Question about Battery Charging

[labgruppen]

@marleona, why not use a mosfet instead to switch your solar panel. baka mas mura pa sa relay and its associated supporting components.  and don't forget to insert a blocking diode (in series with your solar panel) to prevent discharge of your battery through the solar panel if there is not enough light shining on it.

[marleona]

@marleona, why not use a mosfet instead to switch your solar panel. baka mas mura pa sa relay and its associated supporting components.  and don't forget to insert a blocking diode (in series with your solar panel) to prevent discharge of your battery through the solar panel if there is not enough light shining on it.

yep, nalagyan ko na po siya ng blocking diode. may circuit po ba kayo regarding sa mosfet? kasi ung naunang post kay repax using relay try ko siya gawin bukas at masubukan in practice.

[labgruppen]

isang sample ito.. the mosfet should be logic type such as 20N03L , MTP15N06VL , etc. paki lagyan na lang ng blocking diode, di pinakita sa diagram.  ang maganda sa mosfet as switching element ay pwede kang mag implement ng PWM para sa charging mo. say kung malapit nang mafull charge yung battery, bababa yung duty cycle to lower charging current. tapos pag full charge na yung battery, i-memaintain nya yung duty cycle just enough for the load current + trickle charge current ng battery. anyway, since meron ka nang components for the relay switching, it would be more practical to continue with that scheme.

[marleona]

^kaya nga po... at saka 2 battery eh magswitch siya kapag puno na si Batt a to Batt b. Anyways ang galing pala nun dahil kasi pwede niya macontrol ung charging current flowing through batteries... hahaha napapaisip tuloy ako!!! pero sige check ko pa rin kung pwede ung dalawang options!?

[labgruppen]

you could easily independent bank charging with mosfet. just add another mosfet(mosfet B) for batt B. mosfet B is driven by another gpio (GPIO_B). each battery is monitored by its own adc channel. now, just implement in firmware when to switch mosfet A or mosfet B based on the readings of adc ch A and adc ch B.

[marleona]

wahahahah un lang gagamit ako ng isa pang gpio para sa isang battery hehehe. pero may question po ako ?

may kulang po yang circuit....


put rectifier diode in series with the battery...to avoid back pedal ng current in time mag charge ang battery....

yan ung gusto kong gawin kung relay, pero paano ko naman siya iimplement kapag load??? well meron na yan para sa "solar cell" as a load eh what if naman po kung load niya talaga ay load na??? paano ko siya ipapasok sa batt A and batt B at siyempre gagamit pa ako ulit ng ibang gpio kasi siya ung magcontrol kung wala na si batt a at switch siya kay batt b??? wahaha hirap iexplain??? or pa follow na lang po nito... http://www.electronicslab.ph/forum/index.php/topic,15433.20.html#quickreply

[labgruppen]

take a look at this.. tipid na sa GPIOs ito..

battery voltages are monitored by adc channels 0 and 1 via voltage dividers (to provide proper voltage levels to adc inputs). if batt1 needs charging, PA0 should turn high, turning on mosfet Q1 which charges batt1. a high PA0 also turns on mosfet Q2 thus putting the load on batt2. if however batt2 needs charging, PA1 should turn high, turning on mosfet Q4 which charges batt2. a high PA1 also turns on mosfet Q3 thus putting the load on batt1.  note however that in this scheme, the solar panel must also be continuously on charging either one of the batteries in order to power the load continuously. thus you can not implement PWM charging here.  to have more flexibility in features, you can drive each mosfets via their on GPIO (say Q6 driven by PA3, Q8 by PA4). with each mosfet driven by separate GPIO, you can implement PWM charging, LVD (low voltage disconnect which turns off the load if both battery levels are too low and at the same time turn on the panel to charge a battery), make before break switching (this ensures that the load is connected to a power source at all times). the zener diodes are there to protect the mosfets from excessive vgs (refer to your mosfets specs for the max vgs and choose zener diode voltage accordingly). you can also replace the mosfets with relays if you prefer using relays. diodes d7 and d8 ensures continuous mcu power.

[DigitalMind]

take a look at this.. tipid na sa GPIOs ito..
battery voltages are monitored by adc channels 0 and 1 via voltage dividers (to provide proper voltage levels to adc inputs). if batt1 needs charging, PA0 should turn high, turning on mosfet Q1 which charges batt1. a high PA0 also turns on mosfet Q2 thus putting the load on batt2. if however batt2 needs charging, PA1 should turn high, turning on mosfet Q4 which charges batt2. a high PA1 also turns on mosfet Q3 thus putting the load on batt1.  note however that in this scheme, the solar panel must also be continuously on charging either one of the batteries in order to power the load continuously. thus you can not implement PWM charging here.  to have more flexibility in features, you can drive each mosfets via their on GPIO (say Q6 driven by PA3, Q8 by PA4). with each mosfet driven by separate GPIO, you can implement PWM charging, LVD (low voltage disconnect which turns off the load if both battery levels are too low and at the same time turn on the panel to charge a battery), make before break switching (this ensures that the load is connected to a power source at all times). the zener diodes are there to protect the mosfets from excessive vgs (refer to your mosfets specs for the max vgs and choose zener diode voltage accordingly). you can also replace the mosfets with relays if you prefer using relays. diodes d7 and d8 ensures continuous mcu power.

that's already merely a finished product. imho. ewan ko na lang talaga. thanks for posting.

[marleona]

^hahahaha uu nga po. salamat, pero mukhang di ko gagawin ung circuit na to. since relay lang po kasi ung gagamitin ko. nagdadalawang isip lang kasi ako kung iswitch ko siya sa batt a to batt b to load eh hindi ba maturn off si mcu kapag nangyari un. pero sa circuit nakita ko ung capacitor to mcu regulator na un ung magserve ng quick transition to batt a to batt b para di maturn off ung buong system.

[labgruppen]

^hahahaha uu nga po. salamat, pero mukhang di ko gagawin ung circuit na to. since relay lang po kasi ung gagamitin ko. nagdadalawang isip lang kasi ako kung iswitch ko siya sa batt a to batt b to load eh hindi ba maturn off si mcu kapag nangyari un. pero sa circuit nakita ko ung capacitor to mcu regulator na un ung magserve ng quick transition to batt a to batt b para di maturn off ung buong system.

the mcu need not change power together with the load. in the example above, d7 and d8 makes the mcu get power from the battery that has higher voltage.  only the load is switched.

[DigitalMind]

^hahahaha uu nga po. salamat, pero mukhang di ko gagawin ung circuit na to. since relay lang po kasi ung gagamitin ko. nagdadalawang isip lang kasi ako kung iswitch ko siya sa batt a to batt b to load eh hindi ba maturn off si mcu kapag nangyari un. pero sa circuit nakita ko ung capacitor to mcu regulator na un ung magserve ng quick transition to batt a to batt b para di maturn off ung buong system.

you'll reconsider using mosfet...
1.) much cheaper ang mosfets than relays.
2.) relay eat currents... alots. specially solar power application mo. as much as 300mA!
3.) so much more high tech looking. cleaner layout than bulky relays. (yuck)

[marleona]

you'll reconsider using mosfet...
1.) much cheaper ang mosfets than relays.
2.) relay eat currents... alots. specially solar power application mo. as much as 300mA!
3.) so much more high tech looking. cleaner layout than bulky relays. (yuck)

hahahaha aaminin ko na po, gets ko ung circuit at siguro ung mosfet kung ano ung part number kasi nasabi na ni sir labgruppen kung ano ung gagamitin eh kaso may zener diode pa diyan etc. ayaw ko ma spoonfeed dito sobra sobra na nga ung tulong ninyo eh. ok na ako siguro sa relay kahit may downside siya at tapos bulky nga lang, pero maliit naman ung nabili ko eh 5v coil rating tapos 30VDC @5A ung sa contact hahaha enough na un sa solar panel namin.

[marleona]

add ko lang pala... mukhang off topic po ito eh. Tanong lang kung magswitch si batt a to batt b na nakakabit sa mcu hindi ba magshutdown si mcu??? pero pageexperimentuhan ko pa ito bukas eh using relays and switch from batt a to batt b at titingnan ko kung ano mangyayari sa mcu kung magrestart o magshutdown. pero sabihin ko kaagad ung results para kung pwede na. Maraming salamat!!!

[labgruppen]

add ko lang pala... mukhang off topic po ito eh. Tanong lang kung magswitch si batt a to batt b na nakakabit sa mcu hindi ba magshutdown si mcu??? pero pageexperimentuhan ko pa ito bukas eh using relays and switch from batt a to batt b at titingnan ko kung ano mangyayari sa mcu kung magrestart o magshutdown. pero sabihin ko kaagad ung results para kung pwede na. Maraming salamat!!!

kung gagamitan mo nga ng "OR-ing" diodes kagaya sa example ko (d7 and d8) di sya magshu-shutdown.  magiging sort of 1+1 redundant yung power section ng mcu mo. the mcu will take its power from the battery with higher voltage regardless of which battery is connected to your load. note that diodes d7 and d8 are connected to their respective battery directly, not through any switching element (be it a mosfet or a relay). dapat si load lang at si solar panel ang pipili kina batt a or batt b.

[labgruppen]

hahahaha aaminin ko na po, gets ko ung circuit at siguro ung mosfet kung ano ung part number kasi nasabi na ni sir labgruppen kung ano ung gagamitin eh kaso may zener diode pa diyan etc. ayaw ko ma spoonfeed dito sobra sobra na nga ung tulong ninyo eh. ok na ako siguro sa relay kahit may downside siya at tapos bulky nga lang, pero maliit naman ung nabili ko eh 5v coil rating tapos 30VDC @5A ung sa contact hahaha enough na un sa solar panel namin.

I agree with sir martin. tapos dpak pa yung packaging ng mosfet mo, astig! btw, if ever after finishing your project with relays and decide to explore the same project with mosfets, take note that the part nos. I first posted does not apply with the 2nd circuit I posted. The second circuit uses p channel mosfets and does not require logic type mosfets. IRF7404 looks promising for the solar panel mosfets.. (in soic8 package ito kaya looks hitech) max Vgs is +/- 12 volts, and can conduct at least 5 amperes at Vgs=4.5,  a 6 volt zener will provide ample protection against excessive Vgs while ensuring more than enough Vgs for your solar panel current. Btw, since you will be using relays, i think i am not guilty of spoon-feeding. Don't forget the fuses for your batteries. They may be just 17Ah but they can surely deliver extremely high currents (50's to hundreds of amps) when short circuited.

[marleona]

^wahahaha yep. kapag tapos na ako sa project ko with relays I'll experiment on using mosfets tingin ko astig siya!!! yep, lalagyan ko po siya ng fuses just in case lang naman at least sure na safe ung buong system ko wahahaha.