Hi all-
Home tinkerer here, I've built e-bike packs in the past, this is my 1st powerwall build.
Parts so far-
APC smart ups 750 (24v setup)
~160 voltage and capacity tested 18650 (used laptop cells from local re-cycler)
12ga copper household wire
20 cell holders
7s BMS (cheap non-manageable Chinese one)
large "security system" cabinet- about 2ftx3ftx5in with locking door- this would hold the cells.
Reason for PW build-
I've got the cells anyway.
In in San Diego w/ a 4kw solar panel setup. Because I also have an electric car (Leaf), I'm on the EV-TOU2 plan with SDGE.
so- at night, I pay ~19c/kwh, and between 12pm and 6pm, I pay (or get credit for) 57c/kwh.
This allows me to get a smaller solar panel setup than I use, only because I get 57c/kwh credit when the solar system is crankin'.
But it's not quite enough... I want to charge the bankwhen paying 19c, and grid-tie back at 57c between 12 and 6. I'm sure most here are in a similar boat.
I'm aware I can adjust the APC UPS to set a correct float voltage for a 7ssetup. I'm investigating what grid-tie inverters to use (more on that later).
so my plan is-
Use modified 24v APC UPS to charge at night, and provide emergency power to small appliances when power is out
Make individual 3.7v packs with a bolt connector at the top (looks like this is pretty common). Use resister wire for cell fuses.
Mount the 20s packs with 1 cell removed and the frame notched so I can push-mount it onto 1/2in pex (like this)
managed though the cheap BMS.
The cabinet can fit 7s all next to each other. I'll start the install at the top. This will allow me to pull a pack, add another 20 cells when I get them, and re-insert the pack.
I have 8ga and 4ga wires from my stereo install days- this would go to the grid-tie inverters.
Grid tie inverters-
I have a cheap sun-600g inverter that would operate in the range the 7s puts out. It cuts off at 22v, and 21v would be the lowest safe discharge voltage for a 7s setup, so I'm cool there (I have a BMS anyway). I could use this and hope it doesn't set on fire.... or....
My solar setup uses Enphase micro-inverters, so I have the monitoring station, etc.
This project uses an Enphase inverter w/ Leaf batterieshttp://www.myelifenow.com/2015/03/my-mini-ess-with-leaf-batteries-gets.html
I'll pick up an enphase m215 (or similar) with operating voltages in thesame range os the 7s build. I know 215w isn't much, but I could still discharge it fully during the 6hr peak usage window.
Ideas? Comments? am I crazy?
Home tinkerer here, I've built e-bike packs in the past, this is my 1st powerwall build.
Parts so far-
APC smart ups 750 (24v setup)
~160 voltage and capacity tested 18650 (used laptop cells from local re-cycler)
12ga copper household wire
20 cell holders
7s BMS (cheap non-manageable Chinese one)
large "security system" cabinet- about 2ftx3ftx5in with locking door- this would hold the cells.
Reason for PW build-
I've got the cells anyway.
In in San Diego w/ a 4kw solar panel setup. Because I also have an electric car (Leaf), I'm on the EV-TOU2 plan with SDGE.
so- at night, I pay ~19c/kwh, and between 12pm and 6pm, I pay (or get credit for) 57c/kwh.
This allows me to get a smaller solar panel setup than I use, only because I get 57c/kwh credit when the solar system is crankin'.
But it's not quite enough... I want to charge the bankwhen paying 19c, and grid-tie back at 57c between 12 and 6. I'm sure most here are in a similar boat.
I'm aware I can adjust the APC UPS to set a correct float voltage for a 7ssetup. I'm investigating what grid-tie inverters to use (more on that later).
so my plan is-
Use modified 24v APC UPS to charge at night, and provide emergency power to small appliances when power is out
Make individual 3.7v packs with a bolt connector at the top (looks like this is pretty common). Use resister wire for cell fuses.
Mount the 20s packs with 1 cell removed and the frame notched so I can push-mount it onto 1/2in pex (like this)
The cabinet can fit 7s all next to each other. I'll start the install at the top. This will allow me to pull a pack, add another 20 cells when I get them, and re-insert the pack.
I have 8ga and 4ga wires from my stereo install days- this would go to the grid-tie inverters.
Grid tie inverters-
I have a cheap sun-600g inverter that would operate in the range the 7s puts out. It cuts off at 22v, and 21v would be the lowest safe discharge voltage for a 7s setup, so I'm cool there (I have a BMS anyway). I could use this and hope it doesn't set on fire.... or....
My solar setup uses Enphase micro-inverters, so I have the monitoring station, etc.
This project uses an Enphase inverter w/ Leaf batterieshttp://www.myelifenow.com/2015/03/my-mini-ess-with-leaf-batteries-gets.html
I'll pick up an enphase m215 (or similar) with operating voltages in thesame range os the 7s build. I know 215w isn't much, but I could still discharge it fully during the 6hr peak usage window.
Ideas? Comments? am I crazy?