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Old 06-17-2010, 12:24 PM   #1
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Charging Coach Batteries with gen.

Hoping some of you electrical experts can advise me!

I have just ordered an EU2000i to take on future trips.

It comes with a DC charging battery cable.


I am wondering though, which is the best way to charge the trailer batteries when needed:

- direct connection of the generator's 12v charging feed?

- use of a "smart" 15 amp 110 charger I have, connected to the generator?

- just plug in the trailer and allow teh converter/charger to do its thing?


I just took a look at the literature that came with our trailer, it has a
Parallax 7400 Series Converter / Battery Charger. I'm not sure which specific model, 7430, 7445, 7455, 7465, as the trailer is not at my home for me to check.


However, the brochure indicates that even the 7430, the smallest model, has a 30 amp DC output.

The brochure goes on to say that "Your Parallax 7400 series power converter is capable, of delivering its full rated output to the batteries, if needed, but will taper off to a few hundred milliamps when the batteries are at full charge.


Seems to me this makes my decision easy, I would be best to just use the trailer's converter/charger rather the either using the generator's 12v cable, or using a separate battery charger connected to the generator.



Does this seem right?


Something else I wonder about.

Since the brochure says that the Parallax will still supply "a few hundred milliamps" to the batteries when fully charged, does this mean it is not as good for the batteries as some other units now available?

I thought they went down to virtually zero current when teh batteries were charged?

I recently installed a couple of quick disconnects to my AGM batteries with the idea that any time we were camped for more than a couple of days on 110 power, I would take the batteries off line to protect them.

Is this a waste of time with just a "few hundred milliamps," or still a good idea for the longevity of my batteries?

Thanks for any advice!



Brian
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Old 06-17-2010, 12:34 PM   #2
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I'd say option 1 (using generator's 12 volt output) is the least effective.
The other two is a toss up, basically try and see which works best.

The Parallax is single stage converter charger, plenty of amp capacity but high 13 volt range (best initial charge rate is in mid 14 volt range). If your smart charger were a 40 amp model I'd say it would be clear cut winner.

I have AGM batteries and will disconnect them from the Parallax when fully charged, but only in high temperature situations.
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Old 06-17-2010, 03:08 PM   #3
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this is covered in your other thread from days ago...

and in 100s of other threads here.

charging DIRECTLY from the genset is NOT recommended.

the reasons are posted elsewhere.
________
the ONBOARD charger/converter (P-lax) is without a doubt the best approach to charging the coach batteries...

from the options listed.
________

the C/C should be a 55 AMP model in your unit (unless not oem)

the p-lax 74xx series (used in classics) are NOT 1 stage chargers.

this has been posted incorrectly here 100s of times

to SELL chargers or encourage UNneeded purchases or promote confusion.

bambi/safari/international model trailers typically come with the 73xx series p-lax.

which is different.

the 74xx series lacks the 'adjustable bulk' charging stage and the float trickle stage isn't 'smart' but it's there.

UNfortunately if the genset ordered the h-2000 with the 12v direct outputs...

the unit will NOT have the new 30 amp plug...

for a few dollars more the companion series 2k is a better first option genset.

the 12v/dc output is ok for charging starter batteries (from cars to gokarts)

cheers
2air'
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Old 06-17-2010, 04:51 PM   #4
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Thanks for the clarification, 2Air!

I wondered about whether to order the standard or companion unit, but in the end, thought it might be handy to have the 12v output at some point, and also, I have all kinds of adapters that go from a standard household 20amp socket - which I guess is what is on the EU2000i - to a 30 amp style receptacle that will accept my trailer cable, so hopefully I didn't make a big mistake here!

I think it doubtfull that I will buy a second generator and parallel kit, but it is possible, we ave never tried boondocking, but might ow that we will have the generator. If we like it, then the second unit might be on the cards for the AC.

Silly as it may sound to more experienced RV'ers, I have always had a "House rule" that we only "pee" in the toilet! Stems from my (probably) mistaken view that I would otherwise stand a good chance of having to deal with toilet problems!

Obviously if we decide to try boon docking. I would have to change my stand on this issue!



Now, what do you think about the wisdom of disconnecting the AGM batteries if our trailer is going to be on shore power for several weeks at a time?

Is the minimum current that the Parallax 74xx series supposedly will continue to put out even though the battery is fully charged likely to shorten its life or am I worrying about nothing and shouldn't bother disconnecting the batteries as I have started to do?

Thanks again for your help.


Brian
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Old 06-17-2010, 05:13 PM   #5
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Quote:
Originally Posted by 2airishuman View Post

the p-lax 74xx series (used in classics) are NOT 1 stage chargers.

this has been posted incorrectly here 100s of times

to SELL chargers or encourage UNneeded purchases or promote confusion.


cheers
2air'
Thanks for the heads up on the factory installed converters installed in the Classics. Sorry to give inaccurate info.
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Old 06-17-2010, 05:37 PM   #6
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Quote:
Originally Posted by tpi View Post
Thanks for the heads up on the factory installed converters installed in the Classics. Sorry to give inaccurate info.
No problem from my end, I know everyone does their best to help and I know I have at times passed on incorrect info albeit with best intentions!


Thanks ............ Brian.
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Old 06-17-2010, 08:47 PM   #7
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you will be FINE with the 30 amp outlet but it sure is nice to have it on the genset.

Quote:
Originally Posted by Wingeezer View Post
...Now, what do you think about the wisdom of disconnecting the AGM batteries if our trailer is going to be on shore power for several weeks at a time?...
that would be UNwisdom...

the oem 05 agms in my unit have been plugged in 24/7 when not boondocking for 5 years.

in storage AND long term camping.

while the p-lax isn't a 'smart charger', one can simply USE the batteries and cycle them down/up to mimic this.

the 74xx functioned nicely till it died (from low voltage at the shore/pole) after 4 years of duty.
_________

on top of that, i don't think the 12 systems will operate properly without the batteries connected/in the loop.

i don't think the 12v systems will work using just the converter and IF they did, the voltage they'd see would be ~13.5

cheers
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Old 06-18-2010, 07:11 AM   #8
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Quote:
Originally Posted by 2airishuman View Post
i don't think the 12v systems will work using just the converter and IF they did, the voltage they'd see would be ~13.5

cheers
2air'

Thanks again 2Air!


Actually, the one page description I have of the Parallax 74xx series
says:


"Although the converter is an excellent battery charger, the converter does not require a battery to be connected to it for its proper operation."


As mentioned, I did install a couple of those quick disconnect knobs on the battery terminal so I could take the batteries off charge. I used them for the first time on our last trip and everything seemed to work just fine, just a quick turn or two on the terminal knobs disconnects the batteries.

From your experience though, it seems I don't really need to bother doing this - I guess it doesn't hurt though!


As for voltage, our trailer has a 12v lighter socket in the bedroom and I keep a simple voltmeter always plugged into it just to keep an eye on things. It seems to always read 13.8 or 13.9 volts. (Same whether the batteries are connected to the trailer or not)


Brian.
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Old 06-18-2010, 09:00 AM   #9
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Quote:
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..."Although the converter is an excellent battery charger, the converter does not require a battery to be connected to it for its proper operation."...
ah yes, i'd forgotten this, and have never TRIED using the 12v systems without the lifelines connected.

the charger/converter functions are set up in parallel so yes the converter can function sans cells.

however LEAVING the batteries connected is good for a couple of reasons.

1. float voltage from the unit drops as the batteries reach FULL (i saw float voltages ranging from 13.2 to 13.5 with the p-lax)

2. USING the on board 12 v system (and batteries) will cycle the charger/cells which is a good thing (i think)
_________

given your unit has agms, with lower internal resistance, those batteries can better use the FULL amp capacity of the charger.
_________

early on i considered pulling the batteries regularly as u r...i added Q/dc and nylon straps for pulling.

but given how TIGHT the boxes are and how heavy the batteries are, removal is a pia, so they rarely come OUT of the boxes.

the agms are maintenance free and THAT feature alone is worth the extra cost 2me.

cheers
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Old 06-18-2010, 09:27 AM   #10
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With the disconnect knobs I installed, I need only open the battery doors and give a quick turn on the knobs and the batteries are offline - no need to pull the batteries out, very quick & easy.

I was actually a bit more concerned about AGM batteries maybe getting damaged by being left on line that regular batts.

Parallax say that their chargers will not harm batteries left connected for a long time as long as they are regularly topped up.

The AGM batteries are not capable of being topped up, so I wasn't sure if it may be worse for that type of battery to be left on line for a long time, which is why I opted for the disconnects just to be sure. They are expensive to replace!

I recall you said you had no problem leaving AGM's connected for a very long period though.


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Old 06-18-2010, 10:44 AM   #11
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Both the 7300 and 7400 converters are not required to have a battery in the circuit per manufacturer. Page 3 of this PDF refers to this:
http://www.parallaxpower.com/7400/51...%20rev%20H.pdf

The power output of my 7355 is very clean and well regulated without battery load. Absolutely no static or interference on audio devices running from the 12 volt source. The unit has big filter capacitors. The only advantage I can imagine to having batteries in the circuit would be a measure of protection against malfunction of the converter.

Fully charged AGM batteries can float indefinitely on the charger depending on temperature. Refer to the AGM chart on bottom of page 11:

http://www.eastpenn-deka.com/assets/base/0139.pdf

I disconnect my fully charged AGM batteries in hot weather (90 degrees), but I err on the side of leaving them connected too long vs. quickly disconnecting them. At times I've run on the converter only for several days. There has been no incidence of battery outgassing or other problems with the setup for 3 years.
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Old 06-18-2010, 10:51 AM   #12
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WE don't have AGM batteries, We prefer to turn off the charger instead of disconnecting the batteries. Have installed a switch for that purpose. We also have solar so the charger isn't often used, but we will kick it in for a few hours a day when parked in shade.
Recharging from a generator is best done through the trailers on board charging system. The output from the generator 12 volts is lower and will reqiure a lot more generator time,.
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