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Mastervolt Charger Question - moving to LiFePo4

indimini

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Jan 29, 2021
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Hi all - long time lurker, but this is my first post. I am looking to upgrade from my current AGM configuration (2 270 Ah Mastervolt AGMs) to either 2 280 Ah or 3 200 Ah LiFePo4 batteries built using prismatic cells most likely with a 200 A Daly smart BMS.

Background
Our boat is currently set up with a Mastervolt Mass Combi 12/2500-120 charger inverter and the Mastervolt Solar Chargemaster 60 MPPT solar charger. On the Mass Combi, there are four charge profiles. First is standard which is bulk which builds up to 14.4V until it reaches absorption (14.4v) and then float (13.25v); Then there is an option for Gel/AGM/Spiral which adds .55v to the float phase (13.8v). Option 3 is "traction battery", increasing the bulk stage +0.7v and absorption stage + 0.4v. Lastly, they have a forced float option which sets all 3 charge modes to a fixed 13.8v.

The solar charger can be configured for Mastervolt's Li-ion batteries which performs some messaging on their Masterbus which I don't believe I can do. There are options for a user-defined charge profile on the MPPT where I can specify voltage for absorption/float and set max current, so I think that would be the best route forward for that charger.

Question
My question is for the Mass combi, which battery profile would be best (if any)? The constant 13.8 V profile seems too low, but their standard 3-phase profiles also seem less than ideal. I would like to keep the Mass Combi as I expect 80% + of my charging will come from my solar (800 W total), but don't want to commit to the charger/inverter if it risks damaging the batteries long term. Any experience with this equipment or other thoughts/suggestions are appreciated.
 
Welcome to the forum.

Constant 13.8V is bad. You never want to float a LFP battery above 13.6V.

from:


ACID

14.4 bulk
14.25 absorp
13.25 float

This is the only program I would consider.

The downside to this configuration is you may not get the battery fully charged, but you should get close. That's not necessarily bad as that may increase cycle life.
 
Thanks snoobler! Digging deeper into the docs, it looks like bulk charge time in hours, absorption and float voltages can be configured via their masteradjust software (which I have along with the necessary PC interface). Thinking I could set absorption to 14.25 set bulk charge time to 0 hours, and set the float to something in the low 13's.
 
A float of 13.6V is pretty ideal. Even if you don't get fully charged @ 14.4/14.25V, 13.6V float will get you to about 95%.
 
This is an old thread - but a very useful one. Thank you @snoobler.

I have a similar setup. Do you know what % of full the Mass Combi will bring the LiFePo4 batteries to? I don't mind that TBH if it is kinder to the batteries.

And will it charge more slowly than a charger with a dedicated LiFePo4 profile?

Thanks for the great help!
 
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