Great, yes much better way to go.
DIY Lithium Packs, Proposal and Discussion
- Thread starter luthj
- Start date
luthj
Engineer In Residence
Submitted an order for battery box parts. $175 cut and delivered in clean 16 gauge steel. Should have them in 2 weeks. I am going to cut through a floor support beam. I am not particularly worried about floor integrity. Given my load and how the box attaches. If necessary I will rivet or weld a section of tubing for additional support.
luthj
Engineer In Residence
Decided on Orion Jr 2 with canbus. I will install a CAN to bluetooth adapter for monitoring. I think i will also use a Hall effect current sensor instead of tapping into my existing 500A shunt. The wire run to the shunt is ~6ft, and there is interference risk.
I also ordered a heating pad. This model. Its a bit big, but should fit on the bottom of the box. It has a built in thermostat that is 45F on and 68F off, which should do a good job.
I also ordered a heating pad. This model. Its a bit big, but should fit on the bottom of the box. It has a built in thermostat that is 45F on and 68F off, which should do a good job.
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bgflyguy
Member
I have two sets of batteries inbound. I don't know which will end up in the ambulance, but I'm hoping for the lifepo4's since they have considerable more wattage.
I placed an order with batteryhookup for 8 lg chem n2.1 120ah cells ( https://batteryhookup.com/products/new-lg-chem-n2-1-3-7v-120ah-cell-module ) and then placed an order with Dongguan Lightning Energy Technology Co., Ltd (https://www.alibaba.com/product-detail/Free-Shipping-8pcs-3-2V-280Ah_1600059397971.html ) for 8 lifepo4 EVE 280ah cells. I'm still looking for the BMS, but i'll probably end up with DALY. I will need a few, so I might order a couple of different ones. I figure it's worth it to test a few things and get the right solution for something like this. Even if I over buy on this, I'm still going to come out way better than Renogy etc. in terms of material cost.
I'll probably build a simple pack with all-thread and whatever backing material I can find. That box looks awesome though.
I placed an order with batteryhookup for 8 lg chem n2.1 120ah cells ( https://batteryhookup.com/products/new-lg-chem-n2-1-3-7v-120ah-cell-module ) and then placed an order with Dongguan Lightning Energy Technology Co., Ltd (https://www.alibaba.com/product-detail/Free-Shipping-8pcs-3-2V-280Ah_1600059397971.html ) for 8 lifepo4 EVE 280ah cells. I'm still looking for the BMS, but i'll probably end up with DALY. I will need a few, so I might order a couple of different ones. I figure it's worth it to test a few things and get the right solution for something like this. Even if I over buy on this, I'm still going to come out way better than Renogy etc. in terms of material cost.
I'll probably build a simple pack with all-thread and whatever backing material I can find. That box looks awesome though.
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hour
Observer
Shoo, I have 3 Dalys sitting around now that I swapped out in favor of chinese smart bms units. No problems now for almost a year on my 200+ah lifepo4 job running a 60a bms in negative and 110*F+ temps. Low/high cell/pack cutoff works great as does low temp disconnect. Tracks capacity just fine, only reason I still run a BMV712 is because I had it and it was already installed, and it's a redundancy for low temp cutoff mated to a Victron MPPT. Any reason you're not eying those?
edit: like luthj posted here. Not sure that pic is accurate though on Amazon, mine came without wires and is the size of an ipad.
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luthj
Engineer In Residence
Got the battery box steel earlier this week. Came together okay, though I am regretting not getting a rental bottle with C25 shield gas.
IMG_20200718_101017545
IMG_20200718_101240667
IMG_20200718_113936051
IMG_20200718_132334698
IMG_20200718_101017545 IMG_20200718_101240667 IMG_20200718_113936051 IMG_20200718_132334698
luthj
Engineer In Residence
Over in the Van build thread, I cut a big hole in the floor...
Did the deed.
Quite a bit of Australian terra firma was sequestered inside the floor support. I have no idea how it got in there, as the biggest hole is only 0.45"...
IMG_20200722_122203037_HDR
luthj
Engineer In Residence
Making progress on the box. Everything is fitting so far.
I am working through the BMS specs, and making a wiring diagram. Since the Orion Jrs outputs are limited to 175mA, I need amplification/relay control. Something in the 5A range should work. Anybody got a solid state relay suggestion? I need low power consumption (<1mA is ideal) and 10-15V input.
I am starting to fill out a profile in the Orion software. I wasn't able to find detailed specs for the Eve 280AH cells. So I had to extropolate the temperature/performance data from the few points available, and some references from similar cells.
The BMS documentation on the charge/discharge inputs, safeties, and the various min/max voltage fields is a bit vague in places. I am figuring it out with the flow charts, but most of it will get turned off, as my chargers don't support current limiting via external input. Besides, I shouldn't ever exceed 0.5C worst case.
I am working through the BMS specs, and making a wiring diagram. Since the Orion Jrs outputs are limited to 175mA, I need amplification/relay control. Something in the 5A range should work. Anybody got a solid state relay suggestion? I need low power consumption (<1mA is ideal) and 10-15V input.
I am starting to fill out a profile in the Orion software. I wasn't able to find detailed specs for the Eve 280AH cells. So I had to extropolate the temperature/performance data from the few points available, and some references from similar cells.
The BMS documentation on the charge/discharge inputs, safeties, and the various min/max voltage fields is a bit vague in places. I am figuring it out with the flow charts, but most of it will get turned off, as my chargers don't support current limiting via external input. Besides, I shouldn't ever exceed 0.5C worst case.
dreadlocks
Well-known member
luthj
Engineer In Residence
Yeah, I have a few spares from the 4x4 display panel lying around to play with. After reviewing the specs, it looks like the relay pins are good to 60V and 175mA, so I don't need isolation, just a sufficient resistor to limit current under max transients.
Buried in the BMS manual is this example, though I would just swap the relay to the V+ side, as I am using a blue sea one with internal logic.
I am also considering if I need a relay to drop the PV input for safeties sake. Since it would be on all the time, I need something with very low power consumption that can handle up to 60V and 20A. Not much in the mouser catalog at reasonable price. The Victron battery protect 65A would be perfect, but its limited to 32V. They have a 48V version, but its 100A and 140$. I guess I could pick some FETs with low RDS and make my own solid state relay. Given the output is safe to 60V, I wouldn't need isolation for PV output control. I just need to keep the voltage drop under 1% at 20A, so a few in parallel would be required. That and a beefy heatsink,
dreadlocks
Well-known member
what solar charger are you using? I know with my Victron 100/30 & 50 they sell this doodad that would work great w/BMS: https://www.victronenergy.com/cables/ve-direct-non-inverting-remote-on-off-cable
luthj
Engineer In Residence
Unfortunately I am using a outback flexmax, older version. The only way to remote control it would be hacking their proprietary bus. Which has mostly been done, but I would need a bunch of work to send commands...
Looks like there are some 4 channel FET boards for arduino/prototyping. With RDS of 70 mOhm, I could run all 4 channels in parallel for 1% loss at 20A. I need to figure out what the power consumption of the board is though, as its using opto isolators, which probably eat a few mA each.
Amazon.com: NOYITO 4-Channel MOSFET Switch Module IRF540 Isolated Power Module (4-Channel, Red) : Electronics
Amazon.com: NOYITO 4-Channel MOSFET Switch Module IRF540 Isolated Power Module (4-Channel, Red) : Electronics
www.amazon.com
dreadlocks
Well-known member
You can fire up the free version of eagle, put in the dimensions of your favorite project box, draw out a board and send it off to OSHPark and in a few weeks you'll have 3 boards in your mailbox for a few bucks if you wanna whip out something more designed for your needs.. could get 3 hand made "solid state" relays for less than the cost of a battery protect, takes time and work tho.
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