Installation of Discover AES batteries.

[geoffrey_t]

Can anyone explain the differences between Outback's recommendations for programming the FXR for discover batteries and Discover's spec sheet recommendations.

I have attached the Application note from Outback regarding the programming for FXR for Discover batteries and also the spec sheet from the Discover.
How did Outback come up with a Re-bulk Voltage? Is that off the Discover spec sheet?
Why did Outback suggest a Low Battery Cut in of 51.2 when Discover has Restart Voltage after LBCO at 52 volt?
Why did Outback suggest an Absorb End Amps of 0Adc when Discover has Absorption Termination Current at 2A?

Did anyone use Outback's recommendation with success?
Thanks.
I'm trying to switch from my lead acid to lithium and need a hand understanding the new programming required.

discover_install.pdf

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open-loop-integration discover.pdf

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[raysun]

I've not used AES/Discover, but have integrated several brands of LiFePo4 with Outback gear.

A couple of suggestions/observations:

• Use the battery vendor's spec sheet. They are the ones designing and warranting the battery. They are also the one that gets customer feedback that causes them to "refine" their specs. I wouldn't expect Outback to publish much past the initial release testing.

In the rare case the vendor has made an error in their latest specs and you catch the inconsistency, call them on it. Most vendors want their stuff to work without headaches, and AES is a 1st tier vendor.

Some specs take careful reading in order to understand the context. In the case of:
Outback Absorb End Amps = 0
and
Discover Absorb Termination Current = 2A
the two parameters are related, but not the same thing. If you notice, OB is listing it for the FlexMax Charge Controller. 0A is correct. Refer to the manual for the reason. Discover's Termination Current (which Outback refers to as Charged Return Amps) is the net charge current that signals when to terminate the Absorb phase. The 2A would be a per battery block spec. I assume with 4 inverters the battery is multiple blocks, in which case the termination current will be 2A x # of battery blocks.

FWIW the above discussion of termination current is entirely academic unless the system has some sort of quality battery monitor that can sense the net charge current at the right time and signal the chargers to terminate. In the Outback ecosystem, that would be the FNDC. I don't see that listed in your profile.

[geoffrey_t]

Can you please explain why Zero is the correct setting for "Absorb End Amps".
I went to the Flexmax charge controller manual and searched for "Absorb End Amps". I couldn't find an explanation for why this is the correct setting. I found one table that said:"Absorb End Amps
Default 00 Adc Range: 00 to 55 Adc"

[raysun]

Absorb End Amps is primarily designed to help control charge termination from a stand-alone controller, under a very narrow set of circumstances.

The charge controller only "knows" the gross amps it delivers to the battery bus. It has no way of knowing what portion of those amps is going to battery charging, and what portion is servicing loads. Further, it has no way of knowing the contribution of other chargers working in parallel.

The sole case where charge controller Absorb End Amps can work is where it is the sole charging source, the charge termination amperage is known, and the battery discharge (load service) is known and unchanging.

For example, assume the charge termination amperage is 10A, and the load 5A. In this case, Absorb End Amps could be set to 15A, and would be an accurate charge termination point.

Next let's assume the load varies, and at the putative charge termination point, the battery is accepting 10A, but the load is drawing 30A. Now, the 40A demand on the charger means the Absorb End Amps point of 15A would not be reached.

Finally, a 15A net charge to the battery, and 0A load demand would end charging prematurely.

Those are the "well controlled" cases of a single charge controller. With multiple charge controllers, Absorb End Amps is meaningless in all conditions.

Set Absorb End Amps = 0 to keep the charge controllers from acting in unpredictable manners.

I'll repeat the most critical question in this discussion. Does the system have a quality battery monitor, or does it not?

[geoffrey_t]

Thank you for the excellent explanation.
Does the Mate 3s distinguish between load amperage and battery charge from multiple chargers?

[raysun]

No, it doesn't distinguish amperage at all. The individual charge controllers can report gross output, but the Mate can't itself do anything with the information other than display it.

If the FLEXnet DC battery monitor is added to the system, then net current and state of charge can be derived. The Mate can use these data to dynamically control the charging process.

[provo]

Does the Mate 3s distinguish between load amperage and battery charge from multiple chargers?

To do that you need a battery monitor like the Outback FlexNetDC (FNDC), and some shunts. Here's a screenshot from the FNDC User's Guide:

That third shunt at the bottom could be on a second charge controller. If you go that route you might want to look into OpticsRE if you don't have it -- the combination of the FNDC and Optics is very powerful.

[porch13]

I'm getting ready to swap out my 48V Rolls bank for a pair of Discover 4-44-6650's. I'm digging through both Discover and Outback's documentation on programming (I have an outback FLEXpower ONE FXR which is roughly 5 years old) and was wondering which settings you @geoffrey_t ended up going with and how it's working out for you. Thanks!

[sdgustafsson]

I replaced my old Lead Acid batteries with Discover AES 2 years ago. I have a lot of experience with Outback VFXR3524A inverters and Discover AES Lithium Ion Battery (14-24-2800).

First thing I have to say is Outback with FDC do to track the batteries at all. Also, the recommended settings are not right. You really need to have a laptop running Discover AES Dashboard to really setup up the inverters. The BMS controls the battery, so there's no need to worry about over-charging the batteries. But the inverter will turn itself off if the FNDC thinks the batteries are at a low state even. when t he batteries themselves say they are 50%charged. You will have to unplug the FNDC every few days to reset it.

Please send me a message if you want more info.

Cheers,
Seth

[raysun]

But the inverter will turn itself off if the FNDC thinks the batteries are at a low state even. when t he batteries themselves say they are 50%charged.

This is not exactly how the FNDC and inverters work. The inverter Low Battery Cut-Off (LBCO) is triggered on voltage, not State of Charge. The inverters measure the battery voltage with their own internal voltmeters, the FNDC has no role in LBCO, or HBCO for that matter.

You will have to unplug the FNDC every few days to reset it.

This is an unusual operation to say the very least. Properly configured, the FNDC does a credible job tracking charge and discharge current, and deriving State of Charge from the values. Like all "current counting" meters, it is prone to drift, and periodic synchronization is needed. That drift is typically below 5% on my system, as measured by the FNDC and also by an independent Victron battery monitor. Being off by 50% and requiring an arbritrary "hard reset" to 100% by unplugging it suggests the FNDC is misconfigured, damaged, or something radically wrong in the shunt wiring/battery circuit.