charging a second battery bank , with dump load from a pmw

Yes, you are correct. It would work.

However, I dislike complexity of design in systems that are supposed to work for years with little maintenance. You would need at least two charge controllers on bank "A". One to move current to battery bank "B", and a second controller to dump excess energy from "A" to a resister bank when "B" is full. And, you really should have a backup dump controller+load on "A" in the case if both dump controllers/loads fail.

Second--If you do not have enough energy--Battery bank "B" will be the first to suffer--Needing you to use a backup genset and/or you will need to manually manage loads on bank "B" (and "A"?) to ensure that you do not kill either bank.

Dump controllers are not as good at regulating battery bank state of charge--You either are dumping charging current into the bank or dumping load. With series (standard configuration) solar charge controllers, you are either charging or "off"--This is better.

Now--Normally, in a system with a solar array, you would have a series charge controller for the solar array regulation, and a second (one or a pair) of dump controllers setup as dump controller(s) to regulate the wind turbine charging (the solar controller would be set, for example, to charge to 14.6 volts, and the dump controller set to charge to 14.8 volts. Wind turbines typically do not have predictable/daily charging unlike solar. Gives you the advantage of better charging controller with the series type solar charge controller and the dump controller to control over charging when needed during stormy weather/windy season). That is another charge controller (with PWM controllers, you can share one solar array with two PWM charge controllers to separate battery banks).

I would suggest that you simply have one battery bank / charging setup (solar+wind)--And simply mange your secondary loads (turn them off when poor charging conditions are present--or when the battery bank is at a lower state of charge).

Things fail--And they can fail in different ways. A failure of a series charge controller will stop charging your battery bank (not good for the battery). A failed dump controller (or dump load) will over charge the battery bank and can run the risk of fire. (note: series charge controllers have been known to fail and over charge batteries too, just that failing shorted seems to be less common).

I believe that a single battery bank will be much easier to maintain, debug, and safer than a "master/slave" battery bank setup.

-Bill

There is one "master/slave" battery system that people have used successfully. The standard 24/48 volt master battery, and a smaller 12 volt battery for 12 VDC devices (such as HAM radio gear).

Use an MPPT type charge controller to take the higher voltage battery and down convert to the 12 volt battery. However--As you can tell, this discharges the main battery bank in favor of the lower voltage battery bank--So you still have to monitor your loads.

By the way, how well is the wind turbine working for you? In general, most installations do not seem to reliably generate much useful power. There are a few people that have done well, but most build their own turbines on put them on 60-90 foot towers.

From a person that ran a Skystream turbine for a few years (grid tied--So this is the "best" harvest that you will get--Battery charging always "tosses" some energy away when the batteries are full and you do not have enough loads--Note that the Skystreams did seem to be the best producing "small" wind turbines--When they worked):

Good wind near Lake Erie or other Great Lake... (as I recall)?

https://web.archive.org/web/20100603163140/http://blog.keepturning.com/2008/02/11/janes-household-skystream-kwh-record.aspx

For most people, I would suggest solar panels is a better/lower maintenance/cost system... However, if you are in Peterborough, EN, United Kingdom area--You probably don't get much winter sun (fixed array, 45 degrees):

http://pvwatts.nrel.gov/pvwatts.php

Month	Solar Radiation ( kWh / m2 / day )
January	1.12
February	1.93
March	3.06
April	4.12
May	4.79
June	5.10
July	5.09
August	4.56
September	3.54
October	2.33
November	1.33
December	1.03
Annual	3.17

3 hours of sun per day of sun is pretty reasonable. 1 hour of sun per day--Not great.

-Bill