Timeline for How to switch power supply between two 24V batteries automatically & efficiently
Current License: CC BY-SA 3.0
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| Aug 16, 2016 at 12:53 | comment | added | Bruce Abbott | You still need the diodes prevent back-feeds. Or for lower loss use back-to-back MOSFETs:- electronic-products-design.com/geek-area/electronics/mosfets/… | |
| Aug 16, 2016 at 8:11 | comment | added | prasanth_ntu | @BruceAbott: Once again, thanks & I have modified the circuit you have shared in the earlier comment. Everything looked fine until i realised that when one battery is cut off or voltage drops than other, the reverse current from the higher voltage battery flows to the lower voltage battery which is kind of troublesome. Is there any fix or alternative solution for this issue? I have attached the circuit with the link below: https://www.circuitlab.com/circuit/yua2vg/bms-v3a/ | |
| Aug 11, 2016 at 6:15 | comment | added | Bruce Abbott | N channel FETs switching battery negatives? You can't do that because the Arduino requires them to always be connected to (its) Ground. If you switch battery positives (which is the only reasonable option) then you need a voltage booster to drive N channel FET gates above the battery voltage. Using P channel FETs is easier. | |
| Aug 11, 2016 at 4:56 | comment | added | prasanth_ntu | Thanks again. Any reason for recommending to use P channel MOSFETs and not N Channel? I assume, for N channel, we don't need a level translators | |
| Aug 11, 2016 at 4:40 | comment | added | Bruce Abbott | Your circuit makes no sense. The load has two battery inputs and two switches going to a common ground, but how does it distinguish between them? The Arduino measures positive voltages only so you should common the battery negatives (= Arduino ground) and switch the positives using P channel MOSFETs. Level translators will be required to change the Arduino's 0~5V output to 24V~12V. These can just be a transistor and two resistors, like this:- electronics.stackexchange.com/questions/70729/… | |
| Aug 11, 2016 at 3:55 | comment | added | prasanth_ntu | @BruceAbott: I added the circuit that i have came up with in the link shared below. I am quite new to electrical circuits and I am pretty sure that there are numerous mistakes in it. Any help/ suggestion/ advise would be highly appreciated. The intended functionality of the circuit is that if battery1 voltage is greater than threshold value, it will turn on NMOS1 using Arduino Digital Pin 1 and vise versa. **[Click here to access the Link for circuit diagram]**(drive.google.com/file/d/0B0F55gMRFtkWU1kxN1UzRmZtdm8/…). | |
| Aug 10, 2016 at 6:56 | comment | added | Bruce Abbott | You would use P channel MOSFETs (rated for at least 30V and 30A) with level shifting gate drivers, or DC solid state relays. The Arduino continuously measures the voltage on each battery, and operates the FETs/SSRs to switch each battery in and out as required. Using a voltage divider is fine. Only requirement is that the resistor going to ground should be 10k or less. | |
| Aug 10, 2016 at 4:59 | comment | added | prasanth_ntu | Thanks for the detailed explanation including narrating the potential problems. Could you explain more on using the solid state circuit (MCU, i already have an arduino) to monitor the battery voltages and control the switchover, and MOSFETs to switch between batteries. I am more interested to explore this option. Note: I am using a 24V battery. For monitoring the battery voltage using an Arduino, would it be advisable to use resistors to do a voltage divider (from 24V to 5v) or is there any better way to do it? | |
| Aug 8, 2016 at 16:31 | history | answered | Bruce Abbott | CC BY-SA 3.0 |