Am I dropping too much voltage

wheelnsniper

Quick run down. I have txt 48. Factory motor. New set of Rangers and an XCT400 with the fan (which alltrax told me is pretty much a 500. Which shocked me) anywho. I also got a DPI from scottyb. Batterys have never seen another charger. I have been consistently running them about 10-30 min a day for roughly 3 weeks. Some days no driving. Nothing heavy and charging full and leaving on the charger. Put one of scpttys meters on the pack. I had to do alot of work on farm and ran it off and on for couple hours and decided to test. At rest it always stayed at 50.5. Punching it would drop to 47.3 on flat. I went to a dirt mound that is about 15 ft tall at about 35 to 40 degrees. Ruff estimate. I would get the cart just on it and punch it. Climbed no problem but voltage dropped to 39 but jumped right back to 49 and after about a minute back to 50. Isn't that a huge drop. All connections look clean. Thoughts? Wasn't sure if batterys still new or if I have to spend more money which I want to avoid. She performs awesome. Lots of torque for what I would expect on factory motor. Again new but want to make sure all is good. Thanks again guys

Wheels

BGW

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teecro

I'm going to say your fine... Why? Mine does the same thing and has since I built it. Where I live your lucky to find a flattish section of driveway much less road so I'm always seeing voltage drops into the same 38 to 39 volts for a few seconds whereas is then starts to climb right back up as soon as the peak demand is gone.

Clemsoncartguy

I'm gonna say your rune as well. A 45° angle hill is a 100% slope. So that's pretty demanding to hurl the 1000 pound cart plus your weight and any other crap you have bolted onto it.

JohnnieB

You are seeing a mixture of things and all of them appear to be normal.

In and of themselves, the batteries in your 48V-204AH battery pack will typically drop about 1.5V per 100A of current draw. The voltage drop occurs almost instantly, but when the current flow stops or reduces, the voltage recovery happens over several minutes. Actually, full recovery take an hour or more, but it recovers at an exponential rate and most of it occurs in the first few minutes.

Then there is the intrinsic resistance in the amp deliver system (High-current cables, high-current connections and high-current contacts) that will drop up to another 1.0V, or so, per 100A of of current draw. The voltage drop across this resistance both occurs instantly and recovers instantly.

Since new batteries don't reach their rated storage capacity until the have be recharged a couple dozen times, the amount of voltage drop you are seeing now may lessen a bit as the new batteries mature.

Volt_Ampere

That sounds normal to me also. You are seeing both battery and cable drop. You pull max current when you ask the cart to go up a hill at full throttle. IMO the voltage drop will not improve with battery age. It eventually gets worse as battery impedance goes up with age.

Helirich

What is the cut off voltage on the controller? I have a hill just like you discribe in the back yard. Ive never looked at the voltage while climbing it. But I've never seen the voltage in the 30s.

My cart is similar to yours except for non stock motor. One time I ran the battery down around 49 at rest. When I punched the pedal it quit. Then worked a moment later. I assumed the voltage dropped too much, but it was still in low 40s. I never checked what the cut off voltage is set at on my 500 XCT.

I will watch the voltage on my hill today and report back.

JohnnieB

I agree.

I made a qualified statement based on new batteries increasing in storage capacity by up to about 25% during the first few charge cycles, but I'm not sure if the battery impedance decreases during the break-in period.

If it doesn't, the voltage drop per 100A would be about the same when new and when broken in, and increase as they age.

hubtech

i've got a voltmeter i'm installing today, i'll do this test too. i know my batteries need to be replaced, but i'm interested to see what the drop is. our hood is HILLY

JohnnieB

I cheat and use a DVM with a min/max function so I can capture how far the voltage drops without taking my eyes off what's in front of the cart.

One thing to keep in mind is that you don't want to load the batteries below 1.5VPC (Volts per Cell). That is were irreversible physical damage to the plates starts occurring.

The problem is measuring/monitoring the actual battery voltage. What we typically measure is the voltage drop of the batteries plus the voltage drop of the cables & connections, so when the pack voltage of a 48V pack is loaded down to 36V (1.5V x 24 cells), the 2V cells are actually above 1.5VPC.

Attached is a grade chart. Estimating how steep inclines are is very subjective.

Attached Images

Grade conversion chart.jpg (167.3 KB, 0 views)

Helirich

I tried the hill today. It's every bit of 45 degrees. Its tough to not pop a wheely. I got the cart right off the charger. It was reading 51.7 volts. I went up the hill slow. The lowest reading was 44 volts.

This brings up another question. When I'm on the flat and floor it, it goes to 44 volts. But on the hill I only had the pedal at half throttle. (I can't go full throttle or it would go over backwards or launch for the moon) Anyways, does that make since? I would think the pedal has to be on the floor to drag the voltage down the most.