Battery Equivalents and Replacements

Optima Batteries 8071-167 D51 and 8073-167 D51R YellowTop Dual Purpose Batteries

Optima D51 and D51R YellowTop are two very similar dual-purpose automotive batteries. The only true difference between these two batteries is in the layout of their terminal posts: D51 has a positive post to the left, and D51R has its positive post to the right (hence the 'R' right after 'D51'); when looked from their front side.

Optima D51 and D51R YellowTop are recommended for vehicles with single-battery electrical systems requiring batteries that feature good starting characteristics but also can support a broad range of onboard electric and electronic devices like winches, alarms, audio systems, and similar.

Updated: January 8, 2024.

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Optima D51 and D51R YellowTop Features and Specifications

Optima D51 and D51R YellowTop belong to the BCI Group 51 and have physical dimensions of (W x L x H) 5.06 x 9.31 x 8.94 inches (~12.9 x 23.7 x 22.7 cm), and they weigh 26 pounds (~11.78 kg).

The case is made using polypropylene, leading to the reduced weight and sturdy casing.

Optima D51 and D51R YellowTop are high-performance, vibration-resistant, heavy-duty AGM (Absorbent Glass Mat) SLA (Sealed Lead Acid) batteries that can be mounted in virtually any position (except upside down) and are truly spill-proof, maintenance-free batteries.

Optima D51 and D51R YellowTop batteries are light-gray on the sides and feature a yellow top - hence the 'YellowTop' label.

Their nominal voltage is 12 volts, and their 20h capacity is 38 Ah - a new, fully charged battery is able to provide 1.9 Amps current for 20 hours when being discharged down to 10.5 volts at 77°F (25°C).

As typical automotive batteries, Optima D51 and D51R YellowTop batteries come with SAE posts (just different orientations - keep this in mind when ordering batteries for your vehicle!).

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Their Reserve Capacity is 66 minutes - a new, fully charged battery is able to provide 25 Amps for 66 minutes without the voltage dropping below 10.5 volts at 77°F (25°C).

Their CCA (Cold Cranking Amps) value is 450 Amps - a new, fully charged battery is able to provide 450 Amps for 30 seconds, with the voltage NOT dropping below 7.2V at 0°F (-18°C).

Their MCA (Marine Cranking Amps) or CA (Cranking Amps) value is 575 Amps - a new, fully charged battery is able to provide 575 Amps for 30 seconds, with the voltage NOT dropping below 7.2V at 32°F (0°C).

The manufacturer doesn't state their HCA (Hot Cranking Amps - maximum current that a new, fully charged, 12V battery (at 77°F; 25°C) can deliver for 30 seconds, with the voltage not dropping below 7.2V.), but using their CCA and MCA, one can calculate approximate HCA value:

HCA = CCA x 1.66 = 450 Amps x 1.66 = 747 Amps

HCA = MCA x 1.33 = 575 Amps x 1.33 = 765 Amps

So, the approximate HCA value of Optima D51 and D51R YellowTop batteries is ~750 Amps.

Optima D51 and D51R YellowTop batteries feature wound cell configuration utilizing Optima's proprietary SPIRALCELL technology and high purity lead grid - leading to a low discharge rate and low internal resistance, providing consistent power output.

Also, Optima D51 and D51R YellowTop tolerate 300+ charging/discharging cycles (down to 10.5 volts) and allow faster recharging.

For example, these batteries can be charged:

  • alternator: 13.65 to 15.0 volts,
  • battery charger (constant voltage): 13.8 to 15.0 volts (10 Amps max),
  • float charge: 13.2 - 13.8 volts
  • rapid recharge: 15.6 volts max. There is no current limit as long as the battery temperature remains below 125°F (~52°C) - charge until the current drops below 1 Amp.
  • cyclic applications: 14.7 volts max. There is no current limit as long as the battery temperature remains below 125°F (~52°C) - charge until the current drops below 1 Amp, and finish with 2 Amps constant current for 1 hour.

optima digital 400 vs 1200 1Personally, if you don't have these batteries mounted in your vehicles and charged via an onboard alternator, consider getting an intelligent AGM SLA battery charger - such chargers are able to test/analyze the battery and charge it according to its condition.

Recommended intelligent AGM SLA battery chargers are Optima Digital 400 and Optima Digital 1200 battery chargers and maintainers, which charge the batteries using six fully automatic charging modes.

According to the manufacturer, Optima D51R and D51R batteries can be quickly recharged, with recharge times (assuming 100% discharge - 10.5 volts, to 90% of charge) of:

  • 100 Amps charging current: ~25 minutes,
  • 50 Amps charging current: ~65 minutes,
  • 25 Amps charging current: 130 minutes.

Note: These are very high charging currents, and they are allowed only while monitoring the battery temperature. Personally, if You plan on charging these batteries regularly with battery chargers, go for either Optima Digital 400 (4 Amps Max.) or some similar 4-6 Amps intelligent AGM battery charger and keep the charging current in the 0.1-0.15C. Just my 2c.

Can You Recharge a Dead Optima Battery?

Dead batteries with voltages below 1V can be recharged using advanced battery chargers that will "force" the charge into the battery when "ordinary" chargers won't even try to charge such batteries because the voltage is so low that they can't even detect the battery.

However, one must note a few things:

  • never discharge the battery to such low voltage on purpose,
  • there is no warranty that such battery chargers can recover/save batteries discharged to 0-1V, even if those batteries are almost new.

One such battery charger is the NOCO GENIUS10 10A Smart Car Battery Charger (Amazon link, the link opens in the new window), which is able to charge 12V and 6V lead-acid batteries and 12V lithium batteries, can be used as a 12V power supply and can be used to recover deeply discharged car batteries.

But, one must be aware that no matter how good the charger is, there is no warranty that the battery discharged down to 0-1V will be saved...

 Optima D51 and D51R YellowTop Batteries as Trolling Motor Batteries

Although Optima D51 and D51R YellowTop batteries feature SAE terminal posts, it is not uncommon practice by many fishermen to take out the battery (this or any other battery) from their vehicle to use it as a trolling motor battery and then mount the battery back in the vehicle and use it to start the vehicle, as if nothing happened in the meantime.

First of all, Optima D51 and D51R YellowTop batteries can be used for deep cycle applications - as trolling motor batteries, too.

However, their starting characteristics decline as they are being discharged - for how much is NOT known as manufacturers (Optima Batteries included) don't state very often such data for their batteries.

Generally, if these batteries are not discharged below 70% SoC (30% DoD), they are, more or less fine. However, when discharging them below 50% SoC (50% DoD) and especially below 20-30% SoC (70-80% DoD), their CCA/MCA/HCA Amps tend to be significantly lower than CCA/MCA/HCA Amps of a fully charged batteries.

jump starter noco gb40So, if you like fishing using electric trolling motors in the wilderness, consider either getting a dedicated trolling motor battery or at least a good lithium jump starter, for example, NOCO Boost Plus GB40 UltraSafe Car Battery Jump Starter (Amazon link, the link opens in the new window).

A dedicated trolling motor battery (second Optima D51 is just fine if its capacity is large enough for your trolling motor) is IMHO better choice, but having a fully charged lithium jump starter gives the fishermen at least a chance to start the vehicle when the main battery is discharged - and any battery can be discharged during trolling since people often lose track of time and Amps!

If the battery is discharged and can't start the vehicle, jump-start the vehicle and let the vehicle's alternator charge the battery (and the jump starter) while driving.

Note: don't forget - safety first. Call me paranoid, but having a good jump starter when going on the fishing/hunting/camping trip is a smart and not-so-expensive backup option.

optima yellowtop d51 3Long Story Short: If you are looking for a BCI Group 51 battery for your vehicle, especially if it has various electric and electronic devices onboard, consider Optima D51 or Optima D51R YellowTop battery - just be aware of the terminal posts orientations.

Optima D51 and D51R YellowTop batteries are spill-proof, AGM dual-purpose batteries, highly resistant to vibrations, have good charging/discharging characteristics, and 450/575 Amps CCA/MCA.

For more reviews and recommendations, check Optima Batteries D51 YellowTop Dual Purpose Battery and Optima Batteries D51R YellowTop Dual Purpose Battery Amazon links (links open in the new windows).