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Battery charging- Float mode and boost mode

Discussion in 'Power Electronics' started by bobdxcool, Aug 1, 2015.

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  1. bobdxcool


    Mar 9, 2012
    Based on my knowledge on batteries (AGM), the initial battery charging (for ex. a 12V, 200AH battery and a 24V, 20 amp charger ), takes not more than 2-3 hours for the first 70% charge and then it takes like 4-5 hours to charge to 100%. Why is that the initial charging happens so fast ?
  2. JMW


    Jan 30, 2012
    On flooded cell batteries you can charge at 50% of the capacity until the battery reaches 80%, then 10% of capacity 95% then 1% to top it off.
    I hope it was a mistype on using a 24 VDC charger on a 12 V battery.
    There are similar constraints on AGM batteries, AGM don't like overcharging. There used to be a site called Battery University. Goes into great detail
  3. BGB


    Nov 30, 2014
    typical battery charge rage for AGM is 0.3C, which is about 60A. 50A is pretty close to this.

    near the upper end, you can't really control the charge rate, since the battery will only take what it wants to take at a given voltage. at lower levels of charge, it will try to take a lot more, so it may be necessary to current-limit things.

    and, that last 10%-15% or so will take a very long time.

    this is unlike NiCd or NiMH, which will keep taking power until they destroy themselves, requiring some mechanism to detect and intervene when the battery is charged (typically charging it really slow and using a temperature sensor or similar), or for some cheap chargers simply waiting for the user to notice that the batteries are hot.

    for running a 24V system off 12V batteries, they are linked in serial. then the voltages add up, ex: 12+12=24.
    you can also link in parallel for more capacity, or both, and you charge them as if they were a much bigger battery at the given voltage.
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