Hi Jamie,
Thanks for the link. I find the Rolls/Surrette instructions puzzling.
They suggest a bulk phase at I1 (presumably 0.25xC20 which is fine),
followed by an absorb phase " The charger should maintain the voltage
U0 until the current tapers to I1" This current I1 makes no sense to
me in the second stage, but the graph shows current dropping to
0.012xC20 which does make sense and corresponds to the Fullriver
instructions linked by Larry.
The proper charging procedure clearly requires that the
charger/regulator measures the charging current (not just the PV
current and/or wind/hydro current, since there may be a load).
My questions to the Wrenches List is: "What hardware do wrenches use
to regulate the charge on an AGM battery?" Does everyone use this
Blue Sky Energy device? Is it possible to use AGM batteries with a
conventional diversion controller such as the Morningstar Tristar,
and if so how do you determine the transition from 2.45 V/cell to 2.3
V/cell? Morningstar offer a timed transition, but without knowledge
of current or of SOC this is rather less precise.
Both of the charging methods in the agm-faqs linked below (and in the
Fullriver document) require measurement of the charging current to
determine the correct transition from one stage to the next.
Measurement of dV/dt is also suggested in the case of constant
current charging. Who actually follows these guidelines, and can AGM
batteries operate successfully without?
thanks!
Hugh
At 18:41 -0300 25/4/11, James Surrette wrote:
Content-Type: text/html; charset=US-ASCII
Content-Description: HTML
Hi Hugh,
Here is the charging information for our AGMs.
Please let us know if you need anything else.
<http://www.surrette.com/content/agm-faqs>http://www.surrette.com/content/agm-faqs
Regards,,
Jamie
"Starlight Solar, Larry Crutcher" <la...@starlightsolar.com>
4/25/2011 6:04 PM >>>
Hi Hugh,
An AGM battery is considered full when the current drops below a specified
amount. Lifeline, for instance, is considered full when current is less than
0.5 amps per 100AH. The Blue Sky Energy IPN Pro Remote
<http://www.blueskyenergyinc.com/products/details/ipn_proremote/>http://www.blueskyenergyinc.com/products/details/ipn_proremote/ will
allow
you to program the transition into float mode based on the amount of current
flowing through a shunt. This can be very useful for your project that
involves opportunity charging. Multiple charge sources can be monitored by
the IPN Pro simultaneously. For us, it is the most ideal charger for VRLA
batteries.
Here's a link to some charging instructions for the Fullriver AGM:
<http://www.fullriver.com/products/admin/upfile/Charginginstruction.pdf>http://www.fullriver.com/products/admin/upfile/Charginginstruction.pdf
Larry
----- Original Message -----
From: "Hugh" <h...@scoraigwind.co.uk>
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Sent: Sunday, April 24, 2011 12:11 AM
Subject: Re: [RE-wrenches] AGM battery charging, more details
| Thanks, Larry for the detailed response
| >
| >
| >Generally, the manufacturers charge recommendations should be followed.
|
| Yes but the issue I have is to know when and how to switch from
| absorption to float. The Tristar has its own decision process but is
| it correct? And if not then are the settings suitable.
|
| > If you take away the red paint, I believe the Rolls AGM is the
| >Fullriver DC series battery. We started selling Fullriver last year
| >and I was surprised to find the very high absorb voltage
| >recommendation. For the DC400-6 (415AH) in cycle use they recommend
| >charging at 29 to 29.8 volts and float at 27.6 @25C! That is the
| >highest AGM voltage settings I have seen from any manufacturer.
|
| That's my worry.
|
| >
| >My thinking about AGM's is that the float voltage and transition
| >current are much more important factors than absorb voltage and
| >current.
|
| Transition current is not in the vocabulary of the Tristar
| controller. I am not aware of a product that has this feature aside
| from maybe some inverters. I have read in an Outback manual that
| you should program the absorb time based on charge current
| measurements, but the logic of this depends on the battery being
| 'flat' to the same degree at the start of each charge - whereas wind
| and solar charging is not like that.
|
| >For most AGM's, initial charge current is almost unlimited. However,
| >Fullriver recommends current limiting and constant voltage for the
| >bulk/absorb cycle. Their current limit is .15 to .35*C20 rate. BTW,
| >make sure to adjust the temp. comp to 3mV/C/C for float. That is
| >lower than most.
|
| Tristar default is 5 mV/C/C but can be modified by RS232 lead and
| software intervention.
|
| >
| >Equipment in a 24 volt system should be fine up to 32 to 33 volts.
| >Check the specs.
|
| It's not me that has the problem it's the telemetry engineers. I
| assume they read the manual. But reduced temp comp helps.
|
| >
| >What I said about equalizing was that I had done it twice to my
| >personal AGM battery bank. After the battery is fully charged (<0.2A
| >per 100ah @ C20) I put each battery, not each string, on a current
| >controlled charger. The current setting is .05*C20.
|
| That is 5 amps for a 100Ah battery? Does this not make them gas?
|
| >I don't use voltage regulation when I do this. Once the battery
| >reaches 2.58 V/Cell, I charge for about 4 more hours always
| >monitoring battery temperature. I use this process to recover AGM
| >battery capacity and it has been mostly successful with all
| >brands. No more puzzle.
|
| Thanks - AGMs are a puzzle to me but you make it sound pretty simple.
| I do still have an issue with controlling the charge rate using
| existing technology on an opportunity charging system where the
| battery may be in any state of charge when the wind starts blowing,
| or sun starts to shine.
|
| best wishes,
| --
| Hugh Piggott
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Scoraig
http://www.scoraigwind.co.uk
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