Residential - Sump Pump Backup System

[marty9876]

Little off topic but same principals frequently discussed here - let me know if I should get in trouble for this post

I'm looking to create a battery backup system primarily for a sump pump (finishing my basement) and secondarily for general use as needed for power grid interruptions. Not looking to go full off grid, just to provide me some options to help bridge any gap. Suitcase generator/old solar panels are other tools in the tool bag... or just giving up and going to the sailboat worst case!!!!

Requirements:
- automated failover to battery system for sump pump
- pure sine wave (want to have this be general use)
- some semblance of battery charging profile available (don't murder batteries)
- cycle count on the batteries ironically don't matter at all I think which makes this off (if I get 2 cycles a year that's be high)
- ability to run sump pump for 1 day (guessing 6 hours actual run time, guess it all depends on how much it's raining!). I've got a Kill-A-Watt device I can track usage of current pump but in the end thinking just oversize the snot out of things anyways

Loads

1/2hp Sump Pump 373 W Draw 6 Target hr run time 2238 Total Wh needed Cost$0.00
Freezer 240 W Draw 5.2 Target hr run time 1250 Total Wh needed cost $-

Total loads 613 W Draw 3488 Total Wh needed
Projected runtime 1.5 Days


Inverter -AIMS 1250w Pure Sine 35amp charger w/ 8x profiles $538.00
4x Battery boxes $64.00
Disconnect switch $15.00
Cables/lugs/heat shrink/bus bars $150.00



Batteries - 4x Duracell GC2 6V - 5160- Wh cost of $365.00

Total system cost - $1,123.00 for a DIY 5kWh flooded battery based system more of less... Have tools, crimper and alike from the boat.

Top of mind questions:
- Any reason to up the inverter to Victron or alike? I can't figure out the cost increase justification
- Push myself into a 24v or 48v system? Everything would cost a whole lot more then I image
- Lithium obviously great but cycle count on this is next to nothing, recovery/recharge time not overly critical. DIY lithium not sure I want to try just yet, weight/space is not a issue (furnace room)
- AMG would be nice for completely maintenance free but at 2x the cost, lower capacity to just to never add water to something in my basement seems silly. Plus, with never a cycle on it I'm guessing I'd never need to add water...
- Bigger inverter might be nice but I'm thinking I would augment loads in the day via suitcase generator and this gets us through the night
- Sperate inverter and charger solution? e.g Pro mariner charger and something else for the inverter. My worry is auto failover from a standalone inverter.

Anything you'd change?

[Davidasailor]

While you’re adding the extra parts for redundancy it’s worth considering a DC pump in case the AC one quits. I have a Basement WatchDog (which has its own compromises), but it does have a backup pump and an alarm if it runs.

I agree that this doesn’t seem like a great use for lithium. You don’t need the cycles and even if you do a deep discharge with FLA once or twice a year it’s not as catastrophic as doing it on a routine basis. With the size of your bank compared to the size of your charger you won’t need the extra charge speed capacity of AGM or lithium either.

[marty9876]

Originally Posted by Davidasailor

While you’re adding the extra parts for redundancy it’s worth considering a DC pump in case the AC one quits. I have a Basement WatchDog (which has its own compromises), but it does have a backup pump and an alarm if it runs.

I agree that this doesn’t seem like a great use for lithium. You don’t need the cycles and even if you do a deep discharge with FLA once or twice a year it’s not as catastrophic as doing it on a routine basis. With the size of your bank compared to the size of your charger you won’t need the extra charge speed capacity of AGM or lithium either.

Thanks for the input - I've ruled out the 12v pump option a this time. More or less, I'm taking the approach one great pump (replace existing with new, prosumer grade pump) then put the money into the bank with the goal of the bank being multi-purpose.

In true boat project sense, I think I can scrap the budget... If I every end up needing this to get inspected I'm guessing the inverter needs to be UL/ETL listed or certified. Add ~ $400-$800 to the inverter for that. At a certain point, might as well just get a Victron UL 3000VA 12/3000/120 unit and call it good... at least I can someday unbolt it form the wall and stick it on my sail away boat!