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Old 07-20-2021, 12:16 PM   #11
Volt_Ampere
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Default Re: Starting my EZGO Marathon Lithium build.

Looking good. Do you know if there are any other sources for these BMW batteries? They look like they should work well for a build. I did not see any listed at Battery Hookup.com.
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Old 07-21-2021, 07:29 PM   #12
jhornbr225
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Default Re: Starting my EZGO Marathon Lithium build.

bronsonj - Thanks! I actually feel like I've been pretty lazy. We all know how long these things take. Everything is custom, things need fitted, which usually means putting things half together, taking measurements, then taking it apart, making some holes, then repeating.

Volt_Ampere - I have not seen these batteries anywhere else. Not that I actually do any hunting for batteries. I don't actually recommend them, especially if you want to parallel them up. It took a lot of time (and careful drilling), to tie into each cell's busbar. I suppose if you were not going to parallel them, you could use them as they are. Battery Hookup sent the plugs to hook up the balance leads. My problem exists because I bought two sets to parallel them up. I suppose once I get them all wired, top balanced, and then paralleled, and then some range testing, I'll find out if it was worth all the effort.

Today I got the throttle pot mounted to the side of the main bracket. I've decided to put some studs up through the battery tray so that I don't have to fight so hard with the bolts and nuts being on the top and bottom at the same time. Once I get some 1-3/4" x 1/4-20 all-thread bolts, I'll mount those into the battery tray and then all I'll have to do is place the bracket with all the stuff down on it, then thread on the nuts on to hold it down.

I'm also going to do the same stud thing with the brackets for the fuseholder. I got two pieces of aluminium cut to hold the fuseholder, but by the time I decided I needed all-thread bolts, the hardware store around the corner was closed.

I did order some more transistors today. I didn't want to chance ordering the MJE3005T from the same vendor, I'm sure I'd get the same incorrect parts. I ordered some MJE13009-2. They are rated for higher voltage, will handle 12A, and are 130W capable. I don't think the wattage is all that critical. Since the output voltage will be 50.3V, and the max input is 56.7V, even at 12A, the wattage will be 76.8W. I won't be drawing anywhere near that much current. I'll only be powering the main contactor coil, one side of the reversing contactor coil, and the relay for the Cell undervoltage at any one time.
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Old 07-24-2021, 10:59 PM   #13
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Default Re: Starting my EZGO Marathon Lithium build.

Spent the day looking at the reversing switch. It was my plan to use the microswitches in the OEM switch to power my reversing contactors. The problem is that there is an extra divot in the plastic circle that makes it so that if I'm turning the switch to one side, it works fine, but turning it to the other side actives both switches. That's not good.

I emailed Scotty B about what reversing switch is recommended for the EZ-GO. On the website I see one for the Club Car, but I'm not sure if that's the right one for me.

I looked into starting to make cables, and found that the studs I had installed on the batteries for me to bolt my ring connectors to are too short. I had used 3/4" long 1/4-20 bolts through my aluminum plates. So I went through all plates on all the batteries, and replaced the 3/4" long bolts with 1" long bolts.

I actually installed my Alltrax, reversing contactor, and main contactor on my bracket. It's still not mounted in the cart yet though.

My Bluetooth modules showed up yesterday, so that's a relief.

Darn Amazon. I ordered transistors for next day delivery, but they sent me an email saying that they were running late. So I cancelled that order, and ordered them again, for next day delivery. I got another message today that these are running late again. I'm thinking they are trying to send them through USPS, which in my area, does not work well on the weekends.

So I guess tomorrow I'll start making cables.
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Old 07-25-2021, 08:10 PM   #14
jhornbr225
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Default Re: Starting my EZGO Marathon Lithium build.

Transistors showed up today. I'll have to give them a test and see how this voltage regulation works.

I made all the cables between the fuse, the controller, the main contactor, and the reversing contactors. I'll work on the batteries last. Best to hook up all the other cables, test to make sure everything is correct, then work on the actual power cables. After that is all the control wiring.

I wired it up according to the drawing in the Alltrax manual, but then there is a thread here on BGW where Scotty B installs an SW202. Reading through the thread, I found a diagram that contradicted the way I had wired it up. A little further reading in that thread showed that a few years ago, they added magnetic blowouts to the SW202, necessitating the proper polarity of current going through the contactor. The old drawing didn't have magnetic blowouts, so following the current drawing is needed, instead of the old drawing in the thread. Crisis averted.
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Old 07-26-2021, 08:20 PM   #15
jhornbr225
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Default Re: Starting my EZGO Marathon Lithium build.

I experimented with voltage regulation today.

I've found that each of the coils in either the main contactor, and the reversing contactor, draw between 350-400mA. Their coil resistance according to the datasheet is 141Ω, I actually measured 120Ω. So with the main, and one of the directional contactors on, I can expect a max of 700-800mA. The relay for the protection circuit's coil resistance measures 2300Ω, so it's current draw will be minimal, like 20mA or so.

I did put my Ammeter in series with the two coils, and I read 0.70A

I first put a 1KΩ resistor as the series resistor to my 51V Zener diode. It didn't seem to regulate voltage at all. After doing some experimenting, I calculate that I'll need 100Ω. The gain of the MJE13009 per the datasheet is anywhere between 8 and 40. I calculate the gain of mine, in the region that I am using it, is about 18.5. So if the total load is, say 850mA, then the current flowing through my series resistor is about 46mA. At my max battery voltage of 56.7V, and a Zener voltage of 51V, the max voltage drop across that resistor is 5.7V. If the max current is 46mA, at the max voltage of 5.7V, then that resistance needs to be a maximum of 124Ω. I'm going to put two 220Ω's in parallel. That will appear to be 110Ω, so 46mA flowing though 110Ω will give me a power dissipation of 232mW, divided across two equal resistances, so about 116mW per resistor, worst case. So 1/4W resistors will be no problem. There's also the Zener Diode current to add into there, but it's like 5mA, so I'm not really worried about it. With my selected components, and even worse case scenario, there is enough of a safety factor.
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Old 07-29-2021, 07:32 PM   #16
jhornbr225
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Default Re: Starting my EZGO Marathon Lithium build.

I started putting together the box with the BMS, relay, and voltage regulator. I immediately ran into problems. Although I ordered that same size enclosure as Sergio, the 100A BMS I bought from Battery Hookup, is larger that the 20A unit Sergio has. My BMS is exactly as wide as the box. Since there are 6 screws, one in each corner, and one along the middle of each long side, my BMS won't fit. Options, either get a bigger box, but the series this box is in, this is the largest. Second, order a smaller BMS. I don't really want to do that either. Who knows how long it would take to get here. Third, Dremel out the inside of the box. The middle screws have a stand of plastic that goes all the way to the floor of the enclosure. I Dremeled out the bottom part, so that I can still install the screws. I just have to slide the BMS in under the nubs of plastic. Next, the temperature sensors some out the side of the BMS. With these plastic dividers used to hold circuit board in the box, I could not slide the BMS to the floor without damaging the temp sensor wires. So more time with the Dremel.

I built the little circuit board for the regulator. I realized as I was building it that I had the strip-board, where you have to notch out parts of the stips of circuit traces that you don't want connected. I drilled the holes in the enclosure to hold the relay and the circuit board to the side. I also drilled the big hole for the waterproof cord grip for the wires to all the individual cells. I still need to drill more holes for the C-, B-, key in, and key out.

I decided to hook up and test the Voltage converter for 12V for the radio and headlights. It works fine. Things will be a little tight if I try to put both my enclosure for the BMS and the voltage converter on the same wheel well. I've decided to put the BMS on the driver's side, and the Voltage Converter on the passenger side. That Voltage converter has quite a bit of input capacitance. There was a spark when I first connected it. I suppose when I go to install it for real, I'll use a resistor to charge it slowly, just for the heck of it.

I'll keep working on the BMS enclosure. I also need to remove all the big wires from the contactors and controller and hook up all the little wires. After that I'll tighten down the large wires.

I picked up an on-off-on switch from Home Depot today. ScottyB replied to my inquiry, and said the reversing switches are 6-8 weeks out. So the Home Depot switch and a couple fender washers will have to do for now. Otherwise it's hook it up for Forward only, and push it by hand for reverse.
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Old 09-20-2021, 07:32 PM   #17
jhornbr225
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Default Re: Starting my EZGO Marathon Lithium build.

It's been a while since I've posted. I have been working on things, just have not gone through the effort to post.

I decided that I didn't like the three batteries that are side by side, with the long sides of the batteries facing the front and back of the cart. I got some angle iron, threaded rod, and a 12" long drill bit. I bolted the angle iron to the battery tray, then bolted the batteries to the angle iron. They are not going anywhere now. The battery that was in front of the controller bracket, I had originally ran some threaded rod down to the battery tray for that battery to sit on, but it was not actually bolted down. I installed longer threaded rod and bolted that one down as well. Currently the only batteries that are not bolted down are the two smaller batteries towards the outside walls. They fit pretty snug in there, but I'm thinking I'll get some more threaded rod, and bolt those down as well, just to be sure.

I extended the wires for the BMS balance leads, and put ring terminals on them. I installed the BMS app, but it was not one that I could change parameters with. After some reasearch, I found that version 3.1.1026 allowed me to change parameters. I took some screenshots of Sergio's settings and changed the defaults.

I installed Alltrax toolkit on my laptop, and plugged into the controller. It woke up, and I was able to see and change settings. It's a little tight plugging in the USB cable because the battery is pretty close, but it's possible.

I again had to mess with the 1/4" studs on my batteries. The terminals at the extreme end of each battery will have numerous ring terminals on them. Especially the B+ and B- terminals will have extra ring terminals for the voltage converter and the charging connections. The terminals in the middle will only have one large ring terminal on each, and one terminal of the pair will have the balance lead. With using a couple flat washers, and a lock washer, I needed to get 1-1/4" long, 1/4-20 bolts that were all thread. I used 12 of those, two for each battery.

I labelled all my balance leads, and labelled each cell on the first string of batteries. I measured the voltage at the multi-conductor plug for the BMS, and the voltages were correct. I plugged in the connector and fired up the app. The first two cells showed no voltage. I tried the other BMS that I have, and it showed the same two dead cells. I measured the voltage again, and the voltages are fine. On a hunch, I thought that since I did not have the B- and C- leads connected, that it might be causing the problem. I attached the B- and then all the cells showed the proper voltages. It's weird that only the first two cells showed zero without that main B- lead.

I verified all my control wiring, and installed the control fuse. I did not have the main B+ connected. I turned the key, measured a few voltages, and heard contactors turning on and off. So far so good. I did some ohm checks on the high power side, and all appeared good. I used a 10K resistor and used that to pre-charge the bus caps in the controller. Even though there is already a resistor in line, I wanted to be extra sure that I charged it up slowly. Everything looked good. I plugged in the laptop and saw rising voltage on the B+ monitor. I then removed the 10K and tied the B+ terminal right to the battery. I had set the amps and speeds and accel rates way down in the controller. I put the rear end on jackstands. I turned everything on, put it in forward, and pressed the throttle. Nothing happened. I did have the amps pretty low, so I turned them up slightly, and the wheels started to turn, although the wrong direction. I flipped the switch to reverse, and the wheels turned forward. I disconnected the main battery lead, and swapped S1 and S2 at the motor, I guess I'll have to re-label some wires. I set the rear end down, cleaned off the cart, and went for a spin. I currently only have the amps set to 150A max, and the speed set to 50% max. After letting it get to speed, it feels almost as fast as it used to be, even though the max is currently 50%. I'm sure I can turn up the amps, as soon as I get the batteries all balanced and the two sets connected in parallel. Currently I'm only running on one set of three batteries.

But, Hooray! Marty finally moves under it's own power. There is still a lot of cleanup to do. Wire ties, split-loom tubing to protect the wires, etc. I need to label the cells on the other batteries, and get those ready to parallel up. I've got some 2AWG jumper cables to make to parallel up the cells. I've got a radio to install, and some speakers. I need to take a closer look at my regulator circuit, I think my output voltage is a little high, higher than what I tested it at before.

I also need to order and install a voltmeter on the dash. Gotta be sure not to run the batteries too low.
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Old 09-21-2021, 05:59 AM   #18
bronsonj
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Default Re: Starting my EZGO Marathon Lithium build.

Wow, you've certainly made a lot of progress!
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Old 09-21-2021, 03:55 PM   #19
jhornbr225
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Default Re: Starting my EZGO Marathon Lithium build.

Well, it has been almost two months. Again, my fault for not working on it more.

I ordered the Renogy battery meter suggested in Sergio's thread. The Amazon reviews for it are all over the place. Some hate it, some love it. I guess we'll give it a try. And according to camelcamelcamel.com, at $79.99, it's almost at the lowest price that it gets to. The lowest it ever went was $75, but that was short lived. It's supposed to be here in two days. There were some reviews that complained about no mounting for the shunt, but the description showed a shunt holder. maybe Renogy added it after all the complaints. Some also complained about the length of the shielded wire between the shunt and the display, but it looks to be 20ft. now. Should be plenty long. There is a small place next to the radio hole that it will hopefully fit in.

Looks like rain today and tomorrow. And although I do work in a garage, I have to work right by the door, so if it's raining hard, that doesn't work very well. Also there are no lights, so no working after dark.
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Old 09-24-2021, 08:13 PM   #20
jhornbr225
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Default Re: Starting my EZGO Marathon Lithium build.

The Renogy arrived as expected. I installed the holder for the shunt and started running wires when I hit a wall.

According to the documentation that came with the Renogy, basically you tie your battery - to the shunt, and any loads and the charger to the other side of the shunt. All current to and from the batteries goes through the shunt. That way it keeps track of energy going in and out of the batteries.

The problem is, where do I put the black wire from the balance leads?

Logic dictates that I could keep it as close to the actual battery - as possible. Problem is, I know that since I powered up the BMS without hooking up the B- lead from the high current side, that the first two cells didn't show any voltage. So from what I can tell, the - reference for the first cell actually comes from the B- on the high current side, not the black wire balance lead. If I hook the charging lead straight to the battery from the charger, I won't capture the energy going into the battery during charging. If I put that black wire on the other side of the shunt away from the battery, the shunt resistance might cause a small voltage differential between there and the actual battery -.

Maybe I'm overthinking this. I believe on the bottom of the shunt itself there was printing saying that it was rated 75mv at 500A. So at the small currents that I'm charging, and balancing at, the voltage difference will be negligible. Maybe that black lead at the - end of the balance plug really does not do anything. Maybe it's just for powering up the BMS, as the BMS woke up and the Bluetooth module worked, even without the B- lead from the high current side. Even if I was pulling 500A, the voltage on that cell might look 75mV lower that it actually is. Will that cause me to trip out on a differential fault?

Unless somebody has a better idea, I'll think I'll just put both the black lead from the balance plug, and the B- from the high current side on the side of the shunt away from the actual battery -.
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