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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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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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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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snoobler avatar image snoobler mrpsychedelic commented ·
smartshunt IP65 is just a "waterproof" version of the standard smartshunt, so it will have bluetooth.


for the VE.Bus smart dongle, those sensing wires should be on the battery terminals per the figure.


Those wires provide the inverter a direct open circuit voltage measurement of the battery that is not influenced by charging or discharging. This gives more accurate results when charging and discharging.

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mrpsychedelic avatar image mrpsychedelic snoobler commented ·
I won't be able to install the new shunt for a few days, something came up so I'll be away from the van. When I do get to install it what should I be looking for?


I'll also switch the smart dongle wires to the batteries themselves. I assume positive on battery 3, negative on battery 1? Or vice versa but at least it's the whole battery system that way?

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snoobler avatar image snoobler mrpsychedelic commented ·

When you install it, install it in accordance with the schematics and program it as I indicated above. Not sure what you mean by "what should I be looking for?"


Wire connections made at the same place as the main leads.

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