Bench testing with a 12v lantern battery

tmadden2 · tmadden2's Garage

For testing bulbs, fan motors, relays, and more, this 12v lantern battery setup has served me well for a couple years now. It’s been portable, cheap, and reliable. These days though, battery output has dropped to 11.5V. I’m not sure how low it can go before it stops being a useful tool. Other than using the car battery itself, any recommendations for a more robust power supply, or should I just replace the lantern battery and keep on keeping on?

dad911 · 01-30-2019, 05:36 PM

Old PC power supply.

Quickstep192 · Quickstep192's Garage

A similarly sized motorcycle battery maybe?

Solamar · 01-30-2019, 06:11 PM

I tried using a standard car battery charger, worked for some things but some of the relays (turn signal relay in particular) freaked out.

Id say time for a new lantern battery.

Brian Cameron · 01-30-2019, 09:59 PM

Search amazon.com for “variable dc power supply” - lots of adjustable lab type power supplies for $50-$80.

spoke · 01-31-2019, 03:16 AM

Quote:

Originally Posted by Solamar

I tried using a standard car battery charger, worked for some things but some of the relays (turn signal relay in particular) freaked out.

Id say time for a new lantern battery.

Battery chargers may output 1/2 wave or full wave rectified 60Hz voltage. The average voltage is above 12V but basically what it's outputting is a bunch of sinusoidal humps.

An unused PC power supply sounds like a good idea.

RDM · RDM's Garage

Given the cost, portability, flexibility and availability you've already found the optimal solution!

jpnovak · 01-31-2019, 08:07 AM

Quote:

Originally Posted by Brian Cameron

Search amazon.com for “variable dc power supply” - lots of adjustable lab type power supplies for $50-$80.

This. I have a plug in DC power supply. Works great for testing all kinds of stuff.

a 0-15V supply will cover all your automotive needs on the 911. They are about $40 .

Bob Ashlock · 01-31-2019, 08:16 AM

I always keep a rechargeable Gel battery around for these kinds of things. The good is they can be recharged when necessary, using your common battery charger. I like the Gel batteries because they can put out enough current to check all but the super heavy loads (solenoid, starter, etc.) When doing electrical work on the car, tracing wiring, etc. disconnect the vehicle battery and clip-lead in the Gel battery. That way if you short something out, your harness won't go up in smoke. When re-charging the battery, I connect a tail-light bulb in series. The bulb 'regulates' the current so you don't end up with too much current pushing into the battery from a common battery charger.

Bob Ashlock · 01-31-2019, 08:19 AM

meant to include a pic of a typical Gel battery. These are inexpensive, buy at Lowes, Home Depot. They are commonly used in alarm systems, etc.

Pazuzu · 01-31-2019, 10:56 AM

https://www.amazon.com/gp/product/B00L2M2Y5O

I use this one all the time, a bit more cost than a battery but much better. Variable voltage with a detent at 13.8V, display volts or amps (to check loads for fuse selection), 30 amp max via the banana plugs, or 10amps max via the cigarette lighter port. So many options...

tmadden2 · tmadden2's Garage

Wow - lots of great options out there. Thanks for the suggestions everyone!

spuggy · 01-31-2019, 07:59 PM

Quote:

Originally Posted by Brian Cameron

Search amazon.com for “variable dc power supply” - lots of adjustable lab type power supplies for $50-$80.

This.

I used to use a motorcycle or UPS battery - AGM ones can't leak.

However I do like being able to limit current, just in case I do anything spectacularly bone-headed.

This thing is 0-30V, 0-5A; $40 on Flea Bay:

It's plastic fantastic and hardly industrial grade, but my Fluke says it's much more accurate than I'd have bet it was. Which hardly matters, but good to know...