More Surrette problems

1235»

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: More Surrette problems

    Terry,

    From reading the other thread on the Outback forum, this has me a bit worried:
    Our solar usage pattern is in flux, as we've been trying varying charging voltages and frequencies as we've tried to figure out our charging problems. But in general, we run the genset when SOC drops to 55% until it hits 75%. This may be every second day in December. In addition we'll run the genset as long as needed to ensure we reach float (3 hrs absorbing) at least once a week year-round. We equalize every month in winter and every 3 months in summer (e.., Jan, Feb, Mar, Jun, Sep, Nov, Dec. Because of our genset's low output (45 A), we always try to do a solar EQ, which means bulk-charging and absorbing by gen in winter.

    But, assuming that the battery bank is still getting above 90% state of charge at least several times a week during winter--It should be OK. Don't want to see the bank spend too much time below 75% state of charge (sulfation worries).

    Your charging/load information sure seems to indicate that you have more than enough charging going on during the summer (and the new bank is mostly summer experience right now?)... But the symptoms sure read like deficit charging.

    Have you tried a DC Current Clamp meter (like this one from US Sears) to verify overall charging current to battery bank and that each string is getting roughly equal charging current? And I assume battery voltages reasonably match the Outback charge controller voltage readings with an independent meter?

    Do you have a battery monitor?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • pedro65
    pedro65 Registered Users Posts: 21
    Re: More Surrette problems

    Just installed 16 S 530's in my bank. Manufacture date within the last 60 days. It has been a real experience watching the charge profile on this bank compared to my completely sulfated bank that I inherited from the original owner.

    They showed up with SG around 1.235-1.240. Charged quite a bit got them up to 1.250 in the first two days. At 58V I was getting into float at about 4 amps. I will be checking back in a week or so and expect to see SG's at the nominal 1.265.

    I'll report back when I get another look at the bank in a week.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: More Surrette problems

    Thanks again guys for all the new info and posts. Overall, what I'm seeing is easing my fears of Surrettes. Sounds like they're working hard at resolving the issues and hopefully getting back on track. I continue to read and appreciate every post in this thread.
  • terrynew
    terrynew Solar Expert Posts: 48 ✭✭
    Re: More Surrette problems

    Good questions, Vic. Yes, my Magnum inverter has a BMK that calculates an SOC, and Magnus's user guide and tech support recommend using this over voltage as the best indicator of when to recharge by genset. But some Outback forum'ers dont trust such tools and go by specific gravities instead. Do you agree, and if so what gravities would you use as 50% and 75% threshold indicators?

    I don't own a clamp-on ammeter (the Sears one you linked to isn't shippable to Canada, the site says). But a neighbour lent me his a few months ago ad we confirmed the current at the battery end matched the FM80's display. I'll borrow it again, though, to check that each string is getting roughly equal charging current.

    Are you in agreement with those who say I should consistently be getting a bulk charging current over 40 A? I only reach that one out of every three days. Yesterday, for example, I got six hours of absorb but the peak current (during early bulking) was 33 A. Is this an indicator of reduced charging?

    Thanks,
    ...Terry
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: More Surrette problems
    terrynew wrote: »
    Are you in agreement with those who say I should consistently be getting a bulk charging current over 40 A? I only reach that one out of every three days. Yesterday, for example, I got six hours of absorb but the peak current (during early bulking) was 33 A. Is this an indicator of reduced charging?

    Hi Terry, unfortunately this forum has a habit of focussing on peak current during bulk. At best it's a crude and only indirect indication of whether your system is in balance or not.

    If you're getting 6 hours in absorb, then I'd say your batteries are charging fine, assuming that:
    a) your absorb voltage is correct
    b) they're actually staying in absorb all that time, and aren't dropping down into bulk because of too high loads

    Surrette only mention minimum charge currents once in their manual: 5% of AH when doing an Equalisation charge. You're well above that, and you're not even doing an EQ charge.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: More Surrette problems
    terrynew wrote: »

    I don't own a clamp-on ammeter (the Sears one you linked to isn't shippable to Canada, the site says).

    Oh, Guess I was lucky. Ordered one online last year and it arrived here in Nova Scotia safe and sound, no problems at all. Something must have changed :(
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: More Surrette problems
    stephendv wrote: »
    Hi Terry, unfortunately this forum has a habit of focussing on peak current during bulk. At best it's a crude and only indirect indication of whether your system is in balance or not.

    If you're getting 6 hours in absorb, then I'd say your batteries are charging fine, assuming that:
    a) your absorb voltage is correct
    b) they're actually staying in absorb all that time, and aren't dropping down into bulk because of too high loads

    Surrette only mention minimum charge currents once in their manual: 5% of AH when doing an Equalisation charge. You're well above that, and you're not even doing an EQ charge.

    I've also found that of interest, seeing as my roughly 1000 AH hr battery pack of six, L-16's, now over 10 years old and for several years, were charged by only 600 watts PV. I just made sure I didn't run them down too low for the PV to bring them back up in the next couple of days. Made sure they were back up on both SG and voltage a couple of times a wk.
    But mine are not Surrette, so perhaps that makes a difference. On the other hand, an L-16 should within reason, pretty much be an L-16, regardless of who made them???
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: More Surrette problems
    On the other hand, an L-16 should within reason, pretty much be an L-16, regardless of who made them???

    My understanding is that L16 refers primarily to the size, to allow interchangeability in a holder. Although it seems that the L16 form factor is used primarily for deep cycle and RE batteries there is nothing about being an L16 that automatically leads to similar internal design and construction. And the factor of quality of construction is not covered at all except by competition for the market.
    SMA SB 3000, old BP panels.
  • terrynew
    terrynew Solar Expert Posts: 48 ✭✭
    Re: More Surrette problems

    You're right, Wayne. I checked the Sears site again, and today it's letting me buy the ammeter. I should get it in a week or two. Thanks for the link, Vic.
    ...Terry
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: More Surrette problems

    Hi Terry thanks for returning to help update this Thread RE Surrette, and your situation. Thanks to Pedro64 , and others for additional updates.

    Terry, great that you were able to buy the Sears CO DC Ammeter.

    Tired to briefly address this in the OB Thread; The 45 Amp breaker on your 10 Kw genset seems just right to me, because 240 VAC times 45 A = 10.8 KW. I would be surprised if your Magnum 120/240 VAC Inverter would not be able to use both legs of the 240 as an AC charging source. Do not have the time to delve into the manual. But one way of looking at this is that your PV array would be considered as being able to produce a bit over 2000 watts. The genset should be able to produce about 8 Kw or more continuously into the Magnum. One limitation for your system is the Magnum's 60 Amp DC Max charge rate. Not bad, and still about equal to 3 KW+.

    Heat wave continues here, am trying to manage battery charge and A/C ... an uncomfortable set of tradeoffs. Good Luck, Vic

    Very glad that you were able to get the new 6 hour Abs time done today.
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: More Surrette problems

    ... More,

    Thanks BB Bill for providing the link to the Sears CO DC Ammeter. Had mentioned it in the OB thread, but did not provide specific info.

    Terry, I'm with stephendv on the max charge rate. IMHO, it is good to have the CAPABILITY of providing about 10% of 20 hr capacity max charge rate, but this need not all be from solar. On a good sunny day the PV and genset, together could provide more than this, altho, perhaps not on too many Winter days. In a perfect world, you might wish for more DC charge current from the genset, but this is not inexpensive!

    Terry mentioned elsewhere that his Abs voltage is 59.2 V, IIRC, a bit hot, but should be fine untiil he gets the SGs up on a daily basis.

    There are many variables that dictate the maximum current from the PVs. Believe that the OB FM CC reports the max current seen at any point during the day. An interesting number, but not particularly significant, in my opinion.

    Regarding SG values that drive genset charging; Perhaps you should use nominal SG values that correspond to what you felt the voltage values represented. I would not use an SG that represented 50% SOC -- seems a bit too low to me. You might want to run the generator at a point somewhat above this value.

    Regarding selecting the Pilot Cell, Most often this is selected from among the low SG Cells found after comissioning the bank. Often it is the cell with the lowest SG. It has been recommended that the Pilot Cell be changed every year. I used to try to get my Pilot to 1.265 on every recharge, but have moderated a bit on that recently -- new target is bout 1.258- 1.260.

    Good Luck, thanks for the added info here, Terry. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • pedro65
    pedro65 Registered Users Posts: 21
    Re: More Surrette problems

    Two weeks into my new bank, sg now running 1.260. Hasn't been cycling much as it is a vacation house. Also, monsoon season in the southwest. Getting 300 minutes of float a day......Next time I'm up there will be doing a real EQ as well. No complaints about the Surrettes though.
  • terrynew
    terrynew Solar Expert Posts: 48 ✭✭
    Re: More Surrette problems

    Hi, everyone. Here are the results of doubling my absorb time to bring my new batteries up to specific gravities near 1265. In the last 14 days, I've had 8 days with 6 hrs in absorb at 59.2 V, and four other days with over 5 hrs in absorb. So I was expecting some good news when I took out my refractometer last night and sampled four cells that were the lowest ones after my last EQ, July 11. But no, all 4 pilots had gone down (to 1235, 1235, 1240, 1240). As well, my 'good' pilot, which was 1250 after last month's EQ, was also down (1245).

    Should I just keep on truckin', or do an EQ, or is this lack of progress indicative of faulty charging hardware? Over those same 14 days, the FM80 logged a max current over 40 A on only 5 of the days (but was over 35 A on all but 2 of the 14 days).

    On the side, I've discovered thru several calls to Magnum Tech Support and Outback Tech Support that the Total Ah Out meter on my inverter's BMK does *not* represent my total load, as I had assumed; this is because a single shunt is used for both the inverter and the cc in order for the BMK to calculate its SOC. And so my load may be over twice what I thought it was, 125 Ah/d instead of 58 Ah/d. I wish there was a reliable way to measure the actual load.

    In any case, that doesn't explain why the extra absorbing failed to bring up the gravities.

    But wait, there's a new development: my DC ammeter arrived in the mail, and following Bill's request I compared the cc's output current to the actual cables going into the battery box. When the cc said 27.7 A, the ammeter read 23.9 (pos. cable) and 23.4 (neg. cable). Should I do something about this 15% drop? Is the diff between the pos and neg cables significant?

    More importantly, Bill also asked me to confirm that my two strings of 8 batteries each were getting equal current. They aren't! When the cc said 24.4 A, the cable between the first two batteries in each string measured 11.3 A and 6.7 A. Similarly, a few minutes later, the cable between the last two batteries in each string measured 10.1 A and 5.0 A. Whoa, what could be halving the current in one string?

    So I checked all the voltages. (This is at 10 am, full sun, just starting to absorb.) The 16 batteries ranged from 6.92 V to 7.76 V, with most at about 7.4 V on both strings. No difference between the strings, except that min and max were both on the string with the low current.

    Any idea where I go from here, please?
    Thanks,
    ...Terry
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: More Surrette problems
    terrynew wrote: »
    But wait, there's a new development: my DC ammeter arrived in the mail, and following Bill's request I compared the cc's output current to the actual cables going into the battery box. When the cc said 27.7 A, the ammeter read 23.9 (pos. cable) and 23.4 (neg. cable). Should I do something about this 15% drop? Is the diff between the pos and neg cables significant?

    The difference represents the load. Nothing to worry about.
    terrynew wrote: »
    More importantly, Bill also asked me to confirm that my two strings of 8 batteries each were getting equal current. They aren't! When the cc said 24.4 A, the cable between the first two batteries in each string measured 11.3 A and 6.7 A. Similarly, a few minutes later, the cable between the last two batteries in each string measured 10.1 A and 5.0 A. Whoa, what could be halving the current in one string?

    Two choices... either the batteries in one string are electrically unequal to the batteries in the other string or the connections in one string are different than the other string. If its the latter you should be able to find the bad connection(s) with a volt meter, but you need to have a brisk current flow (either charge or discharge) while you are measuring voltage.

    I recommend that you disconnect one string and charge the other. Check your SG and equalize if necessary.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: More Surrette problems

    A. "Should I do something about this 15% drop?"
    B. "Is the diff between the pos and neg cables significant?"
    vtmaps wrote: »
    The difference represents the load. Nothing to worry about.

    That answers A.
    For B: No, it is not significant and is probably explained by meter zeroing issues between the two cable locations. If you could fit both cables in the clamp together, you should read zero amps net.
    SMA SB 3000, old BP panels.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: More Surrette problems

    Hi Terry,
    terrynew wrote: »
    Hi, everyone. Here are the results of doubling my absorb time to bring my new batteries up to specific gravities near 1265. In the last 14 days, I've had 8 days with 6 hrs in absorb at 59.2 V, and four other days with over 5 hrs in absorb. So I was expecting some good news when I took out my refractometer last night and sampled four cells that were the lowest ones after my last EQ, July 11. But no, all 4 pilots had gone down (to 1235, 1235, 1240, 1240). As well, my 'good' pilot, which was 1250 after last month's EQ, was also down (1245).

    Remember that equalization brings low cells back up to high cells (in theory). So, you really need to measure all cells and look for a the SG spread. I have seen 0.015 to 0.030 SG differences listed as "significant" and suggesting an equalization to restore "balance' (the range is from different battery mfg--I would say that if your batteries are outside that range, then you have "significant" state of charge differences.
    Should I just keep on truckin', or do an EQ, or is this lack of progress indicative of faulty charging hardware? Over those same 14 days, the FM80 logged a max current over 40 A on only 5 of the days (but was over 35 A on all but 2 of the 14 days).

    Can you put your battery bank AH and voltage in your signature--I assume 48 volt system?
    On the side, I've discovered thru several calls to Magnum Tech Support and Outback Tech Support that the Total Ah Out meter on my inverter's BMK does *not* represent my total load, as I had assumed; this is because a single shunt is used for both the inverter and the cc in order for the BMK to calculate its SOC. And so my load may be over twice what I thought it was, 125 Ah/d instead of 58 Ah/d. I wish there was a reliable way to measure the actual load.

    There are different points in the system where you can measure current flow/Amp*Hours/etc... They are all valid from their point of views (charge controller, inverter, DC loads, battery bank, etc.).

    Personally, I push for the battery monitor (or Victron) to MONITOR THE BATTERY. That is, for most people, the most important indicator. Keep the battery happy, hopefully you will have a long battery life. If the battery is "not happy", it will commit suicide (or perhaps be murdered). :p

    Normally the shunt to measure battery current goes from the battery bank negative common point, to the battery shunt, to the negative/ground/common bus where all return/negative wires should be attached (if you connect a return to between battery negative and shunt, that current flow "will be missed" by the battery shunt).
    In any case, that doesn't explain why the extra absorbing failed to bring up the gravities.

    How many parallel strings do you have (if any)? (I see 2 strings of 8 batteries below--I think your sig is not correct now with 8x batteries 400 AH @ 48 volt battery bank?)
    ...When the cc said 27.7 A, the ammeter read 23.9 (pos. cable) and 23.4 (neg. cable). Should I do something about this 15% drop? Is the diff between the pos and neg cables significant?

    If you only have two wires (+ and -) going to the battery bank, and no others--My guesses:
    • It is difficult to have accuracies better than around 5-10% per measurement. Especially if the measurements are made at different times (measure wire A, then measure wire B). 15% error in measurement is getting close to being "significant"--But if you have no other wires to the battery bank, then it has to be measurement errors.
    • You can place both the + and - leads in the current clamp, and then measure the "sum of the current" which should be zero.
    • Also, make sure you have the ZERO Button setup correctly. As near as I can understand--A) with no wires in clamp, push zero button until "ZERO" is displayed on the LCD meter. Then B) connect the clamp and make measurement. If "ZERO" is not on, then you have the unzeroed bias of the magnetic sensor. To rezero meter--move wires from clamp, push zero button to turn off "ZERO", then push button to turn on "ZERO" again. Then make measurements (depending on your needed accuracy, you may need to rezero every couple minutes, or even more often).
    More importantly, Bill also asked me to confirm that my two strings of 8 batteries each were getting equal current. They aren't! When the cc said 24.4 A, the cable between the first two batteries in each string measured 11.3 A and 6.7 A. Similarly, a few minutes later, the cable between the last two batteries in each string measured 10.1 A and 5.0 A. Whoa, what could be halving the current in one string?

    You cannot half the current in one string (10 amps in, 5 amps out)... That has to be variation over time or measurement error. (I played with my car's electrical system because it was "easy" to setup steady state test conditions--I.e., headlights on with motor off. Start car, measure battery current with alternator running, lights on/off, etc. It is possible that the DC Clamp is picking up stray magnetic fields, but it should not be that much error (try taking a measurement, then flipping meter 180 degrees so the current flows "backwards" through the clamp--should be about the same with just a +/- sign change on the meter).
    So I checked all the voltages. (This is at 10 am, full sun, just starting to absorb.) The 16 batteries ranged from 6.92 V to 7.76 V, with most at about 7.4 V on both strings. No difference between the strings, except that min and max were both on the string with the low current.

    Almost a 1 volt different between batteries in a bank is significant. Could be the low voltage battery has low SG and needs more charging. It also could be the high voltage battery is fully charged (high SG) or even a high resistance cell.

    To a degree, you can isolate the problem by measuring voltage at night with significant loads--And see if the low voltage or high voltage battery has a "voltage collapse".

    And check the voltage drop across cables/connections (looking for bad/dirty/loose connections under heavy current).

    Also, measure the difference in current between the two strings (under heavy charge and heavy discharge). 10-20% difference is probably normal, and may even change over time (as the bank charges/discharge).

    Differences of a factor of 2x--Pretty close to being significant and needing to look for bad electrical connections, bad cells, etc... A factor of 10x difference in current means something is broken in the bank (during charging, a shorted cell can make that string take all the charging current; an open cell can stop current flow, etc.).

    So, log the SG, voltage, and current flow (i.e., 10 amps charging, 20 amps discharging, etc.):

    String/Batt/Cell / SG / Volts / charging or discharging:
    A/1/1 1.265sg 7.20 volts / charging 10 amps
    A/1/2 1.200sg
    A/1/3 1.260sg

    A/2/1 1.245 6.95 volts
    ....
    B/1/1 1.100 6.00 volts / charging 30 amps
    ...

    If you have a 48 volt @ 800 AH battery bank, your estimated maximum charing current is around 41 amps:
    • 18 * 175 watts * 0.77 * 1/59 volts = 41.1 amps typical maximum current in good weather

    Which is about 5% rate of charge--You can easily add more panels for 10-13% rate of charge (if your loads require it, and your wallet allows it :cry:).

    If you charge during the day and discharge at night--you should be OK. If you have significant loads during the day, it will reduce the average charging current to the battery bank--which can be an issue (leading to deficit charging).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dill
    Dill Solar Expert Posts: 170 ✭✭
    Re: More Surrette problems

    sounds like another good real world test showing why not to run parallel battery banks.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: More Surrette problems
    BB. wrote: »
    How many parallel strings do you have (if any)? (I see 2 strings of 8 batteries below--I think your sig is not correct now with 8x batteries 400 AH @ 48 volt battery bank?)

    You cannot half the current in one string (10 amps in, 5 amps out)... That has to be variation over time or measurement error. (I played with my car's electrical system because it was "easy" to setup steady state test conditions--I.e., headlights on with motor off. Start car, measure battery current with alternator running, lights on/off, etc. It is possible that the DC Clamp is picking up stray magnetic fields, but it should not be that much error (try taking a measurement, then flipping meter 180 degrees so the current flows "backwards" through the clamp--should be about the same with just a +/- sign change on the meter).

    I think that the OP was referring to comparing the plus leads of the two battery strings. (Which are probably two series strings of 4 12 volt each?)
    I would call that big a difference a problem with respect to battery life and health. Especially when the string with the lower amperage was the one with the biggest cell-to-cell voltage difference.
    SMA SB 3000, old BP panels.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: More Surrette problems

    Sounds like another $5,000 set of batteries in a death spiral. Time for some 911 on them. Don't know what equipment you have. You have to equalize them until you get the SG's up to where they need to be. You have to control the temperatures. Break them up into size groups you can do. Check the SG's every 30 Minutes and temperatures, stay below 120 . When they all get to 1.260 - 1.265 your there. Don't be surprised if it takes 8 -10 hours or more. As long as they are rising and the temperatures are ok, they will be fine. You have to keep the Temperatures down otherwise you'll warp all the plates and destroy them. You can't let batteries get into the situation you in, trying to reverse it is painful.

    If all else fails, call Surrette.
  • terrynew
    terrynew Solar Expert Posts: 48 ✭✭
    Re: More Surrette problems

    Thanks for the feedback, everyone. Sorry about the signature, Bill -- it's accurate now. Yes, it's a 48 V system of two strings of 8 six-volt batteries.

    Inetdog is right, I'm worried by one of the two strings having a much lower current than the other. But thanks to Bill's tip on using the Zero button properly on the ammeter, today I'm getting readings that aren't as different between the two strings as yesterday's were: With the ammeter on the cable between the first two batteries of String A (A1-A2), I get 7.07 A. In comparison, the current between the first two batteries of B string (B1-B2) is 9.57 A. I get the same two currents placing the ammeter between the last two batteries of each string: A7-A8 = 7.06 A, B7-B8 = 9.53 A. This is when the CC's output current is displayed as 21.4 A.

    I get no difference in readings when reversing the ammeter on the cables. And with the ammeter looped over both the + and - cables entering the battery box, I get 1.08 A rather than 0 A, but the ammeter loop couldn't close completely due to the cable thickness (there's a 1/4" gap in the 'claw').

    Is this 25% difference in current between the two strings more than a sign of the need to equalize? Since no one battery is more than a half-volt off the average, I figure the problem must be one or more batteries with high resistance. So I could equalize as is, or disconnect one string at a time and equalize each separately, or disconnect one string at a time and absorb for 6 hrs daily, or disconnect all batteries in the low-current string to see if any one has a super-high resistance causing the problem (in which case I could separately use a plug-in charger at a neighbour's on that one for 24 hrs at 15 A).

    Yikes, you're asking for a lot of testing, Bill. Can I do the voltage measurements with cables connected? When you ask for the stats at both heavy charging and discharging times, do you mean during bulk charge for the former and at night with a heavy load (e.g., toaster oven) for the latter? Should I equalize before all this?

    Blackcherry04, thanks for the charging advice. At least I don't need to worry about the charging temperature going too high, as the FM80 shuts off charging automatically when the battery temp is over 120 F.

    ...Terry
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: More Surrette problems

    Terry, I'd not be counting on a charge controller to do the kind of Equalizing you need on the batteries. I'd break them down into two strings of 8 and use one string with the panels and controller. I'd get the other 8 on the generator and a charger capable of equalizing. You don't need a lot of AMP's , but you do need Voltage ( 62 V +/- ).

    I think you might be kidding yourself if you think you can manage them with the controller alone in parallel . Maybe over time you can , but they will continue to decline if your not careful.

    The best and cheapest way I have found is to get a IOTA charger and open them and crank the voltage up to Equalize voltage with the pot inside. You can go one step farther by running them through a PWM charge controller if you want to use them for day to day 3 stage charging.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: More Surrette problems
    terrynew wrote: »
    Inetdog is right, I'm worried by one of the two strings having a much lower current than the other. But thanks to Bill's tip on using the Zero button properly on the ammeter, today I'm getting readings that aren't as different between the two strings as yesterday's were: With the ammeter on the cable between the first two batteries of String A (A1-A2), I get 7.07 A. In comparison, the current between the first two batteries of B string (B1-B2) is 9.57 A. I get the same two currents placing the ammeter between the last two batteries of each string: A7-A8 = 7.06 A, B7-B8 = 9.53 A. This is when the CC's output current is displayed as 21.4 A.

    That "zero button" just does not make sense on the meter--does it. You have to turn on the "zero mode" to zero the meter then make the measurements (with zero mode on). Every other meter I have used, you just push the button (or adjust a knob) to zero the meter. Perhaps in AC mode (which I have not used) the Zero Mode Off makes sense. :confused:

    Yea--that is "close enough" for government work.
    I get no difference in readings when reversing the ammeter on the cables. And with the ammeter looped over both the + and - cables entering the battery box, I get 1.08 A rather than 0 A, but the ammeter loop couldn't close completely due to the cable thickness (there's a 1/4" gap in the 'claw').

    Yea--the gap is a problem.

    Do you have only two battery wires (+/-) from the battery bank? Or do you have other wires (such as a ground wire that leads off to a ground rod/system ground?).
    Is this 25% difference in current between the two strings more than a sign of the need to equalize? Since no one battery is more than a half-volt off the average, I figure the problem must be one or more batteries with high resistance.

    By itself--probably not something to have a heart attack about.
    So I could equalize as is, or disconnect one string at a time and equalize each separately, or disconnect one string at a time and absorb for 6 hrs daily, or disconnect all batteries in the low-current string to see if any one has a super-high resistance causing the problem (in which case I could separately use a plug-in charger at a neighbour's on that one for 24 hrs at 15 A).

    So far, I see two things that cause me concern.

    First, the large voltage difference between batteries (6.92 V to 7.76 V)... that is too much and would indicate either a Specific Gravity miss-match (and require equalization) or "unhealthy" batteries (open/shorted cells, sulfation, etc.). Or possibly poor/dirty electrical connections (measure voltage drop across wires/connection points with meter set to 2 volt or 200 mV full scale).

    The second--Your array size appears be undersized (2,580 watt array):
    • 12*215 Watts * 0.77 panel+charger derating * 1/59 volt battery charging = 33.7 amps in full sun/middle of day typical charing current.

    We recommend a 5-13% rate of charge, which for your 800 AH battery bank would be:
    • 800 AH * 59 volts charging * 1/0.77 panel+charger derating * 0.05 rate of charge = 3,065 Watt array minimum
    • 800 AH * 59 volts charging * 1/0.77 panel+charger derating * 0.10 rate of charge = 6,130 Watt array nominal
    • 800 AH * 59 volts charging * 1/0.77 panel+charger derating * 0.13 rate of charge = 7,969 Watt array "cost effective" maximum

    And, what is the maximum current you are seeing from your array (and at what bank voltage). Your array sounds like it may be under performing. You can use your new DC clamp meter to measure the current in each of string of your array and make sure that all is OK there (solar panels, unlike batteries, current share very nicely and each string should be pretty close to the other--around 10% maximum difference).
    Yikes, you're asking for a lot of testing, Bill. Can I do the voltage measurements with cables connected? When you ask for the stats at both heavy charging and discharging times, do you mean during bulk charge for the former and at night with a heavy load (e.g., toaster oven) for the latter? Should I equalize before all this?

    Yes, the cables are connected for load testing (this will make a "problem" measuring the resting voltage as one string could be charging/discharging the other--but you have larger problems than resting voltage at this time).

    And yes that is a lot of measurements. Trying to figure out if you have a "bad cell" causing your voltage variations or simply needing equalization (battery voltage is related to both current flow in/out and SG in a good cell).

    If the batteries started out with miss-matched state of charge (i.e., one battery at 95% and another in the series string was at 75% SOC, then you have a lot of initial equalization to take care of).

    Another option would be to get a 6 volt battery charger and "manually equalize" the low cells (with a smaller genset to save fuel and be a bit easier on the other series connected cells.). You have to be careful because you will be doing this with a "hot" battery bank and you will have between 0 to 48 volts DC with respect to ground on those battery charger leads (the leads should be electrically isolated from the generator/AC grounds--but I always am careful with unknown, new to me, equipment).

    -Bill

    PS: As BC04 suggests... Do the equalization with only one string at a time--That will better match your current to the bank size and force the charging current through one string instead of worring about it being "diverted" to the other string.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • terrynew
    terrynew Solar Expert Posts: 48 ✭✭
    Re: More Surrette problems

    Thanks for all that info, BB and BC04. But oh man this is all so overwhelming to someone who was promised plug-and-play. I'm sooo close to throwing in the towel and going on-grid instead of buying more panels and fighting the next problem. But okay, one more kick at the can: I'll eq the two strings separately, and I'll climb the roof to measure the separate panel currents, and I'll see if anyone in Canada is selling my make/model/wattage panels.

    One reason I hate equalizing the two strings separately is that I always get a big spark when I reconnect the positive at the top of the string, when switching strings. That's because of the possible lingering hydrogen in the room, despite the inline fan in the vent pipe. Is there a way to avoid this spark? Anyone know of a switch I could install to alternate between strings? Is it true that such a switch needs to be rated for something like 200 A to handle the house load, making it impossible to find such a switch?

    To answer some of Bill's questions: First, the batteries have no ground cable connected to them, just the + & - cables. The only other hookup is a temperature sensor to the neg. post of the sixth battery in one string; that's the sensor for the inverter/charger. There is also an RTS sensor for the cc, but it's just hanging between two batteries.
    Second, my cc's logging gives me the daily peak current, and it topped 40 A on 26 of the last 50 days. Is that what you asked for when you asked the maximum current I am seeing from my array (and at what bank voltage); how do I measure/observe these? I can go up on the roof to observe the current for each of the four strings of 3 panels, but when would I do this to get the max current?

    How important is it that any new panels be the same make, model and wattage of the existing ones? I might have trouble finding REC AE-US 215W panels in Canada. They're in 4 sets of 3.

    Time for another stress tab. Smile,
    ...Terry
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: More Surrette problems

    If you are getting 40 amps, then no reason to go on the roof.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: More Surrette problems
    terrynew wrote: »
    One reason I hate equalizing the two strings separately is that I always get a big spark when I reconnect the positive at the top of the string, when switching strings.

    You're doing something wrong if you get a spark. That could be dangerous, not just because of the hydrogen, but because the arc itself can be dangerous. NEVER make/break connections to a battery that is being charged or discharged!

    Everything that is connected to your batteries must have a fuse or circuit breaker. Assuming you have circuit breakers, you just flip the breakers to "OFF" before making/breaking any connections in the battery box. NOTE: most charge controllers require that you disconnect the panels (use the input circuit breaker or combiner box disconnect) before you flip the breaker between the controller and the battery.

    One more thing: After you have disconnected (as above) the inverter and the controller from the batteries, if you still get a spark while disconnecting one string of batteries it means that one string is discharging into the other string. You can figure that out with your clamp ammeter.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: More Surrette problems
    terrynew wrote: »
    Second, my cc's logging gives me the daily peak current, and it topped 40 A on 26 of the last 50 days.

    Is that 40 amps on the input or the output of your charge controller? --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: More Surrette problems
    vtmaps wrote: »
    You're doing something wrong if you get a spark. That could be dangerous, not just because of the hydrogen, but because the arc itself can be dangerous. NEVER make/break connections to a battery that is being charged or discharged!
    One more thing: After you have disconnected (as above) the inverter and the controller from the batteries, if you still get a spark while disconnecting one string of batteries it means that one string is discharging into the other string. You can figure that out with your clamp ammeter.

    --vtMaps

    If you have just charged or even worse equalized one string of batteries, it will still be in the "surface charge" regime and can have an open circuit voltage significantly higher than a rested battery, even one at the same SOC. Using a 1-2-both-off battery switch (most commonly for marine use) can avoid the open spark. (Unless it is totally sealed, it could still ignite vapors, but at least the arc will not injure you.) But resting the just-charged string before paralleling it can go a long way to reducing the initial cross-charging current.
    SMA SB 3000, old BP panels.
  • terrynew
    terrynew Solar Expert Posts: 48 ✭✭
    Re: More Surrette problems

    Thanks for the feedback, everyone. Yay, I avoided the spark by disconnecting the panels first. Thanks for that tip, vtMaps. Too bad I had to go up to the combiner box on the roof, since the &@# installers didn't put a circuit breaker in the electrical room as code requires.

    So I switched to just String 1 of my 2 strings of batteries, absorb-charged them, and then equalized. But upon measuring all post-eq specific gravities, I found the middle cell in the low-voltage battery was *dead*. It read below the 1100 mark on my refractometer. Funny, it was 1250 when I equalised it after installation back in May. Anyways, Surrette has agreed to replace it and I hope to have the new one in a week or two.

    In the meantime, I've switched to String 2. Funny, I got a spark during the switching from String 1 to String 2, even tho I had disconnected the panels like I had when I had removed String 2. Maybe it's the one string discharging into the other string as you suggested, vtMaps? How would a clamp-on ammeter tell me this?

    To answer your other question, vtMaps, my FM80 cc's user guide just says the max daily current meter tells me the max current, without specifying if it's input or output. But I assume it's output.

    Thanks for the tip on getting a 1-2-both-off marine battery switch, inetdog. Would something like http://www.islandwaterworld.com/browse.cfm/battery-switch-200a-1-2-both-off-bep/4,12463.html be appropriate, and meet my house current load?

    So I'm convinced I need more panels, and am getting quotes for 6 of 'em. But we can't find any REC AE-US 215's here in Canada. Am I right that something like a Sharp 220 would be compatible, given that it has the same 60 cells per panel?
    ...Terry
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: More Surrette problems
    terrynew wrote: »
    Thanks for the tip on getting a 1-2-both-off marine battery switch, inetdog. Would something like http://www.islandwaterworld.com/browse.cfm/battery-switch-200a-1-2-both-off-bep/4,12463.html be appropriate, and meet my house current load?

    Looks OK to me. The 200 amp rating and 48 volt DC limit should meet your needs.
    One of the advantages of this type of switch is that by going from 1 to 2 via the Off position, you never connect the two battery strings together, even momentarily, while going from 1 to 2 through the Both position, you connect the two together momentarily but never lose output to your load. You have the choice of which you want to do, but you have to be aware of the difference.
    SMA SB 3000, old BP panels.