Newbie started with a 16s 3.2v 100Ah LiFePO4

Hi,

I'm Keni, here is my 48v 100Ah so far.

I'm using a Batrium and 16 longmans... I will eventually plug this into a Victron, my solar and mains... May build another bigger system in the future, depending on how it gets on...

Wish those batteries were around when I started - look great and fast to build!

Very nice
LiFePo4 & Victron fan here too
Note - only charge to 3.45V not 3.65V if you want them to last

keni said:

Hi,

I'm Keni, here is my 48v 100Ah so far.

I'm using a Batrium and 16 longmans... I will eventually plug this into a Victron, my solar and mains... May build another bigger system in the future, depending on how it gets on...

Click to expand...

Welcome. I'm heavy 18650 and Batrium and would love to have a LifePo4 setup one of these days

If I could ask - how are you using them (PV/powerwall or?) and how are you controlling max (charge) / min (discharge)?. I use the voltage range to turn my inverters on/off in an off-grid PV/powerwall setup as 18650 has a wider voltage range that facilitates this but LifePo4 is such a flat voltage....

Welcome to you! That is a nice intro, yes!

Thank you for the welcomes, very nice indeed...

@Redpacket - thank you for that, I thought as much.

@OffGridInTheCity - funny enough I was going to ask that same question. I'm trying to understand why my shunt wasn't stopping a cell over charging. But I guess I'm not understanding how the shunt works.

keni said:

@OffGridInTheCity - funny enough I was going to ask that same question. I'm trying to understand why my shunt wasn't stopping a cell over charging. But I guess I'm not understanding how the shunt works.

Click to expand...

A shunt measures and reports on coulombs (ah) going to/from the battery. From this, you can determine charge and discharge amp-hours and SoC. It typically doesn't perform actions but provides data for something else to take action.

In my case, I use my Midnite Classic 150s (charge controllers) as the control unit based on voltage. They know about battery voltage and have external relays to turn my inverters (the load) on/off. I use a Classic to turn things on at 51.5v, limit max charge to 56.6v (4.04v/cell), and turn things off at 49.5v (3.54v/cell) - e.g. all done by battery voltage. Here's the on/off software control screen for external relay AUX1 to illustrate:

I can chose my operating DOD by adjusting the voltage hi (absorb/float) and low(Off Volts above). And I should point out that I'm off-grid - so its all about turning on the inverter when the batteries are charged enough and turning off the inverters when the batteries get to the low voltage. There's no grid-tie (sharing power to the grid) involved.

For LifePo4 I'm not sure the preferred method of control is by voltage since the curve is sooooo flat. I'll be interested to hear how you proceed and others may comment

Wow, thank you again for a detailed response...

I think I get it now, in short a shunt us just another tool for measurement, not control...