Add-on DIY portable power station? Charging options? Better ideas?

[pantechlife]

I'm exploring options for a small (50 > 100ah'ish) likely DIY portable power station.

My main house batts are 2 x 200Ah 12V LiFePO4 batteries charged from 740w 24v (residential) panels via Renogy ROVER 60a MPPT. The idea is to add AH juice for the consistent loads day to day, while also getting a portable power unit that I can ideally carry, over wheel, with me to video shoots.

I understand this plan would be moot if A. I was working within consistent sunshine hours (I aint), or B. Don't need portable power (I do), given A+B this plan makes sense (till I'm directed elsewhere), and would hopefully add an effective ~100ah to my setup.

Looking for advice re: best practices for this.

The office gear I'll run as much as possible off 12V adapted devices (buck converters, boosters, and USB-C), yet for errant low-load items (ext monitor, digital devices, chargers that I can't adapt) I'll need 240V Australian outlets. It would be cool if I could either plug-in all these doodads to this station to get a full day out of it, sitting under desk, maybe.

My hope is that it'd be possible to use this station as an 'overflow' of my 400ah juice, and drain it first (then charge it when main batts are full, or when I might need to via a manual switch).

Yet I am a noob and defer to all yee wise and faithful.

 

[MisterSandals]

It would be cool if I could either plug-in all these doodads to this station to get a full day out of it, sitting under desk, maybe.

Have you done an energy audit of the things you expect to power?

The batteries you mention:
2 x 200Ah x 12.8V nominal = 5120Wh
100Ah x 12.8V nominal = 1280Wh

6400Wh total

How many watts and how many hours each day do your doodads use?
for example:
laptop 120W x 5h = 600Wh

For solar:
6400Wh / 740W solar = 8.64h from empty operating at 100%

You need to find your daily Wh used as your next step.

 

[pantechlife]

Have you done an energy audit of the things you expect to power?

Hey, thanks and yes I had and should have mentioned, I had factored on a sheet where I overestimated to ~2.5kw.

My energy needs have greatly reduced from original factoring, and office now consists of a macbook air m1, ext monitor and modem ~90% of the time. A LOT less power.

I just downloaded the one in yr sig, imported to Google Sheets (white 'user input' labelled cells make little sense?): https://docs.google.com/spreadsheets/d/1_zmBeMb-wRMM-2Qg6f4eFDXj4obiqSG7e0Ppt187PPY/edit?usp=sharing

Though informed refactoring is needed, it has been accurately done prior, which informed the 400ah purchase - which is now what I got and will need to make do with.

 

[MisterSandals]

I had factored on a sheet where I overestimated to ~2.5kw.

The spreadsheet shows 2.5kW (a rate) as the inverter load?

3918Wh (3.9kWh, an amount) as your daily use

Everything in the spreadsheet looks reasonable. I wouldn't expect as much solar production as indicated in the spreadsheet. Running a Renogy at 100% will likely result in longevity issues. A better and bigger SCC might be a good investment.

EDIT: 300W water heater?

 

[Brucey]

Perhaps something like a Redodo mini 12V 100Ah paired with a Victron Phoenix 12/800 or 12/1200? Could connect it to your existing bank for charging, use Anderson connectors for quick disconnect when you need to go mobile.

 

[Brucey]

I think in Australia you may be able to get a multiplus 1600 which is an inverter/charger.

 

[pantechlife]

I think in Australia you may be able to get a multiplus 1600 which is an inverter/charger.

Wo, we're getting into crazy talk territory .

I'm talking re a budget, light, portable DIY station, with an inverter for low power devices.

I'll likely test my 150watt pure sine inverter I have on hand, that's worked fine for laptop et al prior, and on googling just now something like a LiTime 50ah batt, and upgrade when/if needed.

 

[pantechlife]

The spreadsheet shows 2.5kW (a rate) as the inverter load?

I meant as total AC/DC use.

I just re-uploaded the original spreadsheet, it (read: I) borked the prior:

Its A Beastie - Energy Audit_Rev B

Mobile (AC & DC Loads) 1 2 System Load (Energy Audit),3 Item,Description,Number of devices,Watts,Extra Surge Watts **,Hours/day,Runs off DC (Blank=no),Total Watts,Total Extra Surge Watts,Total Watt-Hrs,AC Loads,DC Loads,4, System size calculations, User input,User input,User input,User input,Us...

docs.google.com

3918Wh (3.9kWh, an amount) as your daily use

This is 'full load watt hours'?

Everything in the spreadsheet looks reasonable. I wouldn't expect as much solar production as indicated in the spreadsheet. Running a Renogy at 100% will likely result in longevity issues. A better and bigger SCC might be a good investment.

I'm taking SCC as: MPPT.
Yr not thinking of the 20-40A models are you? I actually upgraded to the Renogy Rover - 60a model , after realising my prior 60a 24v wasn't enough to handle my panels.

EDIT: 300W water heater?

That's what it says :
Rated Capacity: 10 Litre. Rated Voltage: 12 Volt (25 Amp, 300 Watt ) and/or 240v (4.2Amp , 1000Watt) - Duoetto 10Lt Hot Water Heater .
Obvs only turned on when needed, and heats fast.

 

[pantechlife]

A key question is - what do I need to charge this thing, from the 400ah 12v circuit?
I.e. 400ah reaches full charge, auto charges the station.
A switch gives option to manually charge the station.

Just 1 battery so assume dont need BMS, but how would I control these charges/avoid over/under charging?
Do all 50a lifepo4 have a built in BMS for such things? Looking at this one

 

[MisterSandals]

This is 'full load watt hours'?

No, its the total use of all your projected use per day. Watts x hours = Wh.

I'm taking SCC as: MPPT.

Solar charge controller (not necessarily MPPT)

Yr not thinking of the 20-40A models are you? I actually upgraded to the Renogy Rover - 60a model , after realising my prior 60a 24v wasn't enough to handle my panels.

Sorry, you're right. 60A SCC will be plenty.

I've gone astray from your original question. I'n not sure how to automate or even share power between your 2 battery systems without continual manual intervention.

Did you buy the Renogy already? There are very good SCCs for not much more.

 

[pantechlife]

Solar charge controller (not necessarily MPPT)

But why on would u not MPPT?

Sorry, you're right. 60A SCC will be plenty.

I've gone astray from your original question. I'n not sure how to automate or even share power between your 2 battery systems without continual manual intervention.

Neither am I!

Did you buy the Renogy already? There are very good SCCs for not much more.

I have bought, unopened.

What would another give me that the Renogy doesn't?
Note that I'm in Oz, with less options than US, Renogy actually have a relatively good reputation here, I.e. can (and have) returned, do [eventually] get warranty honoured, etc.

 

[MisterSandals]

But why on would u not MPPT?

Cheap little utility battery for camping or whatever at $10. I have a few.
All my serious SCCs are MPPT.

740W / 28V = 28A

I’d get a Victron 100/30 with Bluetooth in a heartbeat.

 

[pantechlife]

I’d get a Victron 100/30 with Bluetooth in a heartbeat.

I would too, but based on prior advice I was told I needed over 24v MPPT, and bought the Rover 60a on recommendation (also factoring for adding more in future).

LR4-60HPH-370M
2 x 370w 24v
EACH:
Current at maximum power ( IMP/A ),
STC: 10.76 | NOCT: 8.63
Short Circuit Current:
STC: 11.52 | NOCT: 9.32
Maximum Series Fuse Rating: 20a

 

[pantechlife]

@MisterSandals To charge whatever external battery/station don't I just need a Voltage Sensing Relay (VSR) or Smart Relay, and a switch?

Seems the above got off-topic and overthunked, mayhap.

 

[MisterSandals]

To charge whatever external battery/station don't I just need a Voltage Sensing Relay (VSR) or Smart Relay, and a switch?

How would you get this relay to do what you originally asked?

My hope is that it'd be possible to use this station as an 'overflow' of my 400ah juice, and drain it first (then charge it when main batts are full, or when I might need to via a manual switch).

 

[pantechlife]

How would you get this relay to do what you originally asked?

Isnt this exactly what it does?

I've realised I actually have a Redarc Dual Battery Isolator SBI12 in my box of inherited doodads, from what I'm reading this can be attached/between/wherevs my 400ah and auxillary and when 400ah reaches charge ( 13.2 volts for activation, 12.7 volts for deactivation) it will then charge/connect flow to my auxillary batt.

The switch could bypass the SBI12 to allow flow.