I Have HBL power system's 2cell 4.2v lead acid battery which has capacity of 12Ah for C/ 100 and 9Ah for C/10.

I found it in the rubbish and thought it may useful and in working condition.I refilled it with dilute sulphuric acid.

I charged it with smartphone charger at 5.06V at 400 to 500mA .When it is charging it produces very small bubbles of gas. I think I am charging it at the gassing voltage.

Is it OK to charge it at 5V? If not than its OK to charge it using LM317 at fixed safe voltage or just use small resistor? Or use a low drop P channel linear reg? its this big and transparent

  • 1
    \$\begingroup\$ Please don't. You are boiling away oxygen and hydrogen gas due to too high voltage, which is a mixture as explosive as it gets. Replace the lost water with distilled water and get a propper carger. In your case it will be difficult to find one but a variable power supply with current limit, set it for 2.4 V 1 A and terminate the charge manually comes to mind. You must limit both voltage and current! \$\endgroup\$ – winny Jan 15 '17 at 12:13
  • 1
    \$\begingroup\$ @winny 2.4V/cell? \$\endgroup\$ – RoyC Jan 15 '17 at 13:48
  • \$\begingroup\$ @RoyC Yes. For 12 V it's 14.4 V current limited, say C/10 to be on the safe side. Wait until current is 10% of initial current. Terminate or float short term to 13.6 or long term 13.2 V. \$\endgroup\$ – winny Jan 15 '17 at 16:20
  • \$\begingroup\$ @winny, this is a two-cell battery. So that would be charge using CC/CV supply at 1A, 4.8V. Note that since this is already C/10, as soon as it drops out of CC mode into CV mode, that would be the point where you would switch to the lower float voltage. 13.2V for a 12V battery would translate to 4.4V for a two-cell battery. \$\endgroup\$ – mkeith Jan 16 '17 at 18:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.