Proper service often requires specialized equipment as outlined in the PS-850/855 Battery Maintenance Guide .
This is the single most important test for the PS-855B. It's a built-in, automated test that measures the battery's ability to hold a charge and deliver power under load.
As of April 2023, production and publication services for these units have transitioned from Extant Aerospace Primary Manual CMM TP-483 (ATA 24-30-08) Service Literature Service Letter SL-170 provides detailed battery care and charging instructions. from the CMM or a list of authorized service centers for this unit? L3Harris PS-855B | SEAEROSPACE.COM
Wipe the surrounding shroud with a lint-free microfiber cloth. Fuse and Circuit Protection Replacement ps-855b maintenance manual
Without the manual's schematic, this repair is guesswork. With it, it is systematic.
The PS-855B maintenance manual outlines a preventative schedule to avoid sudden failures.
Grand Rapids, MI 49512-9704, USA July 30, 2014. [Link] Foreword. This manual provides information intended for use by persons who, PS-850/PS-855 Component Manual | PDF - Scribd PS-850/PS-855 Component Manual | PDF. 4K views230 pages. PS-850/855 Battery Maintenance Guide | PDF - Scribd As of April 2023, production and publication services
What specific are you currently facing?
| Specification | PS-855B | | --- | --- | | | 501-1712-02 | | OEM | L3Harris | | Output | 5.0 AMP, 5 VDC | | Input Power | 28 VDC, 15 Amps | | Battery Output Voltage | 24 to 28 VDC | | 5 VDC Converter | Adjustable +2.5 to 5.5 VDC, capable of delivering 25 watts | | Battery Output Current | Steady State Load: 10 Amps max | | Weight | 13.7 lbs (6.2 kg) max | | Dimensions | 7.820"H x 14.085"L x 2.400"W | | Amps/Hour | 5.0 Amp/Hour | | Environmental Qualification | DO-160C, Categories: [A2F2]-BB(C)E1XXXXSABABAWA[XXC3]XX |
This points to a failing reference voltage. The manual instructs you to probe the zener diode (ZD1) for stable voltage (e.g., 6.2V). If noisy, replace. Also check C11 (the main filter cap) for high ESR. Fuse and Circuit Protection Replacement Without the manual's
Pricing and availability are subject to change and were valid as of April 24, 2026.
[Normal Flight Operation] ──> Supplies 28 VDC trickle charge to battery pack │ (Essential Bus Failure) │ ▼ [Automatic Relay Transfer] ──> Instantly provides 24 VDC & 5 VDC backup power Manual Testing with a Stopwatch Connect the unit to an approved manual test station. Move the selector switch into the position. Click a stopwatch to begin timing the drain cycle.
According to the maintenance manual, 80% of “low +5V” cases are fixed by replacing C20, C21, and C23 (three capacitors costing under $5 total).
Always refer to the official PS-855B maintenance manual for your exact model revision before attempting any repair. When in doubt, consult a certified electronics technician.