Batteries 50V vs 100V

[Bob Smith]

Hi all

until now I believed that the batteries for a PV installation for residential all were between 48 and 52V as nominal voltage
I finally received a quote today and the battery was a Solax Triple Power (see attached pdf)

The nominal voltage is 115V

As the discharge power seems to remain in the same range than the other batteries, this means that the current will be lower.

I am trying to figure out what are the advantages of such batteries vs what we seem to find more commonly the 50V batteries.

Thanks a lot and maybe this post will also help other newbies like me.

PS One big difference I notice is the mass. A 5.8kWh has a mass of 72kg while usually the pylontech, Growatt etc are in the region of 40 to 50 for the same storage capacity. And of course the price. That high voltage seems to be about 50% more expensive...

 

[Bob Smith]

To contribute to my own discussion


WHAT IS HIGH VOLTAGE BATTERY SYSTEM?

The high voltage battery systems are usually rated at more than 100V. These powerful batteries can charge and discharge faster than low-voltage ones, making them ideal for covering those quick demand surges from starting equipment that might not be able to stay running without power immediately. The increased volts also mean smaller conductors.

High-voltage battery systems are a more recent development in the world of home solar battery backup. These higher voltage models can provide increased energy output to support heavier loads, making them perfect for homes with electricity consumption rates that exceed what is typically seen at lower voltages

Commissioning a home battery backup with an high-voltage battery not only increases efficiency but also saves energy. The DC bus voltage normally varies between 300 volts and 500 V, so when you choose this option your inverter has less work to do. When you choose a low-voltage home battery backup, the inverter needs to work harder and reduce an input voltage of 300 -500V below 100 V. This results in less energy efficiency for your home or business’s power requirements.

High voltage battery systems are perfect for properties with commercial energy storage demands and home battery backup use. They offer a number of advantages over other types of batteries, including longer life and higher discharge rate. In addition, high voltage battery systems are less likely to overheat, making them safer to use. With their many benefits, it’s no wonder that high voltage home battery backup are becoming increasingly popular.

THE HIGH VOLTAGE HOME BATTERY BACKUP ARE MORE EXPENSIVE TO INSTALL?

Generally speaking, the price of high-voltage batteries in the market is higher than that of low-voltage batteries. The main reason for this is the high manufacturing cost of high-voltage batteries and the brand premium. However, there are a number of factors that can affect the price of lithium batteries, including the type of battery, the size of the battery, and the quality of the battery. In addition, lithium battery prices can also vary depending on the supplier. As a result, it is important for buyers to compare prices from different suppliers before making a purchase.

Source: https://www.bonnenbatteries.com/hig...hats-the-best-choice-for-home-energy-storage/


Another interesting post

https://www.deegesolar.co.uk/high_voltage_or_low_voltage_solar_batteries/

HIGH VOLTAGE BATTERIES​

High voltage batteries are a recent phenomena within the solar industry. Compared to LV batteries, high voltage solar batteries offer a higher discharge rate to support higher load demands. High voltage battery systems are usually rated around 400V. These systems can charge and discharge faster than the low voltage batteries and can cover those quick demand surges from starting equipment. If we take this back to the water tank analogy a High voltage battery is a high “pressure” battery. Which means as the pressure in the battery is high, as soon as the battery is switched on there is a burst of initial energy, resulting in a quicker discharge of energy or water from the hose. Because the voltage is so high in a HV battery, they do not require larger conductors.
In a high voltage battery system, the inverters tend to allow for less battery connections (around 3 batteries), however the individual batteries themselves are much larger in capacity. What’s more, when commissioning a home solar PV system with a high-voltage battery you can increase the efficiency of the entire system. This is because the DC bus voltage is normally around 300-500V and the current running to the inverter from the battery is significantly lower. In contrast, when you choose a low-voltage battery, the inverter needs to work harder to reduce the input voltage of 300-500V to below 100V. This results in a loss of energy, and a less efficient system.
High voltage batteries are perfect for households or commercial properties with exceptionally larger energy demands. So if you are looking for faster charging and discharging, a HV battery is the right choice for you.

EXAMPLES OF HIGH VOLTAGE BATTERY SYSTEMS​

Here are a few examples of the HV battery systems we install here at Deege Solar.

• The 5.8kWh High Voltage Solax Triple Battery with the 5kW Solax Inverter.
• 2 x 2.6kWh Fox Ess Batteries with a 5kW Hybrid Fox Ess Inverter.
• 5.12kWh Sofar Amass EP HV Battery with a 6kW Sofar Solar Hybrid Inverter.

• HV Batteries have Higher Charge and Discharge Rate.

More Efficient System.

• More Expensive to install.

 

[MHarv]

I have Solar PV array on Solax X1 Boost 3.6kW G98 type tested compliant inverter to 5.2kW array split east west.

also have installed Solax X1 AC-3.6 inverter coupled to Solax Main Master Battery LFP 5.8kW and Solax Slave Battery
5.8kW combined total of 11.6kW, each battery at 115 volts, with two batteries, starting voltage of 230 volts, which gives
lower Amps for Charging and Discharging, charging batteries on Octopus Go cheap rate early morning 0030-0430 hrs
ampage starts at 9A @ 244v with increasing voltage, finally finishing off at 14.9A @ 247 utilising smaller DC cables between
Battery and inverter, 6mm2.

Main Master Battery has inbuilt DC 40A breaker, for battery system, charging from 41% takes about two hours depending on
ambient temperature where the batteries are located, so far battery temperature not gone below 14'C, situated in attached double garage
which I find is cold.

Best buy price was from ITS, great service, in no way am I affiliated to them, just good price and service after doing some research
as you have done Bob Smith and found another battery system with over 100volts, different attributes to compare with a 48v-52v system.
I did compare Pylontech and Growatt, from my installer...but went with Solax HV Battery and AC System in the end....

Discharge and Charge covers a range, boiling a kettle 3kW for a cuppa, will discharge over 3000w max is 3680w Solax X1 AC-3.6kW (G98 &G99 Compliant Type Tested ENA Reference Number for G99 Fast Track Application... also G100 ELS Compliant which is required as I already have G98 PV system installed before the battery installation... to reduce Export to 16A 3680 kW for the Battery System to be Approved by the DNO before making the battery purchase.

Integration with PV is working, solar charges the battery, also with iBoost +, Threshold setting increased from Default 100w to 200w
Using Work Mode, in Summer set 'Self Use' to Winter in 'Force Time Use', for this to work enter timings, enter 2 sets of periods with Octopus Go TOU timmings and all set, batteries charge then starts automatically to discharge to house load if any or into standby mode until requested for power.

High Voltage Battery System should be taken into consideration if looking at Battery Systems for the home, Pylontyech now have
brought out their own HV Battery System which will work with Solax AC inverters, check out ITS website.

 

[bladerunnerpv]

This was a topic I was on my way to digging into but not had time yet.

I had thought the limitation of HV batteries were that they were AC coupled only

however, I then saw SolaX X1 G4 Hybrid 7.5D, so hybrid inverters with HV would appear to be possible, single phase.

What stuck in my brain from last time I looked at these as AC coupled items was that only one or two batteries could be linked to the inverter, making the achievable kWh storage quite limited.

Also there seem to be several types / sizes of HV batteries from a single manufacturer - Solax have TP3.0 and TP5.8, there's also the BYD HVM and HVS systems. Needs some time to unpick the differences and understand why.

Skimming the TP5.8 spec, it's LiFePO4 as usual. 90% DoD is >6000 cycles, which is uninspiring and base warranty 10yrs, and IP55 environment protection.
1 Master with 0 to 2 slaves, so 5.8 - 17.4kWh possible, so either I misunderstood (always possible) or things may have moved on. Inverter + 1master, 2 slaves for £8660 excl VAT, wholesale price.

Givenergy 9.5kWh battery (~50V) warranty is unlimited cycles/10yrs, IP65

BYD HVS: warranty is ?? cycles/10yrs, IP55
"One Battery-Box Premium HVS is composed of 2 to 5 HVS battery modules that are serially connected to achieve a usable capacity of 5.1 to 12.8 kWh. Additionally, direct parallel connection of up to 3 identical Battery-Box Premium HVS allows a maximum capacity of 38.4 kWh. Ability to scale by adding HVS modules or parallel HVS stacks at anytime"

HVS 10.2 is 4 modules 167kg in one vertical stack. on a 600 x 300m base - gonna need a decent floor there methinks
25A max output current

BYD HVM: warranty is ?? cycles/10yrs, IP55
"One Battery-Box Premium HVM is composed of 3 to 8 HVM battery modules that are serially connected to achieve a usable capacity of 8.1 to 22.1 kWh. Additionally, direct parallel connection of up to 3 identical Battery-Box Premium HVM allows a maximum capacity of 66.2 kWh. Ability to scale by adding HVM modules or parallel HVM stacks at anytime"

HVM 11.0 is also 4 modules 167kg in one vertical stack. on a 600 x 300m base - gonna need a decent floor there methinks
50A max output current

both HVS and HVM with RTE >96%

"anytime" - hmmm, well as long as they're still making that version and haven't upgraded / changed design, come back in 5yrs and I doubt you'll have a chance!

watching with interest...

 

[binky]

Higher voltage means lower ampage which in turn means you can use smaller cables. Higher voltage is also more dangerous to work with, although I'm not sure how nasty 100v DC is. Other than that I don't like the price

 

[Bob Smith]

Higher voltage means lower ampage which in turn means you can use smaller cables. Higher voltage is also more dangerous to work with, although I'm not sure how nasty 100v DC is. Other than that I don't like the price

So you don't know any other benefits ?

1. They mention they are quicker to charge: Could this be an advantage when there is a half cloudy sky and windy day when the panels are well exposed to the sun for 10min then, it is cloudy for 10 etc..?
2. They mention they release power more quickly: Is that any advantage in a typical house (TV, toaster, kettle, tumbler dryer, washing machines, oven.., maybe when an EV needs charging?)

For @bladerunnerpv I must have AC coupled because I already have an existing system with FiT.

 

[johnb2713]

1. They mention they are quicker to charge: Could this be an advantage when there is a half cloudy sky and windy day when the panels are well exposed to the sun for 10min then, it is cloudy for 10 etc..?

Inside the pack it will be double the number of LifeP04 cells to a traditional 50v pack. I dont see how it can be quicker to charge, the LifeP04 cells have a charging algorithm to follow and each of the 3.2v cells will follow it. As long as the charger has the capacity to feed the power required and the inverter the capacity for discharge, I would have thought there was no difference in either.

Interested to hear how they go.

 

[binky]

So you don't know any other benefits

Nope, but I'm no expert on batteries

1. They mention they are quicker to charge: Could this be an advantage when there is a half cloudy sky and windy day when the panels are well exposed to the sun for 10min then, it is cloudy for 10 etc..?
2. They mention they release power more quickly: Is that any advantage in a typical house (TV, toaster, kettle, tumbler dryer, washing machines, oven.., maybe when an EV needs charging?)

For @bladerunnerpv I must have AC coupled because I already have an existing system with FiT.

How much quicker is the question? Milliseconds, seconds? Is that based on using the larger cables of a lower voltage battery??? My background is engineering, so I have a dislike of unjustified statements. I don't really get the voltage conversion argument either, if you have to step voltages up and down, does it really make any difference if its less volts, you still need a transformer with it's inefficiencies. So I would suggest doing some more research and coming back with any answers you find. But, biggest but... not Kim Kardashian , if the efficiency is say 1% better than a lower voltage battery then does it justify the extra cost??? I never used to fit the most efficient solar panels coz they were twice the price of mid range gear but not twice as efficient. Some customers insisted on buying them, but they never got twice the output, in fact nothing like twice the output. I used to contact customers annually to get feedback on the solar systems I've fitted, it helped refine my design skills.

 

[Bob Smith]

Yep, I am spending my evening scrolling the internet finding facts-based arguments.
Like you, I don't like relative answers. Quicker, bigger, more expensive etc... Does not mean anything and you can't make a decision based on that.
Often, when you ask back. How much quicker, the person then gets defensive and you go nowhere. pathetic, Anyway another discussion.

I will definitely keep posting everything I find outside of this forum.
I need to learn more about this new design that got proposed not only it has new HV batteries but also micro inverters instead of a string inverter.

I have already spent more than 3 hours tonight and I feel I know less than when I started!!!
Sometimes I feel my life would be easier if there was no choice and if I did not feel the need to want to understand what I am getting

 

[bladerunnerpv]

For the solax X1 Hybrid G4 the spec says
for "Output DC (Battery)"
[I think this means the inverter output to the battery?]
Battery voltage range 80-480V
Max continuous charge/discharge current 30A

If I understand correctly then for nominal 100V battery then this is 3kW charge/discharge [edit: 100V x 30A = 3000W]

for off-grid output (with Battery)
Max continuous current varies from model to model as 13 to 32.6A
- according to the inverter model's max continuous apparent power of 3kW to 7.5kw

for comparison Givenergy Hy5
Battery nominal voltage 48V
Charge/Discharge current 65A / 81A
Max charge / discharge power 3600W / 3600W
48V x 65A = 3.12kW charge power

so vs a 100V battery the Giv has the edge on battery charging?

solax TP 5.8 is nominal 115.2V, so 115.2V x 30A = 3.456 kW [Edit: OK so maybe the solax has it, but they're quite close]

so if I've got my head around it right there's not much difference in charge rate for these two examples?

Did I miss something?

 

[binky]

Yep, I am spending my evening scrolling the internet finding facts-based arguments.
Like you, I don't like relative answers. Quicker, bigger, more expensive etc... Does not mean anything and you can't make a decision based on that.
Often, when you ask back. How much quicker, the person then gets defensive and you go nowhere. pathetic, Anyway another discussion.

I will definitely keep posting everything I find outside of this forum.
I need to learn more about this new design that got proposed not only it has new HV batteries but also micro inverters instead of a string inverter.

I have already spent more than 3 hours tonight and I feel I know less than when I started!!!
Sometimes I feel my life would be easier if there was no choice and if I did not feel the need to want to understand what I am getting

I'm not a fan of micro-inverters unless you have shading issues. Fact is they have 2 problems, one, you are adding twice the number of connections on the roof which are the most common failure point, and two, they will need replacing in 20 years, which means scaffolding and lifting all the panels, which will probably mean replacing all the panel clips if you can still get them, and if you can't, replacing the entire framework. I've found that panel clips are pretty impossible to reuse after less than 10 years, they consist of stainless steel and aluminium, which corrode together by electrolytic corrosion ie dissimilar metals and water make a weak battery.

 

[Bob Smith]

I'm not a fan of micro-inverters unless you have shading issues. Fact is they have 2 problems, one, you are adding twice the number of connections on the roof which are the most common failure point, and two, they will need replacing in 20 years, which means scaffolding and lifting all the panels, which will probably mean replacing all the panel clips if you can still get them, and if you can't, replacing the entire framework. I've found that panel clips are pretty impossible to reuse after less than 10 years, they consist of stainless steel and aluminium, which corrode together by electrolytic corrosion ie dissimilar metals and water make a weak battery.

You may not remember (and you'll be forgiven for that ) a few months back I posted photos of where I will be installing the panels.
There will be a wall facing west

1. A low roof (not flat roof) facing South East
2. The other side of the low roof facing North West
3. The main roof facing North West

(the main roof facing South East has panels since 2016)

As you can see apart from the main roof, the 3 other areas experience some shading throughout the day.

Anyway this thread is about the pros and cons of LV and HV batteries.

 

[Bob Smith]

For the solax X1 Hybrid G4 the spec says
for "Output DC (Battery)"
[I think this means the inverter output to the battery?]
Battery voltage range 80-480V
Max continuous charge/discharge current 30A

If I understand correctly then for nominal 100V battery then this is 3kW charge/discharge

for off-grid output (with Battery)
Max continuous current varies from model to model as 13 to 32.6A
- according to the inverter models model's max continuous apparent power of 3kW to 7.5kw

for comparison Givenergy Hy5
Battery nominal voltage 48V
Charge/Discharge current 65A / 81A
Max charge / discharge power 3600W / 3600W
48V x 65A = 3.12kW charge power

so vs a 100V battery the Giv has the edge on battery charging?

solax TP 5.8 is nominal 115.2V, so 115.2V x 30A = 3.456 kW

so if I've got my head around it right there's not much difference in charge rate for these two examples?

Did I miss something?

Sorry, I do not know enough to answer your question

 

[binky]

You may not remember (and you'll be forgiven for that ) a few months back I posted photos of where I will be installing the panels.
There will be a wall facing west

1. A low roof (not flat roof) facing South East
2. The other side of the low roof facing North West
3. The main roof facing North West

(the main roof facing South East has panels since 2016)

As you can see apart from the main roof, the 3 other areas experience some shading throughout the day.

Anyway this thread is about the pros and cons of LV and HV batteries.


View attachment 14517


View attachment 14516

View attachment 14518

View attachment 14519

Chop the tree down

Fair enough, micro-inverters are going to work better for you with that level of shade

 

[bladerunnerpv]

Sorry, I do not know enough to answer your question

Me neither! Just trying to rough out some sums in case s/o else does A little knowledge is a dangerous thing as they say....

 

[Bob Smith]

Chop the tree down

Fair enough, micro-inverters are going to work better for you with that level of shade

You mean better than optimizer like Tigo or better than just standard panels?

 

[binky]

You mean better than optimizer like Tigo or better than just standard panels?

I mean better than a standard inverter.

I'm not such a fan of tigo as it's still based on strings, I prefer proper micro-inverters so that each panel is completely independent of the next. Or you could go down the solaredge route, which again optimises each panel.

 

[Bob Smith]

That's correct.

There is also another parameter to take into account with the string inverter. We need a minimum Voltage on the string to kick it off.
When you see the layout I have (see pictures above). it is likely that I will have the panels from the Wall and the 2 small roof on the same string.
This string will "suffer" as the panels will always experience different exposures to the sun. Optimizer or micro inverter are therefore a must.

I believe the micro inverter will be more efficient as this makes each panel properly independent as you said.

Unfortuntely, I am also planning to have panels on the main roof which does not have any shading (apart of the clouds of course). Therefore, I do not need optimizers or micro-inverters there. (I do not have optimizer or micro inverter for my 16 panels on the main roof facing south east and I am happy with the generation.)

Ideally, I would have the main roof panels with no optimizer or micro inverter and for the rest (wall, small roof both side) micro inverters.
That's the conundrum.
If I were to have micro inverter for those panels only, I will need the main roof panels connected to a string inverter.

I need to calculate the cost difference and pros and cons.

Option 1:
String inverter. (2 MMPT). String 1 for the panels on the walls and the small roof with Tigo. String 2 for the panels on the main roof and no Tigo

Option 2:
Only micro inverters everywhere

Option 3:
String inverter for the panels on the main roof, and micro inverter for the rest.

I feel option 3 will be the most efficient in terms of generation and maintenance/repair (small roof and walls are easy to access) but will also be the most expensive....

However, I have not yet considered how to connect batteries in case of option 3 and I fear this will increase the cost.

	Inverter	Main Roof Panels	Wall + small roof panels	Pros	Cons
Option 1	6kW	No optimizer String 1	Tigo Optimizer String 2	Less points of failure on the main roof	Tigo not as efficient as micro inverter (still need min voltage for the string inverter)
Option 2	None	Micro Inverter	Micro Inverter		More points failure on the main roof
Option 3	Yes (for main roof panels only). What size?	No optimizer	Micro Inverter	Less equipment on the main roof. Where there is lot of shade panels entirely independent	Cost? Connection to the batteries more complex?

 

[MHarv]

For the solax X1 Hybrid G4 the spec says
for "Output DC (Battery)"
[I think this means the inverter output to the battery?]
Battery voltage range 80-480V
Max continuous charge/discharge current 30A

If I understand correctly then for nominal 100V battery then this is 3kW charge/discharge [edit: 100V x 30A = 3000W]

for off-grid output (with Battery)
Max continuous current varies from model to model as 13 to 32.6A
- according to the inverter model's max continuous apparent power of 3kW to 7.5kw

for comparison Givenergy Hy5
Battery nominal voltage 48V
Charge/Discharge current 65A / 81A
Max charge / discharge power 3600W / 3600W
48V x 65A = 3.12kW charge power

so vs a 100V battery the Giv has the edge on battery charging?

solax TP 5.8 is nominal 115.2V, so 115.2V x 30A = 3.456 kW [Edit: OK so maybe the solax has it, but they're quite close]

so if I've got my head around it right there's not much difference in charge rate for these two examples?

Did I miss something?

Solax Single Master battery 115-130v floating; Mine Master plus Slave at floating 230v-250v; 245 x 14.9= 3650w G98 & G99 Fast Track Max, ENA Register Type Tested with G100 Declaration for ELS. Larger Inverter capacity is Full G99 if you go down this route. All Stats and Data can seen on iphone App including changing parameters without going to the inverter where it is located, which can also change the Work Mode, SOC % and timings within 1 min increments (.... 16A only charges at 14.8A this all depends on ambient temp plus battery temp, colder the battery lower Amps startup Amps 9Amps (for last weeks temps outside, this week startup charge 8A battery 14'C my battery is in a garage not heated, if located inside ambient temps are higher, so therefore the battery temp will be higher to start a charge, constantly 9a for 20 mins at 16-17'C then ramping up to through 10-13, and finally 14.9A at 3680w.

You can lower the Max Amps from 35A to lower numbers or higher for Minimum SOC 10% (Both Default settings)

 

[binky]

That's correct.

There is also another parameter to take into account with the string inverter. We need a minimum Voltage on the string to kick it off.
When you see the layout I have (see pictures above). it is likely that I will have the panels from the Wall and the 2 small roof on the same string.
This string will "suffer" as the panels will always experience different exposures to the sun. Optimizer or micro inverter are therefore a must.

I believe the micro inverter will be more efficient as this makes each panel properly independent as you said.

Unfortuntely, I am also planning to have panels on the main roof which does not have any shading (apart of the clouds of course). Therefore, I do not need optimizers or micro-inverters there. (I do not have optimizer or micro inverter for my 16 panels on the main roof facing south east and I am happy with the generation.)

Ideally, I would have the main roof panels with no optimizer or micro inverter and for the rest (wall, small roof both side) micro inverters.
That's the conundrum.
If I were to have micro inverter for those panels only, I will need the main roof panels connected to a string inverter.

I need to calculate the cost difference and pros and cons.

Option 1:
String inverter. (2 MMPT). String 1 for the panels on the walls and the small roof with Tigo. String 2 for the panels on the main roof and no Tigo

Option 2:
Only micro inverters everywhere

Option 3:
String inverter for the panels on the main roof, and micro inverter for the rest.

I feel option 3 will be the most efficient in terms of generation and maintenance/repair (small roof and walls are easy to access) but will also be the most expensive....

However, I have not yet considered how to connect batteries in case of option 3 and I fear this will increase the cost.

	Inverter	Main Roof Panels	Wall + small roof panels	Pros	Cons
Option 1	6kW	No optimizer String 1	Tigo Optimizer String 2	Less points of failure on the main roof	Tigo not as efficient as micro inverter (still need min voltage for the string inverter)
Option 2	None	Micro Inverter	Micro Inverter		More points failure on the main roof
Option 3	Yes (for main roof panels only). What size?	No optimizer	Micro Inverter	Less equipment on the main roof. Where there is lot of shade panels entirely independent	Cost? Connection to the batteries more complex?

I would go for option 3 to keep unnecessary costs down. It would think it's cheaper than the other 2 options as string inverters are quite low cost.