Working to figure out what I don't know.

softdown

I wouldn't sleep well with less than three gensets. But people sometimes laugh at my extensive preparations. Can't think of a time that my repair guy didn't have two of my gensets in for repair. But doing construction....I used them a LOT. Don't ever let me look at your gensets. They break when I look at them.

BB.

The old emergency planning saw:

1 is none
2 is one
3 is two

Have a friend that is ex-US Coast Guard--As was said here a few weeks ago, redundancy for them was 3 (light houses, etc.).

-Bill

Denman

Figured I should update as I've dropped off the radar for a ridiculously long time.

Based on the good info and guidance I got here I've finished the upgrade to my system and it seems to be working pretty well. 
New system: 24 260W panels, 6 parallel strings of 4 panels in series; Magnum PT100 charge controller; Magnum inverters totaling 8.8 KW; 700 ah battery bank connected with 2 X 4/0 copper leads; Generac EcoGen 15KW propane generator set to auto start on low battery voltage or excessive load; the new single point rooftop shut down system required by NESC for rooftop solar (went with a local installers system rather than the more expensive prefab one sold all over, saved a bunch of money and my electrical inspector likes it just fine).

So far it's all working pretty darned well. I pulled out the old system (panels, racks, inverter, charge controller and generator) and will install the old system for a different building to which I've run properly sized secondary wire so that I can do a throw over breaker just in case of problems. I even got a nice building (8X8) from one of our electrical substations to serve as the inverter/battery building to keep the works and vibrations separate from the new building. It's been pretty fun and with the new, lower, price on panels I basically put in an array 3 X the size of the original for the same total panel price. That double stack Magnum set up was a bit pricy but provides us the flexibility to use the occasional larger load during the day after the battery bank is charged up. I've seen 75 amps going through the system (at 64 vdc) when we're equalizing. The rolls-surrette site lists that as the proper equalize charge for my battery bank. The Magnum PT 100 charge controller looks to be operating as promised and I like having only one charge controller rather than messing with getting a parallel set installed and playing nice together. The Generac EcoGen 15KW generator really only runs for exercise up to now. I installed the new solar panels last July (put my 80 year old parents to work helping out, they had a great time) so we'll see how we do through the winter. I've been nothing but glad that in the first installation I made sure to put in large enough wiring on the 120/240 vac secondaries that I didn't have to upgrade that. I also went with nice flexible wiring for the 4/0 battery wire this time rather than the much stiffer stuff I'm used to using. The difference is amazing and worth the cost. 

Now that it's getting to be the dark time of year we'll see how snow and shorter days work with the system. My only real experiment so far with this set up is going with the 6 parallel strings of 4 panels in series. I did that thinking it would result in a high enough voltage (vdc) coming off the panel strings to still be useable with occluded sun. So far so good.

I'd like to thank everyone here for their helpful input, humor and patience. 

Vic

Hi Denman,   thanks for the update.

OK,  so,  it appears that you have two strings of Surrette batteries ...   are these the same batteries that you were using when this Thread was started?

A 64 V EQ voltage is a bit high for a maintenance EQ.  Surrette seems to be constantly tweaking its Battery Manual.  Here is a Link to the latest one:
http://www.rollsbattery.com/wp-content/plugins/rollsbatteries/pdfs/Rolls_Battery_Manual.pdf

It appeared that the Surrette batteries that you had when this Thread began,  had somewhat low SGs,  and you did some   L O N  G   EQs which resulted in fairly high battery temperatures,  so am curious about weather this is that same battery bank.

And,  from re-reading this Thread, errrrr  I mean Discussion,  and your latest Post,  think that perhaps you might be best served by doing all of the Absorb stage (or at least almost all of it)  before trying to EQ the battery.   This should reduce the current into the battery for voltages above Vabs,  and also at the beginning of the EQ.   In general,  it is recommended that the EQ current (into the battery,  as measured by a Shunt)  be kept at or below 5% of actual 20 hour Capacity.   You had mentioned seeing 75 A current at a voltage of 64 volts ...   this might be the current output of the CC,  or perhaps,  your system does use a  Shunt to measure the actual battery charge current (?).

Also,  IMO,  the EQ voltage should be Temperature Compensated (at the standard Surrette value of --5mV/Cell/degree C change from 25C for Flooded batteries.   Am not certain that the Magnum CC has this capability.   If not,  it should be done manually.

Also,  there should be no real benefit in running higher String voltage verses the amount of power that the PVs can produce.   As long as the string voltage is sufficient for the CC to find the appropriate MPP,  the relative amount of power will not be very much different with higher string V,  verses a lower one that Is within the ability of the CC to find the optimum MPP.   Generally,  there will be a bit of a reduction in the efficiency of the CC,  when operation at relatively high Vin.

All my opinions.   Vic

Denman

It's the same set of surrettes. Thanks for the links and info, I'll go take a look. I do like keeping up so that I can keep them up. By the time the next battery bank gets installed I'm excited to see what fun new things are available.