Batteries 50V vs 100V

[Bob Smith]

I'm no technical expert, I dont take statements unsubstantiated as gospel though. Everything I have seen online such as they charge quicker, they are more efficient and they have a longer life etc not a single one is substantiated in how this is achieved. The individual cells are the same as LV batteries theres just more of them. There seems to be on face value snake oil by the bucket load. I hope they work for you bring all the benefits claimed.

You are right and I tend to do the same. I like facts and data but comes a point where I have to stop digging.
Time will tell.
Well, the thing is that even if I am happy with the batteries I will never know what would have been the difference with LV...


Anyway. @MHarv already have the Triple Power and has shared already some feedback. Maybe you could ask him more technical questions? You'll have to wait months before I can give you some with mine I am afraid

 

[johnb2713]

You are right and I tend to do the same. I like facts and data but comes a point where I have to stop digging.
Time will tell.
Well, the thing is that even if I am happy with the batteries I will never know what would have been the difference with LV...


Anyway. @MHarv already have the Triple Power and has shared already some feedback. Maybe you could ask him more technical questions? You'll have to wait months before I can give you some with mine I am afraid

Not a problem good luck.

 

[bladerunnerpv]

I look forward to hearing how you get on with your shiny new HV system Bob

 

[Bob Smith]

I look forward to hearing how you get on with your shiny new HV system Bob

Thanks. You are gonna need to be patient.

1) Surveyor
2) DNO, you surely know how long this will take...
3) Installation

I hope it will be fitted for Spring... if there isn't a bad surprise in between.

 

[arwooldridge]

I have Solax HV triple power batteries, one thing they don't really highlight is the much reduced charge rate at low battery temperatures. So with a 15kw pk array I can get max 8kw on a cold December day, but the batteries (23kw string) can only take 2kw of this at the low temperatures. (Batteries in unheated outhouse close to 0degC)
Something you may need to factor in. Maybe applies to all lithium batteries. Anyway if you can place them in a heated area they will fare much better. Or add more batteries to compensate. Ideally you need alternative ways to use PV power eg EV charging to make use of the excess.

 

[Bob Smith]

Thanks @arwooldridge

Generally, all batteries are affected by ambient temperature. This is why I gave up the idea to put everything outside ( I had a nice corner out of the view and not taking place in my attic) despite some brands saying they can be installed outdoors. Of course, they will have a cover to protect them but they will be more affected by the temperature than those insides. Unless you have a pack with a heating system (I seem to have read that Tesla has this).

So as you pointed out the real question is Are the HV batteries more affected by the low and high temperatures than the LV?

It is very difficult to get any data from the manufacturers.

It is like trying to get the SoC at end of life. I only know Sunsynk provides that info on their datasheet. (quite bad 40% SoC at 10y)
once @johnb2713 shared a chart for the EEV cells . That is

I would love to see charts for:

• Loss vs time at rest
• Efficiency (power charge) vs temperature
• Loss vs time (during everyday use)

 

[MHarv]

Just reviewed (after above message by @arooldridge) the Solax App Battery stats
Days are getting colder, Solax batteries in cold double garage (not heated) attached to Utility room temp probably 1’C or lower in garage, Battery temps now 12’C; last night charge from 52% to only 92% in the Octopus Go 4 hour period, drop of 2’C from 14’C previous nights reducing charging power ampage to less than 7 amps for whole period of charge; starting charge at 5 amps 0030 hrs reaching 7 amps after two hours and 3.5 amps at 0430 hrs reaching only 92% charge.

The cold is reflecting the ability to charge at full capacity which was available last week.

So location and ambient room temps will help battery charging to full capacity

My storage is 11.6kWh capacity, a 5.8kWh single battery probably would of charged to full capacity in the Octopus Go 4 hour time period.

 

[johnb2713]

I have Solax HV triple power batteries, one thing they don't really highlight is the much reduced charge rate at low battery temperatures. So with a 15kw pk array I can get max 8kw on a cold December day, but the batteries (23kw string) can only take 2kw of this at the low temperatures. (Batteries in unheated outhouse close to 0degC)
Something you may need to factor in. Maybe applies to all lithium batteries. Anyway if you can place them in a heated area they will fare much better. Or add more batteries to compensate. Ideally you need alternative ways to use PV power eg EV charging to make use of the excess.

Lithium batteries (all lithium batteries) can incurr permanent damage if charged at below 0 degC.

"When attempting to charge a Lithium battery below 0°C / 32°F a chemical reaction called “Lithium Plating” occurs which is caused by the charge current forcing the lithium ions to move at a faster reaction rate than usual and accumulate on the surface of the anode.

When this chemical reaction occurs the internal resistance of the battery increases, which can have big consequences when linked in series or parallel connections. As well as this, another side effect to the chemical reaction is it reduces the rate of the chemical metabolism and causes a permanent reduction of the battery’s capacity. This will continue to reduce further each time this reaction occurs."

On the battery i'm making I have a temperature sensor on each group of 4 cells, they are in an outdoor insulated and heated box with a minimum temperature set at 10 deg C (a 40w heater keeps it there). If the temperature drops below 5 degC in the enclosure, battery charging is suspended.

 

[Bob Smith]

Lithium batteries (all lithium batteries) can incurr permanent damage if charged at below 0 degC.

"When attempting to charge a Lithium battery below 0°C / 32°F a chemical reaction called “Lithium Plating” occurs which is caused by the charge current forcing the lithium ions to move at a faster reaction rate than usual and accumulate on the surface of the anode.

When this chemical reaction occurs the internal resistance of the battery increases, which can have big consequences when linked in series or parallel connections. As well as this, another side effect to the chemical reaction is it reduces the rate of the chemical metabolism and causes a permanent reduction of the battery’s capacity. This will continue to reduce further each time this reaction occurs."

On the battery i'm making I have a temperature sensor on each group of 4 cells, they are in an outdoor insulated and heated box with a minimum temperature set at 10 deg C (a 40w heater keeps it there). If the temperature drops below 5 degC in the enclosure, battery charging is suspended.

so in other words. LV and HV same boat...

 

[johnb2713]

so in other words. LV and HV same boat...

Absolutely correct, it's a lithium issue NOT the number of cells.

 

[Bob Smith]

Back to case one.
What are the advantages of HV over LV?
It is frustrating that the manufacturers can't give us comprehensive specs.

 

[johnb2713]

Back to case one.
What are the advantages of HV over LV?
It is frustrating that the manufacturers can't give us comprehensive specs.

Potentially thinner cables connecting to the inverter and thats all as far as I can see. The rest of the gibberish about the inverter having less work to do is complete and utter snake oil. The batteries themselves, the individual cell size will be halved and the number of them doubled giving more connection points with the potential to fail. The BMS will need more channels 32 instead of 16, again adding more complexity.

 

[MHarv]

What about inverter voltage conversion from 52v compared 115v single battery to 230v two batteries system, if another 5.8kWh battery is added the minimum voltage for system is another 115v making the battery system 345v.

Therefore less conversion from DC to AC and vice Versa as stated in first two threads Bob included. Less work, more efficiency to produce AC voltage, both LV and HV have their own merits imho none slightly better overall than the other. Interesting topic nonetheless.

Another is inverter efficiency to run in the back ground; my Solax AC inverter is apparently running/using 50 watts per half hour from looking at 24 hour usage Which is nearly 2.4kW.. baffling at present when the battery system is running loads; whereas I think this should be a lot lower with the Grid? Solax don’t tell you this or in Specs for the running of system or could be that Hybrid inverter is more efficient than the equivalent Solax AC inverter.

Be interesting to know what other systems are getting,

Or what can be done to negate, reduce that operating wattage 0.05 - 0.08 per half hour

Again is this temperature related?

 

[Bob Smith]

I would add that the first batteries were LV and HV are relatively new especially for residential applications.
I do not think the manufacturers would launch new products and hoping that they can sustain sales only based on marketing blabla. There must, therefore, be something "better" about them since they are seen as the new thing.. And maybe the improvement is not about the capacity or the degration with lower batteries etc... but on the infra (as mentioned above, smaller cables etc...)

[..... a few minutes later.....]

I think I have found something. The more batteries you put together the higher the amps on a LV batteries while it is constant for the HV.
The higher the voltage for a HV while it is constant for a LV batteries.

I could not find specs for a 23kWh for a LV I got 20kWh. close enough

HV: 4 batteries for 23kWh. Nominal Voltage 460V, Recommended Amp = 25A. Standard Power 11.5kW.
LV. 4 Batteries for 20kWh. Nominal Voltage 51.2V, Rated charge 120A and Rated power 7.6kW

So, to me as I have an underfloor heating at 3kW and when other appliancies such as the oven, toaster and kettle are in used. I would say that the HV will better support that charge. I have no idea if what I am saying makes sense but by looking at the data this is how I understand them.

Also note that with the HV everytime you connect an additional battery the available power increases, this is not the case for LV, after the second one it is always the same power which is available.

My conclusion from this comparison:
If you need power and you know you need more than one battery, the HV batteries will give you higher dis/charge power.

Happy to be proving wrong and sent back to school to learn again

 

[MHarv]

That’s same conclusion I made but dependent on Inverter capacity Output.
My inverter is 3680w <16A G98.

Bigger inverter required for larger output 5kW to output 5000w requiring Full G99 >16A Application with extra cost implication from DNO. I never asked that question to the DNO.

 

[bladerunnerpv]

the LV batteries quote being connected in parallel in the above spec
looks like the HV are quoted being connected in series though?

IIRC
2 x batteries in series give 2x voltage, but same current as one battery
2 x batteries in parallel give same voltage as 1x, but double the current as one battery
(for same voltage batteries)

Edit:
https://www.countybattery.co.uk/battery-experts/connecting-batteries-in-series-and-parallel/

 

[MHarv]

My 2 Solax batteries total capacity 11.6kW will not deliver 7kW from Solax Battery specs above unless my Solax inverter AC-3.6 Is next model up which is Solax 5kW max output is 5000w

 

[Bob Smith]

That’s same conclusion I made but dependent on Inverter capacity Output.
My inverter is 3680w <16A G98.

Bigger inverter required for larger output 5kW to output 5000w requiring Full G99 >16A Application with extra cost implication from DNO. I never asked that question to the DNO.

Good point. I will need to ask my installer, One thing that he discounted the HV batteries but then if he put an inverter which cannot cope with the power of the batteries what will be the point!! I will be vigilant.

I estimated that my 37 panels to be (14.6kW) (16 existing and the 21 new expected) will only give max a combined power of 8 to 9kW at best because of their different orientations. The HV batteries will cope. I will start with 2 batteries and the 8 to 9 is only a rough estimate for the highest which will occur only a few days in the year. Therefore when I decide to add more batteries (if I feel it is necessary) then regardless of the inverter I will not have enough power from the panels anyway and there is nothing I can do about this (no more room to add panels).

So now, my system is a bit more complex
I already have a 3.68kW inverter (from 2016)
the new panels will be :
10 of them (total 5.05kW facing NW) on a 2 string inverter . Not sure the size of it
11 panels with micro inverter.

these 3 "set up" will need to feed the batteries. I do not know how they going to connect all this so the batteries are efficiently charged (without mentioning that the batteries will also need to be charged from the grid as and when required).

I will keep you informed

 

[Bob Smith]

the LV batteries quote being connected in parallel in the above spec
looks like the HV are quoted being connected in series though?

IIRC
2 x batteries in series give 2x voltage, but same current as one battery
2 x batteries in parallel give same voltage as 1x, but double the current as one battery
(for same voltage batteries)

Edit:
https://www.countybattery.co.uk/battery-experts/connecting-batteries-in-series-and-parallel/

I did wonder this but I have noticed similar things for all LV and all HV.

but then when looking at one battery. the HV has already a higher voltage to start with. This means the cells inside are also connected differently?

Anyway, this thread is about why to select a HV rather than LV (or vice versa). How do you decide which one you need?

My conclusion so far is that if you need higher dis/charge power and you know you need at least 2 batteries for increase capacity, then you need to go for HV batteries.

The, "they charge (and discharge) more quickly". Since they can charge or discharge at higher power, then for the same kWh of capacity then they will "fill" or get empty more quickly if you do not need that type of power.

As I have an electrical underfloor heating, I believe, so far, that it makes sense to have HV batteries. Experience will tell if then I have enough storage. If not I will need to buy more but then my 37 panels may not be enough to charge them....

 

[bladerunnerpv]

I have come across possibility of having two AC couple inverters in parallel, each with their own battery and the suggestion that the output power from battery storage could be increased like that.

Unfortunately, I can't remember where I saw it and I don't know how it works. Possibly SMA? Have seen that Givenergy AC couple inverters can be paralleled but don't know how in practice.

You could use 2 x 3kW output power AC inverters and get 6kW into the house?