Distance / Discharge Amt / Summit 2 Data

[Texasbass]

I’m trying to figure out how far I can go in our new 2014 TXT. It’s got the Scottyb XCT400 package with (6) 8v 170 ah Superlex batteries (supposedly 2 years old).

Yesterday we went about 4.5 miles on fairly flat terrain. My digital voltmeter said 50.5v when i plugged it in. Per the voltage chart that would mean it discharged 10% or 17ah discharged (170x.1). Below is the data from the Summit 2 charging session. It shows initial voltage of 50.6 final voltage of 59.4 and AH Return of 52.8 ah! That would mean the batteries discharged 31%. (53/170).

Any insight on how to decipher the info below? Thanks.

[yurtle]

I'm posting a spreadsheet that JohnnyB created. I've not used it, but the instructions seem clear enough.

Question for JohnnyB,

I assume before and after voltages are "at rest", so 12 hours after charging completion and an hour or so after stopping?

[JohnnieB]

Battery charging is considerably less than 100% efficient and AH returned is typically about 120% to 150% of AH discharged.

The voltage at the start of the charge cycle is the best indicator of how much the batteries were discharged and that is iffy.

IF the charger was connected to the cart within half an hour of the 4.5 mile trip, 50.6V it will be artificially low since the battery voltage hasn't had sufficient time to recover from being under load (amps being drawn).

However, IF 50.6V is a valid At-Rest value, and 4.5Miles was the exact distance traveled and IF your batteries are true Trojan clones (SoC chart is for Trojan batteries), then your cart has an estimated range of 32 miles, which is unlikely.

[JohnnieB]

Originally Posted by yurtle

I'm posting a spreadsheet that JohnnyB created. I've not used it, but the instructions seem clear enough.

Question for JohnnyB,

I assume before and after voltages are "at rest", so 12 hours after charging completion and an hour or so after stopping?

The surface charge has very little energy in it, so starting the test before the batteries have rested 12 hours makes very little difference, especially if the distance traveled for the test is 10 miles or more.

Each battery pack is different and how heavily the batteries were loaded at the end of the test run influences how long of a recovery time is needed, but an hour takes care of most of the variables.

Another often overlooked fact is battery temperature. (Not air temperature - Batteries have a huge thermal mass and will lag air temperature by several hours)

[Texasbass]

Will check the spreadsheet out later tonight. I plugged it in about 4-5 hours after the ride. The distance is almost exact because I used google maps to check distance of trip. Temp was in high 80s during ride and mid 70s during charge.

[cgtech]

I agree that AH delivered to lead batteries during charge is considerably higher than energy delivered during use. Heat losses are a ***** that you can't avoid. If we could avoid heat losses, perpetual motion machines would have been commonplace many, many years ago. Every electric vehicle on the road would only need to be plugged in once every 2 months (only due to fricton losses from the tire to the road)

[Texasbass]

That spreadsheet is great. Thanks gents. I’m going to do a few more trips and see if i can get a few projected range values that are close together.

[JohnnieB]

Originally Posted by Texasbass

That spreadsheet is great. Thanks gents. I’m going to do a few more trips and see if i can get a few projected range values that are close together.

The longer the distance traveled during the test, the more accurate the range estimate.

Tips for getting max range with a Sepex drive:
Avoid jackrabbit starts. Rapid accelerations eat amp-hours.
Fill tires to max allowed inflation pressure.
Cruise at about 70% to 80% of max top speed.
Avoid creeping along at low speeds. Try to stay above walking speed.
(Motor efficiency drops off at low and high end of RPM spectrum)
Use regen braking whenever possible. (Puts AH back into batteries)

Have fun.

[Texasbass]

Originally Posted by JohnnieB

The longer the distance traveled during the test, the more accurate the range estimate.

Tips for getting max range with a Sepex drive:
Avoid jackrabbit starts. Rapid accelerations eat amp-hours.
Fill tires to max allowed inflation pressure.
Cruise at about 70% to 80% of max top speed.
Avoid creeping along at low speeds. Try to stay above walking speed.
(Motor efficiency drops off at low and high end of RPM spectrum)
Use regen braking whenever possible. (Puts AH back into batteries)

Have fun.

Good tips. Thanks Johnnie B.

[Texasbass]

So yesterday I started with a full charge at 51v drove 5 miles over 2 trips and by the end of the day after 1.5 hour rest the batteries were at 50.5v. The weird thing is that after the first few miles, when I go full throttle from the start the volt meter will go down to 38-39v. My understanding is that isn’t good. Is that evidence of weak batteries?

Thinking about just biting the bullet and getting new Trojan rangers. Never worry about distance again.