[RE-wrenches] 120 volt grid tie inverter

Tue Nov 16 11:59:37 PST 2010

On 11/16/2010 11:20 AM, Richard Scott wrote:
> The KACO blueplanet 1502xi inverter has a minimum MPPT voltage of 
> 125Vdc but cannot be connected to a battery.
>
> I would not recommend hooking a battery up to the input of just any 
> grid tie inverter unless it was designed for it.
> The current from a battery is significantly higher than that of a PV 
> array and can damage the inverter or cause it to fail in a way which 
> could be unsafe.
>
> Sincere regards,
> Richard Scott
> KACO New Energy

One thing that could help to make these kinds of connections work would be
to add a power resistor in series, in-between the inverter input and 
battery.

This will limit the current and make the battery look "more like" a PV 
array.

Of course you will lose some energy in that resistor, but the MPPT algorithm
would have a much better chance of getting it right and current 
limiting  safely.
If it's better than going without, then that's better than nothing.

And, of course, one would have to pick a proper resistance (a few Ohms, 
typically),
and a minimum power rating of the resistor.

boB

>
> On 11/16/2010 10:34 AM, Peter Parrish wrote:
>> Bob,
>>
>> So he is grid-tied. But his household loads are all 100 Vdc? I wonder how he
>> charges his battery bank...If it is PV with a charge controller (or wind),
>> then I think he can export to the grid and get both a rebate from his
>> utility and a Federal Tax credit. I assume that he is not interested in
>> powering the 20 HP motor for his sawmill! If he is charging his batteries
>> some other way (small hydro) I don't know about the incentives.
>>
>> But it looks like he is staring at a fully charged battery bank with
>> generation to spare and is thinking "Why not sell this juice to my utility
>> company? Fair question. I have no direct experience with the SB700, but it
>> has been around for eons, and presumably is rock solid and can MPPT at 100 V
>> all day long. The Fronius inverters only work down to 150 V. The Exeltech
>> inverters that I am familiar with work down to 200 V. There must be lower
>> voltage, grid tied inverters out there but the "battery backup" versions
>> assume 24 Vdc or 48 Vdc battery banks. So, with the exception of the SB700,
>> there seems to be a gap between 48 V (maybe 60 Vdc) and 150 Vdc.
>>
>> - Peter
>>
>> Peter T. Parrish, Ph.D., President
>> California Solar Engineering, Inc.
>> 820 Cynthia Ave., Los Angeles, CA 90065
>> CA Lic. 854779, NABCEP Cert. 031806-26
>> peter.parrish at calsolareng.com
>> Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
>>
>>   
>> ________________________________________
>> From:re-wrenches-bounces at lists.re-wrenches.org
>> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of bob ellison
>> Sent: Tuesday, November 16, 2010 5:23 AM
>> To: 'RE-wrenches'
>> Subject: Re: [RE-wrenches] 120 volt grid tie inverter
>>
>> Peter,
>> The fellow is living with a 120 volt DC battery bank, using it to power his
>> place and a 20 HP motor on his sawmill.
>> He wants to reduce the electric bill further than he already has.
>>
>> So we are looking for an inverter that will take 120 volt DC nominal from
>> the panels / batteries and send it to the grid.
>>
>> I am supposed to meet him tomorrow and hope to have more info afterwards.
>>
>> Thanks,
>> Bob Ellison
>>
>> From:re-wrenches-bounces at lists.re-wrenches.org
>> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Peter
>> Parrish
>> Sent: Monday, November 15, 2010 8:38 PM
>> To:glenn.burt at glbcc.com; 'RE-wrenches'
>> Subject: Re: [RE-wrenches] 120 volt grid tie inverter
>>
>> Bob,
>>
>> Do you mean they have a nominal 120 Vdc input? Or do you mean that they want
>> a 120 Vac (RMS) output? If the former, what output voltage do you want? If
>> the latter, what is their nominal dc input voltage (better yet the range of
>> DC input voltages over a range of typical temperatures and irradiance
>> values)?
>>
>> - Peter
>>
>>                                                      
>> Peter T. Parrish, Ph.D., President
>> California Solar Engineering, Inc.
>> 820 Cynthia Ave., Los Angeles, CA 90065
>> CA Lic. 854779, NABCEP Cert. 031806-26
>> peter.parrish at calsolareng.com  
>> Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
>>
>>
>> -----Original Message-----
>> From:re-wrenches-bounces at lists.re-wrenches.org
>> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Glenn Burt
>> Sent: Monday, November 15, 2010 5:29 PM
>> To: 'RE-wrenches'
>> Subject: Re: [RE-wrenches] 120 volt grid tie inverter
>>
>> I think there is still an SMA 700W inverter available that uses 120VAC.
>> -Glenn
>>
>> -----Original Message-----
>> From:re-wrenches-bounces at lists.re-wrenches.org
>> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Bob Ellison
>> Sent: Monday, November 15, 2010 11:14 AM
>> To: RE-wrenches
>> Subject: [RE-wrenches] 120 volt grid tie inverter
>>
>> I have a customer who wants to grid tie a 120 volt dc system
>> Does anyone know of an inverter that can do this?
>>
>> Thanks
>> Bob ellison
>>
>>
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>
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