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HOW TO: Lithium Battery Powered Vent System


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Lithium batteries are happiest when they are not subject to extreme temperatures. The Oliver battery box has vent holes in the door, but the actual "container" itself is sealed tight, and the area above and around it is a dead end air space; there is no way to get the heat out in summer, or to get warm cabin air in during winter. I wanted to get good airflow through this space, with natural (convective heat flow) and forced (computer fan) movement. Another benefit is that the air flows from the open cabin space and through the two electronics compartments, cooling the hot accessories that are installed there. Like the battery box, those spaces have no natural airflow - they get hot in summer and cold in winter. This will help to moderate those temperature swings. Here is how I did it on Hull 218.

FYI, to the best of my knowledge the factory lithium package does not include any kind of venting to the cabin interior, though an electric heating pad is included. Please comment if this is incorrect!

John Davies

Spokane WA

Edited by John E Davies

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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Battery box exhaust vents.

Qty 3 - Perko 51840 Chrome plated brass (same part used on the battery door factory vents) ... https://www.go2marine.com/perko-ventilator-vent

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Make a template - there are  a lot of holes to drill:

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The 4 mounting holes can be sized for 1/8" rivets (not recommended) or number 6 sheet metal screws. Choose the correct size for your fasteners! I chose screws.

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The front and back vents go here:

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You will be staring at these for a long time, so be very sure the holes are perfectly straight, measure thrice, cut once. Don't use a bubble level, measure up to the joining line.

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Here is the reason you can't position it higher:

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Deburr the holes CAREFULLY with 80 grit sandpaper (wear gloves or you will drive glass shards into your fingers), do not scratch the surrounding gelcoat!!!! Install the Perko cover. Repeat these steps for the rear wall. The optional factory granite countertop keeps the seat cushion slightly away from the wall in this position. If yours does not have the optional ones, the front vent will be blocked with the cushion as shown here..

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Here is a view inside the compartment, looking back at the INSIDE of the rear vent. Notice you cannot position it higher or the screws will not clear the top:

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The third vent goes in the center of the inside wall, directly below the pantry shelf. Having three vents means that one blocked vent (a pillow for example) will not significantly affect the airflow.

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Finally, there need to be holes in the TOP of the battery box, to let air out from that space. Since I mounted a fan in the bottom, at the very back, I chose to place them in front, so air would move below and across the batteries, leaving no "still air" pockets. All other openings in the box should be sealed with heavy aluminum tape or a similar product.

There is plenty of space on top of the box for air movement:

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John Davies

Spokane WA

  • Like 2

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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Posted (edited)

Battery box intake vents.

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Originally I wanted aluminum louvered vents, so I could paint them white to blend in, but the ones I bought turned out to be way too flimsy. They would have been destroyed by a wayward kick. I ended up with these and am fairly satisfied. They are sturdy and very pretty. Unfortunately they need trimming and the addition of two more mounting holes, so they would pull down tight and flat. Drilling stainless is possible, a drill press makes it less frustrating. It requires a lot of pressure on the bit.

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Use a 4" hole saw or a jigsaw to cut the holes in the fiberglass. I placed one under the rear bed and one under the rear dinette seat, centered front to back and up/ down. The center is approximately 9 " off the floor.

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Even though sanded smooth, the edge was pretty dangerous, so I used 1/4" split loom to protect fingers. I added a blob of silicone on each protruding screw tip.

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In the future I plan to add third vent at the bottom of the closet door opening.

John Davies

Spokane WA

 

Edited by John E Davies
  • Like 2

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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Posted (edited)

Battery box cooling fan. This one is high quality and well regarded. It has sealed ball bearings and uses just 70 milliamps (0.07 amps), so it can run as long as needed. Flow rate is 38 cfm on high, they supply two dropping resistor harnesses if you want to slow it down to reduce the sound level. It is pretty quiet, though a light sleeper on that side of the trailer might want to turn it off at night. But it is “white noise” which sometimes you do want.....

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Noctua Fan

I really wanted the fan to go in the bottom at the rear wall, so it was centered between the two electronics compartments. The problem is that the floor of the box is not fiberglass honeycomb as I thought, rather it has a hard (6061?) 1/8" aluminum diamond plate bonded in the center! So cutting a large opening was a challenge. If you have access to a scroll saw (pivoting head) it is easy enough. Otherwise, choose to locate the fan at the bottom edge of the rear wall instead! That is thin (1/'8") fiberglass.

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Screws are 5mm, and are double nutted so that the heads will stick up enough to use as "grab handles", for servicing:

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John Davies

Spokane WA

Edited by John E Davies
  • Like 2

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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Posted (edited)

 

Battery fan wiring and switch.

I used the supplied adapter cable and simply cut its 3 pin connector off and butt spliced the wires to a new 18 AWG red/ black wire pair. I secured the connector at the bottom of the battery compartment wall, forward of the inverter:

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Power comes via a 1 amp inline fuse connected to the rear DC bus. I mounted a switch next to my Victron BMV-712 Smart battery monitor display, below the pantry counter top. An additional ground wire is needed if the switch has an LED (this one is blue, to match the Victron backlighting):

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Finally, an instruction placard for a future owner or an RV service tech. This is laminated and taped on the rear wall of the battery compartment, and a copy is in the Owners Manual:

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John Davies

Spokane WA

Edited by John E Davies
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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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Posted (edited)

Battery door - plug holes and add insulation. This did not work out well, I am not very satisfied with the results, but I will post pics anyway. Maybe somebody can suggest a better solution. 1/2" foam board would be much easier to fit, but the insulation value is not so good.

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The material is Dow Corning rigid foam board, 1 inch thick, which weighs essentially zero pounds. This stuff is incredibly light. $20 for a 4' x 8 ' sheet at Home Depot. It is fire retardant, which is important. For comparison, this is R-5 (insulating value) whereas a typical foil/ air bubble sheet, which is used extensively in an Ollie, is R-1. 

https://www.homedepot.com/p/Owens-Corning-FOAMULAR-150-1-in-x-4-ft-x-8-ft-R-5-Scored-Square-Edge-Rigid-Foam-Board-Insulation-Sheathing-20WE/207179253

It can be cut easily with a VERY sharp razor knife, and rough edges can be rapidly sanded smooth and contoured with a bench top belt sander and coarse 80 gr belt. WEAR A MASK.  BTW it is indeed completely waterproof, I soaked a piece for 12 hours to make sure. I had to wedge it in place, it pops out like a cork otherwise:

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Cut four hole plugs to seal off the existing openings. (My door has 8 holes, yours may vary.)

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Cut them in half:

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Glue them into the holes with clear RTV sealant, some will squirt out through the front Perko vents. Remove that excess with alcohol and paper towels:

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Wait at least a full day and then trim off the excess foam and sealant flush with a razor blade:

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SUPPORT the door with something, a 30 inch high rolling work table fit perfectly, and it gave me a nice place to put tools and materials... Remove the support cable. Cut the foam. This is pure trial and error, because it has to fit past the rubber seals, and also have extra material removed to clear the battery tray and knob, and the support cable, and the lumps and bumps on the door itself. Take your time, trim a little, test the fit, trim some more. It should fit as closely as possible, for maximum insulation value, yet allow the door to close easily without stressing it.

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I used a router bit in a drill press to carefully carve out areas that needed clearance. Be sure to allow some room for rivet tails! When you are satisfied with the fit, clean and smooth the parts and use 3 M VHB tape to secure it to the door. I used 1/4" wide tape placed vertically, so any water leaking past the rubber seal will drain straight down.

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Add some weight and go take a long break:

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Remove any weights or clamps. Seal the edges with clear RTV sealant. Use tape as shown to leave clean lines. Reattach the support cable. BTW when trimmed as shown in the top pic, the airflow from the fan underneath the tray is not blocked.

EDIT: Leave several small gaps in the sealant at the inside (bottom edge when closed) so moisture can drain out.

John Davies

Spokane WA

Edited by John E Davies
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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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Wow - amazing engineering and work as usual!  I have a feeling many of us will be trying something similar once Summer rolls around.  This is obviously not an easy mod to pull off.  This will help tremendously even if the design varies a bit due to differences in the Ollies.  What don't you like about your insulation on the door?  I would have to say it's way more insulated than the rest of the Ollie, so I think it may not be a problem.  Thanks!

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2020 Elite II, Hull 688 --- 2021 Silverado 2500HD, 6.6L Duramax Diesel

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John, thanks for the kind words, the pink stuff just looks dorky and crude, I suppose it could be covered completely in heavy aluminum tape. but it would be tricky and time consuming to completely cover all the openings and cutouts. Plus it is soft, and susceptible to dents. I don’t know of an affordable material that would function better. Of course, I will probably be the only person to see it, and the next owner can take it out if it is too pink.... It should work very well at blocking heat transfer from direct sunlight. It will be interesting to see what kind of temps are shown on my monitor, and what effect the fan will have when turned on in inclement weather.

John Davies

Spokane WA

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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Very nice work!  Might you be doing some hi-lo temperature measurements on hot or cold days -- I'm curious about the temperature difference this will make.

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2021 Oliver LE2
Ram 2500 diesel

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John, excellent mod. You continue to show how quality work needs to be done. Unfortunately i dont have the skills nor the equipment to do the work but your detailed photos can allow a qualified individual  to do the work

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The temperature data I've been collecting strongly suggest that I need to figure something out with the battery box like you did.  My target is to keep the box in a sweet spot of 60F - 80F if possible.  Given this limited range, I'm convinced that leaving the battery box door sealed and insulated is mandatory.  These Lithiums are just like humans when it comes to temperature I guess!  🙂 

Here's my preliminary design:

Conditioned air intake:  A 4" duct vent under the street side bed and another 4" duct vent in the battery box right above the street side wheel well.  There's plenty of room for 3.75" holes in both places to install the ducts.  Between the vents I'm planning on using a 4" duct paired with an inline smart fan (yes, I like smart fans!) to pull conditioned air from the cabin and push it into the battery box.  The smart fan will fit nicely right on top of the wheel well and can run anywhere from 28 cfm to 280 cfm.  It also has a thermostat to provide some automation.

Battery box exhaust:  I am not planning on exhausting the battery box directly back into the cabin.  I have another 6" smart fan under my forward dinette seat to move air slowly or rapidly between the entire basement and the cabin if necessary.  Additionally, if I leave the fan pushing conditioned air into the box running long enough it will be pushing conditioned air into that basement area and surrounding electronics.  I'm also thinking of using a bunch of smaller holes in the battery box to exhaust the air rather than just one or two bigger holes.  For example, a 3.75" diameter input is ~11 square inches of area, so if I use 1.5" diameter holes (1.75 sq. in. area), I would need ~6 holes to provide adequate exhaust area.  So I was thinking of drilling the 6 smaller holes in somewhat random places on the front and back sides of the battery box, hoping that would give some good cool air mixing in there.

I'm wide open to suggestions, constructive criticism, or any other things to consider that I missed.  Especially @John E Davies since you have already thought through and executed on your design.

Thanks!

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2020 Elite II, Hull 688 --- 2021 Silverado 2500HD, 6.6L Duramax Diesel

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Nice work John. How is the rest of you conversion going?

I thought I read on one of the new Li manufacturers sites that the temp window has expanded - hi and low.

In the end - is the conversion worth the trouble - I wonder. 

RB

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Cindy,  Russell and  "Harley dog" . Home is our little farm near Winchester TN

2018 Oliver Legacy Elite II - 2018 GMC 2500 Duramax 

"Die young - As late as possible"
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NCeagle, I think your design would work fine, though I would personally be really really reluctant to rely solely on a powered fan. I think it is important to have at least a little natural convective flow - warm air rises out the top, cooler air flows in down low. The space above the battery box is pretty much a dead end cave, while there may be a trickle of air going up between the hull walls, there is no place for escape for it up high, unless you drilled vents in the overhead cabinets.

So you need those openings into the cabin where the pantry box joins the battery box. You don’t necessarily need forced air.

John Davies

Spokane WA

 

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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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3 hours ago, BackofBeyond said:

Nice work John. How is the rest of you conversion going?

I thought I read on one of the new Li manufacturers sites that the temp window has expanded - hi and low.

In the end - is the conversion worth the trouble - I wonder. 

RB

RB, I am done, pretty much. I have been delaying posting some more threads because I do not want to look too eager 😬, plus it is very time consuming. If there is a particular subject you would like to see, let me know. I subdivided them - battery installation and straps, cable installation, Victron solar controller installation, etc. They are too complicated to do in one thread. 

John Davies

Spokane WA

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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2 hours ago, John E Davies said:

NCeagle, I think your design would work fine, though I would personally be really really reluctant to rely solely on a powered fan. I think it is important to have at least a little natural convective flow - warm air rises out the top, cooler air flows in down low. The space above the battery box is pretty much a dead end cave, while there may be a trickle of air going up between the hull walls, there is no place for escape for it up high, unless you drilled vents in the overhead cabinets.

So you need those openings into the cabin where the pantry box joins the battery box. You don’t necessarily need forced air.

John Davies

Spokane WA

 

Thanks John.  I was thinking about a few more crazy options today.  One thing I've got in the back of my mind is that a loss of the fan and having the battery box heat up isn't a show stopper like not having backup heat would be (and having pipes freeze / break).  So, I still have a few months (at least) to think about it before we start seriously warming up here.  I'm not planning on super hot camping, but all I have is a big steel shed for the Ollie and it could get blistering hot in there over the summer.  My batteries are always on to run lights, toilet fan, etc.  If you get any data from your design, please let us know - like if you get the bug to head straight south soon.  🙂  Thanks again for reviewing my design and sharing your thoughts.  Very helpful.

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2020 Elite II, Hull 688 --- 2021 Silverado 2500HD, 6.6L Duramax Diesel

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6 hours ago, BackofBeyond said:

In the end - is the conversion worth the trouble - I wonder. 

That's the big question that we can't answer right now - Lithiums are too new.  So the way I'm looking at it is this...  had OTT offered me an option to have an "air conditioned" battery box for $150 or so, would I have done it?  Heck yes - considering I'm spending so much on these Lithiums.  So like you RB, I wonder too whether it's worth it - but I have this vision of Dirty Harry looking at me and saying "Do you feel lucky, punk".  😃  At some point, the cost does not outweigh the potential benefit of course.  

My guess is that as Lithiums become status quo in travel trailers / RVs they will be located in air conditioned spaces as opposed to vented outdoor boxes used today.

Edited by NCeagle
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2020 Elite II, Hull 688 --- 2021 Silverado 2500HD, 6.6L Duramax Diesel

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3 hours ago, NCeagle said:

guess is that as Lithiums become status quo in travel trailers / RVs they will be located in air conditioned spaces as opposed to vented outdoor boxes used today

I think so, too. 

I'm trying to figure out what I'd have to give up,  in limited indoor space, to accommodate anything else beyond what we already have crammed in.

Or, seal the battery compartment,  and open it up to indoor space. 

2008 Ram 1500 4 × 4

2008 Oliver Elite, Hull #12
 

 

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