Does battery weight matter?

[Tomtomtom]

What would you consider an accurate equivalency ratio between LA and lithium (LiFePO4)?

I'm not sure there is one because it's nonlinear but I'd expect for a small UPS 20% DoD on lead acid to give about the same life as 80% on lithium. i.e. 1:4 on rated Wh basis. I'm basically agreeing with AchmatK.

Also, are you genuinely expecting to get around 6000 cycles (i.e. 6000 x nameplate rated Ah) out of your LA batteries?

No. Where did I say that? A cycle is defined as a discharge-recharge at a given DoD < 100% in all specs I've seen.

So no I wouldn't dream of getting anywhere near 6000 * nameplate Ah for any chemistry.

 

[Tomtomtom]

An equivalent LA battery would need to be at least 1 600Ah @ 48v. Random Google gives me a price of R5k for 200Ah @ 12v.

4 of these would get to 48v x 8 to get 1 600Ah. That's 32 of these batteries coming in at R160k. .

So one thing here that does remain in favour of LA is that, using this example, you *can* get close to 80 kWh out of a single discharge if you ever need to, vs a hard limit of < 20 from the lithium.

Obviously you pay in cycle life but it's valuable to have the option, especially with 4- vs 2- hour stages being a matter of probability.

It's a question of what the system is for, just surviving loadshedding vs. full grid independence, but I think most of us amateurs here are in the former camp.

So you can size for 20% DoD accept 40 when you need to cover 4 hours. With lithium you have to size for the 4 hours.

 

[Speedster]

No. Where did I say that? A cycle is defined as a discharge-recharge at a given DoD < 100% in all specs I've seen.

Right here

As I say it's not a lower lifetime when you properly size for DoD.

So no I wouldn't dream of getting anywhere near 6000 * nameplate Ah for any chemistry.

A decent LiFePO4 should comfortably complete 6000 cycles and still have around 70% of original capacity left. Also, I think you should revisit your cycle definition. I haven't seen a single source which defines it as you do.

 

[AlphaJohn]

Does battery weight play a big part in the quality of the battery ?


Been looking around and came across a few 200ah gel batteries that go for around 30kg vs most other 50-60kg.

Like this https://www.livestainable.co.za/product/gel-battery-ge200-12-200ah-12v/ only 28kg

Depends:

 

[Koosvanwyk]

So one thing here that does remain in favour of LA is that, using this example, you *can* get close to 80 kWh out of a single discharge if you ever need to, vs a hard limit of < 20 from the lithium.

You will only get the rated capacity out of LA batteries if you stick to its rating, so 100Ah /20Hr will only supply the full 100Ah if you discharge at 5 amp per hour (or 60wats).

In reality, a 100 AH LA battery will go flat in just shy of 40 minutes if we expect it to deliver the full 100 amps continiously and will only provide +- 66 amps.if you want to stick to 50% DOD then usable capacity is half +- of that

 

[AlphaJohn]

You will only get the rated capacity out of LA batteries if you stick to its rating, so 100Ah /20Hr will only supply the full 100Ah if you discharge at 5 amp per hour (or 60wats).

In reality, a 100 AH LA battery will go flat in just shy of 40 minutes if we expect it to deliver the full 100 amps continiously and will only provide +- 66 amps.if you want to stick to 50% DOD then usable capacity is half +- of that

Or simply put Peukert's law in one picture:

 

[Tomtomtom]

You will only get the rated capacity out of LA batteries if you stick to its rating, so 100Ah /20Hr will only supply the full 100Ah if you discharge at 5 amp per hour (or 60wats).

That's true but we're already talking about oversizing LA so discharge rate is also low relative to rated capacity.

Given that I'm just saying the available energy is higher for LA vs equivalent-lifespan lithium. So you can target an average DoD of say 20%, but you have flexibility to go to ~40% occasionally, which is exactly what many people need under (common) 2-hour and (less common) 4-hour loadshedding regimes.

It's a different matter if you're going off-grid or similar where I agree under heavy predictable cycling lithium is obviously superior.

 

[AchmatK]

That's true but we're already talking about oversizing LA so discharge rate is also low relative to rated capacity.

Given that I'm just saying the available energy is higher for LA vs equivalent-lifespan lithium. So you can target an average DoD of say 20%, but you have flexibility to go to ~40% occasionally, which is exactly what many people need under (common) 2-hour and (less common) 4-hour loadshedding regimes.

It's a different matter if you're going off-grid or similar where I agree under heavy predictable cycling lithium is obviously superior.

Let look at a typical backup system to supply a base load of 300w over 4 hours of load shedding. No spikes as this is only essential loads like a fridge, routers, TV, chargers, alarm, etc.

For something like this even a US3000 74A pylontech battery will suffice but let's use the UP5000 100A pylontech to give some extra backup time.

The pylontech is 0.5C rated so can supply 50A or 2 400w continuously. Only drawing 300w would leave the battery at 75% SOC after 4 hours. This should give a total of just over 15 hours of backup time before the battery gets to 5% SOC.

For LA lets look at a 100A 48v battery (4*100A 12v). Ideally this should be a 400A 48v LA battery bank.

On mobile so not going to go into all the details.

1. Lithium is only one battery that fits in a server rack. Minimal space needed and can be mounted on a wall in its upright position.

LA will need double the space for 100A LA and needs proper ventilation.

2. Wiring for lithium is simple with only one battery connected to the inverter.

LA will have complex wiring and will depend on the voltage of each battery ranging from 2V to 12V connected in series or parallel depending on the batteries. Wiring is expensive which adds another point of failure as they need to be the same length.

3. Lithium has integrated battery management software to protect it from over discharge or over current.

LA needs additional hardware to do this function and any over discharge can result in permanent damage.

4. Lithium can be expanded later. This is not possible with LA and the whole battery bank needs to be replaced if you want to expand.

5. Cost. 100A lithium is ±R30k. 100A 48v LA is about R20k but you will need to double or even triple the size of the bank taking the cost to over R50k excluding the cabling that goes with it and space consideration.

There is no place for LA in any backup solution no matter what scenario you throw at it. It's obsolete as a battery backup solution when there are better and cheaper alternatives available.

 

[Mars]

The question is when to replace.

Lithium ion batteries don't just go dead. Even a US3000 battery capacity doesn't just fall off a cliff at x number of cycles.

Due to each battery having its own bms I could have the first 3 batteries at 50% of original capacity and still functioning and contributing to the battery bank.

Absolutly. You should be able to read that info from the BMS and compare it to the spec sheet. It will tell you where you are in the batteries lifespan and tell you the batteries current performance.

For example, my 4.8kw narada battery has about 9000 cycles at 60% DOD. Currently Ive used about 3500 cycles. That means I will start seeing a loss of capacity after another 5500 cycles.

The other thing to remember is that the BMS will manage the battery until it no longer meet criteria and then it will just give you an error for safety reasons, so while you may get some performance out of it after its cycle life is completed I don't think it will be much.

Edit. 4.8Kw, not 438kw

 

[Speedster]

Absolutly. You should be able to read that info from the BMS and compare it to the spec sheet. It will tell you where you are in the batteries lifespan and tell you the batteries current performance.

For example, my 438kw narada battery has about 9000 cycles at 60% DOD. Currently Ive used about 3500 cycles. That means I will start seeing a loss of capacity after another 5500 cycles.

The other thing to remember is that the BMS will manage the battery until it no longer meet criteria and then it will just give you an error for safety reasons, so while you may get some performance out of it after its cycle life is completed I don't think it will be much.

I don't think this is quite accurate. Firstly, I strongly doubt you have 438kw (or even kWh) of battery capacity, unless you're powering a small town. Lithium capacity drops off from the get go, and in a linear fashion. There shouldn't be a day where you suddenly notice a change in capacity.

 

[Mars]

I don't think this is quite accurate. Firstly, I strongly doubt you have 438kw (or even kWh) of battery capacity, unless you're powering a small town. Lithium capacity drops off from the get go, and in a linear fashion. There shouldn't be a day where you suddenly notice a change in capacity.

Sorry, typo

 

[Tomtomtom]

There is no place for LA in any backup solution no matter what scenario you throw at it. It's obsolete as a battery backup solution when there are better and cheaper alternatives available.

Useful information, especially about incremental upgrade. But this is a bold conclusion.

Tell me what's wrong with this model - for a smaller system, budget R 5k: I see I can get ~600 Wh lithium (480 Wh usable at 80% DoD) or ~2400 Wh lead acid (480 Wh at 20% DoD).

This is parity, if we agree on the DoD-lifecycle equivalence of 80-20. Your point about upgradeability favours Li and my point about flexible DoD favours lead.

Right now, I would go lithium for this system if I needed no more than 150 W over 4 hours. But at 200 W over 2 hours, with the option to survive 4+, it looks like lead is currently still winning.

What have I missed?

And that's before other factors. I have a "dead" car battery which is 10 years old, repurposed at no cost to power my router UPS for the last 3 years. Still handles 4 hours and can go to 12 once or twice a year. I will have another dead acid to replace it with when it does finally fail, so I don't see myself upgrading to lithium on that system until my cars are all electric too. Is this not a valid scenario?

Lead acid is 160+ years old and still being made. Same is true for incandescent bulbs btw. (Look in your oven.) It's on its way out for sure and completely obsolete in some applications (laptops...) but it'll hang on on in others for a while yet, including some backup solutions, and not only for stupid reasons.

 

[Speedster]

Useful information, especially about incremental upgrade. But this is a bold conclusion.

Tell me what's wrong with this model - for a smaller system, budget R 5k: I see I can get ~600 Wh lithium (480 Wh usable at 80% DoD) or ~2400 Wh lead acid (480 Wh at 20% DoD).

This is parity, if we agree on the DoD-lifecycle equivalence of 80-20. Your point about upgradeability favours Li and my point about flexible DoD favours lead.

Right now, I would go lithium for this system if I needed no more than 150 W over 4 hours. But at 200 W over 2 hours, with the option to survive 4+, it looks like lead is currently still winning.

What have I missed?

And that's before other factors. I have a "dead" car battery which is 10 years old, repurposed at no cost to power my router UPS for the last 3 years. Still handles 4 hours and can go to 12 once or twice a year. I will have another dead acid to replace it with when it does finally fail, so I don't see myself upgrading to lithium on that system until my cars are all electric too. Is this not a valid scenario?

Lead acid is 160+ years old and still being made. Same is true for incandescent bulbs btw. (Look in your oven.) It's on its way out for sure and completely obsolete in some applications (laptops...) but it'll hang on on in others for a while yet, including some backup solutions, and not only for stupid reasons.

Firstly, the lithium option will last multiple times longer than the lead acid combination. Lithium also charges faster (which is important under high load shedding stages).

Regarding your use of you car battery (which is pretty clever, by the way) that's a different argument to buying. Obviously using what one had is first prize, but if you were to buy a battery for that purpose a lithium one would get you a lot further for the same price.

 

[AlphaJohn]

Useful information, especially about incremental upgrade. But this is a bold conclusion.

Tell me what's wrong with this model - for a smaller system, budget R 5k: I see I can get ~600 Wh lithium (480 Wh usable at 80% DoD) or ~2400 Wh lead acid (480 Wh at 20% DoD).

This is parity, if we agree on the DoD-lifecycle equivalence of 80-20. Your point about upgradeability favours Li and my point about flexible DoD favours lead.

Right now, I would go lithium for this system if I needed no more than 150 W over 4 hours. But at 200 W over 2 hours, with the option to survive 4+, it looks like lead is currently still winning.

What have I missed?

And that's before other factors. I have a "dead" car battery which is 10 years old, repurposed at no cost to power my router UPS for the last 3 years. Still handles 4 hours and can go to 12 once or twice a year. I will have another dead acid to replace it with when it does finally fail, so I don't see myself upgrading to lithium on that system until my cars are all electric too. Is this not a valid scenario?

Lead acid is 160+ years old and still being made. Same is true for incandescent bulbs btw. (Look in your oven.) It's on its way out for sure and completely obsolete in some applications (laptops...) but it'll hang on on in others for a while yet, including some backup solutions, and not only for stupid reasons.

 

[Tomtomtom]

Just one other quick point about economic factors that favour making the "wrong" tech choice - say you have a gate motor or alarm system in a place you're only staying 2-3 years. Is there a lithium 7 Ah drop-in replacement that costs < R 300?

 

[PsyWulf]

Just one other quick point about economic factors that favour making the "wrong" tech choice - say you have a gate motor or alarm system in a place you're only staying 2-3 years. Is there a lithium 7 Ah drop-in replacement that costs < R 300?

Lithiums are 1k but should last 10+ years

 

[Speedster]

Lithiums are 1k but should last 10+ years

He wants to save money by buying something that'll only last a couple of years.

 

[AlphaJohn]

Lithiums are 1k but should last 10+ years

We bought em at Makro for R800

Makro Online Site | Makro South Africa | Never Miss a Deal. Get the Best Deals

 

[AchmatK]

As mentioned, reusing what you have is different to buying.

The video linked above goes into much more detail.

At this point the up front cost of lithium is not that much more than lead acid and when you size a lead acid battery bank at 3 to 4 times that of lithium, the lead acid costs a lot more than lithium up front and even more over the lifespan of the battery.

The only thing standing in the way of lithium is the charging capabilities of devices like garage motors and alarm systems that cannot always charge lithium drop in replacements.

If more of these devices can charge lithium there will be no need for the 7Ah lead acid batteries that these devices use.

Just needing to run a 300w load on lead acid requires a lead acid battery bank of 12kWh discharging to 50% over 20 hours.

 

[AchmatK]

He wants to save money by buying something that'll only last a couple of years.

I like the Afrikaans saying, goedkoop is duur koop.

That 7Ah lead acid is not going to last a month of stage 6 load shedding.