His statement is partially true, but only up to the point that the battery reaches its absorption voltage. This voltage is set by the controller, maybe 14.1 for gels, 14.8 for open lead acid. Up to the absorption voltage the current is constant as the battery voltage rises - controlled by the charge acceptance of the battery. At this point the battery stays at this voltage and the charge acceptance of the battery then determines the rate of the falling charge current. After a set time and or current and or other parameters programmed in by the engineer that designed the system, the controller switches to a much lower float voltage.
Most people don't understand how voltage or current sources work, most people don't actually understand how negative feedback regulation works. Most don't understand how a smart charger
How could they no manufacturer provides a proper description of what actually happens. So people trot out manufacturers descriptions as if it's the actual science.
Have any of you actually logged on a data logger the actual current and voltage waveforms of a typical LA charge cycle. Have you compared them with the silly stylised IUI drawings that get published by manufacturers.
The terminal voltage of a battery is a function of the division of impedances between the charging
sources and the battery. If you draw out a simple equivalent circuit of a battery under charge and power it with a simple imperfect voltage source you'll see what I mean. In fact put the who,e thing into spice and model it.
Yes I find it hard to use words to describe technical things normally I would use drawings and formulae
Let's consider the charging
cycle. There is a bulk mode and an absorption mode. ( float mode is somewhat of a construction) there is no abrupt transition between the two modes.
In bulk mode the input impedance of the battery is so low compared to the charging sources that they cannot set the terminal voltage ( look up potential divider circuits) the battery is basically the sole arbiter.
So in bulk mode the charging circuit is faced with a virtual short circuit. It runs as a constant current source. Ie the voltage is determined by the circuit characteristics . It typically uses a current foldbsck to do this.
As the SOC rises an LA battery rases it voltage , the equivalence is it impedance rises. Hence the terminal voltage will rise. Now LA has an unfortunate characteristic that it will Subject to enough power boil its own juices. So a charger
manufacturer ensures that the charger regulates the voltage in absorption. This is do e by in essence throttling the current so that the voltage doesn't rise. Ie the charger various it's output impedance to slowly disconnect itself from the circuit as the change cycle finishes.
Yes it's true that some chargers use several "tricks" to determine when the battery is full , many don't they just ensure the voltage doesn't rise too high and eventually the battery stops accepting current. ,
Float mode is merely in effect increasing the output impedance of the charger to allow the battery voltage to settle down at a lower voltage. It's the battery that's lowering the voltage not the charger. ( think about it , no charger is a current sink, it cannot "force" the voltage into float mode. La batteries float when you remove loads from them.
This is where the English
gets twisted people talk about the " charger switching to a lower voltage" even EEs use these types of terminology of course wer,e supposed to know what actually happens.. The charger can't " switch to anything" it's a function of battery chemistry what happens. Few chargers are much smarter that that , some use charge current as an indication. Some run a coarse timer some do nothing.
So of you consider multiple charge sources. ( and I specifically exclude bang bang solar
regulators. As they are a different technology that takes advantage of the PV constant current idea) they don't interact per say. If the battery needs to stay in absorption mode ( because current is flowing into it) then one of the sources will oblige. The other sources for example can't enforce float mode ( again no current sink) all that happens is the non active sources are in effect high resistance.
As I said one or more sources will contribute it just you cant tell in advance what one. But it will not stop your battery from being charged.
As to manufacturers recommended views , well they have to take the view that on a typical self install product all their customers are technical idiots and that's because most are. They don't want or can't explain the technical issues so they make blanket statements.
The practice is in the eating I've regularly run multiple sources ( two alternators , a big smart charger and before a wind
Jenny ) all worked fine together. By fine I mean they didn't explode. It's was just that with the characteristics of the wind
unit it tended to want to finish the batteries. So you could wasted running time turning over charge sites that didn't do anything.
I'm sorry if the words are convoluted. Yes there maybe some controllers that do strange things , but in general they all o eh the laws of electrical
For example one of the stupid things I've seen is delayed switching from float to absorption. Some battery chargers will not return to absorption mode from float unless they go back go bulk mode first. This means that say a wind gen can cause a funny
situation where in a gust it takes over absorption mode and then after the gust the other charger will not reengage until it sees bulk level voltages. This is not interfering. It's more the consequence of a particular design feature. The charging sources can still all remain connected. Wind generation in my view is not well suited to finishing a battery absorption mode