AGM Battery & Diesel Heater Under Passenger Seat

[brownvan]

Thought I would start a thread on this project since others may benefit. Below are some photos of the current setup in the passenger seat pedestal where I have installed a Webasto Airtop 2000 ST diesel heater and a Group 31 135 Ah AGM battery along with a remote battery switch (Blue Sea RBS), 200A circuit breaker, shunt resistor and repositioned the OEM Bosch module that was mounted in there. This project has been done over the past 3 years and has worked pretty well overall. I chose to pack all my electrical stuff into the seat pedestals because there was adequate space and I was avoiding building out an electrical box in the main space of the van. I also was planning on doing a low voltage system first and changing it over time as the project evolved.

This project was done in roughly 4 phases:

• Diesel Heater
• House AGM Battery
• Solar Panels
• Inverter/RBS/CB

 

[brownvan]

Phase 1: Webasto Diesel Heater

This was the first component I put in the pedestal 3 years ago and I originally powered it off the Starter Battery for a few months until I got to Phase 2. I chose to install the heater as close to the passenger door as possible so that I would have adequate space for installing the battery. The heater sits flush to the floor. It works great and has done close to 1000 hours of service with no problems. The controller is mounted on the wall above the driver’s left shoulder. I won’t go into the details of the install unless there are specific questions but here are some photos for reference.

 

[brownvan]

More Phase 1 pics:

 

[brownvan]

Phase 2: House AGM Battery

I chose the Group 31 size because it was about the biggest size-wise that I could fit under the seat with the largest capacity I could find (135 Ah). The battery is strapped to a battery tray which is screwed to a piece of ¾” plywood that is bolted to the floor. I added an aluminum heat shield to the side of the tray to keep radiant heat off the side of the battery from the heater. The Bosch unit was relocated out of the way toward the front panel of the pedestal and the shunt resistor was mounted to the plywood. Main positive leg was #4 AWG with a 40A maxi fuse. Was used as 12 VDC-only system running the fridge, heater, and assorted USB charging duties.

The DC-DC charge controller (Kisae DMT1230), DC fuse panel, and disconnects were installed in the driver seat pedestal. SOC Monitor is a Blue Sea 1830.

 

[brownvan]

More Phase 2 pics:

 

[brownvan]

Phase 3: Solar Panels

After charging off the alternator for a year+ I finally got around to adding solar panels on the roof. I used 2X Grape Solar 180W panels, in parallel, ran them from the roof down to the driver’s seat pedestal with #10 AWG and added a 30A CB. The solar was a great upgrade; really allowed a sustained float voltage to top off the batteries that you would have to drive hours to achieve.



Phase 4: AC Inverter / Remote Battery Switch / 200A circuit breaker

Finally had the need for occasional 120 VAC and came back and re-did the passenger seat pedestal adding an aluminum panel to hold the Bosch unit as well as the Blue Sea RBS and 200 A CB. This was wired with #2AWG and then brought over to power posts in the driver seat pedestal. Inverter was Victron Phoenix 12/1200 pure sine wave. I also finally added a disconnect relay between the Kisae and starter battery so that it would disconnect when the vehicle is not running (I also added a toggle switch so I could disable charging off the alternator easily)

Phase 5?

With the addition of the inverter has come the ability to drain my battery to 50% SOC in about 45 minutes. I don’t have an imminent need for AC appliances but we are trying out an induction cooktop which is pretty cool but may not be feasible in winter time with limited solar hours. I will likely continue with the 135 Ah AGM for a few more years and replace it with a lithium battery. In the meantime, I am at a point where I could share what has been done thus far in case other’s were considering this approach.

Anyways – thought I would put this writeup together so that others could check it out. I wanted to take a stepwise approach to building out the electrical system, initially with a focus on DC-only for the first 3 years before finally adding an inverter. Apologies but I don’t have an updated electrical schematic because my Visio license expired a year ago. I will update this post in the future with photos of the driver’s seat pedestal and the rest of the stuff. I also have a drawing for the wood panel under the battery tray and the aluminum panel for the Bosch unit if anyone is interested.

 

[Deleted member 50714]

Excellent, one of the cleanest heater installs I've seen.

 

[DSchmidt7of7]

Thank you for the excellent photos and very clear description. It gives us "dreamers" a solid example to refer to.

Now if I can just get over the fear of cutting holes...

 

[Kajtek1]

Nice set, even I think that duct loop is cutting down efficiency.
I was considering putting aux batteries under the floor, but that idea sure opens whole new options.

 

[GeorgeRa]

I remember from the Espar D2 manual that total number of bend degree on ducting shouldn't exceed 270 and you have 360. If you have overheating problem you could re-route your ducting in a Z like route to keep it within 180 degree.

 

[Kajtek1]

When I am not HVAC expert, I did few projects and I would simply build a box between heater outlet and make even bigger outlet in pedestal.
Add 1/2 " insulation and you have perfect build.
I bought such heater over 6 months ago and 115F weather so far is not giving me much motivation to install it, but I am thinking about separating front of the cabin from heating since I already have curtain there, so routing ducts , or just let it go?
If I see it right this is 2000W Webasto, as I remember my 5000 unit did not have much clearance when I tried it.

 

[brownvan]

I remember from the Espar D2 manual that total number of bend degree on ducting shouldn't exceed 270 and you have 360. If you have overheating problem you could re-route your ducting in a Z like route to keep it within 180 degree.

Thanks for the suggestion. As mentioned in my post, I have 3 years and approx 1000 hours of runtime with this configuration with no errors or issues. Excess turns in the outlet duct line will accumulate heat buildup and cause friction. Not sure if this a major issue given the short length of the duct line. I did consider busting out the FLIR cam and snapping photos but haven't had a reason to. Also I am an HVAC expert...

 

[GeorgeRa]

Thanks for the suggestion. As mentioned in my post, I have 3 years and approx 1000 hours of runtime with this configuration with no errors or issues. Excess turns in the outlet duct line will accumulate heat buildup and cause friction. Not sure if this a major issue given the short length of the duct line. I did consider busting out the FLIR cam and snapping photos but haven't had a reason to. Also I am an HVAC expert...

I missed your 3 years experience. Good point with short length!

 

[Kajtek1]

Was it 1000 hr of heater operation, or 1000 hr of camping in the van?
If you are real professional, cutting corners and ignoring manufacturer specifications is not going to bring you customers.
I know with small heater the loop might do just fine, but it might not take long when somebody will copy your design for 5k heater and whole hell will break loose.

 

[brownvan]

Was it 1000 hr of heater operation, or 1000 hr of camping in the van?
If you are real professional, cutting corners and ignoring manufacturer specifications is not going to bring you customers.
I know with small heater the loop might do just fine, but it might not take long when somebody will copy your design for 5k heater and whole hell will break loose.

1000 hours of heater operation. We do alot of winter travelling in it for months at a time.
I don't do van builds. I'm a professional mechanical engineer with over 20 years experience. I design custom heaters and do HVAC professionally amongst many other things so I'm not fucking around. The Webasto has a fair amount of safety controls and would shut down if the performance limits were exceeded.
IF you have anything else valuable to contribute to this thread I started besides implying I'm cutting corners or ignoring specifications feel free to contribute otherwise please know that I am posting this info on here to help others and show them this is possible and has been tested. Still worried about that extra 90 degree bend? Then do a jog-bend as George suggested. Thanks

 

[borabora]

Have you ever measured the temperature in the pedestal when the heater has been going for a while? Obviously what you have works but I wonder if it would also be safe for LIFEPO4 batteries that are more heat sensitive.

 

[brownvan]

Have you ever measured the temperature in the pedestal when the heater has been going for a while? Obviously what you have works but I wonder if it would also be safe for LIFEPO4 batteries that are more heat sensitive.

Good question. I just went and did a preventative maintenance cycle on the heater since the controller will alert you to run it if you haven't used it in 30 days. I ran the heater for 20 min with a set temp of 90 deg F. Vented the interior with windows cracked and sunroof open so it wouldn't hit the set temp. Pretty much full blast. Also the seat & swivel were mounted on the pedestal as normal and I do not have the access panel installed on the side.
Surface temp of the Webasto heater before running was 83 deg F. It's about 72 degrees outside today.
After 20 min full blast, the surface of the duct was 135 F, the Webasto top was 120 F, the heat shield 110 F and the battery top 90 F
Temps were taken with an IR thermometer 1/4" off the surfaces. I could imagine these temps would be higher on a hot day when the interior of the van can get to 120 deg F. Curious what the safe operating/charging temp range for LIFEPO4 batteries? Thanks

 

[erik.wahlstrom]

Phase 2: House AGM Battery

I chose the Group 31 size because it was about the biggest size-wise that I could fit under the seat with the largest capacity I could find (135 Ah). The battery is strapped to a battery tray which is screwed to a piece of ¾” plywood that is bolted to the floor. I added an aluminum heat shield to the side of the tray to keep radiant heat off the side of the battery from the heater. The Bosch unit was relocated out of the way toward the front panel of the pedestal and the shunt resistor was mounted to the plywood. Main positive leg was #4 AWG with a 40A maxi fuse. Was used as 12 VDC-only system running the fridge, heater, and assorted USB charging duties.

The DC-DC charge controller (Kisae DMT1230), DC fuse panel, and disconnects were installed in the driver seat pedestal. SOC Monitor is a Blue Sea 1830.

Wow. This is exactly what I'm looking for. I have a stock battery which includes 4 weld nuts from the factory. Unfortunately they are offset in a way that puts the battery in the middle of the seat. I'm going to build a similar bracket to what you've built but offset it such that I can use the original bolt holes. Thanks!

 

[brownvan]

Wow. This is exactly what I'm looking for. I have a stock battery which includes 4 weld nuts from the factory. Unfortunately they are offset in a way that puts the battery in the middle of the seat. I'm going to build a similar bracket to what you've built but offset it such that I can use the original bolt holes. Thanks!

Cool, upload some pics & notes of before/after when you have a solution for shifting the stock spare battery mounting. I think this would be helpful for members who have the OEM spare battery and want to shift it for adding a diesel heater under the passenger spare seat.

 

[erik.wahlstrom]

Will do. Question, how did you run power to the Webasto? Do you go to a fuse box before distributing it to the heater? I have a fuse box in the driver seat and then through the b pillar, ceiling and down the passenger b pillar to the seat base. Unfortunately . . . . That wire appears to be dead. So now I have to figure out power again. A post mounted fuse running to the heater seems the easiest, but kinda ugly