Originally Posted by Knit
My Tripplite RV750ULHW manual explicitly says the switch setting is for AGM/Gel cell. So the advice here is to go against what the manual says?
I asked their support once about charging voltages and this was their reply
Bulk Charge - The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no "correct" voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.
Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts.
Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging. PWM, or "pulse width modulation" accomplishes the same thing.
Knit - It is interesting to see that and it helps explain the ongoing confusion around this.
The reply you got looks to have been directly copied from this book: https://books.google.ca/books?id=p57...A142&lpg=PA142
It's a very generalized theory of 3 stage charging and not at all specific to your particular charger. Disappointing that they'd send that ........
I have PDF versions of two Tripp-Lite manuals. The first covered the RV612 that came in my '04 Roadtrek and the second manual has the addition of the RV750 that came later. Neither mention AGM in the switch position section. Both have:
Battery Type Switch Position
Gel Cell (Sealed) Battery Up
Wet Cell (Vented) Battery Down (factory setting)
Both manuals state the voltages related to the switch positions:
Common Specifications for All Models • Acceptance Volts VDC: Selectable 14.4 V / 14.2 V - Wet / Gel • Float Volts DC (w/gel): 13.3 V (13.6 V) • ·
You only have the two choices so you choose the best match for the particular battery that you currently have. With some searching you should be able to find the owner guide for your battery brand/model.
Most often you'll find that recommended absorption charging for AGM is 14.4V. You'll find differing float voltage recommendations but usually 13.2V or 13.6V. I'm a fan of 14.4V charging and 13.2V float.
Those particular Tripp Lite units are timer based and lack temperature compensation. They'll do an OK job (far from excellent) if the battery bank is smaller like 200Ah or so. If you want much better care then you move up to a charger that lets you program the specific voltages your batteries need. You'll be able to set the amps in bulk mode, the end of the absorption phase will be based on current flow (when the batteries are actually full) and not a timer and it will have temperature compensation.