Cayrex Lab is the educational companion to my battery R&D work — explore battery chemistries, compare technologies, understand what's actually inside the cells powering our world. Plus a closer look at the APC battery I'm developing.
A guided tour through the major battery chemistries — what they are, how they work, their strengths and weaknesses. Click any card for the deep dive with animated cross-section diagrams.
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Educational content only
This section explains battery chemistry for learning purposes. It does not include construction recipes or DIY instructions.
CHAPTER 02 · COMPARISON
How do they actually stack up?
Energy density, cost, safety, cycle life — the trade-offs that determine which battery is right for which application.
Values are typical hobbyist/commercial ranges · ● excellent ● good ● limitations
CHAPTER 03 · BATTERY WIKI
Battery vocabulary, demystified
The terms and concepts every battery enthusiast should know. Click between Basics for the foundational physics, or Glossary for definitions of common acronyms and jargon used across the field.
CHAPTER 04 · ZINC CHEMISTRY · KEY CHALLENGES
Why zinc is hard — and how it's solved
Zinc-based batteries promise low cost, abundance and safety. But the chemistry has deep, well-documented problems. Here's an honest look at the major challenges and the strategies researchers (including our lab) use to address them.
⚡ Practical Guide
Charging zinc cells the right way
Zinc plating chemistry does not behave like lithium-ion. Applying standard Li-ion charging protocols (CC-CV — constant current then constant voltage) to a zinc cell almost always shortens its life and creates dendrites. Below is a summary of the current best practice for cycling zinc-halogen, zinc-manganese, zinc-iodine and zinc-air cells in the lab.
✓ Recommended
CC + capacity cut-off
Charge with a fixed current (CC) until a defined coulombic capacity (mAh) has been transferred. Then stop, regardless of voltage. The stripping direction (discharge) can use either a voltage cut-off (0.5–0.8 V for zinc-halogen) or a symmetric capacity cut-off. This limits how much zinc plates each cycle, preventing dendrite tips from reaching the separator and giving a controlled "usable window" of the anode.
Typical charge cutoff: Q_target = 5–20 mAh/cm² depending on the plating substrate geometry.
✗ Avoid
CC-CV (Li-ion style)
In a Li-ion cell, holding at constant voltage (CV) at end-of-charge is safe because intercalation reactions are self-limiting once full. In a zinc plating cell, holding a voltage above the plating threshold creates a positive feedback loop: falling internal resistance → higher current → more plating → even lower resistance. The result is over-plating, thick dendrites, and eventually a separator short.
Never hold a zinc cell at a fixed voltage above open-circuit at end-of-charge.
Recommended parameters for lab-scale zinc cells
Parameter
Typical range
Notes
Current density (charge)
5–20 mA/cm²
Higher current → higher dendrite risk. Start with 10 mA/cm² for a new geometry.
Current density (discharge)
5–30 mA/cm²
Usually symmetric with charge current. Higher discharge is safer than higher charge.
Areal capacity per cycle
5–20 mAh/cm²
Zn-halogen and Zn-air cells: aim for 10 mAh/cm² baseline. Higher = more energy density but shorter cycle life.
C-rate equivalent
C/5 to 2C
If cell capacity = 20 mAh, C = 20 mA. Charge at 4–40 mA range for a 5 h to 30 min cycle.
Discharge voltage cut-off
0.5–0.8 V
Zn-Br: 0.8 V. Zn-I: 0.6 V. Zn-MnO₂ alkaline: 0.9 V. Below this, damaging over-discharge starts.
Charge voltage safety limit
≤ 2.2 V (Zn-Br) / ≤ 1.7 V (Zn-I)
Not a target — a safety ceiling to protect against runaway. Charge stops when Q_target is reached, not when voltage is reached.
Rest period between cycles
5–30 min
Helps zinc morphology relax and ion gradients level out. Longer rest gives cleaner voltage plateaus.
Full-strip cycle frequency
every 20–50 cycles
Occasionally discharge to zero to reset zinc plating morphology and remove dead zones.
Worked example — building a Zn-Br static cell
Cell design: 4 cm × 4 cm active area (16 cm²), 2 M ZnBr₂ + 0.8 M MEPBr electrolyte, zinc plating on carbon-polymer composite substrate.
Higher current tests dendrite tolerance but shortens cycle life. Start gentle and ramp up in later experiments.
Step 4 · Total charge current
I_charge = j × Area = 10 × 16 = 160 mA
Step 5 · Charge time
t_charge = Q_cell / I_charge = 160 mAh / 160 mA = 1 hour
Cycler stops charge automatically after 160 mAh transferred, regardless of voltage.
Step 6 · Discharge conditions
Same current (160 mA), cut off at 0.8 V
Coulombic efficiency = (Q_discharge / Q_charge) × 100%. Aim for > 98% on stable cells.
Neware / lab cycler protocol summary
CC charge: 160 mA, cut-off at 160 mAh OR 2.2 V (safety) Rest: 10 min CC discharge: 160 mA, cut-off at 0.8 V Rest: 10 min Loop: N cycles (typically 20–50 for baseline)
Voltage & current profiles — CC vs CC-CV
The two curves show what happens to voltage (blue) and current (orange) during a charge cycle. In CC + capacity cut-off (left), the charge stops cleanly when a defined coulombic charge has been transferred. In CC-CV (right), the voltage is held at a fixed maximum and the current tapers off — safe for lithium-ion, dangerous for zinc.
CC + Capacity cut-off
✓ SAFE
Voltage
Current
What happens: Current stays constant at 160 mA. Voltage rises naturally with state of charge. At 160 mAh transferred (1 hour), the cycler stops abruptly. No hold, no taper, no over-plating.
CC-CV (Li-ion style)
✗ AVOID
Voltage
Current
What goes wrong: Once voltage hits V_max, the cycler holds it there. For a lithium-ion cell this is safe — intercalation self-limits. For zinc plating, low internal resistance keeps the current high, which keeps plating more zinc. The result: over-plating, dendrites, and eventually a separator short.
CHAPTER 05 · COMMUNITY PROJECTS
Share what you've built
Have you experimented with one of these chemistries? Document your project and share what you learned — what worked, what didn't, the test results, the photos. All submissions are reviewed before publishing.
⚡ Coming soon
User-submitted battery projects
This section will feature community-contributed battery experiments — descriptions, photos, test data, lessons learned. Each submission is moderated before going live to maintain quality and safety standards. Got something to share? Submit below or contact us directly.
How it works: Until the upload form is fully live, your submission opens a pre-filled email to cayrex@gmail.com. Include any photos or measurement data as attachments. Submissions are reviewed for quality and safety; once approved, your project will appear in this section with your name (or pseudonym) credited.
SPOTLIGHT · OUR TECHNOLOGY
The APC Battery
A safe, modular, upgradeable zinc-based battery — engineered to replace lead-acid where it falls short. Built on the Cayrex Hyperflow platform.
ENGINEERED BY CAYREX
A direct lead-acid replacement.
A compact, modular static battery system built on Cayrex's Hyperflow platform — designed to challenge conventional lead-acid batteries. Strategically positioned between lead-acid and lithium: significantly better cycle life, safety and upgradability than lead-acid, at a price point comparable to AGM lead-acid. Comes with Zn-Br as default chemistry, but supports Zn-Mn, Zn-I and Zn-Fe — one battery, four chemistries.
Non-flammable aqueous chemistryWater-based electrolyte. No thermal runaway, no fire risk.
Upgrade, don't replaceWhen capacity fades — or when you want to upgrade the capacity or overall performance — refresh the electrolyte instead of replacing the whole battery.
One battery, four chemistriesDefault Zn-Br electrolyte; switch to Zn-Mn, Zn-I or Zn-Fe — no hardware changes needed.
Drop-in lead-acid form factorCompact 12V battery in the familiar size — same connector, same mounting.
No lithium, cobalt, or nickelZinc-based, abundant, ethically sourced — no critical material supply concerns.
Store for years — fully dischargedLead-acid, lithium-ion and sodium-ion batteries all suffer from calendar aging — their capacity and performance degrade over time even when unused. APC can be fully discharged and stored for years without degradation.
Quick reference for converting between concentration and mass — useful when working through electrolyte formulations in scientific literature.
Mass needed
// Molarity + Volume → Mass
mol/L
L
Weigh out
— g
Resulting molarity
// Mass + Volume → Concentration
g
L
Concentration
— mol/L
HELP BUILD THE NEXT PROTOTYPE
Support battery innovation.
Your support helps me move the Hyperflow and APC battery technology closer to commercial reality and also funds the build-out of the laboratory itself — instruments, cell hardware, electrolyte chemistry, and the safety infrastructure required for serious electrochemical research. It also keeps the YouTube channel and this lab open for everyone.