Hey Dale - I think we have talked before... Don't know a whole lot on how the batteries actually work but have had alot of experience running those mounted on my past few trailers over the years.
A 26 Amp battery charger sounds about right size for a single battery if it has good DC VOLTAGE output control. Most of the converters/charger added to trailers using a single battery seem to come with a minimum of 25AMPs. Actually most of them are 35AMP and 45AMP sizes.
The batteries will only draw as much current as they need from the source depending on how much DC VOLTAGE is being provided. It doesn't really matter how much current capability the charger has until something drastic happens inside the battery that causes a SHORT CIRCUIT. Then of course if the source is a hugh 200AMP capable battery charger then the battery may explode on you. I have actually seen one explode back the old days where the battery charging concept was to hit the batteries with 20-30VDC running 100-200AMPS and get the quick 1 hour charge. Those batteries being charged were so hot you could not hold your hand on one...
This isn't done like that anymore... The battery I saw explode blew the top off the battery case which went way up into the air. Not a pleasant sight to see...
Progressive Dynamics has picked around 20AMPS per battery as the standard size battery charger. Consider this brochure report that is usually printed in most of the Progressive Dynamics converter/charger manuals..
"Progressive Dynamics ran this test on the amount of time it took a PD9155 (55-amp) converter/charger set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.
14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.
13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.
13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge."
Notice that they are using a 55AMP battery charger for this test...
Today's deep cycle batteries seem to like those three voltages listed in the brochure report when re-charging them which is called SMART MODE CHARGING technology these days.. You should purchase a smart mode technology type battery charger like the Black and Decker VEC1093DBD 40AMP SMART MODE Battery Charger. This seems to be the battery charger of choice among the RV deep cycle batteries.
My battery bank currently consists of three GP24 85AH Interstate Batteries connected in PARALLEL that are usually shipped with the new trailers. This is providing me with a 255AH battery capacity system. I have two GP24 batteries connected in PARALLEL in one battery bank and only one additional GP 24 battery in the second battery bank. I used to have two in this bank but one of them recently went south on me (after 4 years of service) so this second battery bank only has one working battery it now. These three battery are all controlled by two master bank battery switches where ALL or NONE of the batteries are connected in parallel. Then I have a third four position battery switch that selects each battery bank OFF-BANK1-BOTH-BANK2.
I maintain these three batteries with a Progressive Dynamics PD-9260C Converter/Charger unit. I am using one of these homemade BATTERY MONITOR Panels that monitors the 12VDC VOLTAGE coming from each battery bank as well as how much DC current is being drawn by the trailer. I can also monitor how much current the batteries are using when being re-charged by the same DC current meter.
When I am using my PD9260C converter/battery charger 60AMP unit to re-charge my three batteries I see the following results on my three meters. The two BANK 1 and BANK 2 DC VOLTMETERs show 14.4VDC being used on the initial start-up of the smart mode charge procedure. My current meter is now showing around 52-53 DC AMPS being drawn by the three batteries connected in parallel. This will relate to around 17AMPS being drawn by each battery. The current meter continues to show the 53 AMPS for about 10 minutes or so and then starts slowly dropping back which is telling me the batteries are taking the CHARGE. The DC current will eventually drop to around 8AMPs. The PD9260C smart mode charger is programmed to stay at the 14.4VDC charge level for around two hours time at which time it will drop back to 13.6VDC charge and my current meter will also drop back a couple of amps when this happens. The PD9260C will continue the 13.6VDC charge level from that point forward until it sees no current being drawn by the trailer at which time it will drop back to 13.2VDC. The three batteries will attain their 90% charge state about an hour after the PD9260C goes to its initial 13.6VDC charge mode.
If I remove SHORE POWER from the trailer after the batteries have been charged up to their 90% charge state I will see around 12.6VDC or so on the two BANK1 and BANK2 DC VOLTMETERs. now when I start running things in my trailer I will see a MINUS symbol showing up on the DC current meter which will be showing me how much current the trailer is now pulling from the batteries.
In a normal to us camping run off the power grid I will start out seeing around 12.6VDC on each battery bank 1 and 2. Usually between 8PM and 11PM is our biggest trailer draw time and I will see a MINUS 20AMPS sometimes on the DC current meter during this time but when we start going into our sleep mode and shutting down things in the trailer the DC CURRENT meter will show 1 or 2 AMPS for the rest of the night until 8AM the next morning. I can see the 12VDC levels of the batteries slowly dropping thru the night.
At 8AM the next morning I want to see the BANK1 and BANK2 batteries reading around 12.0VDC which indicates to me I am around the 50% charge state of the batteries. This is not a drop dead number but is where I want to re-charge my batteries to keep from doing damage to them. You of course can go lower then 50% charge state but to me I would like to not go below that number. A totally discharged battery is around 10.5VDC and you definitely don't ever want to go to this point. Damage to your batteries will most likely occur doing this. Damage occurs when crud starts building up on the inside battery cores. If the crud builds up enough to touch the other core next to it then its GAME OVER for that battery. The crud will also be growing on the cores all time when drawing current from the batteries but the trick is to keep the batteries fully charged which will dissolve the crud. There is name for this but its too long a word for me to remember it... I have also learned that I can cycle my batteries from the 50% charge state to the 90% charge state only so many times. After around ten re-cycle times my batteries start loosing a little proficiency and I have to do a FULL CHARGE to a 100% charge state to get the batteries back in good shape again. Of course this takes around 12 hours of 14.4VDC boost charge time and thats a long time to run the generator when camping off the power grid. Usually not allowed where we end up camping off the grid at. Thats usually when we pack up and head for the barn.
Bottom line to all of this is to purchase a smart-mode battery charger and not a charger that has poor control of the DC VOLTAGE output. The 40AMP model is perfect to me to use for up to four batteries in your battery bank
In your purchase mentioned listed above for a 26 AMP battery charger sort of tells me it was NOT a smart mode battery charger and indeed if the DC OUTPUT VOLTAGE went higher than 14.4VDC during the initial charge of a single battery then it could do some damage to the battery cores inside. A smart mode battery charger has excellent built-in DC VOLTAGE control to keep this from happening. i.e. it will never put out more than the BOOST CHARGE MODE (14.4VDC or so depending on charger manf)) and the internal resistance of the battery being charged should only demand around 17AMPS of DC current as was the case for the GP24 Interstate batteries I am using.
I learned all of this from staying in a Holiday Inn Select hotel in my many years of working...
If you want to go beat up someone for having to sit through all of this blame CRABMAN... hehe..