Battery charge

[camodude1954]

I have read on here, that when fully charged, a 48v system should have a little more than 50v of pack charge. Is this correct? If batteries should be charged when they get no lower than 50%, how is around 47.4 considered a 50% charge? Isn't 50% of 50v, 25v? I recently load tested and was told my batteries were pretty much shot since the number dropped from starting at 8 to end up at 7.4.

[scottyb]

Our information comes from Trojan battery manufacturing company. 50.9 is a full charge 48.4 is 50% depleted.
8.0 is 50% depleted
7.6 is 10% of capacity

Your batteries are shot.

[camodude1954]

I know you know what you're talking about, but I still don't see how they arrived at those numbers. I even just did the hydrometer test with the float balls, and they all had all 4 balls floating, indicating fully charged batteries. By the way, I just received my Scottyb meter yesterday. Just haven't gotten it put on yet. How does the instrument panel come open so that I can cut out the hole for the meter? 2001 CC DS. I know something is definitely wrong because it just keeps getting slower all the time unless you stay on flat ground. Thanks for sending the meter so fast. Everybody just raves about it on here

[JohnnieB]

Originally Posted by camodude1954

I have read on here, that when fully charged, a 48v system should have a little more than 50v of pack charge. Is this correct? If batteries should be charged when they get no lower than 50%, how is around 47.4 considered a 50% charge? Isn't 50% of 50v, 25v? I recently load tested and was told my batteries were pretty much shot since the number dropped from starting at 8 to end up at 7.4.

Batteries should be charged after each use!

For maximum battery life expectancy, you should keep them a fully charged as possible or practical.
If the cart is used periodically throughout the day, it ought to be on charge that night.

Here is the SoC vs Voltage chart from the Trojan Battery User's Guide.
Just multiple the voltage under the size battery you have times the number of batteries in your battery pack to get the pack voltage.

Originally Posted by camodude1954

I know you know what you're talking about, but I still don't see how they arrived at those numbers. I even just did the hydrometer test with the float balls, and they all had all 4 balls floating, indicating fully charged batteries. By the way, I just received my Scottyb meter yesterday. Just haven't gotten it put on yet. How does the instrument panel come open so that I can cut out the hole for the meter? 2001 CC DS. I know something is definitely wrong because it just keeps getting slower all the time unless you stay on flat ground. Thanks for sending the meter so fast. Everybody just raves about it on here

Those numbers are empirical data that were arrived at through years and years and years of observation and experimentation.

The trick is that you cannot actually determine how much energy is stored in a battery, any battery, other than by measuring what comes out of it when you discharge it. Then you only know what was in it.

Fortunately, with lead-acid batteries the specific gravity of the electrolyte is a reasonably good indicator of how much energy is stored, but only as a percentage since the Amp Hours stored depends on plate size and several other factors.
Equally as fortunate, Open Circuit Voltage closely tracks Specific Gravity.

In other words, the voltage (or SG) points to the State of Charge, which is expressed as a percentage.
In the case of deep cycle lead-acid batteries, a 0.02V change in Open Circuit Voltage or a 0.02 change is Specific gravity equates to about a 10% change in State of Charge.

FWIW: The floating ball type hydrometer, isn't very accurate, get one that actually reads numbers, and is temperature compensated.

With a DVM battery meter, you really don't need a hydrometer, unless you want to look for a bad cell in a battery, which you can't do much about anyway, other than replacing the whole battery.

Also, when measuring battery or pack voltage, wait about 12 hours after they come off charge or about 15 minutes after they have been used, to get an accurate voltage reading to determine State of Charge.

Hope this help[s more than confuses.

[camodude1954]

I do charge my batteries daily. The cart stays at the campground. First thing I do when we get down on Fri is to hook up the charger. Now we usually end up taking a ride around the campground before the charger kicks off. However, the charger goes back on Fri night and stays on until full charge has been reached. Same thing for Sat night and again on Sun up until we leave. So I don't think that's my problem. Sounds like these 6 year old batteries have ran their course. I don't know how these were maintained either, since I just bought this cart.