When ANY charging source is applied to the battery combiner with voltage of 13.3V or higher, it will engage and parallel the batteries. I think we can agree on that.
Contrary to popular misconceptions chargers do not "put out a voltage", as I hear so often, they supply
current! The chargers only role that has to do with voltage is to
limit voltage.
The supplied
current by the charge source slowly increases battery voltage, as SOC also increases, this is called
BULK charging or CC.
Once the batteries have reached the chargers set point voltage (the voltage limit) all they do is LIMIT VOLTAGE, this is called
absorption charging or CV. If a charger has a further reduced voltage limit this is called
float charging. But again the charger is not "putting out a voltage" it is supplying
current and then
limiting the voltage to the preset level once the batteries get there.
So:
Chargers Supply
Current then as SOC increase enough they begin to
Limit Voltage. This is called CC>CV charging or constant current > constant voltage charging.
- Bulk = Constant Current (all the charge source can deliver in current - full bore)
- Absorption = Constant Voltage (voltage limiting)
- Float = Constant Voltage (voltage limiting)
So, in BOTH situations below, the combiner is engaged and both batteries are paralleled:
Nope....
#1 - while on shore power, if I'm using the house bank, the 5AMP AC charger can barely supply enough current to "keep up" with the current of the house devices (lights, pumps, etc) I'm concurrently using. And therefore neither battery is losing anything... in theory.
Either your charger
can keep up or it
can't keep up and this will be dependent upon house loads, SOC & the current potential of the charger, which at 5A is pretty small.. If it can keep up then the combiner will AUTO-BOTH the banks if the chargers supplied current EXCEEDS the house loads you are using and gets you to the AUTO-BOTH minimum voltage threshold..
Depending upon SOC the charger may or may not be able to get the batteries to the AUTO-BOTH voltage. The net charging current the battery sees determines how quickly the voltage will rise to combine levels. With a 1A net charge current it could take 50 + hours to attain an AUTO-BOTH voltage of 13.0V, and this is depending upon bank size & DOD. With a charge current of 50A it may take just a few minutes to attain 13.0V, again depending upon bank size and DOD.
All a
combiner/VSR/ACR does is
automatically do the same thing as the BOTH position on the switch or automatically PARALLEL or UNPARALLEL the banks. It does AUTO-BOTH based on voltage for both the combine event and the uncombine.
Voltage
rises to combine level = AUTO-BOTH
Voltage
drops below uncombine level = DISENGAGE AUTO-BOTH
#2 - while OFF shore power, but connected to a 1 AMP (15Watt) solar panel, the combiner will see higher than 13.3V and allow charging.... BUT i'm using 5Amps of draw with the house devics, and the solar panel is only capable of providing 1Amp of replenishment, so at this time, I'm draining BOTH batteries.
Unless Ohm's Law was re-written while I was asleep it still applies today..
Let's look at this from your batteries point of view. What does the battery see?
- -5A discharge current from house loads
Hi my name is
George 27 and I see a
-4A LOAD
If George 27 has a negative load on him of -4A then he is NOT CHARGING!!!!! He is DISCHARGING.
So now we know that George 27 is NOT
charging and he is
discharging. What happens when a battery discharges?
The voltage quickly falls below the AUTO-BOTH voltage and the relay OPENS and unparallels the batteries thus, under discharging conditions, you can not discharge two banks because the
voltage sensitive relay (VSR/ACR/Combiner) will simply open as voltage falls.
- Make/close on voltage rise, break/open on voltage drop.
Unless you can explain to me how situation #2 is untrue, and that while sitting on a solar panel, if my 1/B/2/OFF switch is on 1, and how I won't be using both batteries for house appliances at that point.
The battery is NOT CHARGING it is DISCHARGING.
It really is that simple.
Unless charge current
exceeds house loads then you are
discharging the battery. Even if charge current does exceed house loads the amount of current it exceeds the loads by will vary how long it takes to attain the AUTO-BOTH voltage. The less current you have flowing into the battery the longer it will take to attain the AUTO-BOTH voltage. The more current you have flowing into the battery the less time it will take to attain the AUTO-BOTH voltage.
If you had 40A of charge current but had a -52A house load you would still be discharging the battery at a rate of -12A.
With a 1A charge current and a -5A house load your net discharge is -4A..
Are the combiners one-way devices?
Is BOTH/ALL one way?
All a combiner/VSR/ACR is doing is automating or duplicating the BOTH/ALL feature of your battery switch. It does this based on
voltage rise or
fall.
When they are "ON", do the batteries actually see each other?
When the relay is made/closed the batteries are physically wired in parallel. When the relay opens/breaks the batteries are isolated or no longer in parallel/BOTH/ALL....
The key take away points:
- Chargers supply current and only limit voltage
- Combiners simply parallel/unparallel banks based on voltage
- You need net positive current for batteries to be charging
- The charge current rate & SOC determine how long it takes to parallel
- Under discharging conditions the combiner will open/break and isolate the batteries
