VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt 6 volt battery test

With the engine running, I hooked up a voltage meter to the battery terminals. The reading is between 6 1/2 and 7 volts. Is that a good thing?

Should be about 7.5 at high idle.

Thanks. I guess a low battery will not charge up to it's maximum by driving. I will have to attach the battery to my trickle charger to get it back up to the proper charge.

If you measured voltage at the battery with the engine running you actually measured generator output voltage.

The best way to measure battery voltage is to let the car sit overnight and measure it without the engine running.

I agree with Tiny. Your charging system should be providing well over 7 volts at a high idle.

A good and fully charged 6 volt battery will read about 6.3 volts.

The charging system is not designed to charge a flat battery. Must use a battery charger if it is flat. This is Delco's statement.

I know... I was told the same thing while attending a 2 year farm machinery mechanic's course, but...

I've never had a charging system that wouldn't fully charge a battery (even from stone dead) if run long enough.
I've boost started engines with completely dead batteries, done a day's work with them, and the batteries are fully charged when done.

Ask yourself, how would a battery know the difference between voltage supplied by a battery charger and the same voltage being supplied by a generator or alternator?
And as for amperage, even 5 amps will fully charge a battery... it's just a matter of how much time it will take.

My thinking as well Ole. I have done the same. I wonder if it's not recommended because of excess strain on the charging system leading to possible damage if done often?

I may be wrong but I believe the reason for using a charger for a flat/dead battery rather than depend on the alt/gen is to protect the alt/gen from overworking and thus premature failure.

I put the trickle charger on the battery for most of the day. It never got fully charged according to the Battery Butler. It did start the car with the same energy & speed as before. The volt meter read 7.1 volts after charging and the same with the engine at a high idle. What concerns me the most is the hydrometer test I did. After all the charging, there was only one ball floating which is not good. So, the plan of attack for tomorrow (going to a car show) is leave the battery where it is and put my back up battery in the trunk. This is NOT the time of the year to buy a new battery. It will sit for 7 to 8 months getting older and not being used.

After driving the car 50 miles round trip to the car show, I backed the car into the garage and it stalled. It would not re-start and had to push it the rest of the way. I looked at the battery receipt and it was purchased 11/22/21. There is a 24 month limited warranty on it, so I have to exchange it before 11/22/23. Rural King could not tell me what credit I would be receiving for the old battery until I bring it in. I guess something is better than nothing.

Driving 50 miles should have fully charged the battery. It also will heat up each connection in the circuit. Temperature increases the resistance. So I suggest inspecting and cleaning the connections before deep 6ing the battery. The ignition switch should be part of the inspection. Tapping with finger can detect some of the high resistance connections. If it is hot you will be glad you tapped first.