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Battery bank replacement: drop-in LiFePo vs diy

adkroot

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My current bank composed of 8 Trojan L16RE fla batteries is due for replacement, and other than the financial savings I'm curious what the differences, pros, cons, etc., are for a diy LiFePo4 set vs a drop in replacement. Specifically, I'm looking at RELiON's batteries as far as a drop-in replacement. Are they able to access higher quality cells?
Thanks
 
I'm in the beginning stages of the same project. Replacing 24v 420ah lead acid with 24v 8s 280ah lithium DIY.

Rough figures: $1200 cells, $125 BMS and maybe $120 for a VERY nice box. Can't come close to that with any drop in. Closest reputable drop in that I found was the CHINS or Ampere time 200AH at just under $2k and NO cold charge protect.
 
8 Trojan L16RE fla batteries is due for replacement
How did these perform for you, and how many years/cycles did you see from them? I've never seen any in person, but considered them when my GC2 were starting to struggle.


I'm curious what the differences, pros, cons, etc., are for a diy LiFePo4 set vs a drop in replacement

For banks of that size many here will recommend DIYing a big LiFePO4 bank as cost will be much lower and built to your precise spec. Drop-in is easier and has some kind of overall warranty, to the degree such a thing is enforceable and useful.

I always thought I would DIY LFP at some point (both cost and curiosity), but ended up buying a drop-in because of my travel logistics. I don't know where I'll be when the various cells, BMS, hardware, etc started coming in from the Slow Boat. With a drop-in I only had to be in one place on a known date to pick it up. And for the small amount of capacity I needed (100Ah) the cost difference was not egregious.
 
How did these perform for you, and how many years/cycles did you see from them? I've never seen any in person, but considered them when my GC2 were starting to struggle.




For banks of that size many here will recommend DIYing a big LiFePO4 bank as cost will be much lower and built to your precise spec. Drop-in is easier and has some kind of overall warranty, to the degree such a thing is enforceable and useful.

I always thought I would DIY LFP at some point (both cost and curiosity), but ended up buying a drop-in because of my travel logistics. I don't know where I'll be when the various cells, BMS, hardware, etc started coming in from the Slow Boat. With a drop-in I only had to be in one place on a known date to pick it up. And for the small amount of capacity I needed (100Ah) the cost difference was not egregious.
The Trojans lasted 10 years, and are still going though with a noticeably reduced capacity. Seems to be around 40% of what they were when new. They performed well- we're entirely off-grid here in upstate NY, and have a family of 4 so electric use is moderate (showers, internet, tv, washer, etc.) My house is relatively efficient with dc lighting, dc fridge, and until three years ago dc submersible, but I also am building a new home and use all my equipment - table saw, planer and jointer, etc. I've taken care of the Trojan set, keeping it watered, never letting it get below 60% charge, and charging to 100% whenever I need to charge with the generator, which is pretty often from November until March.
 
I've had 20 kWh of L16's for a while and wanted more storage, so this year I added 45 kWh of lithium batteries, DIY style. I've really enjoyed the new battery, for a couple of reasons that aren't spoken of often enough I thought I'd mention.

The first is charging speed. The lead acid cells get harder and harder to charge as they fill up, that last 10 percent goes slower and slower. The lithiums just take the full output of my chage controller right up to the point they're full. It's not uncommon for me to see 2-3x the power going into the lithium cells compared to the lead acid, from identical arrays. Here in the Pacific Northwest in the winter every minute of sunshine is valuable and it feels good knowing the batteries are sucking it up.

The second is just never having to worry about the status of the batteries. Are they getting near 50 percent? Have they made it to float recently? It doesn't matter. As long as there's power in them they're fine, no more need to worry about where they're at other than if they were to get low, which they haven't so far even in December in Oregon. That's most of a week's storage for me, and even this time of year we get enough light here and there to keep them chaged. My L16s have caused the inverter to charge them a couple of times in the last week.

My lithium batteries are 3 x 16 cell of 300 ah each, each battery is 24v at 600 ah more or less, and cost about $2500 buying from good reliable USA source of cells (Docan). Couldn't be happier with the upgrade.
 
My current bank composed of 8 Trojan L16RE fla batteries is due for replacement, and other than the financial savings I'm curious what the differences, pros, cons, etc., are for a diy LiFePo4 set vs a drop in replacement. Specifically, I'm looking at RELiON's batteries as far as a drop-in replacement. Are they able to access higher quality cells?
Thanks
Based on my own experience, I'd go the DIY route vs. the MUCH more expensive drop-in route. Not only do you get the hands-on experience of assembling your battery but you learn how everything interacts.

Watch as many videos as you can prior, read, and ask questions if something doesn't make sense. I did this for months prior to ordering my cells and BMS. Assembly of the battery and reprogramming of my charge controller and inverter/charger went seamlessly.

You will love your new lifepo4 battery!
 
Honestly, by far the hardest part of assembling a DIY until recently was finding quality cells at affordable prices. I put off going with lithium for a couple of years because I wasn't willing to send 1,000's of dollars to an overseas seller with no real recourse if I got junk or nothing, which was/is a common occurrence. Now that there are some reliable sellers operating with US stock and taking credit card payments it's a great way to go. There's a bit of a learning curve but it's really not complicated if you spend some time reading and studying first.
 
I am in the exact same boat right now and am going to go drop in because if I DIY and it doesnt hold up I wont hear the end of it.

Sounds like no one regrets switching to LiFePO4.
 
I am in the exact same boat right now and am going to go drop in because if I DIY and it doesnt hold up I wont hear the end of it.

Sounds like no one regrets switching to LiFePO4.
Funny you say that, my wife was just expressing her skepticism last night while I was touting the savings.
 
Funny you say that, my wife was just expressing her skepticism last night while I was touting the savings.

I was replacing the pelton wheel on our hydro turbine and had a bit of a mishap with the penstock tubing (WHICH I FIXED WITHIN A WEEK) and after that I have lost all credibility. She has a point though--It might a few thousand dollars savings but theres a certain price you pay for convenience, confidence in the "name brand" of the parts but also you just feel better when something fails and it aint your fault!
 
Watch Wills latest video. If it were me, I’d buy one of those EG4 Server Rack batteries. Has everything you need without the hassle.
 
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Well, pros, cons, etc., for a DIY LiFePo4 set vs a drop in seem pretty obvious, don't they?
DIY, save money, learn, have fun. Assume the risks.
Drop-in, have other things to do (some of which make me some money ;·), have someone else (the vendor) do the work, minimise risks.
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BTW...
Sounds like no one regrets switching to LiFePO4.

Well, I for one certainly don't. It's just superior chemistry.
It's one of those life's quirks that the man who made it possible was called John B. Goodenough, isn't it?
He was certainly good enough to win a Nobel (and a few other) prize. Chuck Berry would have loved him... and so do we all ;·)
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I went from 24V/428AH (22kWh gross) using 8X Rolls Surette S-550's to LFP.
1st Purchase was a Prebuilt Disaster with used EV cells a craptastic BMS and heaps of problems. (The ShunBin Disaster). In the end that became 24V/350-AH in the form of 2x 175AH "8S" packs with a proper BMS each.

Then I bought 8 Bulk EVE 280AH cells from Amy @ XUBA (No longer there and company no longer recommended due to lot of neg experience with company bt NOT Amy. Amy took over (OWNS) Luyuan Tech and now has one of the Best Reputations here.

I bought 8 Bulk EVE-280AH Cells from Amy @ Luyuan and they came out perfect but are clearly B/Bulk as they really diverge above 3.400Vpc.
I bought another 8 Grade-A Matched & Batched EVE-280's (all tested out as per the reports showed) to hold 290-292 AH Gross so a full 280AH from the Working Range of 3.000-3.400 and are very well matched & stay in the balance up to 3.500 with minimal divergence.

Amy Wan @ Luyuan Tech is Well Known and Well Respected here as a Top Vendor who delivers genuine Matched & Batched Cells and quality Bulk Cells dfirect from Manufacture, NOT brokers or resellers.
Vendor: https://szluyuan.en.alibaba.com/
Contact Amy Way (Owner) via Chat/Messenger for ACCURATE SHIPPING QUOTE
Properly Matched & Batched cells are supplied with full test report through cycles.
* Can also supply BMS' and sundry supplies (saves a LOT on shipping) if you put it all together.
** Mention you are coming from THIS Forum !

FYI: Shipping from China is a Major PITA and some Ports of Entry are exceptionally BAD, so depending on where you are it can be slow. At this time US West Coast is the worst worldwide, it's self fuelling backlog is just worsening daily. Bad enough that shippers are abandoning whole containers as the "storage Fees" while waiting for processing exceeds the value of the goods within.

I am now doing a full & final reconfiguration of my whole solar system and this includes harmonizing all of my battery packs and my main bank as well. Both Solar Systems are 24V so I want to get things unified and simplified.

All 24V Packs are simple 8S Builds. All Parts & Components can be had through Amy Wan, just provide Link & Info and she "MAY" even be able to get a better price too.
Each is getting the following:
JK-BMS [24S 2A 150A BT] with BlueTooth Part Number: B2A24S15P $143.29 USD
Product Link: https://www.aliexpress.com/item/1005003104573871.html
-plus add: CANbus Module + RS485 Module $7.73 USD each
Product Link: https://www.aliexpress.com/item/1005003451100409.html

- Each Pack is fused at the DC-BUS Bar with an MRBF 200A Fuse REF: https://www.bluesea.com/products/category/16/72/Terminal_Fuse_Blocks

Money Saving TIP !
Many people buy bits & pieces from various suppliers and with each one, they take a shipping hit, even crap from across our own country get's a Pinch added to it for good measure. Using Amy as an example, if she supplies the battery cells and get's all the "BITS" like BMS, Ring Terminals and puts that all into one box, and ships with everything else the cost saving sare instant, and you also get all the goodies you need at once and so there is no Thumb Twiddling when you have parts in front of you... That makes everyone a bit cookoo !

BMS will require:
18-22AWG Ring Terminals for the Sense Leads.
7-AWG Ring Terminals if attaching direct to 7-AWG wires from the BMS _OR_ ONE 4-AWG Ring Terminal can accommodate the TWO 7-AWG. ( 7-AWG X2 = 4-AWG )

Please download Luyuan Tech Basic Lifepo4 Assembly Guide you'll find that quite helpful.
Other links in my Signature may be of assistance to you as well.
Hope it helps, Good Luck
 
I have been thinking about that for a while from a technical point of view (less on the cost and ease of installation) and this is what I came up with based on my readings and experience as EE.

For most (all?) "drop-ins", each battery has its own independent BMS that will disconnect the battery in case of an abnormal situation (overcharge, over-discharge, temperature, current) and if multiple batteries are connected in series or parallel there is no cell balancing across the different batteries. The same could be said for DIY strings of cells connected in parallel, each with its own BMS and where there is no balancing across the parallel strings.

I see the following potential challenges when using drop-in batteries (or DIY strings) in parallel:

  • Cell unbalance: The BMS's have no way to balance cells across the batteries. Without going into technical details you can be sure that within a few years there will be significant cell unbalance across the batteries (faster if the batteries have not been built with grade A cells that have been matched for capacity, internal resistance and other characteristics, or if the connections between the different batteries and the common buses do not have the same resistance). Currents will flow across batteries based on each battery voltage and resistance. That can lead to individual cell overcharge or over-discharge if there is some unbalance within a battery. These situations will trigger the BMS to disconnect the battery.

  • Wasted capacity: as cells get unbalanced, a battery will be disconnected by its BMS before the other ones are full (same on the discharge side)

  • Chain reaction: once a BMS has disconnected a battery, the load will be carried by the other batteries that may not be able to carry the increased current and may get disconnected...

  • Impact of a bad cell: a single weak or bad cell will lower the voltage of the battery it is in and cause other paralleled batteries to charge it. This can lead to a dangerous situation if the other cells in that battery are full and get over-charged. Due to those currents flowing across batteries, it reduces the usable capacity of the entire pack.

  • You will not know there is a problem until it is too late: how will you know there is a bad cell or an unbalance? only when one or more of the BMS's regularly shut down its battery for cell over or under voltage... and that does not give you much time to react or fix the problem (if it can be fixed). Some have BT monitoring application that may give you advanced warning (?)

  • Faster cell ageing: Most drop-in batteries shut down the battery with electronic switches (MOSFET). Depending of the quality (price) of these electronic switching devices they can have significant internal resistance that will generate heat when the current is high. As the BMS is just above (or on the side of) the cells, the cells will be heated and will age faster (see the article on Why temperature of lithium cells is important)
High quality drop-ins may overcome some of these challenges, but the cost is not the same.

On the DIY side, cells are quite easy to assemble to get the voltage and capacity you need in a single string with an external BMS. That will give you much more control over your installation while maximizing the usable capacity of the pack and its lifespan. Just to name a few benefits:
  • all the cells are balanced by the BMS
  • the chargers are protected by turning them off before disconnecting the battery in order to avoid voltage spikes / surges that will damage alternators and other chargers
  • avoid power loss by connecting a backup FLA battery to your installation before disconnecting the lithium battery
  • give advanced warning if anything gets slightly out of the standard (plenty of time to analyze and fix the problem before the battery gets damaged) - critical on a boat where you cannot afford to loose power without notice.
  • keep the battery within optimal charge state in relation to its usage and the capabilities of the charge sources (summer, winter, storage, keep battery full, forced balancing...)
  • simplification of the installation and its setup by having a single center of command...
So my take on it is that drop-in batteries can be cost effective and are a good fit for small land based installations (all the required capacity can be supplied by a single battery). But as soon as you need to connect multiple drop-in batteries together I would look the DIY way and assemble the cells I choose with the BMS that fits my needs.
 
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