Optima Batteries D27M BlueTop and D27F YellowTop Starting and Deep Cycle Batteries
Optima Batteries D27M BlueTop and D27F YellowTop Starting and Deep Cycle Batteries are versatile, dual-purpose marine and automotive batteries. Optima Batteries D27M BlueTop and D27F YellowTop are AGM (Absorbent Glass Mat) SLA (Sealed Lead Acid) batteries, with the spiral wound lead plates, offering good vibration resistance, extended life, low maintenance, and faster recharging.
Optima Batteries D27M BlueTop and D27F YellowTop are completely spill-proof 12V AGM batteries, mountable in virtually any position.
Updated: May 13, 2022.
Optima Batteries D27M BlueTop and D27F YellowTop - Features and Specifications
Optima Batteries D27M BlueTop and D27F YellowTop are BCI Group 27 batteries. Their nominal capacity is 66 Ah (20h capacity), with a reserve capacity (RC) of 140 minutes.
However, they also differ in a few important details. Optima Batteries D27M BlueTop is dual purpose battery intended for marine applications and D27F YellowTop is dual purpose battery intended for automotive applications. Their specifications are given in the following table:
| Model | Optima Batteries D27M BlueTop | Optima Batteries D27F YellowTop |
| BCI Group | 27 | 27 |
| Weight | 53.8 lbs (~24.4 kg) | 53.2 lbs (~24.1 kg) |
| 20h Capacity | 66 Ah | 66 Ah |
| Post Type | Dual SAE & 5/16 Stainless Stud | SAE Post |
| CCA | 800 Amps | 830 Amps |
| MCA | 1000 Amps | 1025 Amps |
| Dimensions (L x W x H) | 12.19 x 6.81 x 8.75 inches 31 x 17.3 x 22.2 cm |
12.16 x 6.76 x 8.61 inches 30.9 x 17.2 x 21.9 cm |
| Reserve Capacity (25A) | 140 minutes | 140 minutes |
| Internal Resistance | 2.5 mΩ | 2.5 mΩ |
| Amazon Link | Optima Batteries D27M BlueTop |
Optima Batterues D27F YellowTop |
Note: Amazon links in the table open in the new windows, feel free to check them for the most up-to-date offers and prices.
As one can see, the Optima D27F YellowTop battery is a slightly lighter battery, features 'only' SAE posts and is capable of providing slightly more CCA and MCA Amps.
The nominal capacity and reserve capacities of these two batteries are the same - 66 Ah and 140 minutes.
Since these are dual-purpose batteries, they provide fewer cranking amps than true starting batteries and feature shorter RC than true deep cycle batteries.
However, they provide much more cranking amps than deep cycle batteries and feature longer RC than starting batteries.
Also, they tolerate 300+ discharge/recharge cycles, especially when charged with Optima Digital chargers.
Optima Batteries D27M BlueTop and D27F YellowTop are intended for marine and automotive applications where they can be used as starting batteries and at the same time are able to provide power for electric and electronic devices like lights, onboard computers, GPS units, alarms, and similar.
With boats, yachts, cars, trucks, and similar vehicles having so many electronic devices that are slowly draining the main battery while the main engine is turned off, having a good and reliable dual purpose battery is becoming more and more important.
If your boat or vehicle has a dual battery system (one dedicated starting battery, another battery, or battery pack as a dedicated deep cycle battery), then consider getting batteries that are optimized for such purpose - personally, both Optima D27F and D27M can be used as compact and relatively lightweight starting batteries, and for a deep cycle battery pack, go for lithium batteries.
Optima Batteries D27M BlueTop and D27F YellowTop As Trolling Batteries
Optima Batteries D27M BlueTop and D27F YellowTop are very good choices as electric trolling motor batteries for smaller electric trolling motors.
Both batteries are able to provide 25 Amps for 140 minutes (2 hours and 20 minutes) - that is 58.33 Ah effectively, which is a good result for 66 Ah batteries.
However, stronger motors requiring 50 Amps or more, drain these batteries too fast, and getting larger, deep cycle batteries for such applications is recommended.
Optima Batteries D27M BlueTop and D27F YellowTop As Fish Finder Batteries
Most onboard fish finders require less than 2 Amps when operating at full power. Since both D27M and D27F can provide 2 Amps for 33+ hours easily, they are a very good choice as fish finder batteries for situations where the main boat engine is going to be offline for hours.
And if the boat has solar panels and a wind turbine installed, such a setup can power a fish finder, navigational lights, and a few more devices almost indefinitely.
Optima Batteries D27M BlueTop and D27F YellowTop As Starting Batteries
Optima Batteries D27M BlueTop can provide 800 CCA and 1000 MCA, while Optima Batteries D27F YellowTop can provide slightly more amps: 830 CCA and 1025 MCA.
Both batteries are practically the same internally (spiral wound cells), but they have different posts and thus internal connections are somewhat different.
Either way, both batteries can provide strong currents that can start large internal combustion engines, even at low temperatures.
How to Charge Optima Batteries D27M BlueTop and D27F YellowTop
When they are mounted in the boat or vehicle, these batteries are charged like any other boat/vehicle lead-acid battery via an onboard generator/alternator powered by the main engine or using solar panels/wind turbine chargers/controllers.
When being charged via mains power, both D27M and D27F batteries can be charged using ordinary lead-acid battery chargers, preferably chargers designed for AGM batteries.
The best results are obtained using Optima Digital 400 and 1200 intelligent AGM chargers that first test the battery condition and then charge the batteries in several steps.
Also, these chargers employ simple, single-button controls, allowing the users to charge different types of batteries in an optimal way.
The most important difference between these chargers is the maximum charging current - Optima Digital 400 charger features 4 Amps max. charging current, while Optima Digital 1200 charger features 12 Amps max. charging current.
Although both Optima D27M and D27F accept the charge very well, charging them regularly with 12A might be too much for them, especially during hot summer weather - if You are not in a hurry and You don't discharge your Optima batteries more than 50% DoD, a 4 Amps battery charger can recharge them easily over the night.
For more information about these chargers, please check Optima Digital 400 12V Performance Maintainer and Battery Charger
Of course, these are not the only AGM battery chargers suitable for these batteries - any advanced AGM battery charger with a not too strong current that allows the users to set the battery type and chemistry will do fine.
Such battery chargers analyze the battery first and then charge it according to the battery's condition. After recharging the battery, they automatically stop the charging and switch to the maintenance mode. Also, if they detect sulphation issues with the battery, they will automatically try to desulphate the battery.
Of course, not all AGM battery chargers come with these features, so be sure to choose wisely.
Long Story Short: Optima Batteries D27M BlueTop and D27F YellowTop are versatile and durable, dual-purpose batteries. They are an excellent choice for single-battery electric systems commonly found in cars and boats and for outdoor applications where the type of load is not always known in advance.
Also, Optima Batteries D27M BlueTop and D27F YellowTop come with a 2-year limited warranty.
Note that there are cheaper batteries in this class, but what you pay is what you get - Optima batteries are very popular batteries that will not let the user down, if and when used for what are they designed to.
For more reviews and recommendations, check Optima Batteries D27M BlueTop