Math & physics check please? Rolling Power Station.

[Rednecktek]

Ok, I've double and triple checked my numbers, re-done my equasions, and... is this right???

Ok, so the project is to make a rolling tool box solar generator with enough oomph to power an RV's 30a shore connection for a week, OR run my wire feed flux core welder and grinder in the field.

Basic parts list:

PowMr 3.2kw 24v AIO (Ordered about 3 days before the 3.6kw came out, Doh!)

Harbor Freight Bauer Modular Toolbox

JBD 8s 100a BMS (From the CC sale)

Eve 230ah cells

MRBF fuses, AiLi shunt, outlets, portable solar panels, Anderson jacks, breakers, fans, etc.

Here's my quandry; converting the metric measurements for the cells into 'Murican...


An 8s pack would be 174mm wide, 432mm deep (8×54mm) and 205mm tall plus posts. In 'Murican that would make a pack 6.86" wide, 17" deep, and 8" tall.

The Bauer toolbox says:




So 3 packs of 8s would be 20.58" wide, 17" deep and 8" tall, right?

Can I actually do a 3p battery set in there?? 230ah 24v would be 19.5kwh of battery capacity?

My plan is to build a plastic shelf over the top of the batteries and lay the AIO on its back, DIN rail breakers next to it, all the bus bars and fan controllers. There should be plenty of space if I put the AIO against the hinge side, right? 120mm intake and exhaust fans will be on thermostats.




Can someone please check my math and all on this? Am I going to get bit by physics?

 

[wpns]

A few random thoughts:

You’ll need battery separators

Those dimensions are outside, and include the handle, not sure how much room there is inside.

That toolbox is rated 60# maximum, you have way more than that, plus you’ll reduce structural integrity by cutting fan holes. Some of the reviews say it isn’t very strong.

Can you show your math on the battery KWHR rating? I’m not sure how 8S3P at 230AH gets you 19.5 KWHR

 

[Rednecktek]

A few random thoughts:

You’ll need battery separators

Kinda planning on using the thin cutting board plastic sheets.

Those dimensions are outside, and include the handle, not sure how much room there is inside.

Good point. Hmmm... and just too small for a pair of 304's the other direction.

That toolbox is rated 60# maximum, you have way more than that, plus you’ll reduce structural integrity by cutting fan holes. Some of the reviews say it isn’t very strong.

I've got 2 already and they don't feel any flimsier than my brothers' Rigid or my dad's Kobolt, but I didn't think to math out the weight.

4140g per cell × 24 cells = 99360g which is 219lb! Ooohhhkkaayyy... 3/4 plywood in the bottom?

Can you show your math on the battery KWHR rating? I’m not sure how 8S3P at 230AH gets you 19.5 KWHR

8 Cells × 3.55v = 28.4v × 230ah = 6532wh, × 3 batteries = 19,596 wh. Did I do that right?

 

[wpns]

8 Cells × 3.55v = 28.4v × 230ah = 6532wh, × 3 batteries = 19,596 wh. Did I do that right?

Ah, OK. I’d have used 3.2v nominal for the cells, but you are close enough.

 

[wpns]

Kinda planning on using the thin cutting board plastic sheets.

Sure, but it increases the size of the batteries.

 

[wpns]

I've got 2 already

Even better, you can physically measure the available interior space. And even mock up batteries and the inverter with cardboard

 

[wpns]

219lb! Ooohhhkkaayyy... 3/4 plywood in the bottom?

And on the sides and brackets to keep ut all together and something to keep the handle from breaking and the wheels from getting crushed and …

 

[Rednecktek]

Yyyeeeaaahhhh.... even if I ran 2p that's 145lb just in batteries.

I'm thinking this is doomed to fail...

Time to break out the welder!!

 

[chrisski]

For the mobile portion, I’m thinking of getting a 600 lbs Dolley and cutting it to size and welding.

https://www.lowes.com/pd/Milwaukee-800-lb-2-Wheel-Red-Steel-Heavy-Duty-Hand-Truck/50042444

I have a 100 lbs portable generator on a dolley like that I move around. The dolley lies flat and I lift and move it with a rope. I am even thinking of adding another set of wheels to make it like a wagon. A good set of wheels may run up to $50 to install.

 

[Rednecktek]

Hmmm... a wagon might be an idea... build a box and mount it to a cart...

 

[alcook62]

Ok, I've double and triple checked my numbers, re-done my equasions, and... is this right???

Ok, so the project is to make a rolling tool box solar generator with enough oomph to power an RV's 30a shore connection for a week, OR run my wire feed flux core welder and grinder in the field.

Basic parts list:

PowMr 3.2kw 24v AIO (Ordered about 3 days before the 3.6kw came out, Doh!)

Harbor Freight Bauer Modular Toolbox

JBD 8s 100a BMS (From the CC sale)

Eve 230ah cells

MRBF fuses, AiLi shunt, outlets, portable solar panels, Anderson jacks, breakers, fans, etc.

Here's my quandry; converting the metric measurements for the cells into 'Murican...
View attachment 252077

An 8s pack would be 174mm wide, 432mm deep (8×54mm) and 205mm tall plus posts. In 'Murican that would make a pack 6.86" wide, 17" deep, and 8" tall.

The Bauer toolbox says:


View attachment 252086

So 3 packs of 8s would be 20.58" wide, 17" deep and 8" tall, right?

Can I actually do a 3p battery set in there?? 230ah 24v would be 19.5kwh of battery capacity?

My plan is to build a plastic shelf over the top of the batteries and lay the AIO on its back, DIN rail breakers next to it, all the bus bars and fan controllers. There should be plenty of space if I put the AIO against the hinge side, right? 120mm intake and exhaust fans will be on thermostats.

View attachment 252087


Can someone please check my math and all on this? Am I going to get bit by physics?

I came up with a total of 16.56 kWh using an online Ah to kWh calculator:

Amp-Hours (Ah) to Kilowatt-Hours (kWh) Conversion Calculator​

Convert amp-hours to kilowatt-hours using the calculator below by entering the electrical charge in Ah along with the voltage.

Amp-hours:
Ah
Volts:
V


convert kWh to Ah

Kilowatt-Hours Results:​

16.56
kWh
I don't know the exact formula they use to reach that total, but it's on the internet so it has to be true, right?

Another thought: I've been looking at those PowMr 24-volt inverters while considering future upgrades. They make both High-Frequency and Low-Frequency inverters. Following the link you supplied I couldn't determine which inverter this is. Have you considered the benefits and drawbacks of both styles?

 

[chrisski]

Hmmm... a wagon might be an idea... build a box and mount it to a cart...

Even for my 100 lbs build, that is too heavy to move on most small wheel carts. The bigger wheels on the dolly let me move mine over grass and light gravel easy.

Ideally, I’d like a “big red wagon” with big wheels that could be pulled over light gravel and grass. The ones I see people towing behind them at fairs are just not enough.

 

[wpns]

Now you know why most 'portable' systems are built on hand trucks.

 

[HighDesertOffgrid]

Hmmm... a wagon might be an idea... build a box and mount it to a cart...

harbor freight green wagon?

 

[chrisski]

harbor freight green wagon?

That seems great.

 

[wpns]

harbor freight green wagon?

Looks like they make one that has 1000 pound capacity, that should work. Just don’t try to use it on hills or significant slopes, if it gets away from you that’s gonna do a lot of damage.

 

[HighDesertOffgrid]

Looks like they make one that has 1000 pound capacity, that should work. Just don’t try to use it on hills or significant slopes, if it gets away from you that’s gonna do a lot of damage.

Agreed. Would hate to see rednecktech chased down a hill by his solar generator.

 

[Norwasian]

Another thought: I've been looking at those PowMr 24-volt inverters while considering future upgrades. They make both High-Frequency and Low-Frequency inverters. Following the link you supplied I couldn't determine which inverter this is. Have you considered the benefits and drawbacks of both styles?

Are there any benefits to HF inverters? The only one I've seen touted is that they are cheaper to buy...but one gets what one pays for, right? Oh, I suppose another benefit might be that they are more lightweight, and some will claim they are more energy efficient in their inversion process.

Personally, I'll stick to the more durable and resilient LF inverters insofar as possible. I'm making a list of them, as I have found the information difficult to find, which I plan to post here somewhere eventually.

 

[chicagoandy]

I'm a little skeptical on that inverter. The specs say a 110v output? North American electrical standard is 120v output, and inverters should output 120V. Most north American electrical devices will accept voltage as low as 110V, which is why that number is frequently mentioned. If the inverter will only put out 110V, then any voltage drop will drop the voltage below the accepted minimum voltage for the appliances you're planning on using.

 

[OffGridForGood]

Garden wagon with 8" wheels is "The Cat's meow" to move around my moble 24v set up.
and the big pneumatic tires roll right over cords and stuff that hard wheels get stuck on.
And with four tires - unlike a cart set up - it stays level and you don't have to tilt it to move it.

 

[chrisski]

I'm a little skeptical on that inverter. The specs say a 110v output? North American electrical standard is 120v output, and inverters should output 120V. Most north American electrical devices will accept voltage as low as 110V, which is why that number is frequently mentioned. If the inverter will only put out 110V, then any voltage drop will drop the voltage below the accepted minimum voltage for the appliances you're planning on using.

Specs say the voltage output is adjustable +/- 10%. It also auto detects 50/60 HZ.

https://cdn.shopify.com/s/files/1/0746/0415/1079/files/POW-LVM3.2K-24V_User_Manual.pdf?v=1711005980

Seems like this makes it good for the 120 V 60 HZ US market and the Japanese 100V 50/60 HZ market.

With 1600 watts max of panels and a 3 kW inverter, this should take care of any normal 30 amp camper as long as electric heat or air conditioning is not used.

Garden wagon with 8" wheels is "The Cat's meow" to move around my moble 24v set up.
and the big pneumatic tires roll right over cords and stuff that hard wheels get stuck on.
And with four tires - unlike a cart set up - it stays level and you don't have to tilt it to move it.

For me the air tires are nice, but they will need attention unlike hard tires. I'm used to coming back to a piece of equipment I have not used in a while to see the air tire is flat or ruined and then that adds hours to the project to replace the tire with a trip to the store. It'd be a flip of a coin for me or how I feel at the moment what I'd want on it.

 

[Rednecktek]

harbor freight green wagon?

I thought about that too, but I'm thinking instead using one of the red hand trucks and welding a couple runners up the back. Build a 3-battery-wide box and mount the AIO above it with the outlets. We won't have to move it far and the hurdle is really getting it in and out of the back of the van. The big loopy handle will be the easiest thing to grab and steer with I think.

A little plate steel and some plastic top rails to hold all the cells in place while it's rolling around just in case it gets knocked over. I can build a top tray for all the fuses, BMS's, and other guts right into the top of the box, then mount the outlets and shunt to the face of it.

 

[Norwasian]

I thought about that too, but I'm thinking instead using one of the red hand trucks and welding a couple runners up the back. Build a 3-battery-wide box and mount the AIO above it with the outlets. We won't have to move it far and the hurdle is really getting it in and out of the back of the van. The big loopy handle will be the easiest thing to grab and steer with I think.

A little plate steel and some plastic top rails to hold all the cells in place while it's rolling around just in case it gets knocked over. I can build a top tray for all the fuses, BMS's, and other guts right into the top of the box, then mount the outlets and shunt to the face of it.

Still not picturing how the assembly is rain-proofed. In my part of the world, that would be a high priority.

 

[Rednecktek]

Still not picturing how the assembly is rain-proofed. In my part of the world, that would be a high priority.

Yeah, that's why I started this plan with a rolling toolbox, then the only exterior holes could be made weather resistant...

I may just have to nerf the capacity and use 100 or 160ah cells. When I get bandwidth I'll have to math out the weights of 2p and 3p 100ah and 160ah batteries in the tool box.

 

[Rednecktek]

Well, it looks like the 100ah cells are 2kg each so about 35lb/battery which puts a 2p at 70.5lb and a 3p would weigh in at 106lb. Still more than the 50lb limit the box claims but considering how much my power tools and batteries weigh, I'm thinking a piece of plywood in the bottom would work fine.

Dimentionally, each battery would be 160mm wide, 120mm tall (plus terminals), and 400mm deep, or in 'Murican 6.5" wide, 4.75" tall, and 15.75" deep. Plenty of room in there for that.

Between this and my laundry room battery, I'm gonna be dropping just shy of $1000 in cells. Ouch!