Best back up battery solution for first 24 hours of Hurricane?

[BeanAnimal]

Hi Bean,

What type of battery would you recommend for extended backup? TIA

In my previous tank I had large (huge, could barely move them) deep cycle 12v batteries, but tech has changed a lot.

Hi Randy,


Total wattage of the equipment you want to backup and for how long?

Are you looking for something that you can plug into when needed, or something that is always inline and ready to go?


As for battery tech: Lead Acid is still very viable and safe, but you are correct, the tech has changed a lot.

A few general thoughts:

LiFePO4 vs Lead Acid

Characteristic	LiFePO4	Lead Acid
Lifespan (recharge cycles)	2500	400
Relative Weight per storage	1	3
Power Output	Stable voltage over large discharge span	Voltage drops faster as cells discharge
Discharge Depth	Little harm in 80% discharge	Frequent discharge below 50% can degrade cells
Charge Rate	Faster than lead acid	Slower than LiFePO4
Self Discharge	Lower than lead acid	Faster than LiFePO4
Upfront Cost	High	Low
Charging	**Complex Battery Management	Simple and safe
Overall Safety	Dangerous if mismanaged	Extremely Safe, especially AGM types that do no off gas.

If you consider most of the general traits, they don't mean much for a standby battery system that is hopefully rarely discharged. Charge rates, weight, lifespan (total charge cycles), etc. are all fairly irrelevant.

Even discharge depth and voltage stability are not significantly relevant in terms of the rare full discharge during an outage. Both will provide similar runtime. If these were regularly getting discharged the LifePO4 would live a much longer life and/or the lead acid would need to be sized to only discharge about 50%.

So, In the end the biggest difference is going to be overall cost and safety.

**Safety. As mentioned on the prior post (and you likely already know) Lithium cells can fail catastrophically if punctured or overcharged, flooded, with water, etc. Of all of the current Lithium formulations LiFePO4 has a better thermal runaway profile and tends to smoke more than it does create flames (as long as other combustibles are not present).

High quality cells and battery management are an absolute must. As I mentioned in the prior thread, most of raw cells you will find are EV seconds and of lower quality. A lot of it is pure garbage being rebadged and sold on Amazon and dozens of other "battery" type sites.

So that brings us to actual advice

1 - I would stay away from a DIY LifePO4 setup where you buy LiFePO4 batteries and BMS and put it together yourself. If this is something you want to do, then I would stick with US made batteries and BMS like those from Battle Born, Relion or Bioenno.

2 - If you are going to do a DIY inverter and some cells, stick with AGM type cells and a well regarded charger and inverter. There are too many brands to list.

3 - If you do decide to go with LiFeP04, buy a name brand "battery generator", preferably (again) with US made or assembled components. https://lionenergy.com/ is one of the better companies.

I know that EcoFlow, Jackery and DJI have a large followings. I would not trust any of those to be plugged in unattended in my home, period.

That brings us full circle to the original questions. For most reasonable power loads where you want automatic backup power, I would still simply go with an AGM based true sine wave UPS with expansion batteries to get you the runtime that you need. APC, Liebert, Tripp-Lite, even CyberPower. Safe and reliable and time tested. LiFePO4 UPS system are around, but expensive.

If you want more the of "generator" type setup where you can plug things into during and outage, then Lion Energy is a good choice, peace of mind. If you are willing to babysit while in use, then EcoFlow, Jackery or DJI.

 

[Randy Holmes-Farley]

Thanks very much. I'd be looking at low demand (say, 10-50 watts) of in tank flow for several days. Automatic on when power drops. Might not need an inverter at all for some systems, such as Vortech.

 

[VintageReefer]

Hi Bean,

What type of battery would you recommend for extended backup? TIA

In my previous tank I had large (huge, could barely move them) deep cycle 12v batteries, but tech has changed a lot.

I’m not Bean and don’t claim to be but I have been following the Lipo battery station market for years and have many brands and types, and the current tech has prices that have dropped over the years and performance that has increased

You probably want something with built in ups and pass through charging - this functions like the old computer ups stations but with the newer lipo tech.

They have a 8-10 year lifespan before the battery is reduced to approx 80% capacity

They can rapid recharge in as little as an hour

Full consistent power/voltage output

Built in battery management software - it will monitor each individual cells health and adjust charging appropriately

Lcd readout of watts being used, and eta until battery runs out

Built in sine wave inverter and cooling fans, thermal management

Form factor package


What you need to do to spec one, is determine your running watts, and the number of hours you would like the power station to last

These are rated in watt hours - which literally is watts over time

The unit itself will not be 100% efficient - some power is lost from running the station - the screen, the inverter, the fan, etc. we generally assume a 15% loss from watt hours to running the station, some brands are more / less efficient. 15% is a good average though.

A medium sized and priced unit is around 1000 watt hours.
The runtime formula is

Station watt hours (WH) x .85 efficiency / running watt load (w)

Example. My example from real life on my 75g reef with my power station

I have a Big Blue CellPowa 600. It’s 537.5 WH. My return pump consumes 15 watts (a dc 1000gph running at 40%)

(537.5 x .85) / 15 = 30.46 hours runtime

This will auto cutover in .01 seconds in event of a power outage and run on battery seamlessly. When power comes back, even if it’s brief, it will switch to AC power and begin recharging itself.

If I’m home during the outage, I can run my return pump as low as 13 watts and still get proper flow through my system. This decrease watt load and increases battery runtime

(537.5 x .85) / 13 = 35.14 hours runtime

More than enough time for most outages and for me to get some sleep and decide the next day if I need to get out the gas generator.

If your return pump was larger or less efficient, let’s say it pulls 40 watts, then

(537.5 x .85) / 40 = 11.42 hours. A huge difference. My 600wh unit would do fine for normal outages but wouldn’t last long enough for my comfort. I’d be looking at the CellPowa 1000 or 2500

The Cellpowa 600 is $300 but the Cellpowa 1000 is $420 and 1075.2 wh. So $120 more, but double the capacity.

(1075.2 x .85) / 40 = 22.8 hours. That’s the one I would go with

Now I used these formulas using the standard 85% efficiency but in my testing of multiple brands, Big Blue is the most efficient and has a efficiency closer to 90%. So if using this brand consider that the formula estimates are a tad on the conservative side.

I currently have 2x cellpowa 600. I have several other stations, both higher and lower in capacity, and I have to say the cellpowa is my top choice and best performing. It also is mid range in price, less expensive and better performance / runtime compared the big name brands like ecoflow

 

[VintageReefer]

if I had that cellpowa 1000 on my reef and my return pump was dialed back to 30% and using 13w…

(1075.2 x .85) / 13 = 70 hours !!!

If I didn’t dial back and used the normal 15w

(1075.2 x .85) / 15 = 60.9 hours. Still very good and more than plenty.


So what this really comes down to is picking an efficient, dc controllable pump, and a unit with a high enough watt hour capacity, to last what you feel is a comfortable number of hours. The difference between 15w and 50w is huge when it comes to battery power.

 

[VintageReefer]

These also have dc barrel jacks which provide direct dc power bypassing the inverter, which should increase runtime, but I do not have any formula or testing data for that.

 

[Randy Holmes-Farley]

Thanks very much for the info!