Mix-and-match inverter and battery chemistry

[byteseven]

I'd like to extend my current home battery by replacing the current 5 kWh battery with a second hand EV battery. I have a Fox AC1 inverter coupled with a Fox battery

The plan would be to use Dala's emulator to connect the EV battery and the inverter. The AC1 datasheet specifically states the chemistry is "LFP". I'm not 100% sure what that means but I presume it means "only works with LFP batteries". This seems odd to me because surely the battery reports its own SOC which the inverter uses this information to switch CC/CV modes etc.

Getting a hold of LFP EV batteries second hand isn't easy/cheap here but a older Nissan Leaf battery is. So, I'm looking for some reassurance that the inverter-chemistry match is not strict and something like Dala's battery emulator will take care of the correct charging etc.

Am I barking up the right tree?

 

[Korishan]

The charger (not the inverter) only cares about LFP vs Li-Ion for charge curve profiles. However, even if it doesn't have an LFP option, you can just use Custom and set those parameters manually.
But more importantly the charge profiles are usually more for Lithium and Non-Lithium chemistry.

If you can get a hold of LFP batteries, go that route. Far safer in the long run.

The inverter portion only really cares about about voltages. I'm guessing you have a combination unit that has a Charger and an Inverter built together.

There are some units that can only do Lithium, or only do Lead Acid, for instance. This is because of the way the charger works. Lithium does require a CC/CV mode, Lead Acid doesn't really use this in the same way. So the charger needs to know if it needs to back off near top charge.

You'll generally be just fine using LFP with your inverter/charger with no issues. Just use Custom settings if you can't get the values set exactly where you need them.

 

[OffGridInTheCity]

Welcome to the forum!

As you go down this journey, please feel free to post questions, perhaps some pics of you're Inverer's setting options and it's likely we can help with discussion/more detailed info until you're comfortable with you're choices.

Google "AC1 Inverer" got me this - https://www.self2solar.com/products...-in-one-solar-inverter?variant=50370558492947 What do you have (more exactly) - e.g. what's you're specific model number. I'm looking for a user manual / spec sheet.

 

[byteseven]

The charger (not the inverter) only cares about LFP vs Li-Ion for charge curve profiles. However, even if it doesn't have an LFP option, you can just use Custom and set those parameters manually.
But more importantly the charge profiles are usually more for Lithium and Non-Lithium chemistry.
...
I'm guessing you have a combination unit that has a Charger and an Inverter built together.
...
You'll generally be just fine using LFP with your inverter/charger with no issues. Just use Custom settings if you can't get the values set exactly where you need them.

I am being lazy with my terms. I'm sure your quite correct that its the charger that cares. For my install I believe the charger and inverter are a single box. I have a Fox H1/AC1.

From what you've said it seems that the Dala emulator can be configured to translate from one chemistry to another. Could you point me at the relevant documentation?

If you can get a hold of LFP batteries, go that route. Far safer in the long run.

Indeed. Unfortunately, I may be either waiting a long time or spending more than my budget or both! I'd rather aim for better than perfect at this point. If an LFP battery pack lands in my lap in the future then I'll already be set up!

 

[Korishan]

the charger and inverter are a single box. I have a Fox H1/AC1

Gotcha, so yeah, lazy part wins, I do the same for combined units No worries. I just wasn't sure if you had 2 units or a single combined unit.

From what you've said it seems that the Dala emulator can be configured to translate from one chemistry to another. Could you point me at the relevant documentation?

I'm actually not sure myself, but I'm sure @Dala could probably do that though

But generally speaking, you don't "translate" from one chemistry to the other. It's all about voltage settings/limits. Lead Acid for example has a voltage range of 1.98V - 2.11V per cell. There are 6 of them in a 12V battery, so 11.88 - 12.66V, even though we charge to 13.8V (this is more to force equalization); for 48V that'd be 47.52 - 50.64V with a top charge of 55.2V. Whereas Lithium-Ion (NMC's) have a range of 3.2V - 4.2V, for a 48V that's 44.8 - 58.8V. And for Lithium LFP it's 2.8 - 3.5V or 44.8 - 56V.

So you can see here that depending on chemistry, you have to select the proper voltage settings. That's really it. The only major reason for chargers to be labeled as Lithium/LFP/Sodium/etc compatible is that they have those settings pre-programmed in the firmware. Also there's the charge curve characteristics which is where the Bulk/Float voltages come into play. Otherwise, if you know the values you need for any battery, you can just use the Custom settings option and put in all your own values.

waiting a long time or spending more than my budget or both!

Completely understand that statement!!

 

[OffGridInTheCity]

Following the Fox HC1/AC1 link I see this for the battery specs....

and battery options look pretty straight-forward (e.g. max charge/discharge current and min/max SoC)

 

[Dala]

You do not need LFP batteries. You just need to make sure the battery that you add has an OK voltage range for the inverter.

 

[byteseven]

You do not need LFP batteries. You just need to make sure the battery that you add has an OK voltage range for the inverter.

Ah. Perfect thank you. Matching the voltages between the inverter/charger and the battery makes perfect sense.

Following the Fox HC1/AC1 link I see this for the battery specs....
...
and battery options look pretty straight-forward (e.g. max charge/discharge current and min/max SoC)
...

I'm familiar with those settings they are unfortunately only percentages rather than voltages.

Its looking like Zoe batteries are much more available and reasonably priced which according to Dala's wiki are 300-400 V. Seems like they are the prime candidate for my project.

My plan would be to source the necessary electronics, configure and understand them prior to getting a battery. This would mean less money spent upfront and less hassle etc. Getting a battery, storing it then mounting it is likely to be the biggest time/effort part of the project.

To test their setups do people just hook up a DC power supply as a mock battery and test it out etc?

 

[Dala]

To test their setups do people just hook up a DC power supply as a mock battery and test it out etc?

Yes, you can test a battery before purchase, or directly after purchasing it to see that all cells are balanced, and that SOH% is OK. This is usually done with a 12V battery, some wiring loom, and the Battery-Emulator. It requires some setup, but it is oh so worth it.

Example (old example from 2020 before battery-emulator existed, 12V battery connected to OBD2 adapter, and a wiring loom to a LEAF battery)

The wiki page for the Zoe will show you how to do the wiring. Just substitute the OBD2 adapter for the Battery-Emulator hardware instead!

 

[byteseven]

That's good advice which I will bear in mind. However, I wasn't thinking of testing the battery but the _inverter-gateway_ combination.

Imagine this. I have everything _except_ a Zoe battery. How would one test this is configured and wired correctly? I suspect this will be the most challenging part of the project and I'm hoping it can be done without a huge battery taking up space in the garage. [And avoid the associated Girlfriend complaints]

 

[Dala]

That's good advice which I will bear in mind. However, I wasn't thinking of testing the battery but the _inverter-gateway_ combination.

Imagine this. I have everything _except_ a Zoe battery. How would one test this is configured and wired correctly? I suspect this will be the most challenging part of the project and I'm hoping it can be done without a huge battery taking up space in the garage. [And avoid the associated Girlfriend complaints]

There is a built in "Test fake battery" mode in the Battery-Emulator, to test out inverter-emulator comms beforehand