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Old 11-23-2017, 05:22 PM   #41
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Originally Posted by Iceni John View Post
Like this?
Bus Nut Online - Articles Of Interest - Super Insulating the Roof - by George Myers

I have a noticeable reduction in ceiling temperature under where I have my panels compared to the rest of the roof. Simply preventing the sunlight from reaching the roof is well worth it, even with the crappy stock insulation in there.

John
I haven't seen that before but yes, a bit like that.

I would take issue with one thing he said. Foam board has excellent compressive strength. It is used to insulate floors, and they pour concrete on it. It would, covered with aluminum or fiberglass, be more than strong enough to carry an AC or three. It already does in many trailers which are made of a sandwich of aluminum, foam and thin plywood.

The thing I would have to check would be the cost of a 40' x 10' glassfiber lay-up.

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Old 11-23-2017, 09:25 PM   #42
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Hi Steve, same plan here. I will take aluminum foil faced insulation. designed and made my solar from on Elfie and Dory so that I can slide a 3/4 to 1 " board in between. That thickness conform easily to the curvature of the center of the roof.

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Old 11-24-2017, 04:47 AM   #43
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i fulltimed in iowa a couple of years and any cooking or showers caused ice buildup on the inside even on wood walls that had gaps in insulation. even in the morning in the bedroom it was frosted from my breath. a dehumidifier was the only thing that worked. also ran to az last weekend and it got down to 9 degrees Fahrenheit overnite up there
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Old 11-24-2017, 11:27 AM   #44
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Thanks for this conversation! Very educational. Particularly, that article referenced went a long way towards convincing me of the importance of a thermal break on a rib joint.
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Old 11-28-2017, 08:18 PM   #45
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Picked up the panels today, one less things to worry about

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Old 12-17-2017, 09:45 AM   #46
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Interesting video about the Tesla truck.
https://youtu.be/oJ8Cf0vWmxE

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Old 12-17-2017, 09:46 AM   #47
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Old 12-17-2017, 04:12 PM   #48
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There are a lot of people waiting for Musk to fail. But this truck has real potential, whether Tesla make a profit from it, or another company does.
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Old 12-17-2017, 05:34 PM   #49
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That makes a strong argument for more hauling by train, using the trucks for local delivery.
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Old 01-15-2018, 11:01 PM   #50
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So here's the latest progress.



And here's my first cut at the 1 wire diagram, beginning to incorporate all the various fuses, breakers, etc.



Tech support from Morningstar has been very helpful. Tech support from Schneider thinks I'm insane ;) They're supposed to be hooking me up with their applications support team this week so we'll how how that goes. Basically they are kind of hung up on the fact that I'm pushing my nominal battery voltage higher to improve efficiency within the bounds of what their documentation says their equipment will do. Mostly it seems like they don't have much experience with Lithium batteries, which don't need the kind of over charging that lead acid do. Since I don't need to charge at 56-64V to charge a 48V nominal pack like lead can, it makes sense to me to increase the voltage of the battery rather than turning the charge voltage way down. Particularly as that should maximize efficiency and power output of the charge controller.

Hard to say if it's a good idea or not, but for now I'm proceeding with 8 modules in series. That will result in a max voltage of 65.6V at 4.1V per cell, which is about as high as I will probably want to go. The Schneider charger will only go up to 64V, but that's ok as I generally won't be wanting to charge to 100% off grid power anyway. The inverter says it will tolerate at least 68V input voltage from the battery, so that should be fine. The Morningstar controller can go up to 67V as I recall, which is good because generally if the battery is going to be charged to 100% I want it to be coming from the solar.

Ironically the only actual problem I've found is on the low end. The highest value the Schneider low battery cutoff voltage can be set to is apparently 48V. That's 3.0V per cell, which is definitely on the low side. I'd be happier cutting of the inverter at about 3.5V. 3.0V shouldn't be fatal, but it's more stressful than usually desired. So that basically means it will be up to the BMS to shut the inverter down to protect the battery. Which is sort of it's job, but usually you'd like to have some redundancies in place.

Which lead me to start looking at how to interface the BMS, charge controller and inverter/charger together from a networking perspective. Which is basically a nightmare. There may be a solution, but it's going to be challenging. They all talk different protocols, and use their own proprietary commands, so it's going to be a job getting them all to play nice together. To start of I will probably use relay based control from the BMS to manually enable/disable charging and discharging, though the Schneider doesn't even officially have a means of doing that. Still there is usually a way of hooking things up to induce a fault that will suspend the inverter/charger, even if it's not officially supported. Morningstar does have a such a feature documented, which uses a relay to disconnect the temperature sensor, which causes a fault that halts charging until restored.

Here's my current best guess at what it will take to get these all talking to each other eventually.



I've been looking at the Batrium BMS, which looks pretty cool. Seems like a good price for the feature set, and they have a cell monitor/balancer specially made to go with the Leaf modules. The documentation leaves a bit to be desired, but they seem to have a good following in the DIY crowd so there is a fair amount of external support.

I'm thinking of sticking with the same basic set of 2 x 24 module sub-packs that I was planning to use in the car since I already have the hardware. Here's what they would have looked like in there.



And here's my basic bus bar plan. One nice thing is the Leaf modules come in two polarities so they could alternate and keep the bus bars short in the stock pack. Re-arranging those I can use the same idea to pretty simply get the parallel / series wiring I'm looking for pretty easily. Went and picked up some 1/8" x 1" flat copper bar from the local metal supply house, so I'll be ready to start cutting and drilling the bus bars once I get the garage cleaned up enough to get to the drill press ;)

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Old 01-15-2018, 11:33 PM   #51
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I feel smarter just for having read that.

Good luck with your endeavor.
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Old 01-15-2018, 11:36 PM   #52
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Solar Hybrid Electric Skoolie Adventure Begins!

Lol. I feel like I’m losing my mind trying to make sure all this stuff will work together before I start buying stuff. But have pretty much determined I’m just going to have to start getting the equipment in and figure out how to make it work.


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Old 01-26-2018, 01:40 PM   #53
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Parts have started arriving!




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Old 01-26-2018, 01:53 PM   #54
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Fabulous ! Can not wait to see your build. Hopefully you will have it done by Spring Training.

A little wire chafing on your bus would be a whole different story, I imagine.

I wonder if you couldn't get one of the schools or Sun Devils to help. We had a heck of a solar club for SAE when I was a Wildcat. Maybe even sponsor???

Will be following you ( as you silently glide down the highway).
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Old 01-29-2018, 03:28 PM   #55
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The biggest potential spoiler of my plans is if the Leaf batteries have deteriorated significantly from their year plus in storage. So now that the inverter / charger is in it's time to build up the packs and get the batteries charging.

The Leaf modules come in two different polarities. All are still 2s2p cells, but half have the positive / negative in one orientation and the other half are the opposite. In the stock pack this makes it easy to connect all 24 modules in the half pack in series by alternating polarity and just connecting the + of one cell to the - of the next with a short bus bar. By reordering the modules so there are 6 of one polarity then 6 of the other I can take advantage of the same idea to create the 6p / 4s arrangement with only bus bars.



Although they are a lot lighter than lead acid, a 12kWh half pack still ends up weighing about 200 pounds. I've found the easiest way to create the stack is to work vertically, so the weight of each additional module helps compress the stack and keep things in line.



Here's the first pack done. Once all the modules / spacers are on and the bolts tightened down the structure is very rigid. The open center tap contacts will be used by the BMS to monitor and balance the cells just as in the Leaf.



And here's both packs done. I reversed the order of the module polarity on the second pack so I only need a short +/- jumper on one end, and have the pack + / - connections on the other end.



And here's the latest plan on the location within the bus. Our floorpan has a dinette made from bus benches on both sides in the front, these are the space between that and the drivers seat / front stairwell. Another solution would have been to put the batteries underneath, but it simplifies things to keep the batteries at the same temperature as the people. Both sides will get boxed in with a temperature controlled exhaust fan in the top.



And here are the results of the cell voltage measurements before and after the bus bars are attached. All of the cells were still within about 20mV of one another after a years worth of self discharge, so that's very encouraging. After being connected in parallel each group of 6 will self balance to some degree, resulting in a final spread of about 10mV across all 96 cells / 48 modules.



Rob
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Old 01-29-2018, 04:46 PM   #56
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Very nice, To what voltage are allowing the cells to charge? Assume lower the 4 Volt per cell? What do you expect the actual AH capacity to be at what lowest cutoff voltage?

Good luck.

Later J
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Old 01-29-2018, 06:11 PM   #57
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I plan to do some bench testing on the whole system in part to set safe voltage limits. 4.1 volts / cell seems to be a pretty common limit when using a BMS. I’ll probably start out at 4.0 V / cell initially. Particularly since the max voltage out of the Schneider is 64v.

I know I’m pushing it a bit by trying to go 8s (16s cells), 7s is more common. But 8s6p is a lot more convenient as there are 48 modules in a Leaf pack. The Morningstar charge controller can put 60A into either a 48v or 60v nominal pack, so another advantage to going 60v nominal is it maximizes the power output of the controller and the 3600w solar array.

That will leave the solar to do the top end of the pack charging, which should generally be fine. I don’t necessarily want the grid charger to fill the pack and not leave room to store available solar power when it’s available anyway. The Schneider is supposed to be able to handle up to 70v from the battery, so hopefully everything will be ok. The big thing will probably be getting the control integration solid to make sure the Inverter and chargers are shutdown before the contactors disconnect the battery in the event of a battery issue. Otherwise that could result in a voltage transient that could exceed the max rating on the Schneider. The Schneider also unfortunately has a max low battery cutoff setting of 48v, which is only 3.0 V / cell. So it will be up to the BMS to shut the Inverter down before the battery is allowed to discharge that low. 3.0V shouldn’t be fatal to the batteries, but would not be good for battery health to do on a regular basis.



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Old 01-30-2018, 12:18 PM   #58
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Finished the temporary wiring for the CellLog on the first pack. With the center taps connected in parallel the cells are now balanced to within <4mV across this pack when measured with my Fluke multimeter! The Batrium BMS is back ordered as they transition to a new version, so I'll be using the CellLogs until then to monitor the status of the packs. For the money ($18 basic, $35 with data logging and USB port) they are a great little product in my experience. They even have a configurable alarm port (selectable NC/NO switch contact) that can be used to shut things down based on hi/low cell or pack limits. I'll be using those to remotely enable / disable a bench power supply connected to the contactor control coils as a basic pack protection for my early bench top system tests.







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Old 01-30-2018, 12:59 PM   #59
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I've always wanted to use a battery pack like you're doing. Very interesting, but I'm not electrically gifted. I'd have electrocuted myself with a battery pack like that by now.
I slowed way down on those battery packs after learning about some of the special considerations of that type of battery as compared to lead acid or AGM. Also the prices of used battery packs went way up at junkyards.

Thank you for documenting this so well. Very informative.
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Old 02-05-2018, 03:11 PM   #60
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Making progress with the bench test setup.



Batteries are now connected to the Inverter / Charger through the stock contactor box. Haven't yet tried wiring up the CellLog alarm ports to control the contactors so I need to stay nearby when the system is operating. Contactors and pre-charge relay are wired up to switches for manual sequencing and control. I'm still waiting on the Schneider DC disconnect box to arrive, but the pack is currently protected by the stock service disconnect / fuse and the contactors.

Wired up the AC side to the AC disconnect box, with a 40A 240V appliance cord so I can plug in to my garage 50A outlet for shore connection and a test outlet on each leg of the split phase output for load testing. Tested with a small 5W LED lamp and then a 1200W heat gun on each phase, no issues.

Most importantly I was finally able to charge the batteries up a bit off the grid charger. The max output of the SW4048 is 64V, which is 4.0V/cell on my 8s6p (16s cells) pack. As hoped it ran at the full 45A output right up to 64V on the external meter. Eventually I may want to go as high as 4.1V/cell, but it will be solar charge controller that will be responsible to for topping up. This should be high enough to let me do some cycle testing to see how the batteries are doing. But I'm very encouraged that the cells all stayed very well balanced through the charge.



The charge controller arrived, so next I plan to start wiring that up on the bench as well.

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