Teej's Honda Element Tiny RV

[tjoiner1986]

Van lifer here.

A few months ago, my 100 Ah AGM battery began failing -- only getting about half the capacity that I used to. Rather than drop $200 on a replacement, I took the plunge and began making the transition to a 280 Ah LiFePo bank made from EVE cells with a 120A Daly Smart BMS (Bluetooth, UART, etc.), all from AliExpress. I'm running two 12V 100W panels through an EPEVER Triron 2210N (20A MPPT). I'm considering replacing that charge controller with the 30A MPPT/charger from Renogy so I can have the alternator charge my battery bank at night or on rainy days.

Currently, I'm waiting for ring terminals and Kapton tape to arrive (should be today) so I can connect the BMS and bind the battery cells together. Yes, I'm aware of compression/fixture and the various methods and opinions people have regarding it.

I have not attempted top balancing as I've read conflicting reports on whether it's necessary or not. And I'd rather not drop $70-80 on a power supply I'll only use once. Ultimately, I will probably do it anyway just for peace of mind.

All of the components I'll need -- breakers, wire, etc. -- are in my Amazon cart EXCEPT the inverter. I'm torn between the Giandel 1200w pure sine and the Renogy 1000w. I'm leaning toward the Giandel due to it's smaller size being able to fit inside the milk crate.

Oh yeah, this is a milk crate build. I already have the crate but I'm thinking of building a plywood box roughly the same 12" width of the crate but about 18" long since the crate, along with the plywood cover I made for it, currently doubles as a tabletop and food prep surface.

I guess my reason for this post is just to document the progress and to get feedback. Being new to LiFePo, I'm certain there are things I'm missing or not understanding entirely.

 

[Bud Martin]

How much power (Whr/day) do you use daily?
200W worth of panel will give you 1000Whr/day, but in actuality, it will be about 80%.

 

[tjoiner1986]

Truthfully, I've never actually calculated that. It's not much. I can safely say that.

I have an Iceco VL60D that runs on 12V. Uses 60-65W when running. That's actually the only appliance I've had until I recently purchased an Instant Pot Duo Plus (3qt, 700W) so I could cook inside. Something I can't do with my propane Camp Chef stove. If it weren't for the Instant Pot, I could easily do without an inverter but as long as I'm considering an inverter I'd like to be able to plug in my little 15W soldering iron for the occasional project or repair and possibly the battery charger for my 24V Kobalt cordless tools.

Other than that, everything else such as phone and laptop can be charged via the 12V socket in my car. I'm a minimalist so no microwave, blender, or 55" TV in here, although I've thought about adding a small (15"?) monitor so I can watch movies and shows on something other than my phone.

 

[Bud Martin]

As long as you can charge up the battery back up the next day after discharged during night, you will be OK, it is good to audit the power consumption so you can manage and reduce the power waste.

 

[tjoiner1986]

Oh absolutely. When I only had a single 100W panel and the old 100 Ah AGM battery, I also had a smaller fridge that used about 35W and I was able to go about 3 days on JUST a full battery. I could go indefinitely when adding solar to the mix. That's why I'm thinking of swapping my current charge controller with the Renogy DCC30S. That way I can charge the battery bank off the alternator if necessary.

 

[tjoiner1986]

I ended up going with the Giandel 1200W inverter (the red one because it was $13 cheaper for some reason).

Additionally, I grabbed:

• 100A breaker to wire into the inverter (because 1200 watt inverter / 12.8 system volts = 93.75 amps)
• 15 feet of both red and black 4 AWG wire with lugs & heatshrink
• Kungber Lab variable power supply

I'm going to hold off on replacing the MPPT for now. I need to do more research into low temperature protection first. I know the Daly BMS has a low temp cut off but I want redundancy.

• Victron has a low temp cutoff but they don't make a combined charge controller/DC-DC charger.
• I'm not sure if the Renogy DCC30S has low temp cutoff.
• The EPEVER I have now supposedly does. I've considered keeping that charge controller and adding a DC-DC charger but it would really be nice to have an all-in-one unit like the Renogy.

 

[tjoiner1986]

The inverter, wire, power supply, and breaker all arrived. I have not been able to do anything with any of it, however, since I don't have a place where I can top balance. That's why this morning I brought the battery pack, BMS, and power supply to work with me hoping I could hook it all up in my down time.

Once I had some down time, I realized I have it all connected in series in preparation to connect the BMS. I thought I read somewhere that an alternative method for top balancing is to build the complete back and then somehow top balance before connecting the BMS. I must have misread because when I re-checked the tutorial PDF here on the site it was in line with Will's demonstration video. So, I removed the tape and began removing the nuts from the studs. While removing the nut from the (+) of cell 3 -- the (-) of which is still connected to the (+) of cell 4 -- I accidentally touched the (-) of cell 4, thus completing a circuit and sending a lovely shower of sparks in all directions and obliterating the top of the stud. That's what happens when you don't have the proper tools with you and you decide to use a pair of pliers instead of a socket wrench.

That was only two cells. Imagine if I shorted out all four!
Thankfully, no injury but I'm mostly glad my supervisor or boss didn't see.

I also realized that I need at least 6 bus bars. I only have 3 but I could have sworn more were included. Just can't find them.

EDIT: I just measured the voltage of each cell.

Cell 1 - 3.30 V
Cell 2 - 3.30 V
Cell 3 - 3.30 V
Cell 4 - 3.30 V

Believe it or not but they are all 3.30 V. Each started higher but settled. Cell #3 bounced between 3.29 and 3.30.

Also, I'm realizing the 4 AWG wire might not be enough to connect to the inverter. 1200 W inverter / 12 V = 100 A, right? 4 AWG cable is only rated to 85 A. Then again, that's assuming I ever decide to plug in something that draws all 1200 W which I definitely don't plan on. At most, I'm thinking 750 W max from the Instant Pot, and that's being generous with the wattage (manual only says 700 W). For such a short run between the battery pack and inverter, however, I'm thinking "better safe than sorry" and grab a couple feet of something beefier. Or am I overthinking?

Also also, the milk crate is only temporary. Initially, it was going to be permanent but then I've since to built a nice lidded box out of 3/4 ply so that I can house everything -- battery pack, inverter, breaker(s), and possibly even the MPPT and/or future DC-DC charger so I can charge off the alternator. Internal dimensions are 12.5" x 17" x 11.5" (W x L x D). The new box is almost done. Just have to apply the finish.

 

[tjoiner1986]

Just ordered some 1/8" x 3/4" copper bar stock from Online Metals. Yeah, I know copper pipe can be used -- it's cheaper and readily available -- but I like things that are over-engineered. These beefy copper bus bars should never need replacing or upgrading.

 

[tjoiner1986]

The copper arrived and I made 5 or 6 beefy bus bars over the weekend.

On Monday, I brought my setup to work since I currently don't have steady 120V access (because van life) to feed the power supply. Began charging/balancing to 3.65 V @ ~9.25 A at 11:15 and ran it until I left at 5:00 PM. I disconnected when I left the office. Didn't want to leave the power supply running overnight and unattended in case it caught fire and burned the office down. When I started, the power supply read 3.46 V at 9.26 A (see photo).

Tuesday, I ran it from about 7:45 AM until 5:00 PM. Ended the day with 3.51 V @ 9.25 A (see photo).

I was expecting this to take around 60 hours -- assuming 50% SoC, that's 140 Ah x 4 cells = 560 / 9.25 A charging current because I didn't want to run this cheap Amazon power supply at full throttle = 62.2 hours -- however, seeing as the power supply's amp reading is currently plummeting as I type this (7 A and falling fast), it looks like I'm almost done. I guess these batteries shipped at more than 50% SoC. Granted the voltage reads 3.63 and the current drop has since slowed way down (~2.7 A). I will wait until the current reads as close to zero as it's going to get. Perhaps by then I will be right at 3.65 V.

I'm not in a rush to get the solar set up charged and assembled. Honestly, in typical me fashion, I'm debating/overthinking heavily between the two charge controllers I have acquired -- Renogy DCC30 and MPP Solar 1012LV. I need to just put my foot down on one and keep it there. The MPP Solar doesn't feature a low temp cutoff. I feel it's a much better quality unit but I don't want my battery's BMS to be the only layer of low temp protection. Redundancy please! That's why the Renogy wins here.

I really feel the 1012LV is better suited for applications where the climate is more stable, where the batteries won't be subjected to the cold such as a heated cabin or a van that stays ahead of the winter weather. Ideally, I would simply travel elsewhere when the weather got this cold but that's not an option for me right now. Lately, I'm waking up to outside temps in the mid to upper 20s with wind chills in the teens. Not sure what the temp in my Element is on those days. I should get a thermometer so I can find out. I stay toasty thanks to layers of thick warm blankets but I would worry about $500 worth of LiFePo cells. Perhaps I should look into a heating device? Man... this is getting complex.

1.92 A and falling. Voltage still at 3.63.

 

[meetyg]

The copper arrived and I made 5 or 6 beefy bus bars over the weekend.

On Monday, I brought my setup to work since I currently don't have steady 120V access (because van life) to feed the power supply. Began charging/balancing to 3.65 V @ ~9.25 A at 11:15 and ran it until I left at 5:00 PM. I disconnected when I left the office. Didn't want to leave the power supply running overnight and unattended in case it caught fire and burned the office down. When I started, the power supply read 3.46 V at 9.26 A (see photo).

Tuesday, I ran it from about 7:45 AM until 5:00 PM. Ended the day with 3.51 V @ 9.25 A (see photo).

I was expecting this to take around 60 hours -- assuming 50% SoC, that's 140 Ah x 4 cells = 560 / 9.25 A charging current because I didn't want to run this cheap Amazon power supply at full throttle = 62.2 hours -- however, seeing as the power supply's amp reading is currently plummeting as I type this (7 A and falling fast), it looks like I'm almost done. I guess these batteries shipped at more than 50% SoC. Granted the voltage reads 3.63 and the current drop has since slowed way down (~2.7 A). I will wait until the current reads as close to zero as it's going to get. Perhaps by then I will be right at 3.65 V.

I'm not in a rush to get the solar set up charged and assembled. Honestly, in typical me fashion, I'm debating/overthinking heavily between the two charge controllers I have acquired -- Renogy DCC30 and MPP Solar 1012LV. I need to just put my foot down on one and keep it there. The MPP Solar doesn't feature a low temp cutoff. I feel it's a much better quality unit but I don't want my battery's BMS to be the only layer of low temp protection. Redundancy please! That's why the Renogy wins here.

I really feel the 1012LV is better suited for applications where the climate is more stable, where the batteries won't be subjected to the cold such as a heated cabin or a van that stays ahead of the winter weather. Ideally, I would simply travel elsewhere when the weather got this cold but that's not an option for me right now. Lately, I'm waking up to outside temps in the mid to upper 20s with wind chills in the teens. Not sure what the temp in my Element is on those days. I should get a thermometer so I can find out. I stay toasty thanks to layers of thick warm blankets but I would worry about $500 worth of LiFePo cells. Perhaps I should look into a heating device? Man... this is getting complex.

1.92 A and falling. Voltage still at 3.63.

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Just a little note on your top balancing:
In order to get best top balance across all cells, you should connect the positive and negative cables to opposite ends of the parallel pack.
You connected both to the first cell, which will cause that cell to reach higher voltage and SOC first, while the others will lag a bit behind...

 

[tjoiner1986]

Ahhh, I didn't think of that! Thanks for the tip.

As of earlier this afternoon, it's still top balancing. Strangely (to me anyway), the current went up from it's lowest point of about 1.4 A to around 2.5 A. Voltage readout from the power supply is mostly steady at 3.63 V with the occasional blip of the target voltage of 3.65 V.

The pack is currently charging at my mom's house. When I go there in the morning, I'll move one of the leads to the opposite ends. I really hope this finishes before Monday. I'm itching to get everything finished so I can finally hook everything up, power on the fridge, and enjoy fresh food again.

 

[tjoiner1986]

Just a little note on your top balancing:
In order to get best top balance across all cells, you should connect the positive and negative cables to opposite ends of the parallel pack.
You connected both to the first cell, which will cause that cell to reach higher voltage and SOC first, while the others will lag a bit behind...

I just now swapped the positive to the other end.

Currently showing:
3.63 volts
5.27 amps
19.17 watts

 

[tjoiner1986]

I would think that after charging all weekend, 24 hours a day, that I'd see that current at or close to zero.

Currently showing:
3.63 volts
5.33 amps
19.38 watts ?

 

[meetyg]

Check the cell voltages with a multimeter, just to make sure the voltage your PSU is displaying is somewhat correct. It's OK if the PSU show a bit higher voltage than the cells are, but I'm worried that maybe it may show 3.63v but actually is pushing out more than that, and may be over-charging the cells.

 

[tjoiner1986]

Check the cell voltages with a multimeter, just to make sure the voltage your PSU is displaying is somewhat correct. It's OK if the PSU show a bit higher voltage than the cells are, but I'm worried that maybe it may show 3.63v but actually is pushing out more than that, and may be over-charging the cells.

That was my concern as well. I didn't have a multimeter on my when I went to check the pack during my lunch break. I'll check after work in just a couple hours. Thanks!

 

[luckielab]

Was curious if the charger was disconnected from the cells whenever the voltage was changed?

 

[tjoiner1986]

Was curious if the charger was disconnected from the cells whenever the voltage was changed?

Voltage was never changed. I started charging last Monday, off and on, but have not touched the power supply except to turn it on/off when needed. Only time I disconnected from the cells was last night when I moved the positive cable to the opposite end.

 

[tjoiner1986]

Totally off the current topic but the other day I decided to try out this BMS:

101.94US $ |JBD 100A 150A 200A BMS With Balance Smart Bms 4S Lifepo4 BMS 12V With Free Bluetooth Temp Sensor Lithium Battery H Means Heating|Battery Accessories| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

JBD seems to me more reputable and reliable than the Daly smart BMS I currently have. Got the 150 amp version instead of the 120 like I did with Daly. Plus this one has output for heaters!

 

[tjoiner1986]

Check the cell voltages with a multimeter, just to make sure the voltage your PSU is displaying is somewhat correct. It's OK if the PSU show a bit higher voltage than the cells are, but I'm worried that maybe it may show 3.63v but actually is pushing out more than that, and may be over-charging the cells.

Cell 1: 3.56
Cell 2: 3.34
Cell 3: 3.33
Cell 4: 3.33

I took everything apart so I could measure the individual cells. Should I charge each cell to 3.65, one by one, or put it all back in parallel and let it resume?

EDIT: I believe what I'll do is parallel cells 2, 3, and 4, charge it to 3.56, and then charge the whole pack to 3.60.

 

[tjoiner1986]