Skip to main content

$1 Solar Battery Charger

The post explains a  cheap yet effective, less than $1 cheap yet effective solar charger circuit, which can be built even by a layman for harnessing efficient solar battery charging.

What is Maximum Power Point Solar Tracking?


For a layman this would be something too complex and sophisticated to grasp and a system involving extreme electronics.

In a way it may be true and surely MPPTs are sophisticated high end devices which are meant for optimizing the charging of the battery without altering the solar panel V/I curve.

In simple words an MPPT tracks the instantaneous maximum available voltage from the solar panel and adjusts the charging rate of the battery such that the panel voltage remains unaffected or away from loading.

Simply put, a solar panel would work most efficiently if its maximum circumstantial voltage is not dragged down to the connected battery voltage which is being charged.

For example, if the open circuit voltage of your solar panel is 20V and the battery to be charged is rated at 12V, and if you connect the two directly would cause the panel voltage to drop to the battery voltage, which would make things too inefficient.

Conversely if you could keep the panel voltage unaltered yet extract the best possible charging option from it, would make the system work with MPPT principle.

So it's all about charging the battery optimally without affecting or dropping the panel voltage.

There's one simple and zero cost method of implementing the above conditions.

Choose a solar panel whose open circuit voltage matches the battery charging voltage. Meaning for a 12V battery you may choose a panel with 15V and that would produce maximum optimization of both the parameters.

However practically the above conditions could be difficult to achieve because solar panels never produce constant outputs, and tend to generate deteriorating power levels in response to varying sun ray positions.

That's why always a much higher rated solar panel is recommended so that even under worse day time conditions it keeps the battery charging.

Having said that, by no means it is necessary to go for expensive MPpT systems, you can get similar results by spending a few bucks for it. The following discussion will make the procedures clear.

How to make a $1 MPPT Circuit


As discussed above, in order to avoid unnecessary loading of the panel we need to have conditions ideally matching the PV voltage with the battery voltage.

This can be done by using a few diodes, a cheap voltmeter or your existing  multimeter and a rotary switch. Ofcourse at around $1 you cannot expect it to be automatic, you may have to work with the switch quite a  few times each day.

We know that a rectifier diode's forward voltage drop is around 0.6 volts, so by adding many diodes in series it can be possible to isolate the panel from getting dragged to the connected battery voltage.

Referring to the circuit digaram given below, a cool little MPPT charger can be arranged using the shown cheap components.

Let's assume in the diagram, the panel open circuit voltage to be 20V and the battery to be rated at 12V.

Connecting them directly would drag the panel voltage to the battery level making things inappropriate.

By adding 9 diodes in series we effectively isolate the panel from getting loaded and dragged to the battery voltage and yet extract the Maximum charging current from it.

The total forward drop of the combined diodes would be around 5V, plus battery charging voltage 14.4V gives around 20V, meaning once connected with all the diodes in series during peak sunshine, the panel voltage would drop marginally to may be around 19V resulting an efficient charging of the battery.

Now suppose the sun begins dipping, causing the panel voltage to drop below the rated voltage, this can be monitored across the connected voltmeter, and a few diodes skipped until the battery is restored with receiving optimal power.

The arrow symbol shown connected with the panel voltage positive can be replaced with a rotary switched for the recommended selection of the diodes in series.

With the above situation implemented, a clear MPPT charging conditions can be simulated effectively without employing costly devices. You can do this for all types of panels and batteries just by including more number of diodes in series.

The explained circuit can be somehow made automatic, you may refer to the following post to learn the automatic version of the above explained design.

https://homemade-circuits.com/2013/09/incremental-conductance-type-solar-mppt.html

 



 

Need Help? Please leave a comment, I'll get back soon with a reply!




Comments

  1. Wow, what a great idea. So simple and efficient MPPT charger.
    You are super genius Sir.

    Thank you for sharing.

    Rashid

    ReplyDelete
  2. Thank you Rashid, it couldn't have been possible without the support and encouragement from engrossed readers like you.

    ReplyDelete
  3. It's difficult to make high quality PCB at home, it's better to get it done from a pcb maker.

    ReplyDelete
  4. Yes that's right. There are plenty of PCB manufacturers in Mumbai,you can easily find them by Googling the relevant keywords.

    ReplyDelete
  5. wish you the same!

    I am sorry that won't be possible,

    these are just diodes connected in series, i think you can easily do it yourself....

    ReplyDelete
  6. I am sorry, that wouldn't be possible either, in the future I would surely want to consider it, thanks!

    ReplyDelete
  7. superb sir you r relay ingenious





    ReplyDelete
  8. HAI DEAR SIR. men pakistan say hon .sir mujhy urdo ya hindi men btain kh meary pass 2 solar penal hen 60watt each.butt ab un men jalny k nshan aa gy hen dono penal 3.5amp curnt dy rhy hen 175amp batry k sath lgy thy drect.one year ago its rating 7 to 8amp now 3.5 amp hi rating. ab agar men new 150wat ka penal lun tu sab say sasta treqa kun sa hi jo istmal kr k men dono ki efeshacy achi ly skta hon. diode kun say hon kis trh lgaon takh batry bhi charge ho ower chage na ho.plz

    ReplyDelete
  9. Hello Hassnain,

    Solar panel kabhi jal nahi sakte, yeh kharab ho sakte hai par jal nahi sakte.

    naye panel ka aur battery ka voltage rating bataye, tabhi circuit batana mumkin ho sakta hai.

    English:

    solar panels can never burn, these can get damaged by other means but not through short circuit or over load.

    specify the voltage rating of the new panel and the battery, I'll try to suggest an appropriate charger circuit.

    ReplyDelete
  10. thans sir for reply...acid battry 150ah 12volt .solor 150watt 12volt 2 plate each 150watt 12volt. batry ko owercharge bhi na kren sasta bhi ho.diode wala method type. diode name bnany ka treqa udu men plz btain .agar sir ho sky to pix bhi snd kr den

    ReplyDelete
  11. phly penal men jalny jeasy draren ai hen tqrebun hr cell men arhy trchy lkiren type amp bhi km howey hin drect battry k sath plats lgy the one year ago.8amp say 4.5 amp hin ab peack pr

    ReplyDelete
  12. you can use the following circuit for charging your 12V 150 ah battery:

    https://homemade-circuits.com/2012/02/how-to-build-automatic-6-volt-12-volt.html

    you'll need to replace the LM338 IC with LM196

    ReplyDelete
  13. Hello sir,
    Is the power from the panel is equal to that delivered to the battery? i.e. is the current through the diodes is greater than the current from panel?

    ReplyDelete
  14. Athri, panel current should be selected such that it is around 1/10th or 2/10th of the battery Ah rating...the current through the diode will be at around this rate while chaging

    ReplyDelete
  15. Sir what I am asking is there is any power losses at the diodes?

    ReplyDelete
  16. power loss may happen if the diodes heat up, therefore make sure to use correctly rated diodes, then power loss will be minimum.

    ReplyDelete

Post a Comment