DIY LiFePO4 build
so this started because I gave away my first DIY build (280amp) to a good friend, because I also wanted to upgrade the 5th wheel but standardize the batteries between the 5th and truck camper so I ca...
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there still is some cost savings depending on how your order stuff. for example, due to tariffs and such for you to get the cells int he US right now you are looking at 95 bucks per cell with free shipping I believe, they have gone up an average of 25US a cell in the last few months. they were cheaper before the tariff crap started happening.
If you live in Canada and don't mind waiting for the slow boat to deliver them, or know some one in Canada who can order them for you and then you go visit and build your battery..... I think they can be had for about 65.00 bucks now, would have to check on the price with the supplier. so at 65/cell that is 260 bucks, you can get a 200amp BMS for about 80 bucks CDN so now we are up to say 320US. you need a fuse, some cables, so say 300 US all in. I haven't found the elusive 100US 100ah battery most seam to be right around that 200 buck range, but look at 300ah "mini" batteries and see what they are.. I say mini because that's the size that's the same as mine, the other 300AH were made of a bunch of 100AH or 150AH cells in series/parallel so they took up more room. the new mini's you see are using 304Ah cells so they are the same size as mine. and the good thing about the mini form factor is you can put two of them in almost every camper out there as they are group 27 size I believe.
so the watt cycle 280Ah mini with Bluetooth is 730.00 the regular price on the renogy 300 mini is on sale for 799, regular 899. so there still is some savings. now one thing to note, the cheep batteries have no real compression, they are just shoved in the battery box with some Capton tape or a fixture holding them in place. so ya as long as your charge and discharge rates are modest it won't make a huge difference, but if your approaching that 0.5C rate in charging or discharging, which isn't hard with a 100Ah battery then compression becomes more important for getting full battery life.
now at the prices I paid for my cells because I got them so long ago, and I got a good deal as we ordered 32 cells. so I built 4 batteries for other people before I even started on mine but theirs were just to the Kapton tape usable stage, they had to come up with their own case. I am probably more expensive than buying a new 300AH mini, but I know which cells I am using, but we are comparing prices two years ago to prices now. two years ago a 300ah premade was over 2000.00 bucks.
another example about 4 months ago a 100ah cell was 35 bucks in the US (from the expensive stores) and 20 bucks on the slow boat from China. today they are 60 bucks so tariffs have brought back pricing from 2 to 3 years ago. so you could build a 100ah battery for 120 bucks 4 months ago, now its going to cost you at least 300. so the larger you build right now the more your going to save as the price of premade is being affected also.
I take the $100 back...they sort of exist but when I went to pull the trigger, they wanted $30 shipping per battery...still pretty cheap but doesn't take Canadian pricing into account.
But I'm not looking for a 900amp-hr bank, so space savings may be a much bigger deal for you. My only major 12v draw is the fridge and I'm borderline getting by with a single 100amp-hr lead acid, so a couple of 100amp-hr lithium is almost overkill for my needs.
I take the $100 back...they sort of exist but when I went to pull the trigger, they wanted $30 shipping per battery...still pretty cheap but doesn't take Canadian pricing into account.
ya I have seen some for 100US but they seam to come an go and are usually listed as a sale price for some brand I have never heard of. I don't doubt they can make them that cheep. If I can get a 100AH cell for 35 bucks with a small order, I would guess a Chinese manufacture is paying as low as 10 to 15 per cell on a large order. and a no name generic BMS is probably 5 - 10 bucks. so really they are paying say 50ish bucks plus another 15 for the cheep case so 65ish plus say 10 bucks for the labour on that battery, if its even that much. that would be right for a 120 - 130 buck battery retail, so a sale price of 100 is totally reasonable.
ya, and just a single 100amp will be much better than what you have as it is generally twice the usable amperage.
I didn't put 300AH in my camper because that's what I needed to get buy, I could easily camp the way I camp in the truck camper with a 50AH battery and the solar I have. where that would be an issue is if the solar broke, or I ran into more than 1 cloudy day. so when I size my batteries I pick the 24hour usage and multiply it by how many days I would normally stay out on a bigger trip. so with the truck camper I use an average of 38AH in a 24 hour period running the furnace all day when night time temps are down at freezing or just below. so with a 304AH battery I can camp 8 days before I I have to worry about anything and then I can always run the dc to dc charger for a couple hours as an emergence back up.
I kind of do the same thing with solar, I size it with the intention of it replacing everything I used overnight by noon. that way I am 100% when the sun goes down and at 100% around noon again. this allows me to make up for bad day easily so if I have a stretch of 3 bad days where I don't recover my usage because its raining and very overcast, so I am down say 100AH when it finally gets sunny, I should be able to recover that in one day and be at 100% for bed time again.
I kind of applied the same logic to the 5th wheel except my average usage is just under 100AH per day in the same conditions. it does have a few differences that throw a curve into my set up, it has been working fine for how we have been using it with 480 watts of solar and four 6V batteries but I wanted to start running the outdoor kitchen refrigerator on the inverter while I am camping. that second fridge for all your drinks is just to convenient to not use but with the setup I have had on it I lose about 20% of my battery capacity a day. now that was in 120F temps so I probably would only use 10 to 15% a day in normal temps. so this issue is prompting a solar upgrade from the 480 watts to about 975 to 1200 watts depending on which panels I find. and then the Lithium batteries for it. the thought of Lifepo4 for the 5th wheel was to make it so I could hit that 8 day or more mark with out the solar working but in reality its more weight savings and constant power for the inverter. plus it will let me run that bar fridge, My GMG smoker and say the icemaker and Margaritaville or the ninja frozen drink maker 😉
