2.4 Kwh Lithium Battery pack - Fiberglass RV



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Old 07-13-2019, 11:28 PM   #1
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Name: Glen
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2.4 Kwh Lithium Battery pack

Got a little tired of the two golf cart batteries in the trillium, and got the bug for a new project. So I built a 2.4 Kwh battery pack out of 18650 LG batteries.
-7 series, 26 volt nominal
- step down to 13.8 volt
- active balancing
- 45 amp BMS
- 260W MPPT solar charging
- mounted in crush/water proof Pelican case.
- 6 days without solar, 24 days with good sunshine.
- 4 usb charging ports
- 13.8 out and solar in connected via umbilical cord to trailer
- total weight 38 lbs


The whole thing was a little excessive, but it was a creative release for me.
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in case.jpg   Final Layout.jpg  

white.jpg   painted and mounted.jpg  

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Old 07-13-2019, 11:37 PM   #2
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forgot to show the pack assembled. 6 amp fuse from each cell to the bus bars.
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Old 07-14-2019, 06:39 AM   #3
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This seems like a neat project, but is there any advantage to this compared to a lead acid battery? It seems the amount of energy stored is about the same as a group 27 lead acid battery.

--Dan Meyer
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Old 07-14-2019, 07:00 AM   #4
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Originally Posted by Dan Meyer View Post
This seems like a neat project, but is there any advantage to this compared to a lead acid battery?..
One clear advantage is you can just loosen the straps, grab the handle, and easily take the power pack with you anywhere.

Oh wait.. maybe thats a clear disadvantage. But there is always insurance...

(And the 80% discharge.. lots more power actually available compared to lead acid of the same 20 hour rating with its 50% limit).
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Old 07-14-2019, 09:40 AM   #5
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Advantages


1. Portable so we can use it to power devices next time the power goes out
2. my two trojan 6 volts (125 pounds) power pack (38 pounds)
3. Charging is so much faster. Will take full amperage until full
4. I got to build a cool thing


Disadvantages.


1. I burned my self with the blow torch when creating the bus bars
2. Cost ($2000 all in) but then again its a 1200 cycle pack. Double that if i only discharge to 30% (1680 watt hours)



As far a security goes, it has steel holes for a padlock and cable to the frame of the trailer. Also has an umbilical plug inside the trailer for when we are parked. I can plug it in outside for travel and inside for camping.



100 ah 27 group has 600 usable watt hours (to 50% discharge)
This has 1900 usable watt hours (80% discharge)
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Old 07-14-2019, 01:04 PM   #6
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Thank you for the explanation of why this is better.

You did forget another advantage. The pride in making your own solution to the problem, despite burning yourself with the blowtorch.

Thanks!

--Dan Meyer
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Old 07-14-2019, 01:12 PM   #7
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You are correct. It felt pretty good to build this. My wife, however, was very happy when it was done.


I get pretty unreachable when i dive into a project like that.


She does like the extra freedom from an annoying generator to top up when we're camping.


Cheers
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Old 07-14-2019, 05:57 PM   #8
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Good job! I did a somewhat similar project although with a few more goals but about the same capacity & total cost, considering extra tools & things I bought to do it. I have not added up the cost but I think the stuff in the box (also Pelican case) is closer to $1K than $2K. It was also a learning exercise for a home battery, that I can use with my Scamp. It has 4 LiFePO4 160 Ah CALB battery cells (4s) making a 13.3v battery, a 1kW inverter, 220W MPPT, 200W AC to 24V DC converter for grid charging, and weighs 100# (ugh) but fits in the back of the pickup. With 2 flexible solar panels (100W each) in the pickup I can go park in the sun during the day to charge the system and then provide shore power at night.
When not camping I use it to run our home office using only off-peak electricity. The LiFePO4 cells are supposed to be good for many 1000s of cycles.
I havenít tested it to itís limits but it should allow a week to 10 days off grid camping in the shade.
For the money one could put in a couple 100Ah Battleborn batteries, but that would not be as much fun.
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Old 07-14-2019, 07:25 PM   #9
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DougOlson,


That sounds like an awesome power pack. Would love to see a pic if you wouldn't mind.


For me the box and electronics, switches, charger and wires were about $700 CAD, and the 210 x 18650s came to about $1200 CAD. With shipping and duty.


Your right, you could do something similar out of the box for the same money.... But there's no challenge in that :-)
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Old 07-14-2019, 08:25 PM   #10
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I think if I was to build something like that I'd use the much larger prismatic style LiFePo batts, such as these, rather than a bajillion 18650s...

https://www.batteryspace.com/lifepo4...-2vx4-dgr.aspx

(thats a 100AH 12.8V pack made from just 4 LiFePo4 prismatic cells. it can be fast-charged with as much as 100 amps, although that would require a massive charger. 33 lbs total.)
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Old 07-14-2019, 08:53 PM   #11
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Originally Posted by John in Santa Cruz View Post
I think if I was to build something like that I'd use the much larger prismatic style LiFePo batts, such as these, rather than a bajillion 18650s...

https://www.batteryspace.com/lifepo4...-2vx4-dgr.aspx

(thats a 100AH 12.8V pack made from just 4 LiFePo4 prismatic cells. it can be fast-charged with as much as 100 amps, although that would require a massive charger. 33 lbs total.)

Well 210 18650s did make it interesting for sure. I thought about LiFePo4 but I was concerned about size and weight. LiFePo4 is 110 WH/Kg. Lithium Cobalt is 170 WH/kg. More power, less weight-size.



It just took a little (understatement) extra soldering to attach 420 fuses. Sure it was hard work, but the result is pretty compact and light.



Technically I can charge my pack with 90 amps at 26v (2340 watts). 12 volts at 100 amps is 1200 watts...but I would never do that. Like you said... Huge charger and that beats the heck out of the cells. I just use a 25 amp 26v (650 watt) CC CV charger. Takes about 4 hours from dead to full.
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Old 07-14-2019, 09:05 PM   #12
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Also it would take 2 of those prismatics to equal the WH of my pack. the 100 ah 12v prismatic is 1200 WH. My pack full to empty is 2600 WH (100 ah x 26 volts). So the cost would be higher and the package would be heavier and larger.



And I wouldn't have a cool scar from the blowtorch. :-)
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Old 07-14-2019, 11:08 PM   #13
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Pics and a little more detail on thepack I put together

Here are some pics of the system I made.
It's a Pelican 1650 case. The pic showing the top/front of the case has (top to bottom) vent exit fan using 12V PC cooling fan in marine 5" deck portal, AC 120V GFCI outlet, combination switched USB, 12V socket, led light, switches for inverter and DC 24v power supply, Victron BMV712 battery monitor, switches for low voltage disconnect, Grid AC/inverter transfer switch, Solar/grid charging switch, cooling fan switch and cooling portal input.
Backside pic shows (top to bottom ) AC/120V GFCI output, cooling vent out, solar input port, gridf/AC input, LED light.
The inside of the case is not near as pretty as yours but I don't need to open the case except to switch the battery disconnect.
Inside the case (roughly right to left, top to bottom) is the inverter, cell voltage monitor, cooling fan switch, negative shunt, positive busbar, cutoff switch, low voltage disconnect, 12V fuse block, Victron MPPT 75/15 charge controller, AC powered 24V DC supply (for grid charging), LED light switch, cooling fan, AC outlet box, USB/12V DC panel connectors. Then a mess of wires laying over everything. You can ignore my toes at the bottom of the picture.
The battery cells are flat bricks arranged below the internal electronics and the pic shows busbar connections of 3 of the 4 cells. The number 1 cell will be in the upper-left part of the picture.
All the external openings in the Pelican case are meant to be weatherproof but it ended up heavy enough I think it won't end up out of the back of the pickup which has a SnugTop shell. Fortunately this Pelican case has wheels so it's not hard to move until its time to lift it up into the pickup bed. :-)
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Old 07-14-2019, 11:29 PM   #14
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DougOlson,


That pack is great! A thing of beauty! Nice work. I like the cooling fan, I'll have to monitor my temps during use to see if I'll need one. I was trying to keep the case water tight, but I may have to rethink that. So far each of the 210 cells puts out no more than .16 amps during regular operation. I suppose if I slap an inverter on there, that will change. For home use I can just open the case, but camping is a different story. I guess the choice comes down to Kuerig, or stick with cowboy coffee.
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