Goin’ Solar! DIY

[lateott]

Really enjoying the thread! Your detailed posts will help many other owners.

So it looks like you screwed/sealed the lower tilt rails directly to the roof, is that correct?

I am using 2 X Renogy tilt racks with 2 X 100W Rich Solar panels. I am planning to bolt the lower tilt rails to standard Z-brackets, which are in turn screwed and sealed to the roof. My reason is I would like to have the ability to remove the panels leaving minimal hardware stuck to the roof. I would use Z brackets directly, but it looks like there is no reasonable way to remove or lift the panels for cleaning/maintenance.

Would you see any problem with my approach after your installation experience? Lower rails to Z brackets to roof? Then I could remove the tilt kit and panels, and leave only the secured and sealed Z brackets. There would by a slightly larger air gap under the panels, but I think that wouldn't be a bad thing.

[campin]

Thnx for commenting lateott! and my tilt kit is secured to the roof.

I’m not familiar with Z Brackets but I read (and learned) good for your application. The 100 watt Renogy weighs 14 lbs, I think brackets will be fine. I have panels weighing 40 lbs. each so I prefer a wider footprint to tilt and reduce flex. My panels have 2-3 inches of airspace when traveling otherwise tilt year round for max power, the degree is subject to season and latitude location. For example in Prescott AZ, optimal winter tilt is 49 degrees, summer 19 degrees.

...and my solar system is permanent on the 184BH (though I can changeout panels and hardware). It’s an upgrade to energy independence.

[sciencenerd]

Originally Posted by lateott

Really enjoying the thread! Your detailed posts will help many other owners.

So it looks like you screwed/sealed the lower tilt rails directly to the roof, is that correct?

I am using 2 X Renogy tilt racks with 2 X 100W Rich Solar panels. I am planning to bolt the lower tilt rails to standard Z-brackets, which are in turn screwed and sealed to the roof. My reason is I would like to have the ability to remove the panels leaving minimal hardware stuck to the roof. I would use Z brackets directly, but it looks like there is no reasonable way to remove or lift the panels for cleaning/maintenance.

Would you see any problem with my approach after your installation experience? Lower rails to Z brackets to roof? Then I could remove the tilt kit and panels, and leave only the secured and sealed Z brackets. There would by a slightly larger air gap under the panels, but I think that wouldn't be a bad thing.

This is how I installed my panel while making it removable. I initially screwed an aluminum flat to the roof. That flat has two through bolts, to which the panel can be bolted using the regular z-mounts.

The 3d picture shows what is left on the roof when the panel is removed.

[lateott]

Originally Posted by sciencenerd

This is how I installed my panel while making it removable. I initially screwed an aluminum flat to the roof. That flat has two through bolts, to which the panel can be bolted using the regular z-mounts.

Very creative approach. Thanks for sharing that, along with the photos!

[lateott]

Originally Posted by campin

Thnx for commenting lateott! and my tilt kit is secured to the roof.

I’m not familiar with Z Brackets but I read (and learned) good for your application. The 100 watt Renogy weighs 14 lbs, I think brackets will be fine. I have panels weighing 40 lbs. each so I prefer a wider footprint to tilt and reduce flex. My panels have 2-3 inches of airspace when traveling otherwise tilt year round for max power, the degree is subject to season and latitude location. For example in Prescott AZ, optimal winter tilt is 49 degrees, summer 19 degrees.

...and my solar system is permanent on the 184BH (though I can changeout panels and hardware). It’s an upgrade to energy independence.

Thanks for the info. There are 3 reasons I have for potentially needing these removable. 1) Repair/replace panels or connections and I would take these with to the next one, 2) I am on seriously considering upgrading my TT this year, 3) Cleaning/maintenance of roof.


BTW, in a previous century I ran the Boot Race on Whiskey Row in Prescott. Great place, I really enjoyed Jerome as well.

[campin]

With the tilt kit I can clean, maintain the roof and remove panels if necessary. ...mind you swinging a 40 lb. panel can be a bit dicey
As for the 184BH, she’s a keeper. Good you do the research, it’ll work out great.

Originally Posted by lateott

BTW, in a previous century I ran the Boot Race on Whiskey Row in Prescott. Great place, I really enjoyed Jerome as well.

...that’s cool! and Jerome is a quaint little town (ride my motorcycle there).

[campin]

My new “solar” cooker. The 3 qt. Instant Pot cooks gourmet meals in minutes (powered by 280AH LifePO4 battery bank). If I use it for 30 min., that’s only 3 amp hours!

[billcf7]

The ultimate solar system

https://www.youtube.com/watch?v=roa2kRjNknw

[campin]

Originally Posted by billcf7

The ultimate solar system

...I would say so, a 2.5 KW system! Can you imagine what’ll be like in a few years?? Thnx for sharing.

Btw the instant pot AH estimate is off, it’s more like 16 (time expired to edit). I didn’t convert ac to dc amperage ...still very little power to cook a nice meal and leftovers.

[campin]

I read a 700 watt microwave (in my Jayco) is typically 40–60% efficient. It’s gotta go, no place in solar world. I’ll replace it with shelves, an ac outlet and new instant pot.

[campin]

Removed microwave (electric hog) and gained 2 cubic feet of space, now shop for a cabinet door.

[campin]

280AH battery cells (8) should arrive in a few weeks. In the meantime gathering bits and pieces to complete the off grid system. And no BMS (battery management system) however there’ll be safeguards to monitor (Bluetooth) the battery bank. I like to have more control over what’s going on....

[lateott]

Originally Posted by campin

...no BMS (battery management system) ...

Risky. From what I have read you can destroy a an individual cell by overcharging it, even when the overall assembled battery is within voltage range as controlled by your charger. You can't really prevent that without a BMS, unless you yourself are monitoring every individual cell during charging. Human BMS.

The problem with that situation is then you need to try to replace (an expensive) cell, which you may be lucky to find if the vendor, brand, and cell type still exist, and even then it is unlikely to match perfectly with your 3 other cells.

FYI, I am currently going through similar process with 2 x 120 AH 12V built from 8 individual cells. I have top-balanced the cells, and I am installing 2 Overkill BMS, which also have bluetooth for monitoring and configuration.

[craigav]

Originally Posted by campin

280AH battery cells (8) should arrive in a few weeks. In the meantime gathering bits and pieces to complete the off grid system. And no BMS (battery management system) however there’ll be safeguards to monitor (Bluetooth) the battery bank. I like to have more control over what’s going on....

You can purchase a BMS, I have seen them on ebay. If you are just using the used larger rectangular cells you will not be happy without a BMS. Most all lifepo4 batteries that are designed for drop in use have the BMS builtin. ~CA

[campin]

Thnx lateott, craigav for contributing! And I’m not down on BMS in general but my solar system is adequately protected. For example I’m installing an active equalizer (balancer) to keep individual cells in check w/Bluetooth monitoring + alarms. And if there’s a rogue cell, a BMS can’t repair it. The good news is LiFePO4 is known to be very stable. ...I’ll monitor no more than if it had a BMS.
btw I read online one should bottom balance without a bms.

[campin]

...LiFe from overseas, I received 2 of 8 cells today. Exciting

[jjason]

Thanks for posting your progress. A few questions:

1. Why did you go with 24V instead of 12V
2. Is the tow vehicle able to charge your batteries? If so, how? If not, how are you keeping the two systems isolated?
3. Do you have a wiring schematic/diagram?

[lateott]

Hey jjason, I know the question is not directed at me, but I am dealing with the same question right now.

It seems the problem is often the other way around. Without isolation, the trailer LiFePO4 batteries are trying to charge the TV battery, and lowering the alternator load, and thereby being drained during travel.

This depends somewhat on State of Charge of the trailer LiFePO4 batteries.

For meaningful charging from the TV, you pretty much need to do the following:

• Run a low gauge power wire from the battery supplementing the 7-pin (you need to reduce voltage loss as much as possible to get the most out of the amps the wire can sustain)
• Install an isolating DC-DC step up charger

It is possible you can do the above without an auxiliary charging cable, but it is not likely that the few amps you can draw through pin 4 of the 7-pin umbilical will do more than keep a topped up LiFePO4 topped up. Imagine how long you would need to drive to produce enough amps to recharge a depleted 280AH battery!

Anyway, I don't have all the answers on this but I'm working on it myself for my installation.

[campin]

Originally Posted by jjason

Thanks for posting your progress. A few questions:

1. Why did you go with 24V instead of 12V
2. Is the tow vehicle able to charge your batteries? If so, how? If not, how are you keeping the two systems isolated?
3. Do you have a wiring schematic/diagram?

To answer your questions...
12V vs. 24V, I think it boils down to a few things. One is wattage. I read a system above 600 watts is a candidate for 24V (48V for small houses). As for costs, both options are about the same after you factor in wire and a Dc to Dc step down converter. The 24V system may look cleaner (smaller gauge wire) and is slightly more efficient.

Regarding TV charging LiFe battery, I’m not comfortable with that. It’s a bit tricky and unnecessary in my case. The TV and TT charge systems are two separate, different animals.

And I don’t have a wiring diagram on paper but will post something in the near future. Thnx!

@lateott. I don’t have much knowledge about it but sure it’s doable.

[campin]

Originally Posted by craigav

You can purchase a BMS, I have seen them on ebay. If you are just using the used larger rectangular cells you will not be happy without a BMS. Most all lifepo4 batteries that are designed for drop in use have the BMS builtin. ~CA

Thnx for chiming in. Yeah I found this to be a hot topic ; ) Anyway the LiFePO4 cells are known to be very stable (I’ll bottom balance too). And should the battery pack reach critical SOC thresholds (under/overcharged), the system will shutdown. The PowerMon battery monitor (w/Bluetooth) will energize a relay to disconnect load. And to keep the individual LiFe cells happy, an optional equalizer/balancer and checker alarm are added. Other system checks are the inverter and Outback charge controller. So in my case I believe a BMS module is unnecessary. And fwiw BMS is known to have issues at times.

I just realized this is is a repeat answer. Lol