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Should I be "exercising" my battery regularly?


MdF
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2 hours ago, Tariq said:

i have a 4.8 kWh battery, which I run down to 20-25 % every night, "usually"load shedding is announced, so IF the SOC is low and there is no pv, i charge the batteries from the grid, the only time I got caught flat footed was on a stormy morning, with batteries at 20 % SOC and then we had a power outage, so had to shut down the inverter, so, yes, I don't cater for EVERY situation, but I am getting the most bang for the buck from my batteries.

I have a 6.4 kWp array and run all my major loads during the day, only have 250-450 watt loads at night.

Hi Tariq

How long have you been doing this and what is your observations on the SOH of the batteries?

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1 hour ago, Vani said:

2. (During the day) When the battery charges up to maybe 80% then allowed to discharge to perhaps 65% and then charge up again, is this not using up a charging cycle of the battery??? If this is true, then does it mean that multiple charge cycles are used up each day, and therefore reducing the lifespan of the battery???

I do the same thing and I'm sure it increases the number of cycles. Whether its significant enough to drastically reduce the lifespan of the battery , i'm not sure.

I have asked a similar question on this forum and the answer I got is that the BMS calculates the cycles based on the cumulative energy into and out of the battery, so if you discharge to 50%  and charge back up to 100% it will be 0.5 cycles.

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With Tariq's 98% SOH after 14 months, its not that bad. But i am also pretty sure that the deterioration will not be linear with time.

I think Pylontech talk about having at least 60% capacity (SOH) after 10 years. So Tariq's deterioration does not seem that bad at all

My system is only a month old on the batteries so it will be interesting to see the rate of deterioration based on my "ONE cycle per day" theory.

The idea that a full cycle is accumulated based on percentage discharge and charge reaching a certain point seems to concur with the logic from manufacturers that claim you get more cycles if the DOD is not too low.

Theoretically there could be many small discharge and charge cycles depending on the settings, amount of sun and load demand on any given day. While lithium is resilient, i still "think" the chemistry has certain thresholds that will affect stamina long term. To what extent, only somebody with some long term data can support.

My gut feel is based on the anecdotal evidence of my experience with smartphones.

 

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I found this info on prolonging battery life. It seems to suggest that multiple small discharges and charges are not bad for a lithium battery and if anything can aid longevity.

https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

and this one with a snippet below:

https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/

image.png.d29de067549a433fcf1861d8f1a09bcc.png

 

 

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19 minutes ago, Vani said:

I found this info on prolonging battery life. It seems to suggest that multiple small discharges and charges are not bad for a lithium battery and if anything can aid longevity.

https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

and this one with a snippet below:

https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/

 

 

Thank for this information.

MdF

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From battery university; Ideally, you should never fully charge (100% is a no-no) or discharge your battery, charge to 95% and then discharge to max 90% (DoD). High heat and fully charging/discharging a battery is what kills it. The additional 5% from 95 to 100% charge is what stresses the battery. Keeping it at 100% for extended periods is also not good.

The only device I have found that allows me to prevent a battery from fully charging is my Dell laptop, I set it to charge to a max of 95%.

The Goodwe / Pylontech setup charges the battery to 100% but then insists on discharging to 90% every day, at a minimum, if you are running in general mode.

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21 hours ago, Tariq said:

i have a 4.8 kWh battery, which I run down to 20-25 % every night, "usually"load shedding is announced, so IF the SOC is low and there is no pv, i charge the batteries from the grid, the only time I got caught flat footed was on a stormy morning, with batteries at 20 % SOC and then we had a power outage, so had to shut down the inverter, so, yes, I don't cater for EVERY situation, but I am getting the most bang for the buck from my batteries.

I have a 6.4 kWp array and run all my major loads during the day, only have 250-450 watt loads at night.

I have similar base load and run mine down to between 60% and 50% during the evenings. I also allow the battery to be used in preference to the grid during the day, where this is necessary.  Been doing so for about 10-11 months, and battery health is at 99%.

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14 minutes ago, FixAMess said:

From battery university; Ideally, you should never fully charge (100% is a no-no) or discharge your battery, charge to 95% and then discharge to max 90% (DoD). High heat and fully charging/discharging a battery is what kills it. The additional 5% from 95 to 100% charge is what stresses the battery. Keeping it at 100% for extended periods is also not good.

So then, based on this, I should change the table below for the two instances of 100% fully charged to say 98% or even 95%?

Battery_%Charge-01.png

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I'm not sure how much difference the extra 5% makes on reducing battery life over a 10 year period, go to battery view and read all the info, its really good. Their view is probably based on a purely scientific basis, so it might not be practical to only charge to 95%. Your BMS should prevent stressing etc but who knows, the battery and BMS technology changes so quickly maybe the newer BMS's don't stress the batteries.

My BMS takes the battery to 100% but then discharges it to 90% every day so its never kept at 100% for an extended period. 

If you feel it will make a difference then make it 98% for e.g, just not 100%.

 

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I have just set my minimum charge level to 95% from 16:00

So typically it would charge to 100% during the day but won't be there for more than 3 to 4 hours and then start discharging down to 95%.

My SOH also dropped to 99% this week and have been in use since Feb this year (8 months)- I have 3 x 3000C batteries.

Run them down to 40% every night

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