[RE-wrenches] Bootstrapping and AC Coupled Sunny Island

[jay]

A possible fix.

You could run a DC relay on the SB PV input that would be voltage triggered to prevent the battery volts from getting higher than you want.

The SI has 2 aux relays I think?  Or could do a tristar with RD-1 relay that has 4 channels.

Just a thought

jay

> On May 7, 2024, at 11:11 PM, William Miller via RE-wrenches <re-wrenches at lists.re-wrenches.org> wrote:
> 
> Friends:
>  
> I am still wrestling with problems integrating a Sunny Island / Sunny Boy AC coupled system to a set of 5 E-vault Max battery cabinets.  
>  
> As a refresher, with closed loop comms, the Frequency Shift Power Control system is not working, or not working quickly enough, and when nearing full charge, the voltage can spike up to 66 volts and the SI system shuts down.  Fortress has told me in a roundabout way that they agree this is a real problem and they are working on a solution.
>  
> Another problem has reared its head:  If the E-Vaults do not get charged fully every 5 to 7 days, the BMS units SOC value becomes radically out of calibration.  The E-vault will report a higher SOC than is realistic.  The SI system starts the generator based on SOC and if the SOC is reported as high the generator don’t start.  Sooner rather than later the battery voltage gets too low and the system shuts down.
>  
> I have been tweaking on the settings like days-since-full-charge to attempt to get this cycle to stop.  No definitive answer yet.
>  
> Here is the reason I am writing:  Yesterday I could not get the Sunny Islands to start.  The battery voltage was 46 which should have been enough but for some reason they just would not start.  Because of this I could not charge the batteries from generator or from AC coupled solar.  I called SMA but they told me they could not advise because of the non-compatible batteries.  I asked about the emergency charging procedure in the manual but I was told this does not work with lithium batteries.  The process is pretty scary anyway so I was not inclined to try.
>  
> SMA told me I may need an external 48 volt charging system.  I have heard of this being required in certain scenarios by wrenches.  This would be a huge pain in the ass: ordering one, waiting for it, hooking it up, etc.
>  
> Here is what I did:  I initiated the Quick Start Configuration mode and told the SI system there was a new battery bank.  I told it the bank was a very small VRLA battery.   The SI system accepted the 46 volts, started up and allowed a generator charge.  After an hour or so we reprogrammed the system for lithium and problem resolved, at least for now.
>  
> Hopefully this trick may help one of you some day.  If it does, it was worth my time typing it out.
>  
> William
>  
> Miller Solar
> 17395 Oak Road, Atascadero, CA 93422
> 805-438-5600
> www.millersolar.com <http://www.millersolar.com/>
> CA Lic. 773985
>  
>  
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