I'm considering my options for my first real system. 7 kWh.
My 'needs' (freezer, lights, fans, misc) are about 2kWh
My 'wants' (fridge, coffee, pc, tv, clothes washer, toaster oven) come to about 5kWh.
At 50% DoD, with 2 days of autonomy I figure I'll need approximately 28kWh (7x4) of batteries. Both the fridge and freezer will run on DC.
Panels: (2kW = 8 250w) / 4 hours insolation)
Here is where the crazy starts.
I was wondering if I could not run 2 separate battery systems / circuits - one SLA and one LifePO4.
SLA 12V 800Ah =~ 10kWh = Needs
LFP 24V 800Ah =~ 20kWh = Wants
Why?
To take advantage of the strengths and weaknesses of each battery type and the context in which the loads will run:
Needs / Wants
- low / high voltage
- consistent / intermittent
- predictable / unpredictable
SLA strengths
- Cost
- History
- Predictable
SLA weakness
- Maintenance - need to be 'topped off' regularly
- Peukert
LFP strengths
- No need to be 'topped off' regularly
- Not as much effected by heavier loads
LFP weakness
- Cost more
- Not as much history
- More hardware (bms)
Each's strengths and weaknesses are pretty much inverted, as are my needs/wants.
That is, my needs are predictable and consistent and my wants are unpredictable with potentially high current.
The problem (among many?) of course is my solar controller (Outback?) will have to charge both or I'll need 2 controllers with a (hopefully automatic) switch/relay.
Or, maybe I can run the 'overflow' to an LFP charger?
One of the things I find appealing about this strategy is that my SLAs will have priority so they will _more_ regularly get fully charged (as opposed to thy entire system being SLA - the panels will effectively be oversized for them). Whenever the SLAs are topped off it will start the LFPs charging, which I don't care as much about getting topped off. When I need to run some high voltage utility I can just make sure the SoC of the LFPs are OK without worrying about the SLA.
So, what do you think, crazy?
PS, Admins: I got an error while posting: "Missing human verification information." I am not an animal! I think the session timeout could be increased and perhaps a more helpful error.
PSS: Followed by "Empty response". Haha, I used to be a sw developer, that's why I got out :P
My 'needs' (freezer, lights, fans, misc) are about 2kWh
My 'wants' (fridge, coffee, pc, tv, clothes washer, toaster oven) come to about 5kWh.
At 50% DoD, with 2 days of autonomy I figure I'll need approximately 28kWh (7x4) of batteries. Both the fridge and freezer will run on DC.
Panels: (2kW = 8 250w) / 4 hours insolation)
Here is where the crazy starts.
I was wondering if I could not run 2 separate battery systems / circuits - one SLA and one LifePO4.
SLA 12V 800Ah =~ 10kWh = Needs
LFP 24V 800Ah =~ 20kWh = Wants
Why?
To take advantage of the strengths and weaknesses of each battery type and the context in which the loads will run:
Needs / Wants
- low / high voltage
- consistent / intermittent
- predictable / unpredictable
SLA strengths
- Cost
- History
- Predictable
SLA weakness
- Maintenance - need to be 'topped off' regularly
- Peukert
LFP strengths
- No need to be 'topped off' regularly
- Not as much effected by heavier loads
LFP weakness
- Cost more
- Not as much history
- More hardware (bms)
Each's strengths and weaknesses are pretty much inverted, as are my needs/wants.
That is, my needs are predictable and consistent and my wants are unpredictable with potentially high current.
The problem (among many?) of course is my solar controller (Outback?) will have to charge both or I'll need 2 controllers with a (hopefully automatic) switch/relay.
Or, maybe I can run the 'overflow' to an LFP charger?
One of the things I find appealing about this strategy is that my SLAs will have priority so they will _more_ regularly get fully charged (as opposed to thy entire system being SLA - the panels will effectively be oversized for them). Whenever the SLAs are topped off it will start the LFPs charging, which I don't care as much about getting topped off. When I need to run some high voltage utility I can just make sure the SoC of the LFPs are OK without worrying about the SLA.
So, what do you think, crazy?
PS, Admins: I got an error while posting: "Missing human verification information." I am not an animal! I think the session timeout could be increased and perhaps a more helpful error.
PSS: Followed by "Empty response". Haha, I used to be a sw developer, that's why I got out :P
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