I want to relplace my lead acid batteries with a Pylontech. I have 4x180 la battery in series. P=Ixv that means 8640W however the DOD is only to 44v . Uou can not use 8640w die tot the 80% DOD

 

Now how does then relate  Pylontech 2400 or3500w, how many Pylontech’s will be needed to replace my current lead acid?

Hi Kobus

Generally Lead acid should be used down to about 80% SOC, or 20% DOD.

This do differ from manufacturer to manufacturer, but for the mainstream batteries this is the safe zone.

So if you use 48V with your 180Ah, you do get to 8640Wh, but due to only 20% usable energy, that equates to 1728Wh.

PS: Typical the Pylon 2400 has a usable range of 2200, from my experience

R

Edited April 7, 20197 yr by Riaanh

Interesting, thx you have answered my question. That means i can get1 Pylontech to replace my lead acid and potentially have 500 wh hour more of usage then.

21 hours ago, The Terrible Triplett said:

It is, I meant to say if the MODEL of the Solis bought, is on the list ... just check for in case a newer model comes out that is not on "the list".

 

43 minutes ago, KobusK said:

That means i can get1 Pylontech to replace my lead acid and potentially have 500 wh hour more of usage then.

Yes. Though in an emergency, you could extend your lead acid batteries to say 50% SOC or even lower (2.5 x the safe, regular use energy), but you can't extend the lithium battery by nearly as much.

[ Edit: 250% -> 2.5 x the safe, regular use energy ] 

Edited April 7, 20197 yr by Coulomb

30 minutes ago, KobusK said:

Interesting, thx you have answered my question. That means i can get1 Pylontech to replace my lead acid and potentially have 500 wh hour more of usage then.

That would be correct, under the assumption that you only used the batteries to the 80% SOC state. If your use was aimed on really draining the batteries as example down to 50% then you would be a bit short.

R

24 minutes ago, Pietpower said:

Why do they use 20%?  Do you have more chances of battery failure if you go to 50%?

I do not really see greater chance of failure, simply expanded battery life.

I have done some calculations in a spreadsheet with the different manufacturers, and the average web pricing for the run of the mill batteries (Lith, Gel, Lead, etc) and admittedly in general Lith seems better ito R/kW usable.

There are obviously a lot to consider, but I believe the future "for now" lies in Lith technology.

Just my opinion 😉

PS: Just another point, once you get the feel for the average R/kWh, you immediately spot the fake/Scam battery sellers 😉 🤣

Specials don't run at 30 odd % of actual values

5 hours ago, Riaanh said:

There are obviously a lot to consider, but I believe the future "for now" lies in Lith technology.

Yup. There is no new battery technology coming in the next 5 years, maybe even the next decade. Of course I could well be spectacularly wrong, but there is at least nothing on the horizon. Definitely not supercaps... forget about that immediately. The battery of the (immediate) future is already here. I believe it will become a little cheaper still.

7 minutes ago, plonkster said:

Yup. There is no new battery technology coming in the next 5 years, maybe even the next decade. Of course I could well be spectacularly wrong, but there is at least nothing on the horizon. Definitely not supercaps... forget about that immediately. The battery of the (immediate) future is already here. I believe it will become a little cheaper still.

Agree. The company I work for is currently involved in this project

https://www.riotinto.com/energyandminerals/jadar-4643.aspx

As supply of lithium goes up the price should come down..

I'm currently busy on a project where a copper mine is now looking at extracting the cobalt from the tailings.  All in the name of Lithium batteries 

 

6 minutes ago, Jaws said:

cobalt from the tailings

Cobalt is a limiting factor in the Lithium batteries that are used for mobile devices and laptops. We have a limited supply of Cobalt (Lithium is however still quite plentiful). And there is presently no easy way to extract it from recycled batteries. LiFePO4 batteries however don't use Cobalt.

That is what is still missing for Lithium batteries. It needs to be as recyclable as lead batteries... that would really seal the deal.

31 minutes ago, plonkster said:

Yup. There is no new battery technology coming in the next 5 years, maybe even the next decade. Of course I could well be spectacularly wrong, but there is at least nothing on the horizon. Definitely not supercaps... forget about that immediately. The battery of the (immediate) future is already here. I believe it will become a little cheaper still.

I have to say, as much as this is true, I would actually like to have seen something new sooner than later. 

On 2019/04/06 at 3:41 PM, The Terrible Triplett said:

It is, I meant to say if the MODEL of the Solis bought, is on the list ... just check for in case a newer model comes out that is not on "the list".

 

How do you get the battery to go to 50% on DOD?

my inverter switch back on 44v.

what will the voltage be at 50% DOD?

Edited April 7, 20197 yr by KobusK

2 hours ago, KobusK said:

How do you get the battery to go to 50% on DOD?

Oh I remember this exercise from the days before I had a BMV.

The trouble is that the SOC vs voltage relation depends on the battery being open circuit when you measure it, and it must have had some time to settle. Since you cannot make it open-circuit, the best is to take the measurement while the inverter is in bypass. So you cannot use the voltage as SOC measure while the inverter is still discharging the battery, and the voltage itself is a function of both the SOC as well as the current discharge rate.

So back in the day when I was doing this, I would set a voltage and let the inverter switch (there are ways to make Victron inverters behave like axperts based on voltage), and then an hour or so later I would note the voltage. If this was a bit higher than I liked, I would adapt the switching voltage and lower it a bit. And so, over the course of some days, I found the right voltage that would yield the right "resting voltage" that corresponded roughly to the discharge level I wanted.

This also relied on another detail: That my loads were more or less similar each night around 7PM when we went back to grid.

All of this is however a hackery/kludgery and the correct answer is that you cannot do this with voltage, or more specifically, you cannot do it ACCURATELY with just voltage. It's a bit like those early British tanks that didn't have rifled barrels. It would blow up something "over there", which was often good enough, but not very precise 🙂

(Yes, stole that from Mr. Clarkson).

Edited April 7, 20197 yr by plonkster

12 hours ago, plonkster said:

The battery of the (immediate) future is already here. I believe it will become a little cheaper still.

The price have dropped already, not by much, but did. I think competition between brands can also be a good thing. My gut feel tells me that even if someone can import uch cheaper, they will still sell at market related pricing.

10 hours ago, KobusK said:

what will the voltage be at 50% DOD?

Without a BMV I would not risk that route.

 

7 hours ago, plonkster said:

Oh I remember this exercise from the days before I had a BMV.

The trouble is that the SOC vs voltage relation depends on the battery being open circuit when you measure it, and it must have had some time to settle. Since you cannot make it open-circuit, the best is to take the measurement while the inverter is in bypass. So you cannot use the voltage as SOC measure while the inverter is still discharging the battery, and the voltage itself is a function of both the SOC as well as the current discharge rate.

So back in the day when I was doing this, I would set a voltage and let the inverter switch (there are ways to make Victron inverters behave like axperts based on voltage), and then an hour or so later I would note the voltage. If this was a bit higher than I liked, I would adapt the switching voltage and lower it a bit. And so, over the course of some days, I found the right voltage that would yield the right "resting voltage" that corresponded roughly to the discharge level I wanted.

This also relied on another detail: That my loads were more or less similar each night around 7PM when we went back to grid.

All of this is however a hackery/kludgery and the correct answer is that you cannot do this with voltage, or more specifically, you cannot do it ACCURATELY with just voltage. It's a bit like those early British tanks that didn't have rifled barrels. It would blow up something "over there", which was often good enough, but not very precise 🙂

(Yes, stole that from Mr. Clarkson).

This works well but has to be redone at least once a year on lead acid batteries, as battery capacity diminish over time. That is, if you don't have a battery monitor that can intelligently give the stats back to the charger and inverter.

 

@KobusK  I think it's quite clear than having a battery monitor and something (i.e. Victron Color Control / Venus / ICCSoftware / your own scripts) to give the inverter a much better overview of your batteries, that they won't perform as well as they should.

interesting topic, this is exactly what i am trying to understand currently. I have com to understand from others that to safely and responsibly use the lead acid / gel hybrid batteries you need a BVM and ICC. so this begs the question, on a pylontech, do you need both? since the battery has built in protection? would say a BVM be enough to just ensure that you are recharging the batteries sufficiently?

9 minutes ago, Dex_ said:

interesting topic, this is exactly what i am trying to understand currently. I have com to understand from others that to safely and responsibly use the lead acid / gel hybrid batteries you need a BVM and ICC. so this begs the question, on a pylontech, do you need both? since the battery has built in protection? would say a BVM be enough to just ensure that you are recharging the batteries sufficiently?

BMV is for Lead Acid batteries. Lithiutm Ion batteries have a BMS that does the same as the BMV.

In a lead acid battery bank, the BMV tells the solar / inverter charger what the state of charge is.

In a Lithium (for example Pylontech) battery, the BMS just manages the battery. If the inverter has a RS485 port, and has firmward that's compatble with the Pylontech, you don't need anything more. Examples are Infinisolar, Goodwe, Solis. For Axpert inverters you need ICC. For Victron inverters you need Venus or Color Control.

 

5 hours ago, SilverNodashi said:

BMV is for Lead Acid batteries. Lithiutm Ion batteries have a BMS that does the same as the BMV.

There are reasons to use a BMV with Lithium batteries. We have customers using BMVs with BYD batteries... because the BYD BMS doesn't have very accurate current measurement below 1 ampere and with really small loads the SOC is often inaccurate.

Also, if you have a battery with a simpler BMS (with allow to charge/allow to discharge analog signalling and no canbus comms), then a BMV is still a good idea.