The MK Battery 8G31DT is a 12-volt, 97.6Ah (20-hour rate) BCI Group 31 sealed gel deep cycle battery with dual terminals: an SAE automotive post plus a 5/16" stainless steel stud on each polarity. It is a valve-regulated, non-spillable, maintenance-free battery built in the USA by East Penn Manufacturing and sold under the MK Battery brand. Typical uses include backup and off-grid power at communications and repeater sites, solar and renewable energy storage, marine house banks, RV coach batteries, and floor cleaning equipment.
MK 8G31DT Key Specifications
| Part Number | 8G31DT (also labeled 8G31DT-DEKA) |
| Manufacturer | MK Battery (East Penn Manufacturing Co., Inc.) |
| Chemistry | Valve-regulated lead acid (VRLA), gelled electrolyte (sulfuric acid thixotropic gel) |
| Nominal Voltage | 12V |
| Nominal Capacity, 20-hr rate | 97.6Ah |
| Nominal Capacity, 5-hr rate | 80.5Ah |
| Capacity, 100-hr rate | 108Ah |
| Peak Capacity, 20-hr / 5-hr | 102Ah / 85.0Ah |
| Reserve Minutes @ 25A | 190 |
| Reserve Minutes @ 75A | 51 |
| Cranking Amps @ 32°F | 780 CA |
| BCI Group Size | 31 |
| Terminals | Dual terminal (DT): SAE post plus vertical 5/16" stainless steel stud with wing nut, positive and negative |
| Length | 12.93 in (328 mm) |
| Width | 6.74 in (171 mm) |
| Height (including terminals) | 9.40 in (239 mm) |
| Weight | 68.5 lb (31 kg) |
| Handle | Yes |
| Plate Alloy | Lead calcium |
| Posts | Forged terminals and bushings |
| Container / Cover | Polypropylene |
| Vent | Self-sealing |
| Operating Temperature | -76°F to 140°F (-60°C to 60°C) |
| Charge (Cycle / Absorption) Voltage @ 77°F | 13.8 to 14.6V |
| Float Voltage @ 77°F | 13.5V ±0.5% |
| Self-Discharge | Less than 2% per month |
| Shipping Classification | Non-spillable per DOT, ICAO, and IATA |
| Country of Origin | Made in USA with U.S. and imported raw materials |
Ampere-hour ratings are nominal, measured to 1.75 volts per cell at 77°F (25°C) after 15 cycles per BCI specifications. Peak rating is the maximum capacity the battery achieves over its service life.
What Makes the 8G31DT Different
- Genuine gel, not AGM. The electrolyte is immobilized in a thick gel, so there is nothing to spill, stratify, or dry out. Gel holds up better than AGM in deep-cycle duty, in hot enclosures, and in installations that go long stretches between full recharges.
- Dual terminals. Each post has both an SAE automotive post and a 5/16" stainless stud with wing nut. Use the post for vehicle-style clamps and the stud for ring lugs on inverter, charge controller, or DC distribution cabling. No adapters needed.
- Mount in any orientation. Sealed, valve-regulated construction with a self-sealing vent. Fits equipment bays, cabinets, and battery boxes where a flooded battery would be a maintenance and safety problem.
- Individual Plate Formation (IPF) technology. Each plate is formed individually for consistent voltage from cell to cell and battery to battery, which matters when you parallel or series batteries into a bank.
- Over 250 quality control checks during manufacture at East Penn.
- Ships without hazmat restrictions. Rated non-spillable by DOT, ICAO, and IATA, so it can move by ground or air without special containers.
Applications
- Backup and standby power for LMR repeater sites, base stations, and remote communications shelters
- Off-grid and solar-charged radio, telemetry, and SCADA sites
- Mobile command vehicles and communications trailers
- Marine house banks and trolling motor power
- RV coach and auxiliary batteries
- Floor scrubbers and sweepers
- UPS and inverter systems where a spill-proof deep cycle battery is required
Charging the MK 8G31DT
Gel batteries are less tolerant of overcharge than flooded or AGM batteries. Use a voltage-regulated charger or charge controller with a gel profile and confirm the settings below before connecting. Constant under- or over-charging shortens life and voids the MK warranty.
- Absorption / cycle charge: 13.8V minimum, 14.6V maximum at 77°F (25°C)
- Float / standby: 13.5V ±0.5% at 77°F (25°C)
- Temperature compensation: MK's temperature-compensated setpoints shift with battery temperature (for example, float drops to about 13.32V at or above 95°F). Use a charger with a temperature sensor if the battery will run above 77°F.
- Heat is the enemy: East Penn states that every 13°F (7°C) above 77°F reduces expected service life by roughly half. Keep the battery out of direct sun and ventilate the enclosure.
- Never charge in a sealed container. Do not remove or tamper with the vent valves.
Storage
Store between 50°F and 77°F where possible. Self-discharge is under 2% per month, but MK recommends a refresh charge at least every 6 months in storage. Do not store beyond 12 months without charging.
Compatibility and Cross Reference
The 8G31DT is a standard BCI Group 31 footprint and replaces most Group 31 flooded, AGM, or gel batteries in deep cycle or dual-purpose applications, provided the charging system is set to gel voltages. Related MK part numbers: 8G31 (same cell pack with a single 3/8"-16 threaded stud terminal) and 8G30H (flag terminal). The 8G31DT is also distributed as 8G31DT-DEKA.
Frequently Asked Questions
Is the MK 8G31DT 97.6Ah or 108Ah?
Both numbers are correct; they are different discharge rates. 97.6Ah is the industry-standard 20-hour rating and is the number to use when comparing against other Group 31 batteries. 108Ah is the 100-hour rating, which applies to very light, long-duration loads such as small solar or telemetry sites.
What does "DT" mean on the 8G31DT?
DT stands for Dual Terminal. Each polarity has an SAE post and a 5/16" stainless steel stud with wing nut, so the same battery accepts automotive clamps or ring-lug cables.
Is the 8G31DT gel or AGM?
Gel. It uses a thixotropic gelled electrolyte, not an absorbed glass mat. It must be charged with a gel charging profile (13.8 to 14.6V absorption, 13.5V float at 77°F).
Can I charge the 8G31DT with a standard automotive or AGM charger?
Only if the charger has a selectable gel mode or its output voltage falls within 13.8 to 14.6V and it floats at about 13.5V. Many AGM and flooded profiles push 14.7V or higher, which will overcharge and shorten the life of a gel battery.
Can the 8G31DT be mounted on its side?
Yes. It is a sealed, valve-regulated battery with immobilized electrolyte and can be installed in any orientation except inverted.
Does the 8G31DT ship as hazardous material?
No. It is rated non-spillable by DOT, ICAO, and IATA and ships as a standard ground parcel or freight item without hazmat surcharges.
Where is the MK 8G31DT made?
It is manufactured in the USA by East Penn Manufacturing Co., Inc. in Lyon Station, Pennsylvania, with U.S. and imported raw materials, and sold through MK Battery.
How long will the 8G31DT last?
Service life depends on depth of discharge, operating temperature, and charging accuracy. MK rates the dual-terminal 8G31DT at 0.67 times the cycle life of its standard single-terminal gel models, so for high-cycle-count duty the 8G31 may be the better choice; for float, standby, and moderate cycling the 8G31DT performs the same. Keep discharges shallow and the battery cool for the longest life.
California Proposition 65 Warning: Battery posts, terminals, and related accessories contain lead and lead compounds, chemicals known to the State of California to cause cancer and reproductive harm. Wash hands after handling.
