Solar -> 4x12V batteries

[agenthex]

I own a CyberPower PP2200SW battery backup, and I would like to expand the battery storage and charge it with a solar panel. I want to use a MPPT charge controller, but I need to know if I need more than one.

I assume that the four 12V batteries in the UPS are in series, so in addition to connecting additional batteries in parallel with each existing battery to expand capacity, I need to know how to connect charge controller(s) to keep the array topped.

Will the following schematic work?

       A           B           C           D           E
       |           |           |           |           |
(+48V) -> [+12V-] <-> [+12V-] <-> [+12V-] <-> [+12V-] <- (-48V)

A - First charge controller  (+) and UPS (+)
B - First charge controller  (-) and second charge controller (+)
C - Second charge controller (-) and third charge controller  (+)
D - Third charge controller  (-) and fourth charge controller (+)
E - Fourth charge controller (-) and UPS (-)

Additionally, if I use multiple charge controllers, is it safe to connect all four charge controllers to the same solar panel? Or do I need one panel for each controller?

Lastly, if I want a 12V source, can I connect the output from all charge controllers together without worrying that the controller will cause an internal short?

[Sunking]

Good luck getting an answer. I would answer your question, but you would not understand.

[agenthex]

OK. Well, thanks for taking the time to not answer my question. More importantly, thanks for assuming that I'm not smart enough to understand. You could have just not posted, and I'd be exactly where I started.

[Wy_White_Wolf]

Why would you use 4 - 12v charge controllers instead of 1 - 48v charge controller?

You have a lot of basics to learn before you try anything like this.

WWW

[agenthex]

Hi, Wolf. Thanks for the heads-up. I guess I need to learn more, but reading is not asking, and asking is not doing, so I figured I'd take the next logical step.

I suppose I could use a 48v controller, but I wanted access to a 12v line as well. Perhaps a proper DC-DC converter is necessary.

I don't know that much about configuring VRLA cells for series/parallel, but I wanted to expand the capacity of my UPS far beyond its integrated bank and charge the entire bank with either the built-in charge circuitry (when connected to A/C) or solar using at least one panel (with both BMS maintaining the same batteries at the same time).

[Wy_White_Wolf]

Then you'd use a DC-DC converter for the 12vdc access. Trying to put a tap in for 12v off of 1 battery creates out of balance problems that will destroy the batteries. Charging the seperately can also create that out of balance problem.

Also Parralleling an old set of batteries with a new set is asking for trouble. The 2 strings will never charge the same and end up destroying both sets of batteries. Replace all the batteries with the same type/age.

WWW

[agenthex]

Charging the seperately can also create that out of balance problem.

I was hoping to avoid this by using separated charge controllers and putting the batteries in parallel before connecting in series. The UPS could charge the bank as 48v (when connected to A/C), and separate 12v solar controllers would keep the parallel cells balanced relative to each other. If I put the existing batteries in parallel with each other, then newer cells could be installed in series (of parallel) with the existing cells. Hopefully this would avoid older cells wearing on new ones, but maybe that's unavoidable without all-new cells.

That is what I need to know even if it's not what I want to hear.

[Wy_White_Wolf]

I was hoping to avoid this by using separated charge controllers and putting the batteries in parallel before connecting in series. The UPS could charge the bank as 48v (when connected to A/C), and separate 12v solar controllers would keep the parallel cells balanced relative to each other. If I put the existing batteries in parallel with each other, then newer cells could be installed in series (of parallel) with the existing cells. Hopefully this would avoid older cells wearing on new ones, but maybe that's unavoidable without all-new cells.

That is what I need to know even if it's not what I want to hear.

You're thinking is completely bassackwards. The 12v controllers will create the imbalance instead of prevent it.

You cannot have batteries both parrelled and in series. Seperate series can be parralleled.

The new/old battery problem is unavoidable.

WWW

[agenthex]

OK, last questions:

1) If I connect multiple 48v series of batteries in parallel and charge them with one MPPT controller and one panel, what do I do when I want more solar panels?
2) Do I need identical solar panels?
3) Can multiple solar panels be connected to the same charge controller?
4) Can multiple controllers be connected to the same battery bank? (And how?)

Thanks for your help.

[Sunking]

WWW you walked into a trap.

[inetdog]

OK, last questions:

1) If I connect multiple 48v series of batteries in parallel and charge them with one MPPT controller and one panel, what do I do when I want more solar panels?
2) Do I need identical solar panels?
3) Can multiple solar panels be connected to the same charge controller?
4) Can multiple controllers be connected to the same battery bank? (And how?)

Thanks for your help.

Looks like a set of four questions to me!

1. You add more panels. Although typically one panel will not produce a high enough voltage to charge a 48 volt battery bank, since the MPPT controllers only reduce the voltage, they do not increase it.
2. No, but they need to be close in either current or voltage depending on how you wire them.
3. Yes, it is very common.
4. a. Yes. But each CC will need its own array of panels. You cannot go from one array of panels through multiple MPPT controllers to either one or several battery banks.
b. By setting them to the same output voltage setpoints and wiring the outputs in paralllel.

Sunking will be happy to design all of this for you if you pay his hourly rate and minimum contract.
Preferably in advance, of course.

[agenthex]

Thanks for your input.

If I get four 12v panels in series and attach them to a battery bank through this, I could charge a 48v bank and patch into my UPS which would essentially be a 1500W inverter. I don't expect to use more than 100W at a time for 90% of the time, but it would be nice to be able to run more power-hungry appliances even off the grid. I have a smaller inverter, but it's 12V, so if the UPS inverter is wasteful, I might have to use a DC-DC converter to step to 12V, at which point the UPS is only used as necessary.

I think the best course of action for me is to get panels and a solar controller, interface with the 48v pack in the UPS, and consider a new AGM bank to replace the stock batteries when they are old enough.

[Sunking]

it would be nice to be able to run more power-hungry appliances even off the grid.

It would be very foolish of you to take anything off-grid. If you do that you just volunteered to pay 5 to 10 times more for electricity the rest of your life. Very foolish.