Riddle me this

[majorairhead]

We have a Progressive Industries EMS-PT30C.

We have a flying cloud 25a that has the Interstate srm24 batteries, and the stock Parallax 8355 converter.

Now, I got this puppy in USE mode, all internal electrical stuff is off see, except that lp gas detector, and maybe the light of the microwave clock.

So, I'm plugged in to a 110 line, intending to charge the batteries. The EMS-PT30C shows a draw of 5 amps.

24 hours later, I go to check it out, and the EMS-PT30C shows a draw of 0 amps.

So wazzup with that? You think those batteries draw 5 amps to charge, then when charged cease to draw amps?

Check out the faqs here for some interesting reads:
http://www.parallaxpower.com/faqs

majorairhead

[Lumatic]

Not familiar with that particular Progressive Dynamics model. 24 (hrs) x5 amps=220 amps. I would guess the converter turns off charging when charged. Do you have a battery gauge?

[dkottum]

That converter continues to apply about 13.4v even after the batteries are fully charged. Once fully charged the batteries do not draw any current, 0 amps.

That converter is okay if you have external power to it and are using the batteries while camping. If you leave it hooked to external power with no battery use it will ruin the batteries with the constant higher voltage. Or you could place the Battery Disconnect in STORE position when hooked to external power and no battery use, will will isolate the batteries from the converter/charger.

Only the propane detector will still be connected to the batteries, and it will draw the batteries down eventually. We put a switch on the propane detector power supply wire.

[68 Overlander]

The Parallax nominal output is 13.8 VDC. Always has been and probably always will. The amperage/current applied to the battery bank is controlled by the battery, not the converter. It is capable of 55 amps (8355 is a 55 amp unit) and it is a shared load with your DC system. For example, you have 10 amp being used on your DC system, lights etc, you essentially have a 45 amp converter left at that time. (don't confuse this with older types that had separate charging circuits ie 3-6 amps for charging) Modern switch mode converters don't work that way. So...remember the battery controls the current to it by its internal resistance. If it's fully (charged) the converter just hangs out pressing 13.8 volts to it with very little current since it won't let it in. You probably had a nearly full battery when you saw those 5 amps. Best I can tell after you checked it later your batteries were full and the amps noticed at that time was measured at 0. Remember that voltage is still there and your batteries are very likely to start gassing with that 13.8 VDC present. That is why Parallax units get a bad name...They don't drop back to a lower float voltage to prevent excessive gassing after a period of time.
Here is where it gets a little confusing. 13.8 is too much for constant charging, but actually not enough for "fully" charging. You want 14.4+ VDC periodically and yes, even some small amount of gassing to properly charge a flooded or AGM battery. You just don't want it constant. It needs to step down in the 13.6 range for everyday use and then even lower to about 13.2 for float or storage (with daily boost of 14.4 for a few minutes to desulfate)
Doug's comment above is true..when you use your battery, its okay to be in the 13.6-13.8 range when its cycling. Its just when you use little battery power (usually plugged in to shore power) that you get into trouble with a constant voltage of 13.8 like the Parallax.

[majorairhead]

I'm a novice in the electrical department. The responses y'all have given are helpful for sure.

Anybody open that faq linky? If so, check out question 4, and most importantly, anybody care to try and clear up just what the heck is being said in question 9?

I'm most likely going to upgrade some time to a PD4655 but our 'stream is new and still under warranty. I have concerns related to a switch of the converter and warranty claim issues should they arise.

thanks folks

majorairhead

[Lumatic]

Not sure about the EMS PT30C, but I have a "charge wizard" added to my Progressive Dynamics that allows you to override and change charging stages.

[Al and Missy]

The EMS PT30C is a shore power regulator/protector. If he was drawing 5 Amps there, the current into the batteries was much higher, maybe as much as 40 amps, due to the voltage step down in the converter. The input power to the converter will be 20%-30% higher than the output due to efficiency. So 5 amps x 120 volts input is 600 watts. Multiply that by .75 to account for efficiency in the converter and the converter's output power is around 450 watts. Divide that by 13.8 and the converter's output current is around 32.6 amps which is shared by anything running and the batteries as Randy mentioned. Once the battery current drops to a few amps, the converter stepdown makes the input current to the converter so small that the PT30 probably can't display it with its 3-digit display.

Al

[dkottum]

Originally Posted by majorairhead

I'm most likely going to upgrade some time to a PD4655 but our 'stream is new and still under warranty. I have concerns related to a switch of the converter and warranty claim issues should they arise.

majorairhead

We kept our original converter/charger for five years and it worked fine providing 12 vdc electrical equipment in our Airstream. We used the Battery Disconnect Switch in STORE mode to isolate the batteries from the converter/charger.

Earlier this year I had bought a PD4655 and was passing through Airstream Service Center in Jackson Center for routine inspections and maintenance, so I asked them to install it. No problem, they had done this before.

I don't think this install would affect your warranty. You should call Airstream Customer Service and ask them first. If you do, let us know what they say.

[68 Overlander]

Originally Posted by majorairhead

Anybody open that faq linky? If so, check out question 4, and most importantly, anybody care to try and clear up just what the heck is being said in question 9?


majorairhead

I did and have argued with them for years. Marty Redd is who you will likely talk to if you call their tech support.
Question 4 is mostly correct. They leave out the fact that 13.8 VDC will overcome most batteries resistance and continue to gas the batteries after charging is complete. 13.2 would be better for storage as it will not overcome that "full battery" internal resistance.
Question 9 attempts to argue that the converter doesn't know the difference between the battery resting voltage and the voltage of the DC system when they could be the same. That is only true if the batteries and system voltage always match. As soon as you unplug for a night of boondocking for example, and then reconnect to shore power or a generator, the battery voltage will be lower and the converter should recognize that and enter a boost phase. There are other examples.

[68 Overlander]

Originally Posted by Al and Missy

The EMS PT30C is a shore power regulator/protector. If he was drawing 5 Amps there, the current into the batteries was much higher, maybe as much as 40 amps, due to the voltage step down in the converter. The input power to the converter will be 20%-30% higher than the output due to efficiency. So 5 amps x 120 volts input is 600 watts. Multiply that by .75 to account for efficiency in the converter and the converter's output power is around 450 watts. Divide that by 13.8 and the converter's output current is around 32.6 amps which is shared by anything running and the batteries as Randy mentioned. Once the battery current drops to a few amps, the converter stepdown makes the input current to the converter so small that the PT30 probably can't display it with its 3-digit display.

Al

Great point and EMS systems are a good way monitor. Unfortunately the portable models have the display on the unit so you have to visit the pole to read it. The HW models have a remote that you can read from inside the Airstream. Both have advantages regardless.

[majorairhead]

I appreciate the candid replies. I have our unit winterized and in a shed.

Do y'all think I could hook up a battery tender to the batteries as they are, should I disconnect a cable (neg. pos. or both?), or should I haul those batteries out and put 'em in my garage and put a tender on 'em there?

And since I'm a cheap Pennsylvanian of German descent, what battery tender would y'all recommend, keeping in mind my frugality?

[SteveSueMac]

Frugality considers total cost. You can "cheap out" but if that costs you more later, that's not frugal 😀

I don't think this is the exact model I purchased 5 years ago but I take my batteries out of the trailer and put them on this in my basement for the winter :


https://www.amazon.com/Battery-Tende.../dp/B000NCOKV0

Good luck!

[68 Overlander]

Originally Posted by SteveSueMac

Frugality considers total cost. You can "cheap out" but if that costs you more later, that's not frugal ��

I don't think this is the exact model I purchased 5 years ago but I take my batteries out of the trailer and put them on this in my basement for the winter :


https://www.amazon.com/Battery-Tende.../dp/B000NCOKV0

Good luck!

I don't think that is necessary but you can if you want to. I assume you don't have shore power where you store the Airstream or have the Parallax converter and are afraid to. I get that.