 Electrical Testing - No Engine |
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| DennisV |
  Aug 27 2025, 09:06 PM
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#1
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Senior Member  Group: Members Posts: 724 Joined: 8-August 20 From: Santa Rosa, CA Member No.: 24,575 Region Association: Northern California 
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Will I do any damage if I drop a battery in a car that has no engine or transmission? I'd like to test the electrical system (i.e., lights, dash, horn, etc.)
Are there any cables, wires, or fuses that I would need to remove or tape off before connecting the battery? The engine harness is also currently out. I realize without the generator, there will be nothing to charge the battery. I will get a battery tender. Thank you. P.S. I read that this Optima Redtop 35 was recommended, but their online fitment tool doesn't agree. In fact, it says "OPTIMA DOES NOT CURRENTLY OFFER A BATTERY IN YOUR SIZE" when I enter 1970 Porsche 914-6. |
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Replies(1 - 8)
| Superhawk996 |
Aug 27 2025, 11:00 PM
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#2
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914 Guru Group: Members Posts: 7,392 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch
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Would be far wiser to do it using a current limiting power supply. That way if you have an unanticipated short somewhere, you’re not dependent on a smattering of fuses to protect the wiring.
If you don’t want to spring for a cheap power supply, you could use the battery but I’d fuse the battery down to something on the order of 5 amps at the initial connection. You can upsize the fuse gradually as you prove out wiring and add load. A unfused battery is capable of smoking wiring before you can even disconnect it. |
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| GregAmy |
Aug 28 2025, 06:23 AM
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#3
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Advanced Member Group: Members Posts: 2,564 Joined: 22-February 13 From: Middletown CT Member No.: 15,565 Region Association: North East States
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^^^ good points.
Even spending $13 for a 60A breaker should cover any major shunts. The individual circuits *should* be protected by the fusebox: https://www.amazon.com/dp/B06Y5279ZH?th=1 |
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| DennisV |
Aug 28 2025, 06:54 AM
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#4
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Senior Member Group: Members Posts: 724 Joined: 8-August 20 From: Santa Rosa, CA Member No.: 24,575 Region Association: Northern California
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QUOTE(Superhawk996 @ Aug 27 2025, 10:00 PM)  If you don’t want to spring for a cheap power supply, you could use the battery but I’d fuse the battery down to something on the order of 5 amps at the initial connection. You can upsize the fuse gradually as you prove out wiring and add load. Good idea. I see I can get a 12 AWG holder with blade fuses for $4. Cheap insurance. |
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| IronHillRestorations |
Aug 28 2025, 08:12 AM
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#5
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I. I. R. C. Group: Members Posts: 6,865 Joined: 18-March 03 From: West TN Member No.: 439 Region Association: None
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First remove all the fuses and add them back one at a time, checking each circuit before going to the next fuse.
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| Spoke |
Aug 28 2025, 08:45 AM
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#6
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Jerry Group: Members Posts: 7,248 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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If you don't have the heavy red wire to the starter connected at the starter, make sure all dangling wires have their connectors taped up well.
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| Flyinlow |
Sep 15 2025, 06:23 PM
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#7
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Flyinlow Group: Members Posts: 87 Joined: 17-October 20 From: British Columbia, Canada Member No.: 24,774 Region Association: Canada
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QUOTE(Superhawk996 @ Aug 27 2025, 10:00 PM) Would be far wiser to do it using a current limiting power supply. That way if you have an unanticipated short somewhere, you’re not dependent on a smattering of fuses to protect the wiring. If you don’t want to spring for a cheap power supply, you could use the battery but I’d fuse the battery down to something on the order of 5 amps at the initial connection. You can upsize the fuse gradually as you prove out wiring and add load. A unfused battery is capable of smoking wiring before you can even disconnect it. Question… could this be done using a battery charger on a 10 amp setting and a fuse say 40 amp? |
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| Superhawk996 |
Sep 15 2025, 06:40 PM
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#8
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914 Guru Group: Members Posts: 7,392 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch
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QUOTE(Flyinlow @ Sep 15 2025, 08:23 PM) QUOTE(Superhawk996 @ Aug 27 2025, 10:00 PM) Would be far wiser to do it using a current limiting power supply. That way if you have an unanticipated short somewhere, you’re not dependent on a smattering of fuses to protect the wiring. If you don’t want to spring for a cheap power supply, you could use the battery but I’d fuse the battery down to something on the order of 5 amps at the initial connection. You can upsize the fuse gradually as you prove out wiring and add load. A unfused battery is capable of smoking wiring before you can even disconnect it. Question… could this be done using a battery charger on a 10 amp setting and a fuse say 40 amp? A 40A fuse protects nothing. With a 40A fuse, a short on a 16 or 18 gauge wire will melt it and it won’t bother to blow the 40A fuse. Fuses are meant to protect wiring - not equipment. I wouldn’t want to depend on the battery charger to limit the current. I’ve seen chargers that deliver way more than rated capacity to a dead short. |
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| Flyinlow |
Sep 15 2025, 06:42 PM
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#9
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Flyinlow Group: Members Posts: 87 Joined: 17-October 20 From: British Columbia, Canada Member No.: 24,774 Region Association: Canada
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QUOTE(Superhawk996 @ Sep 15 2025, 05:40 PM) QUOTE(Flyinlow @ Sep 15 2025, 08:23 PM) QUOTE(Superhawk996 @ Aug 27 2025, 10:00 PM) Would be far wiser to do it using a current limiting power supply. That way if you have an unanticipated short somewhere, you’re not dependent on a smattering of fuses to protect the wiring. If you don’t want to spring for a cheap power supply, you could use the battery but I’d fuse the battery down to something on the order of 5 amps at the initial connection. You can upsize the fuse gradually as you prove out wiring and add load. A unfused battery is capable of smoking wiring before you can even disconnect it. Question… could this be done using a battery charger on a 10 amp setting and a fuse say 40 amp? A 40A fuse protects nothing. With a 40A fuse, a short on a 16 or 18 gauge wire will melt it and it won’t bother to blow the 40A fuse. Fuses are meant to protect wiring - not equipment. I wouldn’t want to depend on the battery charger to limit the current. I’ve seen chargers that deliver way more than rated capacity to a dead short. Thanks |
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