Battery issue ?

GreenPowerManiac

Last two times I've noticed all the fuses popped on my battery bank causing "Inlet Low Voltage" on Inverter.  

Replaced them with 10 amp fuses and was good for a few weeks then did it again.  All fuses blown.  Most batteries are from 2008-2009 era.   

Is it time to replace the battery bank or too much charging ???

BB.

Lower battery voltage will cause the inverter to pull more current (power=voltage*current -- Drop the input voltage, need more current to supply the same AC loads).

What is your system design? Battery AH/Voltage, series/parallel connections, where are fuses, size of AC inverter, size of AC loads.

If not AC loads, but DC loads (such as lighting), depending on the load, low battery voltage usually causes the current to fall... But many loads (DC motors driving pumps, LEDs with electronic ballasts, computer running on DC input, etc.) will draw more current as the voltage falls.

Older batteries are going to run lower output voltage... Old wiring (corrosion, poor connections) can cause voltage drop too.

The batteries may be old, but still have capacity--You may have to look at your wiring+loads to figure out how to get more useful life form the batteries.

-Bill

GreenPowerManiac

9 - 120ah deep cycle SLA's in parallel battery bank, MorningStar charge controller 60 amp, Sunforce 2500/4000 inverter.

Fuses are on + battery posts 10amp. 

Load end is in house, multiple 110 circuits, mostly lights, computers, clocks, a de-humidifier, solar water heater pumps and such.

Photowhit

Might disconnect for a while and do load tests on you batteries! One bad battery will bring them all down.

Specifically, I would disconnect from the load, but leave the batteries connected for a night, then disconnect each battery and individually load test each one.

mike95490

9x 120A = 1080Ah bank.  Should have about 100A to properly charge and bubble it.  

10A fuses for each battery seems light, and even with loads spread over 9 batteries, I'd think a 25A fuse would be a more suitable size if you are unable/unwilling to step up to a 24V system with lower current density.

BB.

If you have one or two (for example) parallel batteries failing, that puts a lot more current draw on other batteries...

And, interestingly, it is the "good battery with low resistance" connection that will blow the fuse first.

-Bill

jonr

If you are going to run 9 batteries in parallel, use a clamp on ammeter to check amp balance.   Use wire lengths to balance them.  Then 25A would be about right.

GreenPowerManiac

Every few months I check the water levels and add where necessary.   It's gone years without blowing the fuses.  Took out a bad battery a month ago.  Started at 15 of them.  
I load test them all the time and most only draw 1-3 amps each. Figured if it drew more than 10, it's going bad.  

GreenPowerManiac

Thinking of getting some deep cycle AGM batts.   How many would I need for a max load of 2.5kw and a 40 amp input from array ?
8 AGMs ?
Tired of PM ing the SLA's

BB.

What voltage battery bank?

AGMs can certainly output high currents, both sustained and surge current.

But, the other sizing is how many Watt*Hours per day of usage, days of storage, and maximum discharge... Our standard works out to 2 days of storage and 50% maximum discharge. For flooded cell Lead Acid batteries, this also (usually) gives you a large enough battery bank to supply sustained and surge current.

Even though, you can dump a lot of current into AGM and even (partially charged) lead acid batteries--It seems that as the batteries get full, if there is too much charging current, you can pull the battery out of regulation (i.e., reported 72+ volts on a 48 volt battery bank).

A good maximum load and charging current for Flooded Cell is (roughly):

• 400 AH @ 12 volts (per 1kWatt of load and solar array)
• 200 AH @ 24 volts (per 1kW)
• 100 AH @ 48 volts (per 1kW)

Not a hard limit--But it seems to work well as a starting point for your system design.

-Bill

mcgivor

Even though, you can dump a lot of current into AGM and even (partially charged) lead acid batteries--It seems that as the batteries get full, if there is too much charging current, you can pull the battery out of regulation (i.e., reported 72+ volts on a 48 volt battery bank).

Question for Bill.
Been a fly on the wall and reading this, could you please explain the above, re.if there is too much charging current,  you can pull the battery out of regulation  (i.e. reported 72+volts on a 48 volt  battery bank)

softdown

My vote would be for a 24 volt system. Nine parallel 12 volt batteries? The cables should be 4/0s in my opinion. More so with parallel than serial.

Is connection corrosion a possible issue?

BB.

People tend to look at solar charge controllers as having a "regulated" voltage output. And they do--But it has a "very slow" response time...

A computer 5volt power supply will hold the voltage to 5v +/- 0.25 volts over all conditions (and if it is >5.25v many will "throw a crowbar" on the output (monitoring circuit will short circuit the output if output voltage is exceeded).

Some (few, many, almost all?) MPPT type solar charge controllers appear to have a much longer response to battery voltage. And some will have periods of time where they do not regulate the output voltage at all--For example, during a MPPT sweep (trying to find Vmp and Imp for Pmp operating conditions)--The charge controller will dump the maximum energy from the array into the battery bank for a few seconds while it varies the Vmp and logging Imp (create a little log) to find V*I=P -- During this time, if the battery is near fully charged, the battery literately cannot absorb all of the charging current without having its input voltage "dragged" much higher than normal.

We had one person here with a Schneider (Xantrex) XW installation with large array and (relatively small) AGM battery bank. And it was throwing an error message that the battery voltage was >72 volts (on a 48 volt battery bank) and shutting down.

For flooded cell batteries--They can accept higher charging voltage and current by converting that into hydrogen and oxygen gasses (electrolysis). AGM batteries (at least Concorde/Lifeline batteries) seem to accept very little "excess current" when charged and having high input voltage--So while the can accept very high current when charging a less than full battery--Once full, they (appear) to have very little ability to "eat" excess energy from an MPPT charge controller and will accept very little current--On the order of 1-2 amps for one poster her. Here is a thread talking about corrective equalization behaviour for Concorde AGMs:

http://forum.solar-electric.com/discussion/8457/sulfated-lifeline-concorde-agm-batteries

So--If you have a "small" battery bank and a "large solar array"--The charge controller does not react fast enough to "accurately" regulate its own output voltage. (this can be seen with a car alternator--Don't Do This--If you have a running car and disconnect the car's battery, many alternators will over voltage the car's DC and fry the sensitive components (burn out lights, fry computers, etc.).

The battery is what regulates the short term battery bus voltage. The "charge controller" is what regulates the "long term" battery voltage (i.e., holding 13.6 volts float, 14.7 volts absorb charging, etc.). A solar charge controller will not be able to (accurately) regulate its own output voltage without the battery there to "buffer" the charging current.

There are a ton of different charge controllers out there--Outback (as far as I recall) was known (years ago) for unregulated voltage output during the few seconds MPPT scans (would take battery voltage >> absorb set point).

I do not have any experience with MPPT charge controllers (of any brand)--So newer/different brands of charge controllers may behave differently (better or worse). The rules of thumbs, generally, keep us out of trouble. If there is a specific needs for very large array/very small battery bank--Further research (talking with manufacturers/experimenting, etc.) would be recommended.

-Bill

GreenPowerManiac

Oh, my bad,  12v battery bank.

Usually draws between 200-800 watts consistent during daylight hours 4-16 hours depending on sun/clouds/night.

How many AGM's  (Duration 27 DC) Farm & Fleet for instance caught my eye....Deep Cycle

softdown

GreenPowerManiac said:

Thinking of getting some deep cycle AGM batts.   How many would I need for a max load of 2.5kw and a 40 amp input from array ?
8 AGMs ?
Tired of PM ing the SLA's

I hear you on the flooded lead acids. What is SLA?

I am going to move from FLA to AGM when another battery dies. Half of my clothes have been destroyed by battery acid...for one thing. Finally bought a battery apron. This board almost has a bona fide love affair with the lead acid lady. They can have her.

Too bad AGMs usually costs so much!

westbranch

SLA = starved lead acid =  AGM

Aguarancher

SLA = sealed lead acid

mike95490

me too:
SLA  = Sealed Lead Acid Also called Maintenance Free, , with shorter plates and less capacity (but more fluid / plate ratio),  They hope the battery lasts long enough to reach the end of the warranty before it runs out of water.  Sometimes, you can pop the caps off and add water anyway.

GreenPowerManiac

B.B.  
Any idea what I need to get in AGM's  ?

GreenPowerManiac

PM'd the bank today.  They are FLA's since I've got to check water levels every 3 months.  A few needed topping off, yet pass a load test afterwards.   All fuses intact after a week.  
I still need to know what's the equivalent in AGM's      Now: 9 FLA's about 100ah each  900ah 12v in parallel.  AGM's needed ?

Photowhit

If they are good, you may have other problems. No reason to replace good batteries unless your loads are growing.

There would be some reluctance to suggest an AGM solution. I and many here don't like multiple strings of batteries.  Some places sell larger AGM's but they tend to be very expensive and even with 3 strings it would be hard to reach 900ah. Have you considered going to a 24volt system?

GreenPowerManiac

Yes, and can't do it.  Just bought 1k worth of inverters.  

Photowhit

GreenPowerManiac said:

Yes, and can't do it.  Just bought 1k worth of inverters.  

Is that all?

6 of these will be slightly more than 900ah at 12volts for @$2500
https://www.solar-electric.com/concorde-sunxtender-pvx-3050t.html

4of these will run @$2400for 810ah @12 volts
https://www.solar-electric.com/concorde-sunxtender-pvx-4050ht.html

These 2 year old "new old stock" AGM's would be 780ah possibly of batteries in 3 strings, I think Softdown bought 10 of them.
http://www.ebay.com/itm/DC260-12-Deep-Cycle-AGM-Battery-Group-8D-/262712391966?

were in discussion here;
http://forum.solar-electric.com/discussion/351298/is-this-battery-price-too-good-to-be-true/p1

Marc Kurth

Photowhit said:

If they are good, you may have other problems. No reason to replace good batteries unless your loads are growing.

There would be some reluctance to suggest an AGM solution. I and many here don't like multiple strings of batteries.  Some places sell larger AGM's but they tend to be very expensive and even with 3 strings it would be hard to reach 900ah. Have you considered going to a 24volt system?

AGM's are a great solution for people who just don't do the maintenance, or for remote/unattended locations. They are not the answer for every application by a long shot. Note that I do not claim that AGM's are "better" or even equal except when their unique characteristics are needed.

But just as importantly, all AGM's not created equally - so when someone reports good/bad results - find out what they are using. "My brand of TV broke in 6 months, so all TV's are crap."  I am very opinionated, but I know by my own experience that there are very few AGM's that will perform in the same league as a good flooded battery. So, select wisely.

The common limitation in cell size for AGM's is 1,100 to 1,200 ah @ 2v.  
So a 57 KWH battery bank is basic with a single string, but I am quite comfortable at 2,000 ah at 48v also with higher quality AGM's.

For PV systems, 2v, 900 ah and 2v 1200 ah batteries are huge sellers for me. Cheap? No. Capable of providing a long service life? Yes.

Building a 1000 ah to 2000 ah 12v battery bank really is not rare, BUT it requires very special considerations if you expect it to have a reasonable service life. Jump to 24v or 48v when it makes sense!

softdown

Photowhit said:

GreenPowerManiac said:

Yes, and can't do it.  Just bought 1k worth of inverters.  

Is that all?

6 of these will be slightly more than 900ah at 12volts for @$2500
https://www.solar-electric.com/concorde-sunxtender-pvx-3050t.html

4of these will run @$2400for 810ah @12 volts
https://www.solar-electric.com/concorde-sunxtender-pvx-4050ht.html

These 2 year old "new old stock" AGM's would be 780ah possibly of batteries in 3 strings, I think Softdown bought 10 of them.
http://www.ebay.com/itm/DC260-12-Deep-Cycle-AGM-Battery-Group-8D-/262712391966?

were in discussion here;
http://forum.solar-electric.com/discussion/351298/is-this-battery-price-too-good-to-be-true/p1

That Ebay listing for the AGMs ended a couple weeks ago.

Photowhit

That Ebay listing for the AGMs ended a couple weeks ago.

I know, just letting him know the expense and what people are willing to spend for even old batteries. He should still be able to call it up and view the original listing.

softdown

Photowhit said:

That Ebay listing for the AGMs ended a couple weeks ago.

I know, just letting him know the expense and what people are willing to spend for even old batteries. He should still be able to call it up and view the original listing.

The miles are more important than the years *with properly cared for* batteries. My 8Ds are much maligned around here....yet I still use four made in 2011.

I am ecstatic with that "old" battery purchase. They are all sitting over 12.8 volts in a 45F room. Was planning to sell for awhile....

You do your best to keep me on my toes...

Marc Kurth

I like the 8D performance/life cycle profile from Concorde and Fullriver because I know an awful lot about them. The 8D is right behind the L16 in terms of sheer performance, longevity, self discharge characteristics. There are some others that I do not hold in such high regard.

Be aware that a nice high standing voltage can fool you. Do a basic capacity test to see how they hold up under a sustained load. That battery is designed to reliably deliver 25 amps for 578 minutes. If you have cycled them a few times, I will forecast a runtime of 480-500 minutes at 25 amps. Not bad for 1/3 of the normal price.

If you like "aged out" batteries, PM me about (36) DC160-12 that I can get for an even better ratio of cost/KWH.

Marc