How to check for voltage, Load or no load?

[Wjackson11x]

When checking voltage on a battery pack or even a single battery, Should I be checking voltage while under load or with the cart sitting still. The reason I ask is that with a fully charged pack, I get 39.4 volts with the cart sitting. According to the state of charge chart I should be getting around 38.2 volts. I just want to be able to check the state of charge properly and get an accurate reading. That way I can keep the pack above 50% charge.

[scottyb]

On a 36v cart the automatic charger cut off voltage will be around 43v (plus or minus) but if you nave a DVM connected you will see the voltage quickly drop off after the charger shuts off. This is called settling. The battery pack voltage settles downward to a voltage that the pack can actually hold and deliver for use. This settling can take 12 -24 hours. at about 12 -16 hours you can expect to see numbers very close to what is on this State of Charge Chart. Hope this helps

[Wjackson11x]

Thanks Scotty, when checking the voltage to check for %, should I check it while riding or just check it while sitting still. Which is the accurate reading? And what is a DVM? Digital Voltage Meter?

[Andy4639]

The readings in the chart are for after a full charge and the battery sitting for at least 12 hrs. Do not use the battery during this time.

[scottyb]

I have one DVM (digital voltmeter) with large clip on leads, I use this to watch the pack under load. Under load ( while driving) is the easiest way for most of us to verify the good health of a battery pack. If you have a little hill you can watch the meter go down under load and recover at rest.
Short of a draw down machine this and the hydrometer are the best tool I own for battery analysis. It really takes all three tests to determine the condition of a battery.
1= Standing voltage after a settled
charge.
2= hydrometer readings with particular attention to the difference between cell readings in a given battery
3= voltage drop under load. Look for excessive drop. If you have an excessive drop ( greater than 20% of total voltage from a fresh pack) under load then work the pack pretty hard for a while and re-check all individual battery voltage ... chances are the weak or bad battery will have a much lower reading than the rest of the bunch.... if you have one.

[Wjackson11x]

Thanks guys!