DIY Battery dilemma: (Build vs Buy)

[wpns]

I don't wanna start anything cause I'm not sure I understand it correctly, but it's the Lifepower4.

That’s not good, I’ve got a half dozen PowerPro that are kinda a black box, listed as passive balancing, how would I know if they have the same issue?

 

[rogerheflin]

From reading all of the BMS issues and/or pre-build battery issues it is becoming very clear that the companies building pre-built batteries may not know anything more than we do. It is also becoming clear that it seems that all BMSes seem to have issues reporting SOC correctly if the battery does not hit 100% or close to 0% to know where it is .

I build my own simply because I know I will eventually need to fix it(just like every appliance), and there is a high chance (in a few years) that whoever built said battery may not be around anymore making the warranty pointless, or may claim it is an unsupported produce, please buy a new one.

And if you build it yourself you can at least make sure to use the same BMS on all and you know what cells you have, and/or upgrade all batteries BMS'es to the same firmware and/or new hardware.

 

[Brucey]

That’s not good, I’ve got a half dozen PowerPro that are kinda a black box, listed as passive balancing, how would I know if they have the same issue?

I believe you can see the individual cell voltages on the eg4 app or maybe on the batteries displays themselves?

 

[Quattrohead]

That’s not good, I’ve got a half dozen PowerPro that are kinda a black box, listed as passive balancing, how would I know if they have the same issue?

Look at the cell voltages on the display and you can also see the highest/ lowest in the app and web portal.
But I know you already know that

 

[wpns]

Look at the cell voltages on the display and you can also see the highest/ lowest in the app and web portal.
But I know you already know that

Yeah, except I'm in the wrong 'mode' so I don't see the individual cell voltages, just max and min across all 6 batteries:

And the delta is generally less than 100mV:

and in the 'under 10 mv' range during discharge. They are only 6 months old, so hopefully by the time I get all the firmware updates done and the new monitoring in place I can know what's going on...

 

[Brucey]

Yeah, except I'm in the wrong 'mode' so I don't see the individual cell voltages, just max and min across all 6 batteries:
View attachment 248622
And the delta is generally less than 100mV:
View attachment 248623
and in the 'under 10 mv' range during discharge. They are only 6 months old, so hopefully by the time I get all the firmware updates done and the new monitoring in place I can know what's going on...

My understanding is the biggest issue with balancing on the eg4 batteries is with the original lifepower 4s using Narada BMS units. So may not be as big an issue on their newer 280Ah batteries and their lifepower v2s.

 

[shadowmaker]

My new factor in DIY vs. prebuilt is I've been woken up to how broken some prebuilt's BMS balancing schemes are.

My DIY battery you can literally just hold at the balance voltage (55v/3.437vpc for me) and it will balance continuously until the entire pack is whipped into perfect balance (<.007). No need to cycle, just hold it there until it's done.

I couldn't believe a couple months ago when I discovered my prebuilt server rack battery cannot also do this, it identifies high cells on the way up and then applies a balancer to those until they're in line, but it does not then identify the next highest cells when held there. You would have to repeatedly cycle it to get it to re-identify the next highest cells. That's hot garbage to me.

I have prebuilts only and they are cheapest Chinese shit one could find (~175e/kWh 2y ago, ~125e/kWh 1y ago, VAT24% and home delivery included). One had damaged cell which I changed myself (got it free from manufacturer) and then installed Neey balancer wiring to some of them as original ~50mA passive balancer wasn't beefy enough in some cases. Two latest ones had their balancer/voltage detection wires badly soldered, so resoldered them and installed Neey wiring while I was at it.

It takes me about one hour to install Neey wiring and it costs something like 15e. I need only one balancer (Neey 4A, ~85e) that I change between batts if ever needed, but usually they seem to need only one top balancing and then original balancer is good enough to keep them balanced.

Also got BMS tool from manufacturer so I can change BMS parameters to my like.

 

[tinyt]

I always DIY if I can.
But I know my limitations, so I use small EVE F105 cells for a tiny build.
This is a work in progress of three S16 cells each with JK BMS.
Middle rack is being tested with a 5A power supply.
The plan is to put each of them on the 3 shelves of the cabinet from amazon. It is modified with cable exit holes, TTL UART exit holes, vent holes, and forced air cooling triggered by a 40C thermostat switch.

 

[Loadtoad]

Being budget conscious, I have done research on DIY LiFePO4 battery kits with aims to potentially lower the battery cost and/or get more battery capacity for the money. Based on what I have learned thus far watching videos in YouTube, these kits can cut in half or more the cost of batteries with storage capacities between 14 Kwh and 16 Kwh per box, as they tend to go for 9 to 15 cents per watt hour of battery storage (perhaps cheaper, depending on the battery kit/cells brand, prices and/or deals). Specifically, I'm paying special attention to the Basen Green 48V 280A to 314A DIY kit (https://www.basengreen.com/product/diy-case-for-48v-battery-packenclosure-accessories-usa/). Why this kit? The BMS/controls come assembled from the factory with an equalizer unit and battery breaker, overall simplifying assembly and enhancing safety. A complete kit with 16 314A battery cells will go for $1,925 per box (11 cents per watt hour) and free shipping from a US distribution facility. The only thing this kit does bring is fire suppression capability. This option opens the possibility to be able to get three 16 Kwh batteries for the cost of two EG4 14 Kwh indoor wall-mounted batteries. However, it looks like these battery kits are more suitable for off-grid applications, and not so much to grid-tied setups (correct me if I'm wrong).

couldn't find anything on UL cert?

 

[Brett V]

I'm in the DIY camp. My battery build is linked in my signature.

 

[dareggaemon]

@RScupper UL listing or meeting ABYC standards is important for insurance purposes.
Up in smoke without it could mean total loss with no recourse.

Homeowners insurance covers stupid. As long as you don't intentionally burn down your home you'll be covered. However, your insurance company may drop you after the payout. Plenty of people have burned down their homes with shoddy work and their homeowners insurance covered it.

 

[OffGridInTheCity]

Homeowners insurance covers stupid. As long as you don't intentionally burn down your home you'll be covered. However, your insurance company may drop you after the payout. Plenty of people have burned down their homes with shoddy work and their homeowners insurance covered it.

I have State Farm. I had an incident with some DIY (definitely non-UL) work last April 2024 and they took care of me + neighbors, paid very well, and offered the regular renewal with normal rates last Aug 2024. I still don't understand how things work or if each case is individual as no one was volunteering the details and it didn't seem in my best interest to *insist* on details as things were handled 110% in my favor. State Farm made it's own determinations!

Here's the story....
I built a DIY shed under my ground PV array and did a DIY generator exhaust thimble thru the wall. Over time this DIY thimble apparently caused a fire in the wall of the shed. This would have been relatively minor BUT... the heat ignited 10 x 100lb propane bottles stored along the outside wall of the shed causing a huge blowtorch... that burned up my solar panels, destroyed some rain harvest tanks, melted my neighbor's pool liner, cracked windows and destroyed some fencing. This prompted a local fire dept investigation but also a full IAAI fire investigation / report that could be used in court. No one shared any details with me! The State Farm agent said that he could share the IAAI report but in a friendly/tone of voice that said I should leave it alone.

I was told by State Farm that I was absolutely cleared of fraud or arson but was found negligent to some degree (DIY work? propane tanks stored along a shed wall? - no one actually said or to what degree) because they handled (paid?) claims of the neighbors thru the liability portion of my insurance. I gather that if I wasn't negligent, the neighbors would have been required to pay their own expenses via their own homeowners and of course could have tried to sue me - so in a sense it was a blessing to be 'a little negligent' as then State Farm swooped in and handled things. Neighbors seem 100% satisfied.

I'm still interested in how all this works but non-UL = non-coverage was not true in my episode.

 

[Drunkin Solar]

Man you are lucky with your State Farm payout

Off topic here but that company completely screwed my wife four years ago when straight line winds took down five HUGE trees around her property and house causing massive destruction. They estimated 86k in damage (in reality the damage was probably 135k) and paid out only 31k for the damage. Disgusting company in my book.

I'm in the build your own camp. I like bang for the buck