GhostCalc runs off the TI-84 Plus's own 4× AAA bay — there is no second battery hidden anywhere. Cells don't come in the box, and that's deliberate. Here's what to put in it, what to keep out, and how to tell when a reboot is really a battery problem.
It would be easier to drop a 4-pack in with every build. Three things make that a worse deal for you than buying your own.
Customs clears faster
Loose lithium and alkaline cells are one of the most common things pulled during international inspection. Shipping the calculator dry is what keeps every order moving.
Fresh beats pre-packed
Cells self-discharge, leak and age between the day a build is packed and the day it lands. A pack bought this week off a busy shelf beats anything we could seal in months earlier.
Weak cells break things
The ESP32-S3 pulls short, sharp current spikes every time it touches Wi-Fi. Cheap cells sag under that load, dip below the brown-out line, and the calculator reboots mid-answer.
Our picks
Two sets, and the honest split between them: get the rechargeable XTAR set if you use GhostCalc most days. Get the Energizer lithiums if you'd rather never think about a charger again.
🥇 Best overall — rechargeable
XTAR AAA 1.5 V 1620 mWh Li-ion
Flat 1.5 V curve1620 mWh~1000 cyclesCharger in the set
Why it wins
These are Li-ion AAAs with a regulator built in, so they hold a flat 1.5 V for roughly 95% of the discharge instead of drooping the way an alkaline does. That steady rail is exactly what the ESP32-S3 and the camera want during a Wi-Fi transmit. About a thousand recharges, so the running cost stops mattering quickly.
Best for
Daily drivers, all-day school carries, and anyone tired of buying a fresh 4-pack every couple of weeks.
Heads-up
They need a charger that can talk to the onboard regulator — a generic NiMH charger will not do it. The set bundles the right one. If the set is out of stock, buy the cells and add a compatible XTAR charger separately.
1.5 VLithium primary4–8× alkaline lifeRated for cold
Why it wins
Single-use lithium. It holds its voltage under load instead of collapsing, and lasts roughly four to eight times longer than an alkaline of the same size. More per pack, bought far less often.
Best for
Trips, exam weeks nowhere near an outlet, and a spare set left in a bag for the day the others die.
Heads-up
Every set is a set you eventually throw away. If GhostCalc lives in your bag five days a week, the XTAR pack pays for itself inside a couple of months — these are the better pick when charging isn't an option, not the cheaper one.
Generic or store-brand alkalines — voltage regulation is a coin flip.
Anything old or expired. Alkalines quietly shed about 3% of their capacity a year just sitting on a shelf.
Standard NiMH rechargeables. 1.2 V nominal is already under the line before the module draws anything.
Zinc-carbon or "heavy duty" cells. High internal resistance, brown out the second real current is pulled.
Mixed brands or chemistries in one bay — the weakest cell sets the ceiling for all four.
Cells that lived in a hot car or a freezer. Temperature extremes wreck the chemistry for good.
Is it actually the batteries?
When GhostCalc starts acting strange, batteries are the first thing to rule out — not the last. The tells:
Freezes or reboots the moment you send a question.
Wi-Fi drops mid-answer, then reconnects a second later.
The screen flickers or blanks during a camera capture.
A solve spins forever and never lands on an answer.
Everything has just gotten slower, and a fresh set brings the speed back.
Drop in a fresh set of one of the picks above before opening a ticket. Most "my GhostCalc keeps freezing" messages end right there.
What the bay needs
If you'd rather match the spec than the brand, this is what a cell has to do to keep a GhostCalc stable.
Form factor
AAA · LR03 / L92 / Li-ion
Quantity
4 cells
Min volts under load
1.35 V per cell
Peak current draw
~800 mA on transmit
Polarity
Embossed +/− in the bay
Location
TI-84 Plus rear door
Four habits worth keeping
Swap all four
Never mix an old cell in with new ones. The weakest one rate-limits the pack and wears the other three out faster.
One brand, one chemistry
Don't put alkaline and lithium in the same bay. Pick a lane and fill all four slots from it.
Pull them for storage
Not touching it for a month or more? Take the cells out so a leak can't ever reach the contacts.
Keep the contacts clean
A dry cotton swab on the bay terminals every few months stops the oxide film that quietly adds resistance.
No affiliation. These are simply the cells we run on the bench. GhostCalc has no relationship with either brand or seller, earns no commission, referral or affiliate fee, and nothing here is sponsored. The links point at the exact product we'd buy, with an Amazon search as a backup if a listing sells out or isn't available where you live — buy whatever you want, wherever you want. Rather not make the trip at all? Tick 4× Extra Batteries in checkout and a spare set ships with the build.