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Old 08-17-2019, 12:54 PM   #51
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Thanks for the drawing, Rick!

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Old 04-28-2020, 09:15 AM   #52
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Improved Isotherm 65 Fridge Efficiency

While laying in Starr's bed last summer I'd notice that the Isotherm 65 fridge was running a lot -- if I remember correctly, it ran about 1/3 of the time during ~80°F cabin temp. So I pulled the Fridge out and noticed two things:

* The fridge's fan and condenser cooling coils were located at the rear top right corner, but the cabinet's vent port was lower, behind the driver seat. So it seemed to me that much of cooling air was probably just recirculating around the fan; i.e., the air that was cooling the coils was probably much warmer than the van cabin's ambient air.

* There was room between the fridge and it's surrounding cabinet for added insulation.

So, I fashioned baffles/walls/separators out of corrugated plastic to separate the fan's input area from the cooling coils' exhaust area. One piece of the plastic was very carefully cut to just touch the van interior's outside wall when the fridge was fully pushed in -- to form a tight vertical "wall" between the input & exit areas. I then added 2 layers of 0.3125" thick Reflectix roll insulation on the top & 3 sides of the fridge (not on the bottom). And I left the added insulation off a triangular area below the fan assembly, down to the cabinet vent port -- forming an exhaust plenum running diagonally down the fridge's right side. I used HVAC foil tape on all insulation seams.

As a result, I believe that the fan is now drawing in cooler air pulled from under the fridge and/or from a behind-cabinet-opening to the left, from the under sink area. That is, the fan no longer pulls back in already-heated air from the condenser coils area. The result seems to confirm this: the fridge runs less frequently and the average daily summer power consumption decreased from ~30Ah to ~20Ah. An added benefit: the fridge is quieter (although was quite quiet to begin with).

If I were to do it again (& I might ), I'd use the following better insulation than Reflectix: US Energy Products Reflective Insulation Shield, Heat Shield, Thermal Insulation Shield Vapor Barrier (24" x 25 FT) (1/4 inch Thick)

Hopefully these pictures help illustrate what I did:
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Old 04-28-2020, 09:47 AM   #53
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Nicely done!
This deserves additional thought and a place on the to-do list...
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Old 04-28-2020, 11:41 AM   #54
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Very nicely done. Thank you for the write-up. Definitely on my to-do list.

It seems that in the RB-150 layout, there is no direct escape path for the warm air that comes off the coils. I wonder if something could be done to make this even better by providing a more direct exhaust path for the warm air.
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Old 04-28-2020, 12:30 PM   #55
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I was concerned about how easily the exhaust air would be pushed down thru the plenum to the lower vent opening. So I did think about cutting a vent opening next to cooling coils, but I store my Lagun tabletop on the outside of the cabinet and any vent opening would mostly covered by that tabletop.

I also thought about installing another assist fan, but thought that I'd try the described passive solution first. And I find that the fridge's fan seems to have no problem exhausting air down the thin plenum (I did make it especially wide).

I have taken temp readings and the exhaust air temp was only slightly above cabin's ambient -- just as I'd expect for an efficient solution!
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Old 04-29-2020, 02:10 PM   #56
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Awesome. Thanks for sharing.
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Old 04-30-2020, 01:22 PM   #57
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Lithium at 1 Year

Well, Starr's been in the family a little over a year and I finally feel like I have a pretty good handle on his power setup...so, it's probably time to share with this community! The quick summary is: all the power components (except a battery monitor) worked from day one and I'm very happy that I went Lithium. But it took the entire year to really feel comfortable with the electrical components and tune them for best performance. I'm going to briefly cover the highlights in this post, but you can read the full details in Starr's Guide, http://rick.samcos.com/StarrVan/StarrGuide.pdf (the Electrical section in the Appendix also has much of the detail). The Guide is a living document that I intend to continue to update as experience is gained and new equipment installed; and I'll leave it accessible on the web. It has lots of info besides electrical that folks might find useful. Now, for a synopsis of the past year re the electrical systems...

The first few months were mostly consumed with constructing a mental model of how the van's electrical components were interconnected. IMO it is a complicated overall system, not intuitively straight-forward and Sportsmobile-West didn't supply me with an electrical schematic, or even block diagram. Of course, there were manuals for all the major components, but no description of how they interconnected and interacted with each other -- all I could see were lots of trees, but little clue as to how the trees were organized into a forest. I initially attempted to document the design by tracing the van's wiring. But it is so dense and hard to access that I quickly gave up and figured that it would quickly reveal itself through usage. But it took most of the year to arrive at what I think is a complete & accurate model. Periodically I would be surprised by some electrical behavior, resulting in my having to refine my model. The result was that I didn't fully understand, and therefore trust, the electrical systems until recently. Nor was I confident that I was using them optimally. In any case, here's a block diagram documenting my system:

Oh, if only something like the above had been available to me earlier! Then I wouldn't have had to discover on my own such things as: the Master Battery Switch doesn't disconnect the battery from the alternator; the solar controller (given sun) will energize the van's 12V circuits and inverter/charger even with Master Battery Switch OFF; the Kenwood AV system's audio amplifier is only powered if the Master Battery Switch is ON (i.e., otherwise no audio, even when just driving), and so on...

In the end, I have gained confidence in Sportsmobile's electrical design and now understand the good reasons for electrical behavior that seems quirky on the surface. But I also came to the conclusion that they had little experience with Lithium batteries. That was clear soon after delivery when I discovered that the installed battery monitor was worthless for Lithium. And as I gradually dug more deeply into each component, I discovered that they all were configured for Lithium with simplistic factory defaults; no parameters were tuned for my particular battery or other component interactions. But everything did work pretty well and I learned to tune settings at my leisure. The various component settings that I ended up with are fully documented in the Starr's Guide's Appendix.

It wasn't until the past month (thanks, covid-19) that I finally dug into the last known sub-optimal electrical behavior -- slow-ish charging of the Lithium battery by the aux alternator. I wanted to minimize the length of time I need to run Starr's engine at high-idle-speed to charge the aux battery when camping. But the 280A alternator+regulator was only providing a maximum 45A charging current. I played with the regulator's programming and for some unknown reason couldn't increase the charging current. I finally determined that the ~25' cable from the alternator to the battery was slightly undersized, resulting in a significant voltage difference between the alternator and the battery cable ends during high current (1.4V difference at 90A, 0.7V at 45A). Since the alternator was measuring the battery's voltage at its end of the charging cable, it saw a false high battery voltage and wouldn't stay in Bulk/CC charging mode. It instead settled on 45A as the max that it should feed the battery. So, I ran a separate battery voltage sense wire from the regulator to the battery so that the correct battery voltage was always measured. As a result, I finally saw correct CC/CV charging behavior. But then I had the reverse problem -- I couldn't get the regulator to throttle the 280A-rated alternator's Bulk/CC charging current below 165A; i.e., down to the Relion battery's specified 100A maximum.I then worked with Nations Alternator and, with some custom modifications to my alternator (kudos to Adam at Nations!), we got the alternator's base current rating down to ~200A and the regulator was then able to further reduce the Bulk/CC charging current to 95-125A (depending on engine rpm & alternator temp). Even though it usually exceeds Relion's 100A max, I have no concerns about charging the battery at this high current. This is because I learned from Relion that the battery's BMS will only shut the battery down due to over temperature, not over current (over current can cause over temp). My alternator's Balmar regulator is monitoring the battery's temperature and has been programmed to shut down charging at a conservatively lower temperature than the battery's BMS temp limit. Note that it is critically important that all this is correctly configured -- a sudden battery shutdown will usually destroy a charging alternator.

During this process I learned that Nations apparently has a 12V 160A alternator which would have been a much better fit for Starr's Relion battery's 100A max current spec (this alternator is apparently spec'd for the Winnebago Revel Sprinter van). Thankfully I didn't have to totally replace my alternator and I'm now a happy camper with my much faster alternator charging.

I also recently installed an aux alternator disable switch for two reasons:
  • To prevent the charging of the Aux Battery when the van must be driven while the battery is frozen. (Since a charging/energized alternator always requires a battery load, you cannot simply disconnect an alternator from a frozen battery. You can only remove voltage from the alternator's field circuit and thereby completely disable it.)
  • To more easily drop the battery's SOC into the preferred 40-60% range before long-term van storage. For example, you can simply disable the alternator during a trip's drive home, just before the van's long-term storage.
Lastly, I've been pretty satisfied with my 230 watts of roof solar and 300 amp-hours (Ah) of Lithium battery storage. The van’s 300AH Auxiliary Battery is effectively 240Ah since discharging below 20% SOC is somewhat detrimental to long term battery health. So, given that I typically consume about 90 Ah of power a day, the van can usually be used for almost 3 days without any charging of the battery. And that time is obviously extended by any solar charging that occurs. The amount of possible solar charging varies widely depending on time of year, cloud coverage, and latitude. I calculated what the panels should produce for Bend Oregon's latitude & average weather, and those numbers are in line with my memory of this past year's van experiences:

Clearly, off-the-grid stays longer than 3-4 days are not possible during the winter without alternator charging. To help (at any time of the year), I am planning to purchase a small, foldable, external solar panel (e.g., an easily-storable Acopower LTK 120 watt panel) – a steeply inclined 120-watt portable panel will contribute the same Ah as the roof’s 230-watt flat panels during the winter!

Some additional, sundry comments regarding electrical usage:
  • I saved about 33% (10Ah/day) of fridge consumption with additional insulation (described in an earlier post).
  • I've never used the charger function of my Magnum inverter/charger except to test and tune its configuration; I just don't camp with hookups (but I use its inverter function heavily).
So, in summary, I have four general recommendations:

  1. Install a Lithium battery -- the 50% weight savings, 30% more discharge capacity, 5 times longer life, and sometimes a faster charging rate IMO easily offset the larger (but lowering) cost differential to other battery types.
  2. Check your battery's maximum spec'd charging current and ensure that your alternator+regulator are matched (e.g., install a Nations 160A alternator rather than the 280A model).
  3. Install a Lithium Battery Monitor (e.g., Relion's) so you can see your instantaneous electrical charging/consumption current & an accurate battery State of Charge (SOC); otherwise you will be flying blind and it will be extremely difficult to tune the setup and manage your use of the electrical system;
  4. Don't go with a charger's default Lithium parameters; rather carefully tune the charging profile parameters for the alternator's regulator, the inverter/charger; and the solar controller to match your battery's specs for recommended charging voltages, recommended/max currents, and temp limits.
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Old 04-30-2020, 07:18 PM   #58
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Impressive, both what is written here and what is in your Guide.
My hat is off to you!
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Old 04-30-2020, 09:18 PM   #59
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Nicely done rick. Great information. I too feel the same way you did in regards to not fully trusting my battery’s/system. You really have to get in there and touch everything to understand it or begin to at least in my case. Great contribution.
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Old 05-01-2020, 09:01 AM   #60
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Quote:
Originally Posted by rsamco View Post
I was concerned about how easily the exhaust air would be pushed down thru the plenum to the lower vent opening.
Due to natural convection (hot air's propensity to rise), if there was a way to reverse the flow, there may be some additional benefits available. In my case, I too added insulation all around and then added a second fan placed low that brings in outside air and pushes it up. I used a 12v computer fan and it moves plenty of air. The second fan is wired through a relay triggered by the original fan, and it has a switch so it can be turned off independently of the stock fan. I did that because I thought it might be a bit noisy, so I wanted to be able to turn it off at night, but it turned out it's not bad and I leave it on all the time anyway. My layout has a vent at the top of the cabinet, and when the fan is running, there is a noticeable increase in warm air coming out as opposed to when the second fan is off. My gut feeling is that the compressor runs less, but that's just a guess.
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