Looking to Upgrade DC system

Discussion in 'OnBoard Electronics & Controls' started by mydauphin, Feb 21, 2012.

  1. BPL
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    BPL Senior Member

    in series or? parallel. Otherwise I don't follow you.
     
  2. BertKu
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    BertKu Senior Member

    What he means is, to have batteries switched parrallel or in serial, you need batteries which are all of them in the same condition, thus throw all your batteries out of the window and buy 4 new ones. 2 in serial and again 2 in serial and at the 24 Volt side parallel.

    What we are saying is, if you use Schottky diodes at the 24 Volt side and you protect the batteries placed in serial halfway , whatever methode, kind of high current zenerdiodes, you can use a mix of any kind of lead acid battery, without to replace all 4 batteries, when one of them goes bad.

    By the way, most electronics today uses MOSFets, which are thousands of transistors parallel, the same for some diode technology. To use 10 times Vishay diodes to get a comfortable 150 Ampere is a modern way of solving problems. Unfortunately some people are living on an other planet.
    Bert
     
  3. BertKu
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    BertKu Senior Member

    The drawing from thread no1 may be misleading and the batteries are not connected at the + 24 side, but are 3 individual sets of 2 batteries in serial.

    If you charge each set separately for a period of time and the sets are not connected at the 24 side (not even through the charger) then you will have little problems. If they are connected at the 24 Volt side, your charger need to be able to supply 3 x the current for your 3 sets.

    First at all you need to understand that a Lead Acid battery charges chemically already at 12 Volt. The fact that nobody wants to wait for 24 hours before the battery is charged, means one has to go to a higher Voltage and most Lead Acid batteries are charged at 14.4 Volt.

    As soon the battery is fully charged, the excess current, because of the 14,4 Volt will create gassing . This process start a 13.8 Volt. Thus the trick is to measure a battery immediately when you take the charger off. (Most batteries today are sealed and you cannot, like somebody else said, measure the status of the liquid). Thus if your battery is slowly dropping from 13.8 Volt to a lower level, your battery is pretty well charged.

    If you connect 10 batteries of "12 Volt" type in serial and you are so lucky to have a high Voltage charger, all what is needed is to check constantly the voltage of each battery. If the one falls behind the others in Voltage, you need to isolate this battery and charge it seperately with a 12 Volt charger. If you have 10 batteries of each cell of 2,25 Volt, you also need to monitor each battery, but the voltage you need to compare is only 2.3 Volt. (gassing threashold)

    If you have a charger which charge only at 13.6 Volt, (or a multiple number x 13.6 Volt for batteries in series) it will take longer, but you cannot damage your battery. You just need lots of time.
     
  4. pistnbroke
    Joined: Jan 2009
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    pistnbroke I try

    All the batteries I use day to day have computer chips in them to control there little lives ..so if this is such a good idea why dont the makers put controllers inside the batteries to balance the voltages on individual cells ( like LiFe) . What you are doing is certainly possible .If its worthwhile and practical is another issue..to go your route 4 x 6v batteries with balancing would be better than 2x12v ...and a controller for each cell the best.......

    for the cost of batteries its not worth the effort and the chances of big gains are remote.

    Using batteries of mixed condition ????As a very good friend of mine said of batteries " if its F@cked its F@cked"
     

  5. BertKu
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    BertKu Senior Member

    Most likely the Lead acid batteries do not go out of balance as easily as Lithium. However, people do often put old or half charged batteries together with new or fully charged batteries and then you have a situation. (with sealed batteries, one cannot easy test it anymore with a acid tester).
    I am doing it already for years as I have, although smaller, but still Sealed Lead Acid batteries charged in series. I am using two heavy 6.8Volt Zenerdiode circuits, which clips the one Voltage, should the customer put half discharged and fully discharged batteries in series. By allowing to bypass the charging current through the fully charged battery, the fully charged battery does not get damaged by exceeding 13.8 Volt for a long time. The chargers I am making are used by customers who have absolute no clue what batteries can do and not do.
    But the batteries have all the time in the world to get charged, there is no time restrain. However they use the batteries for up to 12 hours, without being put back onto the charger and often forget it for a couple of days.


    I don't think it is neccessary, it will be an overkill. Only those people who are using batteries in a kind of deep charging situation and are using batteries placed in series with different loads should consider to make some form of balancing. or charging protection circuits.

    True, but we giving the readers all options in what can be and cannot be done. It is up to them to make the final decision.


    We musn't forget the situation in having batteries in series with different loads on each battery. Example: one uses over the 24 Volt in series placed batteries a 24 Volt host and uses over the 12 Volt a series of appliances or lights. People will do that sort of thing.
    Bert
     
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