Controversial! Why Solar can damage your batteries!

Discussion in 'Tech/Mech General' started by jonandshell, Oct 17, 2014.

  1. jonandshell

    jonandshell Funster

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    Following on from another thread where I mentioned that we don't have solar panels, here is my reasoning-

    In my industry, our electrically powered machines are run by good old open lead acid traction batteries. Traction monoblocs are my chosen method of running our habitation electrics.
    All the batteries supplied to our customers are covered by a manufacturers warranty of 5 years. This is not a warranty of averages, this is a warranty based on 250 cycles a year at a 6 hour discharge rate. The battery useage can be easily monitored by means of downloading the cycle data from the chargers.
    Now, the number one reason for warranty rejection by our suppliers is 'customer opportune charging'. This means the battery user is putting the battery on charge for short periods, often on breaks or between shifts, in an effort to top up the battery charge.
    The result of this 'opportune charging' is that the battery capacity gradually falls and thus more opportune charging is applied in an effort to complete the days work. This trend destroys the battery cells through gradual sulphation.

    Here is the explanation-

    Sulfation occurs when a lead acid battery is deprived of a full charge. This is common with starter batteries in cars driven in the city with load-hungry accessories. A motor in idle or at low speed cannot charge the battery sufficiently.

    Electric wheelchairs have a similar problem in that the users might not charge the battery long enough. An eight-hour charge during the night when the chair is free is not enough. Lead acid must periodically be charged 14–16 hours to attain full saturation. This may be the reason why wheelchair batteries last only two years, whereas golf car batteries deliver twice the service life. Longer leisure time allows golf car batteries to get the fully saturated charge.

    Solar cells and wind turbines do not always provide sufficient charge, and lead acid banks succumb to sulfation. This happens in remote parts of the world where villagers draw generous amounts of electricity with insufficient renewable resources to charge the batteries. The result is a short battery life. Only a periodic fully saturated charge could solve the problem, but without an electrical grid at their disposal, this is almost impossible. An alternative is using lithium-ion, a battery that is forgiving to a partial charge, but this would cost about six-times as much as lead acid.

    What is sulfation? During use, small sulfate crystals form, but these are normal and are not harmful. During prolonged charge deprivation, however, the amorphous lead sulfate converts to a stable crystalline that deposits on the negative plates. This leads to the development of large crystals, which reduce the battery’s active material that is responsible for high capacity and low resistance. Sulfation also lowers charge acceptance. Sulfation charging will take longer because of elevated internal resistance.

    OK, so back to the title of this thread-

    Solar power cannot guarantee to fully charge your batteries, especially in winter. Likewise, neither can a conventional split charge system.

    The only way to prevent gradual sulphation of your batteries is completing a full charge cycle by means of a B2B charger or the MH's built in charger.

    Any questions?:reel:
     
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  2. hilldweller

    hilldweller Funster Life Member

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    You seem to be missing the point. Those who can't hook up need solar to survive. In reality a shortened battery life is probably cheaper than paying hook up regularly.
     
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  3. jonandshell

    jonandshell Funster

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    I am not missing the point as regards the effect of solar opportune charging on your batteries.
    However, putting the health of your batteries to one side, solar is a good thing! It provides a hassle free energy source and it can offer complete charging if it is sunny, your useage of power is low, or your van is in storage.
    We never go anywhere sunny, use little power or store our van!

    It did say this would be controversial!
     
  4. RS_rob

    RS_rob Funster

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    Sounds like Memory Effect to me (y)
     
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  5. jonandshell

    jonandshell Funster

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    In layman's terms, yes!
     
  6. RS_rob

    RS_rob Funster

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    :BigGrin: yay I finally leanrt something about batteries :boxing: & my mate & the tinternet was right :D
    My RC batteries suffer that cos i never discharge them properly :notworthy:
     
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  7. Mike B

    Mike B Funster

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    So how about using solar for the meet/rally and then putting your batteries on full charge for 24hrs on your return home? :)
     
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  8. DP_JAY

    DP_JAY Funster Life Member

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    All I know is we have 3 year old cheapo leisure batteries charged by cheapo solar panels with a cheapo regulator for 3 years and it all still works. Except in the deapths of winter(when we use hook up if away for longer than a few days)the batteries are showing fully charged long before the daylight goes.
     
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  9. jonandshell

    jonandshell Funster

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    Of course, incomplete charging by ANY means damages batteries.
    I was just picking on solar as the most likely culprit!!!!!!!:Smile:

    However, in answer to the above question, despite our sixty megawatt atomic Sterling Alternator to Battery charger, we frequently arrive home from short trips with partially recharged batteries.

    Plugging into EHU and letting the built in mains charger finish the charge cycle is the only answer.:cheers:
     
  10. DuxDeluxe

    DuxDeluxe Funster Life Member

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    I'd better chuck the solar panels away then...... for fear of terminally damaging my £80 leisure batteries.

    Ducks know bugger all about electrickery but It really needs to be put into context and thousands of solar panel users appear to have no issues.

    Thanks for the information but we will manage the risk, thanks(y)
     
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  11. cliffandger

    cliffandger Funster Life Member

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    Cliff had a lecturer at college years ago who used to be an officer who worked on submarines and whose duties were maintenance of battery banks which on a diesel submarine was the most important job. He told us for maximum life on a lead acid battery they need to be periodically discharged fairly rapidly them brought back up to a full charge but not too quickly. His theory being that this practice descaled the plates. He said in the real world where we all need to use our batteries all the time it's a very difficult thing to so as a rule.
     
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  12. Techno

    Techno Funster Life Member

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    I have an inverter with built in 3 stage charger now i.e. a UPS
    The last three times I hooked up I turned the charger on only to find that it reports my batteries as full.
    So this concludes that my 300watt solar is keeping my batteries tip top so I expect them to easily last beyond their warranty before giving them away after 4 yrs and renewing.
     
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  13. jonandshell

    jonandshell Funster

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    A good example of your solar charging keeping up with, or exceeding your discharge rates.

    Many folks fit only a 100 watt panel and the resulting charge, discharge, partial charge, discharge, partial charge cycle is what will cause sulphation issues.
     
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  14. Allanm

    Allanm Funster

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    I didn't think that lead acid batteries suffered from memory effect. I used to work for BT many years ago, all exchanges were run by banks of lead acid batteries permanently connected to the equipment at one end and a charger. Very rarely were the batteries put under extended load ( only during a power cut, but most exchanges had generators that would cut in after a few minutes.
    These batteries lasted for years with just regular topping up and SG checks. In fact when one of the exchanges closed down, I bought the batteries and used them as a huge UPS system. They worked perfectly for another few years. If they had been subject to the memory effect I would have thought they would have had a very short life.
    Allan
     
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  15. vwalan

    vwalan Funster

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    i find my batteries get a better charge in winter .possibly than they do in summer . i only ever use solar to charge them . apart from when driving with the trailer hooked to the truck.
    isnt solar better in winter?
    better ask mo. or snowy .
    i,m sure it is . hee hee .
     
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  16. jonandshell

    jonandshell Funster

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    The scenario you had Alan, was that the batteries were partially discharged then recharged fully.
    It is not the shallow depth of discharge that causes lead acid battery sulphation but the failure to completely recharge.
    You are right in saying that you can discharge a lead acid battery any amount (but not beyond 100%) and no 'memory effect' or sulphation takes place.
    Its the full recharge that is critical.
     
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  17. jonandshell

    jonandshell Funster

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    Interestingly, for battery spotters that is, the chances are that those BT batteries most likely failed not from sulphation, but stratification.
    The lack of regular movement of the batteries would have resulted in lack of electrolyte mixing.
    The acid sinks to the bottom where the concentration increases. The acid then erodes the seperator plates and short circuits in the cells occur. The battery then will not charge.

    This can also occur in batteries which are not topped up with water when required. The electrolyte becomes more concentrated and the separator plates again are eroded by the acid.
     
  18. RS_rob

    RS_rob Funster

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    A diagram might help right now (y)
     
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  19. vwalan

    vwalan Funster

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    how about this as a diagram. first one nice blue sky solar working fine .
    second one grey cloudy sky solar panels not working too good .
    better not use too much leccy that day.
    hee hee .
     

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  20. RS_rob

    RS_rob Funster

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    lol ffsk should have seen that coming pmsl

    I meant of the battery in question for those following but not commenting..........
     
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