Hi Mick, While I don't know what SG they are using in those batteries, I'd say the voltage was too high at 28.8. If it was a standard SG then it would be gassing at 28.8 and starting to dry out the batteries. ( do the batteries look concave?)
The OBCC FM does a rebulk adjustment setpoint, but the older MX does not. What makes you think its not undercharge/overuse thats causing the problem? Jay peltz power On Jul 7, 2012, at 2:53 PM, Mick Abraham wrote: > Greetings, All~ > > My client's string of SunXtender two volt AGM's won't hold a charge...after > only two years! The prior AGM batteries also turned to toast prematurely. > There must be a better way, so could we review the Outback charge setpoints? > > Side note: Delta-v from the highest 2v cell to the lowest shows a gap of only > .148v during a charge cycle so cell imbalance is not the likely problem. I > think they're all working together equally bad. > > A small amount of dry powder--light green color resembling verdegris finish > on copper--can be seen around 30% of the +/- posts, in an amount smaller than > 1/8 teaspoon. From this sign, I suspect that the cells have vented and dried > out. The property is vacant 90% of the time so I am mostly focused on the > MX60 solar charge controller as the culprit. > > This is an early vintage Outback controller, firmware version 5.11. > Temperature compensation is in place; automatic EQ is defeated. Bulk & > absorption setpoints exactly match those requested by Concorde/SunXtender: > 28.8 volts bulk/absorption & 26.4 volts Float. The controller does regulate > at these voltage points so it's technically "working"--just grinding up > batteries on a regular basis. > > The Concorde people do not furnish suggestions regarding absorption time or > "rebulking" so that may be the source of trouble. Controller setpoints have > the Absorption Time Limit set for "0 minutes minimum & 1 hour maximum". The > controller is also set to "rebulk" the battery at a 23 volt trigger and > there's an inscrutable setpoint called "End" that's set for 45 amps. I have a > theory about the meaning of that but I'll keep the noise level down... > > If I recall correctly, the Outback end of charge routine in early days was to > start a clock & see how long it takes to move the battery to the > bulk/absorption voltage then apply an equal amount of time for an absorption > charge before shifting to float. Steve Higgins may confirm if that is indeed > the protocol for a version 5.11 controller but: has that method now been > changed in the newer version Flexmax controllers? It seems those now have an > absorption duration value that can be changed so maybe that's what we need--a > replacement controller along with good information on the absorption duration > and/or float setpoints, etc. > > I see that some controllers can even be set to not Float at all. Maybe that's > better: run the charge then stop it all for the rest of the day. OR: thinking > outside the box here...what about a controller that won't initiate charge > cycle at all unless the battery voltage crests down to a trigger point. All I > know for sure is that two sets of valuable batteries have now been ruined so > "normal" charge setpoints are not working well in this situation. > > If some better electronics (such as blending in the Outback capacity monitor > gizmo) might help, I'm all ears. Next time maybe I'll suggest flooded cells > to the client instead of AGM's, but the cells are in a crawlspace that gets > freezing cold at times. > > Thanks in advance for advice & suggestions. A second off grid client has a > similar setup so I need to hotfoot it out there and tweak that (more recent) > Outback controller to match the suggested setpoint revisions...before bad > things happen again. > > Jolliness, > > Mick Abraham, Proprietor > www.abrahamsolar.com > > Voice: 970-731-4675 > _______________________________________________ > 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
