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LiFE battery charging using Bulk and float as with Lead Acid


andrevh

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Hi

I got a Schubart inverter 24V and 2 1500W LiFE batteries with a Schubart sticker on.

The settings the store gave is 29V Bulk,  28V float and 24V discharge cutoff.

I am using 200Watt in office and yesterday the batteries did supply the ncessary for first loadshedding but not the second  2 hours later the afternoon.

I have to work with what I have now.

What would the recommend best performance settings be.

On a spec I coul get:  http://www.sustainable.co.za/media/pdf/FreedomWon/freedom_won_lithium_battery_spec_sheet_fw-12-100.pdf

it specifies charge moe 14.6 V (12V) at 0.2C  and then 14.6  at 0.02C  which would assume 29.2  which is also the maximum bulk charge of inverter.

The cutoff is specified as 8V which should make the 20V cutoff of inverter safe?

 

Thus would 29V or even 29.1V float be safe to use and 29.2V Bulk?

 

 

 

 

 

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  • 2 weeks later...

LiFe batteries want between 3.45V and 3.65V per cell. There's usually 4 cells in a "12V" battery, or 8 cells in this case. So you want a charge voltage of no more than 29.2V... BUT... and this has been discussed on another thread, 1) very little extra energy is stored by charging up to 3.65V per cell, and 2) it is beneficial to the life of the battery to charge a bit lower, ie at 3.45V.

Using the Victron sheet is not a bad idea. Charge to 28.4V, and float at 27V.

 

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I have added a battery balancer and am testing discharge.

 

I got a high voltage on upper battery after an hour  and the  Voltages were 13.65V and 13.12V

 

A minute after tht the system shutdown and the battery voltage were minus on the lower and 13.82V on the other. 

The same happened the first time without  a balancer and I swapped the batteries.

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1 hour ago, andrevh said:

I have added a battery balancer and am testing discharge. 

 

I got a high voltage on upper battery after an hour  and the  Voltages were 13.65V and 13.12V 

 

A minute after that the system shutdown and the battery voltage were minus on the lower and 13.82V on the other.  

What do you mean the battery voltage was minus?

If I assume that each battery has its own built-in BMS, and since the capacity will never be identical, whichever one reaches the danger point first will disconnect. Which is good. But if you measure it in this state, the lower one is now an open circuit, and as a result the voltage across it will appear to be negative. I actually explained it previously, where a member measured -36V across a battery.

Site-lock won't allow me to post a link to that article. I'll try it in another post.

 

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1 minute ago, plonkster said:

Site-lock won't allow me to post a link to that article. I'll try it in another post.

Let's try it inline... if you can see this, I finally managed to get past sitelock's draconian policies.

Edited by plonkster
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Thanks, got it.    To find an existing topic  across 256+ topics not always do-able  especially when topic names are not properly descriptive.

I will keep on exchanging batteries  till I get a working battery set or will go back to heavy lead acids eventually.

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34 minutes ago, andrevh said:

Thanks, got it.    To find an existing topic  across 256+ topics not always do-able  especially when topic names are not properly descriptive.

Hehehe didn't mean to suggest you should have found it, my bad 🙂

28 minutes ago, andrevh said:

When I disconnected everything

That's the trick. When it is still in circuit, you see the other battery(ies?) in reverse and get a negative voltage. It merely means this one (you're measuring) is either bad or open-circuit. If it has a BMS, chances are it's gone into protection mode of some kind and will recover if you charge it again.

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2 hours ago, plonkster said:

if you can see this, I finally managed to get past sitelock's draconian policies.

I find I often have to select the "paste as plain text instead" (or similar) option that turns up after a second or so. Especially links to pages in the files section. It does seem silly not to allow fancy linking to pages on your own forum.

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Hi

 

This is now my third swap of Lithium Ion 12V x 2.    After charging them lastnight and made sure it is balanced, I started the dischange through Inverter process.

It went well for 3 hours but at a combine voltage of 26.9V while discharging it shutdown, same as described on  third post where while connected in series with load, the 1 show negative,

but disconnected, the one was at 12.6V and the other at 13.8 or around there.

 

1) Contacting the supplier they said I need to do this process a few times before these batteries would become stable???

2)  I should not use a balancer (Victron balancer , using .7A) to balance them, it is self balancing???

     Two serial connected packs????

 

Is above 2 points valid for using Lithium Ions in  basically UPS applications.  (I doubt it, but maybe I have something to learn here)

 

The load on the batteries is about 170Watt and it is 1500W batteries.

 

 

 

Edited by andrevh
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To add to the topic, based on the Victron Superpack whose spec is above they say:

Do in that case be sure that your chosen replacement fits your criteria by checking the datasheet and be aware the SuperPacks can be connected in parallel, but not in series. Hence in that case you would consider the other Victron lithium products named above.

 

Mine were sold as a serial application (2 batteries)  -- Not victron but another Schubart brand

 

 

 

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7 hours ago, andrevh said:

To add to the topic, based on the Victron Superpack whose spec is above they say:

To understand why, consider the difference between the older batteries with the VE.Bus BMS:Selection_138.png.d9cb1078cee6369bf0506c027b66bea0.png

That daisy-chains between batteries, like this (see the grey wires):

Selection_140.png.c596c548285a90c4a3d33373c39c124c.png

So what this does is to ensure that if there is a high cell in any battery, energy can be removed from it and passed on to a low cell anywhere else (not necessarily in the same pack). Now in these batteries the balancers are very simple, it's simply interleaved switches with a resistor to bypass some current and do passive balancing. But that grey cable isn't just a single wire, it has three connections in there, also allowing signaling for a high/low cell and so forth. It is all tied to a small BMS unit, which in turn controls either an external disconnect, or talks directly to the Multi over VE.Bus.

Now the Superpacks that were released last week are similar, except they don't have the daisy-chaining or the external BMS. There is a BMS inside the pack, but no cross-pack balancing can be done.

Selection_139.png.b814e96e2326ff59b2834baaa039936b.png

And this is why they tell you not to put it in series.

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