Platinum and Odyssey likely one in the same
Just wrapped up some lengthy research and discussions with Enersys on the PC 1750 vs Sears Diehard Group 65 P-2 for my '99 Powerstroke. Found this forum and thought many might be interested in the comparison and special charging needs for deep cycle service. Have also included a PDF table for the comparison. While Enersys would not state the batteries were the same, they did say the batteries were made on the same production line. The table tells me a lot.
View attachment odyssey 1750 vs diehard P2.pdf
You will probably find similar comparisons between other Sears Platinum and Odyssey models and group sizes.
This posting has undergone a few edits and some visitors coming back to the site have probably noticed that. Most of that has been for clarification and to direct readers to the Odyssey publications.
If you are considering this type of battery,
especially for deep-cycle service, be sure to go to the Odyssey web site to learn about this technology's charging needs. If you
never deeply discharge this battery, charging requirements are likely to be more forgiving. If you allow the battery to become depleted without taking into consideration parasitic loads, that counts as deeply discharging just as it would if you were running accessories before recharging. Also consult the General Provisions section of the Warranty in the owner's manual which also specifies information on charging needs.
There is an owner's manual AND a technical manual for these batteries available for download. Generally speaking, for deep-cycle operation you will need a charger that can provide ~40% of the 10 hour rating for the bulk charging stage PLUS nominal 14.7 and 13.6 constant voltage absorption/float stages. So, for a battery with a 10 hour rating of 65 amp/hours, you will need a charger capable of supplying a nominal 25 amps in the bulk stage plus the nominal voltages for the absorption and float stages.
The material goes deep into charging procedures for 3 different designs of automatic chargers as well as guidelines for manual chargers. I had covered some detail when first posting this, but have removed it because I felt the expeditionportal viewers would be better served by consulting official Odyssey pubs. Go to the Odyssey website
http://www.odysseybattery.com/ for the most current information. If you use a manual charger, be sure to understand the transition points and limitiations between stages.
I would venture to say that if your battery is forced into float before charging current is reduced as described for the timed absorption stage, your battery is likely beginning to lose capacity. Desulfation might correct the issue. Do not allow the charging voltage to ever exceed 15 volts. This will cause the internal pressure valves to open and out-gas hydrogen. Voltages of 15 volts and higher can easily be reached by the older unregulated chargers as the battery approaches full charge.
If you cycle these batteries as one might typically would for flooded lead acid deep-cycle batteries while boon-docking or on a sailboat [discharging them to 50%, then recharging to 80% (typical for maximum generator efficiency)], these batteries will likely be killed off in less than a year. If you recharge them with just any off the shelf so-called "smart charger", you could very likely get only 75% of the design life from them. Do not trust chargers that claim to have an AGM setting without verifying the profile needed for the Odyssey batteries!! Nearly every charger I have examined, even those that claim to have an AGM mode, either provides absorption and float float voltages that are too low to obtain maximum life from the Odyssey battery or the charge profile is not even specified!!
Be sure the nominal constant voltages mentioned above are measured at the battery, especially if the charger has detachable cables. On a very expensive charger/inverter setup I own, I was using jumper cables from the charger output. Voltage at the battery was .3 volts below the required voltage level, while the temperature compensated voltage at the charger output was correct. Switching to the proper gauge cable eliminated the voltage drop and provided the exact same voltage at the battery as the charger terminals.
Be sure the voltage output of the charger is temperature compensated. One chart I use (from Xantrex) shows charging voltages for absorption and float for AGM batteries should be decreased .1 volts from nominal for every 10° F increase in temperature above 70° to avoid the pressure valves from opening. Voltages should be increased by the same amount for every 10° F decrease in temperature below 70° to avoid undercharging the battery. While this chart is useful and you might be able to rig up a manual charging process, you will be better served with an automatic temperature compensated charger specifically designed for this battery technology.
Also, the stock converter/charger found in most RVs is woefully inadequate for any kind of battery long term, let alone for something of the caliber of an Odyssey/AGM battery. They will cook a flooded battery and undercharge an AGM, which shortens the life of the AGM. These converters are still used today because they are cheap, not because they are good for your battery!
Odyssey does provide a list of recommended chargers if you're not going to use an Odyssey Charger and it looks like it is updated each year. Do not use trickle chargers to charge a deeply discharged battery. Trickle chargers and float chargers are intended ONLY for batteries that are already nearly fully charged.
My "odyssey" with the Sears Diehard Platinum is just beginning. After learning of the challenges associated with AGMs in general, I took a voltmeter with me to make sure that only the 2 batteries with the highest open circuit voltages were chosen. Of the 10 that were there, 8 measured in the 12.6-12.7 volt range. I found 1 with 12.86 volts and another with 12.93 volts. An open circuit voltage of 12.84 or over is considered 100% charged. The voltages of the other 8 indicated states of charge (SOC) between 85%-95%. All were manufactured within one month of each other and the 2 I chose presumably had a lower self discharge rate since leaving the factory.
Have not yet bought a charger as am able to make do with the combination of chargers I already own, but Sears says the Diehard Platinum 71227 charger can be returned if it's charging profile does not match the profile described in the Odyssey Technical Manual, especially the 40% of 10 hour amp hour rating. The failure rate of the 71227 is reported to be somewhat high, but within the 3 year warranty period. If it were to fail, replacing it could be easier locally, but also note that after 2012 Sears may be dated as a retail concern. I will likely end up with the Odyssey Ultimizer OMAX-25-1B and is warranted for 5 years.
Practically all major battery manufacturers are starting to jump into the AGM market. There are leaders and followers of this technology in the industry. Specifications and prices can vary greatly. If an AGM for your group size weighs only 45 lbs with one mfr and 60 lbs with another, there is a reason for it. Mostly, it's to get the cost down. Performance will be affected proportionally. You cannot assume they are all the same. I would avoid any brand of AGM where the manufacturer cannot provide detailed written information on how to take care of them. I would also avoid chargers that where the charging profiles for each setting are either not specified or don't meet your intended AGM's manufacturer's requirements. I respect an AGM's retailer to need to make a living, but all of them I talked to don't have a clue about what these batteries need. Consult the manufacturer for any brand you are considering.
Hope this helps somebody.
