diy solar

diy solar

EG4-48VDC in Series

Why you need the high voltage system? The high voltage battery must match with high voltage inverter, you can check the Sofar, Growatt, Luxpower and some other inverter brand which have the small power but high voltage version for home energy storage system. At this situation, the battery pack also should be high voltage system, there isn't the BMS supplier willing to provide this to the individul clients.
So DIY is not the solution to decrease the cost.
I have a Growatt MIN11400TL-XH-US installed with 12 kW of panels. I would like to use the 5kW off grid output in the very rare occasions when we have a power outage. The Growatt HV battery is a significant upfront investment if all you will use it is a couple of times a year. And I would hate to make a large upfront investment (>$7k for 9.9 kWh) like that and discover the HV battery does not perform as advertised- I expect it’s unlikely a person would have a quick or easy time getting the seller and manufacture to deal with an issue- so I would prefer an incremental solution if possible.
 
Thanks, and the EG4 manuals clearly indicate you can only series the smaller voltage models up to 48 vdc and not the 48 volt model. Does anyone know of a brand that can go to 72 or perhaps 96 volts?

There are BMS which can do that. REC has modules which can be cascaded to several hundred volts.

The limitation is the series device that interrupts the circuit. If you were to bypass BMS on several batteries, connect cells of multiple batteries in series, and use a higher voltage relay to disconnect when any BMS signals disconnect, that might work. But, isolation of BMS control and communication circuitry could be a problem. Some BMS internals could then be hundreds of volts from chassis and data connectors. May or may not have the isolation required for functionality and safety.

Possibly a diode-bypass arrangement could also do the trick. Just like for PV panels/strings, if one panel is shaded, bypass diodes allow rest of string to push current past so that panel doesn't have their voltage applied across it.

(Any scheme to use batteries in a string above rated voltage belongs in Danger Zone!)
 
any thought on connecting high voltage battery to the PV-DC input ?
 
It should work fine.
As long as the voltage is in the correct range.
And the battery has low voltage cutoff protection.
 
Use a precharge resistor.
PV input expects to be fed with approximately current source from PV; its capacitors would initially look like a short to battery.
Properly sized NTC thermistor is another option. They are used for SMPS capacitors fed from AC.

It was done with Prius batteries into Sunny Boy, and someone more recently used an EV battery and PV input of an AOI.

I would like to feed generator input into PV input of Sunny Boy, so generator isn't AC voltage and frequency source when off-grid; Sunny Island would continue to do that. Lithium battery is another idea, with gentle current draw on it while recharging Sunny Island's AGM to float so only used for surge. Because lithium would be fed to GT inverter, I could interrupt AC rather than DC to prevent over-discharge.
 
It should work fine.
As long as the voltage is in the correct range.
And the battery has low voltage cutoff protection.
I was concerned about the different impedance. PVs are basically a current source, and current limited by default depending on insolation, but a battery can provide a lot of instant current
 
Use a precharge resistor.
PV input expects to be fed with approximately current source from PV; its capacitors would initially look like a short to battery.
Properly sized NTC thermistor is another option. They are used for SMPS capacitors fed from AC.

It was done with Prius batteries into Sunny Boy, and someone more recently used an EV battery and PV input of an AOI.
what's AOI and SMPS ? please share a link to the EV battery to PV-input if you have it. That's exactly what I'm thinking of doing. Thanks
 
All In One
Switch-Mode Power Supply. Inrush when plugging in a large supply could trip breakers, is also stressing for caps. VFD variable frequency drive is an SMPS with AC output.

Here's one V2H implementation:


More on the topic:


I've seen other links and articles, but the forum and web are so big, can't locate the needle in haystack.
Somebody here showed an AOI connected to HV battery in car.
 
All In One
Switch-Mode Power Supply. Inrush when plugging in a large supply could trip breakers, is also stressing for caps. VFD variable frequency drive is an SMPS with AC output.

Here's one V2H implementation:


More on the topic:


I've seen other links and articles, but the forum and web are so big, can't locate the needle in haystack.
Somebody here showed an AOI connected to HV battery in car.
Same here. I know that I have seen it, but don't remember where.
 
Sigineer carries two dc to ac 96v inverter chargers rated at 15000 watts.

The 15KVA inverters output pure sine wave power.

The HP15048D converts 96Vdc to 120/240vac split phase at 60hz and 62.5hz for North American markets.
 
Would someone be willing to explain why you can’t put 2 EG4 48VDC batteries in series and what would/might happen if you did?
At 96 volts, it's shock could kill. Perhaps you should start studying basic electricity before proceeding? There are plenty of online resources. I am a retired electrical engineer.
 
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