36v vs 48v performance

[JohnnieB]

Originally Posted by mrphilf

1. This is the problem with my only knowing enough to be dangerous. I based running it before charging based upon the voltage reading as compared to a state of battery charge chart I had gotten from here when I bought my 36v batteries...by the 48v reading on that chart and the one above I was above 100% so my dumb a$$ figured they were good...oh well.

2. Anyway DPI charger came today, its plugged in and charging.

3. So onto my next confusion...according to Scotty's battery break in procedure for the first 20 charge cycles I should run the batteries down to 75%...JohnnieB says keep the charger on at all times when not using. Is this after the initial 20 charge cycles?

4. Also how long do I need to leave the cart sit before determining its SOC so as to know if I am at 75% or not?

1. In all honesty, you probably didn't hurt the new batteries all that much. They did have a fairly high residual charge from when they were formed, you didn't load them down below 1.75VPC and you didn't discharge them below 80%.

The really bad stuff happens when the batteries set on the shelf for several months and the forming charge has depleted considerable and the pedal is slammed to the floor to see what the cart will do with the new batteries. If the voltage drops below 1.5VPC, (which is easy to do since the AH capacity is only about 70% to 80% if the rated capacity and the SoC is less than 100%) lead can actually be ripped off the plates under those circumstances.

2.

3. The 75% is a limit rather than a goal. You shouldn't discharge the batteries below 75% SoC for the first couple dozen charge cycles, but you don't have to take them down to 75% SoC before recharging.

Everybody uses their cart differently, some people make long trips and others make short trips.
If you make long trips, limit yourself to discharging to 75% SoC before recharging.
If you just make short trips, recharge after each use, however during the break in period, deliberately make a couple longer trips and discharge the pack down to about 80% to 75% SoC.

Basically, the batteries should only be lightly discharged until they are broken in. If your normal routine only lightly discharges the pack, no need to change the normal routine other than taking a couple longer trips. If your normal routine typically discharges the pack to less than 75% SoC, limit your trips to 75% Soc.

BTW: The longer trips could be several short trips in the same day, just don't let the batteries sit overnight in a partially discharged state.

4. The voltage will continue to rise for over an hour after the cart stops, but most of the increase occurs in the first half hour and much of it occurs in the first 5-10 minutes, so it depends on how accurate of a SoC estimate you want to get.

When I'm out and about and want to know what the SoC is, I typically wait until the 0.1V digit on my dash mounted DVM battery meter stops climbing faster than 0.1V every 10 seconds, or so. I know the SoC estimate will be a bit lower than what is actually is, but a low estimate is on the save side.

When I'm doing things that require greater accuracy, such as maximum range estimates, I wait at least 30 minutes.

[mrphilf]

Thanks for all the help Johnnie! Hopefully after battery break in is done I can finally be done tinkering with this thing and move onto a new project that I know more about lol. Although unless the batteries get a whole hell of a lot stronger it seems like this build is just not going to live up to expectations :(

[JohnnieB]

Maybe something is holding it back.

What D&D motor?
What Cart body type?
What Controller?
What Cables?
What Solenoid?
What F/R switch?

[scottyb]

Originally Posted by JohnnieB

Maybe something is holding it back.

What D&D motor?
What Cart body type?
What Controller?
What Cables?
What Solenoid?
What F/R switch?

And what were your expectations?

[JohnnieB]

Originally Posted by scottyb

And what were your expectations?

Not knowing what the cart is and what is installed, I don't know what to expect.

[scottyb]

Originally Posted by mrphilf

Thanks for all the help Johnnie! Hopefully after battery break in is done I can finally be done tinkering with this thing and move onto a new project that I know more about lol. Although unless the batteries get a whole hell of a lot stronger it seems like this build is just not going to live up to expectations :(

My question was to this man.

In addition to the information you requested we need to know what he was expecting that isn't happening

[JohnnieB]

Now I understand.

[mrphilf]

Originally Posted by JohnnieB

Maybe something is holding it back.

What D&D motor?
What Cart body type?
What Controller?
What Cables?
What Solenoid?
What F/R switch?

D&D 4:1 motor. According to Vic, highest torque available
1991 Marathon
GE 500 Amp controller - was recommended by East Coast Carts
2ga
Solenoid is "HD" box said rated 200amp. I didn't even realize there were larger ones til I read this.
"HD" FNR switch - unknown of any rating
22" tires

My expectations - put 2 adults and 3 small kids on the cart and drive through logging trails in the mountains and be able to climb the hills. I don't need to climb them fast just climb them period. As I stated before, according to Vic at D&D, I should be able to climb a hill steep enough to flip the cart...

I would LOVE to need to be forced to go into my Garage and fab a set of off road wheelie bars...but I don't expect that much. Pulling a hill steep enough to make me nervous that I have small kids on board is my realistic expectation

[JohnnieB]

Marathon has a Pot-Box throttle. Pull the Black and white wires off the controller and measure between the two wires with an Ohmmeter.

Should be about zero Ohms with pedal up and about 5,000 Ohms with pedal down.
What do you have?

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Are all 13 high current cables 2Ga?

Are any cables or components (other than the motor) getting more than 10°F above ambient air temperature?

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The 22" are costing you about 20% in torque, but the motor ought to have upped the torque by about 40%, so there is a net gain of about 20% over stock.

Upping the pack voltage from 3V to 48V should have generated an additional 33% gain in torque. So you ought to have about 50% more torque than a stock Marathon on 18" tires.

What is the max air pressure printed on the tire's sidewall?
Low pressure tires take more torque to turn.

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I agree with Vic, that cart ought to climb anything that doesn't flip the cart, if the tires don't loose traction.

[mrphilf]

Yes all 13 cables are 2 ga. Charger cables are still stock 8ga but I can't see that mattering.

I had tested the potentiometer before but I did it again to be sure. 0 and 5000 ohms. I used an analog meter...I can do it again digital if it's that critical to be that accurate.

Yes I am using low pressure quad style tires. I know they take extra power to turn, as does driving off-road on dirt and gravel.

I never checked for any components heating up. I will do that on my next run.

Battery charger ran at least 14 hours, not sure exactly how long but I checked at 14 and it was still on. I just got home and the green light was on for charged. I unplugged it from the cart and the wall waited a minute and plugged both back in, it detected and then charged with both the yellow and green on for maybe 20 seconds then went to green only. So I assume now they are fully charged?



On a side note, I do have a winch installed. Double switched and tested not to be drawing any power unless activated. I had it running off 3 batteries on my old 36v setup. I have NOT hooked up the wiring since putting the new batteries in. After reading the DPI book it warns about having even a slight imbalance in battery power. How much imbalance is really bad? I only used the winch once each of the past 2 years and theoretically should need it much less with my new 48 v power. Is it that big a deal? I don't want to add the weight of a 12v battery to run the winch...if needed I would hook the winch up to the full 48v and risk the winch...do I need to do that?