battery not up to the job?

[swiftdrivr]

The battery in my DB-1 is showing 12.3 V at the jump plug. First race will be VIR, so I have some time. Should I replace it?

[TimH]

It may be fine, but you need to load test it.

[EYERACE]

Now this will fry mine of course..........because we all know the way things really work.

The gel cell in the VD is maybe 5+ years old ??? ...it's on the trickle charger 24/7 garage or track.

At track, first start of the race day uses a jump lead-acid 12V, once the engine's warm, for the rest of the day I start on the gel only - on grid or after impound. On track the dash may read 11.9V for a single moment but the rest of the time at speed things read 12.3 or 12.5 or something pleasant. Race over? .....right back on trickle.............

[Lotus7]

You can't judge a battery by simply it's voltage reading (unless it reads a single-digit number, then it's likely done).
Really need to put a load tester on it. Or a smart charger that can tell you its health.

Subjectively, does it spin the engine over as enthusiastically as it always has?

[swiftdrivr]

how do I load test, and what do I look for?

[Steve Demeter]

There are load testers, that basically put a big resistor across the terminals and measure amps and voltage drop.

Or an easier way is to start the car multiple times and if it starts cranking slowly, time for a new battery.

[swiftdrivr]

I don't have a load tester, but I do have a starter button

[JHerscher]

Hey Jim

Look for a device called a battery percent of charge meter. I think I got mine at a boat store; you can also probably find them at other stores or online. It puts a resistor across the terminals and tells you the health of the battery. Two batteries with identical voltage can give different percent of charge readings.

Not too expensive, maybe $20 several years ago?

Roughly the size of a small multimeter so it goes to the track even with my rig.

John

[DaveW]

https://www.amazon.com/Schumacher-BT.../dp/B000AMBOI0

That's what I use.

[mark elder]

For some more money, I use this

Projecta Battery Carbon Pile Load Tester 12v 500amp - Mr Positive NZ

The smaller one in the post above puts a 100amp load. This one (and similar) have an adjustable carbon pile that you set to match the CCA of your battery (0-500amps load). There are models that put up to 1000amp load.

You load the battery for, say, 15-20 seconds and look at the voltage drop.

The bigger the load, the harder the test.


For me, my load tester has always been 'right' (and given me good advice); its a good thing to own. Buy one.