[RE-wrenches] AC Coupling

[Darryl Thayer]

The balancer did a good job on helping share the load, for example if I had a 30 amp load on the 12 volt leg of the 24 volt system the equalizer would supply perhaps 29.5 amps but the 12 volt battery would supply the rest, even though close, the 12 volt section does more work tahn the 12 to 24 volt section.  The only way this can be made up is to overcharge the 12-24 volt section such that the 12 volt get charged.  
DT

From: R Ray Walters <ray at solarray.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Saturday, September 3, 2011 6:18 PM
Subject: Re: [RE-wrenches] AC Coupling

Hi Jay;

I agree, for long outages, a generator is the way to go. It just doesn't make sense to have 5 days of lead acid battery sitting there for years waiting to be used once or twice in an epic ice storm.
On the other hand, many places have very unreliable grid power with short outages every few days. A battery based backup system is great in those cases, but I rarely size the bank for more than a day of storage and I usually use sealed batteries. I look at it as a big UPS system, that if managed could limp along for longer in an extended outage.
I start any system design of this nature with this question: How often does the power go out?
RIght there, I talk more than half the folks out of batteries, while the rest know what they're getting (and not getting).

R. Walters
ray at solarray.com
Solar Engineer




On Sep 2, 2011, at 7:15 PM, jay peltz wrote:

> HI Larry,
> 
> I'll chime in here with the "other" option, ie no batteries at all.
> 
> Instead its a back up generator.
> I've found them to be much cheaper, and if you are expecting a longer outage then weather is usually a problem ie its overcast and therefor you'll need a backup for your battery system anyway, so 
> just go with the backup.
> 
> jay
> 
> peltz power
> 
> 
> On Sep 2, 2011, at 8:51 AM, Larry Brown wrote:
> 
>> Wrenches,
>> 
>> After Hurricane Irene left a lot of people without power here in the Northeast, customers who have grid-tied systems are asking about some battery backup to power some essential loads.
>> 
>> We have used Sunny Islands but they require either 2 Sunny Islands or a step up transformer to get 240 volts for the well pump.  Schneider Electric  (Xantrex XW) inverters look like they would work  for this application and do 120/240 volt output as well and we have used these in off grid applications but not as AC coupled.  I have considered Magnum because they also do 120/240 volts but they need battery diversion to ensure the batteries are not over charged.
>> 
>> None of these systems are going to be rewired as a DC system so I am looking for any feed back on what others are using to AC couple to existing grid-tied systems to provide some battery backup.
>> 
>> Thanks
>> Larry
>> 
>> Larry Brown
>> Sun Mountain_______________________________________________
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