Battery efficiency ratios

[Moped]

Now I have an Ecoflow River 2 and the app I can see precisely how much power each of my devices is drawing from the battery.

Very useful information.

I have noted that there is an 81% efficiency ratio during the power conversion process regardless of whether it is AC or DC.

So a 256wh battery provides 207w of total usable power after efficiency conversion.

Now the question is when using 12v power in a motorhome or camper do the leisure batteries have the same efficiency power loss?

So a 100ah lead acid leisure battery, whilst in theory offering 50ah of power down to a 50% discharge, actually only offers a true 40ah as a result of say an 80% efficiency ration?

And does the same principle apply to lithium batteries supplying power to 12v systems within the motorhome or camper?

Or are efficiency ratios only applicable when using sockets to charge devices with batteries or inverters and not when using the general motorhome systems such as lighting, water pump, heating pumps and fans and so on?

 

[wildebus]

Now I have an Ecoflow River 2 and the app I can see precisely how much power each of my devices is drawing from the battery.

Very useful information.

I have noted that there is an 81% efficiency ratio during the power conversion process regardless of whether it is AC or DC.

So a 256wh battery provides 207w of total usable power after efficiency conversion.

Now the question is when using 12v power in a motorhome or camper do the leisure batteries have the same efficiency power loss?

So a 100ah lead acid leisure battery, whilst in theory offering 50ah of power down to a 50% discharge, actually only offers a true 40ah as a result of say an 80% efficiency ration?

And does the same principle apply to lithium batteries supplying power to 12v systems within the motorhome or camper?

Or are efficiency ratios only applicable when using sockets to charge devices with batteries or inverters and not when using the general motorhome systems such as lighting, water pump, heating pumps and fans and so on?

quick answer ... No

and the 81% conversion ratio sounds pretty poor to boot. It is poor for a DC-AC (Inverter) efficiency and incredibly poor for a DC-DC conversion I would say (especially if the battery in the Ecoflow is a 12V battery and is supplying 12V at the outlet.

When charging, a lead battery will 'waste' around 5% - so if say a solar system is sending in 100W of 'charge' into a Lead Battery, the charge in that battery will increase by around 95W. A Lithium will waste much less - maybe under 1%.
Discharge, I don't think there is any real waste on either as a direct drawing of power, but all devices have an inherent inefficiency so there will be some.
How are you reading how much power you are requesting vs how much power is being actually drawn (i.e. the requested power plus about 20% more on top)?
Never used a Ecoflow so don't know what it tells you, but those numbers sound odd.

 

[Moped]

I am multiplying the power draw shown in the app by the time shown to discharge to 0 watts.

this works out at around 207 for a battery that theoretically holds 254 so 81%. the youtube video uses plug in equipment to measure the total draw down to zero charge and arrives at similar figures. The tester suggested this is about right for solar generator power packs. I suspect batteries with larger capacities have a smaller percentage latent discharge relative to their capacity. for a small power generator this latent discharge will be a relatively higher percentage relative to usable free power.

Bit like the operating system of an tablet taking up quoted memory. if you have massive 256Gb of memory then the 13Gb of an operating system is negligible but if you only have 64Gb of memory it is a large number.

This value may improve with use as the battery and systems "runs in" and settles down so to speak. The calculation above was for a first full charge and use.

basically for any battery as long as you power something with a known and consistent power draw and time how long it takes for that item to stop functioning, you can then work out how much power has been used. Compare this with the capacity of the battery when fully charged and the power used divided by the battery capacity as a percentage is the efficiency ratio.

 

[colinm]

Either the Ecoflow is inefficient, or 256wh is the total battery capacity, and the BMS is limiting charge and discharge to 207wh. I suspect the later, is the biggest part of discrepancy, with just a few wh of loses.

 

[Nabsim]

This isn’t a case of wh and W being muddled is it? I always disliked the way Victron use Wh instead of W, a lot of people think they are buying bigger inverters than they actually are. It seems to be getting more common these days though

 

[wildebus]

I am multiplying the power draw shown in the app by the time shown to discharge to 0 watts.

this works out at around 207 for a battery that theoretically holds 254 so 81%. the youtube video uses plug in equipment to measure the total draw down to zero charge and arrives at similar figures. The tester suggested this is about right for solar generator power packs. I suspect batteries with larger capacities have a smaller percentage latent discharge relative to their capacity. for a small power generator this latent discharge will be a relatively higher percentage relative to usable free power.

Bit like the operating system of an tablet taking up quoted memory. if you have massive 256Gb of memory then the 13Gb of an operating system is negligible but if you only have 64Gb of memory it is a large number.

This value may improve with use as the battery and systems "runs in" and settles down so to speak. The calculation above was for a first full charge and use.

basically for any battery as long as you power something with a known and consistent power draw and time how long it takes for that item to stop functioning, you can then work out how much power has been used. Compare this with the capacity of the battery when fully charged and the power used divided by the battery capacity as a percentage is the efficiency ratio.

All I can say is that when I have done a discharge test, I have setup a constant load and at the end of the test, how much is taken out is the amount of power the battery can deliver.
On Lithiums, I have run that test until the battery cuts out at 0% SOC - and the battery has provided what the makers claim - or actually a touch more so usually around 105Ah on a 100Ah Battery (my current "100Ah" batteries are actually 106Ah), and not 80% of that number.
On Lead, I will do that test but stop when the SOC monitor hits 50% and then see how many Ah have been taken out. Again, it has always tended to match the quoted capacity unless I am specifically testing a problem battery.

 

[Moped]

This isn’t a case of wh and W being muddled is it? I always disliked the way Victron use Wh instead of W, a lot of people think they are buying bigger inverters than they actually are. It seems to be getting more common these days though

Agree that some manufacturers focus their marketing on the size of the inverter output and not the size of the stored power. Example 600w of power great but 300wh battery so you get 30 minutes of 600w power x 85% for efficiency loss = 25 minutes.

But folk think they are getting a 600w battery, which they are not.

Back to the Ecoflow I’m going to do a 0% to 100% recharge as and when it runs out of power. And then see if efficiency improves. The first charge was from the factory default 30% charged which may or may not have been from the U.K. power grid.

 

[Moped]

The battery efficiency is the amount of energy you can take out down to a discharge relative to the amount you can store to a full charge. I’m getting 82% and there are numerous video tests on YouTube indicating that this is around the average value you can expect regardless of solar power station battery size. A slower low powered draw rate and you get slightly more and a higher draw rate and slightly less.

Also worth noting that slower charging is better than fast charging as the battery is cooler when slow charging so you can squeeze a bit more energy into a cooler battery. Rapid charging is great but expect a slightly lower amount of total usable power when discharging. Maybe worthwhile setting the Ecoflow charge rate to a lower setting when mains charging to squeeze a bit more out of it.

Batteries run hotter when undergoing high draw rates and energy is lost through heat. That’s also why it’s better to keep a battery cool which is why many electric batteries in cars have cooling equipment fitted.

Now as for stand alone leisure batteries are concerned, there are videos on YouTube demonstrating that these are not 100% efficient. Again there is loss through heat and conversion losses even with a DC draw and battery management losses. The suggestion is expect 95% with a good quality lithium battery and 85% with a lead acid battery. It may well be that battery manufacturers take this into account when designing a battery and that they overcharge so that they can offer the quoted value as a 12v DC discharge value.

This might explain the near 100% efficiency rates offered above which by the laws of physics is impossible. But also when fitted into a motorhome or camper van power has to go through the vans own internal battery management systems (Sargent etc) so this will bring the available discharge rates down.

As it stands it could be argued that Ecoflow, Bluetti, Jackery and others should quote the usable discharge power available from their units but they don’t. They just quote the battery storage capacity.

So when buying a unit if you make an allowance that, after heat loss and battery management losses, you can draw in total around 80% of the quoted storage capacity, you can base your daily power requirements on these values and purchase a unit that has a capacity 25% greater than your needs.

But to add that pass through charging is a useful feature when the sun is shining and for me this feature makes the River 2 a ideal low cost generator as I can charge devices and ebike batteries daytime whilst keeping the River 2 topped up with solar at the same time. There might be a slow draw on the battery when using the inverter to charge the ebike battery but as long as 100w is being pushed in then that would give me around 4 to 5 hours of charging time which is more than enough when I normally need 2 to 3 hours for a top up.

 

[colinm]

So how much did you put in, and how low does the BMS allow it to drop? I've seen nothing from Ecoflow to show if the quoted capacity is the total, or usable, without knowing this you don't know the 'efficiency', but your test is helpful to know the true usable capacity.

 

[Moped]

Ecoflow state a 256wh capacity at 100% and the total draw to 0% is around 210w.

Now it took an average mains AC charge input of around 318w for 60 minutes from to charge from 0% to 100%

So overall it took 318w of mains AC charge (around 10p worth of electric at 35p/Kw) to provide 210w of usable battery power. Or £300 for 3000 full charges. Now I also have a 2400wh battery which I assume requires around 3kw to fully charge from 0% at a cost of say £1 so £3000 for 3000 full charges for this. The large unit is not Ecoflow and has a very basic display so calculations not easy to make unlike with Ecoflow. All at current U.K. power prices. So the £500 investment in 400w panels should pay for itself many times over. But I digress.

My main charging method will be solar (free) either direct or via a 12v socket and until we go off for a trip in the motorhome I won’t be able to establish DC charging efficiencies through the XT60 lead and socket.

 

[wildebus]

This is an interesting topic and the dicussion on how efficient Power Stations are intrigues me.

So .... I decided to do a test today on mine. I had this morning a full(100%) VTOMAN Power Station with a claimed capacity of 828Wh
I connected this upto my Motorhome EHU to see how much Watthours it would put into the van.

The charts below show the power it put in and the duration it was running for.

vtoman-out by David, on Flickr
The average power (recorded on a minute by minute basis) was 535W.
The unit ran for 74 minutes until the Power Station output shut down with a "Lo" message, which is 1.233Hours of run time at an average of 535W. Giving a total power IN to the van of 660Wh.

Providing 660Wh on a unit rated at 828Wh would suggest an efficiency of 80%, which is very similar to the Ecoflow. I would have thought it would have been a bit higher TBH.

I did set a current limit deliberately on the input current so the inverter on the Power Station would run at a lower output.
I suspect this 80% is down mainly to inverter losses, and as inverters tend to be most efficient at closer to their maximum rating I might repeat the test without a limit and see if the total power supplied is any higher (the VTOMAN I have has a Continuous 1500W PSW Inverter so could have supplied much more power, albeit for a shorter period of course).

 

[Nabsim]

Not good, in the absence of anything being stated by manufacturers I would expect to get out whatever they rate a unit at. Quoted figures should be actual

 

[wildebus]

Not good, in the absence of anything being stated by manufacturers I would expect to get out whatever they rate a unit at. Quoted figures should be actual

If you were to use it for the 12V DC output I would think (certainly hope and expect) the power out would be near enough the same as the quoted capacity, but there will always be inverter losses to consider when delivering AC power . 20% loss is rather high though IMO.

 

[Moped]

If you were to use it for the 12V DC output I would think (certainly hope and expect) the power out would be near enough the same as the quoted capacity, but there will always be inverter losses to consider when delivering AC power . 20% loss is rather high though IMO.

I accept the inverter loss although was hoping it would be nearer to 15%.

What is slightly puzzling though is that the efficiency is similar for DC ports although I have only used the USB outlets to date and not the 12v socket so there is a conversion taking place when using these as the USB ports are 5v. Be interesting to see how the 12v port compares as I would assume no form of inversion takes place through this port apart from wattage restrictions.

 

[Moped]

Not good, in the absence of anything being stated by manufacturers I would expect to get out whatever they rate a unit at. Quoted figures should be actual

Maybe you do through the 12v outlet but not through outlets requiring inversion either 5v or 240v.

I have yet to check this.

However Mrs Moped has located a 12v portable DVD player that the kids used to watch in the car so just plugged that in to the 12v socket and efficiency is 91% so much better for the 12v socket. After a few minutes now showing 94%.

There is a BMS and operating latent loss so no unit will ever give 100% efficiency but 91% to 94% is reasonable. It is powering WiFi and Bluetooth also.

We do have a 12v USB charging stick so be interesting to see what that draws when plugged into the 12v socket to charge USB devices rather than directly using the USB outlets.

Our motorhome TV is 12v consuming 22w so good news and we will now watch DVDs on 12v the portable player which consumes 16w.

Must admit the Ecoflow app is very good and is a big plus for Ecoflow users. To be able to see inflows and outflows, battery life remaining to the minute, percentage charge, and be able to configure charging rates and other settings through the app makes battery management very simple indeed!

 

[trevskoda]

I have had to sit down after reading all the posts.

 

[Nabsim]

Maybe you do through the 12v outlet but not through outlets requiring inversion either 5v or 240v.

I have yet to check this.

However Mrs Moped has located a 12v portable DVD player that the kids used to watch in the car so just plugged that in to the 12v socket and efficiency is 91% so much better for the 12v socket. After a few minutes now showing 94%.

There is a BMS and operating latent loss so no unit will ever give 100% efficiency but 91% to 94% is reasonable. It is powering WiFi and Bluetooth also.

We do have a 12v USB charging stick so be interesting to see what that draws when plugged into the 12v socket to charge USB devices rather than directly using the USB outlets.

Our motorhome TV is 12v consuming 22w so good news and we will now watch DVDs on 12v the portable player which consumes 16w.

Must admit the Ecoflow app is very good and is a big plus for Ecoflow users. To be able to see inflows and outflows, battery life remaining to the minute, percentage charge, and be able to configure charging rates and other settings through the app makes battery management very simple indeed!

If you bought a 100Ah lifepo4 battery and only got 91ah from it I expect you would be taking it back and that could be powering everything mentioned so I don’t think this is acceptable. Saying that I am still not convinced it isn’t something to do with Wh figures.

Are all these things the same technology as the Bluetti in native 56 or 54v isn’t it so would be converting to 12V anyway.

 

[Moped]

If you bought a 100Ah lifepo4 battery and only got 91ah from it I expect you would be taking it back and that could be powering everything mentioned so I don’t think this is acceptable. Saying that I am still not convinced it isn’t something to do with Wh figures.

Are all these things the same technology as the Bluetti in native 56 or 54v isn’t it so would be converting to 12V anyway.

Hadn’t considered this but yes you are right Ecoflow batteries are not a natural 12v so all outputs require some sort of modification even the 12v output. Neither are Bluetti or any of them it would seem.

Even so the 12v socket seems to be the most efficient one to use.

All these efficiency percentages are post inverter. When using inverters with a 100ah lithium battery you would not get 100ah of power from it if using an inverter. You might get 75ah to 90ah of usable AC power draw depending on quality of inverter.

As such the Ecoflow inverters are middle of the road spec I guess.

Standby mode does drain the battery all be it slowly so some energy is used by the Ecoflow operating system and BMS when it is turned on and power is being drawn. I always turn power stations off when not using.

 

[wildebus]

I reran my earlier test, but this time ran the built-in inverter at full power, starting at 100% SOC and ran until died. I was wondering if at full power the inverter would be more efficient and get more accessible power from the built in battery?

Answer basically was no

The actual power into the Van calculated out to be 620Wh, so 40Wh less than before in fact. Some of the difference may be the ramp down at the end which I don't think I included, plus at 1500W output, the fan on the Power Station was running all the time for cooling, so that obviously used some power as well. So all in all, AC out on my Power Station would be around the 80% efficiency and that is that. (Still want to do a check on the DC out, but I need to set up a DC load and a way to log it).

 

[Moped]

When running the AC inverter at maximum load probably more energy is lost through heat than with a smaller load, and as you say the fan will be working overtime to keep things cool.

I have now viewed several YouTube videos of a various power stations where input and output tests are carried out and, regardless of battery size, efficiency percentages are all very similar. They all confirm that the 12v DC sockets are the most efficient to use. And also the USB- C socket which is also a 12v output.

And if using the power station to power the 12v system in the motorhome or camper van rig up a direct connection using the XT60 port if you have one using the power station as a lithium battery, bypassing the fixed leisure battery with a switch. This is far more efficient use of the power station reserve that using it as a hook up with the onboard inverter.

For every 1kw you push into a battery when AC charging, expect to get around 700wh out when drawing from the battery. That is due to efficiency losses when both charging and drawing out power.

Exactly the same would apply to a stand alone lithium battery as the charger has a 15% power loss when charging so you will use say 1.15kw of mains power to fully charge a battery that can store 1kw. And the inverter used when drawing AC power from the battery will have say a 15% energy loss so you get a net 850w out of a 1150w charge.

But of course we will mainly use solar or campsite hook up for charging stand alone lithium batteries so the input efficiency not that significant.

Stand alone power stations are portable so direct plug in AC charging of these more important and more so the speed at which it charges.