Register to reply

Homemade charge controller

by damosuz
Tags: charge, controller, homemade
Share this thread:
damosuz
#1
May1-14, 03:44 PM
P: 41
I have built the following circuit which uses the comparators inside a 555 timer to control the charge of a 12 V battery from a solar panel. The circuit is adjusted (via pots R1 and R2) so that when the battery voltage gets under 12 V, the relay connects the solar panel to the battery so it charges while when the battery voltage gets over 14 V, the relay connects the solar panel to a dummy resistor so it dumps energy.

When I try the circuit with the panel outputing 15 V and the battery at 10 V, the relay swithes very fast between charge and dump. Does anyone know why?

Thank you for your help.

Phys.Org News Partner Engineering news on Phys.org
Researchers find security flaws in backscatter X-ray scanners
Virtual reality guides those whose memory is failing
Intelligent navigation system to personalise shopping trips
berkeman
#2
May1-14, 04:18 PM
Mentor
berkeman's Avatar
P: 40,944
The 555 pinout looks a bit odd to me. Where is pin 5? Have you checked that pinout against the 555 datasheet?
jim hardy
#3
May1-14, 04:47 PM
Sci Advisor
PF Gold
jim hardy's Avatar
P: 3,641
check battery voltage with solar panel directly attached.
If you have a sulfated battery it'll be greater than your dump setpoint.

http://batteryuniversity.com/learn/a..._to_prevent_it

damosuz
#4
May2-14, 03:09 PM
P: 41
Homemade charge controller

I tried with a different battery and it seems to be working. The battery I was using must have been sulfated!

Thank you.
jim hardy
#5
May2-14, 05:37 PM
Sci Advisor
PF Gold
jim hardy's Avatar
P: 3,641
Great.

Berkeman's suggestion about pin 5 was right on. 555 wants a capacitor there to smooth its internal reference .

Some capacitance from node R1-R2-R8 to common would help noise immunity.

555 datasheet suggests robust capacitance across supply near the chip for it draws considerable current during switching. The cmos versions are less rambunctious.

Nice job!
There exist "smart" analog battery charger IC's made for this job, but for a one-off hobby application yours looks fine.

http://www.ti.com/lit/an/slua115/slua115.pdf


Register to reply

Related Discussions
Battery Charge Controller using a VRDC Electrical Engineering 3
Difference Between Normal Feedback Controller and Robust Controller Electrical Engineering 3
Difference between charge, specific charge, relative charge and elimentary charge? High Energy, Nuclear, Particle Physics 1
Difference between Controller & Host Controller Computers 1
Homemade RPG General Physics 3