Varimax help please

[SolarMusher]

Hi boB, Ryan,

The idea is to let the absorb time increase when bulk time increases ONLY if the battery current when in bulk is above some adjustable preset
value ~AND~ the battery voltage is below the absorb setpoint by an adjustable preset voltage, THEN the counter can count up.
Otherwise, the timer will just stop accumulating absorb time when the battery voltage is not sitting at the absorb voltage.

What would be a good current value to let the absorb time increase with new Varimax FW? That's what I'm not sure to understand.
Example: I have now 3.2kw PV/60A to 830AH/48V batteries (25% DOD, classic 200), could 30A (10am) be a good preset Bulk current to allow the Absorb time to increase? If not, what should be a good bulk current value to begin in this case? Of course C/10, but it's not possible to start a bulk charge on solar at full power. So what, C/5? C/2?
I understand that you want to let Absorb increase only when a minimum bulk current is avalaible and to control Absorb (fixed time) when cloudly with less current to not overcharge. But maybe you could give real math/examples/details for some of us who are not expert.
Thanks
A+
Erik

[boB]

Hi boB, Ryan,

The idea is to let the absorb time increase when bulk time increases ONLY if the battery current when in bulk is above some adjustable preset
value ~AND~ the battery voltage is below the absorb setpoint by an adjustable preset voltage, THEN the counter can count up.
Otherwise, the timer will just stop accumulating absorb time when the battery voltage is not sitting at the absorb voltage.

What would be a good current value to let the absorb time increase with new Varimax FW? That's what I'm not sure to understand.
Example: I have now 3.2kw PV/60A to 830AH/48V batteries (25% DOD, classic 200), could 30A (10am) be a good preset Bulk current to allow the Absorb time to increase? If not, what should be a good bulk current value to begin in this case? Of course C/10, but it's not possible to start a bulk charge on solar at full power. So what, C/5? C/2?
I understand that you want to let Absorb increase only when a minimum bulk current is avalaible and to control Absorb (fixed time) when cloudly with less current to not overcharge. But maybe you could give real math/examples/details for some of us who are not expert.
Thanks
A+
Erik

You have a 48V battery so I would bring that relative battery voltage down at least 1.0 volt... Maybe lower, like, -1.5 volts
below Absorb set point.

On the amps, it needs to be lower than what you normally get out of your system into the batteries but higher than
what you get out of the system early in the morning.  Almost anything should do, like say, 10 amps maybe ??

Maximum time is whatever time you normally want for Absorb time.
Minimum time...  If your system has the chance getting to Absorb soon because the batteries are
already charged and that normal Absorb time is too long for that situation, this is where VariMax
comes in.  In that case, just set the minimum Absorb time to something smaller than your normal
2 hours, say, 1/2 hour ?

Try that for starters.

boB

[SolarMusher]

Great! thanks a lot boB.
A+,
Erik

[SolarMusher]

Hi,
I have varimax set to Min 1/2hr, max 3hr30 and 10 amps , -1.5V as bulk current.
It's works fine.
This morning my Classic absorb time length was 1hr47, I would like to increase this length a little bit, say 1/4hr.
Could I do that if I lower bulk current to 9 or 8 amps?
Thanks,
Erik

[boB]

Hi,
I have varimax set to Min 1/2hr, max 3hr30 and 10 amps , -1.5V as bulk current.
It's works fine.
This morning my Classic absorb time length was 1hr47, I would like to increase this length a little bit, say 1/4hr.
Could I do that if I lower bulk current to 9 or 8 amps?
Thanks,
Erik

If you think the counter should have been closer to  3hr30 than 1hr47  at that time, then yes.  Either reduce
the current and/or reduce that -1.5 volts.   If it was really only 1hr47 that it had to count, then changing
the current or voltage will not make it count faster, but if it is stopping now and then because of the
current/voltage adjustment, then changing those should make it count up quicker.

I would suggest maybe reducing the current to, 8 or 9 amps like you say but maybe also
reduce your -1.5 volts to -1.0 volts ?   Give it a try anyway ?

boB

[SolarMusher]

If you think the counter should have been closer to  3hr30 than 1hr47  at that time, then yes.  Either reduce
the current and/or reduce that -1.5 volts.   If it was really only 1hr47 that it had to count, then changing
the current or voltage will not make it count faster, but if it is stopping now and then because of the
current/voltage adjustment, then changing those should make it count up quicker.

I would suggest maybe reducing the current to, 8 or 9 amps like you say but maybe also
reduce your -1.5 volts to -1.0 volts ?   Give it a try anyway ?

boB

Hi boB,
I don't want to make this counter count faster, speed is limited here  .
No, I just want to make this absorb time a little longer when slightly discharged and was thinking that with a little longer bulk charge which could begin 30mn sooner, it would result in a little longer absorb time, maybe 30mn longer. Am I wrong?
My Classic was planning 1hr47 in absorb time for a little 45/50A discharge and it was correct, this time gave me around 10/12amps end current for a 830Ah battery bank, it sounds pretty good. Yea, I know you're going to ask : why do you want to change these settings which were working fine? Because I'm playing to absorb this 5 years old bank at 62v (previously 59.2V) trying slowly to rise SG to 1.265/70 rather than EQ for 4/6 hours each month. 3.2kw PV give me enough power to full charge this bank 3 days/week.
In two days, I could notice real capacity progress with SG up to 1.255/60, but it was at 10°C so this was only 1.245/50, not a true 100% SOC.
So I'm looking for the limits and another way to fight against sulfation (started this array with 1.1kw 5 years ago )
Erik