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Solar charge controller for lithium batterys

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(@davee)
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Hi @nurderfch1846 & Ron @zander,

re: It included the bracket at the end. here´s the correct link: https://cdn-reichelt.de/documents/datenblatt/C160/GM82.6_6v_db_en.pdf

and

Stall current is 3200mA, so for two motors 6400mA. That´s also at 6V, so it would be even more at 3,7V.

  • If, as appears but I couldn't see stated, these are brushed DC motors, then powering 6V motors with 3-3.7V will greatly reduce their speed and torque ... their output might still be enough for your purposes, but they might not even move. Or perhaps you are using a boost converter to increase the voltage to 6V?
  • The last statement about stall current ... if you are supplying 3.7V, then the stall current will be proportionately less, not more. If you are using a boost converter to supply the motors with 6V, then the current drawn by the motors will be as stated, but the current input to boost converter will be obviously be considerably more.
  • Powering a DC brushed motor in its stalled state will rapidly overheat and destroy it. Obviously, when power is first applied to a stationary motor, it will be momentarily 'stalled', and draw that maximum current, but 1 second (say) later, the motor will normally be spinning, and the current demand much lower. To some extent, the battery can probably supply a higher current for a very short time. Hence, it is sensible to match the motor and the battery, considering their respective specifications for brief overloads, as well as continuous operation.
  • Consider protection scheme for stalled motor, that will limit or cut-off power if the motor is stalled for more than very short time (seconds probably!) .... otherwise you may experience magic smoke from both motors and batteries ... the motor magic smoke may be expensive, but the battery magic smoke is very toxic, fire risk, etc. as well. Note maximum motor current specification of 420 mA ... much less than the stall current. This is an indication of the level the protection scheme should enforce, allowing for the brief 'spin up' time.

Best wishes,

Dave


   
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(@nurderfch1846)
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Joined: 10 months ago
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@davee

Posted by: @davee

Or perhaps you are using a boost converter to increase the voltage to 6V?

I´m planning on using one, yes.

Posted by: @davee

Note maximum motor current specification of 420 mA ...

Why is it rated current (max.) in the datasheet? How can the rated current be max.? As far as I know, the rated current is the current that is consumed by the motor at the point where the efficiency of the motor is at its maximum. And that´s constant, right?


   
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(@davee)
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Joined: 3 years ago
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Hi @nurderfch1846 ,

The power input max of 6V at 420mA is specification of what they expect the motor can cope with in 'normal' conditions  .... appreciably exceeding this for an extended time risks overheating, and hence premature failure. Obviously, this is not a precise number, but exceeding it will almost certainly reduce its life. If you design a 'device' that requires a power input greater than this, it suggests you chose the wrong motor.

If you were designing  a commercial product, then exceeding it could have huge costs in terms of warranty replacements, reputation of your company's products, etc.

Best wishes, Dave


   
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(@nurderfch1846)
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@davee Ok, thanks for the clarification.


   
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