Future of DIY LiFePO4 looks bleak…

[upnorthandpersonal]

No one has DIY'ed a better unit, I bet my right nut on it.

Issues with the battery (and I'm using the pro version for these):

- individual cells can't be serviced
- 100A maximum charge/discharge per pack (with a 30A recommended discharge mentioned in the manual)
- only up to 16 packs in parallel which limits total capacity to 80kWh
- Needs a 19" rack to properly mount more than one, adding to the cost
- 125A breaker. I prefer a Class T fuse and don't trust a breaker near as much, especially when it's also intended to be used a a main switch

 

[Nobodybusiness]

Did you look at Wills latest review on the EG4 unit ? No one has DIY'ed a better unit, I bet my right nut on it.

Cost is still $.29 WH for the battery he just reviewed.
DIY is almost half that.

Plus all those cells are laser welded in and cannot be fixed if they go bad.

Guarantee mine is just as good at half the price.

 

[MrM1]

Did you look at Wills latest review on the EG4 unit ? No one has DIY'ed a better unit, I bet my right nut on it.

I wouldn't. I dont have one (left yes, right no)

 

[robby]

Did you look at Wills latest review on the EG4 unit ? No one has DIY'ed a better unit, I bet my right nut on it.

Can we hold you to that
I know a guy who will collect if I prove you wrong.

 

[Dzl]

Did you look at Wills latest review on the EG4 unit ? No one has DIY'ed a better unit, I bet my right nut on it.

Good thing you are only wagering one of them

If you spend enough time poking around the forum, you will see lots examples of DIY batteries with impressively high build quality and attention to exceeding what you will find in a typical budget conscious pre-built. That is not a jab at the EG4, it looks really solid and thoughtful design for a prebuilt, and its likely better designed/built than the majority of DIY builds, but the idea that no custom build could produce a better battery than a decently built mass produced battery is rather unlikely in my eyes. BMS quality alone is one area where DIY can excel.

 

[Ampster]

No one has DIY'ed a better unit,

Better? My DIY 3P16S 42kWh may not be better in your eyes or Will's eyes, but it suits me fine. It is more cost effective, has a BMS that gives me access from anywhere in the world with graphs that give me comfort about the health of my pack and fits on the space I had available. That is why I DIY'd it the way I did.

 

[offgriddave]

The EG4 has a pre-charge resistor. Does any DIY pack have that? (Without the manual 2-1 switch).
I bought it because it has the pre-charge resistor. When I started out in DIY last April, I discovered a resistor was needed and thought it was silly. Not a single build explains what resistor you need except "you need a big one" and finally I asked directly here and somebody linked to the actual resistor to buy. I thought it was ridiculous that this wasn't built in to either the inverter or BMS. I mean come on, DIY designs that arc weld in your face every time you plug it in? And you don't know about it until after you bought everything. When I found out the EG4 had one built it, it was immediately purchased.

 

[MrM1]

The EG4 has a pre-charge resistor. Does any DIY pack have that? (Without the manual 2-1 switch).
I bought it because it has the pre-charge resistor. When I started out in DIY last April, I discovered a resistor was needed and thought it was silly. Not a single build explains what resistor you need except "you need a big one" and finally I asked directly here and somebody linked to the actual resistor to buy. I thought it was ridiculous that this wasn't built in to either the inverter or BMS. I mean come on, DIY designs that arc weld in your face every time you plug it in? And you don't know about it until after you bought everything. When I found out the EG4 had one built it, it was immediately purchased.

My push button resistor is built into my switch gear. See my signature.

And with the EG4 and it's built in Resistor, on another thread the built in pre charge resistor seems to be the reason that the Schneider XW will not start. So not sure a built in pre charge resistor that does not have user programmable parameters is a good thing

Schneider xw pro 6848 not powering up with eg4 lithium battery

I recently purchased 4 of the eg4 lifepower batteries to replace my 48v crown cr430 flooded lead acid setup. I installed the four batteries in the rack made for these batteries and checked voltage on each module before paralleling. All modules showed 52.8 volts. I set all of the dipswitches as...

diysolarforum.com

 

[upnorthandpersonal]

The EG4 has a pre-charge resistor.

And it won't work properly in the event that the you turn off the inverter and the caps discharge, and then you turn the inverter back on. The pre-charge circuit only works at the time you turn the battery on. That's why the battery is the wrong place to have this - it should be part of the inverter to begin with.

 

[robby]

No, they don’t. The exact reason i DIY is because there are no commercial offerings available that match the quality of the components i use.

I don't know how you have come to that conclusion. I have had hours of discussions with the lead tech at Fortress Power and I know that them plus several other companies buy brand new Grade A cells directly from the manufacturer in batches that exceed over a thousand units. These cells are then tested again at their assembly plant before they go into the Battery pack. The BMS they use comes from the Auto Industry along with the massive relay that engages power. My eFlex batteries are in 4mm thick Aluminum water proof case. These thing would be super hard to replicate the quality in a DIY Project. Price is about the only major selling point of DIY as it can be a lot cheaper than the commercial offering but that is changing right now on the lower end of the pre built the scale. Example EG4 is pretty cheap and it makes a DIY job not as attractive as it was before. I am just not sure if those lower priced packs have much better quality cells than you can pick up in the DIY trade. Also I question if the Warranty on those cheaper packs will be honored years from now.

 

[toms]

Did you look at Wills latest review on the EG4 unit ? No one has DIY'ed a better unit, I bet my right nut on it.

Most obvious flaw is it’s missing the supercap to prevent AC charge ripple and inductive load surge.

It’s a nice offering, no match for the capability of the systems i have though.

Pretty case and mount system don’t make up for low spec cells and BMS, and missing supercaps.

You can post your knacker to me when you feel free - i’ll feed it to my pet wombat.

 

[toms]

I don't know how you have come to that conclusion. I have had hours of discussions with the lead tech at Fortress Power and I know that them plus several other companies buy brand new Grade A cells directly from the manufacturer in batches that exceed over a thousand units. These cells are then tested again at their assembly plant before they go into the Battery pack. The BMS they use comes from the Auto Industry along with ha massive relay that engages power. My eFlex batteries are in 4mm thick Aluminum water proof case. These thing would be super hard to replicate the quality in a DIY Project.

BYD are one of the largest manufacturers of LiFePO4, i have seen a lot of problems with them. Same with Pylontech - their performance in the field is rubbish. Even Simpliphi with the next step up have too many issues for me to consider recommending.

I’ve explained a lot in this thread how i come to the conclusion my DIY setup is better than commercial offerings. And it has proven reliable with an average of around 15kwh delivered daily for the last decade with zero periods of lost power.

 

[BlackWaterPark]

I’ve explained a lot in this thread how i come to the conclusion my DIY setup is better than commercial offerings

Forgive me if you posted this elsewhere, but did you have a full guide with parts to program laid out somewhere?

 

[robby]

Forgive me if you posted this elsewhere, but did you have a full guide with parts to program laid out somewhere?

Yes I would also love to see this super system.

 

[Dzl]

The EG4 has a pre-charge resistor. Does any DIY pack have that?
I bought it because it has the pre-charge resistor. When I started out in DIY last April, I discovered a resistor was needed and thought it was silly. Not a single build explains what resistor you need except "you need a big one" and finally I asked directly here and somebody linked to the actual resistor to buy. I thought it was ridiculous that this wasn't built in to either the inverter or BMS. I mean come on, DIY designs that arc weld in your face every time you plug it in? And you don't know about it until after you bought everything. When I found out the EG4 had one built it, it was immediately purchased.

I've also never understood--if pre-charge is as necessary as its sometimes made out to be--why even high end inverters are not including this circuitry. I assume there is some logical reason, but it just seems strange. Not only that it is omitted from the products themselves but that its not even really discussed in most inverter documentation from what I've observed.

 

[toms]

I've also never understood--if pre-charge is as necessary as its sometimes made out to be--why even high end inverters are not including this circuitry. I assume there is some logical reason, but it just seems strange. Not only that it is omitted from the products themselves but that its not even really discussed in most inverter documentation from what I've observed.

Because the inverter isn’t the component that is damaged by not using a precharge.

 

[upnorthandpersonal]

Because the inverter isn’t the component that is damaged by not using a precharge.

That's not entirely correct. Because of the high inrush current that can be much more than the nominal current the device can handle, you could even blow PCB traces. For reference:

https://www.ti.com/lit/an/slva670a/slva670a.pdf

Inverters should add a 'soft-start' feature to eliminate these inrush currents, if only to not blow up fuses that shouldn't because of the inrush current.

 

[BlackWaterPark]

Yup, inverters that are poorly designed can go right up in smoke real quick. Quality inverters will shut down to protect themselves... Like mine did recently when I screwed up the initial deployment procedure of the HABs by not giving a 5 second wait between throwing the battery breaker and depressing the power latching switch on.

 

[toms]

Forgive me if you posted this elsewhere, but did you have a full guide with parts to program laid out somewhere?

My system is as follows:

Primary system:
32 cells 2p16s LiFeTech lithium 200ah
REC BMS / Gigavac contactors for main disconnect and DC PV disconnect
NT00 fuse/ disconnect
2x4 pole 300a busbars
Sunny Island 8.0H hybrid inverter
SunnyBoy SB1700 PV inverter
Outback Flexmax FM80 DC charger

Auxiliary system (high inductive loads)
32 cells 2p16s Sinopoly 100ah
Maxwell Supercapacitor
ZEVA BMS / Gigavac contactors for main and PV disconnect (REC precharge)
NH00 fuse/disconnect
2x4 pole 300a busbars
Victron Phoenix 48/5000 inverter
Victron 150/70 DC controller.
240V to 48V charger fed from Kubota J108 generator.

Auxiliary system feeds into generator input of Sunny Island.

System housed in a climate controlled enclosure constructed from 100mm coolroom panel.

As i have said, it isn’t as pretty as a rack mount or enclosed system, but it is more functional.

I don’t take many pictures, but i have some from when i was changing from batrium to REC.

The way the enclosure is setup makes taking photos of the entire setup difficult, there is essentially a sliding panel that seals the whole area.

 

[BlackWaterPark]

My system is as follows:

Sorry, didn't mean for you to type out your entire system, I was asking expressly about the battery itself. I should have been more clear on that. I plan on building one come spring, so plenty of time to order the parts. What's the difference between the 2 BMSs?