microhydro battery bank

Hello, Hope nobody minds a microhydro based question. I have a small, homemade, battery based microhydro system. I also have grid power. I switch individual circuits back and forth to maximize the hydro, trying to balance the input with the loads. We tend to charge the batteries at night when sleeping and while at work and run them down slightly when home and awake. After about three years I've begun to have battery problems and am researching how to approach dealing with my batteries. My current bank consists of 4- 12 volt 165 amp hr power battery gel batteries run at 48 volts. They charge up fine but lose voltage quickly even at low loads. I never run them below 80% state of charge. Well maybe a few times. I have not tested them carefully to find the problem. I was thinking of upgrading to sun xtender pvx2120l to increase backup capacity. Then started thinking about minimum charge current and how to deal with that. The hydro output is 6.5 amps max at nominal 48 volts . For several months a year it can be lower, some years down to 1 amp. This does not meet the 5% minimum charge current rule. Do I have to size my battery bank smaller? Can I periodically charge at a higher rate with my inverter? ( magnumAE4844). How often would I have to do this? Thanks for any help or suggestions.


  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: microhydro battery bank

    I think you're on the right track: too much battery for the available charging power. If you could maintain 6.5A that would only be good for 130 Amp/hr bank. So your existing bank is too big and is exhibiting exactly the problem that comes from habitual under-charging: slow death.

    You may want to look into adding a grid-connected battery charger such as this:

    And possibly add some solar panels? :D

    But to really help out we'd all like to know your intended use/loads/plan. The microhydro might make a good supplement, but it's hard to get enough head/flow to produce serious amounts of power.

    Could you detail your over-all set up?
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: microhydro battery bank

    it does sound like the batteries were starved at times for a good charge and may have sulfated somewhat now. the output of the charger is high for a 165ah battery bank at about 36% and few flas will normally tolerate that much on a regular basis. also gels aren't good at all with high rates of charge or discharge. solar may be your best bet to add to your microhydro. you will still have to size things because how much the worst charge rate is from the mhydro and how much you draw out of the battery bank as it needs replaced.
    i do suspect your batteries won't last much longer and will need replaced. the sunxtenders are good batteries and will be able to take the high charge rates the inverter can deliver so the grid can help you out when the other renewable sources aren't up to snuff.
  • System2System2 Posts: 6,290 admin
    Re: microhydro battery bank


    I'm new here, but I will throw in a comment:

    The factory guys told me that getting the bank up to a fully charged state is critical, as we all know - chronic undercharging will kill them.

    When I pushed for more info regarding the charge rate, I was told that charging at the high rate is ideal and will certainly extend their life - but is not always practical in all applications.

    Their point was that getting the bank fully charged was the more important factor of the two.

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: microhydro battery bank

    True enough, Marc (we need more people named 'Marc' around here! :p )

    BUT ...

    Insufficient charge current leads to sulphation which gradually reduces the battery's capacity. That means with each successive charge the voltage comes up to the apparent correct amount, but the battery is not truly charged. Funny, isn't it? Why aren't we laughing? Because I just lost $400 worth of batteries to this little peculiarity when a plate shorted out in one cell. According to the meter, the batteries were 'charged'; right voltage for absorb, and float. One battery goes wonky and the whole bank is messed up. Although this case wasn't due to sulphation, the net result is the same. That's why we have this little rule of 5% Amp/hr rate min to try and keep the batteries healthy.

    Of course, even that doesn't always work as I just found out. :cry:
  • mike95490mike95490 Solar Expert Posts: 8,577 ✭✭✭✭✭
    Re: microhydro battery bank
    dscheckman wrote: »
    My current bank consists of 4- 12 volt 165 amp hr power battery gel batteries run at 48 volts.

    The Battery FAQ states that GEL batteries cannot take a high charge rate. (burns voids in the Gel)

    AGM CAN take high charge, let's get clear, what do you have GEL or AGM ?

    The salesman says to charge at high rate. Who stands to make $$??

    What does the mfg say regarding these ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2System2 Posts: 6,290 admin
    Re: microhydro battery bank

    Good Question, My batteries are 4 -Power Battery PSG12165 12 volt 165amphours @C-100. Power Solar Series. Advanced Gel Formula. They are advertised as new technology having the best characteristics of gel and AGM batteries. I think they are basically gel batteries. They were available locally and pretty cheap, about $150 each. I run them in series for a 48 volt system as I have long runs of wire from my turbine to the batteries and inverter. Like "Coot" says I charged them properly with a charge controller (TS45) set to spec and monitored carefully ( Trimetric). Rarely ran them below 90%. Never to anything approaching 50%. Floated them often. I have reached the conclusion they are shot. Figuring out a replacement approach is driving me a bit crazy. I'd like to have a bigger battery bank if anything, not smaller. Maybe accommodate some PV in the future but not right away. Need a sealed battery.I'd like to get 4 sun xtender 12volt 215 amphour and wonder how often I'd have to charge with my inverter (Magnum MSAE4400) to keep them from sulfateing.
    David in Vermont
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: microhydro battery bank

    sorry the batteries are shot. as to the sunxtenders (or lifelines), they have a low self discharge rate and are more efficient on charging. i believe the self discharge is around 2 or 3% per month. i think you'll be quite happy with them once you get over the price.
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: microhydro battery bank
    mike90045 wrote: »
    (burns voids in the Gel)

    And the charge algorithm for gels is far astray from standard flooded or AGMs. Even though my Deltran Battery Tender states that it can handle all three. I'm thinking that gels don't handle bulk very well. This is what causes the voids. IMO.
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