8 Volt Tractor Battery - The Complete Guide

8-volt tractor batteries are starting batteries and should not be confused with 8V deep-cycle batteries, which are typically used in golf carts and similar electric vehicles for creating battery packs of 24V and 48V.

8V cranking batteries are not as common as 12V Group U1 and Group 22NF batteries or 6V Group 1 batteries, but they are still present in some vehicles, and as such, they are also available on the market.

Published: January 4, 2023.

8 Volt Tractor Batteries Features and Specifications

8V tractor batteries are often said that they belong to the BCI Group 1, which are passenger car and light commercial 6-volt batteries with physical dimensions of (L x W x H) 9 1/8 x 7 1/8 x 9 3/8 inches (9.125 x 7.125 x 9.375 inches, 232 x 181 x 238 mm).

8-volt tractor batteries are of the same dimensions, but they are not 6V, but 8V batteries and are often labeled as "8V-1 battery" or "1-8V battery", sometimes with prefixes like "HD" (Heavy Duty), "SLI" (Starting, Lighting, Ignition), and similar.

8V tractor batteries should not be confused with 8V deep cycle batteries, which have different dimensions:

• 8 Volts Group GC8: 10 3/8 x 7 3/16 x 10 7/8 inches (264 x 183 x 277 mm), deep cycle batteries,
• 8 Volts Group GC8H: 10 3/8 x 7 3/16 x 11 5/8 inches (264 x 183 x 295 mm), deep cycle batteries,
• 8 Volts Group 1-8V: 9 1/8 x 7 1/8 x 9 3/8 inches (232 x 181 x 238 mm), starting/cranking batteries.

As one can see, these three battery groups differ in length and height significantly, while their width is very similar. But they also differ in their intended use.

8V tractor batteries are almost exclusively wet/flooded lead-acid batteries, with a positive terminal on the right side of the battery.

Since they are wet batteries, they are not maintenance-free and not spill-proof batteries, and as such, they must be operated in an upright position.

Also, occasionally it is up to the user to check the electrolyte level and to add some distilled water if required.

Note: it is good practice to check the electrolyte level every 2-6 months, more often during warm months and during periods of intensive tractor use.

Lithium 8V Tractor Batteries

Lithium 8V tractor batteries are not present for a very simple reason - batteries based on lithium chemistry cannot be made to have 8V.

The nominal voltage of lithium battery cells ranges from 3.2 to 3.7V, thus lithium batteries can provide:

• 2S 3.2V: 6.4V,
• 3S 3.2V: 9.6V,
• 2S 3.7V: 7.4V,
• 3S 3.7V: 11.1V

So, if we connect two cells in series, we get 6.4V-7.4V, which is too low voltage, and the engine will not start, or it will be a very lazy start.

If we connect three cells in series, we get 9.6V-11.1V, which is a too high voltage that could damage the starter, its solenoid, and who knows what else...

Thus, lithium 8V tractor batteries do not exist as such.

Examples of 1-8V Group Tractor Batteries

Here are a few examples of 1-8V group batteries used as cranking batteries in tractors and other similar applications. Batteries are ordered alphabetically.

Deka 801 8V Flooded Battery

Deka 801 battery is an 8V cranking battery with physical dimensions of (L x W x H) 8.86 x 6.73 x 8.86 inches (225 x 171 x 225 mm), and it weighs 31.5 pounds (~14.3 kg).

The battery is a typical 8V wet lead-acid battery consisting of 4 cells connected in series.

Since it is wet/flooded, it is up to the user to periodically check the electrolyte levels in the cells.

Deka 801 battery features 520 Amps CCA and 650 Amps CA rating, ensuring reliable cranking of smaller gasoline and even diesel engines.

Reserve capacity is 102 minutes - the battery can provide 25 Amps for up to 102 minutes, after which it must be recharged immediately.

Despite having a very good RC value, the battery is designed as starting battery and should be used as such.

Duracell Ultra SLI1-8V Flooded Battery

Duracell Ultra SLI1-8V battery features physical dimensions of (L x W x H) 8.875 x 6.75 x 8.875 inches (225 x 171 x 225 mm), and it also weighs 31.5 pounds (~14.3 kg).

As its label suggests, the Duracell Ultra SLI1-8V is a wet/flooded lead-acid battery with 520 Amps CCA and 640 Amps CA rating, ensuring reliable starting/cranking even in unfavorable conditions.

However, for the battery to function properly, the user must regularly check the battery fluid level, and the battery must be kept charged, even in the periods when the tractor is stored for weeks and even months.

How To Charge 1-8V Batteries

When the batteries are connected to the electrical system of the tractor or some other vehicle, and if the alternator and charge controller are present, let the vehicle keep the battery fully charged.

If the battery is going to be recharged in the garage, one should use a 5-8 Amps 8V advanced lead-acid battery charger with a temperature sensor.

When the battery is fully recharged, the battery charger should automatically switch to maintenance mode, keeping the battery fully charged, even if the battery is stored for months.

Note: if You are storing the tractor for weeks or even months, it is a good idea to connect the battery to the battery maintainer to keep it fully charged while the tractor is not being used. Of course, in such situation, a much cheaper unit can be used to keep the battery fully charged.

6V Tractor Batteries vs. 8V Tractor Batteries

6V batteries that belong to the BCI Group 1 feature better CCA and CA ratings than 8V batteries of the same dimensions, thanks to the larger individual cells.

However, if one replaces the 8V battery with a 6V battery, even with one with better CCA and CA ratings, actual cranking performances will suffer due to the lower voltage required to "force" the current through the wires.

For example, if the 8V battery provided 320 Amps when starting, the 6V battery would provide 240 Amps, which is 25% less.

Note: this is just an approximation used as an example.

Now, will 240 Amps be enough when 320 Amps are required for reliable starting is rather questionable.

Not to say that if You replace the 8V battery with a 6V battery, You will also have to replace the battery charge controller in order to charge the 6V battery properly. Also, You will have to replace all the 8V light bulbs with 6V light bulbs and replace all the 8V instruments and other loads with 6V ones.

Similarly, if You replace the 6V battery with an 8V battery, the cranking should theoretically be improved, but don't forget that too much current can damage the starter and other parts of the electrical system - they all have to be replaced with the battery replacement.

For short, don't replace an 8V battery with a 6V battery, and don't replace a 6V battery with an 8V battery, simple as that.

Long Story Short: 8V tractor batteries are starting batteries, and they are not intended for cycling use.

Since they are flooded/wet batteries, they should be used in an upright position with their battery liquids being regularly checked.

When being stored for longer, these batteries should be connected to intelligent battery maintainers that will keep the batteries charged even for months to come ...