Wayne Dohnal wrote:
-=dwh=- wrote:
His 55a WFCO charger went straight to constant current bulk stage and didn't overload the generator.
The prof might be one of the <10% of WFCO users that has adequate battery wiring to kick the WFCO converter into its 14.4 volt mode, but the other 90+% of WFCO users never have greater than the 13.6 volt converter output. For generator charging, they'd be better off with a single-stage Magnetek at 13.8. I didn't mean to hijack the thread, just pointing out that the Prof's WFCO installation is not representative of most. My relative new motorhome is an example of the typical WFCO installation, where the charge voltage never once exceeded 13.6 until I swapped in a PD for the WFCO. As for pampering the batteries, when I'm in the boonies charging with the generator, I'm willing to sacrifice some battery life to reduce the generator run time.
On the one hand, you say the problem is inadequate wiring, on the other hand you say it's the converter.
I must say, that I find it hard to believe that the vast majority of WFCO 3-stage chargers just magically never go into bulk stage. In truth, I don't believe it.
In any case, I think the relevant point is that the CPE inverter gen will run a 55a 3-stage charger in bulk stage, but won't run an 80a charger in bulk stage.
But...there was something in the Professor's test results which didn't jibe - but I couldn't figure out exactly what it was. Having slept on it, now I know what it was that didn't seem quite right...I'll try to describe it...
Connect CPE to 80a PD converter/charger.
Push button for "boost mode" (bulk stage).
CPE overloads.
Okay - why does the CPE overload? Because the converter/charger is trying to pull enough current to do a constant current 80a bulk charge on the battery (that's the theory anyway).
Then...
Connect CPE to 80a PD converter/charger.
Allow PD to do a constant voltage charge for one hour.
Push button for "booost mode" (bulk stage).
CPE does not overload.
Now here's the thing - that should not have worked.
Multi-stage chargers operate in two modes. They operate as constant
current chargers in bulk stage, and then they operate as constant
voltage chargers in the absorption and float stages.
When the button is pushed to put the PD into bulk stage, the converter/charger should be trying to drive 80a into the battery. It should raise its output voltage however high is required to get 80a to flow, and keep doing that until the battery voltage reaches 14.4v, at which point it switches to constant voltage mode and holds at 13.6v. After 30 hours, still in constant voltage mode, it will drop the voltage to 13.2v for float stage.
That is in fact how an Iota converter/charger behaves with the IQ/4 module installed, though it stays in bulk stage until the battery reaches 14.8v or 4 hours, whichever comes first. It then does absorb stage at 14.2v for 8 hours before dropping to float at 13.6v.
Now...here's the rub.
If the PD actually behaved like a proper mult-stage charger, then when you hit the boost button, it should switch into constant current mode and pump out 80a until the battery reaches 14.4v. That should happen any time that button is pushed if the battery is below 14.4v.
But that's not what happened in the Professor's test. That's what was niggling at the back of my mind. A mystery!
So, I decided to look into it. I can't find a manual online for the charge wizard, but the PD 9200 series has the charge wizard built-in and I can find a manual for that:
http://www.progressivedyn.com/PD9200_Manual.pdfAnd what did I discover?
That the PD is NOT a true multi-stage charger! It doesn't DO constant
current at all. What is actually is, is simply a multi-
VOLTAGE charger. What PD calls multple "modes" is actually just multiple voltages - 14.4v, 13.6v, 13.2v.
Aha! So that's what happened! When the Professor hit the boost button, the PD increased its output voltage to 14.4v, which cause SOME extra amps to flow into the batteries - however NOT the full 80a that a real constant
current charger would have pumped out.
A constant voltage charger simply raises the bus voltage to a certain point, and then allows the battery to absorb however much current can overcome the battery's internal resistance.
So when the Professor first pushed the button to switch the PD to 14.4v, enough current flowed into the batteries to overload the CPE. After an hour at 13.6v, the batteries had absorbed enough that when the PD bumped up the bus voltage to 14.4v, it really made no significant difference in how much
current was flowing to the batteries - and thus the CPE did not overload.
Mystery solved.
So, while I was at it, I decided to look into the WFCO as well. The only WFCO unit I saw that is rated at 55a is the 9800 series (dunno exactly which unit the Professor has but he did say it was 55a). I found a manual online for the WFCO 9800 series:
http://www.wfcoelectronics.com/documentation/manuals/Manual%20-%20WF-9800%20English.pdfAnd what did I discover? That it is also a multi-voltage charger that also does not do constant
current charging. It operates the same as the PD - by simply adjusting the voltage that it outputs to the bus.
So the significant difference in why one would work from the CPE and not the other really has nothing to do with their max amperage ratings. The determiniing factor is how much the battery bank can absorb at a certain bus voltage.
The bigger bank could absorb more amperage initially, and that's what popped the CPE into overload.
For reference, here is the manual for the Iota IQ/4 control module:
http://www.iotaengineering.com/pplib/IQ4manual.pdfWhere it says (last page):
"BULK STAGE - During this state,
the charger will operate either at Full Current output or Constant Voltage output depending on the discharged state of the battery. A discharged battery will dictate the voltage and force the charger into
constant current operation. As the battery charges, the charger
transitions to a constant-voltage operation. This BULK STAGE will continue for either 225 minutes or until the battery voltage reaches the “High Trigger” value (whichever occurs first). At this point, the BULK STAGE will operate for another 15 minutes before switching to the ABSORPTION STAGE.
ABSORPTION STAGE - This state is limited to 480 minutes (8 hours) during which the charger will operate either at Full Current output or Constant Voltage output depending on the discharged state of the battery. During Full Current output, the charger is providing its full current rating and will slowly increase the battery voltage to the “Absorption Stage” voltage. At the end of the 480 minutes, the charger will revert to the FLOAT STAGE.
FLOAT STAGE - This charge state holds the batteries at
Constant Voltage for a period not longer than seven days. During this state, the charger not only floats the batteries, but it can also provide load current up its maximum rating for other loads without depleting the battery capacity. The FLOAT STAGE will end when either the battery voltage drops below the “Low Trigger” point or at the end of seven days when the IQ4 initiates an equalization stage to remove sulfate layers from the battery plates. In either situation, the unit exits the FLOAT STAGE and enters the BULK STAGE."
That's the correct behavior for a proper multi-stage charger.
As far as I can tell from the online documentation and the product manuals, neither the PD nor the WFCO does
constant current charging at all.
Thus they are not true multi-stage chargers. What they actually are, are variable voltage power supplies.
EDIT: Forgot to make links clickable. Fixed.
EDIT 2: For additional reference, here is the manual for a Samlex SEC series converter/charger. This is the unit I have decided to buy to replace the old Schumacher battery charger in my camper:
http://www.samlexamerica.com/customer_support/pdf/Manuals/SEC-1215A_SEC-1230A_SEC-2415A_Switch_Manual.pdfNote that on Page 4 it says:
"STAGE 1 -
CONSTANT CURRENT OR BULK CHARGE STAGE
When the battery is low, it will try to draw larger charging current. The charger senses the current draw and limits this to the maximum permissible value (15A for SEC-1215A / SEC-2415A and 30A for SEC-1230A). Bulk charging takes place at this constant current. In this condition of constant current, the voltage measured at the charger or battery terminals will be the battery's own voltage. The constant current injected into the battery starts restoring the battery capacity and it's voltage starts rising. When this voltage approaches the threshold of battery "gassing", termed "boost or absorption voltage", the charger automatically switches over to Stage 2 - "Boost or Absorption Stage". The value of this voltage depends upon the type of battery being charged (See Dip Switch Settings). By this time, approximately 80% of the battery capacity will normally have been restored (Note: The percentage capacity restored till the point the battery reaches the boost or absorption voltage is inversely proportional to the value of the bulk charge current.)
STAGE 2 -
CONSTANT VOLTAGE BOOST OR ABSORPTION STAGE
As explained above, when the battery voltage approaches the point where battery "gassing" can begin, the charger automatically switches over to the "Boost or Absorption Stage". The charger applies a constant voltage whose value depends upon the type of battery selected ( See Dip Switch Settings ). This controlled overcharge restores the balance 20% of the capacity in a minimum amount of time. As the capacity is fully restored, the charging current starts reducing. When the current reduces below the preset threshold, the charger automatically switches to the "Float or Maintenance Stage".
STAGE 3 -
CONSTANT VOLTAGE, FLOAT OR MAINTENANCE CHARGING STAGE
As explained above, as the charging current drops below the preset threshold ( 1.5 to 2 amps for SEC-1215A / SEC-2415A and 2.5 A to 3 A for SEC-1230A ), it signals that the battery is 100% charged. In this "Float or Maintenance Charging Stage", the charger outputs a constant voltage of 13.5 V for 12 V system and 27 V for 24 V system. This helps in maintaining 100% capacity of the battery and also compensates for self discharge. The battery can remain connected in this stage indefinitely without the risk of overcharging or excessive loss of electrolyte."
