DIY 100ah Lithium Battery (1 Viewer)

[Otter]

I originally posted this in the "What did you do..." thread, but decided to make an individual thread for it so I could post performance updates.

I added a 100ah lithium battery to my system. I've had a Batteries Plus X2 Group 31 AGM for several years and running all of my aux power needs off of that. With a 100ah AGM, you really only have about 50ah of useable power without killing the battery. It's served me pretty well, and never ran it too low to not crank the truck. I've had 100w solar panel mounted to my RTT for a good portion of that time, and it has always kept the battery topped off, even when parked for multiple days with the fridge running. However, I still had some anxiety and wanted to increase my capacity. I considered just getting another AGM since an off the shelf 100ah lithium can cost anywhere between $600 and $1000. At best any cheaper AGM would cost around $200 and might only give me another 25ah.

So I considered building a diy 100ah lithium battery. I purchased four raw 100ah cells and a battery management system (BMS) for about $300 (could've been $200, but I splurged on a BMS with bluetooth and a low temp cutoff. I assembled the cells in series and mounted the battery and bms in a Harbor Freight plastic ammo can. The whole thing weighs probably 15lbs, which is a considerable savings over another Group 31 lead acid battery. I added a 120a breaker on the inside and a Anderson plug to connect it my truck's electrical system. The starting battery and lithium house battery are connected to the same power posts in my electrical panel in the cargo area. I can flip the breaker switch on my starting battery and connect the lithium, or I can pull the lithium out of the truck and reset the breaker on the starting battery. My solar and shore power chargers will charge whichever one is connected.

We'll see how it works long term.

Here's a pic of the cells as they arrived

Balancing and fully charging the cells in parallel

Capacity testing with fan device on the left, BMS on the right, and cells connected in series in background

Battery fully assembled inside plastic ammo can

Mounted on platform next to electrical panel in cargo area

 

[Otter]

We camped on Mount Mingus starting later Thursday afternoon through Saturday morning. Our 50L Dometic fridge ran the entire time, plus minor charging of phones, lights, white noise machine at night, etc. Max power draw was probably 7 amps total if everything was going at the same time.

From the time we left the house, the only battery charging was done via the rooftop 100w flexible solar panel, which is two years old now and may generate a max 70w in full sun.

According to the battery management system, each morning before the sun came up, we were down to 87-90 amp hours remaining.

The solar panel would typically have the battery fully recharged before we finished breakfast.

Here's a screenshot of the BMS app.

Additionally, before we left for camping, I used my puma compressor to top off my tire pressure. The compressor was pulling between 35 and 40 amps while running. The Lithium handled it with no issues and was fully recharged on the drive up to Mingus.

Typically we only run the compressor at the end of a trip, so I have minimal concerns about this draining the battery too much to affect my power needs.

 

[sdnative]

Nice work! I did something similar and it works great. I opted to skip the solar charging and just use DC-DC but I may add solar if I find myself in one spot for several days.

DIY LiFePO4 battery install under ARB drawer wing

I have been considering a second battery for aux loads since I bought the truck about a year ago. I went through a few iterations before ending up where I am now. Goals were to power aux loads like the fridge, lighting, radio gear, charge devices, etc for several days while camping, jump start...

forum.ih8mud.com

 

[Otter]

Nice work! I did something similar and it works great. I opted to skip the solar charging and just use DC-DC but I may add solar if I find myself in one spot for several days.

DIY LiFePO4 battery install under ARB drawer wing

I have been considering a second battery for aux loads since I bought the truck about a year ago. I went through a few iterations before ending up where I am now. Goals were to power aux loads like the fridge, lighting, radio gear, charge devices, etc for several days while camping, jump start...

forum.ih8mud.com

Yeah, I saw your post. Nice work. I already had the Victron solar and shore power chargers. I left a spot in my electrical panel for a dc-dc charger, if I find I might need it. I didn't really want to buy another charger. I would also have to change some wiring connections in my panel, if I added the dc-dc charger.

 

[Highway Romping]

I think I'm going to go with a similar setup once I get my camper. Next time I see your truck, I'm going to draw a crude schematic of your wiring.

 

[Otter]

I think I'm going to go with a similar setup once I get my camper. Next time I see your truck, I'm going to draw a crude schematic of your wiring.

Happy to help any way I can

 

[Dissent]

Nice work! I'm running a 27 series X2 and love it but have been looking at a 2nd for more capacity. I saw a few YouTube videos about building a pack like this. May play with that when I get settled.

 

[LandCruiserPhil]

NIce clean work Otter
How are you addressing the different charging profile for the lithium?
Do the batteries come with any warrenty?
How low have you run the batteries?

 

[Otter]

NIce clean work Otter
How are you addressing the different charging profile for the lithium?
Do the batteries come with any warrenty?
How low have you run the batteries?

Thanks, Phil.

When I swap out the batteries, I change the charging profile using the Victron app to the appropriate battery.

No warranty whatsoever. Fair warning: If you have any issues with the cells, good luck getting a replacement. To return, you'd have to pay freight to China. Best option is to buy from a reputable source, which is going to be based on prior purchasers' recommendations via online forums. diysolarforum recommends purchases from one particular vendor for grade A new cells the last time I was on the forum. I'd check there before I buy another set. I'm really leaning towards some 280ah cells some time in the future.

I did a load capacity test after the cells were balanced and assembled in series. The BMS stopped the discharge when one cell bottomed out at 2.5v. The battery itself is supposed to shut down at 10v. One cell hit 2.5 before the others, so the BMS shut everything down. The tester gave a capacity at around 98 ah.

 

[Funner]

Hey Richard, interesting solution. Is this completely divorced from the 100 series wiring/charging system?

 

[Otter]

Hey Richard, interesting solution. Is this completely divorced from the 100 series wiring/charging system?

When the lithium battery is connected, yes. If I pull the lithium, I can reset a breaker in the engine bay, then everything will be connected to vehicle's charging system.

 

[Funner]

When the lithium battery is connected, yes. If I pull the lithium, I can reset a breaker in the engine bay, then everything will be connected to vehicle's charging system.

 

[Otter]

As an experiment, I purchased a portable 1800w induction cooktop and a 1500w continuous pure sine inverter. I wanted to see if this was a viable option for camp cooking. I've got a couple stoves already: a Coleman dual burner propane stove, an Iwatani butane portable burner, and a Jetboil. I carry three different kinds of fuel.

The induction cooktop is 200w-1800w depending on the power settings, which go 1-10. I set up my Lithium battery, connected it to the inverter, plugged in the cooktop and set up a pot of boiling water. The default starting power setting is 5 (~900w). 1200w is 100 amps at 12v, and the battery BMS can handle a 120amp discharge. Battery is 100ah, so it should run for an hour pulling 100 amps (1200w).

I ran the entire setup for 1hr and 3min, give or take. I ran it at level 8 for approximately 20 minutes, then turned it down to level 6 for the remainder. I use an induction cooktop in our kitchen and I rarely go over level 7, unless I want to boil a huge pot of water (of course the wattages are different).

I doubt we'd cook with the burner for longer than 20 minutes preparing our usual camp meal. Pancakes, eggs, and bacon on Sundays might run it a bit longer than that. Past use has shown about 10ah use running the fridge from sunset to sunrise. We've been fully recharged to 100ah by the time we finish breakfast. I think we'd be good for a couple days, but I might have to break down and get a DC-DC charger. At some point, I'll build a bigger battery, maybe a 280ah.

Honestly, I didn't really think this would work, but we're going to try it out next weekend on a multi-day trip.

 

[Otter]

Decided to mount a battery monitor to give me an idea (without having to look at my phone) of the charge percentage on the battery. This battery monitor uses a shunt to measure the amps going into and out of the battery and gives a pretty accurate capacity level. It can show the current voltage, amps, amp hours, and percentage, as well as showing charge or discharge. Pretty easy install and only $45 on Amazon. Victron makes a nice bluetooth smart shunt, but that's $160 or so.

 

[LongDuck]

Your flux-capacitor is showing...

 

[Otter]

Field tested for breakfast in Jackson, Wyoming. It will cook a couple eggs just fine for a breakfast burrito. Only used about 5 amp hours.

 

[Otter]

Prior to a two week trip to the Grand Tetons and Yellowstone, I added a Victron Orion Smart 18amp DC-DC charger. We usually drive every day, so this should top up my battery just fine.

 

[Otter]

Fridge and lithium battery fit in the small bear boxes at Curry Village in Yosemite. Should run the rest of the week with the cool temps.

 

[Funner]

Prior to a two week trip to the Grand Tetons and Yellowstone, I added a Victron Orion Smart 18amp DC-DC charger. We usually drive every day, so this should top up my battery just fine.

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What is the lowest you’ve run this down? It seems with the usable power in a 50ah LifePO4 that would be sufficient? I know everyone likes overkill, but my use would just be a fridge, no induction cooking, that’s stays in my house.

 

[Otter]

What is the lowest you’ve run this down? It seems with the usable power in a 50ah LifePO4 that would be sufficient? I know everyone likes overkill, but my use would just be a fridge, no induction cooking, that’s stays in my house.

On this trip, after 4 days in the bear box, I was down to 40ah or so. Pretty sure I've had it down to 25ah on a trip before. When I first built it, I ran it all the way to 0ah once or twice to test the capacity.

I usually account for 10ah running the fridge overnight while on a trip. That's from shutting the truck off after driving all day until the sun hits the panel in the morning. Inside a house at room temps for all day with no charging, you could probably average 20-25ah for the day, plus or minus. 50ah battery might be good for 2 days?