What Size Replacement Converter?

[JohnBarth]

Hi folks. I have a 1987 25' Sovereign we bought about 4 years back. Most of the components are original. I haven't pulled my gaucho yet, but I believe the univolt is original equipment. Not making much noise, but it appears to be cooking my batteries. I had two Interstate SRM-27 12 VDC batteries in parallel that came with the trailer. A week before going to a rally I pulled the batteries, topped off the water and replaced in the trailer plugged in to shore power thru 30 A plug. After a few days later they load tested good. When I got to the rally about 70 miles away we had no AC hookup, so I figured no problem to run my fridge and water heater pilot light/gas solenoids, water pump, a few lights and vent fans. The batteries were not up to it. A couple nights ago I pulled the batteries and both were low on water again and load tested weak (well one was weak and the other was dead). The batteries were also very warm to hot when I took them out of their storage cubbies - outside temperature was mid 80's.

So before I put the new batteries in I want to make sure my univolt won't kill them. I need to pull out the gaucho couch to check it, but I'm thinking its probably worth the money to get a new modern multistage converter like Randy sells.

So here is my question - what size converter do I need (ampere rating, not physical size)? I want to be able to boondock/drycamp for a few days. I've bought replacement 12 VDC batteries with greater amp-hour rating (105 A-hr each) than the old Interstates, and I might later go with two 6 VDC golf cart cells in series (like I put in my old popup. It could run off those batteries for close to a week). Also considering some solar later on.

How many amps does my converter need to put out to keep my batteries ready to run a few lights, water pump, pilot lights/igniters/gas solenoids for water heater and fridge, two fantastic fans, bathroom and kitchen vent fan, furnace pilot/solenoid/igniter and fan if it gets cold and jack when its time to hitch back up? I have asked Randy but he is a busy guy running his business and answering lots of questions, thought there is probably someone out here with a similar trailer who already knows the answer. Thanks!

[68 Overlander]

We normally base it on length of coach and number of batteries to be charged taking into consideration what was there before and any other DC using accessories that might have been added. The most common by far is 55-60 Amps. That would power the normal DC accessories (Lights, water pump, a couple fans, radio, furnace fan, etc) in a 25-31 foot Airstream with plenty of power left to charge and maintain a pair of batteries. I had a 60 amp unit in my 76 and 81 model 31 footers and never needed more and a 55 would have been fine too.

[A W Warn]

Per Randy's recommendation, I installed the PM4B60 in my 25' Safari in May 2014. It was a quick and easy install. It is very quiet running unit. Now I leave my trailer plugged in 100% of the time, unless I'm camping. Since the install, the batteries have only needed water once per year. I'm happy!

ps:
With the extra amperage output of the 60 amp converter, when we are camping without hookups it takes less run time on the generator to charge the battery.

[68 Overlander]

Originally Posted by A W Warn

ps:
With the extra amperage output of the 60 amp converter, when we are camping without hookups it takes less run time on the generator to charge the battery.

It's not necessarily the extra 5 amps but rather the tweaking of the charge profile we insist on that sets the Boondocker apart and my trip to Progressive Dynamics (Yes I met the nerds face to face and they are really cool dudes) was the reason users have a remote option for the 4655 now that doesn't need spliced. Marshall, MI has the best Denny's in the country if you ever travel I94
It's a fine line between fast charging and battery longevity that every manufacture strives for and we try and help them when they will listen to the field. Marketing is marketing but customer testimonials are what drives the train so thanks for that. If I spent my day in the weeds comparing this and that, I wouldn't be here, that's for sure.

[Rgentum]

For installation instructions & videos for installing a 8955 converter, go to:

http://www.bestconverter.com/Magnete...Kits_c_64.html

and click on Installation Photos

In my prior note, I said I had installed a 4655; in fact, it was a 8955.

[JohnBarth]

Thanks everyone for the replies and advice. Pulled my old converter today, its a "TRIAD-UTRAD" TU-750-6 converter-charger. 50 amp rating. Also cleaned out the mounting area - lots of aluminum shavings and rivet shafts (factory presents I guess). Wiring all looks good, no evidence of overheating or damage. Big cables, too, at least AWG 4. Ordered a PowerMax PM4B-60 from Randy. Plugged my old converter in the garage and measured 13.5 VDC at the output (no load).

[midwestmn]

please help me with a converter question. i have a 94 B VAN and the converter makes a noise. I shut it off and on and the noise stops most of the time. Sometimes it starts all over again. What does this mean? Do I need a new converter, batteries or ???
Thank you.

[68 Overlander]

Originally Posted by midwestmn

please help me with a converter question. i have a 94 B VAN and the converter makes a noise. I shut it off and on and the noise stops most of the time. Sometimes it starts all over again. What does this mean? Do I need a new converter, batteries or ???
Thank you.

Hi Mid, What is the make and model of it? In 94 you were in the transition era of modern switching converters that make no noise except the cooling fan when running and older transformer types that can and often do hum.

[MelGoddard]

I talked to Andy at CanAm today, about what converter to teplacevwith; and he said not to bother.
The Parallax 7300 on my FC puts out 13.3 V. and therfore would not overcharge the batteries.
My manual also says not to disconnect the batteries Presumeddly to absorb any voltage spikes.
In storage, I have a timer set for two hours/day to maintain them. Over the years, seems to work.

[lewster]

Once again, look at ANY battery manufacturers charging requirements and they all agree......... continual single voltage charging is not what they recommend for proper charging of their product!

You might not boil the batteries, but certainly aren't charging them properly either. 🙄


Lew Farber

[68 Overlander]

What Lew said. It's fact guys and gals.

[Naper]

Originally Posted by lewster

Once again, look at ANY battery manufacturers charging requirements and they all agree......... continual single voltage charging is not what they recommend for proper charging of their product!

You might not boil the batteries, but certainly aren't charging them properly either. 🙄


Lew Farber

I learned something today. I always thought a multi stage converter charged on demand with a constant voltage and varied the amperage based on demand. I will admit this whole converter thing has me baffled. I am a car guy and in cars the charging system charges the battery when it needs to be charged one voltage one amperage and there doesn't seem to be any drama, batteries last for years.

[68 Overlander]

Naper, You described basically how the single stage units work...constant voltage and varied amperage but the current is controlled by the internal resistance of the batteries instead of amp stages. Voltage being the 'force' it can become difficult to overcome the resistance so up the voltage goes (boost). Some gassing is good but that is why they time out and drop back to their nominal voltage.
Batteries do last for years in cars because they are rarely discharged and constantly being maintained. No drama there you're right

[Curly777]

I too installed a PM4B60 but only after calling Randy and seeing what he thought I should use. My wet battery was engraved with "2010" (PO must have had a new engraver as many things are engraved) which I assumed meant that the battery was 6-years old. So I replaced it with a glass matt that I purchased locally. The resulting two trips have allowed me to have the very comfortable feeling that I can forget about the electrical system for a good long while.

[JohnBarth]

Well I received my PM4B-60 PowerMax from Randy (in two days instead of three) and installed it no problems. Randy answered a couple questions I had right away. I also installed my new group 31 Duracell batteries. Verified with my DC clamp on ammeter that the initial charge (about 14 A) tapered down after less than an hour. I also replaced my old tongue jack that was slowly dying - although the new converter and batteries did breathe some new life into it. The PM4B-60 PowerMax is silent and cool. The fan never did kick on so I got bored and reinstalled the gaucho coucho and called it a day.

Next electrical upgrade will be LED lights - I found my old automotive style bulbs are drawing 1.5 A each!

[68 Overlander]

Thanks John. FYI the part numbers on the Boondockers have been changed to make it easier to understand the models. For example the PM4B-60 is now simply BD 1260 (12 volt, 60 amps) etc. Many have inquired so thought I would clarify here. There might be a few of the old part numbers floating around but there is no difference.