Magnum settings for a lithium bank

[OT66]

Hello,

I have recently purchased 2 x 24V, 200AH lithium batteries. I've chatted with some very helpful people on here and elsewhere. I also got suggested charging parameters from Magnum. There are people saying the CC/CV profile is what I want while others, including Magnum say to use "custom". I'm attaching the battery spec sheets. Can I get some input on if these settings seem reasonable? Some have looked at them and are unsure why they would make some of those suggestions. I have a Magnum MS4024PAE inverter.

The suggested settings from Magnum are ...
02 Low Batt Cutout= 23.6V or higher
03 Absorb Time= 2hr
04 Batt type= Custom, Absorb= 28.8, Float= 26.4, EQ= 28.8
05 Max Charge Rate= 100%
_
09 Final Charge Stage= Silent, ReBulk= 26.4
-
11 Bulk Always= ON

 

[JLD]

I have the same system.
Low battery cut out 24v
Absorb30 min
Custom absorb 28v float 27v EQ 28v
Max charge I change as needed. 100 works
Final charge silent rebulk 26.6
I will take battery's to 29v every 15 to 30 days to balance.

 

[sunshine_eggo]

Hello,

I have recently purchased 2 x 24V, 200AH lithium batteries. I've chatted with some very helpful people on here and elsewhere. I also got suggested charging parameters from Magnum. There are people saying the CC/CV profile is what I want while others, including Magnum say to use "custom". I'm attaching the battery spec sheets. Can I get some input on if these settings seem reasonable? Some have looked at them and are unsure why they would make some of those suggestions. I have a Magnum MS4024PAE inverter.

The suggested settings from Magnum are ...
02 Low Batt Cutout= 23.6V or higher
03 Absorb Time= 2hr
04 Batt type= Custom, Absorb= 28.8, Float= 26.4, EQ= 28.8
05 Max Charge Rate= 100%
_
09 Final Charge Stage= Silent, ReBulk= 26.4
-
11 Bulk Always= ON

My neighbor has this exact unit and the custom setting thwarted diagnostic efforts for like a year.

I'm 100,000% certain you need to use CC/CV.

If you use custom, you will trigger frequency shifting as it approaches absorption voltage EVEN IF IT'S NOT CHARGING. This caused the inverter to go from 60Hz to 58.3Hz, and a handful of his appliance clocks lost 8 minutes every day. Again, it will do this even if it's your PV chargers achieving absorption voltage.

 

[OT66]

Thanks for your input. I've read about custom vs. cc/cv profiles a bit with Magnum. Is there any downside to the CC/CV, or anything I need to be aware of that would be better suited to a custom profile? Most of this is way over my head and my primary concern is to not damage an expensive lithium bank.

 

[sunshine_eggo]

Do you plan to AC charge regularly or as backup?

 

[OT66]

Do you plan to AC charge regularly or as backup?

I have either option. My system is plugged into an inverter/generator when I'm at the off grid cabin and I just fire it up as needed. In the winter I just spend weekends there, so I may run it a little bit each day if I'm getting low and then on Sunday before leaving I would charge it up completely (this was with my AGM bank in the past) and then turn the entire system off. In the summer I basically live there and solar can keep up for the most part but if I'm running things like toaster, vacuum etc. I would turn on the generator for a bit.

 

[sunshine_eggo]

Generally speaking, you don't want to run much in CV mode on generator as it gets progressively less fuel efficient as the battery approaches full.

I wouldn't worry about it as I doubt you'll leave your generator running for too long in CV/absorption mode.

It's been awhile since I looked at how to setup CC/CV mode, but my neighbor uses it for generator backup only.

 

[yodamota]

Looks like the battery "Gel" setting would be a good setting to use. as it sets the equalize voltage to the same as the absorption voltage. Along with unplugging the battery temp sensor.

https://www.magnum-dimensions.com/sites/default/files/MagArchive/64-0003-Rev-D-ME-RC.pdf

 

[jberger]

I don't have 24v batteries, but I am running (2) Magnum 2812's connected to (3) 12v LFP 400ah batteries.
I use CC/CV with the temp sensor disconnected (very important), equalization turned off and the end charge terminated by end amps.

 

[OT66]

Here's what my battery manufacturer suggested. 20V low battery cut out is way too low, isn't it? Is recharge and rebulk the same? They have recharge at 28.8 others say 26.4.

In my system, I only have AC power when I go turn on the generator. I bought a Victron shunt, so my plan was to watch the battery capacity and then fire up the generator typically when the batteries get to about 50%. Is that reasonable? If that's the case, is the rebulk/recharge number irrelevant in my application? It will be relevant in the summer when I have solar, so I would want to set my solar controller so that it doesn't overcharge?

 

[sunshine_eggo]

fire up the generator typically when the batteries get to about 50%. Is that reasonable?

yes.

If that's the case, is the rebulk/recharge number irrelevant in my application?

No.

It will be relevant in the summer when I have solar, so I would want to set my solar controller so that it doesn't overcharge?

It is typically relevant to PV. A brief dip due to heavy load doesn't necessarily warrant a full recharge cycle.

 

[sunshine_eggo]

I don't see that your remote allows for CC/CV configuration.

IIRC, my neighbor has the ARC50, and we were able to set to CC/CV

IMHO, AGM2 is almost a perfect setup.

Once you hit absorption voltage, simply kill the generator.

 

[OT66]

I don't see that your remote allows for CC/CV configuration.

IIRC, my neighbor has the ARC50, and we were able to set to CC/CV

IMHO, AGM2 is almost a perfect setup.

Once you hit absorption voltage, simply kill the generator.

I'm not sure about some of the other versions but I do know that my ME RC-50 Rev. 2.8 does have a CC/CV profile. I checked last weekend. Thanks for your input on all of this. I'm trying to figure it out.

 

[sunshine_eggo]

I'm not sure about some of the other versions but I do know that my ME RC-50 Rev. 2.8 does have a CC/CV profile. I checked last weekend. Thanks for your input on all of this. I'm trying to figure it out.

ah... it was @yodamota that linked the other ARC. Can you link the manual?

 

[OT66]

I have the same system.
Low battery cut out 24v
Absorb30 min
Custom absorb 28v float 27v EQ 28v
Max charge I change as needed. 100 works
Final charge silent rebulk 26.6
I will take battery's to 29v every 15 to 30 days to balance.

Thanks, what's the size of you bank? 100AH, is that why 30 min absorb? Magnum told me 30 mins per 100ah, so for my 400ah bank 2 hours?

 

[JLD]

I have a very large bank 4800AH, with 4 inverters. That is kind of why I like to balance to 29v at least once a month. My battery's will cycle from 100 to 85% most days but once or twice a month I let them go down to 35%. 30 min absorb has just worked, so have not increased.

 

[OT66]

I have a very large bank 4800AH, with 4 inverters. That is kind of why I like to balance to 29v at least once a month. My battery's will cycle from 100 to 85% most days but once or twice a month I let them go down to 35%. 30 min absorb has just worked, so have not increased.

OK thanks. Pmd you as well

 

[sunshine_eggo]

Thanks, what's the size of you bank? 100AH, is that why 30 min absorb? Magnum told me 30 mins per 100ah, so for my 400ah bank 2 hours?

Magnum support has taken a big downturn with the move to Mexico. It took the better part of two years to resolve a MS4024PAE issue. They didn't. This forum did.

Their answer is very generic and pretty stupid for LFP.

LFP voltage is slow to rise unlike lead acid, which rises to absorption at about 80% @ 0.1C
When LFP reaches absorption at a similar 0.1C rate, it is nearly poked full at 98%+

When charging to 3.50+V/cell, it's RARE that more than 15-30 minutes is needed. The only time this wouldn't be true is if your battery bank is very imbalanced, or your wiring doesn't facilitate even current sharing. Even then and hour would be plenty.

Your inverter is capable of 105A output. That's about 0.25C - not a high charge rate. Magnum advice was stupid.

15-30 minutes absorption. Not a minute more.

Remember your battery is poked plum full at 28.8-29.2V at 0.05C, i.e., when absorption is achieved, and the current has decreased to 20A, it's full. Stop charging. Period. After that, you're over-charging.

It's also arguable for generator charging to stop the moment you get to absorption voltage as you're gal/kWh starts increasing, i.e., it costs more $ for each % SoC you add in absorption.

 

[OT66]

Magnum support has taken a big downturn with the move to Mexico. It took the better part of two years to resolve a MS4024PAE issue. They didn't. This forum did.

Their answer is very generic and pretty stupid for LFP.

LFP voltage is slow to rise unlike lead acid, which rises to absorption at about 80% @ 0.1C
When LFP reaches absorption at a similar 0.1C rate, it is nearly poked full at 98%+

When charging to 3.50+V/cell, it's RARE that more than 15-30 minutes is needed. The only time this wouldn't be true is if your battery bank is very imbalanced, or your wiring doesn't facilitate even current sharing. Even then and hour would be plenty.

Your inverter is capable of 105A output. That's about 0.25C - not a high charge rate. Magnum advice was stupid.

15-30 minutes absorption. Not a minute more.

Remember your battery is poked plum full at 28.8-29.2V at 0.05C, i.e., when absorption is achieved, and the current has decreased to 20A, it's full. Stop charging. Period. After that, you're over-charging.

It's also arguable for generator charging to stop the moment you get to absorption voltage as you're gal/kWh starts increasing, i.e., it costs more $ for each % SoC you add in absorption.

You're clearly very knowledgeable and I appreciate your input. Unfortunately, it's usually way over my head so a couple of questions please. I know earlier you suggested CC/CV but I'm planning to use the custom battery type at least initially. This was Magnum's response when I mentioned the frequency changes that you posted about earlier ...

"Thank you for your patience while i discussed this with my lead tech. Frequency shift can happen on the PAE models of inverter when using these settings, but ONLY when AC coupling to sell power back to the grid. If you are not AC coupling i would recommend sticking with custom settings as CC/CV can be inconsistent."

Using a custom profile, am I correct to assume that when I start my generator to charge my batteries, it's going to go into a Bulk stage, and how long it stays in that stage is dependent on what? Based on how I set it up using the values above, is it going to charge the bank to about 98% in bulk mode? I'm putting a Victron smart shunt in the system to help me get some info. to help monitor the system, so ideally I just want to confidently get these batteries up to 100% the first time I charge them, so that I can configure the Victron saying they're 100% charged and then from there, when I'm charging the batteries, even if my parameters are off (example, absorb is set to 2 hours when it should be 30 minutes), will the Victron tell me what % charge they're at, so that I know to shut off my generator?

 

[sunshine_eggo]

Again, a Magnum tech couldn't resolve the issue. I don't trust them. There was no AC coupling present and the AC coupling setting is enabled by specifying a custom battery type.

Other's with Magnum experience, one a former Magnum tech, directed me to the solution - select a default battery type or use CC/CV. I have shared that with you.

When charging with generator, absorption should be minimized and float should be completely avoided. When your battery hits absorption voltage, it will be nearly full. Since LFP experience no benefit from being fully charged like lead acid, it's least costly to charge between 50-90% vs. 60-100% as an example. That same 40% increase in SoC will cost you more because the generator is less efficient at lower power.

Note step 1:

https://www.magnum-dimensions.com/sites/default/files/product/manual/64-0032%20C%20%28Owners%20Manual%2C%20MS-PAE%20Series%29.pdf