Modular 5KWH Milk Crate System

[jackal830]

Saw how small the LiTime Minis were and thought I could make a modular milk crate system. Turns out they are just the right size to be able to stuff them in a milk crate and still have room to grab the handles to lug them around.

The crates are each 42.5 pounds and the inverter section is 29 pounds.

System:


Milk Crates:


System Rear (wood cutting board on top of a wooden serving plate, lol):


Rear Power Connections


120A Circuit Breaker at each milk crate:


Inverter Mount Bottom (spacers to make sure lid will sit center on top of crate):


Carrying the inverter via handle (replaced 3/4 inch screws with 1.5 inch screws to better hold the handle)


I tested it out this weekend hooking up to my gas furnace. It's been 36 hours and it's still powering it (although almost dead). It's been in the 30's here, I suspect in blistering cold it wouldn't last a day, but still not bad.

The inverter wasn't made for LIFEPO4 (probably a reason why it was selling for $230). You can manually adjust charging and discharging voltage behavior to not damage your batteries, but the battery charge meter is totally oblivious as to how LIFEPO4 batteries work. Looking at actual voltage is the only way to tell how much charge is left.



I actually bought 2 inverters because they were so cheap. They are rated for 2400W, but I have 15A fuse on power strip.

Cost for one system (including wiring, lugs, etc) should come out to be around $1500 or so. I spent closer to $2000 with the extra inverter and everything required so I could run two simultaneously (each with one crate). I don't have any solar hooked up to it. I have solar on my house, but it's grid tied enphase, so charging would be tricky during a grid-down scenario.

Batteries are in series within the crate and parallel out of the crates to the inverter. Can hook one or two crates up. The two andersson connectors go up to 1AWG lugs (two 4AWG cables) for the parallel connection.

 

[Jmhai3]

I like the portability and interchangeable design.
In your last pick is that a Gas/propane heat unit or Oil-fired furnace?

I would like my cart project to also run my furnace, but the old Lennox has two motors (blower fan and oil pump) and the ignition system so don't think it would be practical. Right now, the cart is slated for 2-fridges, CPAP, a TV (router/WIFI), small miscellaneous devices, and test bed for future off-grid storge/workshop building.

 

[jackal830]

I like the portability and interchangeable design.
In your last pick is that a Gas/propane heat unit or Oil-fired furnace?

I would like my cart project to also run my furnace, but the old Lennox has two motors (blower fan and oil pump) and the ignition system so don't think it would be practical. Right now, the cart is slated for 2-fridges, CPAP, a TV (router/WIFI), small miscellaneous devices, and test bed for future off-grid storge/workshop building.

Mine is an 8 year old gas furnace. It takes 500W to run the blower on 'low' and 800W on 'high'. The furnace itself decides if it's going to do low or high. I think it depends on how far away it is from the target temperature (but I'm sure it's more complicated than this).

 

[Brucey]

Mine is an 8 year old gas furnace. It takes 500W to run the blower on 'low' and 800W on 'high'. The furnace itself decides if it's going to do low or high. I think it depends on how far away it is from the target temperature (but I'm sure it's more complicated than this).

Often the two stage furnaces start in low and then if they still haven't satisfied thermostat demand after say 10 minutes it will kick into high.

 

[Brucey]

Saw how small the LiTime Minis were and thought I could make a modular milk crate system. Turns out they are just the right size to be able to stuff them in a milk crate and still have room to grab the handles to lug them around.

The crates are each 42.5 pounds and the inverter section is 29 pounds.

System:
View attachment 182227

Milk Crates:
View attachment 182221

System Rear (wood cutting board on top of a wooden serving plate, lol):
View attachment 182224

Rear Power Connections
View attachment 182225

120A Circuit Breaker at each milk crate:
View attachment 182231

Inverter Mount Bottom (spacers to make sure lid will sit center on top of crate):
View attachment 182232

Carrying the inverter via handle (replaced 3/4 inch screws with 1.5 inch screws to better hold the handle)
View attachment 182234

I tested it out this weekend hooking up to my gas furnace. It's been 36 hours and it's still powering it (although almost dead). It's been in the 30's here, I suspect in blistering cold it wouldn't last a day, but still not bad.

The inverter wasn't made for LIFEPO4 (probably a reason why it was selling for $230). You can manually adjust charging and discharging voltage behavior to not damage your batteries, but the battery charge meter is totally oblivious as to how LIFEPO4 batteries work. Looking at actual voltage is the only way to tell how much charge is left.

View attachment 182233

I actually bought 2 inverters because they were so cheap. They are rated for 2400W, but I have 15A fuse on power strip.

Cost for one system (including wiring, lugs, etc) should come out to be around $1500 or so. I spent closer to $2000 with the extra inverter and everything required so I could run two simultaneously (each with one crate). I don't have any solar hooked up to it. I have solar on my house, but it's grid tied enphase, so charging would be tricky during a grid-down scenario.

Batteries are in series within the crate and parallel out of the crates to the inverter. Can hook one or two crates up. The two andersson connectors go up to 1AWG lugs (two 4AWG cables) for the parallel connection.

So those are 4AWG using SB175 connectors from the pair of 24V crates?

 

[jackal830]

So those are 4AWG using SB175 connectors from the pair of 24V crates?

4AWG on SB120s along with a 120A circuit breaker coming from each crate. The inverter is using 1 AWG lugs going to +/- terminals, each with two, 4-AWG cable ends inserted into them, crimped, (for parallel connection) with SB120's at the other end.

Running at max sustained load on the 2400W inverter would likely make these wires pretty toasty (one crate, 100A). The cabling I bought is rated to run at up to 105C, so it could do it. When running 2 crates there is very little chance these wires would be anywhere near that.

This is part of the reason I used a power strip with integrated 15A breaker to limit AC output to around 1800W. I didn't want to let this thing run at max load for long periods of time.

 

[jackal830]

Another thing to note is my particular inverter does not have a ground/neutral bond. When passing utility power, the ground/neutral bond at main panel is detected and used, but when it cuts over to battery that goes away.

For the furnace to work (as almost all gas furnaces will not work with floating neutral), you either need to have the inlet do the bonding, or stick a ground/neutral bonding plug into an outlet in the inverter power strip. I'd suggest having the inlet do the bonding, as it's the safest option in my opinion. The inlet I have supports both bonded and unbonded, you just have to make sure to wire it correctly.

I'd advise caution with a ground-neutral bonding plug. If you plug into a GFCI protected outlet, it will trip if you have the bonding plug in while on utility power (which is a good thing), it'd remind you to pull that plug out when on utility / charging.

 

[AlpineJoe]

That's a very nice clean build!

 

[jackal830]

I tested it out during a cold snap (the hottest it got was -6F and coldest a little under -22F). It ran the blower on my gas furnace for 21 hours, so not quite a day in the worst circumstances.