Is something draining my batteries or am i expecting too much out of them

[wingnut2000]

I just installed 6 8volt Trojans in my RXV a couple weeks ago. I don't know if I am expecting too much out of batteries or if something maybe draining them or if my SOC battery meter isn't accurate.

I drive about 3-4 miles and it shows 88%-90% just seems like not very much range for that percentage drop.

[Sir Nuke]

Do they go down and stay that way? If you go for a ride....then come back about 10 minutes later and check...they should recover to nearly full charge.

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[NCPW]

Are we talking about a digital voltmeter or a bar meter?

[wingnut2000]

Originally Posted by Sir Nuke

Do they go down and stay that way? If you go for a ride....then come back about 10 minutes later and check...they should recover to nearly full charge.

Sent from my SAMSUNG-SM-G930A using Tapatalk

it will go back up after sitting a few but pretty sure it will just go back down to where it was in a few minutes

[wingnut2000]

Originally Posted by NCPW

Are we talking about a digital voltmeter or a bar meter?

the meter I installed has a bar and digital reading

[JohnnieB]

Originally Posted by wingnut2000

it will go back up after sitting a few but pretty sure it will just go back down to where it was in a few minutes

SoC (State of Charge) is estimated from the At-Rest voltage. To get a true At-Rest voltage the batteries have to rest (Neither being charged nor discharged) for about 12 hours after charging and for about an hour after discharging.

The battery voltage of lead-acid batteries drops almost instantly when amps are drawn from they, how far the voltage drops is determined by the rate the amps are drawn, the storage capacity of the batteries and their SoC at the time.

New batteries only have about 75% of their rated storage capacity until they are broken in, so that may be part of the reason they drop so much so fast.

Trojan Battery has 8V batteries with 160AH, 170AH, 190AH and 204AH. What AH batteries do you have.

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To get a reasonably accurate estimate the range potential, start with a fully charged battery pack, drive the cart for a known distance (Use a GPS to measure distance) and determine the end SoC after the batteries have rested for an our after the trip. Divide the drop in SoC by the miles traveled to get the %SoC per mile. Then divide 50% (Which is the max recommended discharge for your battery pack) by the %SoC per mile to get a max range estimate.

Based on the miles and %Soc given in Post-1, you now have a range of about 20 miles, which should increase to about 25 mile when you batteries are broken in properly and the is about 72 holes of golf on a single charge.

[kernal]

I'm going to suggest this may be an interpretation issue. The problem is trying to use the digital meters (instantaneous) as a gas gage. As we all know, the battery voltage fluctuates while driving. When you stop driving the batteries are at a lower voltage than their true at rest voltage. They need some time to recover if you are wanting to estimate range. Kind of the opposite of the top charge present just after the charger shuts off during a charge cycle. So I submit if you want to use the instantaneous digital gages to estimate range you have to give the batteries some time to recover to their true resting voltage after parking the cart. In past posts, JohnnieB has reported some testing in this regard and as I recall he stated the batteries will recover most of the voltage in about 15 minutes and the reading won't change much even after several hours. At least that's what my stupid brain remembers so I use 15 minutes. But the point is you should pick some time after the cart is parked to note the voltage and use the same amount of time always. Then go to the chart to estimate % of battery used for the miles driven.
Another issue is unique to the RXV. The OEM SOC meters get their data from the controller. If you change the factory gage to another "plug n play" gage you are still getting battery data from the controller, in other words what the controller "thinks" is the SOC of the battery. Perhaps Bob Boyce can comment on this but in my area there are hundreds of RXV's in use and there has been a consistent problem of the factory SOC meters appearing to work normally then all of a sudden dropping from a little above half to empty in a matter of a couple of minutes. Seems to be a bigger problem on the 12v battery carts and in the winter (Atlanta "winter"). I have seen multiple instances of this myself. For that reason I don't use the factory SOC gage or any version of it. I use the common digital meter and the much maligned segmented LED gage made by Curtis hooked directly to the battery pack because it works well for me and the women that use my cart absolutely refuse to even look at the (always) cycling digital meter. They want a gas gage like a car.

Wingnut: Here are some examples of ranges I have logged on my RXV with 6x8 Trojan 875 batteries.
April 19, 2018; 11.28miles, average speed 13.4mph. max 25.4, voltage after 15minutes rest: 50.4

May 6 2018; 22.8 miles, average speed 11.3, max 25.3, voltage after 15 minutes rest: 49.4

Batteries are 2 years old. Lester Links charger

edit: Was typing this as JohnnieB was posting. If I have misinterpreted anything from his past posts I'm sure he will point it out. I have used the formula he suggests and have found it accurate.

[JohnnieB]

Originally Posted by Sir Nuke

Do they go down and stay that way? If you go for a ride....then come back about 10 minutes later and check...they should recover to nearly full charge.

Sent from my SAMSUNG-SM-G930A using Tapatalk

FWIW: In 10 minutes the SoC will only recover about 73% of the full recovery.
At 15 Minutes it is 85%
At 20 Minutes it is 88%
At 30 Minutes it is 92%
At 60 Minutes it is 100% (Or at least I didn't see any further recover after an hour in the testing I did with my 42V-245AH battery pack)

[kernal]

Well, there ya go. Just confirms my advancing age is interfering with memory.

[JohnnieB]

Originally Posted by kernal

Here are some examples of ranges I have logged on my RXV with 6x8 Trojan 875 batteries.

April 19, 2018; 11.28miles, average speed 13.4mph. max 25.4, voltage after 15minutes rest: 50.4

Range estimate based on above numbers = 49.0 Miles.

May 6 2018; 22.8 miles, average speed 11.3, max 25.3, voltage after 15 minutes rest: 49.4

Range estimate based on above numbers = 36.2 Miles.


Batteries are 2 years old. Lester Links charger

As you see, the range estimates can vary considerably.
Effected by terrain, type of surface tires are traveling on, weight, wind, temperature, speed, distance traveled and several other factors.

When I do range estimates to see how much my batteries have aged, I use the same course/distance/weight/acceleration/speed as much as possible and adjust for battery temperature. (Battery capacity varies with temperature) Keeping everything as consistent as practical, I can still get a 10% or so variance on successive days.

I haven't check this year yet, but last summer when my batteries were 4 years old, they were still at about 90% of their new capacity. Of course, I using 245AH batteries, which far exceed the AH needed for the relatively short trips I take, so my average SoC is mighty high.

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I didn't see anything in your post that waved red flags.