Planning to convert a 6x12 cargo trailer.

[Grummy]

>> I'd think if it were pure sine, they'd plaster that all over the ad. Maybe it's a step up from the cheep modified square wave? Anyway, it's highly recommended.

It's an Inverter Unit, so I think your fine. 39lbs ? Are they building these without cylinder walls now ?? The last one I bought was a Pulsar and it is 8 pounds heavier !

https://www.amazon.com/Pulsar-G2319N-Ga ... den&sr=1-2

Too bad there is not much weight savings in a 1000 watt unit (nor a good selection of them) as that combined with a good battery charger could be a better option given all your solar capability.

[rebelrider.mike]

I did a little digging, and it turns out that total harmonic distortion is a measure of how close a modified square wave is to approximating a pure sine wave. I've seen it measured in dB, but when applied to inverters, it seems people go by percentage. So if it's less than 5%, it's considered a "pure" sine wave. As in close enough that most anything we're going to plug into it won't be able to tell the difference.

The Wen inverter generator claims a THD of 0.6% - 1.2%. The inverter I plan to buy at the moment claims a THD of >5%. So here I was worried about the generator's inverter, and it turns out to be way better than the regular inverter I wasn't worried about. I also looked into whether THD can be measured, and it can. But it's way over my head, and beyond the scope of this project, LOL. I got my pocket Oscilloscope so I can see how "clean' the wave is objectively. Already used it to see my house AC wave, and the modified square wave of an old UPS. That UPS is actually pretty bad. There is only one extra "step" keeping it from being just a square wave. And the peak negative voltage (not sure that's the right term) is not at the same value as the peak positive voltage. I suppose I should check the wave on the UPS I actually have on my computer.

Back to the trailer though, I got the first shipment of parts I plan to use on the build.


The small PWM controllers for dimming the reading lights. They work better than I thought they would. That big one I tried out before didn't give them quite the full current when turned all the way up. But the new ones do. Also these guys actually click off when turned down all the way. Not all of these gadgets have an off feature, and I didn't expect one from these. But they have it and I'm pretty happy about that.


Also got the solar charge controllers. These have a bit of a cult following, and people either seem to love them or hate them. They're definitely not usable right out of the box though. If you search You Tube for MPT-7210A, you'll find that some tinkering is required to get them to work just right. Mostly swapping out the capacitors and the horribly noisy fans. I can confirm the fans are terrible, LOL. But they both work, and can be programmed, so they should work out fine.

Later today I'm hoping to receive the last couple parts for the headboard panel. So I can build that while I wait for the trailer.

I've also updated the floor plan to include the power cable from the truck, the battery size and location, and the very approximate position of the axle.


The weight spreadsheet got updated too. I added a tongue weight box which shows what 12% of the total weight would be, and another box showing the remainder of the weight which will be on the axle. So someday, when I know the actual final weight of the trailer, I can shift things around inside until I get the right tongue weight. I don't know for sure, but I think I'll be removing about 250 lbs of OSB from the walls and doors as soon as I get the trailer. I'm not sure any of it will even go back in, or if I'll just save it for a future project.

[rebelrider.mike]

Been playing with those solar controllers I bought. Even driving them at maximum I won't be able to get more that 292W from each. As I learn more about solar panels and how they work, I'm realizing this won't do, so I'm rethinking how I'll manage the charging setup.

I know I want 10 solar panels. May as well use up the whole roof space right? I also have the battery design I want, and I don't want to change that. So I've been looking for a controller that will do fit all the parameters. I think I'm close.

The panels are from Grape Solar. Here are their specs:

100 Watts each, 600V maximum for the system they're hooked up to.
MPP volts is 19.12
MPP amps is 5.32
Open circuit voltage is 23.1
Average energy per day is 300 Wh (probably less in the PNW, LOL)

The battery is like this:

8s2p LiFePO4, "24V" 25.6V nominal
Ranges from 29.2V to 20V
Maximum charge and discharge is 80A (based on the BMS I choose)
Approximate energy storage is 3,072 Wh

The charge controllers I'm finding don't go over 100V, except a couple that I don't want to use. So I can put up to 4 panels in series and still have an open voltage of 92.4V. If I put them 2 in parallel, that uses 8 of the panels. That's as close as I've gotten so far. I could still use the last two panels on one of the green controllers. And I can think of several other projects that can use the spare one.

I'm looking pretty close at this controller:
https://www.amazon.com/dp/B08HM1STQP/?coliid=I22JHY5MZ1V725&colid=1E6B1UUZBLNWO&psc=1&ref_=lv_ov_lig_dp_it
I think it will do the 4s2p panel configuration, and it can be setup through a phone app. Which I think is pretty cool. Most importantly, it allows user defined battery specs.

Well, I'm off on yet another road trip. I think while I'm gone, if my phone cooperates, I'll take another look at other people's solar setups and weight saving ideas. I've learned quite a lot since the last time I read through them.

[Modstock]

One reason my trailer weighs in at 1600 lbs is I have no 12 volt battery power. I wanted to install lights, battery, ect but ive went without power for so long I realized we didnt need it.
Water on the other hand can add alot of weight. We carry two 6 gallon tanks with us but most of the time we fill up one. Each 6gall jug weighs in at 50lbs each when full.
If its just a weekend, we get by on 2.5gal .
Usually we'll fill up the water at the closest place near camp cause you will feel that extra weight on hills.

Im surrounded by mountains here, everywhere is uphill.
Now if I can keep my woman from adding more stuff inside, thats the challenge. Every winter I take out things we dont need in secret.

Cant wait to see your build started.
Enjoy


Sent from my SM-A115AP using Tapatalk

[rebelrider.mike]

I totally get that. If I was stuck with lead-acid, I'd probably do without anything but the grid hookup. Unfortunately, my wife and I get pretty miserable when it's hot out, and there's lots of times we don't go camping because it's just too hot out. And I'm not sure I'd be comfortable with a Li-Ion battery either. At least not one big enough to power an A/C. But the LiFePO4 battery makes it feasible for me, and compared to the A/C, the rest uses very little power anyway, so it's worth it for the convenience. The battery itself will weigh a little less than 50 lbs. Though the solar panels and brackets will be more than 150 lbs.

Very cool though that you're able to keep your trailer down at 1,600 lbs. I'm planning on taking 4 gallons of water each trip. We don't use a lot of water either, and there's usually a source where we're going anyway. So we'll save a lot there. I've made some estimates and wild guesses on weights of things I plan to add, and I'm still at about 1,500 lbs. I'm sure that will go up as I get actual parts and pieces installed.

We're used to tent camping with only a few bins of gear in the back of the truck. So if week can resist the temptation of just throwing extra stuff in because there's room, we should be ok, LOL.

[Grummy]

>> The battery itself will weigh a little less than 50 lbs.

How many amp hour battery is this going to be ?

[rebelrider.mike]

If I buy all 16 cells, it should be about 3 kWh. If each cell is 60 Ah as advertised. Battery companies tend to exaggerate a little.

[Grummy]

>>>If I buy all 16 cells, it should be about 3 kWh. If each cell is 60 Ah as advertised. Battery companies tend to exaggerate a little.

Sixteen 60ah batteries ? Does that theoretically make 960Ah?
I took an online kwh to Amp Hr at 24 volts indicated a whopping 125 Ah.

I was just attempting to make a comparison with my 200ah Lifepo (which supposedly allows for 200amp draw and charge capability), because my battery weighs 52lbs.

Certainly you are not going to use 10 solar panels to charge a 125amp hour battery bank (or maybe you are?). And on the other side of my confusion, I'm not sure how one gets to 960Ah in around 50lbs. Seems a little too good to be true ? if they

If in the end you only really have a 125Ah battery, wont you be a bit limited with what you can simultaneously draw off of that ?

[rebelrider.mike]

Well, I could have my math wrong, so I'll share it. I think I've got it all right, but I'm new at solar.

Each cell would be 3.2V nominal, and 60 Ah.
Volts x Ah = Wh, so each cell would be 192 Wh.
In an 8s2p configuration, the battery will only have 120 Ah.
But Watt-hours are additive regardless of the configuration of the cells in the battery, so 16 cells x 192 Wh per cell is 3,072 Wh, or about 3 kWh.

Each cell is capable of 180 Amps continuous charge or discharge. They will also be in pairs (parallel), which doubles the maximum continuous current to 360 Amps.
As far as discharging, with everything on, and with the fridge and A/C unit both peaking, it all should still be below 75 Amps. It's extremely unlikely that everything will be running full power at once, More like 20A or less most of the time. But just the same, I've picked out a BMS that will limit the battery to 80 Amps either direction.

For charging, each panel is 100W, and if the charge controllers could actually get that much from each panel and send it to the battery without loss, there could be as much as 1000 Watts, and at the batteries lowest voltage of 20V, it would be receiving 50A.

Between the truck power, inverter generator, and grid power (which can only be used one at a time) grid power would still only be able to send up to 20A to the battery. So a theoretical upper limit of 70A could be charging the battery at once. Though some of that would likely be running at least the fridge from time to time. And as the battery gets more charged, the current will drop.

For weight, each cell is listed at 1.2-1.4 Kg. That would be about 3 lbs each. Then 16 would be 48 lbs. This is just the cells without the BMS and wires and things.

This is all still theoretical, based on advertisements and spec sheets. For all I know they're lying through their teeth. As I gather parts though, I plan to hook it all together before I install it in the trailer. Check each cell for any heat under load and actual capacity. That sort of thing. Also the plan changes a little every time I learn something new, so the actual setup I build may very well be a bit different than what I've got planed right now. All depends on whether or not it works, LOL.

I can do a capacity test on a little tester I have. To see if it can handle the high discharge current though, I'll have to find something with low resistance and a high tolerance to Watts. Like an old heating element or something. In fact, I'll want to test the inverter, converter, and charge controllers, and the fridge, to see how much heat they build up in an enclosed space.

Well, anyway, I hope that makes some sense. I've got spreadsheets helping me keep track of it all, but it's still a lot to figure out.

[Grummy]

>>> Well, anyway, I hope that makes some sense....

Oh ya.. clear as mud ! Lol !

Well, I'll be watching and learning as long as you keep us up to date.

Thanks

[rebelrider.mike]

I found this charge controller which I think can do all 10 solar panels:
https://www.amazon.com/PowMr-Controller-Backlight-Battery%E3%80%90Software-Version%E3%80%91/dp/B0719PGGBS/ref=psdc_2236627011_t1_B091FMHGZH

I'm also looking for a balance charger to maintain the battery when I'm at home. I found this one, but it's weird.
https://www.amazon.com/dp/B087CJZTXJ/?coliid=I2ZHXXNPEXRMLT&colid=1E6B1UUZBLNWO&psc=1&ref_=lv_ov_lig_dp_it
It doesn't come with a power supply, but to use it at it's full potential I'd need a 34V 1000W DC power supply. I don't think they make those. At least I haven't found one.

[rebelrider.mike]

Still waiting for the actual trailer to be ready. Any day now... Or next month.

My wife asked an interesting question: Should we get insurance on it? I don't know. I suppose with the money I'll be putting into it, it's probably a good idea. Progressive does my motorcycle insurance. They're happy to insure my trailer, but I'll have to figure out what the stuff I add to it is worth. So I've added prices to all the things on my weight spreadsheet. I'll be able to add it all up as I go. I don't know if insurance is even required in Washington on a cargo or camping trailer. I'll have to go look.

It seems the planning is pretty much done. I haven't thought of anything lately to add or change. I've started buying a few parts while I wait for the trailer itself. I've got the battery cells ordered, and found a charge controller for the solar panels. I'll be buying them next, I think.

I've been helping my grandpa clean out his shed the last couple months. Unfortunately, he won't be around much longer and he doesn't want us all stuck with his accumulated stuff after he's gone. So we're doing it now as a sort of early inheritance. I found a small sink in his stash that will fit the trailer perfectly. He's got all sorts of interesting things tucked away, and almost everything has a story behind it. I found a box of tiny 0.8 cc model airplane engines that were seized up and hadn't been run in 45 years. I got them apart and cleaned up, and had enough good parts to put one working engine together. Grandpa got a kick out of seeing one run again.



Anyway, we're still going through stuff, so who knows what I'll find that can be used in the trailer build...

[Karebru]

My wife asked an interesting question: Should we get insurance on it?

Wives are good at thinking about that kind of stuff. We insured ours through Progressive, because she thought about it.
She left the details up to me. I decided my labor was fun time, and based the amount on what it cost in materials, etc. and not some estimated market value.
Your experience may vary.

[rjgimp]

Wow. Four pages already and you haven't actually built anything yet? Awesome!

I suspect this thread will hit 200 pages. You have good stuff going on here. I'm happily following along.

[rebelrider.mike]

Haha!
What I lack in experience I make up for in excessive planning. Forums are a great way to keep track of thoughts and plans, and also other people's suggestions. I may not do all the suggestions, but I do appreciate and consider them seriously.

I was looking at Progressive's website, and they'll insure the specific cargo trailer I'm buying, as well as stuff inside. I get to pick the value of the stuff inside.

I don't normally keep track of expenses when I work on projects. Takes some of the fun out of doing it. I just spend a bit from month to month until it's done. But in this case, since I'll want insurance, I suppose I'd better keep track. So my weight tracking spreadsheet is now a weight and cost tracking spreadsheet:


Same color scheme. Green is what I know for sure. Yellow is what has been advertised or I've found on datasheets. Values not listed or left white, I've either guessed or haven't thought much about yet. But it's all looking good so far.

I should be getting the trailer any day now. They said 8-12 weeks,and we're into week 8 or 9 now. Should have it no later than Thanksgiving.