Question regaring MPPT in series to support high voltage battery bank

[Unknown]

Lets assume that my solar panels and mppts match with one another

My problem though is that the MPPT do not match with the entire battery bank. My battery bank voltage is too high. If the battery bank is 72V. Is it possible to connect 3 MPPTs that can charge 24v batteries in series to charge it? I've attached an image to clarify. Let's assume that I can't buy a MPPT that can handle 72v, but I can buy multiple 24v ones.

Furthermore, I'm confused by the datasheet of MPPTs. If the nominal voltage only reaches 24v, but the MPP voltage range reaches 102v. Does this mean it can handle charging a battery of up to that value(102) or is it still limited to a 24v battery

nominal and max battery voltage.PNG

[inetdog]

The "nominal voltage" refers to the voltage of the battery bank. A 12 nominal battery has a voltage ranging from 15V under heavy equalization to 11V at low cutoff. But it is called a 12V system.
The MPP range, which is usually a bit smaller than the working voltage range, applies to the panel voltage input.

You cannot put two CCs in series to handle a higher voltage battery bank, and if you decide to treat the bank as two banks in series, each with its own ungrounded CC, then you still must drive those two CCs from totally separate arrays of panels.

[Logan005]

This is why I like Charge controllers like the Outback, Midnight and so on, You get many more options, to scale your system. One good $500 charge controller can operate up to 150vdc input and 12v, 24, 36v and 48 volt battery bank. If your using cheap limited MPPT CC, You will end up paying more and get much less and eventually end up upgrading at great expense anyway.

[Sunking]

No it will blow up into Great Balls of Fire. Just about every Solar Charge Controller has it chassis bonded to the negative battery circuit. That means all but one battery would have a direct bolted dead fault across the batteries.

[jflorey2]

My problem though is that the MPPT do not match with the entire battery bank. My battery bank voltage is too high. If the battery bank is 72V. Is it possible to connect 3 MPPTs that can charge 24v batteries in series to charge it? I've attached an image to clarify. Let's assume that I can't buy a MPPT that can handle 72v, but I can buy multiple 24v ones.

Yes, you can do it PROVIDED the charge controllers do not bond either battery or PV side to ground. For example, the Classic series of Midnite controllers do not bond to ground, so you could do it with them. (Of course, if you are going to use a Classic, they already support 72 volt batteries, so you wouldn't need to to begin with.)

Furthermore, I'm confused by the datasheet of MPPTs. If the nominal voltage only reaches 24v, but the MPP voltage range reaches 102v. Does this mean it can handle charging a battery of up to that value(102) or is it still limited to a 24v battery.

There are separate voltage limitations on PV and battery side.