Controller Issues?

Derik · January 2011

Since I don't have a generator back up yet and we have had our share of cloudy weather I decided to increase my Absorb time to 4 hours. I did this adjustment on New Years day. We had two days of full sun but I was here and used a lot of power for two days. The Hydrometer reading on Sunday night when I left was 1.237 after charging all day but with heavy power use. This is the Temp adjusted hydrometer reading.

I was off site Mon, Tue and Wed. We had full sun on Tue and Wed. tonight when I got here the Hydrometer reading was 1.238 and according to the Mate I made just 4.9 KW.

On Sat I made 9.5 KW with an end hydrometer rating of 1.233

Sunday I made 8.5Kw with and end hydrometer rating of 1.237

The only Variations is on Wed night (tonight)I took the reading around 6:30pm and had a few lights on. The other two days readings were taken just after charging about 4:00pm.

With full sun on Wed why would my system only make 4.9 KW?? Voltage was 25.2 when I got here with battery temp around 50 degrees.

I realize I was treading water over the weekend but I would think I would have made 8-9kw today and since I wasn't here I would have hydrometer ratings at 1.255 which is full for my newer L-16 RE B's.

I have never run the batteries lower than 1.185 and have normally kept them 80-90% every day or two.

Night time temps are 30-40 inside the insulated batt box and highs are 50 degrees.

All Hydrometer readings are temp adjusted which isn't an exact science since there is room to error in reading the small lines on the temp.

Oh, and Charge Controller is pumping out 60 amps when it starts absorb and about 18 during the last hour.

9-215watt panels, FM 80 Charge Controller, Flex 500 with Hub and Mate, 12 L-16 batteries. 24 volt system. Located In Southern Southern CA.

BB. · January 2011

Re: Controller Issues?

What is the Battery Bank Voltage when in Absorb? Float setting? Have you confirmed with a meter on the battery bank vs the charge controller?

How long and what gauge is the cable between the FM80 and the battery bank?

How much water are you using (need to refill every ~2 months)?

I assume the 25.2 volts is battery resting voltage (no charge/no load for several hours)?

Certainly lengthening the absorb timer during winter/heavier use is not a bad thing to do.

-Bill

hillbilly · January 2011

Re: Controller Issues?

Derik wrote: »

...
With full sun on Wed why would my system only make 4.9 KW?? Voltage was 25.2 when I got here with battery temp around 50 degrees.

I realize I was treading water over the weekend but I would think I would have made 8-9kw today and since I wasn't here I would have hydrometer ratings at 1.255 which is full for my newer L-16 RE B's.

Not sure, but did you read how many minutes your CC was in "float" mode? That would be my guess, as if the batteries went into float early then you wouldn't get very many KWH. Sounds like overall you are deficit cycling, which can be a downward spiral. I'd look into a secondary charging source asap. Listing all of your CC settings would be helpful too...

Derik · January 2011

Re: Controller Issues?

I have 12 feet of 4/0 welding cable going to the battery bank. I realize this is longer than what is recommended but I have no choice with my house configuration.

Yes voltage was resting voltage after several hours of darkness and a few lights on. 25.2 last night 24.6 this morning at 45 degrees and I used lights, t.v and the wood stove fan ran all night. Readings at batteries and at mate are the same.

With an abosrob time of 4 hours the system only goes into float for about the last hour of the day.

Absorb voltage is set at 29.6 float is 27.2

Remeber I just increased absorb time from 3 hours to 4 hours 3 days ago, and I was making plenty of power when I was here using it, seeing hydrometer readings going up not down & making almost 10kw of power off of 9 215 watt panels. My typical use is about 4 - 5 Kw but had guests two days and used more.

I filled the batteries once this winter so once since Sept. I just bumped up my absorb tiime from 2-3 and now 4. It has only been at 4 for a few days and was at three for only a few weeks.

Hydrometer readings this morning were 1.230 so I don't have far to go for full charge and am using very little capacity of the batteries.

My guess is that 3 days with the absorb at 4 hours wasn't enough to trickle (low amp charging) the last hour or so of absorb to fill the batteries to 100%.

I am getting them 90% full but not getting the last 10%.

Remember I can see Mexico from my house, so I don't get a lot of the losses this time of year you guys have in the North. The days are just shorter than summer but cooler so the panels are very efficient , it's 8:25 a.m. right now and I am making 1160 watts at 45 amps.

BB. · January 2011

Re: Controller Issues?

Sounds like you have everything properly setup...

Don't worry too much about that last 5-10% final charging. That takes the longest time, is when batteries "start using water", and "gassing" batteries is a mix of good and bad--Good that it mixes electrolyte, bad that is creates oxygen that causes positive grid corrosion and plate erosion over time...

Check once a month or so on your "full battery" to see that all cells are fully charged. If you have a difference of greater than 0.030 specific gravity from high to low cell, then equalized. Remember that you should measure each cell every 30-60 minutes and stop equalization once the s.g. stops rising.

Just avoid spending "lots of time" (days, weeks, etc.) below ~75% state of charge--that is when sulphation happens (sulfates crystallize and no longer are available for charge/discharge chemical reactions).

-Bill

Derik · January 2011

Re: Controller Issues?

Thanks BB, that is what I thought but needed to hear it from someone else since this is all pretty new to me. I do know that my KWH used are far less than KW I am capable of making with this system, I just wondered why it had cut down production when the batteries are not all the way full. I would guess just a few more days they will be 100% full with the sun we have had this week.

BB. · January 2011

Re: Controller Issues?

How long the batteries spend at 29.6 volts is going to determine that last 10% or so of the charging cycle.

If you have significant loads during daylight hours--it is possible that the controller is being "confused" by your loads--which may convince the charger it is actually recharging the battery bank--somewhat limiting the maximum state of charge before it flips over to float. But that would not (as I understand) cause your charge controller to cut back on kWH production.

Extending the timer and monitoring your battery bank's water level (not too much or too little usage) as well as with a hydrometer will tell you how you are doing.

If you want more data--I am a pretty big fan of Battery Monitors (Victron makes a couple nice ones too). They show you what is happening with your battery--vs the the charge controller that can only tell you what is happening with the Battery+Loads.

Outback also make an integrated battery monitor system for use with their equipment--I don't know anything about the details--but you might want to look at theirs too and see if it has any advantages for your use.

-Bill

Derik · January 2011

Re: Controller Issues?

Today I arrived here at 2:40 pm and the system was already in Float. I checked the charge controller and it had finished the absorb cycle 55 minutes prior to me getting here meaning it went into absorb about 9:45 a.m.
Which is beleivable since I have not been here since Thurs. morning and the only load is the fridge and one light. Indoors is about 55 degrees so the fridge hardly runs and the lights are only one 8 watter on a 4 hour timer and one outdoor light 8 watts as well that is on dusk to dawn. So most powe use when I am not here is phantom loads.

KW produced was 5.1 and hydrometer readings went up close to 1.255 which was about 1.248-1.250 with the temp compensation. So close to fully charged.

I have a trimetric but have yet to install it. I had to put everything in conduit for my home inspection and didn't want to open everything up again just yet. I'll post some photos but my Flex 500 is in a tight closet mounted vertical and it's a real hassle to work in there with the 4/0 cables in conduit..but mounting the trimetric is on the top of my list of things to do.

Vic · January 2011

Re: Controller Issues?

Hi Derik,

Am a bit late in reading this thread.

By the number you listed, I think that you are running Trojan batteries (?).
I was only able to find one Flooded battery manual at the Trojan site:

http://www.trojanbattery.com/pdf/TRJN0109_TRJNUsersGuide0810Lr.pdf

If your batteries are Trojan, and if the above manual covers your battery charge parameters, then, 1.277 SG is noted as 100% charged. When in Float, you need to maintain full charge. So being in Float at a compensated SG of about 1.250, you are about 85% charged.

The FM-80 CC should have included the Battery Temp Sensor (BTS or RTS). This should installed below the normal electrolyte level of one battery near the center of the pack.

Think this system was recently installed. Normally, the user chooses a "Pilot Cell", to monitor the SG of the bank. This is often the losest SG cell in the bank. L-16 batteries are considered to be tall, and it is said that tall batteries need more frequent EQuilization. The electrolyte stratifies, and an EQ helps stir it, mixing the heavier acid back into the water. In tall batteries it is more difficult to mix the acid throughout the entire colunm of electrolyte. You probably can do an EQ on a sunny day, after your bank is fully charged.

Most battery manufacturers state that at the very minimum, batteries need to reach 100% state of charge once per month. More often is better.

Is your Hydrometer a GLASS float style ?
Are you running the FM-80 BTS ?
Where you reading the charge voltage settings of the FM-80 ?
Have you checked the voltage calibration of the FM-80 with a high quality Voltmeter (DMM) ?
Have you considered getting a generator ? (OOOPPPsss a little attitude)

Am done. Good Luck, Vic

Derik · January 2011

Re: Controller Issues?

Hi Vic, yes I have a good meter and it reads the exact same voltage as the Mate. I also have the temperatue sensor in place and it seems to be working fine and reads the same as the mate. So I am in absorb at 30-30.6 volts depending on the temperature but actual temperature compensation voltage is 29.6 exactly as set.

The batteries are Trojan L-16RE B. The trojan distributor said that when these batteries are new to not expect Hydrometer readings above 1.255 until about a year of service.

I have a 40.00 dollar hydrometer glass float, temp and very good qualitiy ruubber. Having said that readings of 1.255 or 1.250 or even 1.260 are hard to tell and there is a chance of operator error. of .oo5 or so.

Oh yes the generator. I have been talking to the Kohler guy about getting a generator so I can run my ac this summer. So I will have one by summer but doubt I will ever have to use it to charge my batteries.

I started this post just after I had set Absorb to 4 hours, I have a unique sitiation here not sure if it's the altitude, cool temperatures, or abundant sun but I make way more power than I can ever use and it appears I can toast these batteries in the dead of winter.

I am now in float just a little past noon & the days are getting on minute longer every day!

I am new to this but my belief is that solar is unique to almost every mircoclimate and you can't use one rule of thumb for every situation. If I followed the advice of the some of the Canadians on this board I would have toasted my batteries ( 8 hour absorb ) already and instead of having 2000 watts of power I would have been sold 4,000 watts.. anyway my experience has been that I don't see the losses most see.

I have a cabin with solar (very small) two T-105 trojan batteries one 65 watt panel, going on 6 years of service, un insulated battery box outside, equalized one time and still running strong, charging perfectly and all cells reading within .oo3 of each other...no generator!

Having said that I will monitor the L-16s much more closely and equalize them when needed. So far that has been once since May.

I'll be up there again tomorrow and check things out again my guess is that I will be having to add water and cut the absorb back to 3 hours very soon.

Vic · January 2011

Re: Controller Issues?

Hi Derik,

Thanks for the reply.

OK fine on the Trojans. Almost all of my neighbors run one of the Trojan L-16 varieties, altho few of them seem to pay much attention to their system, until the power goes off.

Am no expert on this, but am surprised that the SG would not come up to the 100 % value until many cycles, altho batteries are not really finished until they have seem 50-100 cycles. Seems to me that this trait would make it very difficult to set charging parameters, but I am no expert on this.

Great that you have a quality Hydrometer, this is of prime importance (to me at least). It is challenging to make repeatable readings within 5 points of SG, but it is worth the effort to take 3-4 readings per cell.

Great that you have checked the system calibration. Seems (as BB stated) that you are doing things correctly.

I throw away many Kwh every sunny day, unless I am around to think of creative ways to consume the XS power ... this takes quite a lot of time !

Re Asorb time, if you can keep an eye on the SGs fairly often, then you can zero in on the correct time value. Think that the FM-80 has a setting that allows Asorb to be terminated based on the current flowing to the batteries (and, unfortunately it includes all inverter load current as well). In the MX-60 is is called End Amps. Many battery manufacturers say that batteries are fully charged when Asorb current has tapered to 1-2% of the 20 hour AH capacity. There would still be one parameter which affects this ending current -- the Asorb Voltage. But silll this is a way to try to make the asorb time variable depending upon the amount of bank discharge. But you would still need to watch the SG, in order to tune the End amps as well as the Asorb voltage.

Nice that you have a generator in your plans.

Many folks seem to pay too little to their battery banks when they are new, but become very interested in them when they are in distress, but you seem to be paying close attention to your valuable batteries. FLAs are quite tolerant to most abuses (other than exposed plates and extended time with little or no charge). Bill has many good tips, including: Watch your water useage, as it is a very good indicator of how well you have set your charge parameters.

Good Luck with the new system. Sounds like you are doing all the right things. Vic

Derik · January 2011

Re: Controller Issues?

Thanks Vic, I did have some issues and that's why I joined this site ( great resource) and started paying attention to my sg readings. It started with me realizing that my absorb time had went from two hours to one hour, thus I had some low hydrometer readings not below 50% but about 60%. Some how the system had re set itself and the internal clock on the Mate was wrong as well? I had a lot of contractors in the house and the power was being turned on and off all the time.. I then increased the absorb time to two hours and watched the the hydrometer...I was able to get the batteries back up within 4 days or so I ran an EQ cycle and then we had the CA rains ( I am sure you got pounded as well) Then I decided to set the absorb to 3 hours and watched the hydrometer, and after a few days decided to go for 4 hours. After a week of sun it looks like 3.5 or 3.0 hours may be my winter absorb setting (depending on our winter rains)

I don't live in the house all the time so my power use is little when I am not there.
Or I am sure I would have really had to conserve or have had to hook up a generator by now.

Thanks for the helpful comments.

Derik

Vic · January 2011

Re: Controller Issues?

Hi Derik,

I am still a bit troubled by this statement if one of your previous quotes,

"The batteries are Trojan L-16RE B. The trojan distributor said that when these batteries are new to not expect Hydrometer readings above 1.255 until about a year of service".

I have not seen this before with any of the FLA batteries I've encountered. I wonder is the seller of your batteries was trying to say that you would not experience 100% of rated CAPACITY before 50-100 discharge/charge cycles.

In my experience, SG readings are not really a measure of absolute capacity, but state of charge of the cell(s).

It seems to me that your bank is really reaching about 85% charge given the SG readings you have quoted, and this may not be the best thing for the bank if that is correct.

In the Trojan Battery User's Guide, a Tech Support phone number is given:
800-423-6569. I wonder if you think that it is a reasonable thought to call Trojan to see what they have to say about target SGs on a newish battery bank.

This thought has been hanging in my mind and thought that I'd try to bring it up.

Just my thoughts, Vic

Derik · January 2011

Re: Controller Issues?

The trojan site says 50-100 cycles before a new battery has full capacity, I would assume that means sg readings would be a tad low but I'll call them, to confirm.

Trojan also says in the battery guide to recharge if batteries are below 1.250. I swear I read somthing there also that said new batteries would have lower readings but I can't find it now. They recommend equalizing if batteries are lower than 1.250.

Anyway I'll call them, now we are getting so much sun that I could equalize them and watch the readings until they get up to where they need to be if 1.255 is in deed not fully charged for a newer battery bank. I was thinking about equalizing them anyway since I have only done this once but this morning I took hydromter readings on a few cells and they all were identical and at 1.235 after a night of the wood stove fan running all night and 5 hours of watcing a 52 inch LCD with two lights on. I;ll check all the cells this weekend.

It appears as if I am only using about 5% of the capacity of the batteries during the night so if 1.255 is too low for newer batteries no damage should have been done and sulfation should be at a minimum.

Vic · January 2011

Re: Controller Issues?

Hi Derik,

Thanks for the reply ... again, I really know nothing of your specific batteries, but just a thought about contacting Trojan directly.

Have fun with the new RE system.

Am off to the mountains, where there is NO internet, and reality seldom leaks in.

Good Luck, Vic

Controller Issues?

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