0
\$\begingroup\$

i'm building a robot (a sort of rover) which includes a 12V/7Ah SLA battery. The robot circuit needs a regulated 12V supply to work correctly.

I would like to charge my rover using a generic 14-19V DC power supply.

Now the question is, what device should I use to charge the battery when this is connected to the robot circuit and at the same time regulate the output to 12V?

I found the following device, but apparently this will work only if connected to solar panel. Other than this limitation it does exactly what I want to accomplish.

Solar charger

Could you suggest a on-the-shelf product for what i need, or otherwise if simple to create the circuit that I should build?

Thanks for your time :)

\$\endgroup\$
  • \$\begingroup\$ I don't think the device pictured provides a 12V regulated output. I think it is just a connection to the battery and will be at battery voltage minus some small drop due to resistive losses. The only reason it is separate is so the controller can prevent over-discharge of the battery. So you should expect anywhere from 10.8V to 14.4V at the "12V" connection point. \$\endgroup\$ – mkeith Nov 9 '16 at 16:26
  • 1
    \$\begingroup\$ It is kind of difficult to get a regulated 12V supply from a 12V battery, because the battery voltage ranges from, say 14.4V (or even higher during certain charge operations) to some low voltage cutoff point (which is application dependent) lower than 12V. So you need a buck/boost regulator. I suggest you re-think your approach. Use a battery which is distinctly higher or lower in voltage than 12V, or figure out a way to get by without the regulated 12V rail. Could it be regulated to 10V, for example, or does it really need to be regulated? \$\endgroup\$ – mkeith Nov 9 '16 at 16:30
0
\$\begingroup\$

"...what device should I use to charge the battery when this is connected to the robot circuit and at the same time regulate the output to 12V?"

Any 12V SLA battery charger would work, however, I would recommend you ensure you have voltage protection between your charger & your robot. Charging voltages can exceed 14V and your 12V robot regulator circuit will need to handle that extra V or be isolated from the charge V during charging--if you prefer to protect it that way.

Personally, I think you'd do better using a li-ion battery as it has a higher energy density & it weighs much less than lead.

hth!

\$\endgroup\$
  • \$\begingroup\$ Some chargers perform a charge operation called "equalization" which can take a 12V battery up to 16V for a limited time period. Barring that, 14.4V is a pretty common upper voltage. It would be wise to assume at least 15V could be present on a 12V battery system connected to a charger. \$\endgroup\$ – mkeith Nov 9 '16 at 16:36
  • \$\begingroup\$ I suppose i need a 12v voltage regulator between the charger and the robot circuit. But the voltage regulator would also drop the battery voltage when the charger is not connected (from what i've seen the voltage drop is at least 1/1.5V when working with 1.5Amp load). Any solutions? Or this problem does not exist? \$\endgroup\$ – Stefano Filippone Nov 9 '16 at 16:42
  • \$\begingroup\$ @StefanoFilippone - What are the min & max V & A that your robot requires for proper operations? You could create a charging circuit that isolates the robot while the battery is charging. \$\endgroup\$ – DIYser Nov 10 '16 at 3:33
  • \$\begingroup\$ @StefanoFilippone, that is what I was trying to tell you in my previous comment. It is a pain in the butt if you need regulated 12V from a 12V battery. Sometimes you need to reduce voltage, and sometimes you need to boost. So you end up requiring a buck-boost DC-DC converter. It is much better if the regulated voltage is always lower or always higher than the battery voltage. For example if you went to 24V or 6V, it might actually be easier to produce 12V regulated. Otherwise, google buck-boost regulator. \$\endgroup\$ – mkeith Nov 10 '16 at 6:27

Your Answer

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

Not the answer you're looking for? Browse other questions tagged or ask your own question.