Offgrid-House: Battery bank suddenly losing power rapidly?

PorkChopsMmm

I am a unique situation and I am looking for troubleshooting advice. We have a 48V 225 amp hour battery bank connected to our ~1.4KW solar array, all using Outback components. The details should be in my sig line.

We moved into the house over a month ago (installation has been in place since September 2011) and up until yesterday we were doing really well with the solar. But yesterday, despite being at 100% charge during the day our Outback VFX3648 inverter shut down to low voltage in the early morning hours -- around 5:30 AM. We were able to limp along until the sun rose and started charging the panels. I thought this was a fluke, maybe we had too many energy star rated fans going over night, figured it would not happen again, especially because yesterday was a sunny day and we got up to a 100% charged bank. Fast forward to last night -- I didn't run some fans, unplugged our laptop, and don't use some things we have used every night for the past month. I figure we will be fine since I have reduced our power loads and we had a fully charged bank. At 2:30 AM this morning the Outback inverter again shuts down due to low voltage. So 3 hours earlier than the day before with, what I believe to be, less power being used. This morning I ran our 2,000 watt generator to help kick start the system. It ran for 1.5 hours. Shortly after the generator turned off the inverter powered down again. My wife re-filled and re-started the generator and re-booted the Outback inverter. Our plan is to run the generator as much as we can today as it is overcast.

This same exact setup has worked fine for 3 full days while we only received rain and have overcast skies 4 weeks ago. I haven't used the generator for months, I am wondering what could have changed? My next thoughts are to check my Outback MATE to see if I can see any historic trends and high usage numbers. Unforuntately I did not have the MATE hooked up to a PC so I can't export the historical energy used and produced, I can only view it on the MATE.

Do you all have any tips for tracking if any hard wired appliances/devices are using more power than they should? I have my kill-a-watt hooked up to our fridge right now, but so far it has not been producing out of spec numbers. Our large draws would be the fridge, shallow well jet pump (that is only used when water is being used), propane tankless hot water heater (hard wired), and any LED lights we are using (also hard wired).

I am also planning to equalize the batteries this Saturday. I have not done that in a long time and maybe that would contribune to the problem.

Dill

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

first thing I would do is check the fluid levels in all of your batteries and get a specific gravity reading on all of the cells while you're in there.

BB.

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Use an accurate volt meter and check the voltage at each cell/battery.

My guess is you have a poor electrical connection (only 1 battery string is carrying current), or a bad cell (shorted cell taking down bank, open cell preventing a string from charging/discharging).

The other possibility is that the bank was deeply discharged at some point and now damaged (or over a longer time, undercharging sulfated the bank. Did anything "strange" happen a few days to a few weeks ago (bank taken dead, low electrolyte level, or something)?

I always like to suggest a DC Current Clamp Meter--Allows you to measure current in each parallel battery string to make sure all current flow is (relatively) balanced and matches what the rest of the system is telling you.

-Bill

PorkChopsMmm

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Thanks guys. I will try to do all you have suggested tonight. The bank was deeply discharged ~6 months ago but I thought it had recovered since then. I knew it would never be the same, and was thinking of doubling my bank this Fall, but I was hoping to get a few more months out of the batteries.

Bill, too funny. I bought a DC clamp meter from Harbor Freight and I can't get it to work at all. :grr

BB.

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Learning how to "zero" a DC current meter can be confusing (more complicated, less user friendly)--And I have read a few reviews of various (inexpensive) meters that could not be zeroed. You do have to rezero every few minutes (if you are after more accurate readings) because DC meters use a transistor to sense the magnetic field, and they tend to drift.

Even the one I suggest (here) took me a bit of reading/playing around to figure out how the zeroing worked (did this on my car's wiring so I had some idea what was happening--lights on/engine off, engine on/lights on, etc.).

Regarding the bank, from my experience (with mostly automotive batteries) is that if a battery is > 1 year old, and taken "dead", it will fail hard in the next week to couple months.

Do you have numbers on your daily loads in Watt*Hours or Amp*Hours (by season)? A larger battery bank has its own issues (generally needs more panels to keep charged, possibly larger backup AC charger/genset and more fuel use), and if the bank lasts ~2+ times longer, it will still cost you 2x as much to replace.

I always like to start out with known loads, then spec the battery bank... Then the rest (solar, genset, chargers) based on the load/bank capacity.

-Bill

niel

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

you stated the system was in place since sept 2011, but i have to ask if it was actively charging the batteries during the time from its install to the move in day because if it wasn't then the batteries would self discharge and sulfation could've set in? your batteries sound like they are old and abused rather than in a new system. maybe you are drawing too much from them and they weren't getting back to full charge state for some time and this could also sulfate your batteries. as was suggested, do check on the electrolyte levels and specific gravities to be sure you are giving the batteries what they need.

2manytoyz

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

I believe the Harbor Freight clamp-on Ammeter is capable of measuring AC/DC VOLTAGE, but only AC CURRENT. This would explain why it wouldn't work for you for measuring DC currents.

I use an Extech DC Ammeter for measuring DC charging/discharging currents:



This quickly tells me how well things are working. I can measure each bank of solar panels, each panel, and how well each battery is performing. All my batteries are tied to a bus bar, and each battery "should" supply about the same amount of current when a load is applied. Also a good way to check for parasitic loads.

I'd be willing to bet your SG is down. Might have done permanent damage from the deep discharge months ago. If that's the case, check the water, equalize, test again. My guess is they're toast. Hope I'm wrong...

Edit to add: The Extech meter is VERY easy to zero. With the meter off the cable, close the jaws, push the Zero button, verify the reading is zero. Open and close the jaws once more to verify the zero is holding, then place on the DC cable you wish to measure current. Other meters I've used have a wheel (trim pot) that has to be carefully tweaked back and forth to get a good zero, and tends to drift. No such issues with this model.

PorkChopsMmm

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Thanks for the advice. The batteries were new when purchased and tested fine, e.g. no dead cells, back in late August 2011. Installed in September 2011. Actively charged since then. While I was gone once the batteries dropped down very low (I left the inverter on with no loads. For some reason it never shut itself down). I got them charged and ever since then they have worked fine. I also tested their water levels at the time and they looked good. I was not able to get SOC #'s for each battery as my trip was cut short.

BB.

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Also, to make clear--A clamp type amp meter measures the "total" current though the clamp... if you have a + and - wire in the clamp (both power leads to a load), the "sum of the current" will be zero.

You have to be able to get at "one conductor" at a time to measure the current in that conductor (and why a clamp meter cannot simply clamp an a two or three wire lamp cord to measure current flow--you have to split the wires out, or build a short cord with wires split out, to measure the current flow).

-Bill

PorkChopsMmm

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

2manytoyz -- thanks for the reply. I think you may be right -- mine can only read AC current. Here is the one I purchased.

http://www.harborfreight.com/digital-clamp-on-multimeter-95652.html

Test AC/DC voltage, AC current, resistance, insulation test
Easy-to-read LCD display with an upper limit of 1999
0 adjust
500 volt insulation test
Resistance: 200-20k-2Mohm
Rotary switch
Double insulated leads
Low power indicator

BB.

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Yep-- it is that A~ meaning Amps AC vs:

_____________
- - - - - - -

For DC.

And it can get more confusing, because with AC inverters and PWM charge controllers, they use a "pulsing" DC current--So an AC only meter may read AC current in the cabling (possibly even somewhat reasonable AC current).

-Bill

PorkChopsMmm

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Ok, here is what I found. In short water levels look good but when the bank is at ~100% charge it quickly would dip to 80% or 90% when loads were applied. Sorry that isn't more scientific -- it's hard to watch voltage levels because the MATE is in my power shed and not located in my house... yet.

Here are the numbers I got for the batteries (voltages are at rest)



I saw some interesting numbers from this thread on this forum for US Battery golf cart batteries. I wonder, would this line up to my Duracell GC2 batteries purchased at Sam's Club? If so, I think I have been under charging my batteries. My current charge numbers are 60 amps, absorb 57.6V, and Float 54.4V. My equalize numbers are 57.6V for 1 hour. From the thread below it sounds like the equalization should be much higher, e.g. 61V. Any feedback on these numbers?
http://forum.solar-electric.com/showthread.php?5750-US-Battery-Charging-Specs/page2

This is sounding like I need to equalize these guys. Again, my CC is currently set for 57V for 1 hour. The US Battery specs are ~61V. What say you all? Never equalized these before.

westbranch

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

you may find this discussion and actions helpful

http://forum.solar-electric.com/showthread.php?14071-Battery-Condition

offgrid me

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Those Gravity readings look very low. A charged battery should be between 1.265 and 1.275. Usually 1.17 is about 50% capacity and should not be drawn down futher. You also seem to have quite a range of values. I would guess that those batteries are severely sulphated and can no longer accept a charges. What was your absorbe time setting. You may get some life back from them with a good equalizing. Check you sg's every half hour durring eq and stop eq when the sg's stop rising.
Good luck
Ned

PorkChopsMmm wrote: »

Ok, here is what I found. In short water levels look good but when the bank is at ~100% charge it quickly would dip to 80% or 90% when loads were applied. Sorry that isn't more scientific -- it's hard to watch voltage levels because the MATE is in my power shed and not located in my house... yet.

Here are the numbers I got for the batteries (voltages are at rest)



I saw some interesting numbers from this thread on this forum for US Battery golf cart batteries. I wonder, would this line up to my Duracell GC2 batteries purchased at Sam's Club? If so, I think I have been under charging my batteries. My current charge numbers are 60 amps, absorb 57.6V, and Float 54.4V. My equalize numbers are 57.6V for 1 hour. From the thread below it sounds like the equalization should be much higher, e.g. 61V. Any feedback on these numbers?
http://forum.solar-electric.com/showthread.php?5750-US-Battery-Charging-Specs/page2

This is sounding like I need to equalize these guys. Again, my CC is currently set for 57V for 1 hour. The US Battery specs are ~61V. What say you all? Never equalized these before.

Photowhit

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

PorkChopsMmm wrote: »

Ok, here is what I found. In short water levels look good but when the bank is at ~100% charge it quickly would dip to 80% or 90% when loads were applied. Sorry that isn't more scientific -- it's hard to watch voltage levels because the MATE is in my power shed and not located in my house... yet.

If your assessing % full from battery voltage, the drop to 80-90% under load is fine and normal. If you've read the Battery FAQ's you'll find evaluating a battery by voltage is tricky, if not often misleading since charging and loads bounce 'good numbers' around a lot.

PorkChopsMmm wrote: »

My equalize numbers are 57.6V for 1 hour. From the thread below it sounds like the equalization should be much higher, e.g. 61V. Any feedback on these numbers?

Numbers look OK other than the equalizing, there are two basic types of equalizing, if setting a monthly maintanence equalizing for an hour or 2 if you have a BTS(battery temperature sensor) I would suggest @61V for 2 hours.

PorkChopsMmm wrote: »

This is sounding like I need to equalize these guys. Again, my CC is currently set for 57V for 1 hour. The US Battery specs are ~61V. What say you all? Never equalized these before.

The type of trouble shooting equalizing you need to do this weekend is what "Offgrid ME" has eluded to, with a steady 61V until the SG(specific Gravity) no longer rises. You'll want to watch the temperature as well as the SG, If you have a BTS in place I believe your CC will shut down if the batteries get too hot.

PorkChopsMmm

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Thanks for the help, guys. I will jack the equalization up to 61V and leave the current absorption rates and float rates as-is.

I am using the Outback Remote Temperature Sensor (RTS) that shares the temp to the inverter, CC, MATE, etc., so it should stop if they batteries get too hot. Just so I know, what is considered too hot?

When I equalize, should I wait for a sunny day or use the generator? The generator will only run for 1.5 hours or so until it runs out of gas. If it runs out of gas during the equalization cycle will it hurt the batteries? I am assuming I would be stopping the equalization every 30 minutes or so to check gravity anyway.

Thanks again!

P.S. offgrid me -- I believe the absorb time limit is 1 hour. Is that long enough?

BB.

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

For anyone with low SG levels, or deeply cycling batteries, I would tend towards a much longer absorb time (like 4 hours) and see how the battery bank performs (at some point, they start bubbling a lot and using excessive water, SG peaks earlier in absorb cycle, then you can try knocking absorb time back down an hour or two and see what happens).

Some folks here use shorter absorb times in summer (like 2 hours) and longer in winter (4 hours)--Assuming home/cabin is occupied summer and winter.

-Bill

mike95490

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Run the genset early enough in AM , to get the batteries 'Bulked up' so that the solar can do the absorb/Eq.

niel

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

i suspect they are being undercharged. here are the specs for us battery who makes the energizers from what i gathered in my searching.
http://www.usbattery.com/usb_images/charging_instruction_2011_2.pdf

for a 48v battery bank this should translate to 58.8v for the absorb voltage, 52.08v float, and 61.2v eq.

there is some fudge room on that as you can see by the pdf.

Blackcherry04

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Those Batteries need 911 treatment, that low it'll take maybe 10 hours, ( depends on how hard the sulfate is ) of heavy EQ'ing and thats if you can keep the temperature down below 115-120 degrees. I have a water tub I keep water flowing through and drop them down as low as I can get them before I start, pump the water in at the bottom a let it flow out at the top overflow.

Check the SG levels every 30 Minutes and temperature, sometimes you'll have to let them cool.

You'll probably lose some life, but they will be toast soon anyway. You can change the absorb time after you get them up.

PhilS

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

I think the group has narrowed down the problem to your batteries' state-of-charge and I don't disagree.

But you mentioned your water pump that "only pumps when water is being used". Do you have an indicator of some kind that lets you know WHEN it is pumping?

IF you had an unnoticed water leak and that pump came on frequently would you know? And IF it was coming on frequently, would that be enough to draw down your bank?

I have a light (visible from the kitchen window) that is 'on' when my jet pump is 'on'. One time a couple of years ago I noticed the light 'on' when no water was being used. I then found a significant leak under the house. No telling how long it'd have leaked without the indicator light.

I'm not saying it's your problem now, just that having some indicator of when the pump is actually 'on' may help you in the future.

Phil

PorkChopsMmm

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Phil, great advice. I can tell it comes on when we run water but I haven't heard it come on while I have been working outside. How did you wire it so a light would come on?

solar_dave

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

PhilS wrote: »

I think the group has narrowed down the problem to your batteries' state-of-charge and I don't disagree.

But you mentioned your water pump that "only pumps when water is being used". Do you have an indicator of some kind that lets you know WHEN it is pumping?

IF you had an unnoticed water leak and that pump came on frequently would you know? And IF it was coming on frequently, would that be enough to draw down your bank?

I have a light (visible from the kitchen window) that is 'on' when my jet pump is 'on'. One time a couple of years ago I noticed the light 'on' when no water was being used. I then found a significant leak under the house. No telling how long it'd have leaked without the indicator light.

I'm not saying it's your problem now, just that having some indicator of when the pump is actually 'on' may help you in the future.

Phil

Just as a BTW on water leaks, my Mother in law had a condo we were managing for her as a winter rental in a retirement/golf community. The property was unoccupied and a water pipe broke under the slab, I got a call from the HOA guy saying there was water coming out from under the garage door! OMFG! The water bill was over a $1000. The plumber bill was another grand. The carpet replacement was another $1900 as it flooded about half the condo. What a mess, you did right in having the light come on.

PorkChopsMmm

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Eq'ed twice today. 3rd running right now.

1st EQ 6.68V 90 degrees and 1.245
2nd EQ 6.60V 100 degrees and 1.265

I am hoping to get to 1.275... sound good? I will also monitor tomorrow. Thanks for the help!

inetdog

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

PorkChopsMmm wrote: »

Eq'ed twice today. 3rd running right now.

1st EQ 6.68V 90 degrees and 1.245
2nd EQ 6.60V 100 degrees and 1.265

I am hoping to get to 1.275... sound good? I will also monitor tomorrow. Thanks for the help!

Are you using temperature-compensated SG values (either from a compensated hydrometer or from manual adjustment)?

PorkChopsMmm

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Whoops, good catch. They were temp corrected in my spreadsheet... not on my last post. Looks like I am closer to 1.271.

inetdog

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

PorkChopsMmm wrote: »

Whoops, good catch. They were temp corrected in my spreadsheet... not on my last post. Looks like I am closer to 1.271.

In terms of EQ charging, I think that minimizing the differences among cells is more critical than getting all of them to a specific SG. Lots of work to check all the cells, not just one cell from each battery, but should be worth doing once your test cells are in the right neighborhood.

BB.

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Where ever the SG stops rising (after 30-60 minutes of ~5% rate of charge), then that is your 100% state of charge. Log it for each cell and you can check them over time (months/years) and see that everything is going well (or not).

-Bill

PhilS

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

PorkChopsMmm wrote: »

Phil, great advice. I can tell it comes on when we run water but I haven't heard it come on while I have been working outside. How did you wire it so a light would come on?

This a 120V jet pump. I put a second wire to the pressure switch that sends 120V to a porch light on the exterior.

Phil

PorkChopsMmm

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

Well, slight update. After equalizing the batteries almost a month ago I was able to get good SG numbers across all batteries -- right around 1.270 @ 96 degress F. So I thought I was good for the last few weeks then we begun losing power again. I went out and checked the SG and I was down to 1.110 @ 94 degrees -- at ~100% charge 6.34V per battery. So bad news I added water to each cell of each battery and EQ'ed them twice today. I will do another measurement to see if this was able to bring them back up. Each cell was quite low on water, no down to the plates, but maybe 1/2" to 3/4" below the plastic "rim" in the filler cap.

Good news is that Sam's Club said they would replace the batteries. I was hoping to double my battery bank soon from 8 batteries to 16. I only have 6 240W panels right now, with plans to add 3 more in the next few months. Would it be bad to go ahead and double the bank now? Think ~1400 watts of panel can maintain a ~450 amp hour bank @ 48V?

inetdog

Re: Offgrid-House: Battery bank suddenly losing power rapidly?

PorkChopsMmm wrote: »

Well, slight update. After equalizing the batteries almost a month ago I was able to get good SG numbers across all batteries -- right around 1.270 @ 96 degress F. So I thought I was good for the last few weeks then we begun losing power again. I went out and checked the SG and I was down to 1.110 @ 94 degrees -- at ~100% charge 6.34V per battery. So bad news I added water to each cell of each battery and EQ'ed them twice today. I will do another measurement to see if this was able to bring them back up. Each cell was quite low on water, no down to the plates, but maybe 1/2" to 3/4" below the plastic "rim" in the filler cap.

Good news is that Sam's Club said they would replace the batteries. I was hoping to double my battery bank soon from 8 batteries to 16. I only have 6 240W panels right now, with plans to add 3 more in the next few months. Would it be bad to go ahead and double the bank now? Think ~1400 watts of panel can maintain a ~450 amp hour bank @ 48V?

If the SG was low across all of the batteries, I would say that the problem was not lack of equalization but rather a chronic undercharging leading to sulphation. (The trapped lead sulphate cannot get back into solution to allow the SG to rise.) I would run the numbers on available charge amp-hours versus use and look at the settings of the CC before risking a second set of batteries.