backup battery bank mppt setting question

[Minimoose]

I have two battery banks of 400ah each and only use them in power outages. One bank runs my well pump with a 4000 watt inverter and the other bank runs essentials with a 3000 watt inverter. I have 1400 watts of panels that I kept portable for now. The only draw on the batteries is the charge controllers which isn't much. I decided to plug up one 100 watt panel to each battery bank just for maintenance purposes to keep them topped off. Every night the banks both level out at 13.1 volts so every day they are going into boost (14.4 volts) and later floating at 13,8 volts. Is this harmful to my agm batteries? should I set boost to 13.8 volts temporarily or maybe reduce the boost return voltage to 12.9 or 13 volts? If I don't hook up the solar panels at all the batteries will drop to about 12.8 resting voltage in about a week and a half which isn't too bad either. Thanks!

 

[sunshine_eggo]

I have two battery banks of 400ah each and only use them in power outages. One bank runs my well pump with a 4000 watt inverter and the other bank runs essentials with a 3000 watt inverter. I have 1400 watts of panels that I kept portable for now. The only draw on the batteries is the charge controllers which isn't much. I decided to plug up one 100 watt panel to each battery bank just for maintenance purposes to keep them topped off. Every night the banks both level out at 13.1 volts so every day they are going into boost (14.4 volts) and later floating at 13,8 volts. Is this harmful to my agm batteries?

No. It's good for them to be at 100% as often as possible.

 

[Minimoose]

No. It's good for them to be at 100% as often as possible.

Thank you! I'm used to maintaining my normal motorcycle,car, and mower batteries, but I keep noco genius chargers on all 5 of them. I thought about doing that with my battery banks, but it would be silly not to use the solar I already have.

 

[Wellbuilt]

I would not boost/ charge every day .
I woul maybe charge once a month .
My LA battery’s sit at full for months
They just went allmost 4 weeks and they where 51.2 when I turned the system on .
I charge one hour on day one 11/2 hours on day 2 2 hours on day 3 and day 4 gets a full charge .
In the summer months I like to charge all day and just get to full as the sun gos down

 

[Minimoose]

I would not boost/ charge every day .
I woul maybe charge once a month .
My LA battery’s sit at full for months
They just went allmost 4 weeks and they where 51.2 when I turned the system on .
I charge one hour on day one 11/2 hours on day 2 2 hours on day 3 and day 4 gets a full charge .
In the summer months I like to charge all day and just get to full as the sun gos down

I was thinking the same thing. I can just unplug the panels and charge once or twice a month. I also thought about setting the boost time to zero and lowering the float down to a lower setting just to them right around 12.9-13.0 volts idle. I'm not sure about the deep cycle batteries, but I keep my vehicle agm batteries 12.8 to 13.1 volts when not in use.

 

[sunshine_eggo]

If your batteries have a "standby" charge voltage, set absorption and float to that. 13.5-13.8 are typical values.

If you really object to re-bulk, then daily charging to the standby float is vastly preferred. These things LOVE to have a slow trickle of electrons charging them all the time.

 

[Minimoose]

If your batteries have a "standby" charge voltage, set absorption and float to that. 13.5-13.8 are typical values.

If you really object to re-bulk, then daily charging to the standby float is vastly preferred. These things LOVE to have a slow trickle of electrons charging them all the time.

Actually I'm a little concerned that I am under charging. The NPP batteries say 14.5 to 15 volts for cycling and 13.5 to 13.8 for float. The universal batteries say 14.6 to 14.8 for cycling and 13.6 to 13.8 for float. That's actually closer to the flooded lead acid settings and not the sealed lead acid. I really don't mind them boosting every day as long as it doesn't shorten the lifespan. Thanks for the reply!

 

[Rednecktek]

That's actually closer to the flooded lead acid settings and not the sealed lead acid. I really don't mind them boosting every day as long as it doesn't shorten the lifespan. Thanks for the reply!

I was just thinking the same thing. Are you sure your SCC isn't set to FLA battery settings instead of AGM/SLA settings?

Otherwise, yes. Lead based batteries like to be full up all the time if they can be.

 

[Minimoose]

I was just thinking the same thing. Are you sure your SCC isn't set to FLA battery settings instead of AGM/SLA settings?

Otherwise, yes. Lead based batteries like to be full up all the time if they can be.

I actually had them set on SLA setting, but last night I set them to FLA. They are doing boost mode at 14.6 right now.

 

[fratermus]

I really don't mind them boosting every day as long as it doesn't shorten the lifespan

Food for thought, since these are for standby and not cyclical use. If the controller{s} are configurable I might consider:

1. Absorption ("boost") == the high end of float spec (13.8v?) for daily charging
2. Float == Absorption, or maybe the low end of float spec (13.6v?)
3. Equalization == Absorption spec (14.6v?) for monthly full-charging

Might have to toy with the quasi-EQ duration to see how long it takes for current acceptance to drop to C/100 or whatever.

 

[12VoltInstalls]

last night I set them to FLA. They are doing boost mode at 14.6 right now.

Just make sure the Flooded settings doesn’t try to equalize them which could be 15+ volts. AGMs don’t want that iirc. (Other than alarm and life safety batteries for places I’ve worked I’ve never bought an agm)

 

[Minimoose]

Just make sure the Flooded settings doesn’t try to equalize them which could be 15+ volts. AGMs don’t want that iirc. (Other than alarm and life safety batteries for places I’ve worked I’ve never bought an agm)

FLA setting was 14.8 volts I lowered it to 14.6 to match the boost setting. I'm thinking about just setting boost, equalize, and float all to 13.6 for now. Easy to do with the user settings.