air freighted batteries

System
System Posts: 2,511 admin
in Off Grid Solar & Battery Systems #1
Hi all - I'm new here but have had an off-grid system running at a cabin in SW PR since about 2002. Current system is 24 V, Outback sealed inverter, panels that generate about 20 A at maybe 50 V at high noon plus an Air X that adds a little. Currently 4 Exide (L-16) 400 A-H batteries. Permanently on the system are an internet sat modem (Hughesnet), a Campbell weather station, and GE (Simon) security alarm system. I can monitor battery voltage and AC current draw remotely via the Campbell station. Last summer and fall I was gone for almost 5 months and it worked fine. A friend comes up every month or so and waters the batteries.

In January the system failed. As best we can tell, a power strip that was plugged in but not being used) failed non-gracefully and drew 15 A long enough to draw the batteries below 23 V, at which point the Outback inverter shut down. It appears that one battery is now unrechargeable.

Options? I can certainly replace the one battery but of course all 4 are now 3 years old, so this may not be optimal. How about sealed batteries? I've read that they're optimal for unattended sites. The big problem, however, is that there are few dealers in PR so most likely whatever I buy (other than more L-16s) would need to air freighted in. I used to hear great things about Surrette Rolls but I've been away from the forums for a while. Are they still a good choice? Can they be air freighjted to PR?

Thanks for any suggestions/advice.

Phil
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Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: air freighted batteries

    sorry for your misfortune. i think you can stay with the l16s and buy another if the remaining ones check out ok. can you find somebody to load test them? now no battery will take a prolonged accidental load like that as that can kill them all no matter if agm or fla. maybe you should think of other possible safeguards and weed out any possible stuff that is likely to cause this again. i know there's no guarantees even with the best of equipment.

    i might also add that if you had somebody there for maintenance that it is possible that person possibly did something to cause this or overlooked this problem even if he/she didn't cause it. my speculation should be taken with a grain on this though. beyond that, s**t happens and it'll cost you one way or another.:cry:

    ps- i can't say about shipping to pr, but you might check with our host northern aeizona wind and sun and if you buy 1 l16 then be sure it is the same battery make, model, and capacity to match the others. if they failed or are marginal on load testing then you can buy whatever battery you like to replace all of them.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: air freighted batteries

    There are a few battery monitors with contact closures on them (Xantrex and Victron Energy)... You could program one to cut power/alarm/etc. at 50% State of Charge (for example). Should be much more accurate than other methods... Although, perhaps you can monitor the day AH on the inverter and alarm that if the load profile looks strange on that.

    In the end, which is the bigger issue... Losing a battery (or entire bank) or the loss of power (data logging, repeater/comm up-time failure, etc.).

    Sort of the problem with spending lots of money on a high reliability system vs spending on two cheaper semi-independent power systems with fail over/cycling/monitoring/backup system fails when called online/etc.

    Did the power strip have a surge suppressor/MOV setup? Fuses/surge suppressors/breakers/etc. are many times the source of failures in systems.

    For the most part, reading here, Surrette Rolls still seem to be very good batteries.

    Are you after cost, reliability, reduction in service or what with a battery change?

    If you can still have the friend watering them when needed--I would probably stick with flooded cell. Being able to monitor individual cells with a hydrometer seems to give a bit more information. And I am not sure AGM's will last any longer in your service. Just less water/maintenance/cleanup--at a pretty steep cost.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: air freighted batteries

    Niel, BB - Thanks. I had left a bulb hydrometer on site but critters ate the bulb. I'll get a new one soon as I'm back (next week).

    A load tester is new info for me. Am I correct that for 400 AH batteries I need a 200 A tester? The only one I found in a quick search costs $240 in the States.

    Suggestions on a brand/source?

    Yup, leaving a power strip plugged in but unused was completely avoidable. It was removed and saved - next week I'll take it apart, look at what's inside, and look for heat damage. If that wasn't the source of the problem, I'll absolutely have to look deeper.

    Phil
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: air freighted batteries

    Amazon sometimes has some nice deals:

    http://www.amazon.com/s/ref=nb_sb_ss_c_1_19?url=search-alias%3Dautomotive&field-keywords=battery+load+tester&x=0&y=0&sprefix=battery+load+tester

    Are you looking for a large tester to measure surge current (upwards of C/2.5 of 20 hour AH rating) or thinking more about a C/10 and discharging for an hour or 5+ to check under long term load.

    I am not sure which I would use--but tending towards measuring long term load support (with a load that won't overheat) would seem to test the battery in similar conditions to your usage vs high current for a minute (like a cranking test of C/1 or higher current).

    Would be interesting to read how others here "test" for good/bad batteries.

    If you have parallel battery strings, a cheap (or expensive) DC Clamp Current Meter would allow you to measure differences between parallel battery strings under heavy load/charging.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #6
    Re: air freighted batteries

    Amazon selection looks great. Thanks. It's a single string of 4 (24 V nominal). Until this failure it seemed pretty well suited to the load. Went up to 29.6 V by early afternoon, then down to 25.5-26 in the evening, depending on evening usage. Yes, there's a clamp meter on site.

    As for C/?, and for how long, I could use some advice. Clearly the one bad battery is history as it won't charge up at all. But load testing of the other 3 should clue me into whether it makes any sense to only replace the one battery.

    Phil
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Re: air freighted batteries

    C/8 is a good rough maximum current for most flooded cell storage batteries (won't overheat, should not warp plates). Discharge a battery for 4 hours will take you to 50% state of charge. You can discharge down to 20% state of charge (~6.4 hours) if you want to really stress the batteries...

    More or less, choose your maximum expected discharge level.

    Personally, with batteries that are more than ~1 year old, if they have been taken to 10.5 volts or less (i.e., dead 12 volt battery), then I would seriously consider replacement if this is a critical application.

    I have seen too many cars that have worked fine, batteries cranked dead (or lights left on). Electrical problem addressed, battery recharged, everything looks good--and two weeks later, the battery will not start the car (battery failed). If the battery makes it past the 2 week period--it probably is OK for now (my personal opinion--others will probably differ).

    Again, depends on your needs and ability to service the installation (can you get out the next day with 4 new L-16 batteries--and is that good enough).

    You might also look at a cutout switch of some sort set for ~23 volts (11.5 volts @ 12 volt bank)... Or whatever minimum voltage makes sense for your setup. Voltage based shutdown of a battery bank is pretty iffy... Between loads, temperature, age, etc.--the voltage of a running battery bank (charging/loaded) is not a very good indicator of state of charge.

    But--again it depends--I developed a system for use in Central Offices (large Voice Mail System)--And their policy was, they wanted reliable, instrumented systems, but in the end--they wanted the systems to run to destruction and not shut down to preserve equipment (assumption that telephone switch was critical infrastructure and it was better for it to run longer than shut down to save a battery bank or equipment if the A/C failed).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #8
    Re: air freighted batteries

    A power strip drawing 15 amps and not burning the place flat to the ground? Extremely, highly unlikely. At 120 volts (fed by "Outback sealed inverter", 15 amps would turn that little power strip into a 1800 watt electric heater for an extremely short time, then promptly into a ball of flames. Was it by chance, your "friend" who suggested the power strip as the cause of the problem?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: air freighted batteries

    before you buy a load tester try some major automotive service places near you to see if they may have one and charge you a small fee to test your batteries.
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