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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 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. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

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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