Yes, the original was one piece. @grantwest and I designed a two piece which was quickly copied on the production model.
As you guessed, I only use it for testing.
Gemrix ,
can you tell us about the solar boost you are going to add to your gem ?
I am researching that part of the project and I will be posting that soon. 
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On Board Solar Charging
As I mentioned my first GEM purchase was soon after installing solar (photovoltaic) at my home.
Background on the solar install (if you are interested)
I have several spare solar panels because I ordered whole pallets when I installed my solar array in 2016. I figured if one developed a defect or became damaged I could easily swap it out with a matching one rather than trying to find a match. As of today they are still stored in the workshop, not far from the GEM.
One of the things that made my solar installation economically feasible was the 30% solar (and wind) tax credit called the ITC (Investment Tax Credit). For my installation, I did get some quotes for 20.1 Kwp array that I needed to offset all of our annual energy use. We use more electricity than average because I also installed a geothermal heating and cooling system in 2011. Of course the trade-off is that we use very little propane, just for a portion of the water heating, cooking, and the standby generator. In 2011 the quotes were over $100k. In 2016 the quotes were about $65k with a long payback period. I decided to educate myself and just do it as I usually do. I have been a big time do-it-your-selfer for years.
I actually ran 2" conduit down to the field about 300’ in front of our house as I was back filling the geothermal pipe in the ground in 2011, thinking “If I install solar down here, that would eventually make all of our energy free.” I dug up the end in the spring of 2016 after breaking even on the geothermal (vs. traditional gas heating and electric cooling). The system went online in the fall.
I had just over $34k in the project all said and done. With the tax credit the net was just about $24k. I am currently on pace for a 9 year payback. Actually, it was kind of a zero year payback because I refinanced the house from 30 to 15 years and “paid” for the solar with the interest savings.
The Photovoltaic GEM
Now that I am getting to the GEM upgrades, I thought it would be cool to use one of the spare panels on the roof rack. Even though the panels are high powered, (340w 72 cell 37.8v) I realize that even under ideal conditions this is basically a trickle charge. Although, it would be a pretty sweet ride in a doomsday scenario.
Adding the solar panel would actually reduce the net cost of the system after the 30% tax credit. I found that I am not the first to think of this approach. My solar install is grid tied with no battery storage currently installed. With net metering, it is not necessary unless you want or need to be off-grid. I do have a 2,000w dual conversion battery backup that powers all the electronics in the house with dedicated electrical runs and a propane standby generator but no large scale battery backup.
How to Make it Work
I found that there are very limited options for a charge controller. Usually charge controllers are using higher voltage photovoltaic panels to charge lower voltage battery systems like 12-48v typically. For example 37.8v panels wired in a series of 10 = 370v. This is DC-to-DC conversion is usually accomplished by a “buck” converter. The GEM, as you may know, has a built in buck converter to create a 12v supply from the 72v battery pack. What I need is a charge controller that does a “boost” conversion. As it turns out this is a rare animal. I could only find two options.
The version of this one the one in the video is CTK-EV-300 but they make a CTK-EV-600 which could handle up to a 600w panel.
https://www.amazon.com/MonkeyJack-Waterprrof-Controller-Regulator-Intelligent/dp/B06XY27K2X/ref=pd_rhf_dp_s_cr_simh_0_2/139-8261333-1124919?_encoding=UTF8&pd_rd_i=B06XY27K2X&pd_rd_r=459cfd23-d3fb-496d-8932-90addf516ff5&pd_rd_w=sCf2K&pd_rd_wg=3UAIN&pf_rd_p=31caee8f-ce20-49ad-9f29-d71df297ad52&pf_rd_r=2NH1F5MB9Y8WQ4N9QD10&psc=1&refRID=2NH1F5MB9Y8WQ4N9QD10
One of the many re-branded versions of this unit made by Ming He.
https://www.amazon.com/Docooler®-Battery-Regulator-Charge-Controller/dp/B01HCL7LEW/ref=sr_1_1?hvadid=221588975405&hvdev=c&hvlocphy=9006414&hvnetw=g&hvpos=1t1&hvqmt=e&hvrand=16366501519199706323&hvtargid=aud-649564993678%3Akwd-309977320709&keywords=mpt7210a&qid=1556507932&s=gateway&sr=8-1#customerReviews
This Guy has 3 videos about this controller
I am going to get the green one to try because there is more information about it with videos, reviews, and many sold. The green one has an unnecessarily loud fan and resets frequently with even small changes in sun / shade conditions. Because of this, it may be best to only run it while the vehicle is parked. Actually maybe this is for the best anyway. I may end up mounting it in a different case with a larger, quieter fan. I am also considering separating the screen and control to mount it separately. They are cheap and apparently can get the job done. I am not thrilled about either option so I am still looking.
One question: what voltage should I set this to? I thought it should be slightly higher than the nominal 80v to top off the pack with solar when available. It is not as much current and more like a trickle charge. 4.1 x 20s = 82v? Is this a safe maximum? will the BMS allow this?
I am going to meet Dave & pick up the battery pack unit tomorrow!
These are expensive and a hassle to ship but it could be done. After talking with Dave for a while I decided it would be worth the trip. I figured a way to do it in one long day.
I live near Erie, PA about not far from I-90. Dave is also just a few miles from I-90 and about 750 miles west.
I have geo too. Since 2002, matter of fact, I just got back from picking up a new 6 ton heatpump delivered to 7Rivers next door. 
OId one is still running. Desuperheater pump went out, so thought it’s time to update system.
82v is fine. Can you set charger to only come on when a few amps are available? Some frown on trickle charging. Google it to decide.
There is a certain amount of current required before the charger will start but I will have to investigate what that is and if it can be adjusted.
Battery pack, equipment, and I arrived home safely. It was so nice meeting Dave and his wife. I highly recommend dealing with @Inwo and purchasing from him with all the “free” advice included.
In other news, the inverter arrived in record time in only 6 days FedEx straight from China (another good mark for the above mentioned eBay seller who apparently is employed by the manufacturer).
Waiting on the solar charge controller and some other odds and ends. I will be champing at the bit to get going on the install.
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I just finished reprogramming the Delta-Q charger with the software and USB interface.
On the GEM the red wire from the battery charger is attached to the lower left lug of the fuse panel. I disconnected the red wire and attached it to the alligator clip of the programmer. The black wire was a little hard to trace. it goes back through the foam “firewall” and is connected to the top of the gray controller box under the black flap. I did not disconnect this, just clipped onto the lug.
In the software, I could see that it was set to profile 24 which was a High capacity Deka Gel profile and software 2.12. Dave instructed me to use profile 128 (which goes to 82.044V) and software version 1.72. Firmware was unchanged.
Now I can ship the programmer back to Dave. Thanks for lending it to me.
By the way, where should the original 250A fuse be? I should include it, yes?
There was some discussion on this here.
Originally it was wired in the middle of the series of lead acid batteries (If I recall correctly). In my case, with the split pack, I was thinking it could (or should) be wired to interrupt the positive lead on the way into the battery pack. Negative could work also and would solve my potential issue with the shorter length of the negative wire. However, I think the conventional wisdom is that placing it in the positive side of the circuit would afford more protection. Please advise as to best options and why.
Positive or negative, no difference. It’s a non-grounded circuit. Both carry and can interrupt/protect full current.
Do not put it between modules, as an interruption of inter-cell connections will damage bms.
Using it as a splice in neg line is a good idea. Best practice is to connect all neg wires to load side of fuse. Shunt can stay at battery.
Can you send the programmer file to @grantwest ?
I’m going to look for it on line too.
Try this.
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It is awesome that you guys are sharing all this info on the net. Inwo and Rodney are the best. I couldn’t have done mine without them.
Thanks again.
@grantwest let me know if you still need the programmer software.
Started working on the install just the other day.
I was able to get the battery pack in by jacking up the GEM, then wheeling it under on a dolly. Next, I lowered the GEM as the pack went up through an opening in the frame just behind the battery tray. The battery still needed to be raised up a bit so I did that with levers and blocks. Finally, I gently slid it into the tray & onto a vented rubber mat that I trimmed to fit.
I talked about using a bin to protect the battery but that did not end up being a good fit. Instead, I built a custom box from 11" wide x 3/4" thick white plastic Trex boards. The top cover is a fiberglass sheet. I am going to add a foam gasket seal for the top. There are also aluminum louvered vents front & back for heat dissipation. I do have the temperature probes from the BMS so I can monitor the internal temperature. If the inverter, for example, generates more heat than anticipated, I could add a duct or a case fan. Before, the tray just had batteries, so a spray, or dust, or pests was would not have been a problem.
This will shield the battery and all the electronics I am adding from the elements.
@Inwo One question: what is the little silver wire sticking out from the one end of the com2 cable that connects between the BMS brain and screen? I Thought it might be for a ground. If so, which end and ground to what? The frame of the GEM is not part of the electrical system AFAIK. I have taken measures to isolate 80VDC primary battery supply, 12 VDC accessory converter, inverter 120 VAC, and I even have a 72-to-5 VDC supply to operate the addressable LED pixel strips I am using for lighting.
Moving right along with the install… The box is re-assembled in the tray. BMS mounted and actively balancing. Inverter mounted.
I popped open the inverter to add an extension wire to the power switch so I can switch it from the dash. The switch just controls a relay switch for the high current. Looks to be well made.
Ignore the wire. It’s the shield.
Good practice is to ground it on one end only. You are correct, there is not a common ground to work with.
Thanks @Inwo
Next, I just want to verify that this is where the white wire to enable / disable the DQ charger goes. This comes from a bundle of red, green, black, white from the DQ. Does the orange with black stripe wire get left off or reconnected? Looks like the connector you put on it is to reconnect the orange wire but did not want to assume.
