unusuaul "Resting"

[australsolarier]

fng,
lifepo4 batteries have 56V bulk, so that 67V should be plenty enough.
i also have a resting problem in my 12V system.
there is a victron and a midnite classic and after float the midnite sometimes just keeps resting until such time as i manually rebulk. it just won't come out of resting. this is in legacy mode. on solar mode it does not do that. however when in bulk after a while it will reduce the charging rate.
all to do with lifepo4 and midnite classic charger. that is one of the reason sense wires are so important.

[boB]

The terminals at the battery should be even higher than at the charge controller so it might have even less of a chance of turning on with sense wires.

The new CC's have external sense though.

If the PV input voltage is not high enough, external sense wires won't help it turn on unfortunately.

boB

[australsolarier]

ah yes, i am aware the new charge controllers have sense wires.
any idea when they are going to be on sale?

[boB]

ah yes, i am aware the new charge controllers have sense wires.
any idea when they are going to be on sale?

We are hopefully going to be able to take orders this summer or fall

Hopefully   

[FredB]

That is an awful low voltage for a 48v battery using MPPT, For example lets assume the lithium is at 52 you need 130% of that to wake up, So 67.6v. I am going to say the array voltage is just to low for MPPT charge controllers to work. I would suggest getting the voltage up closer to 100v

FNG, That's right! I knew this! Actually the Midnite Classic manual says "Keep in mind that an MPPT controller needs to have the open circuit voltage of the array about 33% higher than the highest battery voltage" But I forgot that when I upgraded from 24V to 48V. Thanks!

[boB]

That is an awful low voltage for a 48v battery using MPPT, For example lets assume the lithium is at 52 you need 130% of that to wake up, So 67.6v. I am going to say the array voltage is just to low for MPPT charge controllers to work. I would suggest getting the voltage up closer to 100v

FNG, That's right! I knew this! Actually the Midnite Classic manual says "Keep in mind that an MPPT controller needs to have the open circuit voltage of the array about 33% higher than the highest battery voltage" But I forgot that when I upgraded from 24V to 48V. Thanks!

Yeah...   If the PV input voltage is on the edge now, the system will work better with a wee bit higher input voltage.

Of course, it isn't easy to raise the input voltage a "wee" bit   

Maybe by cooling it down but that isn't going to be happening during the next few months in the positive latitudes !

The "positudes"   

[FredB]

That is an awful low voltage for a 48v battery using MPPT, For example lets assume the lithium is at 52 you need 130% of that to wake up, So 67.6v. I am going to say the array voltage is just to low for MPPT charge controllers to work. I would suggest getting the voltage up closer to 100v

FNG, That's right! I knew this! Actually the Midnite Classic manual says "Keep in mind that an MPPT controller needs to have the open circuit voltage of the array about 33% higher than the highest battery voltage" But I forgot that when I upgraded from 24V to 48V. Thanks!

Yeah...   If the PV input voltage is on the edge now, the system will work better with a wee bit higher input voltage.

Of course, it isn't easy to raise the input voltage a "wee" bit   

Maybe by cooling it down but that isn't going to be happening during the next few months in the positive latitudes !

The "positudes"   

Well If I could just increase the output of the Sun by 33% that should do it. I'm actually surprised any of the CC's are working, I need 56 Absorb Volts X 133% = 74.48V and none of the arrays output are that high. You're right though as it gets hotter the problem will get worse. Sigh, I will just have to rewire the arrays. I'm glad I made them all free standing and not bolted to a roof!

[boB]

IF you were just a volt or maybe two shy of the Classic turning on, you "could" possibly, in a pinch, adjust the PV input voltage tweak so that it thinks the PV is a volt or two higher than it is...  Not a good long-term solution and you don't want to change that voltage much more than that though.

Don't tell anybody I even suggested this though !   

[FredB]

Problem solved! I rewired the arrays and all's good now. Thanks everyone!

[boB]

Problem solved! I rewired the arrays and all's good now. Thanks everyone!

Excellent !!    Thanks for letting us know, too !