Who is still building DIY batteries

[Dave911]

18650 battery store. Grade A EVE cells. USA seller. JK BMS. 105ah cells were on offer for $48 each. You can do the math. Dedicated locker in a boat. Just built another dedicated locker for the next battery. Each locker contains the class T fuse and BMS as well. Both lockers are mechanically ventilated. Polycarbonate lids so I can see in and Polycarbonate shields over the cells so i can't drop anything orn them.

So that is about the same price as buying a Redodo 100 AH or similar, but you have to build it, wire the BMS and put it into a container.
Putting a plastic shield over the top is smart. I'm not seeing that you are saving anything there.

Dave

 

[Dave911]

For larger capacity batteries, the price difference is still very significant. For instance, if you're looking to add 30kWh+ energy storage, the price difference is going to be ~60% more going pre-built route.

How so? I'm not seeing it.

I've got about 10 kw-hr right now, but I can see it going to 30+ over the next few years. The local utility is asking for substantial rate increases.

I know you can buy cells and BMS's off Alibaba, but from what I understand that is a crapshoot.
Show me the math... please!

Thanks, Dave

 

[Rednecktek]

How so? I'm not seeing it.

So just using Docan as a quick reference, 16x $125 = $2000 for 280Ah cells, a Fancy-Pants JK 200a 48v BMS = $185
So for $2185 you get 280Ah * 48v = 13.4Kwh
The shipping on that (last time I ordered cells) was about $50

The best "value" rack mount batteries are still the basic EG4's at $1360 for 5.2Kwh so you'd need 2.6 of them for the same capacity, or $3500, but since you can't buy 2.6 of them, you'd have to get 3 which would be $4080 and the shipping is going to be $300 at least.

But, we're talking about the Redodo 100Ah 12v cells, so you'd need 12 of those at $229ea or 12 * $229 = $2748 or about $600 more than a DIY but you have balancing issues, but it's a LOT cheaper than rackmounts. Because it's using smaller cells you need a LOT more physical space for those 12 batteries.

So yes, it's getting to be a wash nowadays, the biggest benefits being balancing and space.

Buying via AlibabaxPress can save money over that by a margin, but as you say it's a crap shoot.

 

[Dave911]

16.9 cents per wh.
LF280K from 18650batterystore 16 at $2,304
JK B2A24S20P from AliExpress (JK BMS store) 1 at $125
No case (went commando)

How are you doing the math?

Your total is $2429 / (48v * 280ah) = 18 cents per wh

I would expect your setup to be a lot cheaper than 12 volt prepacked "batteries".

Wouldn't you expect that as well??

These have a plastic box, strap handle and flashy graphics that I will never look at! So no commando for me!

I went back and checked the 18650 store and those batteries you bought are now $125 or $2000 for 16 cells! So they have dropped $304 since you bought them. This is now making sense. I have been watching 12 volt, 100AH batteries prices drop like rocks over the last several weeks. It makes me wonder if the batteries I paid $206 for last week won't be $150 in March!

Maybe in the big picture saving a few hundred is pointless if you don't have a full BMS that will handle 48 volts. After all when you look at it over a 10 year period, saving a few $100 is insignificant if you I have issues. I think I am going to find out!

 

[Dave911]

So just using Docan as a quick reference, 16x $125 = $2000 for 280Ah cells, a Fancy-Pants JK 200a 48v BMS = $185
So for $2185 you get 280Ah * 48v = 13.4Kwh
The shipping on that (last time I ordered cells) was about $50

The best "value" rack mount batteries are still the basic EG4's at $1360 for 5.2Kwh so you'd need 2.6 of them for the same capacity, or $3500, but since you can't buy 2.6 of them, you'd have to get 3 which would be $4080 and the shipping is going to be $300 at least.

But, we're talking about the Redodo 100Ah 12v cells, so you'd need 12 of those at $229ea or 12 * $229 = $2748 or about $600 more than a DIY but you have balancing issues, but it's a LOT cheaper than rackmounts. Because it's using smaller cells you need a LOT more physical space for those 12 batteries.

So yes, it's getting to be a wash nowadays, the biggest benefits being balancing and space.

Buying via AlibabaxPress can save money over that by a margin, but as you say it's a crap shoot.

The rackmounts just don't make any sense to me. I think the manufacturers need to come up with a more easily handled design. Assembling cells and adding a BMS makes more sense than the rack mount package. An assembled battery is repairable. If a Redodo dies, I take it out and ship it back for warranty (I hope). But I think the rack batteries is a truck shipment?? That's expensive and a hassle.

Redodo and others are now coming out with Mini 12 volt, 100AH batteries that are significantly smaller. If the on board BMS could communicate with the other BMS's via a plug in jack or something, that could be a really nice feature. Daisy chained multidrop Modbus RS485 would be pretty easy to add via a phone or RJ45 jack.

The last 4 Redodo batteries I bought were actually $206 each with free shipping and a 5 year warranty. The previous 4 I purchased were about 20% more and that was only a few weeks prior!

I have a barely used basement, so I could put 36 Redodo batteries on shelves and not be bothered at all. So fortunately space is not an issue for me.

 

[42OhmsPA]

Who isn't still building DIY batteries...?
~$6k for ~39kwh including BMS's the old front bench and the new in progress shelf
If the Envision 305s were around when I bought the 32 230s that price would be around a grand less for ~47.5 kwh...
Imo if you're going for high capacity and frugal diy is the only way.

Someday I'll have capacity close to some of the other amazingly skilled users here, along with a much nicer setup.

I've been keeping my eye open for over a year for a nice 'scrap' cabinet at work, I expect to find one within a week of finishing the shelf... Then I'll have to order more cells and start over again, 3rd times a charm ?

Edit - the dangling negative leads have been taped (sticky side out) since taking the photo.

 

[NCislander]

Is there really that much of a savings with a DIY battery with prices coming down so fast?

I am a DIY guy but after seeing so many LI ebike battery fires and explosions I try to steer people away fro DIY builds.

Not because I think they can't be done safely but because the young people doing it don't have the technical knowledge or skills and I don't want to hear about another family being burned up in a battery fire.

I know, LFP are not LI and much safer so an LFP battery might be a lot safer to build.

I see Tesla and some other EV manufacturers are switching to LFP and a new solid state is supposed to be on the way that has the capacity of LI but safety of an LFP.

LFP Battery Cells are much safer.
I recently experienced an OverCharged condition. Blew out the Pressure Seals on (2) Pristine, New, EVE LF280K cells. Pressure seals blew out because that is how they are designed. They did their job.
No sparks, No fire. Quite a lot of heat on each cell, but nothing else. Each were as safe as I can imagine. No Bus Bar disconnect. All remained intact except for the massive cell expansion, and pressure seal release.
The OverCharged condition was 100% my fault. Incorrect cabling bypassed the JK BMS. BMS was unable to cutoff charging.

Cabling has been corrected, (2) cells replaced. Battery Bank & JK BMS are 100% performing. LFP Battery Cells have my trust and confidence.
EVE LF280K Cells are very safe.

 

[Solarcabin Channel]

I recently experienced an OverCharged condition.

Why didn't the BMS stop the overcharge?

 

[JJJJ]

3rd times a charm

This is one area where the DIY process shines. I am amazed at the quality and in some cases the magnitude of the DIY builds that I have seen presented on this forum. At the other end is the tight compact look which also serves the purpose.

DIY keeps the creative juices flowing, whether it is building a battery, remodeling around the home or another project.

Forums such as this provide feedback to help us build the best, safest systems possible. Many systems have logged thousands of hours and still keep ticking.

 

[NCislander]

Why didn't the BMS stop the overcharge?

Due to cabling to the 48vdc Bus/ Bypassing the BMS by mistake. Since corrected.

 

[JaVid]

I have 29kWh of DIY batteries.

Honestly, if I was starting over today, I think it would be better to just buy server rack batteries, but they weren't around when I started.

Now that I know how to DIY, I will continue that direction because I have the system down, but I put SO much time into learning how to make a DIY battery that I will never get back lol

 

[a619]

How so? I'm not seeing it.

I've got about 10 kw-hr right now, but I can see it going to 30+ over the next few years. The local utility is asking for substantial rate increases.

I know you can buy cells and BMS's off Alibaba, but from what I understand that is a crapshoot.
Show me the math... please!

Thanks, Dave

I recently bought 32 Envision cells (305Ah) for $79 each from 18650 store. With an extra cell/ taxes/ shipping, this was ~$2900. Add 2 BMS for $300 and another $200 for cabling/ fuse etc., it comes out to be $3400 for ~29kWh ($0.117/Wh). You can add nicer cases for another few hundred, but this came out much cheaper than any other equivalent options I saw on market last month

 

[timselectric]

How are you doing the math?

Shipped price
$2,429 ÷ 14,336wh = 16.94 cents per wh.
We can call it 17.

I would expect your setup to be a lot cheaper than 12 volt prepacked "batteries".

For a small battery bank, it's not much difference.
But for a large bank, it adds up.
It takes me about an hour to build each battery.
And 50% more cycle life is the same as a 30% cost benefit.
Not sure if you are factoring shipping in the price.
And for each 4 pack of 12v batteries in series, you'll need a balancer. Or have to separate the packs and manually balance them. I wouldn't want to deal with that every 3 to 6 months, even with a small bank.
The best thing about BMS controlled LFP batteries is that they don't require any maintenance.

 

[upnorthandpersonal]

Keep in mind not everyone lives in the States and can buy an EG4 for $1500.

I've made several price comparisons over the past few years:

DIY LiFePO4 Cost Analysis - February 2022 Edition

Disclaimer: I mention vendors below and use them as an example and as reference. This should not be considered an endorsement of said vendors! In light of Will's recent video and some of the comments both there and on the forum, I thought it would be a good idea to do a full cost analysis of a...

diysolarforum.com

DIY LiFePO4 Cost Analysis - Almost February 2023 Edition

This is a recalculation based on the situation today, of what I did last year. Disclaimer: I mention vendors below and use them as an example and as reference. This should not be considered an endorsement of said vendors! Let's start again with leveling the playing field. The EG4 is a 5kWh...

diysolarforum.com

DIY LiFePO4 Cost Analysis - July 2023 European Edition

After making a couple of posts detailing the costs for DIY LiFePO4 based on a couple of popular vendors, I though of making one that uses cells available for purchase in the EU, with only the BMS from Aliexpress. Disclaimer: I mention vendors below and use them as an example and as reference...

diysolarforum.com

The latter one is Europe specific.

These were all done without going to the absolute cheapest cells available, but rather using vendors with decent reputation (like NKON in Europe, Luyuan, etc).

I've got about 60kWh right now, and I'm seriously considering bringing that to 100kWh in the near future. It will definitely be DIY again. I expect a decent drop in cell prices soon. NKON already has LF280k cells for 105 Euro.

 

[TimE]

So that is about the same price as buying a Redodo 100 AH or similar, but you have to build it, wire the BMS and put it into a container.
Putting a plastic shield over the top is smart. I'm not seeing that you are saving anything there.

Dave

The intention isn't to save anything. It's to have better cells and BMS than a cheap battery. It's to have an active balancer not a passive balancer inside a battery case creating possible hot spots on the cells that will cause premature cell failure. Its having a BMS i can adjust and see what is going on at cell level via bluetooth on my phone anytime I want. It's having a supplier I can talk to if I get a problem.
It's having proper compression in the cells and a battery that will cope with high ambient temperature because the cells and BMS have mechanical ventilation.
I have heard so many times how people think a DIY battery is a poor cousin of a professionally build battery. How wrong they can be. If you use crap components, you get a crap battery

 

[RV10flyer]

16.9 cents per wh.
LF280K from 18650batterystore 16 at $2,304
JK B2A24S20P from AliExpress (JK BMS store) 1 at $125
No case (went commando)

All of mine except work van went commando. ?

 

[Brucey]

Redodo has been selling 12 volt, 100ah RV style LIFEPO4 batteries recently at some low prices on Amazon and Ebay.
Just bought 4 of them for about $210 each with shipping.
1250 watt-hours per battery, so $210/1250 = 16.8 cents per watt-hour, assembled, with a BMS, and a 5 year warranty. Nothing to do other than charge them and hook them up. If one dies, I can pull it out and replace it and hopefully have it covered under warranty if it is less than 5 years old. The Redodo cells are made up of prismatic 100ah cells along with a BMS, stuck into an automotive style box. There is a lot of extra space in the box. There are some teardown videos on Youtube.

I looked at doing a DIY 48 volt battery but with the cost of BMS's, cells and shipping it didn't seem to make any sense.
Redodo says the built in BMS can support 4S4P without any issues.
I previously bought 4 Redodo batteries and they seem to be fairly high quality.
Together with the previously purchased 4 batteries I have about 10 kwhr of battery at 48 volts (4S2P) for about $1700. The first few I purchased were more expensive.

I've done electrical/electronic work for a long time, so hooking up DIY batteries would not be a problem, I just didn't see how it makes any sense right now.
The server rack batteries seem ok but if one dies, then what? Plus they are not cheap. If one fails I am out a lot of capacity. Do I setup a truck shipment to send it back for warranty? Do I tear it apart and try and replace the bad cell/s?
I doubt they were made to be user serviceable.

Anyway, tell me why I was wrong to purchase these Redodo batteries. I am seriously looking for honest criticism.
Is this the wrong way to go?

Depending on how my solar setup goes, I may be expanding this Redodo battery bank to 20 kwhr fairly soon. If this is the wrong direction, save me some money!

Thanks, Dave

I have four of the Redodo mini 100Ahs. I've been using them as additional batteries for my river 2 and Delta 2 max. Current Amazon pricing is $900 shipped for a four pack. Clearly some significant savings versus the rack form factor units like the basic SOK with no display or base eg4. Also to diy your own 100Ah 12V you are looking at $240 for four cells (assuming 18650 and 105Ah eve cells) and then BMS costs on top.

So at the 12V 100Ah level I don't see how you can get cheaper with diy. However the cheaper commercials are a black box in terms of not knowing the internal cell voltages/balance. And may need external balancing on occasion. There are exceptions like the powerurus with bt etc but their price is significantly higher.

However once you start diy with the larger capacity cells, 230, 280, 304, that's when the savings versus off the shelf comes into play. Because they cost less per Ah versus the 100/105Ah cells. And the BMS cost is spread over more kWh.

Personally I like the portability/size of the minis (~20lbs each) and the redundancy from having many, versus potentially all eggs in one basket with single rack mount. At some point I will series mine to 48V and use it as a 5kWh expansion battery for my Delta 2 max (charging the d2m at 500W*2 via the mppt ports), for less than the price ecoflow wants for their 2kWh expansion battery. Ideally we will get smart minis at some point (BT, low temp cutoff, maybe heated). I'm also seeing a few more commercials using 130Ah cells (260Ah and 460Ah) coming on the market.

But certainly for $ per kWh for the bigger batteries DIY is still the better value.

 

[TimE]

I have four of the Redodo mini 100Ahs. I've been using them as additional batteries for my river 2 and Delta 2 max. Current Amazon pricing is $900 shipped for a four pack. Clearly some significant savings versus the rack form factor units like the basic SOK with no display or base eg4. Also to diy your own 100Ah 12V you are looking at $240 for four cells (assuming 18650 and 105Ah eve cells) and then BMS costs on top.

So at the 12V 100Ah level I don't see how you can get cheaper with diy. However the cheaper commercials are a black box in terms of not knowing the internal cell voltages/balance. And may need external balancing on occasion. There are exceptions like the powerurus with bt etc but their price is significantly higher.

However once you start diy with the larger capacity cells, 230, 280, 304, that's when the savings versus off the shelf comes into play. Because they cost less per Ah versus the 100/105Ah cells. And the BMS cost is spread over more kWh.

Personally I like the portability/size of the minis (~20lbs each) and the redundancy from having many, versus potentially all eggs in one basket with single rack mount. At some point I will series mine to 48V and use it as a 5kWh expansion battery for my Delta 2 max (charging the d2m at 500W*2 via the mppt ports), for less than the price ecoflow wants for their 2kWh expansion battery. Ideally we will get smart minis at some point (BT, low temp cutoff, maybe heated). I'm also seeing a few more commercials using 130Ah cells (260Ah and 460Ah) coming on the market.

But certainly for $ per kWh for the bigger batteries DIY is still the better value.

My 8x280Ah cells cost $1100. BMS another $135. Another $50 for ancillaries.
JK 200A BMS with 2A active balance being used on a 24v pack. Second 24v 105Ah battery build, about to start with another JK BMS. I didn't need the capacity of a second 280Ah battery so opted for the smaller second battery. The resilience of a pair of parallel lithium batteries was the main gain for me, being on a boat.
Total battery cost for 385Ah at 24v (770Ah at 12v) will be $1850. With 400A BMS capacity. The coast per Ah are almost identical to your cheap batteries, even with the spread over small and large sized cells

 

[Dave911]

I appreciate all of the replies. I'm still processing all of the info.
I would have no issue doing a DIY battery. I have tools and experience, so that's not a problem.

However I wonder about buying raw cells:

1. Are they actually quality cells and how do you know that? Even if you test them and they test good initially, how do you know they didn't shortcut something that will make them useless in 700 cycles?
2. Do the raw cells have a warranty? 18650batterystore.com offers a 1 year warranty on their cells apparently. So that's roughly 350 cycles.
3. Bare BMS units from what I have heard can be unreliable. Do they have a warranty that you could use? I've read quite a bit about failed raw BMS modules.
4. Packaged batteries generally come with a longer warranty. Redodo is at 5 years. Will they honor it?? Will 18650?? I don't know. The EG4 battery has a 5 year warranty. But shipping it back might be costly. 5 years x 365 =

I probably won't be buying more batteries or cells for a DIY battery until next year but I will be watching the prices. But I will likely need another 10-20 KWHR of capacity to get to where I want to be next year.

Dave

 

[upnorthandpersonal]

1. Are they actually quality cells and how do you know that? Even if you test them and they test good initially, how do you know they didn't shortcut something that will make them useless in 700 cycles?

How do you know the cells in off-the-shelf packs are? The cells come from the same factory, and you can get 'EV grade' or whatever you want to call them and they'll be exactly the same as the ones that go into cars. That said, I run 'grade B' cells to power my house, going into my 5th year now. No issues.

2. Do the raw cells have a warranty? 18650batterystore.com offers a 1 year warranty on their cells apparently. So that's roughly 350 cycles.

Will an off-the-shelf vendor be around to honor the warranty in x years?

3. Bare BMS units from what I have heard can be unreliable. Do they have a warranty that you could use? I've read quite a bit about failed raw BMS modules.

JK and others are pretty reliable. If it fails, you can at least replace it. I run 4x 100A versions of the JK for years now 24/7. No issues.

I probably won't be buying more batteries or cells for a DIY battery until next year but I will be watching the prices.

Same. I expect the cell prices to drop, but we'll see. I plan to add another 40kWh minimum.