My DIY vs Prebuilt comparison - May 2022

[Prefersdirt]

So there will be different posts coming from me as we are getting a new place and I will be taking it almost entirely off grid. A separate post will come about inverter recommendations.

Batteries. This is for a 48V system to provide up to 200A service (to match the grid input).

DIY has costs running like this: (Still waiting on a couple of quotes for cells – this is based on one).

16 230aH cells at $127.58ea for a total of $2041.28​

BMS from Overkill solar at $153​

Miscellaneous for the box - $100.​

Total setup (per battery)
cost: $2294.28 + a few hours of my time.
Capacity = 230 aH / 11 kWh

Prebuilt:

Signature solar – EG4 - $1500 100AH = 4.8kWh​

BuyCheapSolar – $2900 10kWh​

Watts247 – PowerUp $1700 - 5.1 kWh -​

I have two issues with DIY batteries. There is zero communication between the inverter(s) and the battery(ies). None. This makes shutdown at low voltage challenging. I love the idea of being able to tell it “Shut down at X%”.

The other issue seems to be multiple batteries in parallel going slightly out of sync in terms of state of charge. The two I have now were that way for a while. (I need to double check them but am not near them right now).

Just wondering what I am missing in these calculations? If I were starting from scratch, I would love the prebuilt more. But money is a major concern and I can DIY.

Thanks

David

 

[toms]

You can DIY a battery and have communication with your inverter/charger etc. This is my preference for building a system.

I use LiFePO4 cells / REC BMS / SMA inverters AC coupled (Sunny Island, SunnyBoy).

I have set up dozens of these systems for off-grid applications over the last decade with good performance and reliability compared to off the shelf batteries such as BYD B-Box and Pylontech.

If you use quality cells (eg Winston), you will get better lifespan than any prebuilt battery. I haven’t seen a prebuilt parallel system that doesn’t eventually need balancing between the modules.

To address your second comment, with quality DIY cells, parallel until you get your desired capacity- then series. I have done up to 600ah@48V with good results.

If you need higher capacity than that it is likely you need two main inverters and i recommend two completely independent systems.

Remember you can only cost the system when every component has failed - initial purchase price is only one factor.

 

[Prefersdirt]

You can DIY a battery and have communication with your inverter/charger etc. This is my preference for building a system.

Tell me more about how to do this! Do you have a thread on this? Where can I read up on this?

 

[Texican]

also trying to get a handle on actual diy battery costs vs more eg4 which I already have 6
who has bought cells from the outfit that has a warehouse in houston and what is the contact/cost ?
I saw the box/bms by seplos and it looks great, not sure if they are readily avbl now or if alternative box exists.
I have never done a diy battery, but a box/bms like seplos makes it look easy and professional
how much money can diy save ???? the box/bms is 500 plus shipping I think

 

[Rossman]

Tell me more about how to do this! Do you have a thread on this? Where can I read up on this?

It just depends what protocol your inverter speaks and what protocol the BMS speaks. F.ex many inverters support Pylontech battery protocol and many BMS' support it as well.

 

[Rossman]

who has bought cells from the outfit that has a warehouse in houston and what is the contact/cost ?

Many people have bought from Docan in Houston and in general the reviews are favourable. There are a couple threads on them with dozens of pages of reviews here on the forum, f.ex https://diysolarforum.com/threads/our-new-go-to-lifepo4-vendor-09-20-21.28696/

 

[Prefersdirt]

It just depends what protocol your inverter speaks and what protocol the BMS speaks. F.ex many inverters support Pylontech battery protocol and many BMS' support it as well.

I am at a point where I have not purchased anything yet. So I am flexible. What is one inverter that supports the Polyntech protocol - this would allow me to figure out where to find that information in a listing.

 

[AKvalleyguy]

Will recently made a post on YouTube that says the DIY builds are dead, my words not exactly his. I guess I'm a dinosaur since I prefer the DIY build. Prebuilt units look easy and handy to install. DIY cells

If you want to learn, do the DIY. If you have other things to occupy your time, get a wall or rack prebuilt job. On the surface it's that easy.

The Buycheap solar wall battery is/was a 15S battery.

I'm currently testing a 230ah 48v with the Docan cells and a JBD 100ah BMS. Running great to date.

 

[Rossman]

Will recently made a post on YouTube that says the DIY builds are dead

Will isn't the be all and end all of the battery/solar world my friend, he was just saying how his affiliate sales are down for DIY cells and up for pre-built. It is meaningless overall. If I was more cynical I might believe he gets a higher affiliate payment for pre-builts and as such encourages the purchase of such. One can never tell when someone is an affiliate and stands to gain financially

 

[ChrisFullPower]

You get what you pay for. Bottom dollar price means cost cutting somewhere.

 

[Rossman]

You get what you pay for. Bottom dollar price means cost cutting somewhere.

When you DIY when you aren't paying for some company to pay some people to build the packs for you. You save the money that would have gone to labour costs. It's that simple.

 

[ChrisFullPower]

I know the quality of the materials I’m putting into my pack. Yeah a real name brand BMS might cost more but I know it’s quality, it works with my inverters, comes with support, has an actual warranty, and won’t burn my house down.

Same goes for the knock off breakers in server rack packs. You really want to trust that bargain bin breaker with your house or life on the line.

If saving a few dollars is worth it to you the go for it.

 

[Bud Martin]

OP, so what kind of SCC are you going to get? Since you are talking about the inverter, I am guessing you are not going to use all-in-one SCC/inverter unit.

 

[Prefersdirt]

OP, so what kind of SCC are you going to get? Since you are talking about the inverter, I am guessing you are not going to use all-in-one SCC/inverter unit.

I am wanting an all in one. Until recently the AIO units were not able to handle all the solar I am going out up. So an additional SCC would be needed. I know I need one for my 24v system since my GroWatt 3000 cannot bring in more solar than I have on it now. Yet my current setup is not enough for winter.

FYI I wm looking at between 9 and 12k worth of panels being put out.

 

[toms]

Tell me more about how to do this! Do you have a thread on this? Where can I read up on this?

As i said in my reply, i use REC BMS and SMA Inverters. Look at the REC website for details, they have a few system examples there.

 

[toms]

Will recently made a post on YouTube that says the DIY builds are dead, my words not exactly his. I guess I'm a dinosaur since I prefer the DIY build. Prebuilt units look easy and handy to install. DIY cells

If you want to learn, do the DIY. If you have other things to occupy your time, get a wall or rack prebuilt job. On the surface it's that easy.

The Buycheap solar wall battery is/was a 15S battery.

I'm currently testing a 230ah 48v with the Docan cells and a JBD 100ah BMS. Running great to date.

My experience with prebuilt server rack systems (BYD / Pylontech) is that they fail prematurely. While they are running if they are used close to their capacity limits they suffer imbalance issues.

 

[AKvalleyguy]

Will isn't the be all and end all of the battery/solar world my friend, he was just saying how his affiliate sales are down for DIY cells and up for pre-built. It is meaningless overall. If I was more cynical I might believe he gets a higher affiliate payment for pre-builts and as such encourages the purchase of such. One can never tell when someone is an affiliate and stands to gain financially

Haha, yeah. I was trying to be vague and polite. ?

 

[Ampster]

I have two issues with DIY batteries. There is zero communication between the inverter(s) and the battery(ies). None. This makes shutdown at low voltage challenging. I love the idea of being able to tell it “Shut down at X%”.

My inverter and BMS can be programmed to shut down at pack low voltage and my inverter is programmed to switch to grid and charge the batteries when SOC gets to set percentage. I am not trying to talk you into DIY. Just don't pay a lot for a communication feature in a battery when that feature is common in most quality hybrid inverters.

 

[Hedges]

Will isn't the be all and end all of the battery/solar world my friend, he was just saying how his affiliate sales are down for DIY cells and up for pre-built. It is meaningless overall. If I was more cynical I might believe he gets a higher affiliate payment for pre-builts and as such encourages the purchase of such. One can never tell when someone is an affiliate and stands to gain financially

He has cut off his own nose to avoid endorsing products he considers cr*p, so very unlikely he said what he did about DIY cell volume vs. pre-built for financial gain.

That doesn't mean prebuilt is actually higher quality, just that they are functional and he sees the price difference as no longer compelling.

The LiFePO4 cells we've seen were meant to be welded to busbars. That should be the solution to reach, whether DIY or not.

My experience with prebuilt server rack systems (BYD / Pylontech) is that they fail prematurely. While they are running if they are used close to their capacity limits they suffer imbalance issues.

Due to assembly, or due to cell matching? or balancer capacity?

 

[AKvalleyguy]

My experience with prebuilt server rack systems (BYD / Pylontech) is that they fail prematurely. While they are running if they are used close to their capacity limits they suffer imbalance issues.

Good info. That's what I have been curious about but have no experience with the prebuilt systems.

Just don't pay a lot for a communication feature in a battery when that feature is common in most quality hybrid inverters.

100%. As for me, my system has no battery specific communication and all is well for me. My setup is Outback inverters and Midnite Solar charge controllers. Dumb as a box of rocks, communicatively speaking, and works well.