Inverter/charger setting

[ddutton]

Seeking advice on Inverter/charger settings. I use my gen a couple times a day to fill my pressure tank and I’d like to maximize that charging time. The lithium iron phosphate batteries have such a flat voltage curve that even at 70% the charger goes straight to float charge. I have a magnum mm1224. It has a remote so I can manually set absorb and float. My batteries are 280ah configured to 24 volt. What settings do I need to get the charger to kick into bulk charge? Thanks.

 

[upnorthandpersonal]

Somewhere at 28V should work, which gives you 3.5V per cell. After that, float to 27V (3.375V per cell).
What are your parameters at now?

 

[John Frum]

I don't have experience with that unit.
Its good to include a product link so that we can find the manual to see what the specifics are.
So this is generic advice.

Try these
bulk/absorb=3.55 volts per cell
If the absorption phase is terminated by tail current set it to 14 amps
If an absorption timer set it to ~15 minutes
disable float

Hopefully you have a shunt based battery monitor and a bms that allows you to see the cell delta.
Discharge until the weakest cell starts to nosedive.
Make note of the pack voltage when it does.
You want to re-bulk before that cell nose dives.
After a couple of cycles the shunt based battery monitor will tell you how much of the battery you are using.
Since we don't know the charge current and the charge current is probably not totally deterministic tweak as necessary to get pack 90% full(~252 amp hours) and the re-bulk setting to just before the weakest cell starts to plummet.

If you really want to float you can set it to 3.35 volts per cell but since your are charging from a generator that is probably not what you want.

 

[Greendream]

Do you have the magnum remote me-rc or me-arc?

 

[ddutton]

Yes I have the remote now set to 28.4 absorption and 27.0 float.
Batteries at 26.7 v or 75% doc. Start gen and goes straight to float no charge. I have it set to charge at 30 amps bulk.

 

[jtvt]

Google "magnum mm1224 goes straight to float"

Magnum Energy ME2012 stuck in Float Charge - iRV2 Forums

My inverter stays in the Float charge and my house batteries are boiling over. The invertor is supposed to go into the Full Charge mode after the Float mode is complete; it does not do this. The

www.irv2.com

Magnum mms 1012 charging issue

I am trying to trouble shoot an installation. Magnum mms 1012 inverter charger, with a ME-RC remote.

forum.solar-electric.com

etc

Sounds like there may be some problems with those units.

 

[ddutton]

After doing a bunch of research I discovered this inverter when it sees over 26 volts it decides the battery is charged. That’s 3.25 per cell, they don’t get below that until they are down to less than 10% soc now I need to see if magnum will update the software on them.

 

[John Frum]

After doing a bunch of research I discovered this inverter when it sees over 26 volts it decides the battery is charged. That’s 3.25 per cell, they don’t get below that until they are down to less than 10% soc now I need to see if magnum will update the software on them.

Did you try disabling float?

 

[John Frum]

After doing a bunch of research I discovered this inverter when it sees over 26 volts it decides the battery is charged. That’s 3.25 per cell, they don’t get below that until they are down to less than 10% soc now I need to see if magnum will update the software on them.

What research led you to that conclusion?

 

[jtvt]

After doing a bunch of research I discovered this inverter when it sees over 26 volts it decides the battery is charged. That’s 3.25 per cell, they don’t get below that until they are down to less than 10% soc now I need to see if magnum will update the software on them.

That sounds like legacy lead acid train of thought.

I wonder if you dropped 1 cell out from 8s to 7s, things would work better. Maybe you would run into other problems.

 

[ddutton]

Did you try disabling float?

Unfortmatley I don't have that option. Older inverter and remote, I'm hoping magnum can up date the software.

 

[ddutton]

What research led you to that conclusion?

Did google search came up with manual and problems section and described exatly what I'm experiencing.

 

[ddutton]

That sounds like legacy lead acid train of thought.

I wonder if you dropped 1 cell out from 8s to 7s, things would work better. Maybe you would run into other problems.

Thought of that then single cell voltage would be too high.

 

[RCinFLA]

There might be some opportunity using equalize mode if you can set its voltage.

 

[ddutton]

There might be some opportunity using equalize mode if you can set its voltage.

Thanks I'll try that next time i'm up to the cabin.

 

[ddutton]

I got it work by forcing it into equalize mode. Generator isn’t on long and charge monitored. Inverter is 14 years old so this method will work until I have to upgrade.