Joseph P O'Connor
I have spent twenty years engineering battery systems. This store is where I sell the parts I could not buy easily myself.
Most of my career has been on the large end of energy storage. Utility-scale battery systems, the kind measured in megawatt-hours, where the cell selection has to survive a third-party design review and a bad decision costs millions. I still do that work every day.
This store is the small end of the same discipline. Same chemistry, same failure modes, same questions about voltage windows and balance and thermal margin. The difference is that a home builder gets none of the engineering support that a utility project gets, and has to figure it out from forum posts.
That gap is the reason for the book, and the reason for this store.
The book
In 2016 I started writing Off Grid Solar because the resource I wanted did not exist. Everything available either covered grid-tied systems with off grid as an afterthought, or assumed you had already decided what to buy. I wanted a book that started at the load calculation and ended at a working system, used internationally recognized codes, and treated lithium as a real option rather than an exotic one.
It is now in its second edition, in English and Spanish, and it is used as training material by companies that install this equipment for a living.
"One of the best solar energy books of all time."
BookAuthority
"This is one of the first books on solar that I personally read and it has become required reading for our employees."
Global Solar Supply
Off Grid Solar also turned up on Alex Honnold's reading list in Outside magazine, which remains the strangest thing that has happened to it. He was adding solar to his van.
[Read Off Grid Solar →]
The field work
I have built and taught off grid solar systems in the United States, Haiti, Guatemala, Nepal, Portugal, and Virunga National Park in the Democratic Republic of the Congo. Some of those systems power homes. Some power a ranger station in a rainforest where the nearest grid connection is a concept rather than a place.
Building in those conditions teaches you which parts fail and which parts are worth carrying. That is most of what informs the catalog here.
How I choose what to sell
This is a small store on purpose. A few rules keep it that way:
- DC side only. I sell the parts between the cell and the inverter, because that is the part I can actually specify and stand behind.
- Chemistry first. Sodium-ion is not one thing. A sodium NFPP cell and a layered oxide cell behave differently enough that the charge parameters are not interchangeable, and almost nobody selling them says so. Every cell here is listed by its actual chemistry, with the charge window published.
- Sets, not bundles. When a kit exists, it exists because one specific configuration needs exactly those parts in exactly those counts. It is not a discount for buying more.
- Nothing I would not put in my own pack.
If you are stuck on a build, ask. I answer my own email.
[Browse the store →] [Contact →]