48V Conversion - No Speed Gain

[Lee0smond]

Hey y'all,

Recently made the transition to a 48V system, but was surprised to not pick up any speed at all (series style motor)

I had upgraded to the SR4500 full package and a new-to-me D&D motor and was getting about 18MPH on flat ground (stock 18" tires) (on 36V)

Swapped out the batteries to 6 x 8V batteries (and resistor) but did not get any speed gain at all. Is that normal? I thought with a series motor bumping up the V meant almost a linear increase for speed.


Anything thoughts or ides? Does the top speed of 18MPH sound right on 18" tires - flat ground?

[Lee0smond]

The D&D Motor is:

Model: 170-013-0001
HP: 8.5
Speed: 16-19

With the disclaimer:
• Performance based on Stock Controller comparison.
• Based on 36 V volt vehicle application specs.
• All motors can be used at 36 / 48 volts.

So I'm right in the specified speed range. But I was hitting it with 36V so just surprised no impact with 48v whatsoever.

[Volt_Ampere]

Increased voltage with a series motor should give you a speed gain but more noticeable would be a huge torque gain at low speed.

[JohnnieB]

If you got 18MPH with a 36V battery pack, you ought to have gotten roughly 33% more speed (and torque) with a 48V battery pack.

1. What is your 48V battery pack voltage 12 hours after charger shuts off?
(Should be at least 50.93V if they are Trojan brand or clones, higher for other brands.)

2. What does the pack voltage drop to when at top speed on level pavement?

3. What is the voltage between the controller's M- and B+ terminals when at top speed on level pavement.

[Lee0smond]

Originally Posted by JohnnieB

If you got 18MPH with a 36V battery pack, you ought to have gotten roughly 33% more speed (and torque) with a 48V battery pack.

1. What is your 48V battery pack voltage 12 hours after charger shuts off?
(Should be at least 50.93V if they are Trojan brand or clones, higher for other brands.)

2. What does the pack voltage drop to when at top speed on level pavement?

3. What is the voltage between the controller's M- and B+ terminals when at top speed on level pavement.

Agreed on the 33%. I was expecting to see somewhere near 22-23ish, especially since the batteries I was replacing were on their last leg.

1) These are brand new Interstate GC8 batteries (6 x 8v). Just ran up and checked, showing 50.7 now to the gauge I installed. I was messing around testing lights so I will have to charge again and re-check tomorrow for true topped up, but either way 50.7 is WAY higher than the crap batteries I replaced. Big thing is the last set of batteries would barely hold 36V and would drop substantially to like 33 even on flat ground and I still got about 18ish on flat ground - would lose lots of speed uphill (phone speedometer gps app).

2) Think it dropped to around 48V lowest. I'll re-run it tonight once I get the lights buttoned up.

3) Haven't measure that. I'll have to go buy some clips for my voltmeter. I've just been using the guage I installed for total pack voltage monitoring.


But even still, old crap batteries that would drop 6v in a 36v system are giving me dang near the same top speed flat. Something seems off.

[Volt_Ampere]

I agree that something seems off. Make the voltage measurements while driving and you should find out what is limiting your speed. Sounds like maybe your controller isn't giving your motor full battery voltage under full throttle at speed.

[Lee0smond]

Fairly new to this forum, is there any way to tag a user in a post?

@ScottyB, are there any settings in the controller you sent I need to check?

All wire connections are tight. Nothing else changed other than swapping batteries and resistor.

[Lee0smond]

Just took it for a spin, drops down to 46.4V when driving on the gauge.

[Lee0smond]

I also drop down to 12MPH going up hills which is only slightly better than with the 36V batteries.

Definitely not what I had expected going to 48V, that's for sure.

[scottyb]

D&D is pretty adamant that many of their motors will gain 1-2 mph when going from 36 to 48 volts. They should know they built it? Call them and ask. Let us know what they say