What batteries for a 5kva inverter/charger

[Fluffy]

The other half of the story will be that the lead acid (2 x 200Ah) would have provided 4800Wh vs 2400Wh for the lithium for the rainy last 7 days.

Each one has it's place. Daily cycling vs storage for rainy days. One of the few long periods in summer time with low PV.
Attachment 604169

Aaah - somebodies awake.

Lithium - nice - but be aware, it's not all roses.

[the_terrible_triplett]

Typo fixed, that you Ekkekan!

Yes, daily cycled lithiums needs an eye to be kept on Eskom planned failures, it is quite manageable.

So as Fluffy said, horses for courses.

Me, I'm done with lead acid, daily cycled batteries to shave off more Eskom usage for we have more Eskom-On days than Eskom-Off days, as Ekkekan has also pointed out over various posts.

[the_terrible_triplett]

The other half of the story will be that the lead acid (2 x 200Ah) would have provided 4800Wh vs 2400Wh for the lithium for the rainy last 7 days.

2 x 200ah in 24v = 24 x 200 = 4800, correct.
BUT ... 50% DOD for lead acid makes it 4800 x 50% = 2400 if lead acid is 100% used.
Ideally lead acid max cycles are at 80% SOC (20% DOD) = 960 to last the guestimate of +-5 year with ease having some "spare" all the time.

Vs

24 x 100 for lithium at 100% usage = 2400
Or at 80% usage = 1920

Anyhow ... moving on for the options have been presented, new ideas shared, mistakes corrected and it is left for the poster to decided what works bests, what's best usage of monies spent and what fits the budget the best.

[ekkekan]

With the current 8 days already with low PV and another 5 forecasting it might be 13 in total. This does not happen a lot.
Jan 2021 gave the lowest PV yield in 7 years.

[Richard Mackay]

Yes he did, well spotted.

To make things even worse , the 2 x 200AH gives more than twice the capacity and safety factor for a rainy day than 1 x 24V 100AH Lithium.

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When it comes to these choices it really is horses for courses. Li is OK for daily cycling, but Lead Acid performance is far superior for UPS/Standby/Leisure duty cycle.

Please elaborate on this because this is not generally accepted.

[ekkekan]

Please elaborate on this because this is not generally accepted.

Perhaps not generally accepted as lead acids are cycled to 50% DOD. The use of lead acid can provide 160Ah+ for those few times when you want to cycle to 80%+ DOD during prolonged rain and thick cloud. A few times should not hurt deep cycle lead acid.
This is what I understand with the answer.

[Fluffy]

Please elaborate on this because this is not generally accepted.

On a daily cycle you can use about 80% of the capacity of the lithium and probably at max 50% (30% actually) of a Lead Acid Deep Cycle. This allows you to use a lithium battery of about half the size of a Lead Acid for the same performance when round tripping daily.

So for example, where a Lithium might get away with a 100AH battery for a particular profile, you would need double that capacity (200AH) for a Lead Acid for the same profile.

However if we compare a 100AH Lithium vs a 200AH Lead Acid, the Lead Acid has twice the capacity for those rainy days, or an emergency, where you can discharge it all the way to almost 0%. Quite simply, if you are prepared to discharge all the way, the Lead Acid in my example has twice the capacity.

Now you cant round trip a Lead Acid daily down to 0% (or eg 10-20%), you certainly can do it a few dozen times in it's life, as long as you charge it again fairly soon. And fairly soon is a few days grace, not hours.

--------------------------

This is one of the biggest problems with Lithium installations, especially these portable packs that are becoming popular. They do the job nicely, but if you are using that 80% capacity daily when camping you have almost zero spare capacity. An equivalent Lead Acid system that is only round tripping 30- 50% of its capacity has a HUGE safe spare capacity.

[Richard Mackay]

With all the buzz about Lithium batteries it's difficult to argue the case for lead acid batteries (which there no doubt is!)
I liked Battery University's considered comment in this regard:

Lead acid stands its ground as being a robust and economical power source for bulk use. Even though Li-ion is making inroads into the lead acid market, the demand for lead acid batteries is still growing. The applications are divided into starter batteries for automotive, also known as SLI (20%), stationary batteries for power backup (8%), and deep-cycle batteries for wheeled mobility (5%) such as golf cars, wheelchairs and scissor lifts.

[Nambro]

Mm. I used 2x 105 lead acid in my camping setup. Running 2 freezers. The problem with fully cycling a lead acid is that you will not get it full again. That is why after 5 to 6 days your second battery system starts to cave in. I tossed the lead acids and went lithium. Huge difference. The battery never went below 90% with the same solar panel and setup. Not even a lithium profile DcDc charger. I let it run to 10% and it is quick to reload. Lead acid takes ages.
Maybe I am busy believiñg my own ### st...s or it is true. All I know is that it surpases lead acid perfomance by miles.

On a daily cycle you can use about 80% of the capacity of the lithium and probably at max 50% (30% actually) of a Lead Acid Deep Cycle. This allows you to use a lithium battery of about half the size of a Lead Acid for the same performance when round tripping daily.

So for example, where a Lithium might get away with a 100AH battery for a particular profile, you would need double that capacity (200AH) for a Lead Acid for the same profile.

However if we compare a 100AH Lithium vs a 200AH Lead Acid, the Lead Acid has twice the capacity for those rainy days, or an emergency, where you can discharge it all the way to almost 0%. Quite simply, if you are prepared to discharge all the way, the Lead Acid in my example has twice the capacity.

Now you cant round trip a Lead Acid daily down to 0% (or eg 10-20%), you certainly can do it a few dozen times in it's life, as long as you charge it again fairly soon. And fairly soon is a few days grace, not hours.

--------------------------

This is one of the biggest problems with Lithium installations, especially these portable packs that are becoming popular. They do the job nicely, but if you are using that 80% capacity daily when camping you have almost zero spare capacity. An equivalent Lead Acid system that is only round tripping 30- 50% of its capacity has a HUGE safe spare capacity.

[Fluffy]

Mm. I used 2x 105 lead acid in my camping setup. Running 2 freezers. The problem with fully cycling a lead acid is that you will not get it full again. That is why after 5 to 6 days your second battery system starts to cave in. I tossed the lead acids and went lithium. Huge difference. The battery never went below 90% with the same solar panel and setup. Not even a lithium profile DcDc charger. I let it run to 10% and it is quick to reload. Lead acid takes ages.
Maybe I am busy believiñg my own ### st...s or it is true. All I know is that it surpases lead acid perfomance by miles.

Unfortunately there is a very large possibility that you are busy believing your own ###

Also possible you had some other problems.

You see the thing is, it doesn’t matter what battery you have, averaged out over one cycle or more, battery state is a function of how much energy you put in (your solar panels that didn’t change) vs how much power you use.

For the same capacity battery, if you still have 90% left it would be the same for lead acid or lithium, 90%.

Similarly charging from 10% it becomes a function of how good your charger is. At the end of the day, literally, if you only generate xx kWh, you will only accumulate (store xx kWh), independent of what the battery final started of charge is.

For sure, if you have a battery with huge safety factor and you are forced to consume it, you will probably battle to replenish it, given you are using the same system that got you into the deep water in the first place. Again, practically independent of battery technology, but the same capacity.

The only tangible difference between the two is the lead acids initial reluctance to take charge from very flat. But a decent system would be designed and capable of recovering from that.

It’s all very well having a battery with a very high charge capability (like lithium), but if you can’t produce the grunt to do so, it’s a mute point.

No doubt you are happy with your lithium’s, and so you should be, but the figures you offer are just not possible with a working setup. There was (is) something else at play.

[the_terrible_triplett]

Unfortunately there is a very large possibility that you are busy believing your own ###

Also possible you had some other problems..

Fluffy, you are probably right ito:
- "other problems" BUT not ito "busy believing your own ### ".
- You are 100% right in saying that if one uses a lithium bank to 30%, vs 50% ito lead acid, that you have little to no reserves.
- You are 100% correct saying that lithium's preform so much better IF cycled daily, and not in a UPS's or used couple of times a year in a camping system.

BUT ... if you push your bank to 30%, you KNOW you have little to no reserves. Compare apples with apples.

You make the point of 100AH Lithium vs a 200AH Lead Acid, BUT ...
1) to get a accurate SOC/DOD on a 200ah lead acid bank vs a 100ah lithium bank is nowhere even close to assuming being accurate vs a BMS on a lithium bank that "gets" it closer. So no wonder lead acid user are disgruntled ito their banks are not "lasting" as advertised.
2) A lithium bank recharges at a fraction of what a lead acid bank takes can i.e a 48v 225ah lead acid bank cycled daily recharged at 15% = 34a charge vs 100amps on a lithium bank, even at 10% SOC, 90% DOD. EXAMPLE.
3) A lithium bank has no absorption phase ... a BIG key point ... which a lead acid so needs.

Me, don't compare apples with oranges. Factor ALL the variables in.

Ps. My friend said I need to say something ...

[the_terrible_triplett]

It’s all very well having a battery with a very high charge capability (like lithium), but if you can’t produce the grunt to do so, it’s a mute point.

You are 100% correct.

BUT ... if people are educated ito the difference of the charging aspects between lead acid and lithium's, that would be more beneficial than focusing on one technologies benefits i.e. lead acid, dishing lithiums.

Lead acids wants TLC, slow and consistent amps, with a absorption phase that takes a very long time.
VS
Lithium's that absorb whatever you give them ito amps, the BMS regulating that and charge amps dropping off a cliff when nearing fully charged ... no absorption.
A BMS controlling lithium's vs a BMV that lead acids banks don't tend to have.

Ps. I mentioned lead acid and a BMV a few times ... lithium's have a BMS ... both giving the user salient crucial data to make the banks lost longer.

Me, I'm suggesting, if you have a lithium bank, check the max charge amps they can take and match that as close as you can with panels and MPPT, DEPENDING on ones daily draw.

Apples vs oranges.

PSS:I used to believe in Trojan T105RE's for daily cycling ... I'm so over that since I went lithium. You will be too one day.
Even my camping system lithium banks are feeding the house circuits each and every night, recharged via solar daily ... yes, a HOBBY!

[Richard Mackay]

My understanding of the efficiency of a charge cycle between Li-Ion and lead acid is that Li-Ion wins hands down.
So the energy you have to put into a lead acid battery with the absorbtion and float phase is energy wasted in heat and whatever.
Li-Ion on the other hand doesn't require this at all.
i would like to know what energy is lost with a full round trip with lead acid... (10% comes to mind but my mind is suspect these days!)

[Nambro]

Ok, so in addition to believing my own bs, there is some truth (actually a lot) in what I believe. Not to mention space and weight savigs

You are 100% correct.

BUT ... if people are educated ito the difference of the charging aspects between lead acid and lithium's, that would be more beneficial than focusing on one technologies benefits i.e. lead acid, dishing lithiums.

Lead acids wants TLC, slow and consistent amps, with a absorption phase that takes a very long time.
VS
Lithium's that absorb whatever you give them ito amps, the BMS regulating that and charge amps dropping off a cliff when nearing fully charged ... no absorption.
A BMS controlling lithium's vs a BMV that lead acids banks don't tend to have.

Ps. I mentioned lead acid and a BMV a few times ... lithium's have a BMS ... both giving the user salient crucial data to make the banks lost longer.

Me, I'm suggesting, if you have a lithium bank, check the max charge amps they can take and match that as close as you can with panels and MPPT, DEPENDING on ones daily draw.

Apples vs oranges.

PSS:I used to believe in Trojan T105RE's for daily cycling ... I'm so over that since I went lithium. You will be too one day.
Even my camping system lithium banks are feeding the house circuits each and every night, recharged via solar daily ... yes, a HOBBY!

[Mtber]

My understanding of the efficiency of a charge cycle between Li-Ion and lead acid is that Li-Ion wins hands down.
So the energy you have to put into a lead acid battery with the absorbtion and float phase is energy wasted in heat and whatever.
Li-Ion on the other hand doesn't require this at all.
i would like to know what energy is lost with a full round trip with lead acid... (10% comes to mind but my mind is suspect these days!)

Lithium Ion or Lithium Iron?

Yes, they are pronounced similar.
No, they are not the same.

[Fluffy]

Lithium Ion or Lithium Iron?

Yes, they are pronounced similar.
No, they are not the same.

I have it on good authority that a metric tonne of Ion occupies a much larger volume that a metric ton of Iron.

[Fluffy]

Fluffy, you are probably right ito:
- "other problems" BUT not ito "busy believing your own ### ".
- You are 100% right in saying that if one uses a lithium bank to 30%, vs 50% ito lead acid, that you have little to no reserves.
- You are 100% correct saying that lithium's preform so much better IF cycled daily, and not in a UPS's or used couple of times a year in a camping system.

BUT ... if you push your bank to 30%, you KNOW you have little to no reserves. Compare apples with apples.

You make the point of 100AH Lithium vs a 200AH Lead Acid, BUT ...
1) to get a accurate SOC/DOD on a 200ah lead acid bank vs a 100ah lithium bank is nowhere even close to assuming being accurate vs a BMS on a lithium bank that "gets" it closer. So no wonder lead acid user are disgruntled ito their banks are not "lasting" as advertised.
2) A lithium bank recharges at a fraction of what a lead acid bank takes can i.e a 48v 225ah lead acid bank cycled daily recharged at 15% = 34a charge vs 100amps on a lithium bank, even at 10% SOC, 90% DOD. EXAMPLE.
3) A lithium bank has no absorption phase ... a BIG key point ... which a lead acid so needs.

Me, don't compare apples with oranges. Factor ALL the variables in.

Ps. My friend said I need to say something ...

I sure hope a lithium bank has an absorption phase, otherwise it is a dead duck.

[the_terrible_triplett]

I sure hope a lithium bank has an absorption phase, otherwise it is a dead duck.

Good point ... for clarification, I was referring to lead acid charge cycle:
Bulk to +-85% SOC, dependent on type of lead acid, some even 80%, is open throttles all the way.
Absorption 85% to 100% SOC takes quite a long time as the volts stay same, but the amps keep on dropping until the battery is full.
Float or "trickle charge" to keep it at 100% SOC for days, weeks or longer.

And then with some vented lead acid batteries, the Equalization charge. Another story that.

Vs Lithium's going flat out till the BMS says: Enough! Slow down a bit - depends on cells, BMS but seem to start at around +-95% SOC ... to avoid cell/s voltage/s running away on higher SOC.
And you don't have to go 100% SOC either, can stop at say 95%, and be done.
OR, if one wants to go 100% SOC, it take minutes (?) from 95% to 100% SOC or where the BMS says STOP!

So no real "Absorption" phase really.

FWIW, software on my Venus controls the charge amps on the inverter, before the BMS needs to act:
SOC >=100 then Charge_Current = 0amps
SOC >98 <100 then Charge_Current = 1amps
SOC <95 <=97 then Charge_Current = 4amps
SOC <=95 then Charge_Current = MAX charge amps set, mine is 60amps

Also can work in "reverse" i.e. on a low SOC.
IF SOC:
<=20 - discharge_current = 5amps
>20 <=30 discharge_current = 60amps/4
<30 <=35 discharge_current = 60amps/2

IF one wants to do that, I removed the above, I drop the max inverter wattages rather than lowering the discharge current.

[Richard Mackay]

Lithium Ion or Lithium Iron?

Yes, they are pronounced similar.
No, they are not the same.

I have also been had with these names. Very confusing
Lithium-ion (Li-ion) is a type of battery as is lead acid, Nickel metal hydride etc.
There are specific types of Li-ion batteries. Stick to the accepted abbreviations to avoid confusion!

[Nambro]

Is it not Lithium Iron Phosphate LiFePo4 commonly also known as LFP battery.

I have also been had with these names. Very confusing
Lithium-ion (Li-ion) is a type of battery as is lead acid, Nickel metal hydride etc.
There are specific types of Li-ion batteries. Stick to the accepted abbreviations to avoid confusion!