Will using an EcoFlow DELTA Max as an EPS shorten its battery life?
November 10, 2023 8:20 PM Subscribe
The EcoFlow DELTA Max can function as an emergency power source ("EPS"), whereby you can leave the unit plugged in all the time and plug other things into it. I set it up as an EPS for a big food freezer in our garage. It works, but what impact will doing this have on the battery life?
In trying to research this, I haven't been able to find a definitive answer. I know that when storing battery backup devices like the DELTA Max for longish periods of time, one should store it at less than 100% charge and also periodically discharge and recharge the battery. But I can't seem to find advice when using it in the EPS mode.
I do note that when the freezer compressor cycles on and off periodically (as compressors do), it seems to cause the EcoFlow to have to recharge itself for a time. This seems strange because the product descriptions say that in EPS mode, power would feed directly to the appliance plugged in – so I would expect that it shouldn't need to recharge the battery. This behavior alone makes me worry that it's shortening the life of the battery.
(The freezer only contains food and not medicine, so it is not critical that we put it on an EPS. I wanted to try this as a leave-and-forget approach to providing backup power for those occasions when we lose power in the area, particularly if a power outage happens when we're not home.)
In trying to research this, I haven't been able to find a definitive answer. I know that when storing battery backup devices like the DELTA Max for longish periods of time, one should store it at less than 100% charge and also periodically discharge and recharge the battery. But I can't seem to find advice when using it in the EPS mode.
I do note that when the freezer compressor cycles on and off periodically (as compressors do), it seems to cause the EcoFlow to have to recharge itself for a time. This seems strange because the product descriptions say that in EPS mode, power would feed directly to the appliance plugged in – so I would expect that it shouldn't need to recharge the battery. This behavior alone makes me worry that it's shortening the life of the battery.
(The freezer only contains food and not medicine, so it is not critical that we put it on an EPS. I wanted to try this as a leave-and-forget approach to providing backup power for those occasions when we lose power in the area, particularly if a power outage happens when we're not home.)
If the battery is at 100%, then you're reducing it's life. Maybe 5-10% capacity per year if it's not hot -- which the electronics might cause, easy to check though. Otherwise, the page says the device is only intended for "casual" usage so I wouldn't be surprised if you have used up it's intended lifespan by now.
posted by flimflam at 7:27 PM on November 11, 2023
posted by flimflam at 7:27 PM on November 11, 2023
This is the simplest rundown I could find outlining what affects the life of lithium batteries.
Short answer to your question is, yes keeping it at 100% continuously will decrease capacity faster than storing it at, say, 40% or 50% or even 80% capacity. Storing at at high temperature can have an equally bad effect - and the two effects, temperature and charge level, add together.
For example, at 0C and 40% charge, the capacity will be at 98% after 1 year. At 0C and 100% charge, capacity will be at 94%. So - some loss but not too bad!
On the other hand, at 25C and 40% charge, capacity will be at 96% after 1 year. At 25C and 100% charge, capacity will be at 80%. So that seems like a much more significant loss.
Other things affect capacity, too - particularly, the number of discharge cycles it goes through. So some of the answer here depends on what you are planning to use the battery bank for. If it will be discharged a few hundred times a year then extra loss by keeping it charged to 100% rather than 50-ish% is a bit ho-hum. On the other hand if you mostly have in mind to use for emergency situations only, maybe it is only slightly discharged 2-3 times a years. And in that case the loss of capacity from keeping it at 100% charge all the time is by far the largest cause of it losing capacity.
Putting it another way, say (Scenario #1) you don't use it for the freezer UPS, keep it mostly charged to 50-ish percent and in storage, and only use it a couple times a year. Then (assuming non-perfect storage etc) let's say it loses 7% capacity each year. After 5 years it will have around 70% of its capacity remaining. (0.93 to the 5th power)
On the contrary, looking at Scenario #2: You leave it plugged in always and in use as the freezer backup power supply. It will lose let's say 17% per year (assuming you can keep it pretty cool in the basement, less than 25C, and so get slightly better than the 20%/year loss of capacity) now you have 40% of the device's capacity remaining at the end of 5 years. (0.83 to the 5th power.)
Under scenario #2, you have an additional advantage that the device is always charged to its full usable capacity whenever the power fails. For that reason, it is a lot more valuable as a back-up/reserve power device for your home - it's always at 100% capacity. Whereas under Scenario #1 it's always at 40-50% discharge and now that the power's out, you can't change that. If this is your purpose, maybe you'd be better off saving $$$ buying a unit that is half as large and keeping that one at 100% charge all the time?
On the other hand, if your main purpose in purchasing the unit it so have remote power say during 3-10 camping trips per year, then yeah you are going to notice that is has quite a lot lower reserve in, say, year 3-8 than if you hadn't kept it plugged in at 100% the whole time.
Two thoughts:
#1. It would be ideal if EcoPower would offer a "UPS saver mode" where the freezer could remain plugged in to the unit and using mains power until the power shuts off - but it would maintain the unit at 80% charged rather than 100% charged. This would be something of a best-case scenario for the use case you are describing.
#2. Either way you are going to get a good 5 years use out of this - and with the way battery technology is going, maybe that is enough?
posted by flug at 7:45 PM on November 11, 2023 [1 favorite]
Short answer to your question is, yes keeping it at 100% continuously will decrease capacity faster than storing it at, say, 40% or 50% or even 80% capacity. Storing at at high temperature can have an equally bad effect - and the two effects, temperature and charge level, add together.
For example, at 0C and 40% charge, the capacity will be at 98% after 1 year. At 0C and 100% charge, capacity will be at 94%. So - some loss but not too bad!
On the other hand, at 25C and 40% charge, capacity will be at 96% after 1 year. At 25C and 100% charge, capacity will be at 80%. So that seems like a much more significant loss.
Other things affect capacity, too - particularly, the number of discharge cycles it goes through. So some of the answer here depends on what you are planning to use the battery bank for. If it will be discharged a few hundred times a year then extra loss by keeping it charged to 100% rather than 50-ish% is a bit ho-hum. On the other hand if you mostly have in mind to use for emergency situations only, maybe it is only slightly discharged 2-3 times a years. And in that case the loss of capacity from keeping it at 100% charge all the time is by far the largest cause of it losing capacity.
Putting it another way, say (Scenario #1) you don't use it for the freezer UPS, keep it mostly charged to 50-ish percent and in storage, and only use it a couple times a year. Then (assuming non-perfect storage etc) let's say it loses 7% capacity each year. After 5 years it will have around 70% of its capacity remaining. (0.93 to the 5th power)
On the contrary, looking at Scenario #2: You leave it plugged in always and in use as the freezer backup power supply. It will lose let's say 17% per year (assuming you can keep it pretty cool in the basement, less than 25C, and so get slightly better than the 20%/year loss of capacity) now you have 40% of the device's capacity remaining at the end of 5 years. (0.83 to the 5th power.)
Under scenario #2, you have an additional advantage that the device is always charged to its full usable capacity whenever the power fails. For that reason, it is a lot more valuable as a back-up/reserve power device for your home - it's always at 100% capacity. Whereas under Scenario #1 it's always at 40-50% discharge and now that the power's out, you can't change that. If this is your purpose, maybe you'd be better off saving $$$ buying a unit that is half as large and keeping that one at 100% charge all the time?
On the other hand, if your main purpose in purchasing the unit it so have remote power say during 3-10 camping trips per year, then yeah you are going to notice that is has quite a lot lower reserve in, say, year 3-8 than if you hadn't kept it plugged in at 100% the whole time.
Two thoughts:
#1. It would be ideal if EcoPower would offer a "UPS saver mode" where the freezer could remain plugged in to the unit and using mains power until the power shuts off - but it would maintain the unit at 80% charged rather than 100% charged. This would be something of a best-case scenario for the use case you are describing.
#2. Either way you are going to get a good 5 years use out of this - and with the way battery technology is going, maybe that is enough?
posted by flug at 7:45 PM on November 11, 2023 [1 favorite]
You are not logged in, either login or create an account to post comments
I’d expect the line voltage your EcoFlow is reading to dip momentarily under the high current demand of compressor startup, but the voltage should come back up when the centrifugal switch in the compressor motor kicks in and the compressor switches from the start windings to the run windings.
If the EcoFlow does come on only briefly, I wouldn’t expect it to need to charge itself back up for very long at all, and if it does recharge over an extended period, I’d first check to see whether the circult the freezer is on could be overloaded and then check to see whether the compressor motor is running on its starter windings (you can usually hear a distinct click when the centrifugal switch actuates).
And then I’d look at the line voltage when it's not under load.
posted by jamjam at 10:34 PM on November 10, 2023