Setting the wrong BCAP value in a Plasmatronics PL40 charge controller

[Solar40]

What would the outcome be if the Charge Controller BCAP was incorrectly set to 660Ah for 1 year instead of 540Ah?

Solar system: off-grid / 24 x 60W panels / 48V gel battery bank / Plasmatronic PL40 Charge Controller

PL40 Charge Controller settings as approved by battery manufacturer-

VOLT 48V

BMAX 56.4V (Maximum voltage in boost mode)

EMAX 56.4V (Equalisation voltage)

ETIM 0 (Equalisation time in hours)

EFRQ 150 (Number of days between equalization cycles)

ABSV 55.8V (Absorption voltage)

ATIM 3 (Absorption time in hours)

FLTV 54V (Float voltage)

HYST 0.3V (Hysteresis used when not in PWM mode)

BRTN 49.2V (Voltage below which return to Boost mode occurs)

CHRG 40A (Charge current limit)

BFRQ 20 (Maximum number of days between boost cycles)

TCMP 8 (Selection of temperature compensation profile. 8 = no temp sensor)

[Sunking]

Charge at too high of a current. For AGM and FLA no real harm. For Gel could easily destroy the battery by drying out the electrolyte. Unless you have a battery conductance meter or can do a capacity test there is no way to tell if you harmed your Gel batteries. Gel batteries should not be used for cycle service applications.

[mapmaker]

Charge at too high of a current. For AGM and FLA no real harm. For Gel could easily destroy the battery by drying out the electrolyte.

This thread is another attempt to get some answers about these 6 PVV 660 Secura batteries.
First attempt here: http://www.solarpaneltalk.com/showthread.php?15743

Here are some specs on the battery: http://www.batteriesdirect.com.au/sh...3/2089011.html

from the spec sheet:

Charge Current: Unlimited, the minimal charge current has to be I₁₀

As I indicated in the previous thread, I don't know what I₁₀ is, and I have never heard of a gel battery (or any other) that could handle unlimited current.

--mapmaker

[inetdog]

As I indicated in the previous thread, I don't know what I₁₀ is, and I have never heard of a gel battery (or any other) that could handle unlimited current.

--mapmaker

I think that the kicker here is the specification of absolute max voltage of 2.40/cell.
That will put a limit on the charge current, although while the battery is at a low SOC the bulk current might get pretty high. Possibly that current will not cause damaging gas bubbles as long as the terminal voltage stays low.

The battery may have a higher internal resistance than we expect to see from FLA or typical AGM. Based on the listed R_I, the voltage drop due to internal resistance at 60A (C/10) would be about .036 volts. Run that up to common charge rates for AGM and you get 600A and a drop of .36 volts per cell. That may be enough to keep the actual voltage drop across the electrodes below the gassing voltage if the terminal voltage is held to 2.400.
But it still seems uncomfortable.

The "microporous separator and silicon oxide gelling sound a lot like some AGM designs.

Any knowledge of this mystery battery Dereck?

[Sunking]

I think that the kicker here is the specification of absolute max voltage of 2.40/cell.
That will put a limit on the charge current, although while the battery is at a low SOC the bulk current might get pretty high. Possibly that current will not cause damaging gas bubbles as long as the terminal voltage stays low.

That is a function of the battery internal resistance and state of charge. The model in question has a specified IR of .6 milli-Ohms per cell (2 volt cell). So if we ere to configure them as 12 volts is an IR = 3.6 mill=ohms which is fairly low. Lower than a like rated FLA, higher than a like AGM. So now assume we have an unlimited current source 14.4 volts (2.4 vpc), and a battery SOC voltage of 12.2 volts. The charge current would have to be [14.4 - 12.2] / .0036 Ohms = 611 amps on a 600 AH battery. As the battery SOC voltage rise to meet the supply voltage, current tapers off. This is called a Constant Voltage or Float algorithm. Obviously this is way to high and impracticable not too mention a lot of heating of 611 amps x 611 amps x .0036 Ohms = 1343 watts of heat energy dissipated by the battery which would cause thermal runaway in a AGM or Gel battery

Turn this around to reality and say we have a 100 amp 14.4 volt source, with the same battery SOC voltage and initially the power source will go into current limit of 100 amps and thus be a Constant Current source (aka Bulk Charger) until the battery voltage reaches 14.4 - [100 amps x .0036 ohms) 14.04 volt at which point we go into Constant Voltage and the charge current will taper down as the battery voltage approaches supply voltage.

The "microporous separator and silicon oxide gelling sound a lot like some AGM designs.

Any knowledge of this mystery battery Dereck?

Silicon oxide crystals are the gelling agent in all gel batteries. Basically a like design for FLA with the difference instead of liquid Acid between the plates you have jello. AGM is electrolyte starved Absorbed Glass Matt separator between the plates, or think wet blanket or dirty diaper between your butt and your sheets on a bed. What is strange and I have no idea of how it affects performance is the plates are PbCaSn aka solder with calcium added. Beats me what that would do. I know calcium is added to lead for strength, but throw in Tin is a first for me. Adding tin to lead lowers the melting point of lead. Not sure that is a good idea or not.

But what really raises that Red Flag for me is conflicting statements. On one hand they claim a 10 to 20 year battery, and on the other hand 1500 cycles. 10 years does not = 1500 cycles. Never heard of the battery manufacture before today. The plate design is Tubular Plate vs Flat Plates which is nothing new as each has its own advantage. But the biggest advantage with respect cycle life goes to Flat Plates, and the big advantage of Tubular Plates is lower IR and ruggedness needed in Fork Lift and Traction applications. You cannot have it all, would be nice, but not possible to have it all.

[PNjunction]

The tin alloy just reduces negative-plate corrosion, especially at elevated voltages during either absorb or EQ.

[Sunking]

It is the positive plates that corrode.

[mapmaker]

The tin alloy just reduces negative-plate corrosion, especially at elevated voltages during either absorb or EQ.

It is the positive plates that corrode.

As I understand it, oxygen produced on the positive plates during gassing is what causes corrosion of positive plates.

But negative plates also corrode... I posted a picture of negative plate corrosion here:

http://www.solarpaneltalk.com/showthread.php?p=110965#post110965

--mapmaker

[Solar40]

As I indicated in the previous thread, I don't know what I₁₀ is.

Lively discussion! Thanks.

From the manufacturer, regarding the minimum charge current required for the batteries-

The minimum charge current is 1.5A/100Ah C10. This equates to 7.95A

[PNjunction]

..The minimum charge current is 1.5A/100Ah C10. This equates to 7.95A

Careful - that rate is only good if you have enough time to fully recharge it. That means finishing absorb, and perhaps many hours on float, which would not be healthy for cyclic service if the extended time turned out to be ridiculous.

I find it interesting that they have seemingly overcome the standard gel maximum inrush of C/20 at 14.0 volts absorb or so. Not mentioned either is that if placed into solar service anyway, that a gel's CAR or charge acceptance rate also affects float too! You get whammied on both the start and finish of charge.

But if they overcame this, that is interesting. My initial thought is that while it may serve as a deep-cycle, the publication of 120-hr rates and more lead me to believe that the primary application is standby / float duty for UPS service that may include long-term low-current applications.

...my 02c ...

[Solar40]

Thanks all for your input.

I'm now of the opinion that the BCAP setting for the PL40 is only useful for the SOC and will have no bearing on how the battery bank is charged.

From the manual-

BCAP sets the effective Amp-hour capacity of
the battery being charged by the PL. This is used
by the State of Charge data screen.

I can't find any other BCAP information in the manual that suggests any different.

Any thoughts?

[inetdog]

Thanks all for your input.

I'm now of the opinion that the BCAP setting for the PL40 is only useful for the SOC and will have no bearing on how the battery bank is charged.

From the manual-

BCAP sets the effective Amp-hour capacity of
the battery being charged by the PL. This is used
by the State of Charge data screen.

I can't find any other BCAP information in the manual that suggests any different.

Any thoughts?

While some other CCs set the EndAmps for Absorb based on the entered battery capacity, there is no evidence that the PL40 does that sort of thing. You might double check that though.

[Solar40]

While some other CCs set the EndAmps for Absorb based on the entered battery capacity, there is no evidence that the PL40 does that sort of thing. You might double check that though.

Thanks Inetdog
I'm happy to put this thread to bed now as this has just come in from Plasmatronics, the manufacturer, regarding the PL40-

'BCAP is only used as one of the inputs for calculating SOC. It has no bearing on how the battery is charged. It will not cause any damage.'

Thanks to all for contributing.