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I have the following setup

30W 12V solar panel connected to 260W solar charging controller connected to 12V 7Ah AGM battery

I would now like to use my 60Ah car battery to charge the 7Ah AGM battery. Can I just connect it to the charging controllers input instead of the solar panel?

spec sheet of the controller:

  • Rated voltage: 12 V/24 V car identify
  • Rated Current: 20 A
  • Max. PV Voltage: 50 V
  • Max. PV input power: 260 W (12 V)/520 W (24 V)
  • Working temperature: -35 °C to + 60 °C Standby current: < 10mA
  • Float charge: 13.7 V (Standard, adjustable)
  • Discharge: 10.7 V (Standard, adjustable)
  • Discharge plug: 12.6 V (Standard, adjustable)
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closed as off-topic by PeterJ, Dmitry Grigoryev, Dave Tweed Jul 5 '18 at 13:05

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – PeterJ, Dmitry Grigoryev, Dave Tweed
If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ This is dependent on the design of the charging controller. It may not like a voltage as low as 12 volts at the input OR it may be fine and boost that 12 volts sufficiently to produce a voltage of circa 14 volts to charge your 7 Ah battery. \$\endgroup\$ – Andy aka Jul 4 '18 at 13:15
  • \$\begingroup\$ You may but if it tests for Isc, Voc, you should not. \$\endgroup\$ – Sunnyskyguy EE75 Jul 4 '18 at 13:23
  • \$\begingroup\$ @Andyaka I have added the specs of the controller if that helps \$\endgroup\$ – Chris Jul 4 '18 at 13:25
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    \$\begingroup\$ @Chris this is where this site has a problem with this sort of question... I'm guessing that the charge controller is a bought-in item and you don't have access to schematics. Without schematics, it's guesswork. That is why this site can close questions like this down because it relies on intimate design knowledge of the THING and questions on commercial electronic devices are regarded as off-topic. I already notice that you have had one "close-vote" on this basis alone so unless you can provide schematics you are undone! \$\endgroup\$ – Andy aka Jul 4 '18 at 13:30
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Put a light bulb in series with input and try it out. That will current limit the source but probably undervoltage. You can use a halogen bulb then a small resistor and with confidence, move towards a direct connection.

Status LED's will help you diagnose. But your risk.

enter image description here

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