AGM Battery float and absorb specs, off grid 12 volt system

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AGM Battery float and absorb specs, off grid 12 volt system

Postby diboranian on Wed Oct 11, 2017 12:14 pm

I live on the Island of Hawaii(Big island) at about 1100 foot elevation on a small coffee farm. During part of the year we have cloud cover for a significant part of day(that is part of reason Kona Coffee is so good!). My system is off grid and I have no generator or other source of recharging batteries. I have two solar arrays of 4 panels each. One is 4 Kyocera 240's and the other is 4 Chao 280's. Both arrays are connected to separate FlexMax 80's. I have 8 Leoch EV6390's connected to an Outback inverter. My first L-16 batteries (wet cell)did not last as long as I had hoped. I was not as diligent as I could have been in their maintenance... With the new Leoch EV6390's(AGM maintenance free) I am committed to learning more about my system. I have read the manuals for the Flex Max 80 and the Mate system controller.
I have a few questions...

1. I have read that it may be more detrimental(as long as you don't overcharge them and create"hot spots") to the long term life of the AGM batteries to undercharge them. Is this true?

2. It is also dangerous to create "hot spots" by having too high of a current during the charging of the batteries. I plan to monitor my system during different insolation conditions and "fine tune" to make sure my batteries are maintained at full charge. What is best way to tell when the batteries are full? Is a full battery indicated by a drop in the current flowing into the batteries during the charging process? If so how low of a current is indicative of a full charge?

3. My system is wired as a 12 volt system with two batteries wired in series and then four of these couples wired in parallel. EV 6390 spec sheet indicates that Charge Voltage should be 6.8-6.9V for Standby(Float?) use and 7.2-7.35V for Cyclic(Absorb?) use. I have read that since the daylight hours limit time in float use I can safely program my system to use the higher voltage(7.2-7.35V) for the Standby(Float?) use. Is this true?

4. Given that I have a twelve volt system I can double the above numbers for Standby(13.6-13.8V) use and Cyclic(14.4-14.7V) use?

Thank you for your time. I really want to learn about this renewable technology and I have been told so much conflicting information by "professionals" who are adamant about the veracity of their information. Everyone can not be right so I decided to go to the source which is you as the manufacturer.
Thank you,
Dickran Boranian, MD
Junior Member
Posts: 1
Joined: Wed Oct 11, 2017 12:01 pm
My RE system: Flex Max 80(2), Outback Inverter, Mate

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