Battery voltage (6V, 8V or 12V) vs Run-time

[JohnnieB]

I posted this in a thread that was originally here, but got moved to CC, and thought you guys might find it interesting also.

The original question was about using 8V batteries vs 12V batteries for a 48V pack.

Unfortunately, the only run-time data listed by Trojan that is common to their 6V, 8V and 12V batteries is at the 25A rate, which is only about 1/2 or 1/3 of the discharge rate used by carts, but it'll illustrate the difference.

The T-105 is the de facto standard for golf cart batteries, so let's use it to build an 8 x 6V 48V pack.
The T-875 is the mid-grade 8V, but the same size and about the same weight as the T-105.
The T-1275 is the typical 12V, but is both larger and heavier than the T-105 and T-875 so it comparing apple to oranges and the run-time is skewed upwards considerably.
The Trojan 27TMH probably isn't used in Golf carts, but it is closer in volume and weight to the T-105 and T-875 and reflects a truer difference in Run-time.

T-105 = 447 minutes @ 25A and 12.00 kWh of energy stored (0.50 kWh per cell x 24) --- Run-time = 100%
T-875 = 295 minutes @ 25A and 9.06 kWh of energy stored (0.38 kWh per cell x 24) --- Run-time = 66%
T-1275 = 280 minutes @ 25A and 7.96 kWh of energy stored (0.33 kWh per cell x24) --- Run-time = 63%
27TMH = 200 minutes @ 25A and 6.16 kWh of energy stored (0.26 kWh per cell x 24) --- Run-time = 45%

Bottom line: For maximum Run-time use the largest and heaviest batteries you can fit in the space available.

[scottyb]

Originally Posted by JohnnieB

I posted this in a thread that was originally here, but got moved to CC, and thought you guys might find it interesting also.

The original question was about using 8V batteries vs 12V batteries for a 48V pack.

Unfortunately, the only run-time data listed by Trojan that is common to their 6V, 8V and 12V batteries is at the 25A rate, which is only about 1/2 or 1/3 of the discharge rate used by carts, but it'll illustrate the difference.

The T-105 is the de facto standard for golf cart batteries, so let's use it to build an 8 x 6V 48V pack.
The T-875 is the mid-grade 8V, but the same size and about the same weight as the T-105.
The T-1275 is the typical 12V, but is both larger and heavier than the T-105 and T-875 so it comparing apple to oranges and the run-time is skewed upwards considerably.
The Trojan 27TMH probably isn't used in Golf carts, but it is closer in volume and weight to the T-105 and T-875 and reflects a truer difference in Run-time.

T-105 = 447 minutes @ 25A and 12.00 kWh of energy stored (0.50 kWh per cell x 24) --- Run-time = 100%
T-875 = 295 minutes @ 25A and 9.06 kWh of energy stored (0.38 kWh per cell x 24) --- Run-time = 66%
T-1275 = 280 minutes @ 25A and 7.96 kWh of energy stored (0.33 kWh per cell x24) --- Run-time = 63%
27TMH = 200 minutes @ 25A and 6.16 kWh of energy stored (0.26 kWh per cell x 24) --- Run-time = 45%

Bottom line: For maximum Run-time use the largest and heaviest batteries you can fit in the space available.

The T875 is several pounds lighter than the T105 = less lead = less amperage storage capacity = you guessed it, less run time.
The T1275 while physically bigger, holds a little less amperage than the 875 and there are only 4 not 6 of them in the cart = over taxed system = shorter run times and shorter useful life.

Add to this equation a battery with more lead and more storage capacity and you have found the perfect GC battery

Google the site and you will find more battery comparison threads with tons of tech/spec info.

Here is some of the info, notice that capacity and weight are absolutely tied together... when in doubt, buy the heavier battery.

6-Volt Batteries



Trojan batteries specifications
:

T-105, 447 Min @25Amps, 115 Min @75Amps, 225Ah @20Amps, 62 Lbs;
T-125, 488 Min @25Amps, 132 Min @75Amps, 240Ah @20Amps, 66 Lbs;
T-145, 530 Min @25Amps, 145 Min @75Amps, 260AH @20Amps, 72 Lbs


Exide
:

E3600, 390 Min @25Amps, 110 Min @75Amps to 5.25 volts, 186Ah @20Amps, 62 Lbs;
GC-5, 480 Min @25Amps, 135 Min @75Amps to 5.25 volts, 226Ah @20Amps, 65 Lbs;
GC2-H, 525 Min @25Amps, 155 Min @75Amps to 5.25 volts, 245Ah @20Amps, 68 Lbs;


NAPA 8144
(mfg. by Exide - equivilalent to Exide 3600)
390 Min @25Amps, 110 Min @75Amps, 186Ah @20 Amps, 62 Lbs

NAPA 8146
(mfg. by Exide - equivilalent to Exide GC-5)
480 Min @25Amps, 135 Min @75Amps, 226Ah @20 Amps, 65 Lbs


StowAway STGC2
(Mfg. by Exide for Sams Clubs - equivilalent to Exide E3600)
390Min @25Amps, 110 Min @75Amps, 186Ah @20Amps, 62 Lbs


US Battery
:

US-1800, 392 Min @25Amps, 107 Min @75Amps, 208Ah @20Amps, 56 Lbs;
US-2000, 445 Min @25Amps, 114 Min @75Amps, 216Ah @20Amps, 59 Lbs;
US-2200, 474 Min @25Amps, 122 Min @75Amps, 232Ah @20Amps, 63 Lbs;
US-125, 517 Min @25Amps, 140 Min @75Amps, 242Ah @20Amps, 67 Lbs;
US-145, 562 Min @25Amps, 154 Min @75Amps, 251Ah @20Amps, 70 Lbs;


Deka Batteries
:

GC10, (? Min @25Amps), 100 Min @75Amps, 190Ah @20Amps, 59 Lbs
GC15, (? Min @25Amps), 115 Min @75Amps, 215Ah @20Amps, 63 Lbs
GC25, 488 Min @25Amps, 132 Min @75Amps, 235Ah @20Amps, 67 Lbs


~~~~~~~~~~~~~

8-volt batteries



Trojan
:

T-860, (? Min @25A), 90 Min @56A, 150Ah @20Amps, 56 lbs
T-875, 295 Min @25A, 117 Min @56A, 170Ah @20Amps, 63 lbs
T-890, 340 Min @25A, 132 Min @56A, 190Ah @20Amps, 69 lbs


Exide E-4800
, 290 Min @25A, 110 Min @56A to 7.0 volts, 63 Lbs.


NAPA 8148
(Mfg. by Exide, similar to Exide E-4800)
290 Min @25A, 110 Min @56A, 63 Lbs.


US Battery

US-8VGC, 337 Min @25Amps, 128 Min @56A, 170Ah @20A, 64.5 Lbs.
US-8VGCHC, 345 Min @25Amps, 136 Min @56Amps, 183Ah @20Amps, 69 Lbs

Deka GC8V
, 318 Min@25Amps, 121 Min @56Amps, 165Ah @20Amps, 67 Lbs

[JohnnieB]

Originally Posted by scottyb

The T875 is several pounds lighter than the T105..............

Very minor point, but at 63 pounds the T-875 is slightly heavier than the 62 pound T-105.
It's the T-860 that is lighter (58 lb)

[scottyb]

Originally Posted by JohnnieB

Very minor point, but at 63 pounds the T-875 is slightly heavier than the 62 pound T-105.
It's the T-860 that is lighter (58 lb)

How do you explain the amperage storage capacity difference? I think, don't quote me, please. 180 vs 220

[JohnnieB]

Cell weight.
Comparing battery weights doesn't always hold true, as in this case, but when you reduce a battery (or battery pack) to 2V cells, the statement about more weight equals more run-time is always true.

The T-105 has 3 cells and weighs 62 lbs., or 20.67 lbs. per cell for 225 AH @ 20Hr rate.
The T-875 has 4 cells and weighs 63 lbs., or 15.75 lbs. per cell for 170 AH @ 20Hr rate.

While playing around with the numbers this morning, I noticed that the stored energy measured as kWh @ 100 hr rate when divided by the number of cells in the battery, correlates with the Minutes @ 75A for 6V and 12V batteries, so it can be used to estimate Minutes @ 75A for 8V batteries.

Crunching the numbers, I get:
T-860 = 77 Minutes @ 75A
T-875 = 87 Minutes @ 75A
T-860 = 97 Minutes @ 75A
(Note: T-105 = 115 Minutes @ 75A)