DIY 280Ah LiFePO upgrade for my Lance 815...

[LivinDaDream]

This will be a bit long, but perhaps helpful to someone considering the same sort of battery build.

I've had a Battleborn 100AH battery in my camper for about 3.5 years and couldn't be happier with it...it just works. My power needs are modest...compressor based fridge being the biggest draw and second is my laptop if I'm doing photo or video editing. I have all LED lighting, so that is pretty minimal. I'm good for about 3-4 days of heavy overcast before running low on power and can run the truck or a small generator to recharge if need be. Needless to say, more battery would be a good thing, but given my space constraint of a single battery box, adding another battery would require some sort of kluged up system external to the camper itself. I looked at putting a couple 50AH Lithium units on either side of the camper in the space between the camper base and the sidewall of the bed, forward of the wheel humps, but that requires wiring and installation and removal when loading or unloading the camper.

For a while I've been thinking about building a 280AH DIY battery pack using some of the cells and parts available direct from China on AliExpress, but hadn't yet pulled the trigger on ordering the parts. Well, a couple weeks ago as I was browsing the local CraigsList, I ran across a guy selling the parts he bought to build exactly what I had in mind, as well as some other odds and ends that he had ordered as well...4 ea. 280AH 3.2V cells, 150A 12V 4S BMS w/Bluetooth and PC interface, 25' 6GA paired cable, a bunch of lugs, a 150W battery load tester, Battery monitor w/500A shunt, heavy lug crimper (hammer driven)...all for $500. He hadn't even opened most of the items, only one of the cells. He and his girlfriend had been planning on going full-time in a camper, but he got a job opportunity that he couldn't pass up and that idea was out the window, so he decided to sell all the parts he'd just bought. I checked the cells out carefully and all were very closely matched in terms of SOC as shipped and had the barcodes intact.

When I got the items home, I set about prepping and testing the cells...discharging them down to 2.55V/cell and then full charge up to 3.55V/cell wired in series and finally up to 3.65V/cell with all 4 cells bussed together in parallel...leaving them bussed together for a day to equalize amongst themselves. I did all the charging with a 30V, 10A lab power supply and double checked cell voltages with a known accurate VOM. Next I configured the pack in series again, added and configured the BMS and did a capacity test on the completed bank. Measured capacity was 284AH to the 2.5V/cell cutoff point when one of the cells reached that voltage...color me impressed! My plan is to run below the max capacity and operate in the 10% to 90% range or around 224Ah or 2900Wh, so better than double what I have with my BB 100Ah. Which, by the way, I just tested and after almost 4 years is still delivering 103AH from full charge to cutoff...I have plans for it, too!

Next, step...how to configure the cells and BMS to fit in the battery compartment in the camper. Most builds I've seen of these type cells have them arrange 4 in a row and while that would have fit in the space, I would have to mount the BMS on the top of the battery and there wasn't as much vertical clearance as I'd like and that would make accessing the cell terminals difficult with the BMS mounted above them. If I configured the cells in a 2x2 layout, I still had enough opening width to squeak in the opening and enough front to back space to mount the BMS on the side of the cells with plenty of space for the door to close...and plenty of top clearance now.



I considered several ideas on how to physically package the cells and one of the challenges was that going with the 2x2 layout was that I was left with only about 1/2" clearance between the cells and the inside opening width of the door. Whatever I did to secure them to each other couldn't exceed 3/8". So, I got some 1" x 1/16" aluminum angle and welded up an open bottom tray to secure them at the bottom...a snug fit once I installed wrapped the base of the cells with captan tape as an added protection beyond the plastic wrap on the aluminum cell bodies. I'll check this at some point for any signs of wear. I made my own buss bars out of 3/4" x 1/8" Aluminum bar stock and mounted an 1/8" plexiglas top cover on standoffs above all the terminal connections. As you can see from the photos the bolts for the cells on each end are exposed and there is voltage potential between one end and the other, though not between the bolts on each end...something I'll deal with shortly.



The BMS and a Thornwave Bluetooth power monitor are mounted on another piece of 1/8" plexi that is attached to the side of the cells with 6 squares of hook/hook velcro. The BMS is mounted on 1/4" standoffs to allow air circulation behind it. Likely not needed as the power levels I'm be running in my system rarely get above a 20A load or a 35A charge rate, either from Solar, Camper Battery Charger or the truck alternator. Connection from the battery to the house 12V system is via Anderson PowerPole connectors with 75A contacts.

I threw all this together more quickly than I'd expected and hadn't planned to have it all together before taking off to Norris Lake in TN for a few days, but I was able to get the basic package together and installed in time, so was a perfect opportunity to see how it worked. I do need to add a few things, one being small buss bars to attach a couple Anderson PP75 pigtails for external loads or my other MPPT controller and remote panels. Overall, the system is performing as expected and I've got my solar controller and the BMS all set up to keep the system operating within the limits I established (10%-90%). Key is being able to set custom parameters for both the solar controller and the BMS so that both can do their job properly. With the system at rest, not charging and with minimal load, I'm seeing cell balance within 3mv and while charging near full capacity, cell balance is generally within 50mv...which in my understanding is pretty darn good.

I hope someone finds this useful and I'll be glad to answer any questions...

Cheers!

 

[DiploStrat]

Bravo! Very nice work. I did the same thing, but I didn't get THAT deal! You are absolutely right - the carpentry of getting things into an existing space is the hardest part. In my case, I was replacing four 6vx300Ah AGM batteries. I, too, had to go with a side by side layout.

Yours is prettier than mine! And I REALLY like your plexiglass safety shields! My three BMS attach to the backside of the white bridge over the cells. The whole mess is in a dinette bench.

N.B. I dumped the bus bars for 4 AWG jumpers. I now balance at about x.004v between cells. Also, on the advice of others who went before me, replaced the screws with stainless steel studs.

 

[LivinDaDream]

Thanks, I'm more thankful for not having to wait several months for the parts to ship by slow boat from China, but a good deal was icing on the cake.

I wish I had a space like that to put two or three packs like you did, I'd consider changing my system over to 24V and putting in a big enough inverter to run my AC for an few minutes to cool the rig down before bedtime. Rare that I boondock in an area where AC will be required and if I do, I have a portable generator that I'll take with me for such occasions.

Great use of space and I see you did the 2x2 layout as well. Why did you ditch the bus bars for the jumpers...less stress on the terminals? Were those 1/2" x 1/8"?

 

[DiploStrat]

Don't mention 24v! (Long, sad story. My Mercedes truck is 24v. When the camper was built, they did a terrible, and expensive kluge to get 12v, so they could use the inverter/chargers and solar controllers that they had in stock. Doing it over, I would have simply replaced the inverter charger with a 24v unit, done the same for the solar controller, and then gotten a simple step down converter to get 12v for my 12v loads. Would have been money ahead in the long run! We get too soon old and too late smart!) At this point, I have killed all of the dragons, but I could have done it a lot more cleanly!

The whole point of the 800+Ah battery bank is to run the air conditioner at least 12 hours. Haven't tested that yet.

I started with the steel, Chinese bus bars, mixed with aluminum. I had some balance issues, but, to be fair, I finally traced them back to a bad crimp on one sense lead and the fact that I had no load on the batteries. All of that said, copper is good and everything is wired for 200A per battery. My actual total load (microwave) is only around 150A, so I should have good reserves.

In your case, I wouldn't worry until I saw problems. Probably worth checking for corrosion once a season, or so.

Again, really nice work!

 

[LivinDaDream]

Not much worse than going back and having to clean up someone else's mess...I feel your pain.

If I ever get around to moving to a bigger rig, whether a camper or an RV and I have the space, I'll definitely go 24V or even 48V for solar and inverter/charger. A converter to get whatever voltage you decide on down to 12V for the minimal 12V loads is chump change and makes the core system so much more efficient at every level...not to mention not having to deal with massive conductors, etc when you start pulling 200A or more loads on a 12V system...it's crazy! If this battery works out well, I might order parts for 4 more and build a 24V or 48V pack to install on the modified trailer I pull on longer trips. It's set up for one or two motorcycles, bikes, kayaks, tools and extra fuel, water, propane and extra gear that I might want with me. I've got two brand new 300W panels I picked up for $150 each that I could mount on the trailer to charge the bank...power an inverter and plug the camper into it, though I'd probably want to disable the Truck Camper charger when plugged into the trailer inverter. I'd be curious to hear how your AC use works out...what type are you going to be powering? I've got a 9200 btu Coleman Mach-8 Cub low-profile unit...cools the camper down pronto, but it's noisy, as you would expect.

When I installed the buss bars and connectors to the cells, I used some Noalox anti-oxidant compound to minimize corrosion...good stuff if you're using AL/AL or AL/CU connections. Brushed the cell post surfaces and the mating surfaces of the buss bars before putting it all together. Funny, I had the same issue with a bad crimp on one of the BMS sense leads...had me scratching my head for a few minutes.

 

[DiploStrat]

THANK YOU! I was looking for Noalox, but could not remember the name. I knew I did not want dielectric grease.

We have a Kalori 12v A/C in the camper and another, 24v model, in the cab. Not really recommended - leaks, no thermostat, expensive to service. Had to move the inverter outside the camper because of heat when running on shore power.

There are better options, but frankly, with lithium, it may be hard to beat a mini-split (first choice) or a small RV A/C with a soft start. These both have the advantage of not needing the inverter/charger when on shore power, and let's face it, if it is really that hot, you are pobably looking for a commercial camp site.

FWIW, the magical numbers are something like: 50-60A with compressor on and 75A of solar. With 75A of solar (about 1500w of panels), you can run A/C all day in good sun, e.g. west of the Mississippi. (See Everlanders for a really slick, double layer panel set up.)

 

[Rando]

One thing you really need to be a bit more careful about with both theses installations in a high vibration environment is insulating between the cells. With many or most of the aluminium cased LiFePO4 cells, the aluminium case is also the anode. As a result, the only thing preventing you from shorting out the entire battery bank is the either one or two layers of the blue heat shrink plastic. If you were to get some grit between the cells, and then give them a good shake, there is a pretty good chance of wearing through the heat-shrink plastic, which would cause an unprotected dead short across a cell, which would get really hot, and cause the heat shrink to further shrink. The battery has no protection against this so a fire would be a real possibility.

I would strongly suggest placing some sort of insulating buffer between the cells - a thin (1 - 3mm) thick sheet of HDPE or something like that would do. The batteries sitting in the aluminium tray give me the serious heabie-jeabies. I know you added some kapton, but I really think you need to reconsider this.

Edit to add - to be clear, I think DIY LiFePO4 is a great option and have been using them for almost a decade now. However the impetus is on the builder to consider what the possible failure modes are and guard against them.

 

[LivinDaDream]

Rando,

I was way ahead of you on this, though I didn't mention it in my post. I had some .8mm hard, but bendable plastic material (might be HDPE, no way of knowing) that had been part of an older photo backpack to stiffen the sides of the bag. I inserted strips of this material between the cells and on the bottom between the aluminum angle and the base of the batteries. I did not have enough to also do along the bottom sides of the batteries, so that is where I used the Kapton, as well at the bottom. It's very easy to unplug the connectors and slide the battery out for inspection, which I'll do before my next trip. I'm not concerned about where the cells come together in the middle, either side to side or front to back so much as the base as that's where all the weight is concentrated. I was thinking of welding in a 2" wide cross piece in the center, front to back to support the central crosspoint of the batteries, but my impending trip didn't allow time for that. Right now, only the perimeter exists, it's just an open frame. The trick may be finding a 2" wide piece of 1/16" aluminum. May have to buy a small sheet and cut it.

Appreciate your thoughts on this...good points.

 

[RAM5500 CAMPERTHING]

I am in the early stages of planning to possibly build a large DIY lithium bank and found this on my search.

Great info

I have a single 300ah battery now and it will run the AC nicely for a couple hours to cool down the box, but it limits me to doing much else.

 

[DiploStrat]

For anyone old enough to remember the Firesign Theater: "Everything you know is wrong!"

The thinks you can think!

-- Lead acid needs to be over charged to prevent sulfating - overcharging destroys lithium.
-- Lead acid wants to be kept on float, fully charged, and prefers shallow discharges - lithium should not be floated, not kept fully charged, and needs deep discharges to avoid memory.
-- Voltage is a strong indicator of the status of a lead acid battery - lithium sits at 3.2v all day. Most chargers read voltage, not amps. A lithium charger needs to read amps because you can overcharge a lithium battery at low voltages.

Sooooo, with lithium you want the smallest bank you can get away with so as to exercise it often.

BUT: If you want A/C or really extended stays in the rain, you want a bigger bank than you need most of the time.

Having gone from 600Ah of AGM to 840Ah of lithium, I am still sorting this out. But I will offer two comments:

-- 90% of the gear out there is really optimized for lead acid. As the chargers are controlled by the voltages they read, not the amps they pass, changing the voltages only helps a little.
-- Your BMS is your friend. Don't scrimp. You want a VERY adjustable, ideally self resetting model.

Finally, there is a reason that Battle Born offers a 10 year warranty and there is a reason that one of the early DIY lithium gurus just bought Battle Born after their home brew finally died after 8.5 years. Yup, they did it well enough to last over 8 years and decided to go with a commercial battery the second time around.

Offered with best wishes as I continue to monitor EVERYTHING!

This ain't for the faint of heart!

 

[Rando]

This is the first I have heard of concern of a "Memory Effect' for LiFePO4. On some further reading it does appear that LiFePO4 does have a small 'memory effect' but this is primarily related to a voltage bump in the discharge curve not a reduction in capacity:
Toyota LiFePO4 Memory Effect Research
The conclusion is that this bump in the discharge curve could confuse algorithms trying to determine SOC from voltage. But I think we all agree that you really need a coulomb counter to determine SOC, so I am not sure this matters for our use.

As a practical example - I have been using a 150Ah DIY LiFePO4 pack in my FWC for the past 5 years. During the spring and summer I just leave the camper on with the solar active. As a result the fridge etc, use about 15Ah every night - or about 10% of the battery capacity. Over the past 5 years this is about 6-800 shallow cycles. Every year or so, I put the pack on my battery analyzer, and the degradation of capacity over this time is completely consistent with calendar aging (~7% over 5 years), so I don't think there is any evidence of this reducing capacity. Besides the test cycles, I don't think I have ever taken the batteries below 60% DOD.

This also brings up another interesting point - unless you are a 'full timer' that cycles their batteries deeply every day or egregiously abuse the batteries, with LiFePO4 calendar aging will probably get you before cycle aging is a problem. Assuming 'heavy' use of 100 days of active use a year, you would still get almost 20 years of use at 100% DOD, in which case the batteries will age out first - or more realistically you will have moved on to another camper. The take home from this is that it is not really that important to focus on things like keeping your cycle between 10 - 90% SOC, memory effects etc. Go out and use your batteries and enjoy them!

 

[DiploStrat]

This is the first I have heard of concern of a "Memory Effect' for LiFePO4. On some further reading it does appear that LiFePO4 does have a small 'memory effect' but this is primarily related to a voltage bump in the discharge curve not a reduction in capacity:
Toyota LiFePO4 Memory Effect Research
The conclusion is that this bump in the discharge curve could confuse algorithms trying to determine SOC from voltage. But I think we all agree that you really need a coulomb counter to determine SOC, so I am not sure this matters for our use.

As a practical example - I have been using a 150Ah DIY LiFePO4 pack in my FWC for the past 5 years. During the spring and summer I just leave the camper on with the solar active. As a result the fridge etc, use about 15Ah every night - or about 10% of the battery capacity. Over the past 5 years this is about 6-800 shallow cycles. Every year or so, I put the pack on my battery analyzer, and the degradation of capacity over this time is completely consistent with calendar aging (~7% over 5 years), so I don't think there is any evidence of this reducing capacity. Besides the test cycles, I don't think I have ever taken the batteries below 60% DOD.

This also brings up another interesting point - unless you are a 'full timer' that cycles their batteries deeply every day or egregiously abuse the batteries, with LiFePO4 calendar aging will probably get you before cycle aging is a problem. Assuming 'heavy' use of 100 days of active use a year, you would still get almost 20 years of use at 100% DOD, in which case the batteries will age out first - or more realistically you will have moved on to another camper. The take home from this is that it is not really that important to focus on things like keeping your cycle between 10 - 90% SOC, memory effects etc. Go out and use your batteries and enjoy them!

Interesting and useful info.

A lot of the sources for info in this field a marine focussed and tend to do a lot of viewing-with-alarm. My "problem" is that with over 600w of solar, I am having trouble getting my bank to discharge - at all. Battery balance improved no end once the refrigerator was turned on. Clearly, some load was necessary.

Many thanks!

 

[LivinDaDream]

Diplo and Rando,

Great points and very much in line with my own thinking/experience. In plotting out the knees in the charge-discharge curves for the DIY set I built, I've setup my BMS to operate between those two points. Actually, I've worked out settings for two different modes. In most cases, I don't need to use the full capacity of my cells, especially when the camper is parked between trips with just parasitic loads and the refrig, typically same as Rando, about 15Ah overnight. so I set my BMS and SCC to operate the system in a lower capacity mode with a low-voltage disconnect of 12.5V and a charging voltage disconnect of 13.5V. If I'm going to be in a situation where I might need closer to full capacity, I'll adjust my charging voltage disconnect to 14.2V. Only takes a minute to plug the new values into my BMS and SCC. No matter what my overall settings might be, I've got individual cell protect values set to protect against any individual cells getting above 3.65V or below 2.5V. So far, my balance is very good.

All that being said, the reality is that, as Rando said, this battery pack will last far longer than my need in this camper...in fact, I'd really have been ok to stick with the Battleborn. This build was an economical and convenient opportunity to dig deeper into a DIY system and a practical means to build an off-grid power system for a small house I may build on some property I own.

I continue to be impressed with the way Battleborn has chosen to engineer their battery systems and set their operating parameters. I don't think anyone else has done as good a job in engineering an install it and forget it package. Many of the "alarmist", types will rail against not being able to control the internal BMS or know what's going on behind the curtain, but we all know too well what happens when you give people "knobs" to play with AND a long warranty! For the first two years of the time I used mine, it was connected to a charger in the camper that didn't have a lithium setting, nor did the MPPT controller have one...I just used the GEL setting on the MPPT since it didn't have an Equalization mode. My current MPPT does have a Lithium setting, but if I'm on shore power, the internal charger is still the original one...no problems whatsoever although don't believe it will charge at a high enough voltage to get a Lithium battery to 100% SOC...only around 80%. Once the sun comes up the Solar will take it the rest of the way, though. I don't really know how anyone could "kill" one of the BB units, other than extreme high temps or physical abuse...they don't seem to have cut any corners.

There is a substantial customer base that is willing to spend the money and be able to go on with life without worrying about the minutae of battery charging/discharging. They've built a reputation that makes them the goto for that market! Not a bad plan!

 

[Rando]

Another interesting issue that I think has been misunderstood is the voltage needed to get a LiFePO4 up to 100% SOC (or very close to it). Any voltage at or above 13.6V will (eventually) get your battery to essentially 100% SOC. It may take a little longer as the current will be lower, but it will get there. So unless your charger has a really low output voltage, I am sure it will get it to 100% SOC with some time.

 

[LivinDaDream]

That's true, at least for practical purposes and the amount of extra energy you put in a LiFePO4 3.2V nominal cell in a 4S pack is only about 1% when you charge above about 13.6V to 14.6V vmax (3.65V/cell). So not worth the time and effort to get there. I do see a lot of comments from those that worry about not getting to 100%...Lithium doesn't care if you ever get there, really...just reduces your available energy, but doesn't damage the battery.

Even then, your BMS is going to shut down charging as soon as the first cell hits whatever your individual cell cutoff happens to be. In my case, I usually have the individual cell cutoff set for 3.55V max and I'll see a cell balance delta of maybe .080V when charging at a fairly high rate 20A+) and nearing 99%. At lower charge rates and SOC, its usually below .020V while charging and .003V or less at rest.