Battery Charging Settings

[BradS7535]

I'm finally getting around to inputting the settings for my solar charge controller for my batteries. I have some questions as to what some of the values should be.

Information:
Batteries = 2x Interstate 6V XHD in serial
Solarepic MPPT Charge Controller
Boost = Absorption

Charge Controller Settings:

Over voltage disconnect voltage = ? (16.0V default)
Charging limit voltage = ? (15.0V default, thinking 15.7V due to 15.6V equalize)
Over voltage reconnect voltage = ? (15.0V default, thinking 15.7V to match limit)
Equalize Charging Voltage = 15.6V (per Interstate Battery Charging)
Boost Charging Voltage = 15.3V (per Interstate Battery Charging)
Float charging voltage = 13.4V (per Interstate Battery Charging)
Boost reconnect charging voltage = ? (13.2V default)
Low Voltage reconnect voltage = ? (12.6V default, thinking 12.3V?)
Under voltage warning reconnect voltage = ? (12.2V default)
Under voltage warning voltage = ? (12.0V default, thinking setting to 50% or 12.14V per Interstate Battery Charging)
Low voltage disconnect voltage = ? (11.1V default, thinking to disconnect if below 25% or 11.7V per Interstate Battery Charging)
Discharge limit voltage = ? (10.6V default, thinking 11.3V per Discharge on Interstate Battery Charging)

As you can see, starting from the top and going down the voltages should be decreasing. Any help would be greatly appreciated.

[Padgett]

Am somewhat opinionated but think anything over 14v charging or 13.2v float is Too High.

Most of my batteries today are AGMs but I do have two GC2s in the TM. When a battery need more charging I have two "Smart Chargers" and usually charge at one of the lower settings (4A or 10A) otherwise are on little (80ma) float chargers when not being driven.

[BrucePerens]

Originally Posted by Padgett

Am somewhat opinionated

Padgett, higher voltages are just fine if you don't use them for longer than necessary. The point of a smart charger is to get the battery fully charged without boiling too much electrolyte, and it definitely uses high charging voltages to do that but it limits the duration they're used. If you keep the voltages as low as you prefer, you might never fully charge the battery and you might not equalize the cells.

The problem with not equalizing the cells comes if the user runs the battery down sufficiently to drive the lowest voltage un-equalized cell into reverse polarity. That'll probably ruin the battery.

Now, the way I'm opinionated is that I think that all valve-regulated lead acid (VRLA) batteries are a bad deal for campers. That's all of the AGM and Gel batteries, and the sealed wet cells. They do vent electrolyte in normal operation, and you never get it back, and eventually they fail by drying up. For this, you get a glass mat protecting your plates from shorting or a silica gel that keeps your battery from leaking if you turn it over. Big whoop.

Flooded batteries are no big deal to take care of, and are just a better deal for house batteries.

[scrubjaysnest]

Numbers look good, but I thought Interstate dropped their absorb to 14.8 volts like most everybody else. When they were 15.3 I quit using their batteries.

[BradS7535]

Originally Posted by scrubjaysnest

Numbers look good, but I thought Interstate dropped their absorb to 14.8 volts like most everybody else. When they were 15.3 I quit using their batteries.

I'm just going off that charging sheet I linked. If I'm using the incorrect voltage can someone point me to the correct charging sheet? Any other suggestions for the settings listed above?

[Padgett]

Might be I underrate a bit because I live in a hot climate and tend to keep batteries for a very long time

[BrucePerens]

Originally Posted by Padgett

Might be I underrate a bit because I live in a hot climate and tend to keep batteries for a very long time

That makes sense. My Morningstar has a thermocouple bolted to one of the battery terminals. Real smart chargers monitor the battery temperature, offset their charge points according to the temperature, and back off the current if the battery gets hot.

[Padgett]

That would be the ideal solution but would need one for each GC2. besides I am chea^H^H^H^H thrifty.

[BrucePerens]

Originally Posted by Padgett

That would be the ideal solution but would need one for each GC2.

It's a matter of diminishing returns. The batteries will be at the same environmental temperature, so the only thing you would get an indication of with a second thermocouple is if the batteries become so un-equal that you are heating one up and not the other.

You could as well ask for a thermocouple per cell. Which I know much more expensive batteries do have.

The GC2 batteries should be matched in size, production date, and date of installation, should be charged in series as a set so that they don't get unequal, and should get an equalization charge every month or so.

[scrubjaysnest]

Originally Posted by BradS7535

I'm just going off that charging sheet I linked. If I'm using the incorrect voltage can someone point me to the correct charging sheet? Any other suggestions for the settings listed above?

I looked at the linked sheet and it showed 14.7 vdc for absorb. And 15.3 for equalize.