[RE-wrenches] Needed: Outback setpoints that won't ruin AGM's

Mon Jul 9 06:56:03 PDT 2012

(I am posting this private response on the board because I believe it may benefit others)

Marc suggested that you only charge the battery until the current is lowered to 2.5% to 3% of the rated capacity. Doing so will undercharge the battery, leaving a deficit needed to reach 100% SoC. This leaves a quantity of lead sulfate on the plates. Any lead acid battery will be damaged when unconverted sulfate is left for extended periods because it hardens over time rendering portions of the plate inactive. The result is what we refer to as a sulfated battery.

Lifeline specifically specifies how to charge the battery properly and spells out that not doing so voids the warranty. Here is the pertinent part: "The limited warranty does not cover...,sulfated batteries due to undercharging,..."  

Even though the manufacturer specifies 0.5% for a full charge, I typically see 0.2% or less on a new fully charged Concorde AGM. 

Every year I see hundreds of batteries damaged from deficit charging, aka chronic undercharging. In fact, almost ALL batteries that we recycle are not worn out, they are damaged.  The #1 reason? Lack of understanding how to care for batteries. It is stunning how much misunderstanding and misinformation there is about battery charging. I am very willing to help anyone stop this tragic waste of money and resources.

Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103

On Jul 8, 2012, at 11:40 PM, Allan Sindelar wrote:

Larry, 
What do you mean by "deficit charge"? And how would the battery be damaged and the warranty be voided, please?

I have copied Marc for his response.
Allan

Allan Sindelar
Allan at 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

On 7/8/2012 10:49 PM, Larry Crutcher, Starlight Solar Power Systems wrote:
> Allan,
> 
> If you were to charge Lifeline AGM batteries (manufactured by Concorde) as described by Marc Kurth, you will damage the battery and void the warranty. You should never consistently deficit charge any lead acid battery. The proper charge method is clearly spelled out in Document No. 6-0101 Rev. C, Lifeline Technical Service Manual.
> 
> I highly recommend that all Concorde manufactured AGM batteries be charged by following the method described in the aforementioned manual.
> 
> Larry Crutcher
> Starlight Solar Power Systems
> (928) 342-9103
> 
> 
> 
> On Jul 8, 2012, at 10:03 PM, Allan Sindelar wrote:
> 
> Mick and Wrenches,
> I faced a similar question with a new bank just a couple of weeks ago. In my case I asked my distributor, and his response is below. He makes some interesting points, including a very different end amps than the factory's.
> 
> We have received very good service from this distributor, in case any Wrenches are looking for a Concorde distributor.
> Allan
> 
> Allan Sindelar
> Allan at 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:
> 
> I’ve had this conversation with several engineers and the responses are variable – so I will present what I believe to be true.
> 
> -          The aircraft battery side of Concorde says that a fully charged battery is one that reduces its current draw to under a nominal 0.5% of the 20/24 hour rating.
> 
> -          The RV/Marine & Solar guys insist that 2% to 5% is also a realistic number.
> 
> -          The factory only quotes numbers for new batteries – I have not been able to get concrete numbers for “less than new” batteries.
> 
> -          It is my opinion that the “right” number is very low with new batteries and climbs with battery age.
> 
> My choice would be to program a 2.5% to 3% current draw using a temperature compensated charger.
> 
> When looking at real world conditions that you and I encounter daily:
> 
> 1)      Off grid PV systems most often do not have enough available hours to be concerned with excess absorption/acceptance hours. Even “occasional use on weekends” type systems are limited to “x” number of hours of solar input. (It gets dark for several hours every night – no matter what!) In reality, BY FAR more systems suffer from chronic undercharging than excess time in absorption mode!
> 
> 2)      Grid tied battery backed systems, along with wind and hydro turbine systems can be a different animal because of the potential for “unlimited hours” of full power input for charging. THIS is when the current draw being used as a charge level indicator is most often needed, but........
> 
> 3)      Undercharging is still by FAR the most common cause of premature battery failure. I have seen several battery banks survive the abuse of constant 24/7 charging at full absorption levels for five to six years, but I have yet to see one battery bank survive chronic undercharging for five years. These batteries used in RV/Marine/Industrial applications often see constant alternator-regulator outputs of 14.2v for 12 to 16 hours per day continuously. No, they don’t last as long as we want to see for our needs, but they often make it 5-7 years under really harsh conditions coupled with no float time.
> 
> Re-stating my view in simple terms:
> 
> -          A battery bank is fully charged when the current draw drops to 2.5 amps per hundred amps of battery bank capacity. Time to reach this point is almost irrelevant because of the variables.
> 
> -          BUT......a programmed time limit can be a VERY good thing in case of battery system or cabling faults which present a false load to the charging system – resulting in runaway charging!
> 
> -          The best time limit is dependent upon individual project parameters, but a good starting point is 25%-50% more time than the calculated charging time for a depleted battery bank.
> 
> Hoping this makes sense!
> 
> Allan, always feel free to send a note to Concorde to get their input! As I said above, I can’t avoid seeing things through the filter of my experience. That doesn’t always jive with the manual.
> 
> Best,
> 
> Marc Kurth
> 
> Centex Batteries, LLC
> 
> 704 W Highway 71 - Suite B100
> 
> Bastrop, TX 78602
> 
> Ph 512 308-9002
> 
> Fax 877 254-2702
> 
> marc at centexbatteries.com
> 
> http://centexbatteries.com
> 
> From: Allan Sindelar [mailto:allan at positiveenergysolar.com] 
> Sent: Wednesday, June 27, 2012 5:35 PM
> To: marc at centexbatteries.com
> Subject: Need a setting, please
> 
> Marc, 
> Concorde provides good recommendations of voltage setpoints, which we follow. What is missing is a recommendation for absorb time.
> 
> For one of our recent PVX-9159 24V off grid systems, I have changed the charge setpoints, but need to know how long minimum and maximum to set the Outback MX-60 charge controller to stay in absorption mode (at 2.38 vpc with temp compensation) to fully complete charging before switching to float. If the answer is that the battery can stay in absorption indefinitely, then I will set it to the charge controller's maximum duration of 4 hours.
> 
> Could you ask Concorde for a recommendation? If an answer can be provided that includes guidance that is applicable to a variety of situations, that would be best.
> 
> In this case the array is about 1500 watts, or about a C/15 rate, not uncommon for a better off-grid system in our sunny region. 
> 
> Thank you,
> Allan
> 

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