Sunny Boy Grid Tied Inverter in Island Mode 60hz

[Hedges]

Thanks, so I guess more specifically one or more of the REC-BMS Q-BMS 16S, depending on how large a battery bank I want to build?

Man, this sure is starting to add up...

And that doesn't include external contactor or pre-charge accessory.

Of course, you can assemble 16s2p battery with two BMS, or 2p16s with one BMS.
Many people here have parallel/series battery packs. Series/parallel may be more ideal for protection. If one parallel connection went bad, the remaining cell would carry 2x current, but BMS would only know current of whole pack. If total pack current was 1/2 max allowed charge and discharge, maybe not a huge problem. BMS would observe that cell going over/under voltage and would tell SI to reduce current (balance during charge) or shut off (to avoid over-discharge.)

I think if you buy $8k or $14k worth of inverters you can afford $750 worth of BMS. Cost starts to bite if you need BMS for three separate battery strings on a 2x SI system.


I went with 20 kWh of SunXtender AGM (on 4x SI system) because it is occasional grid-backup. At the time (2 years ago) the alternative I was aware of was LG RESU, 5x the price for 5x the cycle life. That has since been subject to recalls due to fires. Today, DIY with 280 Ah cells and REC is around half the price, has similar usable capacity (compared to 70% DoD of my lead-acid.) BMS adding 25% on top of cost of cells.

It is similar with cost of PV. The panels have come down 10x over 20 years, but rack mounting has gone up, can dominate the cost. So yeah it's expensive, but is part of a well designed, well integrated system.

There are server rack batteries, I think almost twice the price for under half the capacity, but claimed twice the cycle life.
"Server Rack", meaning intended to provide 48VDC to computer servers. Some reportedly perform better than others with precharge inrush and high inverter loads. You end up needing multiple in parallel to handle the current. "Some" brands, in some installations the customer never gets it to work (shuts off.) Some customers have to replace with a different brand. Some open it up and replace with a better (but still inexpensive) BMS.

Other brands of inverters may have been configured for communications with some brands of server rack batteries. Many I think are used without communications. I don't have first-hand experience with either SI or other inverters on lithium.

 

[crazydane]

So it seems that the SI8.0 is being sold state side now at a very good price:


I haven't purchased from ecrunch.com but they seem legit...

 

[Consumerbot3418]

So it seems that the SI8.0 is being sold state side now at a very good price:

View attachment 116719
I haven't purchased from ecrunch.com but they seem legit...

It says it’s sold out, and 50Hz.

 

[RCinFLA]

Don't get involved with 230vac inverters with autotransformer for split phase 240/120vac. Stick with series connected 120vac version units for 240/120 split phase.

 

[Calvin98]

Great price, but very misleading ad. Big print says 240V to get your attention. Small print says 230V with some stuff tagged on to the end of the line. More info say its USED. 50hz not useful here. Maybe that is why they tacked on 70hz at the hz line. Thanks for letting us know though. Would have been nice.

 

[Hedges]

Data sheet says 40 to 70 Hz, should be able to set for 60 Hz. 172 to 260V, also adjustable.

https://files.sma.de/downloads/SI44M-80H-13-DS-en-30.pdf

The sale link was -11 revision. Some references to that being obsolete, -13 is latest. Don't know if hardware changed or just a firmware update.

It would be fine for 230/400Y, some industrial applications.
In the US for consumer we want 120/240 split-phase or 120/208Y.

Transformers for the full wattage get expensive. Step-down is more readily available used, so off-grid could be done. Step-up I'm finding not all transformers like to be driven backwards. A 240/480 to 120/240 transformer could be fed 240V from our split phase and output 240V L/N for a grid input. But you don't want to use transformers on both sides of the inverter, when you can buy stackable 120V models here.

 

[Calvin98]

Good to know that is really adjustable that far - up to 70 hz. Yes, the 120/240 is still the question.

 

[Hedges]

The specs I quoted were for external grid/generator. Output is a bit tighter.

"AC-1 (Stand-alone mode, battery-backup, load)
Rated grid voltage / AC voltage range 230 V / 202 V to 253 V
Rated frequency / frequency range (adjustable) 50 Hz / 45 Hz to 65 Hz"

Like the US models, can be connected for 3-phase or in parallel. Haven't found how many in parallel, whether it can go to four or just three. No mention of split-phase.

120/240 is going to require transformer. 240V is available native, but will be line to neutral.

After I purchase an isolation transformer (for another application) I'll test how it behaves, how much loss and reactive power, for step-up and step-down autotransformer use. I have a toroid that looks like it it pretty low loss, but typical "E" core power transformers may be different. I think the trick is going to be using 240V windings at 120V, not operating as close to limits.

 

[crazydane]

Yeah I saw the frequency input and output would be compatible with the 60Hz, but didn't catch that the 8H series will not accept 120 VAC. Would definitely want series connected 120 VAC versions. Figured it was too good to be true...

 

[billt1827]

The sale link was -11 revision. Some references to that being obsolete, -13 is latest. Don't know if hardware changed or just a firmware update.

It is indeed obsolete and will be several years old. I have a 8.0H-11 (bought in 2014) and it won't work as a cluster with a -12 or a -13 unfortunately, so I'm having to dump my -11 and buy 2 -13s, which are the current iteration.

Going by european prices, if it were new you would expect to pay $3,500 +.