Home System - Getting It Started

[Hedges]

(4) 12V - 100 ah batteries in series holds and delivers same power as (4) 12V - 100 ah batteries in parallel.
But it does it with smaller gauge wire, fewer FETs, greater inverter efficiency.


No extra $$ for same storage. That's what you're missing.

 

[HARG Hunter]

(4) 12V - 100 ah batteries in series holds and delivers same power as (4) 12V - 100 ah batteries in parallel.
But it does it with smaller gauge wire, fewer FETs, greater inverter efficiency.


No extra $$ for same storage. That's what you're missing.

That's where I should calculate for Watt hours instead of Amp Hours right? I think that's what I missed.
So I'm still going to get 4800 Watt Hours out of that bank from 1 cycle correct?

 

[MrM1]

To get to 48v from 4 12v batteries you'd wire them in series and yes you'd have a 100ah 48v bank

4 12v batteries wired in parallel would give you a 400Ah bank.

Here's the catch
12v x 400Ah = 4800 wh
48v x 100Ah = ... Wait for it ... 4800wh.

It's also my opinion that series connections preform better than parallel connections if your 12v battery is cell allows it.

 

[Nobodybusiness]

I've been looking at that.
Wouldn't it be a helluva lot more expensive for my battery bank then?
(4) 12v - 100ah batteries only get me 100ah if I wire them in parallel to get to 48v.

(4) 12v - 100ah batteries would get me 400ah if I leave them at 12v.

Just wondering if the gain in 48v would make up for the cost. I'd be looking at an additional $3000 to achieve the same storage, or am I missing something?

Not sure if you are making your own batteries or buying 12v batteries. Normally premade batteries don’t allow series connection to make 48 v because each have a BMS.

A 12v 100ah battery only gives you 1.3KWH storage.

16x3.2v 280ah cells is 48v and 15KWH storage and cost $2200 if you make it yourself which is not hard.

Let’s say you have a 5000 watt inverter.
With a 12v battery you are pulling 416 amps and thats not even taking in the inefficiency of the inverters.

At 48v if using one battery it would be 104 amps.

A hell of a lot less copper and lower amperage.

If it’s a stationary setup it’s always better to go with the higher voltage.


Therefore if we take your example 4x12v in series @ 100ah = 48v@100ah or 5400WH

Or

4x12v @100ah in parallel is 12v400AH or 5400WH.

Same capacity but significantly lower amperage at 48v.

If this is not clear let me know.

 

[Nobodybusiness]

(4) 12V - 100 ah batteries in series holds and delivers same power as (4) 12V - 100 ah batteries in parallel.
But it does it with smaller gauge wire, fewer FETs, greater inverter efficiency.


No extra $$ for same storage. That's what you're missing.

Well said. I got a little long winded on mine trying to show it with math.

 

[Steve_S]

12V/100AH = 1,280Wh/1.2kWh 4x100AH cells -4S BMS
24V/100AH = 2,560Wh/2.5kWh 8x100AH cells -8S BMS
48V/100AH = 5,120Wh/5.12kWh 16x100AH cells -16S BMS

120V/10A draw =1200W. 12V@100A=1200W, or 24V/50A =1200W, or 48V/25A=1200W (Uncorrected for inverter inefficiency)

With Batteries in Parallel to make up a bank, each battery CAN act as "Last Man Standing" providing fault tolerance / fail over should any or all other packs cut off for any reason, each pack can be configured to operate "stand alone" thereby keeping you up & running.

COSTS: Note that the 12V 200W panels cost MORE than 24V 250W+ Panels and if you can access places like Santan Solar the deals to be had are incredible. The SCC can take say 200V it does not care if from 12V, 24, 50V Panels. But less panel = less wire, racking, breakers/fuses and simpler combining. It is never the $1000 thing that hits ya, it's the piles of $10, $20 & $50 thingamabobs that do it.

The BIGGY: Like a House the Foundation that it's built on has to be solid and support the structure. Battery System is a "Foundation" component. So build for YOUR TARGET and not the interim which will have to be redone & updated. IF you know that you will want 240VAC/100A Service which requires 24,000W + Overhead then you clearly need to build 48V (48V@250A=12,000W). To get 24kw to the main panel would require Paralleled 12kw Inverters.

Also remember, We can now easily get 304AH Cells which are ideal for Energy Storage Systems so you can build a "Native" xxV/300AH battery pack. 280AH cells weight 5.1kg, 304AH cells weigh 5.6kg. These can get quite heavy quickly, so that is also another thing to consider.

The tough nut to crack... Yes a 12V battery is cheaper per unit at first blush BUT consider the amps it has to push out to deliver the wattage demanded that is where it crosses the line. Higher voltage = less amps to deliver wattage and easier on the gear etc...

 

[HARG Hunter]

To get to 48v from 4 12v batteries you'd wire them in series and yes you'd have a 100ah 48v bank

4 12v batteries wired in parallel would give you a 400Ah bank.

Here's the catch
12v x 400Ah = 4800 wh
48v x 100Ah = ... Wait for it ... 4800wh.

It's also my opinion that series connections preform better than parallel connections if your 12v battery is cell allows it.

That's the lightbulb that went off for me after I re-read everyone's replies.
Since my current cabin system is only 12v, I've always had Amp Hours stuck in my head as the only thing that matters.
I need to change my thought process to watt hours instead.

Thanks

 

[HARG Hunter]

12V/100AH = 1,280Wh/1.2kWh 4x100AH cells -4S BMS
24V/100AH = 2,560Wh/2.5kWh 8x100AH cells -8S BMS
48V/100AH = 5,120Wh/5.12kWh 16x100AH cells -16S BMS

120V/10A draw =1200W. 12V@100A=1200W, or 24V/50A =1200W, or 48V/25A=1200W (Uncorrected for inverter inefficiency)

With Batteries in Parallel to make up a bank, each battery CAN act as "Last Man Standing" providing fault tolerance / fail over should any or all other packs cut off for any reason, each pack can be configured to operate "stand alone" thereby keeping you up & running.

COSTS: Note that the 12V 200W panels cost MORE than 24V 250W+ Panels and if you can access places like Santan Solar the deals to be had are incredible. The SCC can take say 200V it does not care if from 12V, 24, 50V Panels. But less panel = less wire, racking, breakers/fuses and simpler combining. It is never the $1000 thing that hits ya, it's the piles of $10, $20 & $50 thingamabobs that do it.

The BIGGY: Like a House the Foundation that it's built on has to be solid and support the structure. Battery System is a "Foundation" component. So build for YOUR TARGET and not the interim which will have to be redone & updated. IF you know that you will want 240VAC/100A Service which requires 24,000W + Overhead then you clearly need to build 48V (48V@250A=12,000W). To get 24kw to the main panel would require Paralleled 12kw Inverters.

Also remember, We can now easily get 304AH Cells which are ideal for Energy Storage Systems so you can build a "Native" xxV/300AH battery pack. 280AH cells weight 5.1kg, 304AH cells weigh 5.6kg. These can get quite heavy quickly, so that is also another thing to consider.

The tough nut to crack... Yes a 12V battery is cheaper per unit at first blush BUT consider the amps it has to push out to deliver the wattage demanded that is where it crosses the line. Higher voltage = less amps to deliver wattage and easier on the gear etc...

I definitely plan to grow this system over time, so 48v is the way to go for sure.
I will probably start with (4) 12v/100ah CHINS and wire them in series to get my pack to 48v.
Not quite comfortable with my skills even watching Will on Youtube building packs with raw cells.
After I get this set up, I may go the build-your-own route when I decide to grow the system, as I would have to have a balanced bank any way.

Thanks for the heads up on the 24v panels. I do have access to SanTan (I am in Wisconsin, but even the cost of shipping from them is only $200+ for a pallet of panels, so it's cheaper for me to buy panels from them even with added shipping costs compared to others). I will probably buy a full pallet which will provide me with the panels I need in the future.

 

[HARG Hunter]

This is now what I'm thinking:

* 48v All-In-One (Still looking at Options between Growatt, PowMr, Renogy etc...) Probably 3000-5000 range Inverter
*(4) SanTan Solar T Series 250w Panels (37.6 voc, 30.3 vmp)
*(4) CHINS 12v 100ah LifeP04 batteries (Wired in Series)

 

[Hedges]

This is now what I'm thinking:

* 48v All-In-One (Still looking at Options between Growatt, PowMr, Renogy etc...) Probably 3000-5000 range Inverter
*(4) SanTan Solar T Series 250w Panels (37.6 voc, 30.3 vmp)
*(4) CHINS 12v 100ah LifeP04 batteries (Wired in Series)

Make sure the batteries are compatible with wiring in series. That subjects the BMS components to higher voltage than a 12V system would.
Consider 48V battery assemblies, which are also available.

The Santan 250W panels are lower wattage per unit area than some, and likely more degraded.
Panels are a vanishingly small part of system cost. Consider alternate models.

Determine starting surge requirement for motor loads.
Consider no-load power of inverter, matters most for 24/7 operation.

At the higher price and performance end, here is 6kW SMA Sunny Island for $3000.
That plus a Midnight Classic would power just about any 120VAC load.

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[MrM1]

This is now what I'm thinking:

* 48v All-In-One (Still looking at Options between Growatt, PowMr, Renogy etc...) Probably 3000-5000 range Inverter

In my setting, the MPP LV6548 looks real appealing right now

 

[MrM1]

That's the lightbulb that went off for me after I re-read everyone's replies.
Since my current cabin system is only 12v, I've always had Amp Hours stuck in my head as the only thing that matters.
I need to change my thought process to watt hours instead.

Thanks

I made the same mistake 4 years ago thinking I could afford 4 435Ah L16 batteries for a series connection to 24v but could not afford 8 of them for 48v. I failed to calculate the math and could have actually purchased 8 T105 GC 220Ah batteries for 48v and would have been better off for less cost than 4 435Ah L16 batteries.

This error locked me into 24v and now I'm stuck. Oh how I wish I was 48v. Too expensive to change now until something breaks.

 

[HARG Hunter]

I just went around the house and used my watt meter to measure the consumption of everything I plan to initially hook up to this system.

Question...When I looked into battery backup sump pumps, it got me to thinking...

Am I wrong in thinking I should just run 12v DC sump pumps all the time?
I have 3 sump pumps in my basement right now. Would it be more efficient to just hook them up to this system permanently?
Is the energy usage lower than running standard sump pumps off of my AC?

I'm looking at the Wayne ESP25 12v Back-Up sump pump. Just wondering why it's only considered a back-up vs. primary?
Would the frequent use during certain times of the year just ruin the battery(ies) due to constant running?

 

[HARG Hunter]

Just realized that through my tunnel vision, it wouldn't work within the same system because my battery bank will be 48v. May consider setting up a separate 12v system just for sump pump...hmmmm...has my wheels turning.

 

[GLC]

Just realized that through my tunnel vision, it wouldn't work within the same system because my battery bank will be 48v. May consider setting up a separate 12v system just for sump pump...hmmmm...has my wheels turning.

Why not a 110 sump pump?

 

[Hedges]

48V to 12V DC/DC.

Is 12V pump brush type or brushless? Some may be fairly short life.
Induction motors are long life, although starting cycle can be stressful. My larger motors have centrifugal switch for starting windings, but not the sump pumps. Induction motors are reasonably efficient. DC motors may be more efficient. Higher RPM packs more power in smaller package. Induction motor has VA consumption higher than actual watts, possibly more of an issue for inverters than the grid.
The sump pumps I've lost became plugged and stalled; must not have good protection and overheated windings.

 

[HARG Hunter]

OK...I think I have finally come up with my final design. Just want everyone to give me feedback:

Growatt 48v SPF 3000TL
(8) 230w Panels (SST) - 2 Strings (4 Panels in Series on each String)
(4) CHINS LifeP04 - 12v 100ah Batteries (Wired in Series for 48v)

This should do it right?
Panels are 29.8v VOC, so 4 of them in series per string would be a combined 119.2v max (Growatt handles 145 max)

Am I missing anything?

 

[Bluedog225]

You might want to look at 48 volt batteries. Others will know better than me. I recall some mild preference for not piecing together 12 volt batteries to get to 48.

Edit: something like this. Some supply problems for a bit. Should sort itself out. Deal with this seller at your own risk.

https://www.signaturesolar.com/products/48v-100ah-lifepower4-battery-by-eg4

 

[MrM1]

Can the Chins be wired 4 in series? Some brands can, some can't, some have exceptions

 

[HARG Hunter]

Can the Chins be wired 4 in series? Some brands can, some can't, some have exceptions

The rep selling them on this sight says I can.