Should my system be F MPTT at low power??

Freewilley · September 2013

Just put in 2 brand new Surrette S530 batteries. My old system was badly sulphated so I really am not sure when various charging modes kick in...what I had before was the system floating at low voltage/SG. So I am really watching this to see if the issue is not just the batteries.

The batts were 1.255/260 at noon. Not a very sunny day, 1.8kwh since noon. Very soon after start up, the system went to float and stayed there must of the day. The SG went up and down a little but drifted down but the CC varied between float and f-mppt all afternoon.
Now, at sundown, it says F-mppt and the voltage says 12.3 and the sg reads 1.205.

Does this make sense?

thanks!
Willy
Mx 60, outback 2512, 2 S530s, mate, Yamaha EF3000, 1000 watt array 24v.

Freewilley · September 2013

Re: Should my system be F MPTT at low power??

Further info....I turned on the genny, which is charging at 8 amps.
After 20 minutes, the MX reads BAT FULL and the voltage is 14,4. The SG has not come up from 1.205.

After about an hour, the genny charging is down at 200 watts (2 amps?) and the SG still reads the same. Voltage on MX is 14.4 and says Bat Full.

again, is this normal? I think not. My setpoints are all at spec from the manual.

Cariboocoot · September 2013

Re: Should my system be F MPTT at low power??

It's normal for batteries that aren't getting fully charged.

First thing you want to do is check your charging settings on both the MX and the FX. You need the Absorb Voltage to be 14.8 here. You need the max Absorb time to be 4 hours - for now. Then you charge them. Start in the morning with the gen through the FX, when the current starts to drop off from the gen, shut it down and let the MX take over.

It really does sound like the Absorb Voltage is too low and the Absorb time is too short.

Also your FX charging current is too high: that 8 Amps is @ 120 VAC; on the 12 VDC side it's the max the FX can put out and double what you'd normally feed the S530 batteries. Cut the charge current back to 5 Amps AC.

It is normal for the MX to read "BAT FULL" when the charge from another source has pushed the batteries up over its Float Voltage and past the Absorb stage.

NorthGuy · September 2013

Re: Should my system be F MPTT at low power??

I had a similar problem with my batteries. I had to dramatically increase absorption voltage to fix it.

What is your absorption voltage setting?

vtmaps · September 2013

Re: Should my system be F MPTT at low power??

Freewilley wrote: »

Further info....I turned on the genny, which is charging at 8 amps.
After 20 minutes, the MX reads BAT FULL and the voltage is 14,4. The SG has not come up from 1.205.

After about an hour, the genny charging is down at 200 watts (2 amps?) and the SG still reads the same. Voltage on MX is 14.4 and says Bat Full.

again, is this normal? I think not. My setpoints are all at spec from the manual.

This is a continuation of the saga: http://forum.solar-electric.com/showthread.php?20628

As in that thread, we need to know what your charge settings are on the inverter. When you run the generator, your inverter (NOT THE MX) is doing the charging. You need to use your Mate to figure out what the inverter is doing while you are running the generator.

--vtMaps

vtmaps · September 2013

Re: Should my system be F MPTT at low power??

Cariboocoot wrote: »

Also your FX charging current is too high: that 8 Amps is @ 120 VAC; on the 12 VDC side it's the max the FX can put out and double what you'd normally feed the S530 batteries. Cut the charge current back to 5 Amps AC.

This is the advice you were given in the other thread. --vtMaps

Freewilley · September 2013

Re: Should my system be F MPTT at low power??

Thanks vtMaps, but I have been given lots of advice....some conflicting.
and I was wrong, the FX Chgr is at 7 amps, not 8. Why it is, is below...

I did not want to go back to that other thread, but since you guys forced me to....in that thread I had initiated my system with a fresh (but suspect) battery paired with a year old stale battery. I learned a lot from that thread! As mentioned in the thread, I communicated directly with Steve at Surrette to attempt to bring up those 2 batts.
I gave up when the distributor swapped my suspect batt with a new one. I bought a new matching batt so I could start fresh.
I seem to have other issues as my problems did not go away.

As to the charging voltage, Steve said 8 amps was proper (I had been at 14 amps when you advised me I was too high and suggested 6 amps) so I have set it at 7. How the hell do I know who is right. I like Steve's background, which many of you know.
Now to fixing this up....
My settings:
FX
absorb setpoint 14.5, time 2:45
float setpoint 13.2 time 2.3 hours
re-float 12.5
EQ setpoint 15.5, time period 4.3 hours

MX
Charger 70 amps,
absorb sp 14.6
float sp 13.2
absorb time 140 minutes min, 4 hr max
vbatt calibration 12.3 0.0 V

Am I missing anything?

What Steve had suggested, and I may try for now, on the two bad boys was....
fx
absorb sp 14.8, time 2:45
8 amps charging, if no solar coming in
float 13.2

MX absorb setpoint 14.9, time 4 hours
float 14.8

I am unsure what the MIN time option is on the MX for absorb time...it says in the manual it must be at least 10 minutes less than the MAX setting....any direction there?

Cariboocoot · September 2013

Re: Should my system be F MPTT at low power??

Two key points: your Absorb Voltage is too low and it is not the same on both charge sources.

Do not worry about a Float set point on the FX as that will not be used for maintaining Float (you don't want the generator running at that point).

AC Amps shown on the MATE for FX charging is approximately 1/10 the DC Amps going to the battery. So your 7 Amps is 70 going to batteries that are 400 Amp hours; that is 17.5% charge rate, which is pretty high but not impossible for them to handle.

You need to maximize the Absorb time and watch what happens with the current in that time; you are looking for a "plateau" where it seems to sit and not go lower for quite a while. At that point Absorb is a waste of time. It should be around 5-10 Amps DC with no loads on.

SG maxing at 1.260 is not good, and what is worse is how rapidly it seems to be falling off. This would again indicate the batteries are not being held in Absorb high enough or long enough to achieve a full recharge.

Freewilley · September 2013

Re: Should my system be F MPTT at low power??

Clarification, the 1.260 reading at start up was as the batteries were delivered....not charged by my system. Interesting to see what the 2nd day will bring tomorrow....

vtmaps · September 2013

Re: Should my system be F MPTT at low power??

Cariboocoot wrote: »

You need to maximize the Absorb time and watch what happens with the current in that time; you are looking for a "plateau" where it seems to sit and not go lower for quite a while. At that point Absorb is a waste of time. It should be around 5-10 Amps DC with no loads on.

If you don't have a battery monitor or a DC clamp ammeter to look for the plateau in the current, you can monitor the SG with your hydrometer. During absorb the inverter holds the battery at a constant voltage (14.8 volts recommended by Steve) and as the battery charges up, the current that it will accept tapers down to the plateau (or "end amps"). At that time you have reached your maximum SG.

Its a lot more convenient to read the current with a meter than to measure SG every 30 minutes during absorb.

One more thing... Steve recommended that absorb time be set to 2:45. That is a reasonable guess, but the time it takes until you reach the end amps will vary every day. The deeper the discharge, the longer it takes to reach end amps.

--vtMaps

Freewilley · September 2013

Re: Should my system be F MPTT at low power??

Could you please give me a little more detail on how I interpolate my SG reading into current?
I know how to work the hydrometer but a little fuzzy on how the readings will tell this tale...

Also, checking the MX, it is reading 12.2 V, and is still saying Batt Full. This is now over 2 hours since I shut down the genny, and 3 since the sun went down. Is that weird?

thanks very much

Cariboocoot · September 2013

Re: Should my system be F MPTT at low power??

Freewilley wrote: »

Could you please give me a little more detail on how I interpolate my SG reading into current?
I know how to work the hydrometer but a little fuzzy on how the readings will tell this tale...

thanks very much

Not to current so much as to state of charge: the specific gravity will stop rising much the same as the current will stop falling (and for the same reason). As vtMaps said it's not the easiest thing to do. It's much easier to be able to watch the MX's numbers if possible (Bulk with gen, let the MX take over).

Blackcherry04 · September 2013

Re: Should my system be F MPTT at low power??

You might try reading the manual for your batteries.

http://www.rolls-battery.com/content/technical-downloads?q=node/51&phpMyAdmin=2eda4dec0bd69647b9e3cf0f71e01d23&phpMyAdmin=9dec4a269d70t7a63be7c

% Charged / Specific Gravity

100% ....1.255 – 1.275
75% ....1.215 – 1.235
50%....1.180 – 1.200
25%....1.155 - 1.165
0% ....1.110 - 1.130

waynefromnscanada · September 2013

Re: Should my system be F MPTT at low power??

Blackcherry04 wrote: »

You might try reading the manual for your batteries.

http://www.rolls-battery.com/content/technical-downloads?q=node/51&phpMyAdmin=2eda4dec0bd69647b9e3cf0f71e01d23&phpMyAdmin=9dec4a269d70t7a63be7c

% Charged / Specific Gravity

100% ....1.255 – 1.275
75% ....1.215 – 1.235
50%....1.180 – 1.200
25%....1.155 - 1.165
0% ....1.110 - 1.130

Yes, my new Rolls / Surrettes are different than what I was used to with the old Power Battery units I had. The SG on the old ones when fully charged ran around 1.3, which was quite high. The new ones hang around 1.25 fully charged. The voltage seems a bit lower overall as well, except when charging. The difference takes some getting used to. At least for me.

Freewilley · September 2013

Re: Should my system be F MPTT at low power??

Yes, that is the way I charge when I have to, genny for an hour or two for coffee and breakfast and washing machine and usually good solar by 930...I understand that I can then watch my MX to show the current being put into batts by the array....so when it dials down the current for a spell (how long?) that means I should end absorb? Exactly how do I do that, change my MX setpoint and let it float?

Thanks for the note about the manual...I read it lots! And I have tried to follow it without success....these tips on this thread are not covered in the manual, that is for sure.

Cariboocoot · September 2013

Re: Should my system be F MPTT at low power??

The MX has an additional function: End Amps. With that set to the "plateau" level it will switch from Absorb to Float regardless of Absorb time past (as long as it is longer than minimum and less than maximum). Note that the FX does not have this function.

You may have to do some adjusting after you get close; the End Amps may need to go up or down a little, same as the Voltage settings. It is also a good idea to have a remote temperature sensor on the MX at least.

Blackcherry04 · September 2013

Re: Should my system be F MPTT at low power??

Maybe you'd be better off to set the " Ending Amps " and forget the time for now. There is a reason to get the SG's to 100 % with a EQ, doesn't sound like they are there and these batteries are headed south just like your last ones.

Absorb Ending Amps Adjustment (EndA)
One way for the MX60 to complete an Absorb cycle before the charge timer (ChgT) reaches zero, is for the Absorb ending Amps to be set to a value other than the default of “00” Amps (see miscellaneous 3 screen). If the Absorb ending amps setting is set to, for example, 12 amps, then, when the battery current dropped to 11.9 amps, the Absorb cycle would end, the charge timer would be reset to zero, and the MX60 would continue in the float stage. The next Bulk/Absorb cycle will not start until either, the next morning, a 24/25 hour period if the sun did not set, (see LOG2 screen), a Force Bulk being initiated, (see miscellaneous 2 screen), or, a Re-Bulk occurs because the battery voltage fell below the ReBulk voltage setting for 90 seconds (see miscellaneous 3 screen).

NorthGuy · September 2013

Re: Should my system be F MPTT at low power??

I found that the maximum in SG and plateau in absorbtion current doesn't necessarily happen at the same time, so I would suggest measuring both every hour.

At the suggested charging voltage of 58V (would be 14.5V on 12V system) I was getting a plateu in current relatively quickly and at a very low level - 0.5% of capacity. But the SG was still very low.

I had to do something, so I strated increasing the voltage. It still took about the same time for the plateau in current to be established, but it was at a higher level. And SG started improving a bit.

I had to increase the absorption voltage quite a bit (to the level which should be considered insane for most batteries), and finally I got the current plateu at about 2% of capacity, and SG was getting to full levels relatively quickly, in 6 hours.

I then left this high voltage and configured end absorb at 2% level (curiously, 2% was the default charger setting). It's been 7 months since then and I've never had any problems with SG.

However, before I got to these experiments I did several very long equalizatons to get SG to where it is supposed to be.

vtmaps · September 2013

Re: Should my system be F MPTT at low power??

Blackcherry04 wrote: »

Maybe you'd be better off to set the " Ending Amps " and forget the time for now.

Programming your MX to stop absorb can be done three ways:
1) use the timer... Steve recommended 2:45 as a reasonable time to try.
2) manually... stay home and watch the MX, and when the current stops falling, tell the MX to force float.
3) use the MX 'end amps' function.

End amps is the best way, but your MX does NOT know how much current is going into the battery... it only knows how much current it is making. If you have any loads (AC or DC) not all of the current that the MX is making goes into the battery.

If you have a constant load, for example a constant 3 amp load, and you want your end amps to be 8 amps, set your end amps on the MX to 11.

Some charge controllers have an integrated battery monitor that can tell the charger what is going into the battery. The outback FM charge controller (successor to the MX) can do that if you have outback's battery monitor.

As a practical matter you need to find an absorb time that gets your batteries fully charged at least once a week. If I have several consecutive sunny days, I only need an hour of absorb. If there have been some cloudy days, my batteries drift down to a lower SOC and when the sunny days return, I cannot get to full charge on just one hour of absorb, but the second or third sunny day in a row will get me to a full charge.

Every system is different... Steve can tell you what will work for most folks most of the time. In order to give a recommendation that works for everyone, he gives a recommendation that will (unnecessarily) overcharge some folks. Overcharging will prevent sulfation, but will shorten battery life by causing plate corrosion.

After you finally get your SG where it belongs, you need to experiment with the absorb times and absorb voltage, using your hydrometer as the judge of what works. You need to find the lowest absorb time and voltage that gets the batteries fully charged every week or so. Be grateful that you have flooded batteries and that you can use your hydrometer to find out what does work for your system.

--vtMaps

Freewilley · September 2013

Re: Should my system be F MPTT at low power??

I want to say a big thank you to those who have posted with advice. It is great that you will share your experience.

It is kind of funny that I have been building and using this system for 5 years (we live off grid here in Northern Ontario for 6 months, the other six renting in AZ) but it is like day one for me. When I started with new batteries 5 years ago I knew very little, even tho I read everything I could find.
So, be patient as I share my observations and ask what is normal for these batteries...I really do not know how NEW batts should perform.

So, I set points to Steve's recomendations, and yours, last night. This a.m. we are socked in and I have been charging for 3 hours just with the genny (now getting just under 100 watts solar).
7;30, started Gen, charging 800 watts, SG reads 1.180
10:00 gen is now charging at 400, so absorb is commencing, SG 1.200
10:30 gen is now charging at 100, SG 1.205

Is this looking like what you would expect?

Cariboocoot · September 2013

Re: Should my system be F MPTT at low power??

You've got a real problem there because the batteries have been taken below 50% SOC (less than 1.200 SG) and only now are coming back up.

Again, get the Absorb Voltage level up and keep the batteries charging until you get that SG in the 1.260+ range and keep it there for a couple of hours at least.

I suppose we should also be looking at what sort of load demands you've got because if the batteries are fully charged at the end of the day and then <50% the next morning you're using more power than you should.

Freewilley · September 2013

Re: Should my system be F MPTT at low power??

At 100 watts of charging, it will take days?? to fully charge this 400 ah battery bank? I am sure you know the formula to see if this is right.
Should I be putting this on equalize to actually fill this up?
I know that Steve seemed to be very hesitant to use EQ like that.
Last month when I was starting up the mixmatched batts that I have now ditched, I was in this situation and the system was floating I passed this info to Steve and he said just leave it floating, not to Equalize. This is where I get very anxious. You folks on the board say Holy Crap, and he says, yep, slow and steady.

As far as my use goes, I think we are pretty light users. But yesterday on start up I did try and test the system...so I ran my dishwasher for an hour (it draws up to 900 watts on an on and off basis over that hour) which would be my major power use. My thoughts are that as the system was on float, it used up juice but never replaced it and just went down down all day.

Cariboocoot · September 2013

Re: Should my system be F MPTT at low power??

Absorb vs. Equalization:
Absorb Voltage is a desired maximum for recharging batteries. Equalization is done above that Voltage for purposes of correcting differences in SG between cells. If you have to run the Equalization Voltage to achieve full charge (not correcting differences) then the Absorb Voltage is too low. You can push Absorb Voltage up to Equalization levels; the trick is that the higher the Voltage goes the harder it is on the battery. Thus EQ levels are done for short periods to correct problems, not every day for standard charging.

But sometimes the higher EQ Voltage is needed to fix an over-all short coming in SG. In fact a few battery makers recommend a regular EQ charge to push things up, and some users have found that keeping the Absorb Voltage lower and only achieving 80-90% SOC daily with a weekly 'boost' at EQ level to achieve full charge works best for them.

For all the science it is still a bit art, and you need to understand the processes involved and adapt them to your application.

But right now, more than anything else, you need to get those batteries to full charge no matter how long it takes or how much you have to push the Voltage up. Just beware of two things: excessive water loss (do not let the plates get exposed) and excessive heat build up in the battery.

Yes it will take a long time. Right now at 50% SOC you're 'missing' roughly 2400 Watt hours of power. Unfortunately it is not as simple as putting 100 Watts to them for 24 hours to get it back. The charge rate will taper off as they charge, slowing the process down, and the batteries will always need more total power to reach full charge than they are capable of returning in discharge. Otherwise it would be as simple as "40 Amp charge rate for 5 hours = 200 Amp hours".

NorthGuy · September 2013

Re: Should my system be F MPTT at low power??

I had numbers very similar to yours. Judging by voltages and currents my batteries were fully charged, but SG was low. Everyone here told me they were sulphated. Trojan's tech support told me they were sulphated. So, I started doing really long equalizations - 10 hours every day without discharging batteries in between. SG was almost normal after the first day, and perfectly normal after the second. I guess that's how the sulphated batteries should do when equalization cures them.

In my case, things turned out to be different. I got the same low SG charging pattern the next day. So they probably were not sulphated. I had to increase absorb voltage dramatically. With that high voltage they charge as expected. There's one more poster here - Chris Olson - who had to increase his battery voltage a lot. Many others needed smaller voltage increase. You might need this as well.

Freewilley · September 2013

Re: Should my system be F MPTT at low power??

I know I seem new, but rest assured I am very familiar with watering batteries. I do know the basics. I spent the last 2 years equalizing my old sulphated batterries. W?hat I do not know is what brand new fresh batteries act like. Not like these, methinks...what the heck is up. I thought buying new ones would get me off this treadmill.

The sg is not going up noticeably, it is 1.205, temp is 80 degrees (ambient is probably 65) and I do hear some bubbling.

Would you go to EQ if you were doing this? Or go with absorb....my absorb SP is already 14.8...should I raise it?

Blackcherry04 · September 2013

Re: Should my system be F MPTT at low power??

Low SG's is ALWAYS a indication of Sulfation unless the original electrolyte has been altered in some way. It may be soft from discharge or hard from deficit charging over a period of time. If you use 10 hours @ 14.5 V or 5 hrs @ 15.5 really doesn't matter as long as your removing it. Any temperature above 115-120 becomes a problem because of warpage. The longest I ever EQ'd a battery was 32 hrs and it's still in service.

Cariboocoot · September 2013

Re: Should my system be F MPTT at low power??

Why I don't like Surrette batteries. :roll:

At 80F you aren't getting too much heating. This is good.

I believe Chris Olsen had his pushed up to over 15 Volts Absorb. I would turn the Absorb Voltage up 2/10's at a time until you get some vigorous bubbling.

EQ is just higher Voltage, so you may as well turn up the Absorb until you can get a level that works consistently for you. If you can't, then you may want to throw in an auto EQ every month or week.

Freewilley · September 2013

Re: Should my system be F MPTT at low power??

What throws me is that these NEW batteries are acting just like my really old abused batteries were, and also like the pair I installed a month ago and yanked out.
The common thread is a mis-reading of the actual voltage. I have always been told this is caused by sulphation.
I am stunned that 2 brand new batts would show up sulphated...I was assured they were a new batch. I see that they no longer put the dates on them...

So I started EQ mode and almost immediatly the MX reads 15.8 and the EQ timer starts. Even tho the SG is telling me the charged level is low, around 1.205
But there seems to be a common thread of voltage being read as much higher than it is (and yes I am aware of the basics of higher voltage being shown when charging and for hours afterwards)....it leaves me struggling with:
is there a problem in my system itself, like the MX 60. But I reject that as the Mate reads the same voltage (off by one-tenth of a volt, usually) and the FX acts the same when it is charging without the Mate involved.

I have no issue with doing an EQ to clean the plates up and proceeding...but I am not sure things are going to change and I sure do not want to degrade these newbies

This is driving me nuts.....

Blackcherry04 · September 2013

Re: Should my system be F MPTT at low power??

It only takes a clean Square inch of plate to give you voltage, but that square inch is all the capacity you have if you only looked at Voltage. First off it takes 20-50 cycles for a new set of batteries to peak their ability to deliver their capacity. You have to get past the surface of the plates into the pores of the lead. The first EQ's will open the pores and clean the sulfate out so the battery can produce more. If you get the SG's up now and keep them there you'll have a long service life, otherwise history will repeat it's self.

NorthGuy · September 2013

Re: Should my system be F MPTT at low power??

Freewilley wrote: »

Even tho the SG is telling me the charged level is low, around 1.205

In your first post, you said they were 1.255/1.260 at noon. How long ago?

vtmaps · September 2013

Re: Should my system be F MPTT at low power??

Freewilley wrote: »

I am stunned that 2 brand new batts would show up sulphated...I was assured they were a new batch.

Any battery that is not fully charged is "sulfated" and has a low SG. When a battery is first discharged, the sulfate crystals are soft, but charging the battery puts them back into solution. If the battery stays discharged too long, the crystals harden and cannot be put back into solution by charging.

Common usage is that when someone says their batteries are sulfated, they mean hard sulfation. The way to know whether sulfation is hard or soft is to try charging the battery. Since the SG is low, your new batteries are sulfated, but its not obvious (yet) that your batteries are hard sulfated.

--vtMaps

Should my system be F MPTT at low power??

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