Batteries 50V vs 100V

[MHarv]

Solax do Parallel Box (Wondered what this is for?) for this, contact Solax UK for more info, if you are considering Solax, there are some video's on UTube.

https://shop.krannich-solar.com/de-...lutions/accessories/14855/bms-parallel-box-ii
https://www.solaxpower.it/wp-content/uploads/2022/06/BMS-Parallel-Box-II.pdf
Two Solax 3.6 AC inverters= the T58 Battery Specs for 2 batteries 11.6kW at 230v with 7kW output!
More info for you Bob

 

[arwooldridge]

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.

Good idea about the heated box! All EV's allow charging at sub zero temperatures but just limit the charge power. This is why the Solax charge is severely restricted at low temperatures. I can't believe though at the designed charge level it would damage the batteries. It's definitely something to take into account though if you can place batteries in a warmer place, or heat. Maybe use the excess PV power you cannot charge to run a heater instead of exporting it in cold weather.

 

[arwooldridge]

Solax do Parallel Box (Wondered what this is for?) for this, contact Solax UK for more info, if you are considering Solax, there are some video's on UTube.

https://shop.krannich-solar.com/de-...lutions/accessories/14855/bms-parallel-box-ii
https://www.solaxpower.it/wp-content/uploads/2022/06/BMS-Parallel-Box-II.pdf
Two Solax 3.6 AC inverters= the T58 Battery Specs for 2 batteries 11.6kW at 230v with 7kW output!
More info for you Bob

Yes the BMS parrallel box is the best way to go. I have one but am waiting for delivery of more slave batteries to do it justice. You can parralel two strings of up to four batteries giving 46kwhr total. Even if you don't need it initially it gives a better way to expand in future.

 

[Bob Smith]

Hello @arwooldridge

Thank you for joining the conversation. I understand you are the proud owner of a Solax Parallel Box.

I read the datasheets and manual from the Solax website and unfortunately, I could not find a list of support batteries.
I understand though that there is no need for a master battery. Is that true? If so, then there is a bit of savings to be had maybe
Does it support only HV batteries or can we use it with LV batteries?

We have been discussing the pro and cons of HV vs LV and find it difficult to name a clear winner as it depends on different situations.
The first one being, if you only need one battery then there isn't really any difference apart of the price.

If I may, would you mind sharing your experience with your system, why you opted for this configuration and what would you do differently knowing what you now know?

Thank you in anticipation for your time.


https://www.solaxpower.com/downloads/

 

[arwooldridge]

Hello @arwooldridge

Thank you for joining the conversation. I understand you are the proud owner of a Solax Parallel Box.

I read the datasheets and manual from the Solax website and unfortunately, I could not find a list of support batteries.
I understand though that there is no need for a master battery. Is that true? If so, then there is a bit of savings to be had maybe
Does it support only HV batteries or can we use it with LV batteries?

We Hello @arwooldridge

Thank you for joining the conversation. I understand you are the proud owner of a Solax Parallel Box.

I read the datasheets and manual from the Solax website and unfortunately, I could not find a list of support batteries.
I understand though that there is no need for a master battery. Is that true? If so, then there is a bit of savings to be had maybe
Does it support only HV batteries or can we use it with LV batteries?

We have been discussing the pro and cons of HV vs LV and find it difficult to name a clear winner as it depends on different situations.
The first one being, if you only need one battery then there isn't really any difference apart of the price.

If I may, would you mind sharing your experience with your system, why you opted for this configuration and what would you do differently knowing what you now know?

Thank you in anticipation for your time.

Yes the BMS parrallel box is solely for the Solax HV batteries, and yes the integral BMS management in the parrallel box does away with the need for the master triple power 5.8 battery. This unfortunately become redundant if you upgrade from 4 batteries to up to eight batteries when using the BMS parrallel box, so for new installs I would recommend the parrallel box even if you don't need the full capacity initially, as it allows for upgrade later.

 

[Bob Smith]

Yes the BMS parrallel box is solely for the Solax HV batteries, and yes the integral BMS management in the parrallel box does away with the need for the master triple power 5.8 battery. This unfortunately become redundant if you upgrade from 4 batteries to up to eight batteries when using the BMS parrallel box, so for new installs I would recommend the parrallel box even if you don't need the full capacity initially, as it allows for upgrade later.

As I understand the Triple Box. without the parallel box, you currently need the Master and you can add up to 3 slaves.
With the parallel box you do not need master anymore and you can have up to 2 x 4 batteries (2 strings)

Without Parallel box . max is 5.8kWh (from Master) + 3 * 5.7kWh Slave = 23kWh
With the parallel box max is 4 x 5.7kWh per string = 22.8*2= 45.6kWh

It sounds good, however other systems (but with LV) can go much higher in kWh even for residential.

 

[arwooldridge]

As I understand the Triple Box. without the parallel box, you currently need the Master and you can add up to 3 slaves.
With the parallel box you do not need master anymore and you can have up to 2 x 4 batteries (2 strings)

Without Parallel box . max is 5.8kWh (from Master) + 3 * 5.7kWh Slave = 23kWh
With the parallel box max is 4 x 5.7kWh per string = 22.8*2= 45.6kWh

It sounds good, however other systems (but with LV) can go much higher in kWh even for residential.

Yes that's right it's 46 kwhr max, to get more you would need to parrallel inverters each with their own batteries. It seems to be a limitation of Solax HV batteries (maybe others?) that you cannot simply do series/parrallel arrangements. To do so would involve hugh charge/discharge currents on connection unless all batteries where exactly the same voltage charge state. Anyway the inverter BMS system is not designed for parralleling HV batteries with the exception of the BMS parallel box which I imagine works by charging the lower voltage string seperately until voltages are equal.

 

[Bob Smith]

and what made you go for HV batteries instead of LV?

 

[arwooldridge]

As a Tesla owner for 8 years I think it's the right topology. High voltage equals lower current. 10kw charge/discharge at 50 volts would be 200 amps. Maybe one day a scrapped Tesla battery 100kwhr pack can be converted to run on HV inverters. High voltage transistors are reliable now.

 

[bladerunnerpv]

I case it helps a general summary of battery storage can be found on ITS technologies website

https://www.itstechnologies.shop/pages/understanding-economy-7-and-maximising-octopus-goand linked pdf
https://cdn.shopify.com/s/files/1/0257/3103/9284/files/Battery_Storage_Guide.pdf?v=1666854779
dated Aug 2021

Above seems to indicate battery compatibility is mostly only with own make, ITS may be playing it safe in terms of what they supply?

Have a close look at your inverter spec / associated documentation though as some are compatible with a wider range of batteries, I seem to have noted in my mind it's the LV ones which are more mix and match. Solis battery compatibility datasheet gives a list of about a dozen battery manufacturers! Not researched the HV type inverters specifically yet...