I talked with length with an Odyssey tech, who did confirm that there are no internal differences between SEars DHP and Odyssey.
The marine versions have both the automotive posts and threaded studs.
What I called the tech about was the recharging requirements.
When deeply cycled, they want a very high recharge rate. 0.4C, or 40 amps for a hundred amp hour battery. Once 40 amps brings the battery upto 14.7V, the charger is to hold the battery at 14.7 for 4 hours, then drop back to 13.7 float voltage.
not meeting these rather high charge currents on a deeply cycled battery will never allow the battery to reach full recharge.*
I asked about a not so deeply cycled battery, and he said they still require this charging regimen for maximum lifespan and performance during that lifespan.
I was mainly concerned about my 200 watts of solar not being able to even come close to this number for one battery, much less the 3 I was considering.
My alternator can meet 40 amps at 14.7, but I don't drive for 4 hours straight very often
I do not have a charger able to meet 0.4c for the capacity I was considering
I did not feel I could properly recharge an Odyssey/DHP in my application. I suspect few can and actually do.
I did acquire a Northstar AGM battery as my Engine battery. These also have similar charging requirements when cycled deeply. I do have a charger which can meet the 0.4C for a 90 amp hour battery, but I am not sure I am going to cycle this battery often.
However I have taken it down to 40%, and recharged it at 0.4C, held 14.65 for 4 hours, and 7+ hours after removal from charger the battery was still at 13 volts. Before cycling it this deeply and recharging it at 0.4C, it would not rest above 12.8 from alternator or solar the first three days after purchase. It had to be cycled and recharged at 0.4C for it to hold the 13.0 rested OCV.
The Odyssey tech said at least two discharges and recharges at 0.4C would be required to bring an improperly charged battery back up to its maximum remaining capacity/ energy density.
I think any reports of poor performance/ lifespan from Sears DHP or Odyssey are largely user induced by not meeting the rather extreme recharging currents recommended by the manufacturer. Many will say you do not need a special charger for AGM. When the manufacturer recommends a certain charging profile that is outside other AGM specs, or FLA specs, it is for a reason. Ignore them at the expense of your wallet. Perhaps you do not have to meet them exactly to get good service from them, but the closer you can come to meeting them, the better.
* The Odyssey tech did say the battery could be fully charged by lesser currents, but required higher voltages(16.5) and low current(1.8 amps), and lots of time.
16.5v is in the danger zone for automotive electronics so I ruled out these Dualpro marine chargers he names as being acceptable for their batteries despite NOT meeting the 0.4C recharging rate.
http://www.powerprosinc.com/Pro-Charging-Systems-Professional-PS3-Battery-Charger.html
Also to note that currents over 5 amps at 15 volts will pop the vents. Do not think you can just run a charger on the flooded battery equalization setting to make up for the lack of 0.4c charging current.
While I can fit 2 group 27 batteries in my auxiliary battery tray, I lowered my overall capacity with just one group 31. A Flooded group 31 US battery that recommends an ~0.1C recharge rate. My Solar can almost meet this, in the summer, and I hope to achieve more cycles by coming much closer to this manufacturer recommended minimum recharge rate. I did not ever require the full capacity of 2 '27's.
The Low and slow trickle charge mentality, In my opinion, is an old wives tale.
Also, beware of the Flooded marine battery, and do not listen to those who say a Marine battery is a deep cycle battery. Any battery can be deeply cycled a few times, that does not make it a deep cycle battery.
One company told me I was buying a 130 amp hour group 31 deep cycle battery from a reputable manufacturer. My capacity test the first night revealed it to be under 100 amp hours and my "extreme cycle service battery" was just in fact a lightweight marine battery.
The scale revealed it to be 56 Lbs. I returned this "Extreme cycle service" group31 battery for a USbattery in the same exact case dimensions, which weighed 10 Lbs more.
Extreme cycle service from a flooded marine battery? What a joke. Buyer beware. Bring your bathroom scale and armed with knowledge. Trust no salesman.
