About to start 48v hybrid system

Hello people
This is my first post, though I've been reading you for a long time while separating some budget for my build. It has passed some time so my initial ideas are obsolete, and that's why I ask for some recommendations.

My plans were to start with some solar panels and "piggyback" inverters for direct consumption, but now I think it could be better to start with a powerwall system and charge it during low cost grid intervals. I'm software architect and analyst so I host a small lab for myself and have the house pretty connected.In my area, energy supply is a total s**t, and I'm used to lose equipment yearly. The last one was an overvoltage that literally burnt a remoteAP then ran to a trunk switch and fried half of it's ports.

The idea of a disconnected and/or solar powered lab grow, and my first idea is to build a separate phase for electronics and led lighting for the house. The last years total dailyenergy consumption was of 9.5 kwh, it is so efficient.

In my are is not easy to get used laptop/ebike cells, tough theycan be gotten from people in other areas that recycle and resell them. Although risky, I think.

So, do you mind if I ask you some recommendations to start?

For the battery modules, I thought of making 13s5-8p so to stay light and in a wide-spread format, but now I read that 14s is recommended and that the general size is so much much larger.
Is not better to have 48v small modules that can be inserted or removed independently?
Why 14s and not 13s? And what parallel size?

I prefer directly solder fuses on cells vs nikel bars, but I don't know how to design it to a 14s5p format that is usually seen on chinese frames. Any suggestion?

BMS on every module?

What batteries do you recommend? The ones I initially selected have proved to be unreliable with the years.
I cannot post links so what about NCR18650A from NKON?
And those Liitokala NCR18650B from ali are any good?

I also have questions about what's the desired inverter and charger system, but I could wait until I have some batteries already made. Logically I would want them to have some sort of connection for data logging and controlling. I already have a domotics (node-red based) andlogging system with TSDBs

Thanks in advance.
Sergio.

Welcome!

>So, do you mind if I ask you some recommendations to start?
I don't see your location, but in US I use these 3 sources to buy cells:
- BatteryHookup -https://batteryhookup.com/
- Power2Spare -https://www.power2spare.net/collections/all
- Battery Clearing House -https://www.batteryclearinghouse.com/collections/all

>Why 14s and not 13s?
The reason for 48v is due to range of equipment (and lower cost) and manageablewire sizes and many things. 14s = widest range of equipment. 13s = less choices but doable.
48v is alsobest suited for larger power situations - like running shop tools or ahome. If you're just camping/charging iPhones - then 12v is OK.

[size=small]>And what parallel size?[/size]
[size=small]You need to figure out how much power you want to produce. Then the rest can be discussed.[/size]

[size=small][size=small]>I prefer directly solder fuses on cells vs nikel bars, but I don't know how to design it to a 14s5p format that is usually seen on chinese frames. Any suggestion?[/size][/size]
[size=small][size=small][size=small]>BMS on every module?[/size][/size][/size]
[size=small]Watch some youtubes / start getting some info - @HBPowerwall @DIY Tech & Repairs @AveRage Joe @DavidPoz @LithiumSolar @jehugarcia - all have good info.[/size]

Good luck on your efforts

Thank you. I'm in North West of Spain. Is not the best location of the country, but this area as it's own climate.
I'll have more problems finding a good location for the panels, as the house occupies all the south and the roof is e-w oriented.

14s is more suited for normal 48V range. Lithium is meassured in nominalvoltage and la is on min voltage there fore the confusion what 48V is compare to Lithium 14s.....

Charging from grid is just costly. The cost saving most be enormous. I would say 4x...

Ac -> Battery -> AC you looseup to or more than 30% in energy. You also need to get the gear for it and all that. Its alot better to use solar directly. Feel free to calculate the ROI doing AC charging during low price hours.

Welcome btw You can for instance look at my system

Also last thing. Dont start to small... 14s6p is like nothing. You cant power much with that to save money. Also think twice before buying. To many people make the mistake starting to buy things just because and end up with trying to do bad sollutions with them

Thanks Daromer for your tips. While I don't completely understand your first statement on 14s, but I'm starting to see that adding 1s for slightly more voltage aims for the equipment used, not the pack itself.
In fact, when I was thinking on making 14s8p modules, I was planning to run a big number of them in parallel, for the same 10kwh (for example) total capacity. I thought that was better to have "cells-of cells" if that makes sense. So they could be better managed by BMSs and could be hot-swappable.
But as I read more, it seems preferred to have large quantities of single cells in parallel, to reduce the effect of differences in the individual cells and dampen one cell going bad. But with the setups seen, to repair a pack, you must pull all the battery bank offline. So people always use more than one bank from the start.

My current aim for my first bank is 14s80p up to 14s100p. I found a supplier for recycled high mah/high % cells, and it all depends on price.
I have plenty of experience and I'm used to build my own Iot devices, so I'll try to build a diyBMS and integrate it to my automation system.
What do you think about this plan?

There's a known repaired panels supplier that also carries inverters so I'll call him.

I'm only afraid that this could be something that I'm not able to build. I've tried so many things in my life and not always I had been up to the task. That could be another one.

daromer said:

To many people make the mistake starting to buy things just because and end up with trying to do bad sollutions with them

Click to expand...

That phrase can have different meanings. I hope that you don't mean that nowadays building those systems are not redeemable unless one works at an ebike repair service shop and get cells for free.

For me, replacing the grid supply or filter it, should be another point. I've already replaced, that I remember, a complete computer, server board, several PSUs, 2 wifi APs (unify), 3 routers (btw, now I have it virtualized), one 28p switch, two UPS, a 55" tv + yamaha decodifier, the garage opener. All fried. The last winter, we were without supply as the company meter blown itself. They had to bridge it to give us current. (It's a disaster)

Because power quality is so bad in your location, this is a good reason to build a powerwall system.

Like daromer suggests, with 18650 cells you want 14s due to the optimum voltage range of the equipment, eg the inverter, chargers etc.

You can build battery packs in medium size modules, see owitte's system:
https://secondlifestorage.com/showthread.php?tid=823

If you charge from the web, your charger will have to be super tough as well.

Have you checked your grounding systems for the house?

48v from lead acid is the min voltage a LEAD acid system have. 13s lithium minimum is more like 39v.....

As you see 13s is way lower.
La max is around 58v. 13s is once again 54.6.

Thats your answer why 14s Suits better.

What i ment is People buy Gear and then suddenly want to expand their off grid inverter adding a grid tie inverter Making the system dangerous and in worst case blow Up...

IF you have bad incoming power you need proper Gear and just getting and inverter and ac based Charger wont be enough. The spikes Will Go through. First off all you need a system that can deal with it or you need the system to be offgrid with isolated charging from ac.

An easy sollution is just to add some.protevtion on incomming Line like voltage and surge.

You sida you replaced Ups systems. Guess what happens to the solar system IF its hooked Up

From what you are saying the best option I would suggest is to buy a cheap used 48V UPS unit (2200VA or 3000VA) and use that for your computer/elecronics equipment and build the battery pack for the UPS to start with. Then buy an inverter after the first year or learning.

Cheap I mean about a 10th the cost of a new hybrid unit

Economically in relation to battery prices :
https://secondlifestorage.com/showthread.php?tid=4737
Unless you can get very very cheap off peak power (or free cells and value your time at zero) then charging off the grid is not economically viable.

"piggyback" inverters I'm assuming you mean grid tie ?
When considering an inverter solution for the rest of the house
https://secondlifestorage.com/showthread.php?tid=8053

In terms of the e-w roof. Not really an issue if your panels are cheap. Buy panels over batteries and see your first winter through (lowest ouput). My panels are E-W and at about 5 degrees (nearly flat), granted winter ouput is appauling but I'm about 1000 miles further north than you.

Work out the real cost of putting 1kWh of power into and out of your planned battery setup and work out how much the value is of your destroyed equipment.

Learn and build.

Thanks guys for all your advice. It's so helpful and I really appreciate it.

@Redpacket I've read through the build you linked and there's plenty of good tricks there. That's I'm currently wanting to build now, but with bigger packs. My initial idea was to make every pack 14s (48v) andwhatever capacity I decided, and then grow. Owitte there is making the all parallel cells packs I've been advised to build, instead.
But if I understand well how it works, he can't really remove a pack without pulling all the "string" (as he names) offline.
And I doubt about the possibility of changing the subsequent added "strings" capacities. That's something that also applies to my future build. If I make now a battery (a shelf like ajw22) 14s80p, f.Ex, could add in parallel another shelf of 14s100p in the future?

About grounding, I made myself the wiring on my house. I followed the regulations and planted two javelins, used O2 free wiring and buried well isolated. My opinion is that the surge is coming from the grid, but could I use some help on diagnosing this problem. The last incidence (the metering board blown) was a complete burn out of the wiring and switch boardforthe neighbor. Aside from those "events" one can frequently see the lights flashing. I was told by the furnace installator to fix that or they would void my warranty, it'srelays where clicking. And we have the most expensive supply from Europe.

@daromer The idea was to selectively going offgrid, but I mixed several phases of my wilings in my explanations. I'll try to build an offgrid system for electronics and lighting, with solar panels. I would make use on some suggestionsoncharging equipment.
I was told that there's no protection for lightning surges. Affordable for a living place, I guess. On my network equipment, I'm trying now to isolate floors by using fiber links instead of copper.

@completelycharged I already been there. But the UPS was 72v unfortunately. Those devices are not designed for continuous duty.My current setup,can handle almost any load but it self disconnectsin less than an hour.

With piggyback inverters I mean those small units that appeared recently, that go installed in the back of the panels and normally they can handle 4 units at the same time. That was interesting for me, as if I have do the install on the back of the house, there will be @20meters to carry the energy to the basement. Doing direct injection and AC charging of the batteries seemed a good idea initially.

How do you carry the juice from the panels to the chargers in long runs?And I mean DC/AC,direct 48v or raise it to prevent losses.

Note: My location is supposedly in the most rainy state of the country. Something like UK, they say. But in practice we have a nicemicroclimate in this valley and we have sun while it rains all around.
I'm so sorry about my english.

Those on back are micro inverters and they are grid tie.

You run high voltage longer distances. My panel arraya are 500+ vdc. It just run multiple wiring

daromer said:

Those on back are micro inverters and they are grid tie.

You run high voltage longer distances. My panel arraya are 500+ vdc. It just run multiple wiring

Click to expand...

Yes, of course. That was my first plan. Also adding protection from the grid supply and build a dump controller. That before knowing if they work without a frequency feed.

And how you raise the potential, simply mounting panels in series? And then the charger must support all this voltage or you insert a step down device?


Mmmm, not convinced on this setup.

Panels in series. My system have MPPT that range 350-950VDC so thats not a problem.

My chargers on other hand is max 140VDC so for those i have many wires coming down from the roof.

daromer said:

Panels in series. My system have MPPT that range 350-950VDC so thats not a problem.

My chargers on other hand is max 140VDC so for those i have many wires coming down from the roof.

Click to expand...

What inverter rig would you recommend me?

I have a top avgdaily consumption of 9,5kwh
I'm planning to build a 12,5kwh first battery (14s100p 2,4Ah cells)
and 10-12 x 330w panels as the first batch.

I'm trying to find whichinverter suits me as a first unit, but by now I'm already dizzy.

My goals are the self production of energy, improve energy quality and avoid the frequent dropouts. And having an example installation for developing monitoring and Iot devices. Perhapssupport for ev chargingin a medium term (that's a futurible, though)

I suppose that I need an hybrid device, zero-injection (as in my country not only you are not paid for the energy you serve, but you have to pay a fee) that has a high input voltage, for remote panels, and just few minutes ago I've been said that not all inverters allow charging Lithium batteries :-/

I'll try to learn a bit more so I can understand all advices you give me.

You should go with offgrid then. Then you cant feed back to grid.

What you need depends on what you can oau. Victron?

Well, I was not right saying that here the energy injected is not paid. It is, but at 0,01cts per kw. Depending on your tariff that could be a 1/4 the price of the consumption. And half of the total amount are fees that you cannot compensate.

I'm still struggling to find the inverter suitable for me.
@daromer, yours is a connected one, isn't it? And how can you connect other devices in parallel? I've been said that this is not possible without a paralellizable system.

I run a grid tie hybrid system. Grid tie systems can have as many paralell systems as you want on the grid Side.
On the load Side the inverter must be capable of being paralelled and most of them have an Interface where they hook each other together for it to work. Dont try to parallel systema not ment for it.

So I almost have the whole systemdesigned. I'll get a Victron Multiplus 48/5000 and a Victron regulator.
But I have problems deciding what regulator it's best suited for my PV specs.
I've drastically reduced the distance to the panels (less than 6m) by designing a front porch strip, so ditched the 7s2p for a 2s7p.
The problem is that the numbers don't match the Victron chargers. Here are my calculations:




It seemed to me that the 150/70 was short in amperage and power. I'm not completely sure as those watts are theoretical... but I created a new 3s5p configuration. Now the voltage is higher, so even the panels being closer, there is more tolerance in wiring, and I could have misunderstood this, but I think that the mppt will start to follow earlier if the voltage is closer to the end margin (specs say until 53v).
Watts are even more out of spec for the 150/70, but the 150/85 seems a better fit now. But I think it's oversized in intensity.

What should I choose?

On the other hand, the 3s5p leaves one panel isolated in a new row. I don't know if it will look strange.

I have similar Victron gear here & am happy with it.
Looks like you need two MPPT controllers, not one, ie connect half the panels to one, the rest to the other.
I have three to minimize effects of shade & lower current from my 7.8kW solar array.

Re the batteries, build them in modular blocks:
- it's a tried & proven method,
- bad ones can be swapped out,
- you can grow capacity easily &
- it's easier to monitor & balance.

You will need a BMS