Help me make a simple charging circuit for a motorcycle battery

[archiees]

Hi Guys,
My motorcycle battery just died. It shows 9 volts instead of 12 volts. I need to rig up a simple charging circuit in the lab.
I have dc power supplies and resistors and some npns.
Please help

 

[jorgito]

Urgent help

Hello,
If you have a variable power supply, set voltage to 14.2 V. Limit current to 10% of the battery capacity.
Let it charge some 10 to 12 hours.
Good luck!

I almost forgot it! Safety first!
The charge process may generate Hydrogen. Don't try this without adecuate ventilation.

 

[archiees]

Re: Urgent help

Thanks Jorgito,
I have connected the battery in parallel with a regulated dc power supply i have. The bike manual says that to keep the charging rate 1.1A X 10hrs. So i have limited the current from my power supply to 1.1 Amps. Though the voltage is only 12.6 volts.
If i want to increase my voltage, my PS goes in CC mode, preventing me to do that. I don't want to increase my current limit as its the rated charginrate. I guess i will keep it charging for approx. 4 hrs or so and try to start the bike. Hope it wil work.

 

[echo47]

Urgent help

You can set the voltage limit to 14.2V and the current limit to 1.1A.

If you are in a hurry, you can go several times higher than 1.1A. 10% is a conservative charge rate.

At first, you will see low voltage and current limiting. The voltage will gradually rise to 14.2, and then the current will gradually fall. When the current reaches a couple hundred milliamps, the battery is pretty full. At that time, either disconnect the charger or reduce its voltage to between 13.5 and 13.8 (that's a safe "float voltage" which can be applied forever).

 

[omore]

Re: Urgent help

An additional TIP

You can recover the bat discharguing it but checking that the voltage does not fall under 11V then chargue it again. Sometimes, this cycle must be repeated several times