PIC for solar cells to lead acid gel battery charger

solar panel charger circuit lead acid

Dear Friends

I must design for my company a solar cells (17 V nominal) to lead acid gel battery (12V nominal, 14.6V charge final voltage) charger.

I want to use a PIC single chip computer with A/D and D/A-converters for regualting between solar cells and battery/load line with two cool-mosfets (these are the same as a logic level mosfets). the unit should also prevent against solar back current in the night, overcharge, undercharge and load over current.

I also must implement a battery charge measurement (in Ah), i want to do this with the PIC (measuring the battery charge/discharge current and integrating this current up/down respectively).

The surge load current is 20A or 40A, nominal load current is about 5A or 10A.

Do you have ideas, critics, questions or suggestions? I'm glad about every answer from you. I also would like to help somebody with similar questions. For a very helpful idea or a good design we would pay, if you want. Thank you very much!

Walter Nussbaum, dipl. Electronics Engineer ETH, Megasol Inc., Höhenring 17, 8052 Zürich

mail: wnussbaum@gmx.ch

phone: +41 43 268 90 32 mobile: +41 79 297 62 78

gel acid charging profile

Hi there,

Hope you dont mind me giving my two cents. I once developed a charger to charge a 12V sealed lead acid battery, I will first briefly explain what I've done and let you filter if there is any chance where I can provide useful information to you.

Mine is a PIC based dual powered, switch mode charger unit. I've developed a boost converter circuit to boost the level of voltage from the solar panel to the appropriate charging level for the 12V SLA battery. It's actually called dual powered as the boost converter (charger circuit) has the ability to be powered up using either the solar panel or the main power supply. We will just talk about being powered up by the solar panel, since that is the only aspect that you're interested in.

Briefly, the output of the solar panel will be stepped up to the appropriate level for charging purposes. The voltage level which will be stepped up by the charger circuit depends on the PIC, which will actually read feedbacks from the battery. In other words, the developed charger unit has a two-mode charging method. Whenever the voltage level of the SLA battery is low, typically, 10V or 11V, the absorption mode (13.5V) will be applied, whereas float mode (14.7V) will be applied if the SLA battery is fully charged to maintain the voltage level.

Certain configurations, using MOSFETs are done to control the reverse flow of current and etc.

Hope to hear from you. Sorry, if as mentioned above are nonsense to you.

gel battery load measure

hi dear devonsc

thank you very much for your reply.

my company, megasol inc., switzerland, would you pay a real price if you can help me effectively.

my idea is to use a PIC with two logic-level-mosfets, the 1st fet (fet1) to implement a step down = buck converter and the 2nd fet (fet2) to control the load line. the pic also must drive a display to show the charge/discharge current and/or the charge of the battery.

so the PIC sw must do:

- PWM buck regulating, can be very slow

- Ucells < Ubattery -> fet1 is closed* (prevent solar reverse curent at night)

- charge/discharge current > 40A -> fet1 and fet2 closed*

- Ubattery > 14.6V -> fet1 closed*

- Ubattery < 11.1 V -> fet2 closed*

- measure charge/discharge current, display it

- integrate charge/discharge current and display the battery charge in Ah

*always display a warning/error message

the display should be self-explaining, easy to understand also for non-profis

i would like to program in basic, pascal etc., C or assembler would be 2nd choice

yours sincerely,

walter nussbaum, megasol inc., dipl. electronics engineer eth, zürich

mail: wnussbaum@gmx.ch

phone: +41 268 90 32 mobile: +41 79 297 62 78

battery charger lead acid solar 10a

No no, its not the money that Im looking for, I believe many good ones out there that are way better than me, Im just trying to help if I can. I will check the post again and again from time to time. Real sorry as I will be away for quite a while, overseas.