Hey GEM friends, i’m curious. Have any of you calculated your miles per kWh? What are you getting? I have an eLXD with a 10kWh gel battery pack but i’m only getting 10-15 miles of range. In efficiency terms, that’s worse than a Tesla model X. Doesn’t seem right.
For starters, those 14:1 gears aren’t helping, but also check for a dragging brake. Typically one of the rear drums.
My 2010 eL (with a 120Ah (about 10kWh @ 90 volts) Chevy VOLT li-ion battery, IIRC I get 275 watts/mile, but I’m running wide turf tires that aren’t doing me any favors on resistance plus I tend to have my foot in it and I have an MM so I run around 33mph.
It sounds like you’re getting 3 to 4 times better milage than me with almost the same vehicle and nominally the same size battery pack. Something must be very wrong. Certainly doesn’t feel like a brake is dragging but i’ll check. Do you not have 14:1 gears on yours?
I guess it is important to note that the dealer i bought this truck from installed the batteries–supposedly new ones-- only about 8 months ago. Could they have installed them incorrectly? Jrjava, i just noted that you advised me (on a different thread) to check the battery settings months ago. I still need to do that. Could the wrong battery setting cause such pathetic range? It does seem to me that the thing charges to full much faster than i expected. Today it went from 33% to 85% in less than two hours with the regular onboard charger. GEM literature says it takes 8 or more hours for a full charge.
It sounds like you need to do a complete pack checkup.
Is there any dates on those batteries?
Look for a round sticker with a Letter and a number. (E9 would be May '19).
I’m guessing it is currently charged?
Write down the voltages of all your batteries.
Do a brake stand test and write down how low the V drops.
Do this test on all of your batteries.
Check what profile your charger is set to.
Report back with what you find.
I agree that the problem may be in your battery. It only takes a few full discharge events to radically and permanently decrease the capacity of the bank. It is also possible for a single defective battery to dramatically decrease your performance. The output of the pack can never be better than the weakest battery in the pack.
It is not difficult to measure the capacity of your pack. Using an inverter, a space heater and a Kill-A-Watt device ($40 on Amazon) you can determine the exact capacity in a few hours. If the total pack capacity is abnormal, you can recharge and test each battery individually to determine which one or ones are defective.
Pete,
I tend to drive around empty. I never did any calculations for the vehicle when it was weighted down
Similar vehicles, but different setups.
eLXD specs from memory here,but:
eL - 12.44:1 eLXD - 14.76:1
eL - 5hp long GE. eLXD - 7hp hd motor, various manufacturers
Obviously, eLXD efficiency will be worse with those parts installed.
I’m running 23" tires and I’ve done some tuning on my controller, but nothing extreme.
I once measured, quite by accident, with one side rear parking brake dragging only slightly. This added an easy 100 Wh/mile load to the vehicle.
Bad wheel bearings will also add up on your load.
And do all the checks my twin brother from different parents suggested ( @AssyRequired )
Are you running pack dead?
Are you exceeding the ah rated C current? I’m quite sure that you are.
Rule of thumb, lead will only supply 1/2 capacity in normal ev service. IMHO
Waiting for a county inspector… lots of time to reply…
The batteries are labeled 3/21, so they really were new when the dealer installed them.
I run the pack pretty hard, often getting into the 30% remaining range, occasionally into the 20% range and once or twice below 10%. I know that’s supposed to be bad for the battery, but when my range is so crappy it’s hard not to. This is my work truck, not a toy. And this may be bad for the battery in the long run, but part of me wants to kill them so I can get lithium. So far it has had no effect on range though. I think I got 16 miles on a charge the first week I had the thing and that’s what I got yesterday.
Sometimes I run the truck empty, sometimes packed with tools, and once I ran it a mile with 1,400 lbs of concrete in the back. It doesn’t seem to change my range much either way. I’ve been amazed at how little weight seems to affect performance. The thing is slow and inefficient, but damn is it strong. What I don’t get is why, if it is so unaffected by weight, it is so slow going up hills. How does it know the difference between resistance from weight and resistance from climbing?
I don’t know what the ah rated C current is. Please educate me.
Lead batteries only have half the listed energy?!?!?! How do they get away with that? Do lithium batteries have the whole thing.
The truck had two bad wheel bearings when I first got it. It took me a whole month to order the parts and change them out. When I finally got around to it, I expected a big boost in range. Nothing. Not a single mile of improvement.
I just jacked up the back to find (Jrjava, you’re a genius) both rear brakes are dragging a little bit. Damn, I wish I had tools with me to work on that while I wait. I wish I had a voltmeter with me too.
I actually have a Kill-a-Watt meter somewhere. If I find it, I could start by just measuring how much energy goes into the pack during a charge. I suppose I might find that the GEM is plenty efficient, but it just doesn’t have as much battery capacity as claims to.
More to follow!
They can supply listed energy when used slowly. (low C)
Also it uses full to empty, which as you know is bad for them.
Lithium can supply all the energy without damage and take very little extra to charge.
While lead is inefficient wasting energy as heat, equalizing, and gassing.
Rule of thumb is 2:1 advantage with litium. IMO
Pete,
Sometimes it’s the parking brake arms that hang. You can literally just tug backwards on one with a pair of pliers and it should release. They bind where they go over the hub mount into the drum. White lithium grease works well here. No genius here, rear brakes binding one way or the other is a very common problem on classic GEMs going back to at least '00.
The brake stand test that @AssyRequired will tell you if you have a bad battery.
The killawatt meter, inverter and heater sounds great if you have time and methamphetamines to kill.
5 Likes
If you have changed out your stock tires with larger tires, the diameter changes and you will be traveling farther per revolution. It seems small and insignificant but it really adds up and you will actually be traveling a lot farther. Unless of course you are using gps then disregard
1 Like
Pete,
I drove out to the outskirts of the city yesterday, so I was able to get enough travel distance to take some new power consumption measurements at two different speeds.
At 33mph with my foot in it I came up with roughly 221 Wh/mile
At 25mph, trying to be more “factory stock” in speed and acceleration that dropped to 166 Wh/mile
A mix of city streets w/ stoplights and a long uninterrupted straightaway. Not much in the way of hills here, just one freeway overpass to get to NAPA auto and a train underpass after I left there. Return trip was all flat. I run fairly aggressive regen on pedal lift, but I have no way of recording what goes back to the pack. Also, the GE controllers only regen when you are above a certain speed (I forget what it is - 15mph maybe?)
Watts were computed manually, as my BMS does not report them, so there is some small deviation from actual as the pack voltage is constantly changing. I used simple averages for voltage when computing numbers below
Obviously, your 14.x:1 gears and being loaded with tools and 500lbs of lead batteries is going to drive those consumption numbers up.
1 Like
Jrjava, I jacked up the back again only to find my brake setup looks nothing like yours, so I need to get a bit deeper in the weeds to figure out how to get the brakes to stop rubbing. I’ve never worked on drum brakes before.
I put a kill-a-watt meter on my charge cord last night. I plugged in at 20% and the pack took in 5kWh. So i guess its actual capacity is around 6.25kWh. I’m averaging around 15 miles per charge, so that’s 417 Wh per mile. I haven’t done any of the battery tests yet (I have a small business and a four year old daughter, so I don’t have a lot of time to do this stuff).
But it sounds like I have both problems: my battery doesn’t really have 10kWh like it’s supposed to AND my vehicle is using the 6kWh I do have very inefficiently.
Nomo, that is an interesting theory I had not thought of. I think my wheels are larger than stock. I bought it used so I’m not sure What size is stock on a 2011 eLXD? I guess I need to get a GPS odometer to check if my odometer is correct. I have noticed that when I fly by a radar speed trap at what I think is 25mph, it always says I am actually going 22mph. But if my wheels were larger than stock, wouldn’t I be going faster than my speedometer says, not slower?
Pete, I feel you may be inadvertently going on a snipe hunt with all the things you are trying to chase at once. Short of a giant meteorite, I have found that most things can be eradicated by running them down one at a time.
Did you happen to take any pictures? They would help greatly in sorting this out.
The eLXD has more in common with the e6 than it does with the eL.
Maybe, maybe not. The eLXD does have a much bigger motor and shorter gears, but I’m not sure that accounts for double the power consumption of other non-HD GEMS. But maybe it does.
Putting a watt-hour meter such as the Kill-A-Watt, to monitor the input power to the battery charger is not going to tell us a lot about the battery pack. Actually, that’s kind of an understatement, it’s actually a lot closer to zip and zilch, once w[e get past it confirming that the charger is turning on, but we knew that already.
There is no such thing as a 100% efficient charger or charge cycle. It is simply impossible under our current understanding of the laws of physics and electricity. Even more so with lead and acid, which are at the lower end of the efficiency scale, All the heat that the pack, cables, heat sinks on the charger, etc give off… that’s all lost power.
Your charger, if it’s the original or identical replacement, is rated at 15A input on 120V / 60Hz and 12A out at 72-100V DC.
If you’re not seeing anything close to that, your KAWm might be fvcked. or it might be trying to telling us could be any, all or none of the following:
- That it’s not set to the right profile and instead of charging your batteries, it’s slowly murdering them.
- That an external sensor that the QuickQ needs input from to properly charge the batteries is missing, damaged, out of position, etc. Some profile #'s need the temperature sensor, some don’t. So instead of charging your batteries, it’s slowly murdering them.
- That the KAWm is somehow only partially functional and not ̶p̶u̶t̶t̶i̶n̶g̶ ̶o̶u̶t̶, err, delivering the rated output and therefore rather than charging your batteries, it’s slowly murdering them.
We need to know what profile it’s running from the boot up blink codes and also, we need some battery testing done in the manner which @AssyRequired laid out and not some perverse cacamamie bs involving a KAWm, a space heater, and running each battery down to zero SOC, which will quickly murder it BTW. Lead batteries that hit 0% will suffer damage from that, and the longer they sit that way, the more damage they will take.
And, it’s not like you can use the DQ onboard to charge them at the end of that fiasco, because, you can’t. It won’t start because the voltage is too low, so, you’ll need a small armada of little chargers that are the most basic dumb as box of rocks units, or patience that lasts for days as one external charger makes all the rounds.
P185/70R13 which is a 23.9" inflated with no loading, Probably around 23.5" give or take (probably take) on the vehicle. Sounds like you might have bigger rims but shorter tires.
A great GPS dash spedo w/ distance recording that GrantWest found and posted about:
https://www.amazon.com/gp/product/B07FNHGRZ9
The 2011 manuals:
POLARIS 2011 GEM OWNER'S MANUAL Pdf Download | ManualsLib
Tire size calculator:
Tire Size Calculator
Well KAWm me to tears, I just wrote an assyrequired length post.
Oh, and just to make it even longer, here are the specs from the manual:
The elXD and e6 have completely different rear brakes than the rest of the gems. The are a modern automobile style drum brake and I’d put money down saying the entire assembly is off of a Chrysler PT Cruiser, the wheel cylinders are anyway.
That makes s lot of sense, Derrick. Thanks.
Pete. Drum brakes aren’t that hard. Main thing is equal spacing and maybe a $25 brake spring tool. That one tool is worth it’s weight in gold when it comes to ease and speed.
Ok, finally made some progress here and learned some things…
GPS
I put a GPS speedometer/odometer app on my phone and confirmed that when my speedometer says i’m going 25, i’m really going 22 and my milage is actually around 10% WORSE than what i thought it was when i started this thread!
Tires
My tires measure about 22-1/2" across. They say 185/60R14 on them. So bigger rims and shorter tires indeed, jrjava Using the handy tire calculator Nomo posted and the original specs jrjava posted, i see that my tires are 2.2% smaller than what the controller thinks they are and my wheels have to turn an extra 17 times to travel a mile. There we go. That explains that. My treads are a little bare, so maybe i should invest in some new 185/70R14 ones… i think they will fit? I would certainly appreciate pissing off fewer people from driving 22 in a 25 zone (Or maybe not. They want to be going 45).
Brakes
Seems like it was the parking brake rubbing. I adjusted that today. We’ll see how it goes.
Voltages
Lowest is 8.84, Highest is 8.89. With the brake stand test, voltage dropped to 8.39. Pretty healthy, no? I only did the brake stand test for one battery. I’d need a helper to test any others like that and my 4-year old daughter is not yet up for the task.
Delta Q charge profile
It is set to 24. WTF is 24? It isn’t on any of Delta Q’s algorithm lists as far i can find! So… should i change it? To 6? 26? I’ve got nine Deka Dominator gel batteries. 8V 140Ah 8G8VGC.
I found algorithm 24!
Looks like the dealer set me on the right profile after all.