Slight change request for lithium batteries

[Collin80]

The manual says that the low voltage trip range for a 48v nominal system can go as low as 40v. However, I'd like to ask that it be allowed to go lower if possible. A 12S lithium ion battery could easily still be OK at 36V. That's, of course, 3V per cell. That's OK. It's probably not a great idea to go much lower. It could go as high as 4.2v * 12 = 50.4 but I think 49.2 is a better upper limit to set. This is currently possible to set either voltage as the upper limit. So, my request is that the lower limit at least be allowed to go down to 36v.  That way a 12S lithium battery can range from 3v per cell up to whatever the user feels is safe (4.2 at absolute most for the chemistry I'm using).

[dickson]

The manual says that the low voltage trip range for a 48v nominal system can go as low as 40v

I think  for a 48v GS6000  inverter at  36 vdc  it output will   be  a square wave 230vac   .   I think 14s  lithium ion battery  will be better  for 48v  inverter .  

[Sid Genetry Solar]

11 hours ago, Collin80 said:

The manual says that the low voltage trip range for a 48v nominal system can go as low as 40v. However, I'd like to ask that it be allowed to go lower if possible. A 12S lithium ion battery could easily still be OK at 36V. That's, of course, 3V per cell. That's OK. It's probably not a great idea to go much lower. It could go as high as 4.2v * 12 = 50.4 but I think 49.2 is a better upper limit to set. This is currently possible to set either voltage as the upper limit. So, my request is that the lower limit at least be allowed to go down to 36v.  That way a 12S lithium battery can range from 3v per cell up to whatever the user feels is safe (4.2 at absolute most for the chemistry I'm using).

Like @dicksonpointed out, this isn't a software limitation as much as it is a hardware limitation. 

You're running Li-Ion, not LiFePo4?  12S is about as difficult-to-handle as it could get, as it's smack right in the middle between 2 standard sizes.  10S Li-Ion is a 36v nominal...and 14S Li-Ion is 48v.  12S is 43.2v nominal, 36v empty, and 50.4v peak.  I have heard of customers running a 48v inverter on a 12S battery...and it simply doesn't work.

With a GS inverter configured for 48v input, the transformer ratio is 7.5 (32 -> 240v).  Absolute minimum battery voltage for a pure sine output (at no load) is 32 * sqrt[2] = 45.248v.  At 36v in, you're guaranteed a square wave with pretty much zero regulation ability with any significant load--in other words, very much useless.  However, for higher voltages, the inverter can simply reduce the PWM width to regulate down.  In short: it's a lot easier for an inverter to handle a higher voltage (throttle the PWM back) than it is to handle a lower voltage (where do you go??)

We have several customers running 12S LiFePo4 battery banks on GS inverters configured for 36vDC; as far as I know, there are no issues at all.  Minimum battery voltage for pure sine output is ~34vdc.

Yes, the posted range of a 36v inverter is up to 48vDC--however, by adjusting the battery nominal setting, you can easily reach a max of 52v if need be.  The high end is limited by crosstalk or FET drive challenges...but we have a customer running a 48v 6kw GS through the wringer at 66v...and thus far, no issues.  (That's an equivalent peak of 49.5v on a 36v system.)  I don't foresee any potential problems at up to 50.4v, though I will note that Lithium-based batteries reportedly have a much longer lifetime if they aren't charged to and held at 100% all the time.  Charging to a peak of 4.1vpc works out to 49.2v, which should be perfectly fine on a 36v inverter.