Battle Born Charging

First you need the battery to be truly full, then you set the AH counter to zero. The battery capacity in AH is a variable, so the counter can lose count quickly and needs to be reset fairly often to be useful.

EG with AGMs at 32F capacity can be 15% of what it is at 77F. That's after whatever the battery has lost due to age or neglect.

You must have a "marker" to tell you when the battery is full so you can reset the AH counter. I do not understand why it is so hard to get a straight answer agreed by many sources on just what that marker is for Li batts. We have that for other types of batts used in RVs.

When you actually stop the recharge for an Li bank depending on whether you are camping at the time or at home is another matter entirely, and info on that varies as we have seen.

Not my problem. :( You guys with Li batts can sort it out. I would hope at least you can see from this thread that there is conflicting/confusing info so you might need to get clarification so not to lose your expensive investment earlier than expected.

@BFL
How do i know when my battery is full?????
When my battery capacity monitor reads 100%
There's probably other ways of knowing that I'm unaware of.
I
I posted 2 YouTube links below picture that show you how to set up a cheap Chinese battery capacity monitor.


https://youtu.be/YNQvWcmKuBw

https://youtu.be/E6O76Okmt08

Seems there are some parallels with obsessing abuot finding the perfect lead acid 3 or 4 stage automatic charger for battery X, and then becoming used to achieving full charge, with considerably less effort, when using an adjustable voltage power supply, and knowing in general how long it will take..

The adjustable voltage power supply allows a precision not possible with 99$ of things labelled 'smart', and the hassle of trying to get the 'smart' to do automatically , what the human mind and fingers can accomplish in a half second, makes one question why it had to be 'automatic' in the first place, especially when it misses 'ideal' 9 times out of 10.

Mobilesport and others, thanks for sharing your experiences actually cycling and using this battery chemistry with various degrees of BMS deployed.

Regarding my recent off topic alternator failure, it was nice to see the amperage load, the voltage held providing that load once it failed, from the driver's seat at 65mph, and deduce that I could easily keep driving to my destination, and worry about it later.

If some battery/alternator light started flashing instead with no ammeter revealing rate of discharge, I would have been tempted to pull off and investigate then and there, but it was late at night on a weekend, and that's the last thing I would want to do.

.

I read that with interest. He seems to go with the 5 amps is full idea for Li. Like the 4-5% idea in that other ref.

" Why 5 amps and 13.6 volts? Because 5 amps on a 100 AH Pb and LFP is the point both batteries are fully charged."

However he is out to lunch on 5 amps being full on a 100AH lead acid battery of course. EG it is 0.5a/100AH with AGMs. 2-3% is often quoted as being full for flooded batts--if you believe that. (To me full is 100%.) He does not make clear whether that acceptance rate of 5 amps is at 13.6 or 14.4 either, which matters a lot.

So I don't know how much to trust him on Li when he says that about Pb. Again, it does not matter much what I ever figure out; it should matter to those who actually have or will buy Li-ion batts for their RVs.

They are the ones who should be taking over this thread IMO.

OMG, my head is about ready to explode! - time to create another Gov’t agency - lol

BFL13, I can't explain in the techno gargin answer that I believe you're looking for.

Here is a thread from another forum that might answer the question that we're not wording properly or explaining very well other than it works. :)

From this thread....post 16 (into the weeds at your own confusion)

https://www.solarpaneltalk.com/forum/off-grid-solar/batteries-energy-storage/lithium-ion/369050-what-happens-between-ovd-and-clv-values-of-a-controller

"...Not exactly, you still do not have your head wrapped around what Bulk, Absorb, and Float are.

There are only two charge modes of either Constant Current or Constant Voltage. Bulk, Absorb, Float, Equalize, Refresh are all just confusing terms to make a consumer confused.

Bulk is constant Current, all the rest are Constant Voltage. If you were to buy a Float Charger for lead acid, or CC/CV for lithium is the exact same charger. Both have a Bulk (CC) ,and Float (CV) stages. All modes be it Bulk or whatever stage you want to call it like Hocus Pokus have a voltage set point. For a 4S lithium and Pb is 14.4 volts. Absolutely no difference. When you connect a charger, let's say a 20 amp charger, to a discharged battery of let's say 12 volts. When you connect the discharged battery you are not going to see 14.4 volts. Nothing remotely close to 14.4 volts. For demonstration purpuses let's say both batteries are 100 AH, and each has an internal resistance of .02 Ohms. From here it is simple math.

Battery Under Charge Voltage = OCV + [Ri x Charge Current] We already defined OCV of 12 volts or a fully discharged battery, and with a 20 amp charger (C/2 on a 100 AH battery) you will initially only see 12 volts + [20 amps x .02 Ohms] = 12.4 volts. The battery OCV forced the charger to become a Constant Current source. The Charger has a current regulator that will not allow it to deliver more than 20 amps. As the battery charges up, the OCV will rise and continue to rise for 4 to 5 hours. When the OCV of the battery is 14.0 volts, will begin the Absorb Phase. When the battery OCV reaches 14.1 volts there will only be 14.4 - 14.1 volts / .02 Ohms = 15 amps. At 14.2 is 10 amps. At 14.3 is 5 amps. At 14.4 both charger and battery OCV are equal and current stops.

Nothing magic happened, nothing switched on or off. It is pure Ohms Law of voltage and resistance relationship. Now we can add a circuit to do something like change the Voltage Set Point or Turn the Charger Off. Example we add a current measurement with some simple logic that says if Current = 5 amps or less, we do something. One thing we can do is lower the Voltage to say 13.6 volts and call it Abracadbra. No lets call it FLOAT so we fool John Doe homeowner. Sounds better. Why 5 amps and 13.6 volts? Because 5 amps on a 100 AH Pb and LFP is the point both batteries are fully charged. If we were to hold 14.4 volts on either battery would be an over charge. On Pb battery we would gas the batteries and corrode the plates. On a Lithium battery becomes unstable and plating lithium metal onto the anodes.

So you roll the voltage back on both. When you do that the Surface Charge on the plates will bleed off and hold at full charge. Any power demands from that point come from the charger if it remains. However very few chargers made for lithium will fall back to a lower voltage. They shut off.

Now if you were to watch the voltage on a PB and LFP battery, you would see they are not alike. A Pb battery would be a nice straight slope slope from 12 to 14.4 volts. On a LFP would look radically different like the slope you seen in Karrak's graph. It would jump up very quickly from 12 volts to 13,2 volts and pretty much stay there struggling upwards to 13.6 volts when it reaches about 90% SOC, then shoots up real fast that last 10% to 14.4 where you do not want to go.

Solar is a piss poor choice to charge LFP batteries because the charge current is unknown at any point in time. That means you cannot use a current trigger. Your battery could be 50% SOC at noon with only 5 amps and falsely trips the circuit because a cloud or haze passes over. There are no charge controllers that can work properly with Lithium. It takes an external control, a **** BMS. So what do you do? Simple choose 1 voltage of roughly 3.4 volts and allow the battery to saturate and FLOAT. That would be 13.6 volts on a 4S battery.

So far you are not ready to do anything. You have not balanced your batteries. Until you do that, you are spinning your wheels and risking damage. Decide Top or Bottom period. To do that you must connect all cells in parallel and walk away for a few hours. Then either discharge them to 2.5 volts, or charge them to 3.65 volts. Take your pick. Once balanced, lithium batteries do not go unbalanced quickly unless you have a BMS or Voltage Monitor taps. Those wil be a parasitic loads of uneven current draw. Both my Ev's only need balanced about once a year. If your batteries are in good shape has a self discharge of about 1% a month. Some maybe .8% and some 1.2% a month. So it takes a long time for any imbalance to occur. If you TOP balance periodically check cell voltages. All should be within .01 volts at the TOP. If you Bottom Balance should be within .01 volts near the bottom.

Now here is the difference betwen Bottom and Top Balance. With Top Balance the only thing that is known is 100% SOC. It does not tell you what capacity the pack is. Chi-Com cells especially Winston cells are notorius and can be +/- 10% of rated capacity. So when at 100% SOC you can have one cell at 90 AH and another at 110 AH which means you only have a 90 AH pack. That 90 AH pack i sin real danger of being over discharged. Th eother 3 cells wil eat and destroy it if the cell voltage goes to 2.5 volts or less."

There is no reason to somehow worry about perfectly exactly 100.000% full.
97%, 98.5%. 100.2% is all fine and all considered full, done and ready for use.

Also there is no buffer of electrolysis so just stop and call it done.

Ok but when is it "full"? That picture actually says to charge it until it reaches the target voltage and stop.

That would be at the end of the Bulk stage/start of the Absorption stage.

BB says to go another 20-30 minutes after that to get to full.

And are either of those the same as when amps taper to 4a per 100AH? Not the first, since that is when amps are just starting to taper.

I remain confused.

EDIT--when you reach Vabs, amps are still high so there is some voltage drop between battery and charger. You have to be sure you are reading battery voltage, which will still be under your 14.4 charger voltage because of that voltage drop. It is not easy at that point to measure true battery voltage while you are still charging.

The way to tell you are at the start of Absorption is when amps start to taper. This is "close enough" to when you reach Vabs to use as your marker. if you wait until battery voltage is 14.4, same as charger voltage, amps will be down to zero so no voltage drop.

BFL13 wrote:
Well, I find it all very confusing, so it is a good thing I don't have an Li-ion battery.

Way simpler then you think.
I posted a picture after all my text.
In this picture is all that you need to know.
In this picture they talk about the three important things.
I'll try to define them.

1: target voltage is the voltage you set the charger up to , for example my battleborn manufacturer says it needs to be charged at 14.4 volts so I dial my charger to 14.4 volts , they call that the target voltage. That's it , that's how simple!

2: duration of charge source
All this is is the amount of time you charge !
Don't charge past 80% soc
That is it , that's how simple it is!

3: charge rate
Charge rate is just selecting the right amount of amps of a charger!
For example i have a 100 ah battery and so my ideal charge rate charge rate is about a 50 amp charger.
That's it , that's how simple it is.

Them 3 things is all you need to know.
Plus I would add one more thing
Don't drain your battery below 25% soc

In this picture read the very last sentence, they tell you how easy it is to charge Li batteries.
Always keep in mind that the three important things they talk about in this picture is all you need!!!!

There's people that have alot of knowledge about these batteries and they speak alot of technical jargon , they can go way deeper in info then you would ever need.
Alot of people build there own battery and I envy those people but there's a simpler way , the battery manufacture did all the brain work for you.
You can buy a plug in play battery , your done!
Ain't that complicated.
People can complain about price but how many hours are you going to spend online trying to figure out how the inner guts of the battery work.
It takes massive amount of time to learn all that technical sub details.
You could spend that time instead getting a part time job flopping the money down on a ready to go battery .
It's easy
You buy a drop in battery
Wire it up
Use energy
Charge and put energy back into it
repeat.
Follow the three simple things they talk about in the picture and your battery will last a long time
Picture below