UHaul Converter - Peering Inside

[Thomas G.]

Let me preface this discussion by stating that I'm a mechanical engineer and any errors made are from ignorance, as opposed to malice.

I've wondered if I should replace my old converter on my CT UHaul. I rarely camp with electricity, so I am curious to see how much of a battery boiler this converter is. Today I decided to take it apart and see what is inside.

It appears that it has a split output when plugged in. One circuit isolates the battery and charges it and one circuit powers all the trailer accessories off the transformer's DC output, independent of the battery.

With no battery connected, the charging circuit output is 12.44 volts and the accessories circuit is at 13.47 volts.

With a small jumper pack battery connected at 12.8 v, the charging circuit jumps up to 14.24 volts and the accessory circuit remains fairly steady at 13.41 volts.

Given that a fully charged battery is about 12.7 volts, I would think that the charger circuit output should be closer to a float voltage, like 13.4 volts. There is a small electronic circuit board that appears to regulate charging voltage (circa 1985).

Any thoughts or insight from those of you with more experience?

[Darwin Maring]

I would just go to some place like WallyWorld and purchase one of those batteries that has a 3 year free replacement warranty the not worry about boiling it.

[rabbit]

Tom, I'm not a BSEE and would look foolish playing one here, but here are the three levels of charging voltage of a Progressive Dynamics "smart" charger (PD 9245) with which I replaced the converter end of my Newmark electrical sevice.

Assuming a discharge to 12.4V level, "Boost" (desulfation mode) charges at 14.4V and takes the battery to 90% of full charge in roughly four hrs. "Normal" mode kicks in at 13.6V for another 30+ hrs. at which time the charging current is reduced to the 13.2V of "Storage" (float) and maintained until battery use and discharge triggers "Normal" mode once more. In addition, there is an "equalization" mode which provides 14.4V for 15 minutes at 21 hr. intervals. My multimeter consistently gives me readings .06V under the stated current for each stage which suggests that PD's specs are accurate. The 14.2 voltage reading which you are getting is very close to the agitation or desulfation level for the PD which would make a layman such as myself think that the converter is probably an electrolyte boiler. This seems to be the going skinny on "older" converters.

FYI, I wired with 6awg welding cable to battery (17' run) and to distribution panel from split bolt taps on the main line (about 18"). The contactor on the original rig which presumably handled the "isolation" of outputs is not needed w/ the PD9245.

jack

[mary and bob]

I kept the fuse panel and threw away the rest of it. To answer the original question: I have no idea how it really works, mine seemed to kill the battery rather than charge it. I just installed a PD 4045 converter but have not tried it yet. Before that I was just using an 1150 truck battery and recharging it with a 10 amp automotive charger. The truck battery is staying in place. For our 3 month snowbird trip this winter most everywhere has electric, but the camper was out 3 weeks this summer with no electric available and the battery never went dead being used for lights only.

[Thomas G.]

Thanks for the replies thus far.

Right now I'm thinking that I may just add a toggle switch to over ride the charging when it is plugged in.

All accessories will be running off the converter and if the battery is low, I can flip the switch to let it charge.

If the battery is charged (off the solar panel), I can just let the converter run the accessories and leave the battery isolated.

I don't have much confidence that the electronic circuit shown in the photo above is adequate to protect the battery.

Incidentally I was dreading unbolting it from the floor, but someone (bless their hearts) attached it with stainless steel bolts, which just threaded out.

[rabbit]

Bob, I thought the 4045 was a combination distribution panel/converter. Did you have room for that and the old fuse panel. The 9245 is converter only but was an easy bolton to the case of the Newmark.

jack

[rabbit]

http://www.appliedgmc.com/images/PD9200_Manual.pdf

Wiring schematic for PD 9245. No isolation of charge function from power function that I can see there. Batt and fuse panel are in parallel. Hard for me to believe it's that simple but there it is!

jack

[Thomas G.]

Just to finish this thread - I decided to replace the jumper wire between the charger terminal and the battery terminal in the charger with a toggle switch.

I rarely camp with electricity, but when I do, I can just flip the switch and let the DC converter power the trailer without worrying about the battery boiling.

The solar panel generally keeps the battery topped off nicely. Should I need to charge the battery off 110 volts, I can flip the switch back to the charge position.

If I decide to upgrade in the future, it will be easy to install an intelligent charger / converter in place of the current converter, though I think I'd move it up under the furnace and run heavy wires back to a fuse panel mounted in the same area as the converter is now.

[Pam Garlow]

Reading this (pretty much indecipherable) discussion illustrates to me, just what men must be hearing when women are in a deep discussion about Tulle, Toile, or Crinolines, and whether taupe cushions will go better with cerulean or salmon curtains..... Women really are from venus!

[rabbit]

No kidding! By Tom's final post I too was suffering from vererean strabismus. It's all about complementarity, nuts and their bolts.

jack

[Thomas G.]

Originally Posted by Pam Garlow

Reading this (pretty much indecipherable) discussion illustrates to me, just what men must be hearing when women are in a deep discussion about Tulle, Toile, or Crinolines, and whether taupe cushions will go better with cerulean or salmon curtains..... Women really are from venus!

Pam, what I said (in Male Martian), was that I'm too cheap to install a modern converter.

[rabbit]

The parsimonious solution to the single charge rate battery boiling converter is monitoring and an off switch. Works for me.

jack

[knighth001]

Tom,

I don't currently have a battery installed. (The one I was going to use ended up being toast.) I will be getting one soon hopefully. I was reading all the manuals and looking at the wiring diagrams and have pulled out the 120v outlet box in mine trying to see how it's all wired together.

One thing that isn't clear to me, does the 120v outlet work at all when just running off the battery? (I know if I had a battery this would be answered in about 2 secs.) It doesn't look like to me from the wiring diagrams that the converter would do this.

PO had wired a 120v mini Fridge directly into the 120v outlet and I'm assuming that the fridge won't work without it being plugged into shore power. (which I guess means taking a cooler on a long road trip)

[Thomas G.]

Originally Posted by knighth001

Tom,

I don't currently have a battery installed. (The one I was going to use ended up being toast.) I will be getting one soon hopefully. I was reading all the manuals and looking at the wiring diagrams and have pulled out the 120v outlet box in mine trying to see how it's all wired together.

I'm assuming you still have the 110 volt cord that pulls out the door on the left side.

One thing that isn't clear to me, does the 120v outlet work at all when just running off the battery? (I know if I had a battery this would be answered in about 2 secs.) It doesn't look like to me from the wiring diagrams that the converter would do this.

No, when you are not plugged in, all you have is 12 volts (or so) off the battery (when you install it).

PO had wired a 120v mini Fridge directly into the 120v outlet and I'm assuming that the fridge won't work without it being plugged into shore power. (which I guess means taking a cooler on a long road trip)

I think you've got it right. You could put contained ice in the refrigerator and use it as an ice box

By the way, I decided to leap into the 21st century and bought a smart charger, which I'll replace the above dissected box with.

http://www.ebay.com/itm/Inteli-power...4967c4&vxp=mtr

[knighth001]

Originally Posted by Thomas G.

I'm assuming you still have the 110 volt cord that pulls out the door on the left side.

No, when you are not plugged in, all you have is 12 volts (or so) off the battery (when you install it).

I think you've got it right. You could put contained ice in the refrigerator and use it as an ice box

By the way, I decided to leap into the 21st century and bought a smart charger, which I'll replace the above dissected box with.

Inteli Power 45 Amp Converter Charge Wizard RV PD9245C Progressive Dynamics | eBay

Thanks. That's what I thought. Any idea how many amps the stock converter pulls? I'm trying to figure out why the last time I was camping the breaker was tripping based on what I had plugged in/running. I probably need to turn everything on and get my multimeter out.

I'm thinking of putting in a kill switch for the battery charging for now. One of the manuals references a master switch near the battery meter. Mine doesn't have one. I'd like to put a kill switch there. I'm not sure if the master switch the manual refers to just kills drain on the battery or also kills the charging of the battery (since they appear to be separate circuits)? Did yours have one of these master switches?

I also want to replace the unused ash trays with 12v outlets for charging phones, etc. I'd like to replace the converter at some point but I need to buy a battery first. (Also, need to order the weatherstripping to do my side window. Have to keep my prioritized list!)

[Darwin Maring]

Purchase some drinking water in drinkable sized plastic bottles, freeze them in your home fridge freezer and put them in the camper Ice-A-boxa (Italian for fridge) This way you keep the fridge cool and have drinkable water at the same time/

B 4 you do that, plug in the camper at home and turn on the fridge so it is already cold when you introduce the frozen water bottles.

[Thomas G.]

Originally Posted by knighth001

Thanks. That's what I thought. Any idea how many amps the stock converter pulls? I'm trying to figure out why the last time I was camping the breaker was tripping based on what I had plugged in/running. I probably need to turn everything on and get my multimeter out.

Sorry, I've never measured the draw of the converter alone, but it should be no where near tripping the 15 amp breaker. I'd more likely expect an air conditioner or a heater to trip the breaker.

I'm thinking of putting in a kill switch for the battery charging for now. One of the manuals references a master switch near the battery meter. Mine doesn't have one. I'd like to put a kill switch there. I'm not sure if the master switch the manual refers to just kills drain on the battery or also kills the charging of the battery (since they appear to be separate circuits)? Did yours have one of these master switches?

I installed a master cutoff switch right at the positive terminal of the battery. I also installed a small toggle switch between the two left terminals in the converter to manually control the battery charging.

I also want to replace the unused ash trays with 12v outlets for charging phones, etc. I'd like to replace the converter at some point but I need to buy a battery first. (Also, need to order the weatherstripping to do my side window. Have to keep my prioritized list!)

I pulled the ash trays and mounted a cigarette lighter type power point in the recessed pocket for phones, etc.

[mmeyer]

I believe I have the cut sheet for the Converter/batterychargers and that they were made by Newmark. if so it indicates that all RA(ones that charge a battery and convert 120 to 12V) series units pull either 3.3A for a 20A unit , 4.6A for a 30 and 6.2A for the 40 amp unit. I believe the 20A unit was furnished based on the picture of Tom's transformer. Can't check as I sold mine and went to a Progressive Dynamics unit which I believe is way better and way lighter.
Michael J

[mary and bob]

I think what is happening with Sean is that he is overloading the original 110 breaker with what he is using. Ours had a 15 amp breaker that was just a little push pin on the 110 outlet that was on the end of the overhead cabinet. It didn't take much load to trip it. I scrapped the original converter and installed a PD 4045 converter, rewired everything 110 and 12 volt, and am very happy with the results. I also installed a master disconnect on the battery with the lever mounted on the face of the bed support just ahead of the battery box.

[knighth001]

You're right Bob, that's what's happening. I need to figure out how much the fridge is drawing. and my wife did have a coffee maker plugged in running too as I recall. and maybe something else.