40A SRNE MPPT: Am I doing this right?

Hi All,

Using a 40A SRNE MPPT in my van to charge 2 x 100Ah lithium batteries in parallel. The default lithium profile seemed a bit aggressive to me with boost and float set to 14.4v and voltage charge limit and voltage cutoff set to 15v and 16v respectively. Using this profile I charged my batteries to full and then using my BMV-712 monitored the battery voltage with no load settle back to 13.31v over the next 48hrs.

My batteries are B grade cells, but are delivering on their rated capacity. To try and be as gentle on them as possible as solar will be the only always on charging source, I've now set battery voltage cut off to 14.5v (max for battery) and max battery charge to 14.4v. I have also set the boost voltage to 13.8v and float to 13.4v. Should I have float at 13.3v instead?

Do these numbers seem ok, or am I going to end up with significantly undercharged batteries as a result?

nicoloks said:

Hi All,

Using a 40A SRNE MPPT in my van to charge 2 x 100Ah lithium batteries in parallel. The default lithium profile seemed a bit aggressive to me with boost and float set to 14.4v and voltage charge limit and voltage cutoff set to 15v and 16v respectively. Using this profile I charged my batteries to full and then using my BMV-712 monitored the battery voltage with no load settle back to 13.31v over the next 48hrs.

My batteries are B grade cells, but are delivering on their rated capacity. To try and be as gentle on them as possible as solar will be the only always on charging source, I've now set battery voltage cut off to 14.5v (max for battery) and max battery charge to 14.4v. I have also set the boost voltage to 13.8v and float to 13.4v. Should I have float at 13.3v instead?

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Cut off values don't matter. They pertain to the load terminals.

13.8V boost will charge the battery much more slowly, but should get you to > 98% SoC with a 2 hr boost duration and is generally regarded as a "gentler" charge that should improve cycle life. 13.5V float would be better.

Good to know about those cut off values, was wondering why they'd have the defaults set so far above the max of all the lithium batteries I've ever had.

Have set the float to 13.5v and the boost cycle time to 120m (it was set to 0). Thanks for the tips!

You can optimize the boost time. When the battery is at 13.8V and the current has dropped to about 6A, it's about as charged as it will get. If you find that happens in under 120 minutes, you can pull it back.

How do you like the srne mppt? And bt app?

yourunclefats said:

How do you like the srne mppt? And bt app?

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my comment is belated
i used srne ml 2440 and bluetooth bt-1 for a year
in a 12 volt system there were two panels of 595 watts and two MPPT controllers, one for each panel
now I switched to AIO SRNE 24 volts, and so far it seems to me that everything is getting worse, but maybe I haven’t figured it out yet

if you need a separate mpt controller, I could safely recommend srne ml2440 because they only made me smile like the phone application