Charging trailer deep cycle batteries

[Dalo]

Hi all, I have a 2004 HR Alumascape which has given me 18 years of fun. We mostly dry camp. Usually I run the 2000W Yamaha generator every 2 or 3 days for a couple of hours to keep the batteries charged. I have read many comments here about older converters not being very good at charging the two deep cycle batteries. My converter is the Parallax 7355. So far, after 18 years this has worked okay for us but I just had an idea- What if when I fire up the generator and plug in the trailer power cord I also hook-up a 10amp variable rate charger connected directly to the battery posts. Would not this shorten the run time needed to bring battery charge up?

[pianotuna]

Dalo,

Another route would be to get an inverter/charger. I can do 127 amps from mine on a 15 amp outlet.

[Dalo]

Thanks for all your responses. Been reading everything I can find re: Progressive Dynamics and multi-stage converters. Reports were good. Thanks Skibane for the advice on portable solar panels. Since we try to find a nice shady spot to park the trailer a portable panel would work for us. Thanks everyone.

[time2roll]

Dalo wrote:
Thanks. I am looking at going with the Progressive Dynamics lower section replacement. This will have to wait until I return from this trip in 2 weeks. Does anybody know if while camping and the generator is running could I safely Hookup a 10amp variable charger to battery posts at the same time as the converter is plugged in via the trailer power cord?

Yes this will improve the charging speed and battery health. No downside.

The PD replacement will be a huge improvement.

[Skibane]

Dalo wrote:
Haha, yes we get a lot of sun. Actually we are heading out Labor Day for two weeks and usually try to get a shady spot.

I like parking in the shade, too - Keeps the interior a lot cooler.

I use a portable solar panel to recharge the batteries - It can be moved to "follow" available sunlight throughout the day, without moving the RV out of the shade.

Solar also works great in tandem with a generator - Basically, you run the generator for a little while in the morning to get a lot of "bulk" charge back in the batteries, and then shut it off to let the solar panels gradually finish off the charge as the day progresses.

[wa8yxm]

Fisherman wrote:
Noooo, you're in California, you have to use solar panels.

FUNNY Good but Funny.

To the original poster.

IT might. or it might not.. Here is why
The Parallex puts out 13.6. so your "Variable rate" charger may sense "Charged" and switch to float voltage as well.

A better option would be to upgrade the parallex.. A 7300T (T for Two stage (Timed) would recharge faster.

or a Progressive Dynamics 4600 to replace teh Guts" of the parallex

or a PD 9200 stand alone.. Get one with a plug and use it plugged into the Honda direct and let the Parallex think you are still boondocking.

Oh to do a good proper recharge job. Assuming the converter has is rated at about 1/3 the C-20 capacity of the batteries.. Six hours is about right. (Of course if they are not that far down the time is reduced) I'm kind of biased toward Progressive Dymanics.. but I've been to their factory (Mine needed replacement).

[Gdetrailer]

Should work, lots of folks often do this because they don't want to spend the money on a converter upgrade and often will use portable multistage "smart" battery chargers to speed up charging. Generally they will use 20A or higher smart chargers, 10A might get you done a few minutes faster..

I know from having a old school non smart 10A charger it can take quite a few hrs (8-10hrs) to overnight to fully recharge a dead car battery..

Just make sure you do not accidentally connect the portable charger cables backwards..

[Lwiddis]

Two or three hours running a generator through your converter every two or three days isn’t filling your batteries even with a 10 amp charger. Wet batteries should fully recharged daily for maximum life. Despite Fisherman’s quip, if you are serious about recharging for the batteries health, want no more generator noise or maintenance and for “full” power when camping, learn about and install solar.

[Dalo]

Thanks. I am looking at going with the Progressive Dynamics lower section replacement. This will have to wait until I return from this trip in 2 weeks. Does anybody know if while camping and the generator is running could I safely Hookup a 10amp variable charger to battery posts at the same time as the converter is plugged in via the trailer power cord?

[Gdetrailer]

Parallax 7355 is a fixed voltage or single stage converter, it will be preset to around 13.6-13.8V. The charge current tapers quickly because of the fixed output voltage of the converter.

As the battery recharges the battery voltage rises, eventually it will get up to 13.6 or so volts and when that happens the charge current drops down to .5A or less..

If the converter had a higher output voltage then you would see a higher current.. But then you would have the issue of too high of voltage for normal use and the result is boiled to death batteries.

As it is with the fixed voltage if you left it plugged in 24/7/365 you would be burning up batteries constantly.

Your 10A charger may help some depending on the max output voltage but I doubt it will be enough to make it worth the hassle to hookup and disconnect every time you wanted to recharge.

Might be a good time to consider a multistage converter?

Something like a PD92xx with Charge Wizard.. With Charge wizard it can deliver 14.4V in bulk mode.. You can get PDs as a lower portion replacement (you pull out the old Parallax and the replacement fits in the same bay) or you can buy a deckmount version you can mount nearby to the breaker and fuse panel and disconnect the old converter.

The nice thing about modern multistage converters is they can go into storage mode (13.2V) when not in use, into a higher voltage 13.8V for in use or Bulk mode 14.4V as needed.. Storage mode saves a lot on water use, cuts down on boiled to death batteries.

[Microlite_Mike]

The Parallax 7355 converter is an Old School, single output voltage converter which will do an OK job of powering the RV's 12v system but is lacking for battery charging.

It will provide a continuous voltage of 13.6 volts regardless of battery state of charge. This means too slow for charging a discharged battery and too high a voltage for maintenance or float charge. On the latter this means battery will need more frequent "watering" to keep from going dry.

I would consider replacing the converter with either a deck mount or replacement section for the Parallax power center (if so equipped) from Progressive Dynamics. It will provide higher (14,4 volt) charging voltage for an "empty" battery, 13.8 volts for the absorption phase (to get a FULL charge) and then switch to 13.25 Volts for a maintenance/float charge that doesn't cause battery to use a lot of water.

The higher voltage will charge the battery faster and reduce the needed generator run time. On run time, a lead acid battery really needs more than a couple of hours at a time to fully charge. Generally a 100 Ah battery, discharged to 50%, will need 3-4 hours to reach 90% state of charge and another 3-4 hours of absorption charge to reach 100% SOC. Of course this depends on battery temp too as a cold battery will use the initial charging current just to warm the electrolyte.

[JimK-NY]

I don't know anything about your converter model but it is likely single stage which means it charges at a fixed voltage, usually about 13.5 volts. A multistage converter/charger will start at a much higher voltage, around 1.43 volts and then taper off. This means much less time needed for charging and more likely a better charge with longer battery life.

I recommend you check the bestconverter.com webpage and then discuss recommendations with the owner, Randy. He knows his stuff and the prices and services are good and you know you will get the right replacement. I replaced my converter/charger and greatly reduced generator use. Most of my charging is with solar but when that does not work, I still need a generator.

[Dalo]

Haha, yes we get a lot of sun. Actually we are heading out Labor Day for two weeks and usually try to get a shady spot. Just was reading about the Parallax 7355 and still don't understand how to figure the battery charge rate from the converter. It's variable but Parallax states in the manual that it puts out a rate of about .5amp. I know it starts out at a higher rate of charge but quickly drops to .5amp.
Anyone have any idea of how long it charges initially at a higher rate??

[Fisherman]

Noooo, you're in California, you have to use solar panels.