"24V" PV & 12V battery charge controller?

Hi David,

Thanks for your help.  The panel is a brand new "blem", and the j-box is sealed, with just 2 cables coming out (I haven't seen it yet, just looked online at a datasheet).  So I'm reluctant to hack at it and remove the epoxy or whatever.
The charge controller you recommended is interesting, but quite different from the products I've worked with so far (I'm quite willing to learn):
- There is no DC load connection, no LVD, no low-charge LED or indication, no state of charge LED or display, just a "charging" LED , and a "Full" LED.
In my experience, as we need to train the users to monitor their battery and not let it discharge too much so that it will last long enough, this lack of informational display is a problem.  The models I prefer allow the user to manage their use to keep the SOC around 75-80%, for a long battery life even without relying on the LVD feature.
Are these designed for systems that will be all in AC, with an LVD in the inverter itself?  For some reason, LVD's on (small) inverters always seem set way too low, like 10.5V, whereas LVDs on Morningstar or Phocos controllers are set around 11.4V.  At 10.5V, the battery is dead, not just discharged.  That's a whole bag of worms I'd love to understand as well some day, but for now I'll focus on just the charge controller.
Other question on the product you recommended (I looked up the user manual): the spec says Max output 10A, regardless of using 12V or 24V.  So if I connect a 215Wp panel, with say, 31Vmp and 7A  at 1kW/m2,  it takes that input but only gives me 10A *12V = 120W That hardly sounds like intended MPPT performance.  What am I missing?
Where we work, i.e. the tropics, we actually get more than 1kW/m2 on good days, so I want to make sure I use all I get.

Thanks

Hi Dave,

Thanks for all this.  The Morningstar MPPT 15A seems like the way to go.   I don't think we would use the RM, because the users wouldn't be able to make sense of the info.  The built in battery status LED should suffice.
Unfortunately, the panel is part of a larger donation, and it comes with a commitment to report on how it's being used, so I don't think any swap for a 12V is feasible here.

About inverters LVD vs. controller LVD.  Maybe we should start another thread for viewers benefit.  BUt in short, would it be possible to use the controller LVD by installing a relay on the controller load side, and use the relay to switch the inverter input on & off? 
I'm an ME and haven't looked into relays since school a long time ago, but there must be relays that consume current only at the time of activation, right?

[Otherwise, one advantage of the Phocos controller(s) is that they can sound an alarm as well as give a visual signal when LVD is activated.  That would help tell the user something need ot be done]

Any idea why the inverter LVD's are set so low?  Car batteries (the main market for those things) supposedly are even less tolerant of low voltage than deep cycle, so I find this really puzzling.

Thanks,
Michel

Hi guys, great conversation going on here.�  This is a common dilemma we deal with here at the AltE Store.

The problem with using the Morningstar 15A MPPT charge controller is that the 15A is max output.�  So if you've got 24V 8A in, and 12V out, that's going to double the output current to 16A out.�  That's too much.�  Also, the max wattage for a 12V battery bank is 200W, so the 215W is too high.�  So alas, that charge controller is just a little too small for this use.

You could use the Solar Boost 3024iL for $338.�  The Auxiliary Output serves as 20 Amp Load Controller.�  http://www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/MPPT-Solar-Charge-Controllers/Blue-Sky-Solar-Charge-Controllers-MPPT/Solar-Boost-3024iL-Solar-Charge-Controller-No-Display/p6784/

Give me a call and we can work out some details.

Amy
Solar Thermal Queen
AltE Store