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ExRocketScientist

Laurel, MD

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Posted: 01/06/12 07:00am Link  |  Print  |  Notify Moderator

There is nothing wrong. This is normal. What is happening is that the converter is a multistage converter. When the voltage is around 13 volts that is float mode. But when you draw enough power, it fools the converter into thinking the battery needs charging, so it goes back into absorption mode, which is a higher voltage, typically between 14 and 14.3 or 14.4 volts. When it does this, motors will also speed up (exhaust fans and furnace blowers).

The only downside is this can lead to overcharging your batteries, which will reduce their life.


ERS

OldF**t

Crossville, TN

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Posted: 01/06/12 07:12am Link  |  Print  |  Notify Moderator

ExRocketScientist wrote:

There is nothing wrong. This is normal. What is happening is that the converter is a multistage converter. When the voltage is around 13 volts that is float mode. But when you draw enough power, it fools the converter into thinking the battery needs charging, so it goes back into absorption mode, which is a higher voltage, typically between 14 and 14.3 or 14.4 volts. When it does this, motors will also speed up (exhaust fans and furnace blowers).

The only downside is this can lead to overcharging your batteries, which will reduce their life.

+1 This is the way my PD converter works and if it is in storage the converter goes into boost mode every 21 hours or so for 15 minutes. This is documented in the product manual.


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boatwhyteh2o

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Posted: 01/06/12 10:34pm Link  |  Print  |  Notify Moderator

I just went to this documentabout WFCO converter/chargers."Bulk Mode: When the converter senses that the RV system voltage is
less than 13.2 Vdc (equivalent to less than 50% of battery charge) the
converter will automatically go into the “Bulk mode.” In this mode, the
output voltage of the converter will switch to 14.4 Vdc for a maximum
of four hours. If the converter cycles between “Absorption and Bulk
mode,” there could be a shorted battery cell or other issues." This is not the only place the document uses 13.2 Vdc which I think is an error. 12.2 Vdc is close to 50% battery charge 13.2 Vdc is a full charge. Also "other issues" is pretty broad, probably means short somewhere in the system or defective converter. It's almost like it IS switching at 13.2 instead of 12.2 Vdc. Any thoughts?
brooks

ExRocketScientist

Laurel, MD

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Posted: 01/07/12 01:16pm Link  |  Print  |  Notify Moderator

I think that documentation is written with the assumption that there is no load on the batteries. When you have a load, it messes up the "algorithms" used to control the multistage chargers.

The way around this is to have two units and a set of switches to isolate parts of the system. When you have power, you set the switches so that one charges the batteries while the other supplies power to any loads.

boatwhyteh2o

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Posted: 01/07/12 06:49pm Link  |  Print  |  Notify Moderator

I also found a long long thread that engineers this to death.
thank you, brooks

BFL13

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Posted: 01/07/12 07:44pm Link  |  Print  |  Notify Moderator

boatwhyteh2o wrote:

.... It's almost like it IS switching at 13.2 instead of 12.2 Vdc. Any thoughts?
brooks


You missed that the converter is on at this time, so the system voltage is in the 13s not in the 12s like when on battery. So the battery has to be low enough for the converter to "see" 13.2v at the Dc fuse panel where the battery wires come to from however far. If the distance is too great and those wires too thin, then the converter will not "see" 13.2v even with the batteries at 40% SOC and will stay at 13.6v

This is the problem with WFCO and others like it, which require short fat wiring to the battery to work right. PDs have a boost button /Charge Wizard (as do WFCO 100ampers) so you can get 14.4v instead of 13.6v on that too long too thin wire, which helps speed up charging. But it cannot usually make up for the wires being still too long and thin compared with mounting the converter close to the batteries on short fat wire.


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boatwhyteh2o

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Posted: 01/07/12 09:08pm Link  |  Print  |  Notify Moderator

Thank you, I'm going to take some voltage readings like the OP did. My batteries seem good only because I have operated the slide 7 or 8 cycles and was able to hitch and nothing seemed to slow down. I know the 2 group 24's are to small but I can't yet afford a couple of six's like I had on my last trailer. It just seems wrong that the WFCO's fan kicks on and the light's go bright for maybe 1/2 hour. The fan goes off on the converter and the lights go dim for 1/2 an hour. This cycle goes on and on all the time the lights are on. Parked in front of the house loading, or camping with hookups. It drives me batty, all night long bright-dim bright-dim till the lights are turned off.
thanks again, brooks

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