Lithium or AGM batteries

[pspspeed]

Your expert opinion is required. I currently have 4 x 100Ah batteries on a Axpert 5kva/4kw system - I want to increase my standby times by doubling up on the batteries but want to know if it would be better to go for 1X3.5kw Lithium battery.  The system is mainly for load shedding use. Normal current draw from the house is around 500/600w.  4 x solar panels @330W are used during daylight times.

 

[pspspeed]

No opinions - wow?

[Energy-Jason]

Hello there. I'm sure a member with experience on your kit will reply soon.

Sincerely.

J

[___]

1 hour ago, pspspeed said:

No opinions - wow?

Oh I have some opinions alright...

1 hour ago, Energy said:

Hello there. I'm sure a member with experience on your kit will reply soon.

That was the thing. I saw "Axpert" and figured I'll let one of the Axperties answer it...

You probably already know that 100Ah at a nominal 50V or thereabouts (because it makes the math easy) is 5KWH, but because you generally keep lead acid batteries above 50% it only really leaves you with 2.5kwh storage. So your suggestion of going to a 3.5kwh module is really somewhat of a sideways move, because with these you really still want to stick to 80% DoD or less. It's not really going to give you that much more capacity. If you want to at least increase your capacity a little bit, I'd suggest going with two of the 2kwh modules or even two of the 3kwh modules.

Alternatively, you could go with 4 x 200ah batteries (the Axperties will tell you that 100Ah really is a bit small for these), and that will definitely increase your capacity while leaving you in more or less the same position otherwise. Your loads are relatively small and for short periods, so while LFP is definitely the winner in terms of cost per kwh, this isn't necessarily a bad move... just know that you will be back with this decision in the next 12-24 months

Edited January 19, 2019 by plonkster

[Guest]

1 hour ago, plonkster said:

I saw "Axpert" and figured I'll let one of the Axperties answer it...

Ditto.

My take on Lithium is that they are really breaking new ground, everything appears on par and it is very exciting.

BUT ... the tech is brand new. I'm waiting for the first banks to be replaced to see if the marketing material tied up with real life use.

Like with decades old tried and tested batteries like i.e Trojan AGM's with 1700 cycles to 50% ... costs a bit more than the Lithium's.

And they can last +-10 years if used properly.

So is it new tech you want or tried and tested? That is the choice to make.

[___]

16 minutes ago, The Terrible Triplett said:

BUT ... the tech is brand new. I'm waiting for the first banks to be replaced to see if the marketing material tied up with real life use.

There is a balance/tipping point involved. At some point it is cheap enough that you are prepared to take the chance even if the claims don't stack up. For example, you might say that even if it lasts only 7 years instead of the claimed 15... at the price it might still make sense (though I don't think we're quite there yet). I don't think you should (or even will) wait the whole 7-15 years before making the jump. Also, typically the decision is event-driven, just like the installation of a solar water heater is often driven by the prior event of a burst geyser

They are also pretty well tested in some applications already. Where their entire capacity is used in very short time spans (80%-100% on each cycle), we already know they last 2000 cycles. We also know that similar chemistries used in other applications (Tesla, higher energy density) typically lasts 3000 cycles before reaching the 80% mark. So my feeling is that most LFP batteries on the market today will do at least half as good (or better) than their advertising says. Per (advertised) cycle they are already cheaper... so less than 50% to go before they reach the tipping point.

But back on topic: We're talking about a UPS here, a load-shedding rig. And there is always the issue of buying something that makes expansion possible (adding more modules later), and then not doing it... and then you're stuck with an old battery some years later when you do want to upgrade and other things are on the market by then. So I am half inclined to tell @pspspeed to install good quality 200Ah AGMs and be done with it... until next time

[Guest]

Ja, same here. Go for AGM's. If they don't die fast enough, want to buy new, then simply use them harder, get the ROI. :-) 

FWIW, a PF member contacted Trojan direct a few years back. Trojan batteries are rated same ito cycles before reaching the 80% mark he told me.

By the time my T105RE's are done, lithium's would have been around for a while - and commonly available in 24v packs. 

Am not saying don't buy lithium's, just saying I'm waiting and why I'm waiting a wee bit longer - waiting like maybe for say some Trojan Lithium's to arrive.

Then I have a very old tried and trusted supplier behind the new lithium tech - win win if you ask me. 

 

Today's mad rush to find a solution, my gut tells me the consumers are the test beds / on the fly development of the new lithium ranges therefor the exceptional good pricing. Few years from now they may move out of SA / Africa or bring the new products in at a price that has that horrible name that everyone uses to justify high prices i.e. "market related", which when translated means: We push the price up until the sales drop, then step back a bit ... try again later to go higher.

 

[PaulinNorthcliff]

On 2019/01/18 at 1:01 PM, pspspeed said:

Your expert opinion is required. I currently have 4 x 100Ah batteries on a Axpert 5kva/4kw system - I want to increase my standby times by doubling up on the batteries but want to know if it would be better to go for 1X3.5kw Lithium battery.  The system is mainly for load shedding use. Normal current draw from the house is around 500/600w.  4 x solar panels @330W are used during daylight times.

 

If you look at the topic I opened yesterday "Solar in a container" I have mated an Axpert 5Kva to a pair of 2.4Kw Pylons.

I also have a system installed at my house with a Goodwe 5048 and four 2.4Kw Pylons... I'm going to be adding several 3.5 Pylons to this over the coming year as cash becomes available.

For me the question is an absolute no-brainer. I HATE revisiting my work (I'm at the bone idle end of the lazy spectrum). LiPo ALL the way.

[PaulinNorthcliff]

2 hours ago, The Terrible Triplett said:

I'm waiting for the first banks to be replaced to see if the marketing material tied up with real life use.
 

I honestly probably don't have 20 years to spare. ;-{>}

[Jaws]

My vote would go to  Lithium batteries without a doubt . The last few months  I have replaced quite few Lead batteries that didnt even come close to their " manufacturer claims" leaving me feeling like the idiot for recommending them 3 or 4 years ago.

Plus the installs looks so much neater with a  lithium battery.  Much less wiring and space being taken up.

 

 

 

 

[Guest]

7 minutes ago, Jaws said:

... recommending them 3 or 4 years ago.

That makes me wonder:
How long ago did the lithium's start appearing in the market for us to buy? 1-2 years maybe, no?
How old is the oldest bank here on PF?

Trojan banks last +-5 years in golf carts and forklifts. Assuming the 3-4 years are Trojan's, then those where seriously overused or under charged banks, is what I would hazard to guess.

[___]

2 hours ago, The Terrible Triplett said:

How long ago did the lithium's start appearing in the market for us to buy? 1-2 years maybe, no?

Oh goodness no! They started to become more affordable maybe 1-2 years ago, but residential lithium batteries have been with us at least half a decade. A bit of research confirms that LG started making the RESU around 2013!

The RESU is however a slightly different construction, it is NMC (similar to Tesla's battery). From Tesla we also have some stats already. But LFP will do better than NMC for cycle life.

Oh, but Mr. Plonky, don't you have LFPs yourself? (I do). Isn't your answer coloured by your need not to be wrong about that decision? (maybe). Fine... then go buy your lead batteries!

[pspspeed]

Ahh thanks guys for the replies - while my system is still new I can possibly get rid of my 4 x 100ah AGM's at a decent price. I think I am going to take the plunge and get 2 x 2.4kw Lithiums - that should keep me for a while. As Jaws also said - they look so much neater and yes, I am cycling the batteries during the day - running on solar and battery before it pulls in eskom if the clouds get in the way.

[Guest]

1 hour ago, pspspeed said:

2 x 2.4kw Lithiums - that should keep me for a while.

Good choice PSP, you have heard all sides and made a choice. Good one if you ask me.

2 hours ago, plonkster said:

maybe 1-2 years ago,

Ditto. When the Pylontech's and all the "new home affordable" lithium's came onto the market.

Point is that they are relatively quite a brand new solution, the NEW AFFORDABLE ones, so there is NO record if they will last 20 years or 2.

My gut tells me they are designed and developed on the fly compared to i.e. Powerwall, Tesla and other electric car batteries that are quite expensive = well researched and tested.

2 hours ago, plonkster said:

Fine... then go buy your lead batteries!

Like I said ... Trojan lithium's, once mine are done and dusted. 

Once they hit 80%, will run the system on "Keep charged" for another while longer - unless Eskom failures come back - which I suspect is not going to happen soon.

 

Ps. Someone I know wants to import a 2nd hand electric car batteries for use on his Multiplus II, the ones that are at 80%, insufficient for a vehicles but not for a home.

Edited January 19, 2019 by Guest

[Power Punk]

I think there are a few points deserving comment here:

1. It is not good practice to add new lead acid batteries to an existing used bank.  Batteries age both with time as well as with discharge cycles, and as they do, they take, hold and deliver energy at a decreasing rate. Adding a bank of fresh batteries in parallel with your existing ones will result in disparate charging between the two.  This can be managed to a degree, but is not ideal.  Top quality flooded batteries like Trojans are apparently less susceptible to this than your typical SLA or AGM block. This, incidentally, is one of lithium's great advantages - you can pretty-much add capacity whenever you like, as the BMSs manage the batteries at cell-level.

2. For a backup application, you need to pay attention to the "C" rating of your battery - this tells you how much energy you will get out of the battery at a particular rate of discharge.  Most lead acid batteries are rated at C10, some at C20 - in other words, a 100Ah (C10) battery will be able to give you 100Ah of energy when discharges over 10 hours WHEN NEW.  For a power backup application, and in particular load shedding, we are typically looking at a 2-3 hour backup requirement.  A typical 100Ah AGM battery would have a C3 rating of 80Ah. Most lithium batteries are rated at C1, but warranty requirements may limit use to C2, which is still fine.

3. Whilst the economics of total energy of Lithium is a clear winner, you need to be aware of your maximum power requirements.  The greater discharge depth of lithium allow a smaller battery to be utilised, but there is a limit to the continuous maximum power that can be drawn.  For example, the Pylon 3.5kWh battery coupled to an Axpert inverter (no communication) must be limited to a 37A (1.75kW) continuous discharge rate, to comply with warranty conditions. If you have a larger capacity inverter you can control this by installing a suitably rated circuit breaker on the inverter output (effectively de-rating the inverter), which can be increased at a later stage if you decide to add more battery.

3.As @DaveSA indicated, you need to decide whether you intend to cycle your batteries.  In brief, if you want to make use of your solar panels, you need to cycle the batteries.  If you intend to cycle, you need to go lithium. It's as simple as that, if you have grid power.  There is no lead acid battery which offers a warranted cost/kWh which is cheaper than grid power.

In summary, I would recommend lithium over lead acid in all but the most basic backup setups, assuming budget allows, the inverter is compatible, and you are sure of your energy and power requirements.  Its also useful to remember that you will be comparing capacities of the various batteries when new, but due to the significantly longer cycle life of lithium, the difference in usable energy after a year or two can become increasing disparate in lithium's favour.

Enjoy!

 

[Jaws]

Very good post Power Punk

[Power Punk]

42 minutes ago, The Terrible Triplett said:

Ps. Someone I know wants to import a 2nd hand electric car batteries for use on his Multiplus II, the ones that are at 80%, insufficient for a vehicles but not for a home.

I was so buys penning my tome above, that I missed the half-dozen posts in between .

2nd Life LiFePo4 batteries are already available in limited quantities locally.  I did some tests last year on a 7.5kWh bank last year, and am now running a 10kWh bank on a permanent basis.  I cycle the battery fully on a daily basis (100%-0%-100%) for self consumption (I charge exclusively from solar, with small discharge / charge cycles throughout the day, followed by complete discharge  through the night, at a typical discharge power of 1kW and up to 4kw at peak.  I have almost become "grid neutral" as a result (I now use between 1.2 and 3 kWh per day 

[Power Punk]

3 hours ago, plonkster said:

residential lithium batteries have been with us at least half a decade

Not only this, but the EV market in China is already quite mature, with early buses and taxis approaching 10 years now - and hence the emergence of the 2nd Life battery market.  Taking the plunge on lithium (be it "virgin" or 2nd Life) is not nearly as risky as some would have us believe.  There is currently no evidence to suggest that Lithium batteries are doomed to catastrophic failure at some point in their life cycle (EV track record shows us this), and so in the case of 2nd Life you are simply getting in at a different point of the energy-density curve.  As confidence grows, warranties are being extended (BYD now warrants their EV batteries for 12 years). The technology itself also mitigates risk - the BMS of a lithium battery will intervene to contain a problem cell, as opposed to an unmonitored LA bank which can be entirely destroyed in a short time by a dead cell or other undetected malady.

[Guest]

3 minutes ago, Power Punk said:

2nd Life

What kind of costs are one approaching with 2nd life electric car batts?

[Guest]

45 minutes ago, Power Punk said:

you need to be aware of your maximum power requirements. 
there is a limit to the continuous maximum power that can be drawn. 
Pylon 3.5kWh battery coupled to an Axpert inverter (no communication) must be limited to a 37A (1.75kW) continuous discharge rate, to comply with warranty conditions.
If you have a larger capacity inverter you can control this by installing a suitably rated circuit breaker on the inverter output (effectively de-rating the inverter).

This is a titbit that I think must be made a Post-It as it is not something one would think naturally when you have a larger capacity inverter for the house, during a power failure.

I mean, on my Multigrid, the 24v T105RE's are sometime hitting 1.2kW - ja ja, I know.

It is only till the VenusGX software is sorted to limit the battery draw when grid tied. And there we have @plonkster thinking "Damn, he is still at it." :-) 

[Power Punk]

13 minutes ago, The Terrible Triplett said:

What kind of costs are one approaching with 2nd life electric car batts?

Recommended retail price for a 10.24kWh battery is R49600 inc VAT.  This is for the battery (2 x 25.6v/200Ah blocks), an external BMS and a cable package.  The batteries are rated for 100% DoD, so they work out to R4 844 per kWh.

This compares with Pylon's 2.4kWh battery, which sells online for R16 000 inc VAT.  The pylon is warranted at 80% DoD, so this battery has 1.92kWh usable, translating into a cost of R8 333/kWh.

The 2nd Life really are an exciting value proposition.

Edited January 19, 2019 by Power Punk
added photo

[Guest]

11 minutes ago, Power Punk said:

The 2nd Life really are an exciting value proposition.

At that price, yes they are!

if Eskom does come back with a vengeance, and it becomes the new norm, it would be a serious tossup between the then new Trojan lithium batteries and 2nd life.

Pylontech and other newer ranges just do not grab my attention as much.

[seant]

Or Nissan leaf but then you need a car and a bit worth of battery packs to make a 48v system or folks buy wrecked tesla cars for the 18650 packs . If you are in a country there are a large number of EVs then you have plenty of choices for salvaged battery packs either from damaged cats or from battery swop outs .

[Fuenkli]

Another big advantage if you have lithium batteries is that you do not have to worry about partial stage of charge.  Going through a Cape Town winter with lead acid batteries opened my eyes! 

[___]

2 hours ago, Fuenkli said:

Going through a Cape Town winter with lead acid batteries opened my eyes!  

Oh I remember the 90s. In July 1996 I visited for a week... and that entire week was rainy and wet and I started to understand why the Germans sang so much about the sun in "Das Südwesterlied". The end of the 90s and even the early naughties was more of the same, as student I worked security patrol sometimes... and many many nights we used to walk in the rain, being slowly soaked from below where the umbrella didn't cover you as well.

And then it was as if someone turned off the rain (to quote Forrest Gump)... and since around 2013 when I installed my solar system I haven't had much trouble charging batteries.

But yes... on that odd cloudy day or two... a lead acid bank can sit there all day taking all the charge the sun can provide (10% of normal)... and effectively get absolutely nowhere. It all goes to waste. With LFP it certainly is much different.