Phil, Good explanation of the feature. When did GCC make it into the firmware, and can the older ones be updated? It sounds like a perfect solution for some of my installations.
On Fri, Jul 20, 2012 at 12:34 AM, Phil Undercuffler <solarp...@gmail.com>wrote: > OutBack implemented Global Charge Control in the FM charge controllers > a while back, based on the input of the good folk at SELF who worked > to power a number of hospitals and clinics in Haiti after the > earthquake. In some of those systems, the PV array was based on the > typical running consumption of the hospital, in the 30 - 100 kW if I > remember right, and the battery bank was relatively modest. However, > on the weekends and holidays without the normal AC loads the PV input > was considerably more than the battery could absorb without > destructive heating, something like a C2 or C5 rate. > > Global Charge Control is implemented using the MATE3, a FN-DC and FM > charge controllers set to GT mode. You set a high charge current > limit in the M3, and then it monitors the charge current going to the > batteries. In normal operating mode the controllers stay in wide open > mode, harvesting as much power as possible. However if the loads drop > and the total current from the charging sources begin exceed the > global charge limit, the system compensates and the controllers back > off to prevent sending too much current to the batteries. > > In today's world of PV modules being cheaper than diesel, we're seeing > a lot more systems that can use this tool. > > Hope this helps, > > Phil > > > > On Thu, Jul 19, 2012 at 7:56 PM, b...@midnitesolar.com > <b...@midnitesolar.com> wrote: > > > > > > I didn't see that Brian T had the same idea until after I sent that email > > off to Allan... > > boB > > > > > > > > > > > > On 7/19/2012 7:53 PM, Allan Sindelar wrote: > > > > Wrenches, > > I forwarded Brian's post on to Robin at Midnite, as I thought it was an > > interesting idea. Below is his response, as well as boB's. > > Allan > > > > Allan Sindelar > > al...@positiveenergysolar.com > > NABCEP Certified Photovoltaic Installer > > NABCEP Certified Technical Sales Professional > > New Mexico EE98J Journeyman Electrician > > Founder and Chief Technology Officer > > Positive Energy, Inc. > > 3209 Richards Lane (note new address) > > Santa Fe, New Mexico 87507 > > 505 424-1112 > > www.positiveenergysolar.com > > > > Allan, It is simpler than what is being suggested. The reason they want > to > > limit to 20 amps is because the battery doesn’t need anymore than that. > The > > controller will automatically limit the charge current as the battery > gets > > full. If a large load is turned on, the controller will try to refill the > > battery up to its capacity. The 80 amps will quickly be reduced because > the > > voltage will rise to the point where the charge tapers off. > > > > There is nothing else that needs to be done. If the problem is that the > > battery bank is too small for a big controller, the best answer is to get > > more batteries. A 80 amp charger into a 200 amp hour battery is going to > > raise the battery voltage so quick, it will not affect the battery at > all. > > By the way, discharging a battery at 60 or 80 amps is probably going to > do > > damage to a small battery also. We do have an input on the Classic that > > could probably be programmed to do as requested. That input feature has > yet > > to be implemented. I’m sure we will have discussions about this when the > > time comes to write the input code. Maybe this feature will be designed > in, > > but it doesn’t sound like it is a very good feature to spend a bunch of > time > > on. After all, the main problem is that the battery bank is just too > darned > > small. > > > > Bob, Tom and Ryan do you have any comments on the subject? > > > > Thanks, > > > > Robin > > > > > > > > One idea I had in mind was to have an option, in software, to limit the > > current into the battery, > > when the charging current goes above some set threshold. The controller > > would have to get its information from > > the battery monitor over the network. > > > > If it is a grid tie system and grid is there and GT inverter is selling, > > then no problem... The controller > > can work at its full output. If grid or loads go away, then the CC will > > know and it can throttle back at > > that time. > > > > We don't have a battery monitor yet, but we will have one. This will be > one > > of the settings as well as > > Re-Bulk based on state of charge, ending amps and those types of things. > > > > boB > > > > On 7/19/2012 8:34 PM, maver...@mavericksolar.com wrote: > > > > I say it is waste of time. > > > > 1. AGM batteries can take the high current and you are right, the absorb > > voltage is reached and the absorb current is tapered rather quickly. > Current > > generation charge controllers are rather fast at the transitions. I have > a > > bunch of data from a system with a PentaMetric that shows the battery > bank > > going to absorb voltage at grid tie, during cloud events, but only for a > few > > seconds at a time. > > > > 2. A properly designed GTBB system should cover the connected loads for > 24 > > hours of each sunny day, at a minimum. Keep in mind, off grid systems are > > designed for that, and 3 days + of backup, etc. > > > > 3. I would say, based on my experience, the minimum battery bank should > be > > 400Ah. I personally try to set it at 600Ah (48V). It is a backup system > > after all. But the key is the customer's expectations...who are they > going > > to call after the lights go out? > > > > > > Thank you, > > > > Maverick > > > > > > Maverick Brown > > BSEET, NABCEP Certified Solar PV Installer ® > > President & CEO > > Maverick Solar Enterprises, Inc. > > Office: 512-919-4493 > > Cell: 512-460-9825 > > > > Sent from my HondaJet! > > > > On Jul 19, 2012, at 6:35 PM, Brian Teitelbaum <bteitelb...@aeesolar.com> > > wrote: > > > > Drake, > > > > > > > > I’ve been hounding a couple of the charge controller manufactures about > this > > issue, but so far I just haven’t seen a light bulb go off in their heads, > > but I’ll keep trying, and maybe this is a better forum to do it. > > > > > > > > MPPT controllers can be adjusted to current limit at amperage values > below > > their rating, but if you do that, you are also limiting the output of the > > array in general, and the amount of PV power available to run the loads > > directly from the array (through the inverter). Not the best use of > > available PV power. > > > > > > > > Say you have an 80A controller and a 200AH battery. With current > technology, > > you have two choices: > > > > > > > > Let the controller operate at 80A. If you have loads to draw off some of > the > > current (or sell to the grid), great, but if not you could be seeing a > > charge rate of C/2.5, which would be pretty hard on a sealed 200AH > battery, > > to say the least. Granted, the battery voltage would rise pretty quickly, > > and the controller would start to taper off, but it would still see high > > currents especially if the absorption time is set long. Not a happy > > scenario. > > > > > > > > Or, you can set the current limiting on the controller to 20A for a C/10 > > charge rate. But if you had loads drawing 60A, you would be pulling that > > additional 40A from the battery and not using the array’s full power. > Also > > not a happy scenario. > > > > > > > > What we need is a controller that can read the signal from a shunt at the > > battery, and use that as the basis of current limiting control. > > > > > > > > For example, if we have an array that can produce 80A of current, but we > > want to limit the battery to 20A of charge, there would be 60A of > potential > > current there to run loads without drawing on the battery. If there are > no > > loads running, the controller should current limit at 20A (reading from a > > shunt), but if loads are turned on, the controller should be able to let > > more current through while still limiting the battery to 20A. When loads > are > > shut off, the controller should go back to a 20A limit. > > > > > > > > This doesn’t all have to happen very quickly as a battery can take a > heavier > > charge for a short period of time, but I think that this would be a major > > improvement of controller function. > > > > > > > > Of course, if you are grid-tied you can sell all the excess power, but if > > the grid goes down, or you are off-grid….? > > > > > > > > Because of the low cost of PV and the high cost of batteries these days, > I’m > > seeing more and more requests for large arrays with smaller batteries. I > > also think that PV is now cheap enough to allow for oversizing of arrays > for > > better battery charging on cloudy days, which can reduce generator run > > times. We need smarter controllers. > > > > > > > > What say ye, charge controller gurus? > > > > > > > > Brian Teitelbaum > > > > AEE Solar > > > > > > > > From: re-wrenches-boun...@lists.re-wrenches.org > > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Drake > > Sent: Thursday, July 19, 2012 2:21 PM > > To: RE-wrenches > > Subject: [RE-wrenches] Small battery bank vs too large array > > > > > > > > Hello Wrenches, > > > > Where can I get a device that will measure current through a shunt and > > create a signal to trigger a relay? > > > > We want to be able to use a 2 kW array with four, 200 AH sealed > batteries on > > an Outback system. 2 kW of PV would be too much amperage for the > batteries. > > The idea is to open relays to disengage strings in conditions of high > > current to the batteries. > > > > The reason for this is to create backup systems where power will be > > abundantly available when the sun shines. The system will normally > connect > > to the grid, except during outages. In normal charging conditions the > power > > will go straight to the grid. When the grid is down, power will be > > available for loads and battery charging, but batteries will be protected > > from overcharge? > > > > Any suggestions on ways to accomplish this are welcome! > > > > Thanks > > > > Drake > > > > > > Drake Chamberlin > > Athens Electric LLC > > OH License 44810 > > CO License 3773 > > NABCEP Certified Solar PV Installer > > 740-448-7328 > > http://athens-electric.com/ > > > > _______________________________________________ > > List sponsored by Home Power magazine > > > > List Address: RE-wrenches@lists.re-wrenches.org > > > > Options & settings: > > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > > > List-Archive: > > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > > > List rules & etiquette: > > www.re-wrenches.org/etiquette.htm > > > > Check out participant bios: > > www.members.re-wrenches.org > > > > > > > > _______________________________________________ > > List sponsored by Home Power magazine > > > > List Address: RE-wrenches@lists.re-wrenches.org > > > > Options & settings: > > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > > > List-Archive: > > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > > > List rules & etiquette: > > www.re-wrenches.org/etiquette.htm > > > > Check out participant bios: > > www.members.re-wrenches.org > > > > > > > > > > > > _______________________________________________ > > List sponsored by Home Power magazine > > > > List Address: RE-wrenches@lists.re-wrenches.org > > > > Options & settings: > > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > > > List-Archive: > > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > > > List rules & etiquette: > > www.re-wrenches.org/etiquette.htm > > > > Check out participant bios: > > www.members.re-wrenches.org > > > > > > > > > > _______________________________________________ > > List sponsored by Home Power magazine > > > > List Address: RE-wrenches@lists.re-wrenches.org > > > > Options & settings: > > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > > > List-Archive: > > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > > > List rules & etiquette: > > www.re-wrenches.org/etiquette.htm > > > > Check out participant bios: > > www.members.re-wrenches.org > > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > -- Chris Mason President, Comet Systems Ltd www.cometenergysystems.com Cell: 264.235.5670 Skype: netconcepts
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