Use of charger in VFX2812 w/ lithiums?

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Use of charger in VFX2812 w/ lithiums?

Postby svbravo on Fri Apr 01, 2016 1:48 am

I've finished my install of lithium battery modules for use w/ existing Outback gear (see profile for description). I'm having trouble setting up the VFX2812 charger. The charging algorithm for lithiums is quite different than lead acids. The highest voltage that the VFX will allow for "refloat" is 13.0, but 13 volts for the lithiums would be too low. It will never turn on until the batteries' s.o.c. is way down.

For example: Say the batteries are down to about 40%, after several very cloudy days. Not a lot of solar. I'd like to run the generator for an hour or two to get them back up. Unfortunately, even when they're at 40% s.o.c., they will be above 13.0 volts, so the "refloat" will not turn the charger on. I'd like to be able to set the refloat to somewhere around 13.5, but the VFX won't go there, max is 13.0, at least w/ my firmware. Therefore, even w/ the generator running, the charger will not charge the batteries.

The only work around I've found is to run an "equalize" cycle for an hour at a time at 14.0 volts. The lithiums are perfectly happy there, and the charger pushes about 85 amps happily into the bank...sweet. I just wish I could do it in a more "normal" fashion, w/o requiring the awkward work around.

Anyone have any ideas? Is there a firmware upgrade I'm not aware of that might allow the higher refloat setting?

Thanks for the help,
Adam

s/v Bravo
Whangarei, New Zealand
svbravo
Junior Member
 
Posts: 4
Joined: Wed Jul 27, 2011 3:12 pm
My RE system: Outback gear: VFX2812 Inverter/Charger, FLEXmax 60 charge controller, FLEXnet DC monitor, MATE display, network hub.
12v Lithium battery bank: 600Ah total, Sinopoly 200Ah cells, 4 cells per 12v module (x3 modules)
BMS: EMUS system, inc. individual cell monitor boards, Canbus modules (1 per 12v module), Bluetooth module, monitoring app on Android
Genset: 5kw diesel
Boat is set up as 12vdc / 120vac

Re: Use of charger in VFX2812 w/ lithiums?

Postby blackswan555 on Fri Apr 01, 2016 4:24 am

I can not think there would be a difference, But the 24/48 v versions will start a normal charge cycle as soon as they see AC in, eg you Start your gen, yellow flashing ac light on mate, light go's solid, Click in the inverter, Runs normal bulk /absorb cycle,

Tim
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
blackswan555
OutBack Emperor
 
Posts: 2483
Joined: Sat Aug 30, 2008 5:50 am
Location: Ibiza Spain,
My RE system: Other peoples, VFX "E" versions, FLA`s, Generators.

Re: Use of charger in VFX2812 w/ lithiums?

Postby svbravo on Fri Apr 01, 2016 7:20 pm

Hi Tim
That's what I'd expect as well. Used to work that way when I used w/ the old AGM's. But I've made many adjustments to all of the system, and am thinking I inadvertently tweaked the wrong setting, so the charge cycle does not start. When AC is present (genset on), the yellow AC light on the mate DOES flash then go solid. All good. But no charging. It seems like it should go right into it's bulk/absorb cycle automatically. I have that set for 1 hour at 13.7v. Would then go to float, which I've set at 13.6v for 1/2 hour. I'd think it would continue that way, float at 13.6 for the set 1/2 hour, then refloat, and again and again, until fully charged. But at this point, it is not even starting to charge when AC comes on.

I also may not fully understand the Outback "refloat" concept. The max value I can program in is 13.0 volts, which, of course, is too low for the lithiums. Lithiums don't want a tapered charge, but rather a flat rate, with all stages pretty much equal. So, to go to 13.0v for "refloat" won't really work.

Basically, I'll usually want to just turn on the genset, have charging continue until my Flexnet DC tells me that the batts are nearly topped up, say 90% s.o.c., and shut it off. The pv's take it from there. (The BMS provides backup safety, and will open a charge relay, cutting off all charging, if any cell is approaching max s.o.c.). I don't typically plug into shore power, but rather use pv's for all needs when at the dock.

Cheers
Adam
svbravo
Junior Member
 
Posts: 4
Joined: Wed Jul 27, 2011 3:12 pm
My RE system: Outback gear: VFX2812 Inverter/Charger, FLEXmax 60 charge controller, FLEXnet DC monitor, MATE display, network hub.
12v Lithium battery bank: 600Ah total, Sinopoly 200Ah cells, 4 cells per 12v module (x3 modules)
BMS: EMUS system, inc. individual cell monitor boards, Canbus modules (1 per 12v module), Bluetooth module, monitoring app on Android
Genset: 5kw diesel
Boat is set up as 12vdc / 120vac


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