MillerTech LiFePO4 Batteries

[tfrohn]

Does anybody have any experience with MillerTech Batteries? They have a 48V 300 Ah LiFePO4 battery with BMS for $7,990. You would have to get twelve 24V Battle Borns for $12,000 at current sale prices to equal that storage. Any insights will be very helpful. Thanks.

MillerTech 300Ah 48V PREMIUM Lithium Iron Phosphate (LiFePO4) Smart Ba

**This product is a low stock item and may be back ordered. Please contact us ahead of time at ldsreliance@gmail.com to verify stock. It does not ship free and must be shipped via freight so give us your address for a price quote** MillerTech lithium batteries are lightweight, non-toxic, and...

ldsreliance.myshopify.com

 

[b.james]

40 days lead time sounds like they order them from china . You just tell them what name you want on them .

 

[ldsreliance]

@tfrohn We don't keep those batteries in stock in the warehouse. We order them on demand and piggyback them on other shipments with restocking of other batteries. That is why it says 40 days lead time because it literally comes on a boat from China.

@b.james The supplier that MillerTech works with in China does not OEM this battery design to any other company. The design of the BMS, the system parameters, the construction of the cell packs, and even the LCD meter built in to the case are all the design of MillerTech. In other words, this is not just a generic battery that they order off Alibaba and then slap a sticker with their logo on it.

 

[Kish]

I'm not affiliated with LSDreliance (Jason) / MillerTech in any way. I'm just a happy customer!

I've bought MillerTech batteries from Jason multiple times and it was a smooth process each time. Jason is highly technical and can answer any technical question about the batteries, and if he doesn't know, he'll ask MillerTech directly and circle back with you. MillerTech themselves are customer-centric and will go above and beyond to make sure you are 100% happy.

My setup is 4x 12.8 (12V), 100Ah LifePO4 batteries ("premium batteries" as they're calling now), wired in 2S2P for 25.6V (24V), 200Ah for a total of 5.1 kWh:





The batteries themselves are of high quality, and the capacity holds up as advertised. When I first installed the batteries, I performed a full 100%-0% capacity test at 1570W (61A so 0.31C, with 1C being 200A). The result was 219 Ah at 25.6V nominal, so that's more than the 200 Ah advertised.




Just yesterday, I performed another 0.31C capacity test from 100% to 5%, and got 207.7 Ah. Extrapolating the data, that's 207.7 Ah / 95% = 218 Ah, so still over the 200Ah advertised.

Over the last 6 months, the battery system has been drawn roughly 10,680 Ah, or 280 kWh, plus another 280 kWh put back into it via daily solar charging, for a total of 560 kWh. So you can say that they've been cycled roughly 560 kWh/10.2 kWh = 55 times. (or equivalently 280 kWh / 5.1 kWh = 55 times if you only count the energy discharged). According to my battery monitor, it has 74 Synchronization counts, meaning charged to 100% 74 times. Typically, my daily solar yield is enough to charge the battery to 100% daily, but there are certain days where I use more than the solar yield. So I'd say 75%+ of the time, it's charged to 100%.

If I can say one negative thing about the batteries, it's about the inaccurate SoC % meter on them. The voltage reading is accurate, but I personally can't trust the SoC % displayed on it. Under heavy load, the SoC % displayed is lower than the actual SoC, and under low/no load, the SoC % displayed is higher than the actual SoC. It's not a huge deal for me as I use an external battery monitor to accurately count Ah/Wh going in/out of the batteries, but just something to think about if you solely rely on that meter.

Yes, these batteries more expensive that your typical $400-600 / 100Ah you get from China, but the cells on these packs are top notch! If you want to pay a bit less and don't mind lower quality cells, looks like MillerTech is now selling grade-B packs for a slightly lower price. However, I can't say anything about those since I haven't personally tested them, but the regular premium ones (gray case) is recommended by me. If anyone is interested in all the technical data, let me know and I can post it somewhere. I'll try to post more updates as the batteries are cycled and age in the coming years.

 

[ldsreliance]

@Kish Thanks for the feedback and support! I am glad you are satisfied with the batteries.

 

[dmholmes]

If you want to pay a bit less and don't mind lower quality cells, looks like MillerTech is now selling grade-B packs for a slightly lower price. However, I can't say anything about those since I haven't personally tested them, but the regular premium ones (gray case) is recommended by me.

Looks like a good value, I ordered one yesterday

 

[More_Solar_Power]

Looks pretty good for the money. Note that it is limited to 0.5C max discharge.

 

[Kish]

That's not true. You can discharge at 1C (100A on the 100Ah battery).

• Charge/discharge current: 100A
• Peak discharge current: 300A for 5 seconds

 

[ldsreliance]

Looks pretty good for the money. Note that it is limited to 0.5C max discharge.

Where did you hear that??

 

[More_Solar_Power]

From the specs on the link OP posted:

300Ah 48V LiFePO4 Deep Cycle Smart Battery Specifications:

• Efficiency: 98%
• Max charge voltage: 58.4V
• Cut off voltage: 42V
• Max charge/discharge current: 150A

 

[Kish]

Ah, yes. I think anything larger, starting from their 200Ah, 12.8V battery has a 150A cap. I believe that due to the BMS they use?
However the peak of 450A for 5 seconds should be plenty for most use cases.

If you're drawing more than 150A continuously from a single battery, you really should consider paralleling multiple instead and cutting the current in half. A single battery of 150A @ 51.2V is 7.6kW continuous, which is quite a lot of power for residential uses. Should be "good enough" unless you're running your central AC, using your electric oven, and charging your EV at the same time.

 

[ldsreliance]

Ahh yes. That battery is very different from most everything else in their lineup. Not a big seller as there really isn't much demand for that large of a single battery. Kish is right... most anyone would wire in parallel at that point so why design a heavy duty (expensive) BMS just for that use case?

 

[More_Solar_Power]

Do we know if they are using cylindrical or prismatic batteries?

 

[Kish]

I haven't opened mine, but here is a screenshot from LDSreliance's intro video on MillerTech:

 

[ldsreliance]

Do we know if they are using cylindrical or prismatic batteries?

Cylindrical. All cells are graded and then matched before assembly. They grading process is pretty thorough... much more vigorous than the processes some other folks are using. None of the electrical connection points are structural. All cells are fully supported.

Good questions, keep them coming.

 

[More_Solar_Power]

I can tell I'm in the wrong forum for this next comment so please take it as personal preference and not an indictment of the DIY movement. From and engineering standpoint I much prefer a one-box solution. So when you say 'most people would parallel..." it might apply to most but not all. I suspect as DIY solar expands to larger and larger systems, the desire for one-box solutions of increasing power is more than likely.

From a business perspective I can see how Mr. Miller might resist creating a special BMS for >150A in his case until the market develops.

I'm a DIY'er AND a working EE. I once was in the build-it-from-scratch mode. Maybe it's my age but I'm in the reliability mode now. One box has far fewer hand-made connections. It's also tested as one box. In this particular case I would be looking at Mr. Miller's 300 Ah solution.

 

[ldsreliance]

Oh, I fully agree with you. I'd rather have one battery myself than multiple individual batteries wired as a bank. I wish there was more of a market for them. Maybe as utilities continue to come on board with power storage there will be more need for larger single batteries.

 

[Kish]

No worries, I don't think anyone here is offended with you wanting a single high-drain battery, for simplicity.

But just to keep things in perspective, the Tesla Powerwall 2, which is also a huge battery (13 kWh) for whole-house backup, has a max continous discharge of 5 kW, so assuming it's 48V, that's only just over 100A. Even Tesla themselves recommend getting at least 2 Powerwall 2's to put in parallel, for a total continuous discharge of 10kW.

The other thing to keep in mind is the size and weight of these battery packs. For 200A+, you'd need to use massive 0/1 - 0/2 cables inside, adding even more to cost and weight. The BMS PCB itself would need to have massive traces to handle the current. I (personally) rather have multiple batteries in movable chunks. In case I need to move battery locations, or move houses, it's easier to move a 30 lb battery than a 450+ lb behemoth. Imagine RMA'ing a 450 lb battery back, yikes!

 

[Kish]

Its now been exactly 1 year since I've installed my MillerTech batteries, and they've been working without any issues. (As a reminder, my setup is 4x 12.8V (12V), 100Ah LifePO4 batteries ("premium batteries"), wired in 2S2P for 25.6V (24V), 200Ah for a total of 5.1 kWh). Currently I'm at 521 kWh discharged 531 kWh charged on it, for a total of 1.05 MWh of cycling. Alternatively, that's 19,800 Ah cumulative Ah drawn.



Today, I performed another 0.31C (1570W) capacity test from 100% to 0%, and got 203.2 Ah. When brand new, in the same capacity test I got 219 Ah. So the capacity is definitely dropping, but I'm still getting more than the 200Ah advertised. This may be normal for new LiFePO4 batteries, so I'll be monitoring it going forward. Maybe I'll do a capacity test every 6 months or so and post the results.

 

[ldsreliance]

Awesome stuff, Kishan! Glad to see they are performing well for you.