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Which batteries should I buy (rhetorical question)


Chris Hobson

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12 minutes ago, Mark said:

Can you still slot in a bmv702 between the bank and the inverter. Or does this become redundant. 

@Mark, I think it becomes redundant like a Tesla Model 3 that comes with a petrol engine as a standby when you run out of battery capacity, lol. 

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52 minutes ago, Mark said:

Related to the lithium banks.  Can you still slot in a bmv702 between the bank and the inverter. Or does this become redundant. 

You could still have a BMV. Most BMSs have a SOC reporting facility. The Pylon's is a series of six LEDs each representing 16.6% of capacity. I have it on good authority that the same man who wrote the Axpert manual wrote the PylonTech manual :D.

Addition: What will be redundant is my beloved HA02

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2 hours ago, Mark said:

Can you still slot in a bmv702 between the bank and the inverter. Or does this become redundant.

Depends. Many BMSes have built-in SoC, so you don't need the BMV. Using Victron kit as an example, I think there is enough intelligence in some of their kit  (eg Lynx Ion BMS) that you don't need the BMV, but if you use the LiFePO4 batteries with the vebus BMS, then sometimes you do need the BMV, for example when you have DC loads. If the inverter is the only load and all your MPPTs are Victron kit, then you don't need the BMV, the Multi can do proper SoC accounting. This is mostly because Peukert's law doesn't really apply anymore (it does, but the number is much closer to 1)... so it is much simpler to do it.

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3 hours ago, Mark said:

Thanks Plonkster - I guess the next question - will it do any harm? ;)

No it won't, at least I can't see that it would. Just have to adjust the charge efficiency setting I'd think.

One problem that does arise is that the BMV needs to reset at the top, when the batteries are fully charged, and lithium has no sulphation issues and generally spends a lot more time around the middle of the range, especially if you're doing self-consumption, so the BMV will tend to drift a bit.

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  • 3 weeks later...

I  Managed to get quotes from BlueNOVA and FreedomWon for Nigeria.

 

Surprisingly the BLUENOVA are marginally cheaper and have much higher current ratings ( 300 AMp against 100 AMP) than Freedomwon.  The cycle Life are comparable 

Both Work with my Blue ( Quattro) with BMS compatibility for Off grid  use 

See attached comparison on various batteries that I can lay my hands on and their estimated price points 

Any additional points I should consider before making my decision 

1. BluenOVA - Higher current ratings -. 100 % capacity is guaranteed. Higher current means I can use them with 8 or even 10 KW inverter in future. Could not find compatibility with Expert 

2. Freedomwon - Cycle life guaranteed for 70 % of capacity leaving additional 30 % for emergency use ( 10 KWH is rated at 7 KWH ) - Current is small especially I am worried between the small difference of rated ( 100 Amp)and peak currents.  ( 125 Amp)

 

 

Compare .xlsx

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27 minutes ago, ghatikar said:

Any additional points I should consider before making my decision?

The differences are essentially in the BMS. I haven't worked with either batteries in the flesh. I know that FreedomWon is putting in a lot of effort to make their battery work well with ESS. Conversely, I haven't heard anything bad about BlueNova in this area. If it was my own money I'd buy the BlueNova battery, but that would be partly because their factory is in my home town, and because the supplier I normally use (OnTrack) swears by them. Both of them have very good relationships with Victron, so you cannot really go wrong either way.

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The "low" discharge rate is actually not that strange. Usually lithium cells can do C/2 continuous discharge rates without breaking a sweat. So a 10kwh battery, at around 50V (to make the math easier) means 200Ah cells, so 100 amp is pretty normal. In contrast the currents shown for the BlueNova is C/0.5! LiFePO4 can do that... but usually not continuously. Are you sure about that number? :-)

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On 7/30/2017 at 11:44 PM, plonkster said:

SolarMD pairs their battery with the Axpert. They are the only ones though. I still feel like BlueNova or FreedomWon present better options, but I'll be completely honest and tell you how I came to this unscientific conclusion: These guys integrate with a more expensive inverter, in other words, they keep high-class company, or to put it bluntly: I judge them by their choice of inverter :-) But... on the inside, everyone fits Winston cells that come from China. The big difference is in the BMS.

Also, with some of the other batteries, the BMS sometimes have dry contacts that can be used to disconnect chargers/loads when a cell is critically high or low, so you could wire it such that the PV is disconnected when there is a high cell, or everything is disconnected on a low cell. Then all you need is a battery charger profile for the lithium cells. See for example the Victron vebus BMS that can combine with the Cyrix disconnects.

Honestly though, I feel like you should get another AGM bank and slug it out another 2 years or so. Or maybe look at L16RE from Trojan (370Ah). All that bothers me about that, is this is a 6k battery, of which you need 8. For 48k you can get a pretty decent entry-level lithium bank.

This article suggests that cost is about on par now, which suggests you need to look at high end flooded lead acid. Ie L16RE-B.

Hi, just saw this - cant help noticing when people talk about Lithium batteries.  SolarMD does not use Winston cells.  I believe what they use is a little better (but I dont know if they will like it if I tell so will leave it at that.).

cheers

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Hi again.  I did not read all the posts but since I get questions on which batteries all the time let me quickly share my conclusions:

Strategy 1:  Go cheapish now and hope prices will come down (it should).  Then get yourself some Trojan T-105REs and water them as needed and stick it out for 3-4 years.  There is no good value for money sealed lead acid option I have come across unless you get lucky like the CEIL Solatrons I pickup up a few months ago for half price.  Note:  There are MANY cheap but horrible sealed lead acid batteries out there.  I know - this is how I win 50% of my clients - they never want to speak to the people who sold them that nonsense again. 

Strategy 2:  Buy now for 8 - 12 years life.  Good value for money 2V Tubular FLA (Excide India is interesting and I have it on good authority they do 9 years and counting on 30% DOD) or Lithium.  Going rate for LiFeP)4 is R8500 per kWh ex VAT and then we just heard that Pylon is coming in at 15% less in SA now.  Pylon now also compatible with Voltronic (Axpert).  And please be sure you know what is in the Lithium battery before you compare prices.  You must find out what cells they use before you can compare.  I have seen batteries being advertised as 4kWh packs when I know for a fact it is no more than 3.6kWh based on the 16 cells in the pack.

Cheers

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1 minute ago, Hannes7212 said:

SolarMD does not use Winston cells

Good to know. I might have been overeager declaring that "everyone" does that.. not everyone, but a large number of them.

3 minutes ago, Hannes7212 said:

advertised as 4kWh packs when I know for a fact it is no more than 3.6kWh based on the 16 cells in the pack

Also see @ghatikar's post from last night about a disparity between max discharge currents between BlueNova and FreedomWon cells. Something weird is going on there...

I also previously tried to find out why the local guys speak of 7000 cycles to 70% when the overseas stuff (eg MG Energy Systems) claim a mere 2000 cycles to 80%. My suspicion is that expected lifetime and warranty-lifetime is sometimes mixed up, but I could not get a clear answer on this either.

Some numbers are coming out of Tesla car owners now, suggesting that 3000 cycles is doable. But those batteries are NMC far as I know, not LiFePO4.

So comparisons remain difficult.

(By the way Hannes, I sent someone your way, hope you could help him).

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4 minutes ago, Hannes7212 said:

Hi again.  I did not read all the posts but since I get questions on which batteries all the time let me quickly share my conclusions:

Strategy 1:  Go cheapish now and hope prices will come down (it should).  Then get yourself some Trojan T-105REs and water them as needed and stick it out for 3-4 years.  There is no good value for money sealed lead acid option I have come across unless you get lucky like the CEIL Solatrons I pickup up a few months ago for half price.  Note:  There are MANY cheap but horrible sealed lead acid batteries out there.  I know - this is how I win 50% of my clients - they never want to speak to the people who sold them that nonsense again. 

Strategy 2:  Buy now for 8 - 12 years life.  Good value for money 2V Tubular FLA (Excide India is interesting and I have it on good authority they do 9 years and counting on 30% DOD) or Lithium.  Going rate for LiFeP)4 is R8500 per kWh ex VAT and then we just heard that Pylon is coming in at 15% less in SA now.  Pylon now also compatible with Voltronic (Axpert).  And please be sure you know what is in the Lithium battery before you compare prices.  You must find out what cells they use before you can compare.  I have seen batteries being advertised as 4kWh packs when I know for a fact it is no more than 3.6kWh based on the 16 cells in the pack.

Cheers

 

If you see my comparison of costs you will find that Lion is quickly closing the GAP to Leaacid .

Lead acid is typically higher mainataince and two years warranty  while lithium is  fit and forget and 10 Year warranty - I think the small difference is   worth paying for peace of mind  especially for a person like me who is out of house 15 days in a month on the road

If You increase Lithium capacity the cost /cycle comes down as BMS and installation costs are shared. For Lead acid ( wet) the installation and maintenance costs are fairly liner to capacity 

Also, note that  often the losses resulting due to inefficiencies of Lead Acid and longer charge times are not calculated in cycle costs. Factoring those in the Lithium will make more sense  provided you can have the money to spend initially

 

Make Model price USD/Cycle/KWh
     
FREEDOMWON HOME 10/7                0.29
FREEDOMWON HOME 15/11                0.25
     
BLUENOVA BNV52V-154-8K                0.23
BLUENOVA BNV52V-230-12K                0.22
     
BattelBorn 12 V x 4                0.26
SimplyFi Power Phi 2.6 KWh                0.28
Herewin                  0.58
     
LEAD ACID Trojan RE200-B                0.20
LEAD ACID  Trojan L16-RE-B                0.15
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12 minutes ago, plonkster said:

Good to know. I might have been overeager declaring that "everyone" does that.. not everyone, but a large number of them.

Also see @ghatikar's post from last night about a disparity between max discharge currents between BlueNova and FreedomWon cells. Something weird is going on there...

I also previously tried to find out why the local guys speak of 7000 cycles to 70% when the overseas stuff (eg MG Energy Systems) claim a mere 2000 cycles to 80%. My suspicion is that expected lifetime and warranty-lifetime is sometimes mixed up, but I could not get a clear answer on this either.

Some numbers are coming out of Tesla car owners now, suggesting that 3000 cycles is doable. But those batteries are NMC far as I know, not LiFePO4.

So comparisons remain difficult.

(By the way Hannes, I sent someone your way, hope you could help him).

 Based on the price I guess Blue NOVA and Freedom won quote cycle numbers at 70 % DOD ( also warranty conditions are for 70 % DOD)

Bleunova  claims 

  • 3600 cycles @ 100% DoD
  • 5000 cycles @ 80% DoD
  • 7000 cycles @ 70% DoD

These are fairly similar to 3700 claimed by USA based SimliFi and Battelborn  and even LG Chem Resu - https://www.altestore.com/store/deep-cycle-batteries/lithium-batteries-c4441/

In contrast, the Chinese Herewin claimed only 1000 at 80 % DOD !!

I guess we will only know after few years 

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Did not see the comparison but totally agree with your logic.  I actually add 15% PV for a lead based system vs Lithium.  Let me be clear:  I prefer Lithium - its what I run at home.  I just can't stop looking at how those things soak up charge all the way up to 95% SOC before the graph tapers.

There is this one practical issue that favors lead: Lets say you have a 36kWh lead bank, you would typically compare that with a 13 - 15kWh Lithium bank.  Thing is, when the weather acts up a bit in an off grid situation you find that people are happy to stretch their PB bank beyond 30% DOD on the odd day but with Lithium when it is done it's done so in practice when you size it like that the gennie comes on more often.

Not a big deal if things are set up properly but this is a real life scenario that I see often.  Especially people who are used to lead struggle to understand this hard cut-off we force on them with Lithium.

hope that makes sense.

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11 minutes ago, Hannes7212 said:

Did not see the comparison but totally agree with your logic.  I actually add 15% PV for a lead based system vs Lithium.  Let me be clear:  I prefer Lithium - its what I run at home.  I just can't stop looking at how those things soak up charge all the way up to 95% SOC before the graph tapers.

There is this one practical issue that favors lead: Lets say you have a 36kWh lead bank, you would typically compare that with a 13 - 15kWh Lithium bank.  Thing is, when the weather acts up a bit in an off grid situation you find that people are happy to stretch their PB bank beyond 30% DOD on the odd day but with Lithium when it is done it's done so in practice when you size it like that the gennie comes on more often.

Not a big deal if things are set up properly but this is a real life scenario that I see often.  Especially people who are used to lead struggle to understand this hard cut-off we force on them with Lithium.

hope that makes sense.

@Hannes7212   I fully agree.:)

In fact, even if the Gennie comes on often it goes off also faster as the charge times are shorter with max 1 H absorb. Sometimes my lead acid sits on absorbing for 2-3 hours all the while drawing less than C20  in the night. With lithium, I can just leave it on 20 % charge and not worry about partial SOC and battery degradation.

Like computers mix SSD and spinning drive for capacity and speed, somebody should come up with Hybrid.  Lithium contributing to Charge currents and  high current discharge cycles while Lead acid contributing only to overall capacity 

 

  

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2 hours ago, Hannes7212 said:

There is this one practical issue that favors lead: Lets say you have a 36kWh lead bank, you would typically compare that with a 13 - 15kWh Lithium bank.

I agree. I often see the sales material say things like you only need a third of the capacity with Lithium Ion, but that obviously makes no room for a cloudy day. With lead-acid, the 50% you (almost) never use doubles as both buffer for a longer life AND for the rainy days. I tend to go with a 50% rule rather than the one-third rule the marketers calculate so meticulously :-)

Hybrid idea... mmh let me think about that :-)

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