Battery Equivalents and Replacements

Optima Batteries 8020-164 35 RedTop Starting Battery

Optima 35 RedTop is very popular and lightweight AGM starting battery featuring rather specific 'spiral-wound' cells technology, ensuring high vibration resistance, spill proof design, faster recharging, high CCA and MCA etc.

Optima 35 RedTop is used in cars, RVs, trucks, boats etc as strong and reliable starting battery. Despite having excellent RC value for the battery of this capacity, it should not be used in deep cycle applications.

Updated: April 27, 2021.

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Optima 35 RedTop Features and Specifications

Optima 35 RedTop is AGM (Absorbent Glass Mat) SLA (Sealed Lead Acid) starting battery, designed to provide large bursts of energy for short periods of time. Thus, it should be used as starting battery only.

Optima 35 RedTop weighs 31.7 pounds (~14.4 kg) and is one of the lightest lead-acid BCI Group 35 batteries, with only lithium batteries featuring less weight.

Its physical dimensions are (L x W x H) 9.38 x 6.75 x 7.69 inches (~23.8 x 17.1 x 19.5 cm) and is defined as 'Group 35' battery, although it is slightly longer than standard Group 35 battery (L x W x H - 9.0625 x 6.875 x 8.875 inches, 23.0 x 17.5 x 22.5 cm).

In most cases this difference of ~0.3 inches (~0.8 cm) is negligible, but have this in mind when ordering this battery - for short, measure your battery compartment first.

Optima 35 RedTop is maintenance-free battery featuring SAE terminal posts and polypropylene case. Case color is dark gray, with the red cover color - hence the name.

optima d27 m f mNote: Optima RedTop batteries are starting automotive batteries, Optima YellowTop batteries are dual purpose automotive batteries, Optima BlueTop batteries with dark gray case are marine starting batteries and Optima BlueTop batteries with light gray case are marine dual purpose batteries.

Optima 35 RedTop features nominal capacity of 44 Ah and nominal voltage of 12 volts.

Recommended voltage for all Optima RedTop batteries and for BlueTop 34M (also starting battery) is 12.6 to 12.8 which is slightly lower than the recommended voltage for Optima YellowTop batteries and the dual purpose Optima BlueTop batteries of 13.3 - 13.2 volts.

Optima 35 RedTop features very low internal resistance of 3 mΩ, ensuring high CCA and MCA values - 720 CCA Amps and 910 MCA Amps.

Also, it features 90 minutes RC (Reserve Capacity) value, which is excellent value for 44 Ah battery. But, don't forget that this battery is not intended for deep cycle applications and such use may significantly shorten the battery's operating life.

When compared with other Group 35 batteries, Optima 35 RedTop features low weight, excellent starting features, and good RC, but since it is so lightweight, its 20h capacity is relatively low.


Battery Type

Battery Chemistry





Weight (lbs/kg)


Arc-Angel Group 35







16 lbs; 7.3 kg


Delphi BU9035

Dual Purpose






40 lbs; 18.1 kg


DieHard 38275

Dual Purpose






42 lbs; 19.0 kg


NorthStar NSB-AGM35

Dual Purpose






49 lbs; 22.2 kg


Optima 8020-164 35 RedTop







31.7 lbs; 14.4 kg


Optima 8040-218 35 YellowTop

Dual Purpose






36.4 lbs; 16.5 kg


Odyssey 35-PC1400T

Dual Purpose






50 lbs; 22.7 kg


Note: Amazon links in the table open in the new windows ('Model' column), feel free to check them for most up-to-date prices and offers.

Since it is optimized for starting/cranking applications, Optima 35 RedTop also features rather acceptable price, when being compared with other Group 35 batteries.

The following chart lists the most popular group 35 battery prices, with the batteries being ordered alphabetically from the left to the right:

As one can see, battery features are more or less evenly matched with the battery prices.

Features of the batteries in the table are evenly matched with their prices - dual purpose batteries must be able to provide large starting currents and to be able to withstand deep cycle operations. Thus, they are heavier, have larger 20h capacity and have better RC values.

Note: when the car's engine is turned OFF and the car is locked with alarm system ON, battery drain should be in 10-25 mA range. If the battery drain is 50-100 mAh or even larger, there is something wrong with the car's onboard electric/electronic systems, which must be checked as soon as possible - 25 mA current drains 0.6 Ah per day from the battery, while 100 mA current drains 2.4 Ah per day and can discharge the battery relatively quickly.

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How to Charge Optima 35 RedTop Battery

Depending on its use, Optima 35 RedTop should be charged (according to the manufacturer):

- in the vehicle or boat by the onboard alternator,

- by battery charger: 13.8 - 15.0 volts, 10 Amps max, 6-12 hours,

- rapid charge: maximum voltage of 15.6 volts with no current limit as long as the battery temperature is below 125°F (~52°C),

- float charge: 13.2 - 13.8 volts with the maximum current of one Amp.

Personally, if the battery is in the car or on the boat with acceptable 'parasitic' loads, let the alternator charge the battery. If the battery must be recharged with the battery chargers, use Optima Digital 400 (max charging current of 4 Amps) and Optima Digital 1200 (max charging current of 12 Amps).

Both units are intelligent battery chargers designed to charge starting, dual purpose and deep cycle AGM and other lead-acid batteries, they can recharge even deeply discharge batteries and they also can be used as battery maintainers.

For more info about these chargers, feel free to check Optima Digital 400 and Optima Digital 1200 Amazon links (links open in the new windows).

optima redtop 35 mLong Story Short: If you are looking for a good and reliable Group 35 starting battery, consider Optima 35 RedTop battery.

It is lightweight, maintenance free battery, it can be operated in any position, comes with 36 months limited warranty and has been used and tested in countless real-life situations.

For more reviews and recommendations, feel free to check Optima Batteries 8020-164 35 RedTop Starting Battery Amazon link (link opens in the new window).

Amazon Search:

- Car Battery

- Car Battery Charger

- Car Battery Tester

Note: Amazon links open in the new windows, feel free to check them for the most up-to-date offers and prices.