Will SOK 48V batts work with old model Trace SW5548 inverter system

[showme]

I'm thinking of using SOK 48v LiFePo batteries with my system, which will be stacked Trace SW5548 inverter/chargers. The rest of the system is the standard Xantrex power panel, except for swapping the C40 charge controllers for Midnite Solar Classic 150's. Is there any reason this system wouldn't be compatible with SOK's? Thanks for any thoughts on this. Lee

 

[showme]

Has anybody else even heard of SOK batts?

 

[GVSolar]

Use "custom" battery set-up and conservative charge/discharge lifepo4 specs and you should be fine Disable temperature compensation. Be aware of low temperature restrictions. Assuming you are off-grid. Look at @Steve_S recommendations...

 

[showme]

Thank you!

 

[OzSolar]

Has anybody else even heard of SOK batts?

Yes. I think a lot people have them here. My first time to lay hands on them will be late next week when my they get here. I have a dual stack Trace SW4048's.

I assume you're talking about the 100 AH 48v server rack style? Thanks to the SW's easily programmable charging voltages and absorption times we should be able to charge them correctly. Common wisdom for a long life is to "live between the knees" which I interpret to never getting below 10% SOC and above 90% SOC. (here comes Cunningham's law)

Use "custom" battery set-up and conservative charge/discharge lifepo4 specs and you should be fine Disable temperature compensation. Be aware of low temperature restrictions. Assuming you are off-grid. Look at @Steve_S recommendations...

Everything on these old school Trace SW's is custom. There isn't a stock Flooded or AGM setting per se. Good point on temp comp. I think you disable it by unplugging the temp sensor.

 

[GVSolar]

As I understand it, you need to disable automatic equalization. And set temperature compensation to 0°. Unplugging the temp sensor would not be sufficient. Based on the system description (frozen batteries) pay careful attention to battery compartment temperatures.

 

[showme]

Thanks, OZ! I know there are people on here (you, for one) are here with these systems that either use them or are going to. I just forget who those people are, so I can't ask them. But, yeah, the 100ah are the one's I'm about to order. I finally heard back from the guy at Current Connections who told me as long as the charge parameters lined up, it should be ok. But I wanted to hear it from somebody who knew something about the Trace inverters (or older Xantrex) so I don't ruin something right out of the gate. And just before I got on here, I ran across a really good page with a ton of information I was looking for. And it's in layman's language, not techno speak that I don't comprehend. https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/

It confirms your advice about not charging to 100%, turn off the float mode, turn off the balance mode and the temp sensors. (I'll have to go back and pull the 4 on mine). So they're disabled by just disconnecting the plugs? Thanks, I was wondering about that.

So, how many are you getting, and did you catch the sale? Two weeks ago when I was deciding, there were close to $1800@. They're $1650 right now. I think I'm getting the 5 stack, though I thought about just getting two to start with. They sound like great batteries. And after that article I just read which talked about the BMS system being the weak link in LiFePO's, the SOK's absolutely make sense.

A few questions- what type/size fittings are their battery posts accepting? I've got the Trace 4/0 cables with ring fittings. Will those work? Also, are your inverters going to be able to use the CANbus/RS485 comm or is that a no-go with these. I still haven't figured out what the rest of the RYconnections in the AC side are for. I know 7 and 8 are for gen controls, and one is for a remote panel. But not the rest of them. Anyway, let me know when you get them! I want to hear how your set up goes. Lee

 

[OzSolar]

As I understand it, you need to disable automatic equalization. And set temperature compensation to 0°. Unplugging the temp sensor would not be sufficient. Based on the system description (frozen batteries) pay careful attention to battery compartment temperatures.

I'm guessing we are not talking about the same inverter. I just took a peak at the manual and drilled into all all of the menus on my 23 year old Trace SW inverters. There are no user adjustable settings for temp comp. There's just one menu related to it and it reports "temp comp volts". With no sensor plugged in it's the actual battery volts and when I plug it in temp comp volts raised a few degrees reflecting that they live in a barn at ~45F at this moment.

 

[GVSolar]

I'm guessing we are not talking about the same inverter. I just took a peak at the manual and drilled into all all of the menus on my 23 year old Trace SW inverters. There are no user adjustable settings for temp comp. There's just one menu related to it and it reports "temp comp volts". With no sensor plugged in it's the actual battery volts and when I plug it in temp comp volts raised a few degrees reflecting that they live in a barn at ~45F at this moment.

It's entirely possible you're correct. I don't have that particular model – I do have the original trace 2512 and an SW4024. Both still running – one in my barn and one for my well pump.

 

[OzSolar]

So they're disabled by just disconnecting the plugs? Thanks, I was wondering about that.

That's what I'm seeing but you'll want to double check that.

So, how many are you getting, and did you catch the sale? Two weeks ago when I was deciding, there were close to $1800@. They're $1650 right now. I think I'm getting the 5 stack, though I thought about just getting two to start with.

I'm getting four splitting them up into two sets of two using a Victron Lynx for the bus which will allow me to charge and discharge at 2x's the rate of just putting all 4 on a single stack.

Also, are your inverters going to be able to use the CANbus/RS485 comm or is that a no-go with these.

No clue but I doubt it. Hopefully someone else has burned that bridge already and will chime in. My not so well though out plan was to manually monitor them via the Victron smart shunt but that is something we really want to have to figured out before try to "set it and forget it"

A few questions- what type/size fittings are their battery posts accepting? I've got the Trace 4/0 cables with ring fittings. Will those work?

I ~think~ they are M8 which is pretty close to 5/16". You probably have 3/8" ends on your current cables.

 

[showme]

Thanks for the info. I'm slowly (very slowly) wading into all this a step at a time. Also, I found something that directly opposes what I found on that site I posted above, and you mentioned it, too. And I found this "corrected" information on none other than Current Connected's site. It's from the owners manual of the SOK batteries, ch 3 under the Stand Alone Operation Set Points heading-A common misconception about LiFePO4 (LFP) is that it is best to operate in the 30%~90% SOC region, however this applies to every other lithium based chemistry except for LFP. If you only charged these batteries to 90%, then the BMS would never have a chance to offer any cell balancing due to the stable nature of LFP’s charge curve. If cells get out of balance, then the capacity of the entire pack is reduced to the capacity between the fully-discharged voltage of the lowest cell and the fully-charged voltage of the highest cell. If packs are not regularly balanced by the BMS, then the difference in balance can easily overcome what the BMS is able to correct, leading to quite poor performance of the system in general. So, I guess there's a good reason to take them to 100%, even though I read you could get 3 times the calendar life out of them if you stayed under 90%. On the other hand, that article may have been a little dated (but still very interesting)

 

[OzSolar]

It's entirely possible you're correct. I don't have that particular model – I do have the original trace 2512 and an SW4024. Both still running – one in my barn and one for my well pump.

Odd I would have thought that both of those would be the same as my SW4048's. ?‍

 

[showme]

GVSolar- I was reading on the site I referenced above that frigid temps won't hurt Lifepo's 'physically', since they don't contain water, they can't swell up like lead acid batts. It does say that these bats will stop "charging" below 32*, but they'll continue to discharge if necessary to something like -4*. Not that I'd leave them out in that, but they definitely have another advantage over lead acid.

 

[OzSolar]

So, I guess there's a good reason to take them to 100%, even though I read you could get 3 times the calendar life out of them if you stayed under 90%. On the other hand, that article may have been a little dated (but still very interesting)

Right! I do recall seeing that now. What a rabbit hole...

Ironically what you're describing sound an awful lot like an equalization charge (of sorts) for FLA.

I've worked on off grid systems using big 2V FLA batteries for 30 some odd years now. A few of them are over 20 years old and still pretty damn stout. I don't think there's anyone that can say that about LiFEP04's.

I ordered the computer cable interface dongle "thingy" for the SOK's so I can plug the batteries into my laptop to help with my understanding of them.

 

[RCinFLA]

One thing you really need to get right is the coordination of inverter's low battery cutoff and BMS cutoff. Basically, do everything possible to avoid having a BMS shutdown. The old SW5548 and like units lose all your settings when battery power is loss and go back to default settings when battery power is reestablished.

Make yourself a plastic covered cheat sheet, in most important order, and keep it by inverters, just in case.

When things get chaotic remembering the red-green simultaneously buttons push to get into setup menus above level 9 seem to be easily forgotten.

Set equalize voltage down to your float voltage as secondary safeguard and disable equalize mode.

 

[JoeHam]

So, I guess there's a good reason to take them to 100%, even though I read you could get 3 times the calendar life out of them if you stayed under 90%. On the other hand, that article may have been a little dated (but still very interesting)

I’m running two different 100Ah 48V nominal LFP batteries which never have been, and never will be taken to 3.65V per cell.

Neither BMS has any problem keeping balance and I see no reason to stress them or have an accidental overvoltage event trying to accomplish some benefit that I do not see a need for.

One of my batteries is home brew and the other is one of these :

100 Ah LiFePO4 @ $1250 usd. 48v nominal

Let me start by saying that I have an affliction where I read almost every post on this forum. I then wander down various paths following up on what I find interesting. I recently came across this company on one of my rabbit hole trips and I cannot remember the thread where I found this...

diysolarforum.com

They were recently on sale for $1499 FWIW.

 

[RCinFLA]

I see no reason to stress them or have an accidental overvoltage event trying to accomplish some benefit that I do not see a need for.

Balancing cells needs an hour or two of absorb level charging, depending on balancing current capability, at least once a month, charging to at least 3.5v per cell.

Out of balance cells are most common issue with users of self-contained 12v LFP batteries. Users complain of loss of capacity or battery shutting down when attempting a full charge because they have not brought battery to 14.2-14.4v absorb charge often enough to activate balancing of cells.

LFP cells can take full charge better than other Li-Ion chemistries. Other Li-Ion chemistries have more cathode degradation due to lack of cathode lattice support structure when cell is fully charged. In LFP cells, iron provides a vertical support to fully charged state cathode lattice.

Full charging does stress the negative anode graphite, fracturing SEI protective layer that is regrown on subsequent recharging which consumes a small amount of available lithium in cell reducing capacity over time. Maintaining a high state of charge does accelerate electrolyte degradation a small amount. High charge and discharge cell current also does similar damage.

 

[showme]

OZ- that's incredible hearing that those FLA's (L16's?) are 20 years old! You said "a few of them"- does that mean you've mixed new and old batteries?? I didn't think that was a good practice. As a matter of fact, I just had one of my Silverado's batteries (Duramax diesel has 2 batts) go south, and even though the primary batt was still strong, I bought 2 new since I was under the impression that you don't mix old and new. Now have a spare batt that's just sitting there, wanting to be used. And you're completely correct on the statement about 'not being able to say that about Lifepo's", since they haven't been around that long (yet).

RC- Great idea. As I've put my system together, I had to re-wire nearly everything on the power panel, and the walls in the shed were covered in copies of manual pages and hand drawn schematics. Your idea for a list will be next to my panel is a good idea. Thanks! And your advice on keeping the equalization mode set to float is what the manual says about that- Some chargers allow float to be disabled, however we do not recommend doing so. By leaving float enabled and set at the recommended voltage, the charger (whether solar or grid) will provide the power to loads FIRST, and the battery will make up for any additional current demanded by the loads. Floating in this manner will prevent discharging the battery while ample charge is available – whether coming from Solar, Grid or Generator. If floating was disabled or set to a lower voltage, then the battery could be significantly discharged when the user thinks that it’s been connected to a charger and should be full and ready to go.

 

[Nobodybusiness]

Has anybody else even heard of SOK batts?

I have 15 of the 48v Server rack batteries and so far they work fine.

Bought them from CurrentConnected.com
Have a 10 year warranty.

Only had them couple months.

 

[showme]

15 100ah batts? That's 72kw of stored power. Is this a commercial operation?