There really isn't anything magic about charging deep cycle batteries.
Here is what PROGRESSIVE DYNAMICS says about charging DEEP CYCLE MARINE TYPE batteries... We follow this guideline pretty close in our travels...
"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."
This is battery charging science at play here - not many ways to get around it
My PD9260C Smart Mode converter/charger will return my three 85AH Standard Issue GP24 Interstate 12VDC batteries to their 90% charge state in around three hours time. This happens when I am connected to SHORE POWER or running my trailer directly from my 2KW Generator using a RV30A-15A Adapter...
When my three batteries get hit with 14.4VDC Charging DC Voltage they will immediately start demanding around 53AMPS DC Current from PD9260C Smart Mode Converter/charger unit. This DC current starts dropping back in around 15 minutes as the batteries start taking on the charge and in an hours time is only drawing around 8AMP DC current while still being fed with 14.4VDC from the converter. After two hours of charging at 14.4VDC the smart mode converter/charger unit will drop down to 13.6VDC Charging mode with the DC Current now reading around 6AMPS DC. This mode will continue for another hour before attaining a 90% charge state for all three 12VDC batteries being charged together. The smart mode converter/charger may switch to 13.2VDC at this time if no load is being drawn from the battery bank. When a load is presented to the battery bank the PD9260C will autoswitch to 13.6VDC and remain at this level until the load goes away where it will again return to the 13.2VDC mode.
When the trailer load reduces the battery level to around 50% charge state then the PD9260C will go into its 14.4VDC boost charge mode again and will bring the battery bank to its 90% charge state in about three hours time.
This is the cycle process for my battery bank charging process using my PD9260C 60AMP Smart Mode charger.
If your charging system never hits the 14.4VDC mode then it will take many hours to attain a 90% charge mode status as indicated in the above Progressive Dynamics stated process. Most folks think you can force many AMPS into the charging process to make batteries charge faster. I have found this to be a 'NOT TRUE' assumption. You could have a 100AMP or even a 200AMP Source of 14.4VDC Charging Voltage and each 12VDC battery will only draw 17-20AMPS of this available 100AMPS charge source while being charged. The only way to charge quicker is to raise the charging DC Voltage. The down side of doing this is the battery will develop more heat in the process and will immediately start boiling your battery fluids. This could become very unstable and could end up in the battery actually exploding on you. The BATTERY FOLKS have determined the safe charging technique is to use around 14.4VDC to charge your 12VDC Battery and this process will take around three hours time to attain a 90% charge state.
I am NO BATTERY EXPERT just what I read about from folks like PROGRESSIVE DYNAMICS and TROJAN and also from my experience of charging my battery banks over the past few years.
Back in the 50s the local garage would advertise a quick one hour charge as the best way to get your battery charged. They would hit the 12VDC START BATTERY with around 50VOLTS DC (or more) with around 150AMPS available DC Current. The battery would almost turn "red" on you while being charged. Batteries would also explode on you. I witnessed one blowing its top which went into the air a good 50-feet or so at a local garage doing this. Glad I wasn't leaning over the battery when it happened...
Just saying....
Roy Ken
