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Is there a simple way or is it even possible to limit voltage in the circuit of a car? Let me explain my problem, I’m experiencing voltage drop while cranking that is too low for the ECU to open the fuel injectors. I want to install a second battery in series But also install a protected device that limits the voltage to 12 V. I would install this device if possible directly off the negative terminal of the battery in my mind that would make the voltage of the two batteries 24 V accessible to the circuit, but limited to 12 V as to not damage any components, this would allow the auxiliary battery to support the circuit during cranking so that there wouldn’t be a voltage drop.

Anyway, I really don’t know what I’m talking as far as electrical engineering or anything like that and it may be something that’s not possible at all. I just wanted some feedback , thank you.

Transistor
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Hayden Black
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  • This looks like a very complex solution to a relatively simple problem. – StarCat Nov 27 '23 at 17:12
  • The vehicle was designed to work with a single 12 V battery. Is there a good reason to think that it now requires two? – GodJihyo Nov 27 '23 at 17:35
  • @GodJihyo designed and fitted a 24V start, 12V run system for a bulldozer that refused to start... Started after that :) – Solar Mike Nov 27 '23 at 18:13
  • Is there a reason that you don't just replace the battery with a new battery with a higher CCA (cold-cranking current) rating? By the way, there isn't really any such thing as "24 V accessible, but limited to 12 V"; I can't think of anything that that could reasonably mean. – Tanner Swett Nov 27 '23 at 18:13

2 Answers2

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So use a relay controlled by an ignition feed to supply the ecu from the second battery.

A split charge relay will ensure that both batteries get charged.

But I would be looking for a poor connection that is causing excessive voltage drop or running another relay controlled direct feed from the existing battery.

And also check the health of the battery - it should be able to crank while keeping sufficient voltage.

Solar Mike
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If the car circuit is designed for 12V battery then why not attach the secondary battery in parallel instead? If you connect in parallel then the voltage would stay at 12V but it would provide twice the current during ignition. Usually voltage drops are caused by current reaching its limit so if your battery is dropping its voltage just attach a second one in parallel to keep the voltage but double the current.

micropyre
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