Before this gets off on a tangent,
Most chargers are voltage sensing devices. The charging voltage from one can result in the other one not sensing the actual battery voltage fooling a charger into thinking the battery bank is already fully charged. Even solar can affect a converter/charger.
Does not matter if your using a PD9245 (45 amp) or a PD9285 (85 amp) converter/charger. The voltage settings for each charging stage is the same for all models. Therefore, it is not the set points in this case that determine how long it takes to charge, but rather how much amperage the converter/charger can supply and how big the battery bank is. You can recharge a battery with most trickle chargers if you can wait many, many days to do it (very small amperage rate). The higher amperage capability will decrease the charge time (not voltage settings for like simular units). The only rule of thumb to follow is don't let the amperage charging rate exceed 25% of the total AH capacity of the battery bank. If, you are using something like a Trick-L-Start or a BIRD system, then remember the chassis battery becomes part of the total battery bank capacity. The effect of amp rate and the effects of voltage surface charge is why devices such as the Trimetric battery monitor and the Inverter/charger controllers use amperage flow to determine state of charge rather than voltage.
Now, with that said, if you are using a converter charger like the Boondocker brand or a Inverter/Charger that has adjustable stage set points, then the charging time can be decreased somewhat because the bulk stage voltage set point is 14.6VDC or higher rather than the 14.4VDC of the PD units. Please note that Trojan Battery Company does say that the proper bulk stage charging rate for their T-105 batteries is 14.8VDC (
http://www.trojanbattery.com/pdf/TRJ...UsersGuide.pdf). The trade off for the higher voltage though is higher water loss due to boiling. Please note that even though 14.8VDC is listed by Trojan there are only a few marine converters that provide that. Some higher end Inverter/Chargers do allow you to set these higher Boost mode levels. Converter Mfgs design to the much broader range requirements of the mixed 12VDC and 6VDC battery community rather than just one battery mfg type.
Boost stage brings the battery up to around 90%-95% capacity. Absorbtion and Float modes operate the same for all units. Absorbtion mode is used to complete the charge by setting the voltage to 13.6VDC and then decreasing amp rate as the battery completes the last portion of the charge cycle. Absorbtion mode is also typically used for normal RV load use. Converter basically transitions to float mode (13.2VDC) once it senses there is no loads on the system.
A few more things to remember:
1 - Once a battery appoaches 90% capacity during a charge cycle, battery water boiling increase at the higher charging voltages (14.4VDC - 14.8VDC). Thats why the charger transistions to Absorbtion mode.
2 - Extended operation at 13.6VDC (Absorbtion mode) with no loads drawing excess current off can also result battery water boil off. That was the main issue with older linear style converters. 3 stage units transition to 13.2VDC FLoat mode to avoid this problem.
Dave
Linear Mode
