The Signal Report // ENERGY STORAGE
Energy Storage.
Grid batteries, chemistry, and controls, from someone who helps build the AI that cycles them. All reports →
18 in this beat · page 1 of 2
There Is No Such Thing as UL 9540A Certified
UL 9540A certified, UL 9540A listed, UL 9540A compliant: none of those are things. It is a test method with no mark and no listing. What it produces is a report whose numbers set your separation distances and your fire protection, and the method itself changed twice in about a year.
Read the report → Report 095 · Energy Storage · 2026-08-19 · 8 minA Gigawatt of Storage Is Half a Number
EIA reports 52 GW of operating US battery storage and never mentions energy. The same workbook holds 142 GWh, which is 2.75 hours, and the fleet splits into 257 one-hour units and 261 four-hour units. The planned sheet has no energy column at all.
Read the report → Report 089 · Energy Storage · 2026-08-16 · 8 minWhich Used EV Batteries Are Worth Reusing
A 2026 Applied Energy study built the cost model instead of assuming it, and the answer inverts the intuition. The chemistry with the cheapest metals, LFP, is the one worth reusing; recyclers have to be paid to take it. The nickel-rich packs are worth shredding. Recycling pays for materials, repurposing pays for durability, and no chemistry is good at both.
Read the report → Report 083 · Energy Storage · 2026-08-13 · 9 minThe Battery Fire Rate Fell 97 Percent
It is a real number from a real database, and it is the most quoted statistic in grid storage. The same document reports something the number cannot: of the 81 incidents recorded at the time of writing, only 26 held enough information to say what had gone wrong. The rate is measured. The reasons are mostly missing.
Read the report → Report 077 · Energy Storage · 2026-08-10 · 10 minWhy a Grid Battery Ships Oversized
PJM's reference battery is rated 200 MW for four hours and specified with 1,030 MWh of cells. Thirteen percent of them are installed to be consumed, with cell replacements booked for year five and year ten. The national planning model handles all of it by prepaying the wear at a rate that assumes one cycle a day.
Read the report → Report 071 · Energy Storage · 2026-08-07 · 10 minWhat the Ride-Through Rule Actually Requires
NERC PRC-029-1 becomes mandatory on 1 October 2026. Nearly every summary says it adopts IEEE 2800 curves and bans momentary cessation. The fourteen-page standard never mentions IEEE, and it permits current blocking in one of its three regions. What it really takes away is the freedom to choose your own measurement window.
Read the report → Report 065 · Energy Storage · 2026-08-04 · 9 minThe Batteries That Don't Follow the Grid
A diesel generator makes a voltage whether or not anything else is running. Almost every grid battery cannot: it measures the grid's phase with a phase-locked loop and pushes current in step. NERC now recommends grid-forming controls on all new storage, and notes that essentially none of the 680 GW in the queue has them.
Read the report → Report 059 · Energy Storage · 2026-08-01 · 9 minWhy Data Centers Drop Off the Grid
A lightning arrestor failed on a 230 kV line and 1,500 MW of Virginia data center load left the grid in under two minutes. No utility shed it. The utility's reclose sequence tries three times; the data centers' protection quits after three. Neither device malfunctioned, and ten days ago it happened again at twice the size.
Read the report → Report 053 · Energy Storage · 2026-07-29 · 7 minHow a Battery Megawatt Becomes 59 Percent of a Megawatt
Storage headlines are written in megawatts, but grid planners pay in accredited capacity. In PJM's next capacity auction a 4-hour battery is credited at 59 percent of nameplate and a 10-hour at 78. In Texas, a 1-hour battery is worth 13.71 percent in the summer evening window, and 1-hour and 2-hour units are most of what got built.
Read the report → Report 047 · Energy Storage · 2026-07-26 · 7 minWhat a Battery's Efficiency Number Leaves Out
Every grid battery gets quoted one round-trip efficiency figure, usually in the nineties, as if it were a property of the battery. It's a property of where you drew the boundary. When a national lab measured one real system every way, it came back at 93% and at 37%, and the gap was mostly air conditioning and idle time.
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