Running a petrol generator vs the cost of batteries compared

[Lupus]

What does 1000 cycles for lithium actually imply in practice. Is that 1k times I can drain them to zero? Or something else?

If I have 3 sessions of loadshedding per day like in stage 6 and I flatten them, would 1k cycles last me 1 year then?

Tx

Yes that is a battery cycle. Also why are you draining them 3 times a day

 

[wingnut771]

What does 1000 cycles for lithium actually imply in practice. Is that 1k times I can drain them to zero? Or something else?

If I have 3 sessions of loadshedding per day like in stage 6 and I flatten them, would 1k cycles last me 1 year then?

Tx

A cycle is 100 to 0 back to 100.

 

[hj007]

Yes that is a battery cycle. Also why are you draining them 3 times a day

I'm assuming that 4 hours of loadshedding, 3 times per day is likely to drain them?

Should I rather just get larger ones, ie would draining them only 50% last exponentially longer, or just twice as long and be therefore the same lifespan?

 

[AchmatK]

I'm assuming that 4 hours of loadshedding, 3 times per day is likely to drain them?

Should I rather just get larger ones, ie would draining them only 50% last exponentially longer, or just twice as long and be therefore the same lifespan?

What load are you planning to run on them? And what batteries are you looking at?

 

[hj007]

What load are you planning to run on them? And what batteries are you looking at?

No just wanting to understand what cycles means and whether something will last 1 or 2 years based on cycles and assumptions on stage of loadshedding/hours off.

 

[sgs]

No just wanting to understand what cycles means and whether something will last 1 or 2 years based on cycles and assumptions on stage of loadshedding/hours off.

A 100Ah battery at 12v is roughly 1.2kWh worth of energy. If you place a load of 200W on it for a 2 hour loadshedding slot, that is roughly 0.4kWh discharge. 3 of those slots a day would then make up one 1.2kWh cycle.

If the battery has a 2000 cycle life, then it should last you 2000 loadshedding days or 6000 loadshedding slots.

If you intend to drain the battery with every loadshedding slot, however, then you can use up to 600W load. But your battery would then only last 2000 slots, and not 2000 days.

It is all a balance, and you probably want more capacity than a single loadshedding slot as a buffer anyway. So play with the numbers above with your load requirements and budget being the variables.

 

[Jean Claude Vaaldamme]

battery packs in tools are mostly lithium nowdays and they certainly dont last 5 years .18 months to 24 months usually .the real truth on lithium batteries is still out there .i think many people are going to be very annoyed with their prized chinese battery packs .

Well if you go back in the archives before lithium batteries was a thing, you will see the same people claiming how great deep cycle and gel batteries are and how long they will last, they would not back down and dismiss any other argument. Lithium is the new gel and they will defend it with all they have, for the next 4 years till they also pack up.

 

[AchmatK]

Well if you go back in the archives before lithium batteries was a thing, you will see the same people claiming how great deep cycle and gel batteries are and how long they will last, they would not back down and dismiss any other argument. Lithium is the new gel and they will defend it with all they have, for the next 4 years till they also pack up.

The real test for any battery is how much power it can provide at any given time and total power it can deliver before its capacity is significantly reduced.

Let's look at my pylontech battery bank as an example.

It's just over 2 years old.
Total capacity = 396Ah or 18.8kWh
Maximum power is limited to 8kW that my inverter is rated at so less than 0.5C discharge rate but average is 0.1C that I discharge them.
Total power extracted since installation = 6 942kWh
Current SOH = 97%
Current capacity = 382.1Ah
Capacity lost so far = 13.9Ah

I know exactly what to expect from it and its following the expected capacity fade graphs as found in the Australian battery tests.

The capacity fade of lithium batteries is linear and even if it only has 80% of its original capacity in 10 years time, it does not render the battery useless. The battery could be used longer and still usable at 50% of its original capacity.

Currently the cost to me has been just over R15 per kWh extracted from the battery. Another two years and that would have dropped to under R8 and by the time the battery bank is at 80% SOH I expect that cost to be under R1 per kWh extracted from the battery.

I would really like to know what the lead acid batteries are providing in their lifespan and what the cost per kWh is.

 

[Lupus]

I'm assuming that 4 hours of loadshedding, 3 times per day is likely to drain them?

Should I rather just get larger ones, ie would draining them only 50% last exponentially longer, or just twice as long and be therefore the same lifespan?

Depends on what you're using

 

[Splinter]

I don't think there is any debate that a generator is easily more expensive with intense load shedding. I have a generator, and the petrol is expensive. Plus it's a bit of a hassle buying the petrol and filling up the genny repeatedly.

But at this point in time I wouldn't change my decision. Something about not having to rely on Eskom should the grid go down soothes me.

Of course, I'm not talking about the costs of going completely off the grid here.

 

[hj007]

A 100Ah battery at 12v is roughly 1.2kWh worth of energy. If you place a load of 200W on it for a 2 hour loadshedding slot, that is roughly 0.4kWh discharge. 3 of those slots a day would then make up one 1.2kWh cycle.

If the battery has a 2000 cycle life, then it should last you 2000 loadshedding days or 6000 loadshedding slots.

If you intend to drain the battery with every loadshedding slot, however, then you can use up to 600W load. But your battery would then only last 2000 slots, and not 2000 days.

It is all a balance, and you probably want more capacity than a single loadshedding slot as a buffer anyway. So play with the numbers above with your load requirements and budget being the variables.

Thanks so it sounds like its a 1-1 relationship then, 200W would give 6000 slots, 600W would be 2000 slots. Ie the overall total W drawn over its lifespan remains constant.

 

[hj007]

I don't think there is any debate that a generator is easily more expensive with intense load shedding. I have a generator, and the petrol is expensive. Plus it's a bit of a hassle buying the petrol and filling up the genny repeatedly.

But at this point in time I wouldn't change my decision. Something about not having to rely on Eskom should the grid go down soothes me.

Of course, I'm not talking about the costs of going completely off the grid here.

Backup power is ok and can handle the cost.. I don't think many can afford / want to become their own small power stations... I think it'll be easier to move than become a permaculture/farm

 

[eye_suc]

I would really like to know what the lead acid batteries are providing in their lifespan and what the cost per kWh is.

I would also like to know the actual performance of lead acids.

My 1 x 105AH deep cycle lead acid battery died after using it 3 times. R2500 down the drain. I bought the damn thing thinking my light load will make it last for years.

 

[wingnut771]

I would also like to know the actual performance of lead acids.

My 1 x 105AH deep cycle lead acid battery died after using it 3 times. R2500 down the drain. I bought the damn thing thinking my light load will make it last for years.

There should be a warranty though? Also, if a lead acid is left on a shelf in the shop for too long and left to discharge too much then it gets permanently damaged so you could have received one of those? When you receive a battery, the voltage should be 12.5+V

What does using it for 3 times mean?

 

[Lupus]

I would also like to know the actual performance of lead acids.

My 1 x 105AH deep cycle lead acid battery died after using it 3 times. R2500 down the drain. I bought the damn thing thinking my light load will make it last for years.

I had 2 120ah batteries running light load around 170w and the stupid gel lasted 5 months

 

[Lupus]

There should be a warranty though? Also, if a lead acid is left on a shelf in the shop for too long and left to discharge too much then it gets permanently damaged so you could have received one of those? When you receive a battery, the voltage should be 12.5+V

What does using for 3 times mean?

With this load shedding they'll pull over discharge

 

[wingnut771]

I had 2 120ah batteries running light load around 170w and the stupid gel lasted 5 months

Do you still have them?

 

[Lupus]

Do you still have them?

No long gone, tried the warranty route.

 

[wingnut771]

No long gone, tried the warranty route.

Oh well, was interested in the cycle and stand by voltage recommendations written on the side to see if it was compatible with the mecer. How did the warranty route go?

 

[AchmatK]

I would also like to know the actual performance of lead acids.

My 1 x 105AH deep cycle lead acid battery died after using it 3 times. R2500 down the drain. I bought the damn thing thinking my light load will make it last for years.

I'm assuming that's a 12v battery which is 1.26kWh.

What loads were you running on it and for how long? Also what was your charging amps.

Ideally you should only run 5A loads on this battery over a 20 hour period which would take it to 50% DOD and then charge at 5A. Anything higher than this will negatively impact the battery.

5A at 12v is a 60w load.