motor home generator stuff

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aeh56

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Onan 5500 generator in a 32 ft Thor MH with 2 slides.Not totally sure of year but around 2010.
Anyone who knows these rigs maybe you can fill me in on some stuff.The external storage deep cycle 12 volt batts are in parallel and about 200 ah total. Weisse VRLA replacing the Trojans 31s that only lasted 2.5 years. About how many amps does the stock factory charging system send to these? I know it sends some when the rig is driving and some when the generator is running...about how much for each? Is it hard to replace the stock charging system with a more modern system and transfer switch so the charging is more efficient and you could use lithium batts if you wanted? Would it very difficult to change the charging to 24v or 48v with 24v or 48v batts and still keep some of the old 12v load wiring?Or would you certainly want to redo the appliance and stuff with a revamped elect. system...?
What do you know about this?Are there any places in the SE that Really know RV wiring and can consult and work on it with qualified personnel?
 

Mark_K5LXP

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It would be useful to know just what the goal of this "revamped" system would be. Some folks go with lithium for better efficiency, or increased capacity. Higher voltage systems are typically used for higher power outputs or charging from large solar arrays. It can be done in an RV but you'd have to add a converter to operate your 12V equipment. It's not a matter of if any of these things can be done, it just comes down to deciding the best platform for what the end goal is. And, deciding if that cost is worth it.

Mark B.
Albuquerque, NM
 

Ex-Calif

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The Onan Generator outputs AC current. That plugs into a charger/convert of probably 40amps. That capacity is split among the 12 volt circuits being used and the battery demand for charging.

The engine probably has a 60 or 80 amp alternator. with the same deal. Capacity is shared among car load, MH load, car battery demand for charge and house battery demand for charge.

My wildassed guess is that you have 20-30 amps available all the time for battery charging.

I am reading between the lines and guessing you were not happy with your Trojan life of 2.5 years and are looking to do something different?

A battery monitor would go a long way towards answering the consumption and charge questions.
 

Mark_K5LXP

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I would add that Trojan makes very good deep cycle batteries. If they came up short, then a review of how they're used is in order because they didn't die, they were murdered.

Mark B.
Albuquerque, NM
 

Gary RV_Wizard

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The generator doesn't directly charge anything - it merely provides 120vac power to the coach, just like shore power does. A typical 12v converter/charger for a motorhome like yours would have a capacity of 40-55 amps, which handles both current 12v power demand and battery charging. Theoretically all the amps could be charging if there was zero other demand (no lights, for example), but in practice that never happens. Nor can the batteries accept a really high amp rate except when nearly dead.

If you would identify the brand & model of the converter/charger, we could probably give exact numbers. Your coach probably has the converter integrated with the power panel (breakers & fuses), so that would be the make/model.

Agree with Mark - those Trojans were murdered. You should try to determine what happened, e.g. abusive use, faulty charger, improper off-season storage, etc., and correct that. Otherwise the new batteries will soon be goners as well.
 

aeh56

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Florida
When the Weisse were shipped to me they were very low.
The Onan was on for about 8 hours and got them to 13.3.
I hope an additional 2-3 hours will take the to full. So its hard to believe they were getting even 20 amps and nothing else was being used except a 9 inch AC fan that blows exhaust from under the coach that comes from the Onan. What is a good batt monitor that I can install to show everything going on with the batts. With long leads to route into the coach from the batt box?
The woman who owns this coach and has major health issues
lost her fridge because of the batts going bad.And the thermistor. A new one is coming.Norcold fridge /freezer standard size for these coaches. And one thing I thought was incredibly lame of Thor is that the slides only go out if the battery is over 13.7v. What is that????? Why won't the generator
push them out? Could this be changed??This owner is almost disabled and a full timer who camps in the National Forest to save money. I need to help get this rig right quick. So far I got her new batts. Got rid of a destroyed roof ladder, changed genny oil and sealed a small leak with that super sticky exterior tape. It works good.
btw if her Norcold fridge goes out permanently what is a good replacement, non factory, for it? It runs on a little propane and electric but I don't understand the set up really. I need to so I can help her out. She refuses to adopt a different lifestyle that would be much better for her health issues.
 

Mark_K5LXP

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If the Weisse (sp?) batteries are nominally 200Ah, a typical 50A converter (in a 2010 model) should've been able to bring them up to full or nearly so in 8 hours. The measurement of 13.3V can mean it hasn't completed the bulk phase yet, or it did complete and the converter switched to float. Watching the battery voltage after AC is applied should show it reaching absorb voltage (~14.4V) and it should hold that for the prescribed absorb phase duration (2-4 hours depending on the converter).

if her Norcold fridge goes out permanently what is a good replacement, non factory, for it?

I thought a new one was already coming? Low batteries will not cause a refrigerator to fail. Quite possibly a coincident issue but the worst that would happen is the control board would no longer function and the fridge would just shut off. Once power is restored it will pick up where it left off.

If the slide specifies a minimum of 13.7V then it's implied the slide may only be operated with the engine running or on shore/genset power. I've seen references to operating the slides that way because it's better for the motors (and it generally is) but it would be interesting to learn if a manufacturer has made it a requirement.

Mark B.
Albuquerque, NM
 

Gary RV_Wizard

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Becasue of numerous low voltage problems with slides and leveling systems, the RVIA construction standards now call for the slide motors in a motorhome be driven from the chassis battery(s) and operation is recommended to be with the engine running. To put some teeth into the recommendation, I've heard that some rigs now require the ignition to be ON to operate the slides (though the engine might not actually be running).

Obviously trailers don't have chassis batteries, so this doesn't apply there. Maybe they recommend plugging to shore power first (when available)? Maybe somebody with a late model trailer could tell us what their owner manual says about that (if anything).
 

Ex-Calif

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When the Weisse were shipped to me they were very low.
The Onan was on for about 8 hours and got them to 13.3.
I hope an additional 2-3 hours will take the to full. So its hard to believe they were getting even 20 amps and nothing else was being used except a 9 inch AC fan that blows exhaust from under the coach that comes from the Onan.
Why are you charging from the generator? Does she not have shore power?

Mark's right. You could be in float or bulk with a 13.3V reading
What is a good batt monitor that I can install to show everything going on with the batts. With long leads to route into the coach from the batt box?

Victron BM712 is a good monitor but pricey.

I personally like the Balmar Smartgauge as it self programs and adjusts to battery capacity reductions.


And one thing I thought was incredibly lame of Thor is that the slides only go out if the battery is over 13.7v. What is that????? Why won't the generator
push them out? Could this be changed??
Gary explained the theory of the case. My question is why the on-board charger is not producing 13.7V+?

With the generator running and you are only getting 13.3V on the bus you could have corroded/loose connections to the charger or the charger is failing.

As Mark eluded to, interpreting the battery and charger voltages depends on the state of the batteries, the state of the battery charger, the current DC loads on the system and whether or not a charge source is currently hooked up. The standing voltage is also affected by how recently the charger was disconnected (temperature).

This owner is almost disabled and a full timer who camps in the National Forest to save money.

I am taking a leap here and guessing she is boondocking a lot and may be running the batteries to dead before charging them. Again a good battery monitor and some training on how to use it will go a long way to preserving the next set of batteries.

She also may be a candidate for solar solution but that gets pricey quickly and is subject to shading. I know a lady in her 80's that does the same thing in her 5W and she is always parked in shade and is almost always off the grid. I convinced here to get a 2000W generator and to recharge the batteries every 3 days or so using a simple 15amp auto battery charger. SOlar would not have helped her out.
 

nfredrick

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Re converters from The RV BATTERY CHARGING PUZZLE (well worth reading for battery charging info...)
Converters are set to maintain the batteries at the “float” voltage, about 13.5 volts, and supply a trickle charge (2-3 amps, or 25-35 watts) to keep the batteries full, while not over charging them and boiling them dry. Because of the length and size of the wiring in most rigs, the converter typically supplies less than 13 volts to the battery. Some newer three stage converters will put out over 14 volts, but that is still too low. You cannot successfully charge batteries with a converter, because you never get the batteries up to the required 14.4 volts and hold them there long enough.
I installed a new 60 amp Intellipower converter in a friend’s rig & when we started the generator I measured only 4 amps output at 13.6 volts right away. It dropped from bulk charge to float in seconds, and those batteries were not full. Does that sound like a battery charger to you? Their own spec sheet says that it drops to float when the batteries are at 90% and in my experience this is very optimistic

Battery manufacturer’s specifications say that a standard 12 volt wet cell battery needs to be charged to between 14.4 to 14.8V and then held there for some time before it will be fully charged. The Trojan Battery company says 14.8V daily charge (at 77 degrees F) and Interstate will tell you over 15V. Trojan’s 2010 Users Guide has a new chart that shows you should actually vary the voltage depending on the amps you supply for charging and even higher voltages are recommended. Of course they recommend temperature regulation. So all of those out there who are telling you 14.8V is too high do not know what they are talking about.
 

Larry N.

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You cannot successfully charge batteries with a converter, because you never get the batteries up to the required 14.4 volts and hold them there long enough.
Interesting statement- then why do I periodically get a Full Charge status on my EMS? Not all converters are the same, for one thing. You have to look at the whole system.
 

Gary RV_Wizard

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I think you have either misunderstood or overstated what those battery guides say. I've included a link to the Trojan User Guide as an example.

Optimal charging is described as multi-stage, Bulk, Absorption, and Float. Voltage in the 14+ range are recommended for Bulk & Absorption phases, with the Bulk slowly increasing voltage until Absorption can begin. It doesn't say just charge at 14.7v (2.45 volts/cell). The proper voltage and maximum current at any given point in time while charging is a complex decision.

I'll grant that the chargers in most RVs are conservative, limiting both voltage and time while trying to avoid battery damage or fires due to over-charging. Most RV owners are pretty much oblivious to their batteries and benefit from conservative management.
 

John From Detroit

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Davison Michigan
Ok one of the problems with "Group" batteries (24/27/29/31) is that they are not often DEEP CYCLE. they are often MARINE/deep cycle. closer to starting bateries than deep cycle.
They really don't like being run down too far.. (True (GC-2 for example or GC-12) DEEP CYCLE are more "Forgiving" (Still don't like it but hey. and "Too far" is a lot lower) GC-2 you need two in series to make 12 volt...) a pair of GC-2 is around 220 AH.. ANd cost closer to a pair of Group 24 (less power for the dollar)
Resting voltage on a 12 volt full charge is around 12.6
Fload about 14.6
Charge higher
NOTE: It may vary a bit depending on other factors (like how hot is is).
And finally.. as the battery runs down.. so does the voltage IN fact you can get rather close estimate of state of charge by reading the voltage (Many charts on the internet)

LIFeP)4 (What I use for one of my radios) the "12 volt" batteries have a resting voltage of 14.4.
And as they run down that may drop Much more slowly for example 30% Charge they are still 13 volt

Source document: LiFePO4 Battery Voltage Charts (12V, 24V & 48V) - Footprint Hero
Oh at 30% state of charge most lead acid batteries are done for.
 

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