I have a simple inverter back up.on wheels... Mecer 1440w with 2x 105AH lead acid batteries. It is wired into my DB to back up my gate motor (40w), router (10w), outside lights (100w) and TV (100w).

With Stage 3/4, we're being loadshedded 2- 3 times a day.

During the day, with no-one home, the demand on the unit is less than 50w/hour for the gate motor and router, possibly less.

Is this <100w draw for the 2 hours of load shedding considered a cycle, which will reduce the lifespan of the batteries?

Many factors affecting the life of any battery. This article provides some useful info regarding the factors for Lead Acid Batteries, including the data considered in terms of cycles.
https://www.power-sonic.com/blog/deep-cycle-battery-everything-you-need-to-know/

 

37 minutes ago, zsde said:

Many factors affecting the life of any battery. This article provides some useful info regarding the factors for Lead Acid Batteries, including the data considered in terms of cycles.
https://www.power-sonic.com/blog/deep-cycle-battery-everything-you-need-to-know/

 

That's a very interesting and helpful article. Thanks

12 hours ago, zsde said:

Many factors affecting the life of any battery. This article provides some useful info regarding the factors for Lead Acid Batteries, including the data considered in terms of cycles.
https://www.power-sonic.com/blog/deep-cycle-battery-everything-you-need-to-know/

 

If I understand the article, a cycle theoretically starts when a battery dips below 80% of its capacity.

So drawing 100w on a 1000w storage (90% of 2 x 100ah batteries), the battery is not cycling and the lifespan should be maximized.

Right?... in theory....

Edited November 23, 20223 yr by miguelm

In theory correct. So you would need to add up your totals to determine when you have reached the approximate 80% DOD equivalent. That could then be regarded as  a cycle.
 

Edited November 23, 20223 yr by zsde

When I looked at several articles on the web, there are 2 theories that come up :

1.  If you discharge a battery from 100% to 90% and then charge back to 100%, it’s considered a cycle.   See :  https://www.quora.com/What-is-a-battery-cycle-count. Any value discharged, let's say 100 to 99% and bac to 100% is a cycle.

2. A charging cycle is when a battery goes from being fully charged to empty and then from empty to fully charged  - see https://www.grepow.com/blog/charging-cycles-of-lithium-ion-polymer-batteries.html

49 minutes ago, PeterW102 said:

there are 2 theories that come up

And thats what they are, theories. There are so many factors affecting battery life and the OP was questioning Lead Acid which has vastly different characteristics to Lithium, starting with the 50% SOC/DOD threshold which is a SLA killer in terms of cycles and life.
Reading forums one sees so many variations in SLA use life spans. There are those that claim 7 years plus on lead acid and others who's Lead Acids are shot after a year. All of them mostly claim to have not "abused" them. 
Manufacturers claims are to be taken with a grain of salt. There are those that are honest enough to state their SLA will last 2500cycles plus if the SOC is kept above 70%. That means that a 100Ah battery is actually a 30Ah battery if you wish to achieve the claimed lifespan. Compare the price of a good 100Ah SLA to a 30Ah Li to have a true picture of price/performance as Li can be discharged to 10-20% SOC without any negative effects.

Don't wish to distract from the OPs  question.
Too many theories and opinions. My own conviction is that if you add up your usage between charges until that usage equals roughly 80% of the capacity, then consider that 1 cycle. i.e. Lets assume you use 10Ah per day which you recharge, i.e. your battery only dropped to 90%SOC. If your battery is 100Ah, then you would equal roughly 1 cycle every 8 days. Should you however discharge your SLA below 50%, then you may as well add 2 to 3 cycles as tests have proven the sudden drop in lifespan once that 50% mark is exceeded. 
 

2 hours ago, zsde said:

And thats what they are, theories. There are so many factors affecting battery life and the OP was questioning Lead Acid which has vastly different characteristics to Lithium, starting with the 50% SOC/DOD threshold which is a SLA killer in terms of cycles and life.
Reading forums one sees so many variations in SLA use life spans. There are those that claim 7 years plus on lead acid and others who's Lead Acids are shot after a year. All of them mostly claim to have not "abused" them. 
Manufacturers claims are to be taken with a grain of salt. There are those that are honest enough to state their SLA will last 2500cycles plus if the SOC is kept above 70%. That means that a 100Ah battery is actually a 30Ah battery if you wish to achieve the claimed lifespan. Compare the price of a good 100Ah SLA to a 30Ah Li to have a true picture of price/performance as Li can be discharged to 10-20% SOC without any negative effects.

 

To be fair,part of the issue with the cycle survivability is the discharge rates and heat too. If you do slow discharges they'll live years

8 hours ago, zsde said:

There are those that are honest enough to state their SLA will last 2500cycles plus if the SOC is kept above 70%. That means that a 100Ah battery is actually a 30Ah battery if you wish to achieve the claimed lifespan. Compare the price of a good 100Ah SLA to a 30Ah Li to have a true picture of price/performance as Li can be discharged to 10-20% SOC without any negative effects.

100%. This is the most important thing to note when comparing battery prices.

  There are two models:

Rainflow cycles - Every charge/discharge cycle is counted as a cycle, regardless of DoD.

Equivalent full cycles - 6000 cycles at 50% DoD is counted as 3000 cycles.

No battery datasheet I have seen specifies the method they refer to; so my guess is that they use the one that makes the figures look more favorable to them.

 

My battery counts cumulative discharge up to a percentage set in the bms and then triggers a cycle. This value was incorrectly set at 20% by default (I guess for LA) causing it to count cycles too frequently. I'm pretty sure this is the reason so many batteries count so strangely, causing confusion.

We are all thinking in terms of BMS and cycle counts.

The OP wanted clarity regarding Lead Acid Batteries and cycles/expected lifespan of those batteries.. 

15 minutes ago, zsde said:

The OP wanted clarity regarding Lead Acid Batteries and cycles/expected lifespan of those batteries.. 

Which I explained is also depending on the Heat factor as well as how fast it's discharged unfortunately,LA heats up and resistance increases the higher the load

Many of the graphs assume a steady low discharge rate

@miguelm Here is another easy to read article that shows DOD effect on the life of LA batteries

https://www.pveducation.org/pvcdrom/batteries/lead-acid-batteries