Quote:
Originally Posted by lbmaples
Would it be better (faster) to let my converter charge the batteries at 13.6 volts at 10 amps , or a charger at 20 or 30 amps at 14.5 volts .
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A good (modern) 3 stage converter will charge at 14.4 volts in boost mode, dropping to 13.6 after it detects an 80% SOC back voltage until it fully charges the batteries and then drops to 13.2 (storage or trickle) from there. Some have a 4th stage that bumps the voltage back to 14.4 volts for 15 minutes every day or so to attempt to keep the battery electrolyte mixed.
Frankly, this is as good as you are going to do. Most battery chargers are more poorly filtered and will effectively give you boost and trickle stages, but they are no better than a good converter, although some might hit your system with more than 14.5 volts which can be dangerous for the loads that are connected. (Trojan specifies an occasional equalization voltage of 15.5 volts, but warns that the batteries should be disconnected from the loads during this process, which also tends to boil off a lot of electrolyte and should be closely monitored.) The converter has the 13.6 volt mode to both finish charging the batteries and to supply power to the loads in your RV while plugged into shore power.
The actual limitation is that many converters are located too distant from the batteries and wired with less that optimal gauge wire (mine are #6 or #8 at 22 feet from the bank) Since the converter only outputs these voltages on its terminals, the batteries see that voltage (and charge current)
minus the voltage drop of the cabling. I have a Progressive Dynamics 9270, which will output 70 amps but with the voltage drop of the cables would only hit the batteries with 13.1 volts at 70 amps. This actually drops the maximum charge current well below 70 amps and lengthens recharge times. I have thought of using a chassis ground which would cut the loss in half, or rewiring the feed with much bigger cable.
Frankly, RV manufacturers are stuck trying to build for a given use and they assume that most RVs will remain connected to shore power for most uses. Frankly, I believe that they are correct.