Linearity of discharge?

[Sofa Kingdom]

I'm sure you've covered this at some point but I don't see it in my searches. How linear or consistent is discharge from 100% to a given point? Does a pack drop quickly off 100 and slow it's descent or vice versa? Or does it just consistently drop until dead? I'm referring to a pack under load, not just sitting idle.

[Volt_Ampere]

I assume you mean pack Voltage. No it is not linear.

[Sofa Kingdom]

According to the US Battery 48v chart, my pack at 100% should read about 51.3v. At 60%, at the lowest recommended discharge the pack would be about 49v. I give 2 scenarios, which is more likely with all factors equal (flat ground, consistent throttle, weight, speed, etc)?

1. Battery pack holds around 51.3v for several miles, and then begins to drop at a noticeable rate over the next few miles and I stop at 49v and charge it.

Or

2. Battery pack drops quickly from 51.3v within first mile or two, and slowly creeps down to 49v, at which point I stop to charge it.

I am just trying to get a good idea how this should play out...

[teecro]

In my case my cart gets drove for a little over a mile of up & down hills down to the marina where it then sits for a few hours and then repeats, the voltage of the pack if given a short recovery time comes right back up to 100 % SOC on each end of the leg so that definitly not linear at all... If I continue with using the cart for more than a couple miles the drop is fairly predictable with the voltage dropping more sharply as I get toward the 10 to 12 mile worth of use. Now keep in mind that my use is all very hilly.

[ProsperDad]

So for those that don't know me (I know 2 or 3 members personally), I'm a Director level employee of the maroon deep cycle battery manufacturer discussed frequently on this site and sometimes confused for a prophylactic manufacturer.

The discharge curve of a deep cycle battery is not linear. When first applying current (putting the pedal down) the voltage drops quickly, then recovers. For a period of time (generally to 80% depth of discharge or so), the curve is fairly linear. However, from 80% to 100%, the curve starts to drop pretty dramatically.

Bear in mind, that in the last 20%, the motor has to work harder to get the remaining energy out of the battery. Also bear in mind that most carts are designed in a way so not to discharge the pack beyond ~80% depending on the cart.

This image is a basic depiction of what the curve looks like:

[Sofa Kingdom]

Exactly what I was looking for. Thanks guys!

[lockman1]

Originally Posted by ProsperDad

So for those that don't know me (I know 2 or 3 members personally), I'm a Director level employee of the maroon deep cycle battery manufacturer discussed frequently on this site and sometimes confused for a prophylactic manufacturer.

Okay, now... THAT is funny!
Never once has someone asked about batteries for their prophylactics!

But, seriously... Welcome to BGW with your first post! Trojan batteries ROCK!

[cgtech]

Hmm, looks fairly linear to me, given a predetermined load. Much Unlike lithium batteries.