So you own an energy system that operates on batteries, and you would like to understand
a bit more about what's happening during discharging and charging. What does it mean, all those charging stages, the bulk, absorption, flow, equalization
What kind of voltages should you see? When is your battery full? When do you need to equalize
And possibly, what should you do to improve the performance of your system, extend the
lifetime of your battery? Well, in this video, I'll explain to you what's happening during the discharging and discharging
stages of your battery, and by the end of this video, you'll understand what is supposed
to happen and what to look out for in your system. I'm Jesse
I'm a renewable energy engineer. I've worked in the industry for several years, and I've run companies in the design and installation
of off-grid, battery-based solar energy systems, and I've recently held a position of energy
officer for the United Nations. I founded the company Solar Solution, through which I share my knowledge and expertise through
online videos, articles, and through personal support on my website. In the first topic, we'll describe in a few sentences how a battery actually works
In the second topic, we'll run through a couple of the values that we normally use to describe electricity
In the third one, we'll look a little bit more into depth, into the charging algorithm
different steps, the voltages, the battery charge percentages, etc. The number four is a bonus topic because I'm getting a lot of questions about equalization
I think it's good that I explain you a few basic principles about it
By the way, to keep the size and the content of this video manageable, we'll only look
at the lead-acid-based batteries. So this includes the flooded lead-acid batteries and the self-regulated lead-acid batteries
including the HGMs and cell batteries. Okay, let's get started. The first topic
What is actually happening in a battery? A battery takes energy in the form of electricity and stores it into chemical energy
Now what I would like you to remember about this is that if you take the electrical energy
and turn it into chemical energy, the conversion ratio is not 100%
It's always a little bit less. And if you discharge it, you take the chemical energy and turn it into electrical energy
also the sources are not 100% efficient. So I'm mentioning this to you because it makes it easy to understand why charging and discharging
of batteries is just not 100% efficient. That is also one of the reasons why batteries just don't last forever
Okay, that's enough about batteries. Let's look at the units that we normally use to describe electricity, and I'll mention three
The voltage, the amperage, and the pulse. Now, when I was a kid, I was fooling around with electricity, and I couldn't quite understand it
So what my dad did, he explained it to me by using the example of water in a garden hose
Now imagine that you're going to wash your car, you've got a garden hose in your hand, you close the end off, and you try to pinch the hose, and you feel a certain pressure
Now this pressure is similar to the pressure of electricity, and electricity would describe
it as a voltage. Now if you would open the nozzle completely, and you let the maximum amount of water flowing
out, the amount of water flowing out is similar to the amount of electricity, which is described
as amperage. Now you want to spray some dirt on your car, so you would squeeze the nozzle a little bit
it is a powerful jet of water. Now this powerful jet is similar to the power of electricity
And therefore maybe it's easy for you to understand that power is the result of pressure and flow
it is the result of voltage and amperage. Okay, so now that you're fully up to date with those two topics, we can look at the
charging stages, being bulk, absorption, and flow. So the first stage is bulk, in which the battery is typically less than 80% charged
Now in this stage, we generally allow as much power to flow into the battery as possible
as long as we meet two different conditions. The first one is that the amount of electricity flowing into the battery, being the amperage
should typically not exceed 20% of the total amp-hour rating of the battery
So the second one is that as we push this energy into the battery, we don't want the
pressure of the battery, so the voltage of the battery, to go beyond a certain level
This level is described as the absorption voltage, and it's set in your charger devices
That brings us to the absorption stage. If, as a result from the charging in the bulk stage, the pressure in the battery has reached
the absorption voltage, the absorption pressure, your charging device will now restrict this behavior
What it will start to do is it will start to maintain this pressure, this voltage in
the battery. It can reach the end of absorption either when a certain time frame has been set, for
example, two or three hours maximum absorption time, or secondly, it can end the absorption
when the amount of power that you need to push into your battery, the amount of amps
required in order to maintain your absorption voltage, falls below a certain preset value
At this point, you've reached the flow state in which your battery is as fully charged
as it can possibly be, and the voltage will be lowered to a more moderate voltage setting
which is the flow voltage. Now, I'm intentionally saying that the battery is as full as it can possibly be, because
it doesn't mean that your battery now has the capacity that it had when it was new
It just means that you have charged it as full as it can under the current condition
For the specific flow voltage for your battery, I'm going to say the same as for the absorption voltage
Now, let's test case you look in it, because it really depends which battery you have
but typically it is between 13 to 14 volts. Now, if you forget everything else in this movie apart from this one, I'd be very happy
You would preferably want to reach flow states every day. Less ideal would be every four to five days
Less than that, and you'll probably be expecting the lifetime of your battery
Now, one last thing, and it's a tip specifically for both an RV owners
What you normally see is that you've got your panels mounted somewhere on your deck or on your roof, your batteries are down in the bilge, your lockers, or somewhere under your
RV, and you've got your charge controller mounted in a convenient spot for you, so that
you can read out the charging state or whatever's going in and out of your battery
But what you should be aware of is that where your batteries are stored, the temperature
can fluctuate significantly due to the sun or the engine or whatever reasons, but as
the temperature from the battery changes, you should also adjust the voltage in order
to squeeze out the maximum lifetime of the battery. But a good thing is that your charge controller can do this automatically
It measures the temperature and then adjusts the voltage accordingly. The tricky thing is that if you've got your charge controller and your batteries mounted
in separate locations, your batteries can become boiling hot, but your charge controller
thinks, ah, I'm fine, I don't have to adjust the voltage. So how do you fix or improve this
Either way, you can install your charge controller in the same temperature zone as your battery
or if your charge controller allows for it, you can connect either a hardwired or a wireless
temperature sensing device between your charge controller and the battery itself. Okay, so the last topic, equalization
So as I mentioned in the beginning of this video, the charging and discharging of batteries
is never 100% perfect. And on top of that, you know, sometimes you can just not manage to get your batteries
into slope regularly. Now, there is a quick and dirty solution for this, which is called equalization
During equalization, the battery voltage will be raised to a very high level for a certain
amount of hours. So what happens during equalization is that bubbles are formed on those two plates that
I mentioned earlier on in the video, and those bubbles will blow off any kind of hard
sulfur particles that might have formed on the plate itself. Those particles will fall down on the battery
So what those bubbles will also do is that they'll mix up the electrolytes in your battery
and they'll distribute it evenly throughout. Now, you can imagine that these bubbles will not only blow off the sulfur particles from
your plate, but they might also blow off some of the actual lead on your plate, which will
just fall off, go to the bottom of your battery, can never be recovered, or actually then reduce
the overall capacity and lifetime of your battery. Now, as I said, the bubbles normally mix up the liquid, the electrolytes in your battery
But if your liquid is absorbed in a glass mouth, an AGM or a gel battery, then this
doesn't work really well. So typically, AGM and gel batteries do not require and are not allowed to be equalized
Okay, so I hope this gives you a basic understanding of what's happening during the different charging
phases in your battery. If there's something else that you would like me to present videos or articles about, let
me know in the comments below, and I'll use it as inspiration to produce more content
And as always, you know, if you like this video, I'd really appreciate it if you can give me a thumbs up, and it keeps me motivated, and I'll see you in the next video