks for that reference.

So basically,
- I would have no qualms about getting 2 - 3 100 watt panels, some are extremely thin (storable in bed space) and are reported to be of good quality.
- Seems without scavenging needed space, there really is no battery or battery configuration Ahs I could get which would exceed 125 (?) for the space i have (?).
- And I will have to test how long the pre-chilled refrig having food, drink ice packs just running on this aux battery, when disconnected from shore electrics. Again, not sure how much of value the results will be with this kind of battery ( Marine EverStart)
Guessing at the very least the battery I have, should be replaced.

Forgive my ignorance, but as the refrig literature says 60 watts; so, with running on 12Volts, that equals 5 amps... is that 5 amps per hour?

mcgivor : "If the refrigerator is a thermoelectric type 12V unit, it will run continuously.." I am not sure if it runs continuous or cycles on battery power

Thank you with your time in helping with this - will be conducting the test and see what I get - might need a weekend tho.

BillyBob: "My test is at 81 degrees max. As you can see from my photo the air temperature is 41degrees F and the thermometer is 38 degrees F. This was done by turning the fridge to Max and shutting it off for 12 hours...." I will try this also

Matt

Blackda3 · May 2019

I used to be an 1989 VW Vanagon. I am also a huge fan of Victron equipment. Major kudos to Dometic for making a 12v/propane refrigerator that continues to work after 42 years while being bounced around inside a van.

I am also far from an expert on anything. However, I am very good at making measurements and keeping notes. My old vanagon's Dometic, RM182, and my current Aliner trailer, RM2354, have the same ammonia absorption refrigerator. They both were unable to cool less than 50 degrees ambient. If you wish to struggle with this approach, there are a lot of tips and tricks online to improve it’s performance.*

As one of the previous posters has pointed out, there’s a cost to high efficiency/true refrigeration. There are also a number of decisions: do you want to keep it stock perhaps for future resale value; or, do you want to customize it and plan on keeping it forever? There’s also the dilemmna of where to install a new unit i.e. the stock location or possibly moving to another location within the van. (Note - a dorm style refrigerator is too big to fit the stock location.)

Since you mention a very small “window” of time for needing refrigeration, you may want to consider leaving the unit stock or just using “blue ice” from Yeti or similar to keep drinks cool. You could use ice and a Yeti or similar good quality cooler for your other perishables.

My design parameter was based on my desire to keep my food cold/frozen no matter the ambient temperature for 3 days or longer (as well as the soggy vegetables problem i.e. happy wife happy life).**

Let me outline my solution and provide some links for you to make up your own mind. I installed a Truckfridge (aka Vittrofrigo) from Westy Ventures into the stock location. The owner is a huge resource on various VW forums like some of the individuals here. West Marine and Go Westy sell the same or similar units. My unit was not as tall as the stock unit but actually had more useable cubic feet in addition to a small freezer.

In order to power it, I installed two 105Ah AGMs under the back seat, including the requisite fusing, switches, charge controller, and routed my wires from there through the engine compartment, up through the air vents (cowling) to the roof. On the roof I had two 140 watt panels mounted to a set of IronRidge rails which sat on Thule bars with gutterless feet bolted into the pop top. This was a parallel configuration wired to a Soladeck combiner box. I also installed additional lifting struts due to the weight.

I had another (auxiliary) battery under the driver's seat powering the interior lights. This location is really small. I used sealed batteries since I had to lay them sideways to fit. I kept the solar system batteries isolated from the starting and auxiliary batteries (which were connected to the alternator). When parked/camping the starting battery was also isolated from the auxiliary using a relay. The starting and auxiliary were connected together only when the engine was running. I also had to replace multiple auxiliary batteries, I suspect, due to the small size of the cables which provided insufficient charging.

I used Campsitephotos.com to find sunny campsites. I would try to park facing North so when I opened the pop top it would be pointed South. I was often in float by 1 or 2 pm.

Camping in shade required deploying a set of flexible panels and/or maximum energy conservation. (These were PowerFilm which I don’t recommend.)

I also had a 1000 watt Xantrex inverter connected to the two 105 Ah batteries to provide AC. In retrospect, I could have made due with a smaller inverter since I was usually charging phones and laptops. This worked fine since I was generally charging in the afternoon with the excess power.

Links for further research below. Huge shout out to everyone at Wind-Sun that helped me piece this system together as well as BB here for all of his sizing templates.

http://westyventures.com/index.html

http://www.westfalia.org

https://www.gowesty.com

https://www.thesamba.com/vw/

* I'm actually removing my brand new RM2354 Dometic 3 way icebox from my Aliner in favor of an IsoTherm Cruise 130. The RM2354 will be up for sale (almost new condition).
** I also installed a Propex heater to keep my wife warm.

Happy to provide further support off-line via email. Good luck with your project.

littleharbor2 · May 2019

One thing that really helped my propane fridges performance in my 5th wheel was to mount a muffin fan under the fridge's coils to speed up airflow over them. I had just tapped into one of my solar panels leads and switched the line so that the fan wasn't running when the fridge isn't being used, otherwise the fan runs when the sun shines.

Estragon · May 2019

Doing a test run in something like real world conditions is an excellent idea IMHO. That way, you'll know what to expect and can plan accordingly.

Amps is a rate (like MPH), not a quantity (like distance). So a 5amp load run at 100% duty cycle is 5 x 24 = 120amp-hours/day x 12v = 1440 watt-hours/day. A 125ah battery (when new) would be discharged completely in less than a day at that rate. Used in this way, it will lose capacity fairly quickly, and behave like a progressively smaller battery.

If you want to stay with stock fridge using that much power, and can't add more battery in space available, another alternative is to get something a small generator (eg. Honda eu 2000i) to supplement solar charging, and/or run engine for alternator charging. You may want to check if the stock alternator is okay with sustained charging load. Some are designed for just short top-up charging of starting battery and will reduce output a lot if they heat with sustained load. Yours may have better cooling etc for this, but you may want to confirm.

I find the small generator works better. Alternators tend to want high-ish RPMs for decent output, and in my case I prefer not to run the boat diesel with just the alternator load. The generator has an eco mode that adjusts speed (along with noise and fuel consumption) down according to charging load.

Blackda3 · May 2019

I found some of my notes and forgot to mention the most important lesson I learned.

My unit was a Truckfridge TF49. Per the link below, the manufacturer claims 340 watts per 24 hours. However, I’m pretty sure my usage was closer to 500 watts. Adding sufficient solar during the day to recharge the battery and power the refrigerator was simple, balancing the battery size and expected overnight loads pushed me towards using more batteries.

I forgot to mention the most important lesson I learned. Weight is the biggest problem. My stock 89 vanagon, when loaded with way too much camp gear, could barely climb long grades (think 2nd gear, 4000 rpm, dodging semi-trailer trucks, and watching my temperature guage like a hawk). It quickly dawned on me that I was auditioning for a Darwin award with the lives of my family. This led me down the very expensive rabbit hole of a subaru engine conversion.

Yes - I still love VW vans. I sold my vanagon last year and I miss it every day (definition of crazy?). Simply put, if I had to do it all over again, I should have bought a pickup truck.

If you are planing long trips, may I suggest: AAA premium towing coverage (150 miles); Think more along the lines of backpacking (minimal gear); Look for alternative camping approaches (i.e. sleeping in the back of the van only as a last resort and stay in BnBs, Hipcamp, or other cool locations).

Please think long and hard about how your goals and the effect of increasing the weight in your ’77 van. In other words, it's really easy to over pay for the "cool" factor.

https://www.truckfridge.com

BB. · May 2019

Just a clarification... probably talking about 340-500 Watt*Hours per day... The "quantity or amount" of energy consumed per day by the fridge.

340 WH per day / 24 hours per day = 14.2 Watts average load

If the refrigerator runs 15 minutes per 60 minutes---Or a 25% duty cycle, the actual motor running power would be:

14.2 Watts / 0.25 duty cycle = 57 Watt running power

Also, the energy usage goes up every time you open the door, add "warm food", or make ice, you are in a hot climate/no A/C, etc.... And it can go up quite a bit.

-Bill

MRMATT · May 2019

Blackda3; thank you for the input, I am very familiar with GoWesty , and Thesamba, being going to the latter for about 15 years, Scouring those forums has helped, but not find much of a consensus, and info is all over the place. I am definitely wanting to keep the camper stock, in part that is how I am, - I doubt I will ever sell in as my daughter since 8, now 21 if a big VW fan, and in her mind has already inherited one of my VW's and this baywindow camper, and she likes stock more than me.
Yes, I am considering under the backseat, but I think I really do need that space... have levelers in there, stabilizers, child's cot and not sure what else at the moment. I like the idea of wiring up through the air vents (cowling(?)) to the roof, if I choose to put panels up there, my gutters in small part are being used to mount and ARB awning, but perhaps in time i can find another support for any panels I put up there, as I really don't want to be drilling into the fiberglass top.. ( even though I am good with fiberglass repair, so could patch it if needed.)
I do have the lifting struts, so my daughter can lift the top. I can always modify the struts for heavier duty if I am putting panels up there. I will check for any room near/under the seat of my bus for a small battery for a chance to have additional power. How do you recharge that battery?
If I do put 2 batteries under the seat, I think I would go with two 6 volt 220 AH GC2 deep cycle, as they seem to provide much more amp hours than a single 12 volt battery,..unless I am missing something, which in part is why I am here.

What were you using the aux battery for? to supplement your solar for a specific task? My aux battery is "sensed" by a relay, if it falls below a certain voltage, the alt will charge it.. of course only happens when engine is running.
Thanks for the tip of Campsitephotos.com to find sunny campsites, very helpful, I will remember to park North-wise if I do get top solar panels, but for now choosing thin ones that will fit between the folded upper bed, which can be deployed to face any direction. But then again, you could be charging your solar batteries while your camper is moving. I will keep in mind and check out your components and their setup. So many options out there. I def want a battery monitor that would disconnect any load from the battery (ies) to stop the voltage going too low so as not to sacrifice the battery.

I am thinking that 2 6volt batteries may fit in my aux battery area if I turn them 90 degrees. It would be close.

Yea, I am aware also of a Subaru engine conversion, a person in my VW club does that conversion. Definitely I do see an advantage, but still like stock and I do not have the $$ to put out.. maybe I should have added a few more $$$$$$. Nonetheless, there are still those in my club who do long camper trips with stock engines.

Thanks for the note for the AAA extended coverage, I have heard of that, and forgot that. I heard I can get it, and my wife can get it, so the miles may be additive.. will check on that.

I've gone backpacking a lot, and am aware of the bare necessities to bring. I want to pack light, and take my time getting anywhere; I will be in the slow lane

Estragon, & BB. thanks for the calculations, both of you are looking at it in a way I am not, so I am not focusing perhaps on the right thing. Your emphasis is on Watts, and/or Watt/hours I guess for a while my focus is on amps....rather amp hours. Does not Amp/hours determine how long a battery will last under a specific load in amp/hours? I use Watts to figure out the amps,

So, what is a Watt? I just looked it up and found this.

"Is watts per second or hour?

Power is nothing more than the rate at which energy is used. The familiar unit, the Watt, is simply Joules per second. A 100 W incandescent light bulb is spewing 100 J of energy per second in the form of light and heat. It does not make sense to talk of Watts per second or Watts per hour."

So Bill, when you calculate and find "14.2 Watts / 0.25 duty cycle = 57 Watt running power" What does that information give, unless it is converted to amp/hours? How do you use that information in my situation?
Sorry for being thick headed, but I probably been thinking about things wrong, but am learning!

Thanks again to all for your time for feedback... Have to admit, contribution to this forum is amazing.

I will be trying to do a "real test" with the fridge, and battery that I have -and monitor everything.

Matt

BB. · May 2019

Matt,

Your last two posts got caught in the Spam Queue... Not sure why other than two posts really close together (in time), and/or the links to our user names (more links, the more chance ending in spam queue).

Anyway, regarding Amps and Watts.... Yes, you can use Amps and Amp*Hours for your calculations--Works best if all of your loads/charging sources/battery bank(s) are the same voltage (i.e., everything is 12 VDC).

It does get confusing when you have an AC inverter and a major part of your loads are at (for example) 120 VAC... Then it usually is less confusing to convert everything to Watts and Watt*Hours, and convert back to Amps and Amp*Hours when needed (wire gauge, battery bank AH capacity, rates of charge, etc.).

Technically, an Amp is 1 coulomb of charged particles per second moving past the measurement point. Sort of like gallons per second.

A Watt is a unit of work per second (Joules per second). It takes into account the voltage (like pressure with water flow... 1 gp..s at 1 PSI is much less energy than 1 gps at 10,000 PSI).

You are also correct that the SI units are "per second"... However, much of what we use energy for these days to run our homes/work/industry, we use "per hour" as the "non-SI" base units... 60 seconds per minute * 60 minutes per hour = 3,600 seconds per hour... So, all of our Amp*Hour and Watt*Hour units simply use "Hour" as the base time unit (and other prefix units like 1 kW = 1,000 Watts for our home energy billing; 1 MW = 1,000,000 Watts used for large industry/utility power plant scale).

To give you an example of why we typically use Watts and WH vs Amps and AH... Say you have a load at 120 VAC that draws 1 amp.

1 Amp * 120 VAC = 120 Watt
120 Watts * 2 hours = 240 Watt*Hours
1 Amp * 2 hours = 2 AH at 120 VAC

And then, how many amps and Amp*Hours does the battery support (ignoring losses). Your battery bank is 12 VDC, how many Amps and Amp*Hours does it take to run you 1 Amp load for 2 hours at 120 VAC:

120 Watt load / 12 VDC = 10 Amp load at 12 Volts
240 WH load / 12 VDC = 20 AH (running your 120 Watt load for 2 hours drawing from your 12 VDC battery bank)

We have had people make the mistake that 1 Amp load is 1 Amp load without taking Voltage into account. But, as we see above a 120 Watt load running for 2 hours is 2 AH @ 120 VAC, but 20 AH @ 12 VDC.

Watts and Watt*Hours are "complete units"... They contain all the needed information for use to do power and energy calculations.

Amps and Amp*Hours are "partial units"... If everything is 12 VDC, then there is not much confusion and you can remain in the A & AH realm without much confusion.

But when you are working with a 24 volt battery bank, some 12 VDC and 120/240 VAC loads, etc... It is "easier" to convert everything to our "complete units" (W and WH), and only convert back to A/AH @ XX Volts when needed.

So Bill, when you calculate and find "14.2 Watts / 0.25 duty cycle = 57 Watt running power" What does that information give, unless it is converted to amp/hours? How do you use that information in my situation?
Sorry for being thick headed, but I probably been thinking about things wrong, but am learning!

Basically, it is a way converting "average" power (Watts averaged over many hours), and what the motor actually takes when it is running 15 minutes every hour (as an example). I.e., it is running at ~57 Watts for 15 minutes, and Zero Watts for 45 Minutes out of every hour (on average).

When you put "warm stuff" in the fridge and/or in very hot weather, the compressor may run at 50% or even 100% duty cycle--And draw more energy at this time (you want to design your system to supply "average worst case power").

You don't want your fridge/solar power system to "go dead" (run out of energy) when you put your food from the shopping trip in the fridge (take 100% duty cycle on the compressor unit the "new food" is brought down to temperature).

Is this sort of making sense?

-Bill

MRMATT · May 2019

Bill,

Yes, that does help quite a bit - I will be reading it a few times to really let it sink in... Your calc.s help quite a lot, and this sentence of yours "Basically, it is a way converting "average" power (Watts averaged over many hours)," as well as the analogy of amp vs Watts as water, - and your point -

" We have had people make the mistake that 1 Amp load is 1 Amp load without taking Voltage into account. But, as we see above a 120 Watt load running for 2 hours is 2 AH @ 120 VAC, but 20 AH @ 12 VDC starts to make sense." - would never have occurred to me.

Thanks! Let me take it in, and if I have any questions, I'll let you know. Appreciate you taking the time to educate!

Matt

Blackda3 · May 2019

Mr. Matt – I’m sure we have a lot in common. My daughter almost cried when I sold my ’89.

I also wanted to keep my van as stock as possible but decided my goal of real refrigeration was more important. That led me down another road but that’s another story…

To answer a few of the questions you posed:

- Battery Monitors: Bogart TriMetric and Victron. I really like Victron's apps for my iPhone.

- Panels: There are several manufacturers offering all inclusive solar suitcase systems (very convenient) but I found most of them to be over-priced for what they offer.

A special note that our host, NAWS, is finally offering Sunpower 170w Flexible Solar Panels. I’ve been shopping these for over a year! Currently 10% off. I know the price is “high” now due to its inclusion on the tariff list (perhaps someday…). These would fit really well between the bed and roof.

- Auxiliary Battery: I don’t recall if the auxiliary battery on your ’77 was under the driver’s seat like my ’89? The space under my driver's seat was about half the size of my starting battery (Group 24?). I was able to fit a small Optima on it’s side but the stock charging cables were simply too small to adequately transmit the power (amps). I ran my interior light over the stove but not much else.

As BB and Estragon have pointed out, there are a lot of trade-offs between your ability to store and use energy. Try to model the different scenarios/solutions as to how much power you would need vs. your ability to store sufficient power. Unless you are camping in warm weather (over 80F) the propane will work (be sure to use a fan to circulate the air). You are actually lucky that’s an option – I was able to get my old Dometic started exactly once on propane.

Something else to think about – while lead-acid batteries are considerably cheaper than Lithium Iron Phospate (LFP), the weight and size savings of LFP are huge. However, LFP is likely to remain a very expensive option for the foreseeable future. It will be interesting to see if LFP drops in price if/when solid-state Lithium batteries ever make it to market.

The following site has an incredible amount of information – worth spending a lot of time to study: http://www.smartgauge.co.uk/technical1.html

In sum - you need to define the scope of your project and then what will fit. Trying to stay “perfectly” stock, at least in appearance will be doubly difficult. I have seen a few installations of a modern refrigerator while retaining the original door but that doesn’t answer the dilemma of providing sufficient battery capacity.

A couple more suggestions to help “reclaim” some space to make room for the batteries:

- GoWesty – luggage rack bag. I had an earlier version and it leaked during rain. GW claims their current version is better.

- I bought the GoWesty rear bumper and mounted a rear hitch rack. I then stacked 6 Rubbermaid ActionPackers (8 gallon size). I realized later that stacking boxes like this blocked my tail lights and turn signals. I added auxiliary brake lights and turn signals to compensate.

- I also found stacking boxes from the Container Store. I ran a strap around them and secured it the to front passenger seat so it wouldn’t tip over.

- I also considered a trailer approach but decided against it. See Yakima Rack n’ Roll or their Easy Rider (new).

Photos:

This photo illustrates the stacking boxes behind the front passenger seat as well as the luggage bag.

Here's a photo of the bumper along with my solar panels on the Thule racks. The GW spare tire is hiding a Fiamma awing behind it.

A photo of boxes stacked up on the rear hitch rack. Yes - all of that other stuff on the bench was in the van. I had to empty that stuff out to make up the bed before sleeping. Location: Red Rock Canyon Hwy 14 near Cantil, CA.

MRMATT · May 2019

Hi Blackda3

Thank you for the commentary, much appreciated. Yea, my daughter was into VW’s when she was about 7, and now 21, she still loves them and is really excited about the bus which I got almost a year ago.

I am also leaning toward the Victron, the phone app is convenient, but again looking for something that will disconnect the load from the battery if the battery gets to 50% or so..seems like the Victron does this.

I checked the Sunpower 170W panel price.... and it was quite shocking ( no pun intended). Still looking at the briefcase panel and the thin panels, at a much lower price with favorable reviews.

For my 77 bus, the aux battery is in the engine compartment on the opposite side of the engine across from the starting battery. There is a very small space behind the seat,, lime maybe 4 inches or so.

I am thinking I may be able to fit 2 six volt batteries if I turn them sideways, it will be a very close fit. I will have to measure exactly before I order them. Each 6 volt battery is rated at 200Ah, so I am thinking this would give me 400Ah if I connect them to make them a "12 volt battery"

I do have the luggage bag, not from GW, but onsite somewhere else, just a huge duffle bag – could put a body in there & was ~ 20$. Everything in there will be ok if gets wet.

I think I will need to do a “practice pack” before I go to see how much stuff I am dealing with., I am a minimalist, but with my wife and daughter…. who knows what restraint I will have to enact.

Beautiful site – seems like an amazing trip and nice looking, and well prepped van there. I hope I will not be needing nearly that many items at least on this trip. I really like the rear hitch rack, have to check into that.

Unfortunately I will not be able to do my refrig test this weekend as it will be raining and cold , and as we have only one garage, thought I let my wife have it for her car, …

Tecnodave · May 2019

@MRMATT,
Two 6 volt 200 a.h. batteries in series make a 12 volt 200 a.h. battery. The volts add in series, the a.h. add in parallel, but total stored watt hours doubles for the two in series or the two in parallel.....hope that makes sense..

MRMATT · May 2019

Thanks Tecnodave, I was thinking if I was wrong about additive amp hours, someone here would correct me.. thanks for setting me straight. Shame the physics don't work out that way

Still will give me more A/h as compared to the "average size" battery; I have been looking at... there I am seeing no more than 125 A/h for what I can fit.

Thanks again for the education

MRMATT · May 2019

OK, did a real life test, and recently something bad happened maybe someone here can give me an idea...
2 weeks ago, Life test, went to camp/show, refrig half full of food goods
Auxiliary battery dedicated to the refrig is a Deep Cycle Marine battery.
Camper plugged in overnight, refrigerator running on shore power.
Temps in Fahrenheit
Volts when taken are of Deep Cycle Marine battery. running refrig
This camping was kind of a busy - lots friends there, lots of activities, so info is not as complete as I would like

Time Comments Temp Outside air Temp in refrig Volts
0 now put in ice packs (5) 65.8 24.2 12+
40min Put food in 67 28.2 12+
48min Food still in 68.5 31.6 12+
50 min Off shore power, leave house: Refrig goes to default temp, sustained by alternator
3 hours Park at camp; refrig on Aux battery 80.5 41.1 -
5.5 hours 76.7 43.3 12.06
6.5 hr 75.3 40.2 11.97
7.5 73.8 40.1
10.5 (7pm) Turned refrig off due to low V 73.5 49.5 6.75

So it looks like I got ~6 - 7 hours on the battery. Food was still cold enough the next morning.

Now the strange thing.
When I got home, I measured the volt of the battery, and was 12V, ( recharged by the alternator) but for whatever reason I put my charger on it to do a battery check ( which my charger can do in a gross way) It said the battery was only 20% charged. So I left it on for an hour.

The following week... (yesterday)
I repeated the above temperature test with only 3 icepacks, hotter day ( ~ mid 80's), car not running, reffrig on aux battery only, battery only lasted 2 hours before getting down to 6.5V. I did off shore charging, and in 15min was back up to 12 V.(!)
I put it on my charger on it, it said again only about 20% charge. To see if there would be any change of 20% charge, charged at 2 amps for one hour, still 20% charged, charged at 4 amps for about 3 hours, never got above 20 percent charged. Checked battery voltage. Read Zero. Left over night, still zero.

Not good.

So am back to getting a battery. I am looking at 125 Ah battery with 3 solar panels. Kinda frustrated.
Battery charger is reading/charging an extra car battery and lawn tractor battery just fine, tested this morning

Estragon · May 2019

Depending on the battery, 12v is roughly 40% state of charge. If the battery has a capacity of (eg) 100 amp-hours, that means you have to put back ~60ah. A 4a charger would take about 60÷4a = 15hrs to charge.

Going from 6.5v to ~11v (or 11v to 6.5v) takes/has almost no energy, and happens fast. Once in the useful capacity range (~ 11-12.8v) more energy is used/supplied, and voltage changes much more slowly. True deep cycle can be charged at a rate of ~C/5, so a dead 100ah battery could be charged at a rate of about 20a, and would take about 4 hrs to get to 80%, and maybe another 2-3 hours to get to near full. Many sealed batteries can take higher current (eg C/2, assuming 50a charging is available), but will still take multiple hours to charge from dead.

All the above assumes a good battery. Running down to dead tends to do bad things to a lead acid batttery, and the battery may have permanent capacity loss and/or other damage.

It's hard to tell what the alternator did in terms of charging and running the fridge. Under sustained load, many will heat up and throttle current so they don't burn out.

Does your meter do voltage in tenths? There's a big difference between (eg.) 11.6 and 12.4v. They both round to 12v, but are a big state of charge range.

BB. · May 2019

Also, Lead Acid Battery voltage measurements vs state of charge vary a lot vs no load and rested for 3+ hours and under load while measuring... I.e., if you guess that 12.1 volts is 50% SoC after resting 3 hours (no load, no charging). Then you are looking at possibly 11.5 volts while under medium level of discharging current for that 50% SoC (also depends on temperature, battery type, age, service history, etc.).

Taking a battery "dead"--It can ruin the battery immediately... A new battery, quickly recharged may come back for useful (albeit shorter) life. A battery with 1+ years on it, stands a good chance of never being "reliable" again (may die tomorrow, may die in 2 weeks).

Basically, taking a FLA battery below ~20% state of charge, because of normal cell capacity variation (+/- 10% of nominal AH capacity), an FLA battery taken below 20% SoC stands a chance of a "weak cell" actually going to zero and even negative state of charge (reverse charging). Most rechargeable cell chemistries--A "reverse charge" is "death" to a cell.

Standard "automotive" chargers do a "sort of OK job" of charging the vehicle SLI battery (starting, lighting, ignition). And most SLI batteries are really only designed for 15% or so discharge (aka cycling to 85% State of Charge).

Most standard alternator systems don't charge deep cycle batteries very well at all... Between lower charging voltage (typically around 13.8 to 14.4 volts, where FLA really needs closer to 14.8 volts) and time (an FLA battery taken to 50% SoC needs something like 8-12 hours to recharge--Most trips are not that long, or every day). And add voltage drop from alternator to house battery (typically only allows 10 Amps max current flow and more than 0.5 volt drop), and automotive alternators cutting back on current output once they get "warmed up"--The vehicle alternator may (at best) just keep up with house loads when the vehicle is running--And never really/truly charge the house battery.

There are DC to DC charge controllers that take 12-15 volts DC input from the vehicle battery system, and output 14.75 volts (or whatever you set) to charge the house battery... Or you can even put an AC inverter on the vehicle battery and use it to run an AC to DC battery charger for the house battery--Of course, you have to make sure you don't "kill" your vehicle battery while doing this.

Running a refrigerator as an RV load--It is difficult. The 5-10 amps of constant load (or 50% duty cycle once the contents are "cold")--It adds up to a lot of energy that has to be replaced (typically daily).

Lead Acid batteries--There weakness is that it takes time and sufficient voltage to fully recharge. NiCad, LiFePO4, and other batteries, can recharge very quickly and are used in applications where light weight and smaller size is important (like aircraft, portable devices, etc.) where you can recharge them in an hour +/-... But costs and charging system design issues are a stumbling block here.

-Bill

billybob9 · May 2019

MRMATT
Thanks for doing your fridge test. It looks like running your fridge on aux battery did nothing to reduce the temperature rise in the fridge. I did better with mine just unplugging completely. Of course I probably had more Corona's then you but I still stayed in the safe zone. As far as charging, my charger says it all with Trickle 2A, Fast Charge 10A and Emergency Start 50A. This was meant for car batteries but a ball park for all I think. Spent some time this week going to places that sell batteries. Getting INFO and prices was very interesting trying to figure the best options for what I wanted to do. Tecnodave can probably get you in the right ballpark if that's your intention. Thanks Again, Great job.....

MRMATT · May 2019

Thank you all;
Thanks Billy, again unfortunately this test was not done under the best test conditions, as it was live. A bit before 7 the refrig was opened numerous times to dig around to find the desired food to be taken out; possibly that was the reason for the increase in temp (that's when I think of "oh yea, time to take the fridge temp". The fridge was about 1/3 full, so not a whole lot of mass there, especially when 95% was of the contents was not liquid. Who is Tecnodave?

Again still strange to me the battery went from 12+ V down to nothing during the charge;
"Basically, taking a FLA battery below ~20% state of charge, ....., an FLA battery taken below 20% SoC stands a chance of a "weak cell" actually going to zero and even negative state of charge (reverse charging). Most rechargeable cell chemistries--A "reverse charge" is "death" to a cell."
So possibly a weak cell was formed during the recharge? Was reading 13+ volts and then ~ 0 in a short amount of time. I was wondering if the charger was not good for the battery. Seems if I left well enough alone,............. but then again, it did not hold a charge as it did previously.

"Does your meter do voltage in tenths?" Yes it does
"There's a big difference between (eg.) 11.6 and 12.4v. They both round to 12v, but are a big state of charge range."
Now that you mention that, I think I have observed that.

BB. And add voltage drop from alternator to house battery (typically only allows 10 Amps max current flow and more than 0.5 volt drop), and automotive alternators cutting back on current output once they get "warmed up"--The vehicle alternator may (at best) just keep up with house loads when the vehicle is running--And never really/truly charge the house battery.
At this time I am not sure if the limit is 10amps, I would hope with the design of the aux battery VW back then new enough for what amps should be supplied, I don't think VW originally had a traditional automotive battery fo aux battery; I have not been able to fine info on either.

And all, thanks for the amazing quick reply esp on a holiday!
Matt

Need guidance for 1977 VW camper battery & solar arrangement

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