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mrpsychedelic avatar image
mrpsychedelic asked

Is there a way to fast charge a 24V Lifepo4 system everyday?

I have (3) 24V 230Ah batteries connected in paraell. I need to be able to charge them to 100% every night. Some days I may use up to 90% of the batteries.


I thought I had my shunt programmed correctly to the batteries SOC, but I must have been wrong. The batteries were dead with the shunt showing 61% left. The batteries were at 21.6V so defiantly dead. I am assuming they never charged to 100% to begin with.


I plugged them in and let them charge overnight, the next morning the 5k quattro was slowly putting barely any current into them so I assumed they were full. I then told the shunt hey this is 100% for 690Ah. With them dying at 60% left on the shunt I'm assuming they weren't actually 100% and the inverter was just going to slowly charge them the rest of the way. With the rate they were charging that would take like 24hrs for a full charge at minimum.

I'm using this set up for a mobile dog grooming van, so I'm going to be pulling some big power and 40% isnt going to be enough for a full day. Plus I paid for the whole battery I want to use it all lol.

Is there a way I can change the settings on the inverter to safely charge the batteries at a higher current to 100% so they can charge overnight in around a 12hr time? They wont always get drained super low, mostly in the summer when the AC is also running all day. Otherwise ill use 30-50% a day depending how busy and how many big dogs or dogs with a lot of hair to dry.

I've looked every where and I can't find any concrete answers. I don't want to damage the system or batteries, but I really need these to charge faster everyday.

battery charging
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

What batteries (exact type/brand)? Settings (Shunt, Quattro)?

Maybe a cell imbalance during charging/discharging causing to stop charging/discharging to early?

Can you "look into" the batteries with an app via bluetooth to see the cell voltages during charging/discharging?

Charging 690Ah over night (8-10h) shouldn't be a problem.

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mrpsychedelic avatar image mrpsychedelic commented ·

First time using this forum, I'm not sure if I was supposed to reply to the thread or your comment specifically. I will delete whichever was wrong.


Batteries are LiTime. I am currently using a basic shunt that just shows parameters, I went ahead an ordered a victron BT shunt incase I'll need to replace mine.

The settings I have currently are Absortion V - 28.4V, Float - 27.6V, Charge current - 80, AC 1 and 2 input 15A, Repeated absortion time - .25hr, Repeated absortion interval 7 days, Absorption time - 1 hour.



Is there a way to check for a cell imbalance without taking the battery boxes apart and testing individual cells?

Unfortunately the batteries have no BT function so I can't see what they are reading. I can only test with a volt meter.

My math was telling me from 0 at 15A charging I could do it in about 12-13 hours. That's why I'm not sure if I have a setting wrong that it trickle charges way to early, or what is going on. I do appreciate the help because I'm lost on what to do.
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Matthias Lange - DE avatar image Matthias Lange - DE ♦ mrpsychedelic commented ·

Without knowing whats going on inside the batteries its hard to tell.

The Quattro starts reducing the charging current after reaching the absorption voltage and stops discharging after reaching the programmed cut-off voltage.

You will need some time to do some tests.
Charge and discharge each battery individually and measure the current going in and out (for that you need a good shunt).
Maybe one battery has a problem causing the system to stop charging/discharging to early.

With 80A charging current you need 8-9h to charge 690Ah.

Or maybe the settings of your shunt are totally wrong and shows you the wrong SOC, while your batteries are empty/full.

What's your average current consumption? Does the shunt shows the consumed Ah?

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mrpsychedelic avatar image mrpsychedelic Matthias Lange - DE ♦ commented ·
I wish these batteries had a BT monitor to see what's going on with them inside.


I didn't see a setting to change any cutoff voltage in the parameter settings for the quattro. So I'm not sure what voltage is cutting off at

The victron smart shunt gets here tomorrow, so I'll replace mine with that, then disconnect the batteries from each other so that I can run each individually. What should I charge them and discharge them to individually? Also will the victron BT shunt tell me all the information I'm going to need?

The shunt could be programmed to the wrong 100%, but I know for 100% fact I didn't use even close to 690Ah to fully drain the batteries.

My average current consumption would be in the summer 100A an hour at 24V, winter would be around 50A an hour at 24V. The shunt does show how many Ah you're currently using and how many you have left.


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Matthias Lange - DE avatar image Matthias Lange - DE ♦ mrpsychedelic commented ·

1698778736050.png

(18,6V is the default setting and to low for most batteries)

If you charge the batteries individually set the charge current to 20A or lower and give the battery time for the cell balancing, charge until the current is almost 0A.

With 100A average you only have a run time of around 6h.

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1698778736050.png (58.5 KiB)
mrpsychedelic avatar image mrpsychedelic Matthias Lange - DE ♦ commented ·
My low input shutdown is set to 21.6V in that menu.


I can disconnect the batteries from each other now and charge at 14A, I'm on a 15A breaker. Then charge each individually until almost 0A are going into the battery, then disconnect the battery and do the next till all 3 are at that state, then reconnect all 3 and set as 100% SOC?

The summer I may have to run a generator to supply extra power. I haven't been able to real world test in the summer, so the 100 average is an educated guess. Based off running the AC which uses 50A and my dryer which uses 100, but that'll be used for usually 20 mins or less. Nothing else uses much power. And the AC may not run at 50A the entire time being used.

If I did use a generator is it safe to just plug it into my shore power connection, or do I need to wire up AC input 2 for the generator?

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ mrpsychedelic commented ·

Your 15A are the AC input current NOT the DC charging current!

You have to reduce the charging current if you charge the batteries one by one.

As snoobler mentioned with 15A at 120V the Quattro will limit the charging current to way less than 80A and the charging will take more time.

PowerControl will reduce the charging current even more if you have AC loads running at the output of the Quattro.

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mrpsychedelic avatar image mrpsychedelic Matthias Lange - DE ♦ commented ·
Correct me if I'm wrong, but the DC charge current for mine is the 80A I said earlier? I would change that to 20 to charge individually?


The quattro seems to limit it to about 50A for charging.

If I charge each battery separately then reconnect, do you think that'll solve this issue? If not I have no idea what else to try

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snoobler avatar image snoobler mrpsychedelic commented ·
Per my post above, if you're on 120VAC, a 15A AC input would be limited to about 55A.


Most LFP batteries can be charged at 0.5C or 50% of their capacity, so 50A per battery shouldn't be a problem.

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mrpsychedelic avatar image mrpsychedelic snoobler commented ·
With the inverter limiting it to 50A, wouldn't that be split 3 ways to each battery? I'm not sure that matters I'm just curious on the math behind that.


With knowing I'm limited to 55A, should I change the 80A setting to 55A, or leave it as is?


I really appreciate all this help guys. I'm completely lost on what the problem could be. All I can think is a bad battery or the cells arnt the Ah they were sold as. To miss out on 60% of the life seems more then just a bad battery


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snoobler avatar image snoobler mrpsychedelic commented ·
Yes. each battery should theoretically get 1/3rd of 50A.


I was just saying that you don't need to lower it if you charge a single battery.


The inverter will use both the charge current setting and the AC input limit setting to cap the charge at the lower of the two.



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snoobler avatar image snoobler mrpsychedelic commented ·

The settings I have currently are Absortion V - 28.4V, Float - 27.6V, Charge current - 80, AC 1 and 2 input 15A, Repeated absortion time - .25hr, Repeated absortion interval 7 days, Absorption time - 1 hour.

charge parameters are good.

80A * 28.4V = 2272W

Will require about 2700W AC input.

only one AC input can be used at a time.

15A * 120V = 1800W - not enough if you're on 120VAC. You'll be limited to about 55A.

15A * 230V = 3450W - should work if you're on 230VAC

690Ah will require 12.5 hours to charge from dead empty.


New batteries are almost always imbalanced to some degree, but it shouldn't result in more than a few % capacity loss. Daily charging to full and cycling should eventually balance them.


What gauge cable between inverter and battery?

What one-way distance?

Have you confirmed that each and every connection is properly torqued and of high quality (good crimp, no shrink pinched in the connection, battery cables in direct contact with battery and inverter terminals with no washers in the electrical path, etc.)?

Have you paralleled your batteries consistent with best practices to ensure each battery shares a proportional load/charge?

Have you read and followed Wiring Unlimited?

https://www.victronenergy.com/upload/documents/The_Wiring_Unlimited_book/43562-Wiring_Unlimited-pdf-en.pdf


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mrpsychedelic avatar image mrpsychedelic snoobler commented ·
I'm on a 15A breaker at 120V. Should I lower the 80A setting?


Also I only have the AC 1 wired. I don't have AC 2 wired. While I'm thinking about it, if I ever did hook up a generator, could I plug that shore power into the generator to charge or would that give me a problem?

So my math on charging was correct, so something else must be giving me an issue. I'm starting to wonder if it's 1 bad battery making them all act up.

I'm using 4/0 cable from batteries to inverter. One way distance is 5 feet.

All connections are solid. No wiggle room or anything. I don't have them torqued to spec though I will admit that. I'm not sure how big of an issue that could be

I didn't use best practices for parallel connections. I wired all 3 together right away and charged as a system. I didn't fully charge each individual battery separately then connect all 3. Could that result in this large of an issue?

I have no read that wiring unlimited yet. That's a lot to read I'll start reading now.

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snoobler avatar image snoobler mrpsychedelic commented ·

You don't need to read everything. Just look at paralleling batteries and making DC connections.

Is your main (-) connected to battery #1 and your main (+) connected to battery #3 or vice versa?

Next time you're charging, using a voltmeter, note the voltage at the inverter battery terminals and the battery terminals themselves. If you have significant voltage drop, charging will terminate early.

and yes, you should un-parallel the batteries and confirm they are at the same voltage as each other when disconnected.

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mrpsychedelic avatar image mrpsychedelic snoobler commented ·

Main battery #1 is connected to the positive and main battery #3 has the negative. With both of those wires being identical length with the shunt for negative wire and fuse block for the positive wire accounted for in the length.

I actually just checked the voltage at the battery and inverter while it's still charging. Both are at 26.7V.


Charging is almost at "100%". So I should disconnect the 3 batteries and test each separately?

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snoobler avatar image snoobler mrpsychedelic commented ·
main (+) and (-) don't need to be the same length. The cable interconnects between the batteries must be the same length.

Is it floating at that voltage?

How much current is flowing when you measure 27.6V at both locations?

How are you configuring the inverter?

What is showing "100%" ?

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mrpsychedelic avatar image mrpsychedelic snoobler commented ·
I didn't know that about the mains not needing the same length. I had all positive and negative wires identical lengths and every connection. It's not floating yet, it still says bulk charging. Should I wait to retest when the inverter switches to float?


50A is flowing when measuring 26.7V.


I'm using the MK3 connection to configure the inverter.


The shunt I'm currently using is showing 97.3% so almost to 100% full according to the shunt. I set the 100% level when the inverter charged all night a few months ago.

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snoobler avatar image snoobler mrpsychedelic commented ·
The shunt is wrong. If it's flowing 50A @ 26.7V it's not fully charged (probably in the 50-70% at most). It will be fully charged after the bulk/absorption phases finish, and it's floating at 27.6.
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wjf avatar image
wjf answered ·

@Mrpsychedelic It is also possible that your batteries are labelled with a higher capacity than what they actually have. The Victron shunt is very accurate and useful component to check this, providing wiring is correct and shunt is set up correctly......

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mrpsychedelic avatar image mrpsychedelic commented ·
Wiring and shunt are set up properly. I know for 100% fact i didn't use anywhere near the rated 690Ah. I have the BT shunt coming tomorrow. How can I use that to see if each battery truly has 230Ah?
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snoobler avatar image snoobler mrpsychedelic commented ·
You would have to charge and discharge each battery individually.
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mrpsychedelic avatar image mrpsychedelic snoobler commented ·
So should I wait to charge and discharge each battery until I get that shunt? I know we're talking all over now lol so I hope it all still makes sense. You can condense to one message if you like
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snoobler avatar image snoobler mrpsychedelic commented ·
I think you should allow the entire bank to fully charge until the inverter indicates float, 27.6V and little to no current is flowing to it.


Once you get the new shunt, install it and test the entire bank. If you get what you expect out of it, skip the individual tests and enjoy.


You have likely been inappropriately relying on an inaccurate shunt to determine 100%. If everything is configured/connected properly, you are fully charged when the inverter has cycled through bulk, absorpt and ends in float.


The victron shunt should be configured as follows:

Capacity 690

charged 27.2V

tail current 6%

Peukert 1.05

Efficiency 98%

Battery SoC on reset Keep SOC.

Leave others at their defaults.

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mrpsychedelic avatar image mrpsychedelic snoobler commented ·
It's still pushing 50A at 100% charge so that makes me feel so much better that it's just the shunt.


The victron shunt to get here overnight was the old version but that's okay, I just want to make sure I wire it properly. The Aux wire is for a temp sensor, that I won't have so I can cap that off right? Then batt obviously goes to the positive battery wire that I have this shunt wired to, and the VE direct I assume is a cat 5 connection that plugs into the other open port I have on the inverter itself. I have the BT smart dongle attached in one, I assume this goes on the other?

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snoobler avatar image snoobler mrpsychedelic commented ·

I don't see that you said which shunt you purchased. VE.Direct is for connecting to a GX device like a Cerbo. The shunt does not connect to the inverter.


If you got a smartshunt or a BMV-712, it has its own bluetooth.


The VE.Bus smart dongle is for the inverter exclusively so you can access it with VictronConnect for monitoring (no configuration changes except for on/off/charger only mode selection and changing the AC input current limit).


have you wired the sensing leads of the smart dongle to the battery?


1698785357426.png

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snoobler avatar image snoobler mrpsychedelic commented ·
Worth noting that shunts need periodic synchronization to maintain accuracy. it's possible that your existing shunt drifted over the months.
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mrpsychedelic avatar image mrpsychedelic snoobler commented ·
It just says victron smart shunt IP65. It's BT with 3 wires coming out of the side.


I have the smart dongle wired to the inverter, next to where the positive and negative wires are connected. Is that going to be a problem? The smart dongle has never given me any issues at least.

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