[RE-wrenches] intermittent battery problem
David Katz
dkatz at aeesolar.com
Sat Oct 22 08:01:28 PDT 2011
Ron,
I don't think it was the water. It was probably the 10 hours they ran the generator that brought them up a bit. If the water is low, the electrolyte is more concentrated and will make the s.g seem higher. Adding water to the proper level will make the reading more accurate.
I still think they are pretty sulfated. When they said they reached 29 volts in 5 minutes every morning with a charge of less than 30 amps (an assumption, since they are running a 2500 watt generator), that sounds like a battery with very little capacity. The fact that they stayed at 25.7 all day was probably because of the 800 watt PV array and light loads. It would be interesting to do a real equalization and a capacity test to see what is left of the batteries.
David
David Katz
CTO & Founder
AEE Solar Inc
P: 707 825-1200
F: 707 825-1202
dkatz at aeesolar.com
www.aeesolar.com
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Ron Young
Sent: Friday, October 21, 2011 11:39 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] intermittent battery problem
Hi Maverick & everyone,
I visited the site a couple of days ago and load tested the batteries, checked individual voltages in the string of six Surrette 4KS25's (4.3v each), checked all connections etc. The client told me that when they would go to bed battery volts read 25.7. Through the night this would seem to stay steady. About 4 a.m. as far as they could tell the voltage would drop to about 24.5. This happened without a load present and with no charging present (calm, no wind, no sun). They would start up the generator for five minutes in the morning and see the voltage come up to just above 29v then turn off the generator (a small Honda 2500) and the voltage would settly at 25.7 and remain there most of the day even when using their light loads, some lights, phone system, laptop and the Sunfrost.
When checking the batteries I noticed they needed watering and mentioned this to the customer. The electrolyte was just over the plastic screen above the plates by about 1/4 inch. He said he had just watered them and always kept them filled. I replied that they were low and when he looked he said no, that's where I keep them! When I checked the specific gravity reading it was very rich reading around 1.275 - 1.280. I topped them up properly to about 1/4 inch below the bottom of the cell channel which took about 5 cups per each battery. Of course as soon as I topped them up the s.g. dropped to around 1.175. I told him to put the generator on for about ten hours and call me in the morning.
I heard from the client today and in the last two days the voltage has only dropped from 25.6 to 25.4 overnight and s.g. reading is at 1.260 or better so problem seems to be solved.
So it appears the battery was under watered for several years. I'm still not sure why this would result in a sudden voltage drop, especially in the middle of the night with no loads present and no charging. Any additional thoughts appreciated.
Best Regards,
Ron Young
earthRight Products - Solareagle.com<http://Solareagle.com>
On 2011-10-21, at 5:18 AM, maverick at mavericksolar.com<mailto:maverick at mavericksolar.com> wrote:
Ron,
Just curious what the outcome was?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer (r)
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
On 2011-10-11, at 12:11 PM, Maverick Brown [Maverick Solar] wrote:
Ron,
Sounds like you might have a voltage drop in the system at point of measurement.
A large voltage drop can happen for a few valid reasons.
1. High current demand. > Trimetric or better yet PentaMetric can show this demand.
2. Poor Cable connection. Visual / Thermal inspection or local Vdc measurement along the cable chain.
3. Low to moderate current demand with low SOC. Check the MX60 Logging function to see when the last day "Float" happened, i.e. how many minutes of Float in the last 60 days, etc. If there are none or few, then you still might be at a low SOC. (Trimetric or better yet PentaMetric can show the SOC as well).
Of course, not sure what happened to the Sunfrost, but a DC Clamp meter, might determine if it is normal now.
good luck,
Maverick
________________________________
From: re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Ron Young
Sent: Tuesday, October 11, 2011 2:00 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] intermittent battery problem
Wrenches,
I received some additional info from the customer this morning. They have asked me to hold off my visit until they get a few more clues but some of what they are telling me doesn't necessarily jive with a sulphated battery. Would appreciate comments - here's a quote from their email:
Hi Ron
Still having problems with system. If the batteries are sulphated would the system return to full charge when you remove the load??? Checked our hydrometer against another and it is working fine. Batteries are all either in the green or on the line between green and blue this morning. Display showed the batteries at 25.2 when we got up this morning. About 10:30 this morning---I had just tested all batteries with the hydrometer---the readings dropped to 23.8. Retested batteries---they were in the green. I turned off all loads----the readings returned to 25.2. I turned on the Sunfrost---readings immediately dropped to 23.8. I turned off the Sunfrost--- readings returned to 25.2. I turned on all lights in the house and the readings remained at 25.2. I turned the Sunfrost back on and the readings again stayed at 25.2. The one other thing that happened in the meantime is that the sun came out and we started buying power from the solar system---.1-.3kw. This all seems to be part of a pattern where as soon as we start buying power---whether from sun, wind or gen. the system returns to normal---But we are still suspicious of the Sunfrost because of our problems a few months back.
Ron Young
earthRight Products - Solareagle.com<http://Solareagle.com/>
Alternative Energy Solutions ~ Renewable Energy Products
On 2011-10-09, at 11:56 AM, Ron Young wrote:
As always, impressed and gratified by the number of thoughtful replies from Wrenches, thank you again! It looks like a hefty EQ is in order. I've successfully recovered badly sulphated batteries by putting them through multiple charge/EQ/discharge cycles on more than occasion. Will check out that Sunfrost as well. My mistake was believing that the hydrometer could tell the truth, the whole truth and nothing but the truth but apparently it takes an amp hour meter to keep it honest.
Ron Young
earthRight Products - Solareagle.com<http://Solareagle.com/>
Alternative Energy Solutions ~ Renewable Energy Products
On 2011-10-09, at 11:12 AM, Jonathan Hill wrote:
Ron-
We've seen this issue before,and it is almost always due to badly sulfated batteries. I'd try a LONG (8-12 hrs) EQ charge at 32 volts. We've done this with Hawkers and fixed the problem. I believe the Surrettes could handle this kind of charge, though you might contact Jamie Surrette.
Jonathan Hill, senior system design engineer
Sierra Solar Systems
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Grass Valley, CA 95945
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On Oct 8, 2011, at 6:42 PM, Ron Young wrote:
Thanks Bob but he has a tubular type hydrometer, not the pointer type. They're usually ok but I'll check it against mine when I go there which looks like a certainty.
They EQ the batteries on a regular basis as per my instructions (they say) but will have to nail them down on that. The small 2500w generator worries me but they have 800w solar and a Whisper 100. The wind blows a lot. Inverter is a 3524 Outback.
Ron
On 2011-10-08, at 5:07 PM, bob ellison wrote:
I bet he has a cheap pointer type hydrometer, I have seen them be way off from reality.
My guess is that the gravity is low the voltage changes quickly, specific gravity changes slowly in a battery bank.
To fully charge a 24 volt bank you need to get it to 29 + volts and keep it there for several hours, depending on the battery bank size.
Charging it to 25.4 is nothing in the long run.
Give them a LONG full charge, what are the inverters? Does it ever get an EQ charge?
Bob Ellison
From: re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Ron Young
Sent: Saturday, October 08, 2011 2:02 PM
To: RE-wrenches
Subject: [RE-wrenches] intermittent battery problem
Howdy Wrenches,
One of my customers that lives 3 hours out in the back country is having an intermittent problem that I haven't encountered before. The batteries drop rapidly in voltage but hydrometer readings are in the green. Turning off the inverter and just using DC doesn't change anything. Meters on the Mate, Outback MX and Whisper controller are all the same so it's not a metering problem. On the way to bed the batteries were at 25.4, overnight with no loads they dropped to 22.9 then a short 15 min. charge with a generator brings the batteries back up and two hours later they are at 25.8. This scenario has occurred several times and then doesn't appear for a day or two.
It doesn't seem to be sulfation as the batteries are reading good on the hydrometer every time. All cells check out. The inverter doesn't seem to be the problem. They have a Sunfrost on a separate DC circuit. It sounds like an intermittent circuit problem or electronics issue. Customer has checked and tightened all the connections he can get at but hasn't been inside the components. Would appreciate any suggestions or clues before I make the trip.
Ron Young
earthRight Products - Solareagle.com<http://Solareagle.com/>
Alternative Energy Solutions ~ Renewable Energy Products
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