I've got a small ac delco battery that is "fine" according to my mechanic. It is holding a full charge and I can't remember the number he told me.
However, I have had some symptoms which make me wonder. The symptoms are:
1.dash lights which are usually kinda dim get even dimmer when at low idle but brighten when I accelerate.
2. new head lamps and relay wiring (courtesy of SSDan) which are awesome when the rpms are up over 1000 or so but a bit dim at idle
3. if I play the stereo loud enough to really hear it at 50 mph w/top down the lights dim as well but mostly on the dash and not Dan's badass lamps.(yes it is December in CA and my top is down at night. And yes its been this way here for all of my 35 years here)

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'64 valiant convertible 225/6

It's not the battery.

1 & 2: At low rpm the old design alternator doesn't put much amps, so the battery supplies the power and the voltage drops until the alternator spins up.

3: Turn the volume down so your stereo doesn't draw as much power..........

3a: Depending on where you tapped into the system for the stereo's power, that circuit was probably not designed for the current you're drawing. Run a separate power line for the radio from another circuit that can handle the power.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

The standard battery size is a Group 24 but they can be found in a wide variety of current capacities. As the previous post indicates, however, the problem is not the battery, it is the alternator. You can upgrade to a newer alternator that will out put more amperage and, perhaps more impotatnly, put it out at lower engine speed. If it were me I would probably just ignore it though as it's unlikely to do any harm. It's more of a minor annoyance than a problem.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

I just replaced the VR and the alternator as well as the belt. I also put in Dan Stern's lighting with the nicely built wiring and relays. I'm simply wondering if I have too small a battery...I'll try the one in my doggie van (I'm a dog walker/trainer with a 15 pass club wagon) it has a big battery for comparison if you all think its safe to do so?

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'64 valiant convertible 225/6

Measure the voltage at various rpms with and without lights.

Was the alternator a larger capacity one?

If not, another battery isn't going to change things.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

The alternator I installed was a remanufactured one from Napa. It is a 60 amp unit I believe which according to Dan it should be plenty. Also, my stereo is a stock 2005 pioneer that has a 10 amp fuse built in. It seems odd that such a small amount of electical need isn't being met...yet.

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'64 valiant convertible 225/6

60A refers only to the MAXIMUM amount of current the alternator can produce. Not to the output it produces at engine idle. The second gamble you take when buying remanufactured alternators is getting one that charges poorly at idle due to mismatched stator and rotor (the first gamble is getting a thrown-together one made out of shoddy parts).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

The best thing to do is to take your old alternator to a local, trusted electrical shop and have it rebuilt. Most of the time all it is is a blown diode

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2