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clive87 avatar image
clive87 asked

How to Battery Protect against Low Discharge with Inverter

I have a Victron Multiplus 12/1600/70 connected to a Champion LiFePo4 200Ah. The object is to provide uninterrupted power to a small apartment. So next step to wire it into the DB.

However when testing the battery discharged all the way to 8V in a single night (the mains power interruption was longer than expected) Now the battery is either ruined or in sleep-mode and I cannot fix it. I have another battery but too scared to use it now.

How do I guard against this in future??

I ordered a Victron 12/24V-65A Battery Protection unit but how do I wire it?

Battery Protect
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10 Answers
Alexandra avatar image
Alexandra answered ·

@clive87

The battery protect is unidirectional. Meaning is cannot charge and discharge through it.

What you can do is set the inverter to switch off on battery voltage and SOC. Set your system to shut off around 10% SOC min to allow for cell imbalances at lower soc.

The victron 12v charger should wake up the other battery.

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clive87 avatar image clive87 commented ·

All I can say is I am deeply disappointed - what is the purpose of low cut off protection if it will not work with an inverter? I have now ordered two of these devices based on the marketing Gump that comes with them and for nothing.

As for set the inverter set to "switch off on battery voltage and SOC." - How on earth is that done?? My Multi has no buttons or access panel as far as I can see??

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Alexandra avatar image Alexandra ♦ clive87 commented ·
@clive87

It is designed for DC loads off a battery bank. One that an inverter does not control. It is to have a low cut off function like the inverter does.

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ejrossouw avatar image ejrossouw clive87 commented ·

Not sure about the "marketing Gump" as below it actually explains this clearly on the Victron product pages. This was also done, given if used incorrectly, there could be serious consequences.

https://www.victronenergy.com/battery_protect/smart-battery-protect

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Fideri avatar image Fideri commented ·

@clive87

Did you resolve the batt issues? Is your "Champion" battery the type sold by David and Shirtliff in East Africa? I have trouble with my PylonTech batteries.

Fideri

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clive87 avatar image clive87 Fideri commented ·
long story short - I purchased the victron remote view thingy and SET my system to auto cut off at 10% SOC. I then physically TESTED it and it worked like a dream with the remaining Champion. Victron is high end but complicated and frustrating.

The remaining Champion was determined to be faulty and I am still awaiting a replacement.

The system is now installed with the functional battery and it runs lights, fridge, fishtank heater, x 2 PC's wifi etc without a murmur right through 6 hour power outages.

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clive87 avatar image
clive87 answered ·

Come to think of it - is there not supposed to be a default low discharge cut off at about 11V??

How did my battery end up at 8V??

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Alexandra avatar image Alexandra ♦ commented ·

@clive87

Battery could have shut down because one cell fell below its low cut off. So had a deeper discharge than the others.

Alternatively the battery has a fault.

8v is just what the battery outputs in its protected state. Not necessarily the voltage of the pack

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clive87 avatar image
clive87 answered ·

The victron 12v charger should wake up the other battery.

The Multiplus IS a 12v charger - not? (it did not wake it up)

But if not does it mean I must now order a 12v charger? Which model then?

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klim8skeptic avatar image klim8skeptic ♦ commented ·

@clive87 Is this your battery?

It seems unlikely that the multi discharged your batt to 8.0v.

As standard the multi will shut down at 9.30v. Of course you should program the multi to shut down before your batt BMS disconnects at 10.0v.

You did program your multi?


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clive87 avatar image clive87 klim8skeptic ♦ commented ·
No!!

There was no indication that I had to do that - I have no idea how to do it anyway.

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Alexandra avatar image Alexandra ♦ clive87 commented ·
There is not a single battery based inverter in the world that you do not need to program for specific batteries.
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clive87 avatar image clive87 Alexandra ♦ commented ·
so how is that done?
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klim8skeptic avatar image klim8skeptic ♦ commented ·

@clive87 Jumpstart your lithium battery? Dont burn anything down.

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clive87 avatar image clive87 klim8skeptic ♦ commented ·
That set up is not like mine. I do not have a jump starter either. I will have to remove the battery and take it to the manufacturer/distributor.
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Alexandra avatar image Alexandra ♦ clive87 commented ·
@clive87

Does the battery manual not have a bms wake up procedure? That is strange.

If it does not wake up with a charger then an incandescent bulb across the terminals can also do it.

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clive87 avatar image clive87 Alexandra ♦ commented ·

an incandescent bulb across the terminals

OK this may be doable. I must say the ingenuity of such a thing!!

I will try but how many watt? Volt? The bulbs here are 220V and about 60 watt. Designed for AC. Will it work? Or a DC low volt bulb?

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clive87 avatar image
clive87 answered ·

So I have now scoured the Multiplus data sheet and manual.

There is no indication that this product has to be programmed in any way.

There is no indication that it requires additional low discharge protection.

The low discharge setting is not mentioned other than that low discharge protection is included.

There is no indication that the low discharge protection is illusionary or possibly places your battery at risk.

The default settings given are fine for most batteries including mine.

The result is that I have a ruined/non-functional battery and seemingly an inverter not fit for purpose (I am too scared to connect it to my remaining healthy battery).

My next step is to consult the legal implications - the Consumer Protection Act here in South Africa does not permit this kind of misleading advertising nor the sale of goods that cause you damage.

To get the battery to the supplier is a one-day exercise.

I suppose I start there.

A most disappointing experience.



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clive87 avatar image
clive87 answered ·

Oh and also no indication that the battery protect units cannot be used with an inverter/charger. That just added to my disappointment.

At least with Voltronic you know what you get - a poorly constructed this or that - but no two ways about the "this or that".


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Alexandra avatar image Alexandra ♦ commented ·
@clive87

You can ask your supplier to program it any one worth their salt will do so.

And the product page describes the use of the battery protect and that is it unidirectional.

And voltronic also have to be programmed so not sure why you still think they dont have to be?

The victron is so much more versitile than a voltronic way more powerful and customizable features.

The datasheet shows the inverter works between certain voltages as mentioned above so cannot discharge lower than 9.3v on a 12v system.

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Michelle Konzack avatar image
Michelle Konzack answered ·

Since I have a new still packed MultiPlus 12/1600/70 I have checked the settings and I put it on a adjustable Power Supply (0-36V, 200A)


If I start the Inverter at 13V and regulate the Voltage down, it disconnect at 9,4V exact.


Since the MultiPlus will also draw dome Miliamps (the electronic need it, otherwise it would be not able to switch on on it'd own if the battery is charged) I assume, that you batter, has a defect which lead to a faster rest-discharging.


The Champion LiFePo4 200Ah should have a BMS integrated which disconnect the load in a low voltage situation. And you should check with the seller of this battery what's wrong with it.


When you installed your MultiPlus, why did you not read the Manual?


It is clearly written, that it has to be adjusted to use LiFePO batteries

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clive87 avatar image clive87 commented ·

It is clearly written, that it has to be adjusted to use LiFePO batteries

With respect - it is not. I have the manual in front of me and I have now read it x3. And there is absolutely nothing about LifePo4 or possible changes to discharge protection settings or anything.

I take on board that the battery may be faulty or perhaps the level of discharge has just placed it in sleep or perhaps it is ruined. I will investigate. But I repeat, there is simply nothing in the manual on this.

I gather I need further equipment to change the settings and I am now in the process of identifying and sourcing those.

The product should come with a warning: "1. This product cannot operate as a stand alone. 2. Before using this product first obtain comprehensive instructions from __________3. Before using this product reprogramme it in accordance with __________. 4. Purchase these items ( ________ ) in order to reprogramme the settings."


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Michelle Konzack avatar image Michelle Konzack clive87 commented ·
I am not at home and can not check again, but there is somewhere written, that the MultiPlus is setup by default for AGM batteries which also works flawless with Lead-Acid batteries.
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tom w avatar image tom w clive87 commented ·

@clive87

It is written, that the factory settings are for "Victron Gel Deep Discharge (also suitable for Victron AGM Deep Discharge )", see Page11 of https://www.victronenergy.de/upload/documents/Manual-MultiPlus-1600VA-EN-NL-FR-DE-ES-IT.pdf

On page16 you will find the dipswitch settings, which need to be changed for LiFePo4.

However,

I recommend using VE.Config.

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Michelle Konzack avatar image Michelle Konzack tom w commented ·
Thanks for correcting me
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clive87 avatar image clive87 tom w commented ·
Yes I am getting the VE Config. Thank you.
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Laurens D avatar image
Laurens D answered ·

I do not have experience with the multiplus itself, but with the multiplus 2 you can set with the ve configure 3 application the battery type by clicking on the 'Battery Type:' button on the top right in the 'Charger' tab; you can also change settings on the 'inverter' tab related to shutdown.

1677660116891.png


But considering the voltage is 8v for a 12v system is just strange because those batteries could have their own BMS that will make sure this does not happen (< 10v @2.5 each is their rated minimum), does it still give power? because I would have thought you would have been cut-off from the battery.

In this state you cannot be sure that it will stop overcharging, please do contact their support because this might be a risk you don't want to take and If you do please make sure you keep an eye on it.




1677660116891.png (40.5 KiB)
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tom w avatar image
tom w answered ·

I tried to find datasheet for the battery with no success :-(

However,

I found a shop selling a cheap LiFePo battery called Champion LiFePo4 200Ah. The advertisement specifies the cutoff voltage for the BMS of 10.6V. Based on that number I guess the battery disconnected itself at 10.6V while the Multiplus continued to discharge. At 9.4V the Multiplus disconnected as well. The 8V you now measuring is a residual voltage in caps of either the BMS or the Multiplus. As soon as you connect a small load the voltage might disappear.

Here is what you can do:

  1. Disconnect the battery and try to resurrect the BMS by connecting a current limited 12-15V supply.
  2. When the battery will charge on the external power supply, get yourself a VE.Bus dongle and program the Multiplus for LiFePo batteries.
  3. Reconnect system and try again.
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clive87 avatar image
clive87 answered ·

Thank you - I will take the battery in to be done by the supplier. I dont trust my abilities.

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astrayan avatar image astrayan commented ·
9.4V is a pretty strange, low voltage for lead acid. Normally they are considered to be flat at 10.8. But there is typically another setting in Victron inverters called Dynamic, which lets the battery dip lower, if the inverter is outputting a lot of power, so it doesnt go off, when you put a toaster on. On a lead acid, you would probably set the normal low voltage to 11.5V, and the dynamic to 10.5. At 12V, a lead acid has 30% left, and is considered to be going into the high wear zone. But Lithium is a bit different.
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clive87 avatar image
clive87 answered ·

My struggles continue. The supplier says the default setting in the Multiplus provides too low a charging current. Says it is pre-set at 10 or 15A but should be 50A. So I am sent back to the drawing board. EXCEPT - I now have a VE connect and I can access the Multi.

No luck, the multi is already pre-set at 50A. So I upped it a bit to 70A (well within the battery range) and I set the min discharge cut off at 10.8V as prescribed by the battery manual. I changed the charging profile to LifePo.

I connected the dead battery to the live one and BOTH were charging through the night.

Now what?

My dead battery remains dead.

The alarm flashes and the charge light burns bright.

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astrayan avatar image astrayan commented ·
What's the new battery you have? Does it have bluetooth?

Does the whole problem go away, if you put a car battery there?

Can you supply any spec sheets for this "Champion" battery that doesn't seem to google?

I've been looking at warranted batteries with bluetooth in them. Lithium is a bit dodgy because a chinese supplier can swap rubbish cells into them.
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Alexandra avatar image Alexandra ♦ astrayan commented ·
Sometimes a bms shut down has occurred because one cell is too low to be considered safe.


In this case the low battery needs to be opened and repaired. Again the battery manufacturer is usually the one that outlines recovery methods.

It should be returned to supplier for a warranty claim.


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astrayan avatar image astrayan Alexandra ♦ commented ·
It does seem that way
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