older system, newer batteries...

bajafshrmanbajafshrman Registered Users Posts: 8
Hello all,

I've been lurking for a bit and finally decided to post and ask a couple of questions. First, here's what I have:

8 Kyocera 120watt panels
Solar Boost 50 Charge Controller
Trace SW2512 Inverter
8 Trojan L16RE-B Batteries
Honda EU300I

The system has been in service since '98 and had a set of Rolls L16 batteries initially. I added the Trojan batteries almost two years ago (March 2012). We live in a remote pueblo in Southern Baja California which has a on-again/off-again power grid (solar/wind/generator). The Grid has it's own set of issues but it does supply power for five hours in the morning and six hours at night (7am to noon and 5pm to 11pm). I have tied the grid into the system to charge the batteries when power is available, I do not send power back. We do our very best to keep energy usage low and turn off the fridge and TV when the town power is not available.

I'll admit that I have not been monitoring these batteries as much as I should. Just started checking the hydrometer religiously in the past couple of months. When I first started checking the SG was 1.250 and I read that it should be up to 1.277. I've equalized the batteries and the highest reading I could get is 1.260 - 1.265 - they are even across the board (super good since I know I have too many strings). Then I found a small disclaimer that Trojan L16RE-B batteries manufactured before March of 2012 are at 100% SOC with a SG of 1.260 - can anyone confirm this for me?

The batteries are supposed to be stamped with a manufacture and shipping date. Mine are only stamped on the negative terminal (D2) signifying a ship date of April 2012. I'm guessing that puts me in the pre-March 2012 category since no matter what I do I can't get the SG to go up any higher.

I have more questions but I'll start here.

This forum is awesome! Thanks in advance for the help!

Oh, and Happy Holidays!

Comments

  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: older system, newer batteries...

    I'd look at this way, if your not getting any rise after 3 hours of Equalizing, then it's never going to happen. So, if for some reason you have 1% less capacity you'll never know it if your cycling them to 50% dod. Sometimes it's the fill level of the electrolyte before you start to add water. After I do a commissioning EQ, I will add the same strength electrolyte up to the known level where the fill line will be. Big batteries have such a big reserve level it is easy to get the SG ratio off by adding water. I know that the Manufacturers say Never add any, but in this case it's a wash since the original is returned to it's original strength before adding any.

    In the heat your in it could be a blessing to have it a little lower.
  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    Re: older system, newer batteries...

    Are you having an issue with loads depleting those batteries in too short a time? sounds like you are able to keep them well charged ,,,
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • bajafshrmanbajafshrman Registered Users Posts: 8
    Re: older system, newer batteries...

    I don't seem to have any trouble keeping them charged. As a matter of fact, they rarely go below 1.245. Because I get lots of help from the grid charging in the morning and at night I rarely use the batteries without either PV or grid power on. This will lead me into my next set of questions regarding absorb and float settings. I want to make sure I'm not Bulk charging too much. I'll get to that in a new thread.
  • BB.BB. Super Moderators, Administrators Posts: 29,350 admin
    Re: older system, newer batteries...

    You can keep the same thread--It sometimes helps us to review your initial issues and any configuration information you supplied earlier. These are all related questions (care and feeding of your battery bank).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bajafshrmanbajafshrman Registered Users Posts: 8
    Re: older system, newer batteries...

    Ok, I'll keep this going.

    If I am correct it is best to cycle my batteries between 60% and 100% daily?

    I can check this with my hydrometer (60% = 1.200 and 100% = 1.260)?

    Based on the SG readings I adjust the absorb time in small increments by trial and error - correct?

    If my SG is not falling below 1.245 in the morning then I have the capacity to add more load to the system at night - right?
  • BB.BB. Super Moderators, Administrators Posts: 29,350 admin
    Re: older system, newer batteries...

    I don't cut and paste many replies--But this is one:

    Dave Sparks, a poster here has related:
    I learned this strategy from Dave Surrette (Rolls) in the late 70's. Pretty much the bible on how I design my systems for off-grid.

    Assume that the system will never reach more than a 90% state of charge.
    Try not to go below 50% SOC, ever! Complete absorption over 90% of the year

    Use the energy stored from 70% to 90% SOC for your daily cycles.
    Save the energy from 50% SOC to 70% SOC for aging to get long battery life.

    I know Surettes has changed their recommendations over the years but I also know they are in the business of selling batteries! If you do the above you will get 10 to 15 years on their batteries with decent maintenance.

    ...

    Oh yea, I am really happy that Surrette and Trojan are making L16's with 1000 AH capacities @20HR. Been bugging them for many moons to do batteries less than 125LB's!

    And, my two cents... If your batteries are using a bit of distilled water per month--you are probably OK. If you are using none, or a lot per month--then you are probably under or over charging.
    • Undercharging and operating for long periods (below ~75%) is damaging to lead acid batteries.
    • Overcharging is less damaging to flooded cell batteries (at the cost of distilled water and wasted energy).
    • Overcharging sealed batteries (AGM, Gel, VRLA, etc.) can be fatal to those types (venting electrolyte).

    Don't try for 100% SOC--Just try for >90%.

    For lead acid batteries, somebody posted a chart recently (I cannot find it now) that showed (as I recall) if you cycle a battery to 80% SOC (full to 80% SOC) vs full to 30% SOC, the actual life of the (otherwise well maintained) battery will still be roughly the same (I.e., YY kWH of battery cycling till death). [add for clarity--The stored energy provide by the battery will be roughly the same for different dischage depths--HOWEVER, If you pull 60% of battery energy daily vs 20% daily, the battery will only support ~1/3rd the number of cycles--So cost efficiency is the same, but you have to replace the bank 3x more often--I.e., a 2x larger bank will last ~2x longer cycling, but cost you ~2x as much to replace--Cost is, roughly, a wash].

    Too shallow of discharging (i.e, discharging by 10% to 90% SOC)--Is not good for lead acid (and recharging to 100% every day or every few days is actually hard on batteries--lots of gassing/water usage/heat generation/shedding of plate materials/driving Oxygen gas into positive plate grid, etc.).

    Floating (standby usage) is not good for deep cycle lead acid batteries either. Discharging to 80% SOC (and even down towards 50%) SOC multiple times per month is probably optimum.

    There are two recharging patterns that are in typical use... The first is the standard daily discharge from full (>90% SOC) by 20-40% per day--And letting the solar array recharge the battery bank to >90% in the next few days. If the battery SOC looks to be heading below 50% SOC, then think about starting the genset the next morning and recharge >80% SOC (more fuel efficient for genset). If the battery bank is heading towards 20% SOC--Very possible permanent battery damage will occur).

    One poster her who has done a lot of testing recommends not to go much below ~50% SOC--Many batteries will be damaged by even this level of discharge. Get the battery bank >90% SOC several times a week.

    Another battery cycling pattern... Basically to run the batteries (daily) around 80% to 50% cycling, and recharge >90% once every 7-10 days or so (at least one battery vendor said to recharge >90% at once every 4 weeks is OK for their batteries). This allows you to run the batteries more efficiently (>90% cycle efficiency) and lessen charging damage (>90% gassing damage and excessive water usage).

    It appears (from my reading) that sulfation is worse with batteries that set at ~75% SOC with no cycling (for days/weeks/months). If your batteries are not being cycled, you need to recharge before hitting the 75% SOC level (i.e., for good condition flooded cell batteries, recharge 24 hours every ~30 days).

    Battery temperature is another "wild card". Batteries are spec'ed at 25C/77F. For every 10C (18F) increase in temperature, that cuts around 1/2 off of their aging life. For every 10C below 25C, that adds 2x to battery life (those guys in cold climates may have battery capacity impairment from sub freezing temperatures, but their batteries will last many more years).

    Anyway, here is some light reading:
    BB. wrote: »
    Add another very good Battery FAQ that is often recommended here (latest via Tony/Icarus). [I will add the three battery faqs here for one stop reading. -BB 4.7.2013]

    http://www.windsun.com/Batteries/Battery_FAQ.htm
    http://www.batteryfaq.org/
    http://batteryuniversity.com/

    -Bill

    PS: Another interesting Battery FAQ with "gassing voltages" and how to charge Sealed Lead Acid Batteries first posted by mike90045 and Solar Guppy:

    www.powerstream.com/SLA.htm

    In this next link, is an older bulletin from Rolls (you have to click on this link to see the attachment) on how best to recharge deep cycle batteries. And here is the (text version) of the document. (thank you member "Volvo Farmer")

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: older system, newer batteries...

    I'd second about everything Bill has said about your SOC cycling. One thing I'd do is make up a chart of soc of your batteries Voltage vs the SG level. It might be easier to use on a daily basis. Voltage is not a good indicator unless it's correlated to battery health and known values. When you asked 1.245 SG level , if you know the voltage it just makes life easier and loading decisions in a snap.

    Another thing I do is to shuffle the position of the batteries in your bank once a year. 12 Volt banks tend to be harder on the first two batteries on the positive end. I number mine and move them around and clean all the connections at least once a year.
  • bajafshrmanbajafshrman Registered Users Posts: 8
    Re: older system, newer batteries...

    So, the short answer seems be that I think I'm cycling often enough but probably not deep enough. Hope I haven't shortened the life of the batteries but since I can't change it now I won't worry about it.

    I'm going to leave the fridge on at night and see where I'm at in the morning. Since the grid is on till 11pm and it fires back up at 7am the only thing on will be the fridge.

    I'll post tomorrow with results.
  • bajafshrmanbajafshrman Registered Users Posts: 8
    Re: older system, newer batteries...

    ok, another issue...

    Since the power comes on and off the charge cycle is going twice a day (bulk/absorb/float). Is that ok or should I change something?
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: older system, newer batteries...
    Since the power comes on and off the charge cycle is going twice a day (bulk/absorb/float). Is that ok or should I change something?

    Since your cycles are so shallow, I suggest that you charge the batteries once every 2nd or 3rd day (or whenever the SOC gets down to 60-70%).

    BB. suggested a few charging strategies. Another approach is to lower your absorb voltage for daily charging and once a week do an equalization. The lower absorb voltage is easier on the batteries, and any charging deficiencies that result from it are corrected with the weekly equalization.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • SurfpathSurfpath Solar Expert Posts: 392 ✭✭✭
    Re: older system, newer batteries...
    Hello all,
    When I first started checking the SG was 1.250 and I read that it should be up to 1.277. I've equalized the batteries and the highest reading I could get is 1.260 - 1.265...Then I found a small disclaimer that Trojan L16RE-B batteries manufactured before March of 2012 are at 100% SOC with a SG of 1.260 - can anyone confirm this for me?

    The batteries are supposed to be stamped with a manufacture and shipping date. Mine are only stamped on the negative terminal (D2) signifying a ship date of April 2012. I'm guessing that puts me in the pre-March 2012 category since no matter what I do I can't get the SG to go up any higher.

    Greetings Bajafishrman,
    The stamp on the negative terminal is the manufacture date, not the ship date*. So your D2's were manufactured in April 2012, ie. a month after the switch to 1.280 (or 1.277 if you speak to a Trojan Tech - don't ask me why).

    My gut feeling in your case is that I would not worry too much about only getting 1.265 after EQ. As others have said or hinted, if you commissioned your batteries properly and you maintain a charging profile from ~90% (charged) to a discharge limit of greater than 50% - with a periodic (each 2-4 weeks) EQ to around 100%, I am pretty sure you will be OK. Keep your batteries as cool as possible.

    I also have Trojan L16REB's with a year on them (my manuf date stamp is Dec '12). I do regularly get to 1.275 when I perform that periodic EQ, but I got this value upon commissioning. I have been recently monitoring my water use, and so far use about 1 liter a month across all 8 batteries. Not quite sure of this is too much. Perhaps I need to reduce absorb voltage or absorb time a little.

    Like many REB users my absorb voltage is slightly above what Trojan recommends (I think it's 59.4V now), and I absorb for about 3-4 hours on average a day. I usually always go to float each day for an hour or two.

    Hope that helps with your batteries.
    Cheers,
    SP
    *per the Trojan RE web site:
    " Trojan changed SG values of the Premium Line in March 2012 to avoid confusion over correct SG values for the Premium Line compared to the Signature Line however this change does not have any impact on life cycle performance. Trojan Premium Line batteries manufactured prior to March, 2012 have nominal S.G. of 1.260 while those produced after March 2012 have nominal S.G. of 1.280 [at 80 degrees f]. To determine the date of manufacture, refer to the date code on the negative terminal which consists of a letter and a number. The letter refers to the month and the number refers to the year. A2 = January 2012, B2 = February 2012 and C2 = March 2012 etc."
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • bajafshrmanbajafshrman Registered Users Posts: 8
    Re: older system, newer batteries...

    Thanks to everyone for all the great advice. For now, I've done two things:

    - decrease absorb rate and duration

    - increase load

    I want to get the batteries into a better cycle so leaving the fridge on all night - so far, so good. Since I have solid charging capabilities (grid 7am to noon/ PV array noon to 5pm/ grid 5pm to 11pm) I'm comfortable lowering the absorb time and rate. I'll monitor daily until I get it to a good charging cycle (60% to 90%).

    Next plan is to get a better charge controller so I can manage the charging cycle - I don't like it that it goes through all three stages twice daily.

    Happy Holidays!
  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    Re: older system, newer batteries...

    I don't recall if the MN Classic was mentioned already, but a new feature the Classic line has is to skip the Bulk phase of the charge cycle for a day or more (ie set # days to skip). It sounds like it is just what you are after. 8)
    http://www.midnitesolar.com/documents.php?productCat_ID=21&productCatName=Charge%20Controllers%20-%20Classics&model=CLASSIC%20150&product_ID=256&act=info
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • bajafshrmanbajafshrman Registered Users Posts: 8
    Re: older system, newer batteries...

    Two things that are a bit confusing;

    - First, there is only one stamp on the battery on the negative post - D2. But, I purchased the batteries in March of 2012 (I have the receipt). I'm going to assume that they were mis-stamped and consider them manufactured before March of 2012 with a SG at 100% SOC of 1.260.

    - Second, the SG never seems to fluctuate much. They are consistent across the board at 1.250/1.255 almost all the time regardless of how much load I put on them. I have two hydrometers and they read the same. I monitor other batteries as well and I get different readings so it seems they are both working correctly.

    Should I take the charge off the batteries to see if they will discharge?
  • BB.BB. Super Moderators, Administrators Posts: 29,350 admin
    Re: older system, newer batteries...

    Just to be clear--Loads themselves do not affect Specific Gravity--It is Load*Time that discharges the battery bank and reduces your specific gravity.

    If you cycle the battery bank very shallowly (most of your loads are during the day, use mostly for backup power, etc.), then you will not see much change in the specific gravity.

    If you have a need for battery power (say two days without sun)--Then you should try running the system two days without sun (no generator, grid, solar use) and see if the system (and your loads) will meet your needs.

    You don't want to find out your system fails in the middle of an emergency.

    Note, that you need to look at your loads and battery bank capabilities--Ideally you don't want to discharge below ~50% of the battery bank capacity very often--And you don't want to discharge below 20% capacity. You will risk permanently damaging your battery bank.

    Looking at your bank AH capacity, your average loads, and monitoring the specific gravity will all help you ensure the bank is working properly... Of course, the next test is how well your charging solution (solar panels, charge controller, AC Backup, Generator Backup) all work to bring your bank back full.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: older system, newer batteries...
    Two things that are a bit confusing;

    - First, there is only one stamp on the battery on the negative post - D2. But, I purchased the batteries in March of 2012 (I have the receipt). I'm going to assume that they were mis-stamped and consider them manufactured before March of 2012 with a SG at 100% SOC of 1.260.

    - Second, the SG never seems to fluctuate much. They are consistent across the board at 1.250/1.255 almost all the time regardless of how much load I put on them. I have two hydrometers and they read the same. I monitor other batteries as well and I get different readings so it seems they are both working correctly.

    Should I take the charge off the batteries to see if they will discharge?
    Someone had posted in here before that there is a 90 day offset in the dates stamped on some Manufactures batteries, I never thought about it before , but I was picking up a couple batteries last week. I had been waiting for some fresh ones that they had ordered, they were marked M3. If the 90 day offset is correct, that would make them October of 2013, but they could have been made in August.

    The SG's won't change based on load, it would show the SOC overtime as the ratio in the electrolyte changes.
  • bajafshrmanbajafshrman Registered Users Posts: 8
    Re: older system, newer batteries...

    Again, thanks for all the help.

    I understand the SG won't change just because there is a load on the system. But, I thought I would see some difference over night since there's no charge but the system is under load for eight or nine hours.

    If I understand correctly, the batteries should cycle between 50% and 90% daily. That would be a SG of 1.200 and 1.260 respectively. If I'm not drawing enough power to drain them daily then perhaps I should decrease the absorb voltage and time so they go down slowly over a two or three day period and then increase the absorb rate to bring them back up - essentially just creating a longer charge cycle.

    Any danger in this strategy?

    I think my load vs capacity is pretty good. We don't have very many long cloudy spells and I have the grid and my generator to boost the system back up if I need them. But, that's sound advice, Bill - I'm going to turn the solar and grid off to see how long I can go. That will give me a chance to see how long it takes to bring the batteries down to 50% to 60%.
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