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Old 12-30-2022, 04:21 PM   #1
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Lithium upgrade prep

Ordered 4 x 12V 100ah Amperetime LiFePO4 batteries.
Batteries will be series to 24V 200ah (4800Wh total).

In watching Will Prowse series connecting video, he mentions charging each battery separately to achieve proper state of charge, since voltage doesn't represent SOC for lithium batteries. And SOC is more important than voltage, apparently. This is a newer concept for me. I thought I could slap em in and let my solar charging system take care of em, business as usual.

Looks in the forums, that plug and play isn't really a great idea. I'm reading up on some posts and learning.



What's the proper order of operations here? Use a stand alone lithium battery specific charger (ones you plug into wall outlet), and charge each battery individually until....what? What voltage? Proper state of charge? What is ideal SOC? Will the charger do that on its own? It's what Will Prowse video suggested.

Guess I'll have to order a charger. What size charger to get? 50amp? 30amp?



What equipment do I need to safely charge, maintain, and discharge these batteries? I'm hearing things like diodes, SOC, etc that I haven't learned about yet. Don't want to mess up batteries, bus, equipment, or myself.




Equipment currently have: (24V)
-1100 W solar panel (88V)
-CAE MP-60 MPPT 60a charge controller 12V/24V/48V compatible
-Edecoa 3000W pure sine wave inverter
-Victron BMV-714 battery shunt + monitor

These all state compatible with lithium.

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Old 12-30-2022, 04:28 PM   #2
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This is an interesting question. I am just as curious as you, but I have a feeling it amounts to how far down the lithium rabbit hole you want to go. Will the batteries work fine and have a reasonable service life if you just hook them up and go? Sure. Will you get absolutely every last drop of energy from them and truly optimize their performance without charging each battery for proper SOC? Maybe not.
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Old 12-31-2022, 08:08 PM   #3
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Lithium Batteries

You absolutely must have a Battery Management System to charge and maintain Lithium batteries. The big question is this for a bus? The absolute best value remains lead acid, Absorbed Glass Matt for zero maintenance and long life. 20 plus years, lithium is when weight matters, like in your cell phone or an electric vehicle. Not my opinion just reality
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Old 01-01-2023, 05:49 PM   #4
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Quote:
Originally Posted by Kwest364 View Post
Ordered 4 x 12V 100ah Amperetime LiFePO4 batteries.
Batteries will be series to 24V 200ah (4800Wh total).

In watching Will Prowse series connecting video, he mentions charging each battery separately to achieve proper state of charge, since voltage doesn't represent SOC for lithium batteries. And SOC is more important than voltage, apparently. This is a newer concept for me. I thought I could slap em in and let my solar charging system take care of em, business as usual.

Looks in the forums, that plug and play isn't really a great idea. I'm reading up on some posts and learning.



What's the proper order of operations here? Use a stand alone lithium battery specific charger (ones you plug into wall outlet), and charge each battery individually until....what? What voltage? Proper state of charge? What is ideal SOC? Will the charger do that on its own? It's what Will Prowse video suggested.
Everything I know I learned from Will Prowse, so this is just a regurgitation.

I think the point Will is making is when you connect two 12 volt batteries in series to get 24 volts, you won't be able to tell if one battery is charged less than the other by looking at the combined voltage. When they discharge, the weaker battery will discharge to a lower state of charge than the stronger battery, and when they charge up the stronger battery will be more likely to overcharge. This is true with both lead acid and LiFePo batteries.

Batteries in Parallel naturally balance their charges; batteries in serial connection (which you need with two 12v batteries to achieve 24v) have no natural way to similarly balance each other, and without first confirming each battery's capacity and then bringing all batteries up to full charge you risk damaging one or more within the serial pair from over or undercharge.

To avoid the problem initially, you need to charge each battery up individually to their maximum recommended voltage (usually 14.2-14.4 volts but check your battery specifications). This ensures both batteries start with the same state of charge.

Then for each battery, put a load on the battery and monitor your amp consumption (through your shunt) down to about 13 volts, or close to 90+ amps consumed, whichever comes first. That tells you about how many amps capacity your battery actually has, which should be close to its rated capacity. You don't want to draw down too deeply-leave some amps in the battery-they are happier if not fully charged or fully discharged.

Then one time charge the batteries back up to the max recommended voltage and set your shunt to show 100% state of charge. At this point both batteries will be at the same state of charge and less likely to draw on each other when at the upper or lower extreme of charge.

Along the way, note the voltage that corresponds to ~15% and ~85% charge-15 amps and 85 amps. These will be your upper and lower voltage settings for your charge controller.

As you note LiFePo batteries don't provide state of charge information between about 13v-13.5 volts (each battery is a little different). They could be anywhere from 15% to 85% charged in this voltage range.

The good news is if you start with both batteries at parity and keep the LiFePo battery charge between about 15%-85% state of charge, they will probably be at voltage parity most of the time.

I want to emphasize that you need to research and experiment with your batteries to determine the voltages corresponding to those values; additionally do some YouTube research to see what others' opinions are about min and max state of charge to come up with your own settings for optimal battery life-some say 20-80%, others 10-90%.

With four batteries, each pair of serially-connected batteries balances voltage with the other pair safely, so as long as each pair starts being equally and fully charged, the two pairs will balance each other.

If you stay somewhere between 15% and 85% charge, that is, if you set your solar charger to maintain battery charge between the lower and upper voltages that represent these states of charge, your batteries will be much less likely to find themselves where that imbalance state exists ('staying between the shoulders').

I would also recommend getting a few cheap voltage displays and connecting them up to each of the batteries so you can see the individual battery voltages in case over time you have a bum battery.

Your batteries have built-in BMS's so they do their own monitoring of the individual cells in each battery-no need to worry about cell balancing since you don't have DIY LiFePo batteries.
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Old 01-04-2023, 03:27 PM   #5
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You should charge them individually before series or parallel connecting them to ensure that they are at similar SOC. I know that some of the manuals for the batteries state this; I couldn't check the AmpereTime manuals because they seem to have put them behind a authentication-wall (WTF!?)

By the same token, "plug and play" can work with these batteries since they have integrated BMSes, which will prevent "bad sh*t" from happening...
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Old 01-04-2023, 03:38 PM   #6
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Lifepo battery pre charge

Your batteries will have a battery management system inside each battery.
I've used my sollar panels to charge each battery separately until the batteries BMS says it is 100%. Then wire them as wanted. It is easier on the BMSs is they all start at the same charge and starting at 100%. Is what the BMS requires to start reading good from the get go. I don't know your battery but if they can communicate to each other that is real helpful for equal battery draw. Will Prowse knows what he's talking about. But topping up is topping up. Solar A/C charger it's just current. Oh and I must disagree with Unpluggedone lithium at the moment is the cheapest per watt pet life of the battery to go. In the future I think lithium will be looked back at as the 8 track. But until then lead acid is a reel to reel.
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Old 01-04-2023, 04:57 PM   #7
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If you want to parallel batteries you have to be very carefully. The internal resistance of lithium is very low. That means that the resistance of the parallel connection between batteries have to be way lower to ensure that each battery is loaded or charged with the same current..to make very low resistance connection is an art..

For that reason it is better to have cells in series to get to your voltage and then parallel the batteries..
The internal resistance is now larger... 4 cells in series plus the cell inter connections.
As a result the the internal resistance from the parallel wiring will be relative small and this a better current sharing is realized.

In electronics every power transistor in parallel has a small resistor added in series to ensure that both transistor dissipate the same amount and each transistor shares the same current.

Good luck
Johan
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Old 01-13-2023, 03:30 PM   #8
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Quote:
Originally Posted by Unpluggedone View Post
You absolutely must have a Battery Management System to charge and maintain Lithium batteries. The big question is this for a bus? The absolute best value remains lead acid, Absorbed Glass Matt for zero maintenance and long life. 20 plus years, lithium is when weight matters, like in your cell phone or an electric vehicle. Not my opinion just reality
I don't think an "absolute best value" can be stated without knowing a lot more about a setup. Things such as daily total power draw needed, maximum draw (and length of that draw) required, solar panel capability, and total watts in the battery bank.
While our battery bank could have been done with lead acid, it would have required 16 6 volt, 205ah golf cart batteries. USED locally these can be obtained for $90ea plus a $20 core for a total cost of $1760.

They weigh about 65 pounds each (without cables and racking) for 1,040 pounds.
They would take up a LOT of space.
And they're starting out USED so figure replacement at max 4 years.


For about $3,750 we obtained TWO 24 volt, 200ah (5.12kWh) lithium batteries. Our bank is wired in series to provide 48 volts to our inverter and has a capacity of 10.24kWh. The bank weighs just 202 pounds and takes up a space of approx 20x20x13". The built in BMS integrates with our inverter and it's charger using a single small communications wire, and can take up to 200amps of charge though 60 is recommended.
Our 2900W of solar has a theoretical 60A @ 48 volts so we should be good to go there.
What makes its bang per buck look outstanding is the 7,000 cycle design life.....that's 19.5 YEARS.
Now how many lead acid batteries are going to need replacing in 19.5 years?


Best bang for the buck? Lithium! Minimal if any maintenance, unlikely to need replacement, and likely to add resale value when you dispose of a lithium powered rig.
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Old 01-13-2023, 06:54 PM   #9
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Quote:
Originally Posted by Kwest364 View Post
Ordered 4 x 12V 100ah Amperetime LiFePO4 batteries.
Batteries will be series to 24V 200ah (4800Wh total).

In watching Will Prowse series connecting video, he mentions charging each battery separately to achieve proper state of charge, since voltage doesn't represent SOC for lithium batteries. And SOC is more important than voltage, apparently. This is a newer concept for me. I thought I could slap em in and let my solar charging system take care of em, business as usual.

Looks in the forums, that plug and play isn't really a great idea. I'm reading up on some posts and learning.



What's the proper order of operations here? Use a stand alone lithium battery specific charger (ones you plug into wall outlet), and charge each battery individually until....what? What voltage? Proper state of charge? What is ideal SOC? Will the charger do that on its own? It's what Will Prowse video suggested.

Guess I'll have to order a charger. What size charger to get? 50amp? 30amp?



What equipment do I need to safely charge, maintain, and discharge these batteries? I'm hearing things like diodes, SOC, etc that I haven't learned about yet. Don't want to mess up batteries, bus, equipment, or myself.




Equipment currently have: (24V)
-1100 W solar panel (88V)
-CAE MP-60 MPPT 60a charge controller 12V/24V/48V compatible
-Edecoa 3000W pure sine wave inverter
-Victron BMV-714 battery shunt + monitor

These all state compatible with lithium.
I watch Will Prowse also and from my understanding that you should fully charge lithium batteries with a lithium battery charger to 100% SOC and then set them up the way you want them. This was, you know that they were fully charged and should have similar SOC amongst the batteries.

This is what I did in my setup and so far, I haven't had any issues and am loving the new setup with lithium (3 x 24V x 200 ah in series). Have been truly a game changer for me!!
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