Cycle Lithium Batteries?

[pspspeed]

I have upgraded my system to a Goodwe 5048ES with 2 x 2.4kw lithium pylontech batteries.  Question is, should i let the batteries cycle or can I just leave them as back-up in case of grid failure.  Don't know what is best for lithiums. Currently I have the as back-up only (loadshedding and cable theft). I see the goodwe does do a small amount of floating (charge/discharge cycling) but not anything heavy.  

Your advice would be appreciated.

[Guest]

Recently I became aware that cellphone / tablet / laptop batteries should not be kept 100% charged all the time like say standby UPS batteries.

It is not good for them, their capacity degrades.

That is maybe a question to ask Pylontech direct.

[pspspeed]

10 minutes ago, The Terrible Triplett said:

Recently I became aware that cellphone / tablet / laptop batteries should not be kept 100% charged all the time like say standby UPS batteries.

It is not good for them, their capacity degrades.

That is maybe a question to ask Pylontech direct.

I also read that in an article somewhere - maybe I will let them cycle to around 20% DOD just to help when the microwave or coffee machine is switched on during the day and PV is not enough to prevent the grid being used.

[___]

If you're not going to cycle them, then reduce the charge voltage and hold them somewhere around 90% SoC. For pylontech I'd say float around 51.8V or thereabouts.

I cycle mine, for the simple reason that my most expensive power costs R2.55 per kwh, and my estimated battery cost is already lower than that (it is not yet lower than the R1.85 I pay in the <600kwh bracket). So I literally aim at keeping my annual grid consumption at 7200kwh and using the battery for the rest. Presently this means I cycle the battery down to 35% DoD... but interestingly only in spring and autumn. In summer the aircons directly consume most of the PV, and in winter there is less sun, so then I run at a lower 15% DoD.

Edited February 20, 2019 by plonkster

[Gabriel_2018]

I agree @plonkster 51.8 V, or 3.45 V per cell, is enough to have a 80% of LiFePo4 capabilities.

[pspspeed]

I would have expected the Goodwe 5048 ES to handle the battery charging properly.  It has a setting for the Pylontech batteries as well as the option of 'back-up' only for the batteries. It floats them between 99 & 100 % or rather the battery BMS does this. You cannot set the charging /float voltages unless you choose the 'user define' option which has some other settings I'm not too sure about.

Interestingly I see the LG battery only charges to 95%.

Anyway, I have set it to cycle the bats to 80% before switching to grid if there is not enough PV. Will monitor it and see how it performs with the charge/discharge settings.

Thanks so far

[2una]

Also curious what to do on this with Pylontech's & a UPS only setup

Sent the below to Pylontech & see if i get a reply.

......................................................................................................................

Good Day,

Tech question here

 I have 3x US3000b with a Victron Multiplus II inverter used as UPS only (no PV connected) for standby power in case of power cut (South Africa).

 Is it ok to leave inverter/charger to hold battery at 99/100% without daily cycle or should i change settings to hold battery at lower voltage?

 If i can find a way to make the inverter force a daily cycle what is minimum cycle i can do to keep battery & warranty good?

 Settings at the moment are these

 

Battery type	Lithium
Charge curve	Fixed
Absorption voltage	53.2 V
Float voltage	53.0 V
Absorption time	1 Hr

................................................................................................................

 

Be handy if Victron would allow a time based "ignore AC input" so a daily cycle could be loaded.

Any ideas on how to skin that cat?

 

 

.

[Guest]

8 minutes ago, 2una said:

Be handy if Victron would allow a time based "ignore AC input" so a daily cycle could be loaded.

Any ideas on how to skin that cat?.

Spit balling again. On a timer, switch the breaker off on the DB so that the inverter runs off the batts.

After an hour / two, switch plug back on.

How to automate this, no idea.  

[2una]

15 minutes ago, The Terrible Triplett said:

Spit balling again. On a timer, switch the breaker off on the DB so that the inverter runs off the batts.

After an hour / two, switch plug back on.

How to automate this, no idea.  

Manually i can do it with doing the breaker off thing yip but i also work away & or ones going to forget to do it so it needs to get loaded to do it automatically somehow & you can guarantee Murphy is going to put his foot in the door with the timer way also but is i think the easiest

[Guest]

1 minute ago, 2una said:

Manually i can do it with doing the breaker off thing yip but i also work away & or ones going to forget to do it so it needs to get loaded to do it automatically somehow & you can guarantee Murphy is going to put his foot in the door with the timer way also but is i think the easiest

I read recently that lithiums do not like to be kept fully charged.

Until you find a automatic method, maybe do it once a week when at home, or evenings when you know you are there?

Or run the lights from 12-6am from batts - till it is automated.

[Guest]

44 minutes ago, 2una said:

Be handy if Victron would allow a time based "ignore AC input" so a daily cycle could be loaded.

2una, do you have a VenusGX by an chance?

[2una]

41 minutes ago, The Terrible Triplett said:

2una, do you have a VenusGX by an chance?

yes, multi II 3000 > venus gx > pylons

[Guest]

5 minutes ago, 2una said:

yes, multi II 3000 > venus gx > pylons

I wonder what will happen IF you switch on ESS, set it to use 20/30/50% of the batts, setting the recharge to times you want, to use some of the batts.

@plonkster - can this work?

[2una]

@The Terrible Triplett

fell onto this - would this work?

https://www.victronenergy.com/live/drafts:acin_ignore_timer_using_ccgx_gen_start_stop_example

[Guest]

Now we are talking.

Plonkster should be around shortly ... best person for these intricacies. 

Using ESS, if that can work, would be even simpler.
Set under ESS, Mode to Optimized (with Battery Life)
Then set Minimum SOC (unless grid fails) to 20% or 50% or what what.
Under Scheduled Charging, enable a Schedule, and set the day, time to re-charge.
 

[2una]

Nice! - lets see what thoughts he thinks is better approach

[Guest]

1 minute ago, 2una said:

Nice! - lets see what thoughts he thinks is better approach

Try it if you are there. Come on ... you know you want to ...  

Just remember to switch Feed-in Excess solarcharger power to OFF.

[___]

2 hours ago, The Terrible Triplett said:

I wonder what will happen IF you switch on ESS, set it to use 20/30/50% of the batts, setting the recharge to times you want, to use some of the batts.

Yeah, you can do that. Just set 22 hours of the day as a scheduled charge slot (with no target SOC), and in the other 2 hours of the day it will discharge the batteries slightly.

Personally I'm not quite sure why you'd want to do that. The batteries generally suffer a little bit of a shortened life if they are held full permanently, but cycling a battery does pretty much the same thing: It also "uses" the battery and therefore will eventually "use it up" to use a direct Afrikaans translation

The best thing to do is hold it at a lower voltage. If you turn on DVCC, the charge voltage will be automatically lowered to 52V. That is about 3.45V per cell, perfectly good for long term "floating". Remember, LFP don't float in the same manner as lead acid (constantly making small bits of gas and boiling off battery water/electrolyte)

[Guest]

20 minutes ago, plonkster said:

Personally I'm not quite sure why you'd want to do that.

Is it not a justification to use the batts a bit to get a ROI, like you do?

All that 2una needs to maybe do, is add a couple of panels, use them to recharge the bit over a day, to nit use Eskom.

[___]

13 minutes ago, The Terrible Triplett said:

All that 2una needs to maybe do, is add a couple of panels, use them to recharge the bit over a day, to nit use Eskom.

There is no point in cycling (and no ROI) if you're going to charge them with the grid. If you add PV modules... then absolutely!

[Guest]

50 minutes ago, plonkster said:

There is no point in cycling (and no ROI) if you're going to charge them with the grid. If you add PV modules... then absolutely!

But that is what I said ... (cwl)

1 hour ago, The Terrible Triplett said:

All that 2una needs to maybe do, is add a couple of panels, use them to recharge the bit over a day, to not use Eskom.

 

[2una]

So you guys think there's not a lot of advantage cycling, Panels aren't an option ,i'm in an apartment here so anything solar is no go area.

Shall see if Pylontech come back with an answer.

DVCC is on already - atm i'm 52.15V & showing 99% charge, Multi is sitting in Absorption

[Guest]

1 hour ago, 2una said:

So you guys think there's not a lot of advantage cycling, Panels aren't an option ,i'm in an apartment here so anything solar is no go area.

Seems not. If Plonskter says so, then it is so. No jokes.  

[___]

15 hours ago, The Terrible Triplett said:

Seems not. If Plonskter says so, then it is so. No jokes.  

Lead acid is different. There you need to stir the electrolyte a bit (flooded lead acid specifically), so a short burst followed by an absorption charge is sometimes needed. Not so much with these. The only reason to do it would be as a test run. For example, if you lived in a country that had less than one power failure a year, you might have the danger of a failed battery which you don't notice until you need it. In that case you might periodically run a discharge and recharge test cycle.