Battery Maintenance, Connections, and Terminals

Published October 3, 2026. Built by Jeremy Panasuk.

Direct answer: A Battle Born 100 Ah terminal is 0.25 inch brass with a 3/8 inch hole, and the suggested hardware is 3/8 inch or 5/16 inch. Torque is 9 to 11 ft-lb. The manual says not to finger-tighten, and that failure to secure the connection can cause severe damage and will void the warranty. A Lifeline GPL-31T uses a marine terminal, M10 on the positive and M8 on the negative, and both of those thread sizes take 70 in-lb (7.9 Nm). Inch-pounds are not foot-pounds.

The cabin calculator still decides how many terminals you are torquing. Ah = (Wh/day × autonomy days × 1.25) ÷ voltage ÷ depth of discharge. At 1,000 Wh/day, 2 days, 12 V, and 0.80 depth of discharge, that is 260.4167 Ah, about 260 Ah. Three 100 Ah lithium batteries in parallel cover it (300 Ah). The AGM version of the same inputs, depth of discharge 0.50, is 416.6667 Ah. Four Lifeline GPL-31T batteries are 4 × 105 = 420 Ah at the 20-hour rate, which is the count on the AGM guide. Each battery has its own positive and negative, and each of those studs gets the torque that belongs to that battery. Mixing the two torque numbers is how a stud gets ruined.

Lithium posts

The spec table lists terminal torque as 9 to 11 ft-lb. The install chapter repeats it as 9 to 11 ft-lbs and says failure to meet that specification may result in system damage or failure. The parallel and series chapters both say “DO NOT finger tighten” and both say inadequate tightening can result in severe damage and will void the warranty. The box includes 5/16-18 bolts (1 inch and 1 1/4 inch), washers, and nylok nuts. The bolt has to reach the nylok insert. Stacked lugs can need the longer bolt. Order on the terminal is bolt, washer, lug, terminal, washer, nut in the diagram the manual labels as proper.

Maintenance is split by wiring, which is the subject of series and parallel. If series batteries are not on a multi-bank charger, the manual recommends a full individual charge once per year, especially with frequent use, so the batteries balance internally. Parallel batteries do not need that individual charge. They need a regular charge to 14.2–14.6 V. The BMS starts a passive balance when voltage exceeds around 14.2 V. Storage is separate: charge to 100%, then remove the negative cable from one battery. The percent those stored batteries lose is on how long a battery holds a charge, not a terminal spec.

Nothing in the lithium manual tells you to wash a terminal with baking soda. That step belongs to the AGM quarterly inspection below. Putting it on a lithium post is this page’s refusal, not a second procedure.

AGM posts, and the gas the connection shares a compartment with

Lifeline’s terminal table lists the GPL-31T, along with several other GPL models, as a marine terminal in copper alloy, positive M10 and negative M8. Torque in section 4.2 is 35 in-lb / 4.0 Nm for M6, and 70 in-lb / 7.9 Nm for M8 and M10. Both studs on a GPL-31T are in the 70 in-lb row. This page does not convert 70 in-lb into foot-pounds. 70 in-lb is the number to set.

Quarterly, Lifeline says to inspect each terminal for corrosion deposits. If deposits are present: remove them with a wire brush, neutralize with a baking soda solution, dry, then apply NO-OX-ID grease. If the connection was loose, or had to be loosened, re-torque to section 4.2. That baking-soda sentence is an AGM service step in document 6-0101.

The same manual’s safety chapter is the limit on how casually a terminal gets serviced. Section 6.1: hydrogen can ignite at concentrations as low as 4% in air, and “never install a Lifeline AGM battery in a sealed or an airtight container.” Section 6.2: all lead-acid batteries contain sulfuric acid in the electrolyte, which can cause chemical burns to body tissue. Lifeline AGM batteries are classified nonspillable, and exposure is still possible if the battery is cracked open or crushed. If electrolyte is displaced, avoid contact with skin, eyes, and clothing; flush with water and call a physician immediately. Section 6.3: shorted terminals can deliver high current; the resulting heat can cause severe burns and is a potential fire hazard. Accidentally placing metal objects across the terminals can result in severe skin burns. Remove belt buckles, watches, bracelets, and rings. Insulating gloves and insulated tools are the manual’s further precaution.

Install upright, terminals facing up, unless Concorde has approved another orientation. Leave at least 0.25 inch around adjacent batteries. Series adds voltage and keeps capacity the same. Parallel adds capacity and keeps voltage the same. Use batteries of the same size and condition. The FAQ repeats the sealed-container prohibition: during storage, charging, or discharging, hydrogen gas can be released and must be ventilated to prevent the possibility of ignition and/or explosion.

A common mistake

Reading 70 and reaching for a foot-pound wrench. Seventy foot-pounds is the wrong unit and far above 70 inch-pounds. The other mix-up is treating the lithium “once per year” individual charge as an AGM instruction, or treating Lifeline’s 90-day boost as a lithium instruction. Lifeline storage says to boost every 90 days, or when a 12 V battery’s open-circuit voltage drops to 12.5 V, which the manual calls about 75% state of charge. The boost charger in that section is 14.4 to 15.0 V for a 12 V battery, held until current falls below 0.5% of the 20-hour rating (0.5 A for a 100 Ah battery). A lithium charger left at 14.2–14.6 V with equalization off is a different profile, on the lithium charger page.

Limits, and when to call a pro

Stop if you see cracked cases, displaced electrolyte, or a compartment you cannot ventilate. Section 6.2’s instruction if electrolyte is on you is to flush with water and call a physician immediately, not to finish the torque. A bank inside a living space, an engine room, or a code-required enclosure needs someone who can size ventilation and fault current. This page does not assign fuse amps or cable gauges. The lithium manual points at its own cable chart and at ANL fuses without printing an amp value in the fuse paragraph. For a 1,000 W inverter on one of these lithium batteries, the bank-size rule is a different page: what size battery bank for a 1000W inverter.

Ah calculator

Torque does not change amp-hours. The form only runs the site formula so the terminal count has a bank behind it.

The battery bank calculator is the full table. AGM charge voltage and the 105 Ah model count stay on the AGM guide.

Sources

Compiled with AI assistance from the sources below. Spot an error? Email jpanasuk@gmail.com.