Backup batteries: leaks, suicide & replacement

Two battery plagues: those that leak and eat the board (Amiga, arcade PCBs, cartridges), and those that hold a protection/key whose death kills the game (suicide, Sega/Capcom). Opposite problems, same vigilance.

1) Leaking batteries (the silent killer)

• Type: old NiCd / Varta (rechargeable, on a soldered base) and backup coin cells. Varta cells leak an alkaline electrolyte that eats traces, vias and components nearby — often under the battery.
• At-risk machines: Amiga (clock/NVRAM), CDTV, arcade PC motherboards, save cartridges, some battery-backed JAMMA boards.

Survival step

On any stored machine: remove the Varta/NiCd battery immediately. If it has already leaked, neutralise (vinegar then IPA), inspect under the microscope and repair the eaten traces before they open (see traces & vias).

• Clean replacement: a lithium cell (CR2032 on a holder) with a series diode (prevents charging a non-rechargeable cell), or a supercapacitor for the clock, or a remote coin cell off the board (wires + holder).

2) Protection batteries (the "suicide")

Some boards keep a decryption key or a config in volatile RAM held by a battery. Flat battery = data lost = dead game ("suicide"), even if the hardware is perfectly healthy.

System	What the battery holds	See
Capcom CPS-2	decryption keys (SRAM)	CPS-2 de-suicide
Sega FD1094 / FD1089 (System 16/18/…)	key in the custom (battery-backed)	System 16
Sega System 24	config RAM / data	system page
Konami (some)	EEPROM/params, not always a battery	system page

Before desoldering anything: check whether the "fault" is a suicide (unbootable board but healthy hardware). The fix is not an iron but a key reprogramming (de-suicide) or phoenix ROMs — described on the system page.

Replace a key battery WITHOUT losing the key

If the keys are still alive, replace the battery without cutting the SRAM's power: piggyback a fresh cell in parallel before removing the old one, or keep the board powered during the swap. A moment's slip = suicide. Per-system detail on its PCB page.

Good practice

• Check batteries on every acquisition; never store a board/console with its original Varta.
• Document the value/type and polarity before removal.
• Prefer lithium + diode or a supercap to replace a NiCd.

See also

• Traces & vias · PCB fault-finding · CPS-2 · System 16 (FD1094) · CDTV

Sources & attribution

• Synthesis of established community knowledge (Amiga Varta leak, CPS-2/FD1094 suicide); precise procedures = the cited system pages, not invented.

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

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