Questions setting up a new Grid-tie system (failures/redundancy/compatibility).

One key decision is batteries.

LiFePO4 and server-rack batteries are popular and have a number of advantages, but there are still teething pains. A key advantage, high charge rate, is only useful for a small battery (e.g. sized for 1 or 2 hours PV production and usage.)

I would assume FLA forklift batteries are readily available in PR. Maybe $6k for 40 kWh, and could last 20 years if sized for 3 days without sun.

I use AGM, twice the price and half the lifespan of forklift batteries. $6k for 20 kWh. I selected them for zero maintenance and high surge current, sized for a bit over 1 hour's PV production but I charge at 0.2C

To go cheap, could use golf cart batteries initially. Maybe $1k for 10 kWh? After some experience and a maturing of the lithium battery market you can decide what to use next.

If you avoid drawing from the battery, e.g. run A/C only while the sun shines, you may get by with a smaller and less expensive battery. Mine for instance is sized to last one 12 hour night, powering a bunch of inefficient refrigerators/freezers. An appliance replacement, or switching them off at night, and my battery could have been half the size.

Hedges said:

One key decision is batteries.

LiFePO4 and server-rack batteries are popular and have a number of advantages, but there are still teething pains. A key advantage, high charge rate, is only useful for a small battery (e.g. sized for 1 or 2 hours PV production and usage.)

I would assume FLA forklift batteries are readily available in PR. Maybe $6k for 40 kWh, and could last 20 years if sized for 3 days without sun.

I use AGM, twice the price and half the lifespan of forklift batteries. $6k for 20 kWh. I selected them for zero maintenance and high surge current, sized for a bit over 1 hour's PV production but I charge at 0.2C

Click to expand...

Interesting! I will look into the FLA forklift batteries setups. The $6k for 40 kWh and 20 years look awesome. What's the catch?

I'm looking for no less than 20kWh and a target of 30kWh. 40kWh will be fantastic. So far I'm looking into SOK Server Rack 5.12kWh & KiloVault HAB V4 4.5kWh. But that 30kWh system will cost me anywhere from $11k - $18k

I saw photos of @pvdude FLA bank and I think I could make something similar. Although I would prefer the AIO rack battery simplicity, the cost/performance of those FLA is tempting.

I'm almost dead on decided on the Schneider XW setup. Now I need to decide on batt & PV panels. I was quoted $270 on 32 Phono Solar 365W mono panels 120cell (PS365M4H-20/UHB). Apparently those are tier 1 panels.

The price and capacity I gave for Forklift batteries was a SWAG. They're very heavy, so local sources is what will matter.
They usually require a forklift, pallet jack, or crane to move. If packaged as individual 2V cells, then you can move them with a dolly.

Quick check on eBay, on the order of $10k for 40kWh
Of course, lead has considerable salvage value. You could ask a shop what they pay for a dead one.


The "catch" is needs maintenance and about 70% efficient round-trip. That is, you'll put 57 kWh into it in order to get 40 kWh out of it, the rest lost as heat (and maybe some released hydrogen.) Must be vented to prevent hydrogen build-up. Will die if not frequently and fully recharged. A self-watering system and/or catalytic recombining caps should make it easier to take care of.

Maybe not always as bad as 70%, that may depend on temperature and charge/discharge rate.
Lithium likely > 90% maybe 98% efficient. Prefers to be partially charged, degrades fast if kept at 100% charge and hot weather.
Lithium might cost you money to dispose of as toxic waste.

To use lead-acid you must have excess PV so it fully charges, including a couple more hours after reaching full voltage.

Looks like my SWAG on golf cart prices is similarly far off, checking Walmart Trojan batteries. Inflation?

People say you will kill your first set of (lead-acid) batteries, so a practice set (maybe second hand forklift) would be worth considering.

Here's LiFePO4 5kWh Server Rack battery from SOK (a good brand) for $2000
Lithium, like lead-acid, has some quirks and issues to deal with. But it is looking like a competitive product, and is the way of the future.

Lead is a commodity with value, and quality batteries cost a premium.

Lithium of course also comes at a price, but we understand manufacture of LiFePO4 cells in China for EV busses results on a certain quantity of reject cells. Those can't handle the high discharge rates of an EV, but are OK for lower discharge rate backing up computer servers or for off-grid power. Some battery vendors claim "A" grade cells, but likely most if not all of the backup power market makes use of the rejects. That makes for very attractive prices. But need quality assembly and a quality BMS; this is a difference among brands.

Probably same thing going on with earlier, more flammable lithium chemistries. They were/are used in EV, also in powerwall type products (likely after sorted for performance.) LG of course has had to eat the recall of Chevy Bolt batteries. They've also recalled their own RESU home batteries.

(Lithium batteries have a "catch" too!)

Here's Trukinbear's battery.
Some years ago, $5000 for about 50kWh, one the dealer had around that wasn't a popular size.
Prices have changed.

scuba_pr said:

Interesting! I will look into the FLA forklift batteries setups. The $6k for 40 kWh and 20 years look awesome. What's the catch?

Click to expand...

Lead acid had lots of catches, all things you can plan for, but plenty of possible stumbling points.

For longevity, you don't want to discharge past 50%, so your forced to buy double the battery capacity you need.
They must be watered/maintained.
You must fully charge them, they don't like partial cycles.
Must be vented outside.
Adding more capacity at a later date doesn't work well. I haven't dealt with this, but there's plenty of reading about adding new batteries parallel to an old bank being bad news for all the batteries involved.
I'm sure there is more, but that's enough for me to steer clear of FLA and lead in general

@pvdude

After the batteries are discharged to about 53 volts, the inverters stop using the batteries and switch to the grid to help support the load.
The transition from PV->batteries->grid is usually less than a minute, depending on the load at the time.

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I assume the transition is seamless, meaning to blip in flow of electricity to loads?

ChrisG said:

I assume the transition is seamless, meaning to blip in flow of electricity to loads?

Click to expand...

Correct. The powered loads are not effected. The only event that interrupts powering the loads is when the grid goes down. The inverters switch to battery in that case drops the load for a second or so, then the loads come back up on battery. I have the computers and networks on UPS for that reason

@pvdude I thought the transfer time between grid and battery was much faster where there would be no noticeable disruption. Also, do happen to know the inverter standby power rating. Trying to figure out for multi day grid outage the additional PV and /or battery required just for inverter.

With the internal transfer relays on the Schneider XW, the transition is split second. The lights flicker and the electronic all stay on at my house. If you're using an external transfer relay ?‍

ChrisG said:

Also, do happen to know the inverter standby power rating. Trying to figure out for multi day grid outage the additional PV and /or battery required just for inverter.

Click to expand...

Do you mean idle consumption?
Depends on what your doing/your settings. If you have any AC load on that needs power it's probably about 60 watts (but I haven't measured it) if you can let it go into search mode, it would be significantly lower.

pvdude said:

Correct. The powered loads are not effected. The only event that interrupts powering the loads is when the grid goes down. The inverters switch to battery in that case drops the load for a second or so, then the loads come back up on battery. I have the computers and networks on UPS for that reason

Click to expand...

I'm planing a system very similar to yours but only one XW (6k) first planing to add a second later; and . I was under the impression that the switching between PV/Batt/Grid was seamless in milliseconds. I'll try to contact the local Schneider installer to verify into this. This is from the XW Datasheet:

1 second is too much and will affect equipment/appliances under load. I do have many 1500+ UPS for sensitive audio/video/computer equipment. But an inverter refrigerator, AC, or other equipment will be affected/reboot under 1+sec transfer time.

Could it be a battery or trasfer relay configuration issue?

400bird said:

With the internal transfer relays on the Schneider XW, the transition is split second. The lights flicker and the electronic all stay on at my house. If you're using an external transfer relay ?‍

Click to expand...

I would use AC IN to AC Out load panel on any inverter (Solark, Outback Radian, XW Pro) so should just seamlessly transition between AC or DC sources.

For minimal load like internet for example, 60
Watts for inverter seems fine. Radian is similar.

Some of these all in ones have crazy high draw.

Why are we not talking more about the silicate salt gel batteries ? They seem to have all the advantages of lead and lithium but none of the dis-advantages. 43 kWh for $12k.

scuba_pr said:

Could it be a battery or trasfer relay configuration issue?

Click to expand...

No idea. There are approximately 34566789 possible configuration combinations and permutations. I can hear a “CLACK” when the inverters switch, so one or more relays are involved.
Suspect the behavior is related to being DC coupled, no sell back.
Also, firmware versions change system behavior in mysterious Schneider ways

ChrisG said:

I would use AC IN to AC Out load panel on any inverter (Solark, Outback Radian, XW Pro) so should just seamlessly transition between AC or DC sources.

For minimal load like internet for example, 60
Watts for inverter seems fine. Radian is similar.

Some of these all in ones have crazy high draw.

Click to expand...

So this means connecting some PV with Micro-inverters to the AC2 of the XW?

I'm planing 16 PV into the MPPT 100 600 for a total of 427.12V @ 24.34A for maximum 7,680kWh - 8,400kWh (w/ bi gain). But I could easily plan for 2 PV into the AC for 960W - 1,050W (w/ bi gain); and leave 14 PV on the MPPT for 373.73V @ 24.34A for a max of 6,720W - 7,350W.

Does that make sense? Will it reduce the possible flickering/transfer issue?

Thanks!

Quattrohead said:

Why are we not talking more about the silicate salt gel batteries ? They seem to have all the advantages of lead and lithium but none of the dis-advantages. 43 kWh for $12k.

Silicate Gel Chemistry Low Temperature – Watts247 Wholesale

watts247.com

Click to expand...

Interesting! Thanks for sharing. I'm still in the planing phase for my batteries and haven't decided yet.

pvdude said:

No idea. There are approximately 34566789 possible configuration combinations and permutations.

Click to expand...

I know what you mean. I've reading the XW/MPPT docs and there are SO MANY config parameters.

I'm still expecting the install labor quote from a local Schneider certified installer. I'll consult and report back.

pvdude said:

Also, firmware versions change system behavior in mysterious Schneider ways

Click to expand...

If it's firmware upgradable all bets are off. This also happens with computers, routers, printers, etc.

scuba_pr said:

So this means connecting some PV with Micro-inverters to the AC2 of the XW?

I'm planing 16 PV into the MPPT 100 600 for a total of 427.12V @ 24.34A for maximum 7,680kWh - 8,400kWh (w/ bi gain). But I could easily plan for 2 PV into the AC for 960W - 1,050W (w/ bi gain); and leave 14 PV on the MPPT for 373.73V @ 24.34A for a max of 6,720W - 7,350W.

Does that make sense? Will it reduce the possible flickering/transfer issue?

Thanks!

Click to expand...

No idea about microinverter. I’m just talking about grid to ac-in, ac-out to loads panel. DC Solar/Batteries pick up when grid fails and switches back when available.

@400bird and @pvdude I just want to clarify, the XW, similar to Outback, can use both AC In and DC at the same time (supplement DC for surge or other), correct? The AC In relays open when grid is down to make sure there is no current going to grid. Is that accurate?

scuba_pr said:

I'm planing a system very similar to yours but only one XW (6k) first planing to add a second later; and . I was under the impression that the switching between PV/Batt/Grid was seamless in milliseconds.

Click to expand...

This is seamless and unnoticed on my setup.

scuba_pr said:

I'll try to contact the local Schneider installer to verify into this. This is from the XW Datasheet:
View attachment 103221

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The transfer switch time is only involved when the grid goes down or comes back (prob generator too, but I don't have a generator)

pvdude said:

No idea. There are approximately 34566789 possible configuration combinations and permutations. I can hear a “CLACK” when the inverters switch, so one or more relays are involved.
Suspect the behavior is related to being DC coupled, no sell back.
Also, firmware versions change system behavior in mysterious Schneider ways

Click to expand...

Mine doesn't do that, well now I've got to go listen this afternoon when it switches from charge to discharge.

ChrisG said:

@400bird and @pvdude I just want to clarify, the XW, similar to Outback, can use both AC In and DC at the same time (supplement DC for surge or other), correct?

Click to expand...

Yes

ChrisG said:

The AC In relays open when grid is down to make sure there is no current going to grid. Is that accurate?

Click to expand...

Yes

400bird said:

This is seamless and unnoticed on my setup.

The transfer switch time is only involved when the grid goes down or comes back (prob generator too, but I don't have a generator)

Click to expand...

Thanks! I will not be attaching a generator either (mine is 120v Honda EU 3000is) so it's not possible. But I do have very frequents grid-down failures of the Power Utility.

I'll find unacceptable a PV system/inverter with battery backup having a 1 sec Grid > PV > Batt transfer time. That will be very noticeable. I expect this to behave like all my APC UPS, just a clicking noise (relay), without affecting any load/device.

I once had an off-brand UPS that it will reboot the PC every time a blackout occurred because of the ~1sec transfer delay.

Quattrohead said:

Why are we not talking more about the silicate salt gel batteries ? They seem to have all the advantages of lead and lithium but none of the dis-advantages. 43 kWh for $12k.

Silicate Gel Chemistry Low Temperature – Watts247 Wholesale

watts247.com

Click to expand...

I'm curious about this to, they seem to handle the heat and cold better and don't require a bms. But, don't they cycle out much quicker on life span and I believe they store less energy.

I was reading in this thread that more than three conext inverters requires a contactor. I guess this is a ATS switch, is this a special item from schneider or any ATS switch. And, why is this?

Second does anybody know if you can stack more than two outback radian 8048's without this sort of requirement?

realpinochet said:

I was reading in this thread that more than three conext inverters requires a contactor. I guess this is a ATS switch, is this a special item from schneider or any ATS switch. And, why is this?

Second does anybody know if you can stack more than two outback radian 8048's without this sort of requirement?

Click to expand...

It is because the internal transfer relays are rated to 60 amps per inverter. In theory you could just stack multiple in parallel adding 60 amps of pass through for each inverter (180amps for 3 parallel inverters)

In reality, there is no way to control how much current goes through each relay. You could have 120 amps through one and 30 through each of the other two (when stacking 3)

Also, if the relays need to open, there is not way to ensure each mechanical relay opens at exactly the same instant. In that cause you could put the full 180 amps through one relay.

This isn't unique to Schneider, it's just how electrical works. Outback should have the same requirements.