Magic Magnet on a stock '02

GEM Forum
1

A bit over a week ago I got in touch with Dave @Inwo about upping performance on my GEM and after me initially trying to order the wrong part or too many parts because people write their posts differently and some are easier than others to decipher, Dave was like, “just try this and let’s see from there”.

Very pragmatic. I really appreciate that Dave. Could have easily sold me crap I didn’t need, because I haven’t yet decided how I want to boost the voltage.

Between that point and when I received it, besides a few conversations where Dave was super helpful in going over some battery and equipment options, I pulled the front batteries and tray out to see the part number on the transaxle / gearbox because I wasn’t really 100% sure if I had 10.35 gears.

Yup. Last part of the number on the top row “0613-00249” = 10.35:1

Not surprising, it’s the 2002 long back truck version.

Ran the tire size through a calculator, took that diameter and went to spicer’s transmission calculator.
Ring/pinion =1 , tires=21.8 (stock), engine rpm:4100 (stock 5hp GE), transmission ratio: 10.35…
…
= 25.7 mph :frowning:

Now, if I had the 8.9:1 trans, then = 29.89 mph.

On paper.

When the MM came in, hooked it up, took the doom buggy out and floored it. GPS said 27, just shy of 28. Not bad, especially for short gears. I’m going to have to do more, but nice to see where just a single mod fits in.

Unsurprisingly, if you have an 8.9 transmission or larger tires, I suppose you could be looking at 30+ mph for a single modification.

Pretty damn impressive Dave. Thank you. A $125 mod, that takes under a minute to install that could add a solid 30% or more to the top end. Batteries drain a bit faster at top end as to be expected, but might be worth it depending on your transmission and tires.

As for my heavy azz gem and it’s short gears, it’s gonna need more voltage, the MM and maybe a shunt. Plus some more speed parts stickers, and maybe a chrome differential cover. Those never hurt.

2

Sounds good. If your looking for just a few more Mph, perhaps try Rodney’s 7th battery Trick. Where he Upps the voltage of a Stock gem by adding a 7th 12v battery along with Dave’s voltage spoof. Seems like a in cost friendly way of getting a few more MPH.

3

I can make a lithium boost kit.
12v green battery with shunt balance and a 20a charger for about $300.
Need the usual guinea pig to test it. :slight_smile:

Also worth testing is putting the 12v boost between contactor and controller.
As of yet no one has taken me up on testing it. As normal I’m too lazy to do my own testing! :slight_smile:

That method needs no spoof, and all acc. are still on 72v. Only motor gets the HV.

I may not always push my ideas, as I sell things on here, and let results do the talking.

image

4

Thanks Grant,

That’s certainly one option I am considering.

My other is getting rid of the FLAs and getting lithium cells, I love the idea of them and what they can do, but there are some complications for me there. Dave has come up with some options for me to mitigate the reduced range of the 60Ah cells, but I do still sometimes load the bed down and because I have a tool box that takes up the first 2’ of the bed (leaving me just enough room to forklift a pallet on) unless I cram everything to the front, I’m going to end up with possibly a significant portion of that weight behind the rear axle, at which point I worry about losing traction without the 200 lbs of lead in the nose.

That and the FLAs are new, so I’m kind of stuck with them for a few years.

5

I’ll be your huckleberry…

6

Here ya go!

MVC-015F

This is a one-off using parts on hand. Losing money on the 20a charger.
Also completely assembled and tested to drop in.
I’m doing a charge cycle now to test the shunt balancers.
Then I need to build a 12v spoof and it will be ready to ship.

7

Top it off with a low voltage alarm.

MVC-016F

8

Fine tuning the charger.
Turned voltage down until current dropped to 2.5a.
Notice how all the “full” lights are on?
One is slightly behind “dim” after first charge.
Fine as it is, but will see if the trickle will finish the last cell.
Cell levels may very well be closer than the shunt voltage error.

image

I love these shunts. Hope I don’t run out!

9

You dont need a magic magnet with a T1 or T2 controller.

10

True, but less money than a programmer.:crazy_face:

11

Java ,

tell us more about your gem and how you use it . also what terrain is it used in ?

fyi a 10:35 diff can get you over 40mph with the right setup , you dont need the 8.9 diff

12

Thanks.

late 2002 e825 “Long Back” (late '02, as in December 27th manufacture date, lol)
5hp GE motor (5BC59JBS6368)
10.35 gears
155/80 R12 tires
Zivan NG1 charger w/ updates
DC-DC board update
T2 controller (i think - I’ll have to pull the dash and look again)
NAPA 8231 FLA deep cycle 105Ah (Deka # DC31DT)

Pretty much stock (i think), other than front suspension was monkeyed with:

Picked it up a few months ago from the local UC’s bus line department. They used it as a maintenance vehicle and hauled tools and parts around the campus. Don’t know any more details than that, but the bed has definitely seen some weight and use. Then it sat abandoned for a year or so, which, unsurprisingly, turned the old batteries into boat anchors.

Intend to, and have been using it as my daily driver. It still sees some use as a “work truck” hauling crap and kegs around occasionally. When it does it’s typically only a few hundred lbs, but the potential for a 600-ish load is there.

Most drives are only a few miles at a time. But sometimes I’ll make multiple trips in one day with pauses in between.

Terrain is mostly flat ish , slight grades. A few brutal overpasses though. City takes up 9 square miles, most streets are 25 mph, a few 35 and one 40 and one 45.

Don’t really want to change the gears because of the occasional hauling, would be happy with 30-32 sustained, 33-35 sprints with just me and some light cargo (2 person weight equivalent) . Would be tickled if I could someday get this thing to run 40+ with an empty bed, but don’t think that’s going to be possible until the FLAs are out of the picture, but then I’m potentially into traction problems if the bed has any weight in it behind the rear axle.

I have an idea for that, but not sure if it will work. Have to talk to Dave a bit about it.

13

If it works out, I just found a 12v battery that’s in an ammo box. Also have 5amp chargers.
Maybe someone else will copy it.
In any case, yours went out yesterday.

14

Thanks Dave,

I was actually looking at the photos earlier and wondering if it would fit in an ammo can…

15

Perfectly, 50cal tall if you want the lid to close.
image

16

Gawd dammit UPS!!!

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17

No worry, the hot glue plugs are not needed. The oil is from the way batteries were submerged in mineral oil.
Oil is harmless insulating oil. Messy, but will not damage anything.
The batteries are cleaned before shipping, but changes in temperature pushes oil out the plugs.
If you find any that do not perform or one that was cracked I’ll send a replacement.

18

@LithiumGods will explain. His were shipped with “floor dry” , and he said it was worse than the oil.

Oil tank picture.
2000lb%20on%20pallet 2000lb%20basket%20full 2000lb%20basket

19

Got it. Thanks Dave.

20

Installing after the contractor worked exactly as advertised.

Started plugging at 28, then I remembered I took the MM off. Went back and installed it, hit 30mph. Can pull 25 mph up a overpass that I previously could only manage at 18-19 mph. Had a fluke 325 around one of the armature leads, but could only glance at it occasionally. 66 amps at 30 mph on straights, 85-105 amps pulling up hills. Min-Max recording logged a 313 amp max, not sure what I was doing at that time though.

Only ran it around for 4-5 miles. Disconnected the pack, going to put the dash back together, maybe another run tomorrow.