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Battery Recommendations

Posted: Wed Jul 03, 2019 3:55 pm
by jimh

Below is a link to a lead-acid AGM battery using ultra-high-purity lead that appears to be suitable for use as a starting battery for almost any outboard engine:

X2Power Premium AGM Dual Purpose (Starting/Cycling) Battery for Starting BCI Group 34M Marine and Boat ... li34agmdpm

The basis for this recommendation:
  • the ultra-high-purity lead in the lead-acid battery creates very low self-discharge rates. This is a useful feature for boats that are used on a seasonal basis and left in storage for long periods.
  • the AGM construction gives flexibility in installation; you do not really need a battery box enclosure. The AGM construction is also resilient to vibration and motion.
  • the AGM construction also allows the battery to be shipped to the retailer with the electrolyte in place, which greatly simplifies distribution into the retail channel from the manufacturer. Flooded cell batteries are generally only transported a short distance from the manufacturer's distribution site where the electrolyte is added, to the retailer, and the carrier is usually a special truck owned by the battery manufacturer.
The ratings for the X2Power Premium AGM Dual Purpose (Starting/Cycling) Battery for Starting BCI Group 34M Marine and Boat battery are very good:

CCA = 880
MCA = 1050
Category = SLI or Starting, Lighting, and Ignition
Warranty Free Replacement = 48-months

This battery is priced at $304, but you can get a 10-percent discount coupon for web-order and store delivery purchase. That moves the price down to about $270. There is also a $20 mail-in rebate.

This battery should provide a ten-year service life in outboard engine starting use for a typical boater. The recommended vendor is just the retailer, but they have nationwide stores and should be available almost anywhere. This battery is probably made Northstar. See

A similar battery was sold by Sears for many years and was made by Odyssey. A 34M battery will fit into a standard battery box.

There is a similar X2 battery in the 24M case; this battery will fit into the traditional battery boxes, particularly the ones provided as accessories on classic Boston Whaler boats.

X2Power Premium AGM Dual Purpose (Starting/Cycling) Battery for Starting BCI Group 24M Marine and Boat

Both batteries have a 48-month free replacement warranty. Here is a comparison of some data between the 34M and 24M models:

MODEL  CCA  MCA  RC  AH   LBS  L      W     H      PRICE
34M 880 1050 133 65 50.6 10.87 6.99 7.76 $305
24M 840 1010 160 76 57.7 10.87 6.57 8.75 $325

CCA = cold cranking Amperes measured at 0-degrees-F
MCA = marine cranking Amperes measured at 32-degrees-F
RC = reserve capacity; minutes at 25-Ampere discharge until terminal voltage drops to 10.5-Volts
AH = Ampere-hours; assumed the basis is a 20-hour discharge rate.
LBS = weight in Avoirdupois units
L W H = height, width, length in inches
PRICE = current advertised website prices July 3, 2018

I recently purchased the 24M model for these reasons:

  • better fit into existing battery box
  • 7-lbs more lead
  • more Ampere-hours capacity

Re: Battery Recommendations

Posted: Tue Jul 30, 2019 10:38 am
by jimh
I installed the 24M battery as the primary engine starting battery on my boat.

The nine-year-old SEARS DieHard Platinum Marine battery was moved to the secondary battery, where is will provide HOUSE circuit power. I discovered the Sears battery was a 34M case. The 34M case is not as tall as the 24M case, so the battery sits more deeply in the stock Boston Whaler battery box.

Lugging around these 50 to 60-lbs batteries, lowering them into position through the small hatches of the stern deck, and getting them into the battery boxes was quite an exercise for my 68-year-old back. The very low self-discharge rate of an ultra-high-purity-lead lead-acid AGM battery means it can sit in storage for eight months and not become deeply discharged. I won’t be removing these heavy batteries for winter layover.

Re: Battery Recommendations

Posted: Wed Oct 16, 2019 10:19 am
by jimh
The X2 POWER battery I mentioned above (and recently purchased) has the following information displayed prominently on a label on the top of the battery:

Dual Purpose / Deep Cycle


This battery requires a voltage limited charger set to the following settings:
FLOAT CHARGE 13.5 [to] 13.8V
CYCLE SERVICE 14.4 [to] 14.8V
MAXIMUM @ 25°C (77°F)

Re: Battery Recommendations

Posted: Thu Nov 07, 2019 3:47 pm
by jimh
Fig. 1. The Group 24 AGM X2 Power Battery.
battery24AGM.png (124.83 KiB) Viewed 7034 times

As seen above, the battery label declares "THIN PLATE AGM 99.9% PURE LEAD" and "POWERED BY NORTHSTAR PURE LEAD AGM TECHNOLOGY"

The Northstar website page on thin-plate AGM batteries says:

NorthStar uses innovative Absorbed Glass Mat (AGM) thin plate technology to deliver superior performance.

AGM batteries differ from flooded lead acid batteries in that the electrolyte is absorbed in glass mats, as opposed to freely flooding the plates. Very thin glass fibers are woven into a mat to increase surface area enough to hold sufficient electrolyte on the cells for their lifetime. This increased surface area and increased electrolyte are part of why NorthStar AGM batteries have such high energy density. This design also means NorthStar AGM Batteries can be recharged much faster than flooded lead-acid batteries.

NorthStar AGM batteries have a longer expected float life of 12-years [or more], with high stable voltage delivery. They also have the widest operating temperature range, delivering superior performance at lower temperatures.

You can buy what appears to be the same battery with the Northstar branding for about the same MSRP. See

Re: Battery Recommendations

Posted: Thu Nov 07, 2019 8:45 pm
by jimh
Follow-up on the $20 rebate: I sent in the $20 rebate form and received a $20 check several weeks later. I am generally always skeptical about rebate offers as they usually contain very detailed qualifiers and exclusions, creating some doubt in my mind if I will ever actually receive the rebate. But this rebate offer worked well.

My cost for the battery before state taxes was thus $325 minus 10-percent, or $292.50, and then $20 less from the rebate, for a net cost of $272.50 exclusive of state sales tax and core charge. The X2 POWER AGM s an expensive 12-Volt battery, but I expect it to last for ten years and relieve me of the chore of trying to charge it during winter storage.