featherlite
Solar Enthusiast
LOL!!!No case (went commando)
LOL!!!No case (went commando)
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.Not having a single balancer that operates over all of the cells (48 volts) could be an issue. Redodo recommends rebalancing the batteries in a bank every 6 months. Redodo says they use Grade A cells, so we will see. I'm just going to do it and then check for balance periodically. That's pretty simple to do. TimE, are you factoring in some type of case around your cells as part of your build cost. I added up the costs to assemble a 48 volt battery with cells and a BMS and I could not get close to the Redodo cost. Where are you buying Grade A cells and a BMS that costs only slightly more than the Redodo cost of 16.8 cents per watt-hour? Are you buying cells with any type of warranty? If raw Grade A cells and a BMS was significantly cheaper than the Redodo's I would have gone that route. But everything I could find was significantly more expensive. I think the best was the B grade cells from 18650. And I'm not sure its smart to invest a bunch of $$ into B grade cells from what I have read.
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.
Well said.I know, LFP are not LI and much safer so an LFP battery might be a lot safer to build.
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.
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.
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)
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.
LFP Battery Cells are much safer.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.
Why didn't the BMS stop the overcharge?I recently experienced an OverCharged condition.
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.3rd times a charm
Due to cabling to the 48vdc Bus/ Bypassing the BMS by mistake. Since corrected.Why didn't the BMS stop the overcharge?
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 monthHow 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
Shipped priceHow are you doing the math?
For a small battery bank, it's not much difference.I would expect your setup to be a lot cheaper than 12 volt prepacked "batteries".
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.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
All of mine except work van went commando. ?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)
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.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
My 8x280Ah cells cost $1100. BMS another $135. Another $50 for ancillaries.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.
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.
I probably won't be buying more batteries or cells for a DIY battery until next year but I will be watching the prices.