BCI Group 4D, 6D, and 8D Batteries

BCI Group 4D, 6D, and 8D batteries are large and heavy, but also rather powerful batteries that are able to store large amounts of energy and are thus often used in high-demanding applications including off-the-grid systems, backup units for security and medical devices, electric carts and vehicles, as high-capacity electric trolling motor batteries, as RV house batteries, etc.

BCI Group 4D, 6D, and 8D batteries feature the same length, very similar height, but they differ in width. However, some manufacturers label their batteries as, for example, '4D' batteries although their batteries belong to '6D' batteries and similar. That is the reason one should always check the battery's actual size, not just the BCI battery group.

Updated: September 10, 2020.

Features and Specifications

Physical dimensions of BCI Group 4D, 6D, and 8D batteries differ and thus, their performances also differ. Physical dimensions are given in the following list:

- BCI Group 4D: 20.75 x 8.75 x 9.875 inches (527 x 222 x 250 mm),

- BCI Group 6D: 20.75 x 10 x 10.25 inches (527 x 254 x 260 mm),

- BCI Group 8D: 20.75 x 11.125 x 9.875 inches (527 x 283 x 250 mm).

The most popular BCI group of these groups is '4D' and then '8D'. BCI Group 6D is not very common, at least not officially, since it is rather hard to find battery labeled as '6D' battery.

But, very often batteries that are labeled as '4D' have physical dimensions (width!) that are very close to '6D', making them too large to be considered '4D' batteries.

The most popular 4D, 6D and 8D batteries are given in the following comparison chart:

Model	Battery Type	Chemistry	Ah	CCA	MCA	RC	Weight (lbs/kg)	Dimensions (LxWxH, inches)	Review
AIMS Power LFP12V200A	Deep Cycle	LiFePO4	200 (2h)	-	-	~480	68.8 lbs; 31.1 kg	19.38 x 10.5 x 8.75	-
Concorde PVX-2580L	Deep Cycle	AGM	258	-	-	480 (@29.5 Amps)	159 lbs; 72.1 kg	20.76 x 10.22 x 9.77	-
Deka 8A4D	Deep Cycle	AGM	198	1110	-	380	129 lbs; 58.5 kg	20.75 x 8.5 x 10	-
Deka 8G4D	Deep Cycle	Gel	183	970	-	395	127 lbs; 57.6 kg	20.75 x 8.5 x 10	-
Deka 8A8D	Deep Cycle	AGM	245	1450	-	517	158 lbs; 71.6 kg	20.75 x 11 x 10	-
Deka 8G8D	Deep Cycle	Gel	225	1150	1470	500	157 lbs; 71.2 kg	20.75 x 11 x 10
ExpertPower EXP122000	Deep Cycle	AGM	220	-	-	600 (@20 Amps)	132.3 lbs; ~60 kg	20.59 x 9.44 x 8.62	-
Fullriver DC260-12	Deep Cycle	AGM	260	1525	1830	578	170.6 lbs; ~77 kg	20.51 x 10.59 x 8.82	-
GreenLiFE GL260	Deep Cycle	LiFePO4	260	-	-	624	80 lbs; 36.24 kg	20.44 x 10.57 x 8.7	-
LifeLine GPL-4DL	Deep Cycle	AGM	210	1100	1360	390	124 lbs; 56.2 kg	20.76 x 8.7 x 8.64	-
Lifeline GPL-8DL	Deep Cycle	AGM	255	1350	1675	550	156 lbs; 70.8 kg	20.76 x 10.89 x 9.65	-
Mighty Max ML4D	Deep Cycle	AGM	200	-	-	~360	114.6 lbs; ~52 kg	20.9 x 8.23 x 8.46	Mighty Max ML4D
Mighty Max ML8D	Deep Cycle	AGM	250	-	-	600 (@24.5 Amps)	159 lbs; 72.0 kg	20.47 x 10.55 x 8.66	-
NorthStar NSB-AGM8D	Dual Purpose	AGM	220	1450	1800	500	152 lbs; 68.9 kg	20.36 x 10.84 x 9.61	-
NorthStar SMS-AGM8DK	Dual Purpose	AGM	228	2250	2700	500	187 lbs; 84.7 kg	20.5 x 11.0 x 9.41	-
Odyssey 8D-1500	Deep Cycle	AGM	220	1500	1787	475	143 lbs; 64.8 kg	20.39 x 10.87 x 8.86	-
PowerStar PS200-12	Deep Cycle	AGM	200	-	-	-	135 lbs; 61.2 kg	20.55 x 9.37 x 8.58	-
Renogy RNG-BATT-AGM12-200	Deep Cycle	AGM	200	-	-	~600 (@20 Amps)	129 lbs; 58.5 kg	20.50 x 9.4 x 9.4	-
Renogy RNG-BATT-GEL12-200	Deep Cycle	Gel	200	-	-	~600 (@20 Amps)	128 lbs; ~ 58 kg	20.60 x 9.5 x 8.7	-
Renogy RBT200GEL12-G1	Deep Cycle	Gel	200	-	-	~600 (@20 Amps)	127.9 lbs; ~58 kg	20.6 x 9.4 x 8.8	Renogy RBT200GEL12-G1
Trojan 8D-AGM	Dual Purpose	AGM	230	1450	1850	460	161 lbs; 73 kg	20.47 x 10.64 x 9.08	-
Trojan 8D-Gel	Deep-Cycle	Gel	225	-	-	500	168 lbs; 76 kg	20.69 x 10.95 x 10.82	-
UPG UB4D-AGM	Deep Cycle	AGM	200	-	-	~600 (@20 Amps)	114.6 lbs; ~52 kg	21.0 x 8.15 x 8.47	-
UPG UB4D-Gel	Deep Cycle	Gel	180	-	-	300+	114.6 lbs; ~52 kg	20.87 x 8.11 x 8.43	-
UPG UB8D	Deep Cycle	AGM	250	-	-	600 (@23.2 Amps)	154 lbs; 70 kg	20.47 x 10.55 x 9.65	-
VMAXTANKS MB197-200	Deep Cycle	AGM	200	-	-	450	112 lbs; ~51 kg	19.1 x 6.8 x 9.5	-
VMAXTANKS MR197-200	Deep Cycle	AGM	200	-	1400	450	112 lbs; ~51 kg	19.1 x 6.8 x 9.5	-
VMAXTANKS XTR4D-200	Dual Purpose	AGM	200	1250	1670	470	130 lbs; ~59 kg	20.8 x 8.7 x 9.0	-
VMAXTANKS XTR8D-350	Deep Cycle	AGM	350	1700	2100	780	185 lbs; 83.8 kg	20.8 x 11.1 x 9.8	-
West Marine WM8A4D	Dual Purpose	AGM	198	1110	1420	380	131 lbs; 59.4 kg	20.75 x 8.5 x 10.0	-
West Marine WM8A8D	Dual Purpose	AGM	245	1450	1800	480	161 lbs; 73 kg	20.75 x 11 x 10.0	-

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BCI Group 4D, 6D and 8D batteries are large batteries - even 'deep cycle' models are able to provide large starting currents, with 'official' 'dual-purpose' models having CCA ratings of 1500 and more Amps.

However, many models are designed exclusively for deep discharge cycle operations and should not be used as starting/cranking batteries, except for small internal combustion engines found on generators and similar, with starting currents of just a few hundred Amps.

Wet/Flooded vs. Gel vs. AGM vs. Lithium BCI Group 4D, 6D and 8D Batteries

Wet/flooded batteries are maintenance intensive batteries are rarely used these days. They can be found at shore/land permanent installations as part of large backup battery packs.

Gel batteries are spill-proof, maintenance-free batteries that often feature relatively small charging and discharging currents, but are able to withstand a large number of charging/discharging cycles. As such, Gel batteries are commonly used in off-the-grid applications charged by solar panels during the day, and providing power during the night.

AGM (Absorbent Glass Mat) batteries are also spill-proof, maintenance-free batteries that may be discharged and recharged with stronger currents than gel-cell batteries. As such, AGM batteries are often used as industrial batteries, vehicle batteries, UPS batteries, and similar.

Lithium batteries cost several times more than lead-acid batteries, but they are 2-4 times lighter and can withstand 10-15 times more charging/discharging cycles. Although their initial investment is larger, they are more cost-effective in the long run.

Note: when connecting wet/flooded, gel-cell, or AGM batteries in series and/or parallel, it is highly recommended to use not only the same batteries (size, capacity, chemistry), but the same batteries of the same manufacturer, from the same batch, in order to avoid imbalances. On the other hand, lithium-ion batteries feature BMS (Battery Management System) that monitors the battery and protects it from unwanted events (overcharging, over-discharging, short-circuit, etc.). Thus, every lithium battery features different BMS system and before even considering connecting them in parallel and/or series, check with their manufacturer if connection like that is supported.

How to Charge BCI 4D, 6D and 8D Batteries?

Due to their capacity, these batteries can be safely charged with 30 Amps chargers, with larger models being able to accept 50 Amps easily.

If the batteries are charged individually, the best practice is to have single, dedicated smart/intelligent battery charger/maintainer - such chargers support charging modes for flooded/wet cells, Gel-cells, AGM, and even lithium batteries.

The charging cycle of smart battery chargers starts with battery analysis, after which the battery charger starts with the charging process according to the current battery condition and ends with cell equalization mode and with maintenance mode.

Solar panels and wind turbines should be connected to MPPT charge controller, ensuring proper charging even when the sun and wind conditions are far from ideal.

In single battery marine and automotive systems (boats, cars, trucks, RVs, etc.) where 4D, 6D and 8D batteries are used as both deep discharge and starting batteries, the battery should be recharged via an onboard alternator and its control electronics.

Note: in single battery systems, there is always a danger of discharging the battery too low in order for the battery to crank the main engine safely. Personally, if you have such a system, don't discharge your battery below 50% DoD and if possible, always have lithium jump-starter fully charged and ready to be used ...

In two battery marine and automotive systems (boats, cars, trucks, RVs, etc.) where 4D, 6D and 8D batteries are used only as deep discharge batteries, the battery should be recharged via an onboard alternator and its control electronics.

Some boats and vehicles have a central MPPT charge controller with connectors for an alternator, solar panels, and wind turbines (as input) and the battery connectors (as output).

BCI Group 4D, 6D and 8D Batteries As Trolling Motor Batteries

BCI Group 4D, 6D and 8D batteries are excellent electric trolling motor batteries, except one thing - their weight.

The maximum current of modern trolling motors is limited to 60 Amps per battery at full throttle. Most of the BCI Group 4D, 6D and 8D batteries are able to provide 60 Amps for at least 2h 30min.

When the electric trolling motor is throttled down, on average its current drops to half, or even less than half.

Most of the BCI Group 4D, 6D and 8D batteries feature Reserve Capacity (25 Amps) of at least 300 minutes (5 hours), with some models (like VMAXTANKS XTR8D-350) featuring RC value of 780 minutes (13 hours!).

However, AGM and Gel-cell batteries are heavy - if your boat is large enough to accept a battery (or batteries) of this size, then place it low in the boat (below the waterline) and it will even increase the boat's stability.

For applications where such a weight penalty is simply unacceptable, lithium batteries are the way to go - lithium batteries initially cost more, but they don't lose capacity as much as lead-acid batteries when the discharging currents are increased, they are 2-4x lighter and can withstand 10-15x more charging/discharging cycles.

Note: lithium batteries should be recharged as recommended by their manufacturer - most models can safely be recharged with advanced AGM battery chargers using charging mode specifically intended for lithium batteries.

BCI Group 24 vs BCI Group 8D

BCI Group 24 is a very popular group of automotive, industrial, and marine batteries, with physical dimensions (L x W x H) of 10.25 x 6.8125 x 8.875 inches (260 x 173 x 225 mm).

BCI Group 8D physical dimensions (L x W x H) are 20.75 x 11.125 x 9.875 inches (527 x 283 x 250 mm), allowing three BCI Group 24 batteries to fit into the battery compartment intended for Group 8D battery.

Since group 24 batteries also feature starting batteries, such a battery pack of 3 starting or 3 dual-purpose batteries may have excellent cranking/starting characteristics.

NorthStar Battery even manufactures a battery pack like that one: NorthStar SMS-AGM8DK battery, which consists of three group 24 batteries and is delivered as a disassembled battery pack, allowing the user to assemble the battery pack directly in the battery compartment, which can be very helpful when replacing the battery in tight areas.

NorthStar SMS-AGM8DK battery is the heaviest battery in our comparison chart, and it is even heavier than VMAXTANKS XTR8D-350 battery (187 vs 185 pounds).

But, NorthStar SMS-AGM8DK battery features internal resistance of only 1.5 mΩ, 2250 CCA Amps, 2700 MCA Amps, 3125 PHCA Amps (seconds?), and 228 Ah 20h capacity.

Also, it comes with a 3 year warranty.

NorthStar SMS-AGM8DK battery is anything but cheap battery - for industrial and similar applications requiring a premium battery, it simply outperforms all other batteries.

Long Story Short: BCI Group 4D, 6D and 8D batteries store large amounts of energy and are used everywhere where that energy is required.

Before getting a new battery, always check the actual battery compartment size and the battery size - better safe than sorry.

Which BCI Group 4D, 6D and 8D battery is the best one? Well, batteries should be chosen according to the individual needs and requirements, but also budget.

Whatever you do, stay safe - these are large units and if misused (short circuit, for example), they can make a lot of damage and even injure (or worse) people, kids, pets ...