About the article

Sailor’s Battery Meter

(Summer Circuits 2010 article)

Sailor’s Battery Meter

On a sailboat, the condition of the battery is a major concern for obvious reasons. On the author’s boat, a 120 Ah lead-acid battery is charged from a 25 watts solar panel. The battery monitor described here was designed to give peace of mind. It consists of two sub circuits: a sensor and a control/readout.

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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

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Component list
Base board

R1 = 100kOhm
R2 = 47Ohm
R3,R4 = 10kOhm
R5 = 10kOhm SIL-5 array
P1,P2 = 100kOhm trimpot, horizontal (corrected from 10kOhm)

C1,C3–C6 = 100nF,lead pitch 5mm
C2 = 100µF 25V

L1 = 100µH

D1 = BAT85
D2 = 5.6V 0.4W zener diode
T1 = BC237A
IC1 = LM2931AZ-5.0, National Semiconductor (Farnell # 9489487)
IC2 = PIC16F690-I/P, programmed, Elektor # 090117-41

LCD1 = DEM16217, 2 x 16 characters
DEM16217, 2x16 characters
K1 (sensor) = 5-way socket strip, lead pitch = 2.54mm (0.1 inch)
K2 (programming) = 6-way socket strip, lead pitch = 2.54mm (0.1 inch)
K3 (NMEA) = 2-pin pinheader, lead pitch = 2.54mm (0.1 inch)
LCD connector: 16-way socket strip, lead pitch = 2.54mm (0.1 inch)
S1–S4 = pushbutton, Multimec type 3FLT6 (Farnell # 1132885)
4 pcs cap for pushbutton, Multimec type 1S09-16.0 (Farnell # 1132917)
PCB # 090117-1

Sensor board

SMD 0805 unless otherwise noted
R1 = 1kOhm
R2 = 100Ohm
R3 = 1MOhm
R5 = 0.01Ohm 1W, e.g. Tyco Electronics type CGSSL1R01J 9 (Farnell # 1174243)
R4,R6 = 100kOhm

SMD 0805
C1–C4 = 100nF ceramic

D1,D3 = 5.6V zener diode, SOD-80C case
D2 = 1N4148 SOD-123F case
IC1 = BQ2018TS-E1, Texas Instruments, TSSOP8 case (Farnell # 8407720)

K1 = 5-way socket strip, right angled pins, lead pitch = 2.54mm (0.1inch)
K2 = 2-way PCB terminal block, lead pitch = 5mm
PCB # 090117-2
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