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Ask Dave: When plugged in at home, will converter charge and desulfate RV’s batteries?

Dear Dave,
Jayco tells me I have a Progressive Dynamics 9200 Series Intel-Power Converter/Charger, specifically model PD9260C. From what I can find online, the unit has the following four modes: Boost, Normal, Storage, and Equalization. First Question: Our motorhome is a 30-amp service. When our motorhome is home and stored between trips, if I use an adapter to plug the service into a 20-amp receptacle, will this unit first fully charge the batteries and then switch to a mode that performs battery maintenance and desulfation? Second Question: Will I need to leave the motorhome’s main power switch in the “on” position for the converter/charger to perform the charging, maintenance and desulfation when I have it plugged into the 20-amp receptacle? —Pat, 2020 Jayco Alante 26X

Dear Pat,
My first question is, what type of batteries do you have? If they are lead acid, then this is a wonderful converter/charger to properly charge and desulfate the batteries. If they are lithium, you will need to look into another charger or ruin them!

The boost stage of most chargers will provide approximately 16 volts or slightly higher to “boil” the lead acid and break up the sulfation. As your batteries drain amp hours, sulfur coats the plates and with a conventional charger/converter it just provides 13.6 volts until the batteries are charged to 12.6 volts and then drops to a 13.2-volt maintenance charge. This will not properly charge and desulfate the batteries.

According to the spec’s for the 9260C, the boost stage provides 14.4 volts, which is OK for lithium batteries as that is what they want for a charge. This charge brings the battery up to 90 percent charge.

Then the “normal” mode provides 13.6 volts to complete the charge. Once the batteries are full, the converter goes into “storage” mode at 13.2 volts. The “equalizing” mode is 14.4 volts every 21 hours for a period of 15 minutes to make sure sulfation is not affecting the battery.

Check the distance from converter to battery

One thing that will affect the performance of this converter is the distance from the converter to the batteries and the gauge wiring. Typically, this will be relatively short. However, we recently replaced a standard converter in a 2015 Thor that had the converter in the bedroom and the distance to the battery bank was more than 20 feet. It had 6-gauge wiring. According to the tech at Progressive Dynamics, that distance and drop in voltage would require going to 2-gauge. We remounted the converter into the battery compartment. So make sure you have the correct gauge wiring for the distance.

Another factor is what gauge and distance is your extension cord, if using one. Again, a long distance will have a voltage drop. You should be able to verify both of these using a multimeter to see what voltage you are getting at the battery. This would need to be done during the Boost mode first.

For your second question, you will need to leave the main circuit breaker on during storage as this provides 120-volt AC power to the circuit breakers for the converter, which you will also need to leave on. I would suggest shutting off the others since you will be plugging into a 20-amp circuit and you might have other outlets “ganged” to that circuit in your garage.


 You might also enjoy this from Dave 

Ask Dave: How can I tell if my converter is charging?


Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here

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John
8 days ago

How is this converter for an AGM?

Joe
10 days ago

Dave, great article! Let’s not forget that it’s very important to check the water level in the batteries every month especially in very hot weather. Low water levels water will not allow a battery to charge correctly and will wreck a battery very quickly. I make it a point to do it the first week of every month.

Drew
10 days ago

I have a single stage converter and get 4 to 6 years out of a set of l/a batteries- always. Don’t charge them between trips and you won’t ruin them.

Bill T
10 days ago

I have used a 15 amp, 25′ extension cord for years without issue. After all it is your charger/converter that is providing the charge voltage to your battery not the 120 volts from your house. I measure the AC input to the charger to ensure I have between 110 and 120 volts from my house and check the DC charge going to the battery for all the stages of output from my charger. I have a PD4060K multistage charger for my Lead Acid battery and have had no issues for 5 years charging at home.

Joe
10 days ago
Reply to  Bill T

That sounds sufficient for the job but what he is trying to explain is a long light weight extension cord could drop the 120 voltage to let’s say 100 volts. Lower voltage in = lower voltage out.= lower charging volts. Besides the extension cord you need to factor in the cable run distance and size from main panel breaker to garage, condition of the receptacle at the garage and condition of the extension cord ends. Also any other heavy load on the branch circuit that could be drawing the voltage down.

Mike DeAngelo
10 days ago
Reply to  Joe

A transformer would see a drop in output voltage if the input voltage drops, but modern AC to DC converters based on switching power supplies typically work at a fairly wide range of voltages. (Most laptop computer and cell phone chargers even work from 100 to 250 volts AC.) So even with a long extension cord the converter should be able to properly charge and condition the batteries.

The voltage drop from a long extension cord is a function of amperage load. So if you measure 120 at the receptacle you should still measure 120 at the end of the cord if nothing is plugged in. But an 80 amp converter will pull 8 or 9 amps at
120v when running at full output. You will see significant drops in voltage if you measure under load.

The bigger issue is the distance between the converter and the batteries. At 12 volts nominal the converter needs to push up to 80 amps to the battery. That needs a big wire or else you will have a big drop. You would need to measure the voltage at the battery during the boost or equalize modes. When the battery is trickle charging almost no current is flowing so the voltage won’t have any drop.

My class A had the converter in the rear storage compartment and the batteries up front 25 ft away. I’m thinking about relocating the converter to an adjacent compartment up front.

Mike DeAngelo
9 days ago
Reply to  Bill T

As a general note look carefully at the details of extension cords. A good 15 Amp cord should have at least 14 gauge copper wire. 12 gauge is even better, normally used for good 20 Amp cords. 10 gauge is even better still. You can always safely increase the size of the wires (which means a smaller wire gauge number). Bigger wire means lower voltage losses. It also means the wire won’t heat up as much and potentially start a fire.

From an electrical supply house or the wire area of stores like Home Depot you can buy cords made up of copper wire of the right gauge in a rubber coating right off as reel in custom lengths. Then you make your own extension cords by adding the ends you want. But this route is often expensive. I like to look for the right wire gauge extension cords on eBay. Then I cut off the ends and put on the cord ends that I want to use. So I’ll get a 20 amp cord and put a 15 amp plug on the end. Now I have a cord that I can use for a longer distance without voltage drop issues or heating issues.

As an extra hint I usually don’t cut the original cord ends off right at the end but I leave at least a foot. Then I can use those for another project. For instance if the cord ended in three receptacles I can put a new plug on the other end and have a handy power tap. One foot lengths with a plug and single receptacle are useful when plugging in something with a “wall wart” or odd size. That way the adjacent receptacle is not blocked.

steve
10 days ago

If 14.4 is ok with lithium and his PD charger maxes out at 14.4, how will this ruin the lithium battery, if he has one?

Bob Palin
10 days ago
Reply to  steve

It won’t. Firstly the author states they want desulfation so they can’t possibly have lithium batteries. Secondly the desulfation voltage is only 14.4 as you say so it wouldn’t harm a lithium battery anyway, he does say this later in the answer.

Here are the specs for the 9200 series Charge-Wizard feature
https://www.progressivedyn.com/rv/charge-wizard/

steve
10 days ago
Reply to  Bob Palin

Thanks. He sure did say that, I missed it.

Mike DeAngelo
9 days ago
Reply to  steve

There are converters that use a boost mode of up to 16V. That can be a problem.

Some Lithium batteries (especially the LiPO variety) are designed as drop in replacements for lead acid. They have a built in charge controller that manages the battery charge no matter what converter puts out. If this is the case the worst is that a little bit of energy is wasted when the converter tries to boost or equalize the lithium batteries.

Another issue when using a lead acid converter with lithium batteries is the lifecycle. Lead acid batteries are best when they are regularly charged to 100%. The worst thing to do to a lead acid battery is store it at anything less than full charge. And running it down below 50% is a bad idea too. But if a lead acid battery is accidentally discharged to zero it can be recharged but it’s life will suffer. So your usable capacity is about 50% of the total capacity. If you buy 2000Wh of lead acid battery treat it like you have 1000Wh.

Lithium batteries are different. They don’t like being charged to 100%. A lithium battery charged to 100% will show loss of capacity after 500 or 1000 cycles. If the battery is only charged to 70% to 80% it will last 8000 cycles before showing loss of capacity. That is the difference between replacing the battery every few years and every few decades! Lithium batteries can be discharged to about 20%. The battery might be irreparably damaged if discharged to zero.

To maximize life treat the lithium battery like its usable capacity is 60% of it’s maximum capacity. Consequently if you buy 2000Wh of battery capacity, you should treat it like it is actually 1200Wh. A lithium specific charge controller should be able limit the charge to 80% and disconnect the batteries at 20% to prevent damage.

Tom
11 days ago

Suggest have an electrician install a 30 amp RV only box outside the house. We had one installed years ago and it has provided us excellent service.

Bob Palin
10 days ago
Reply to  Tom

Not necessary for this application, in fact I am able to run my fiver’s A/C off a 20 amp circuit without any problem. My house came with a RV style 30 amp receptacle on the garage and it worked fine until a friend arrived with a huge motor home and tried to run 2 A/Cs, that’s when I discovered that the RV receptacle was actually on a 20 amp breaker and circuit.

Mike DeAngelo
9 days ago
Reply to  Bob Palin

Agreed. It is nice to have but not generally needed.

Your biggest loads are going to be your AC and fridge. When the AC compressor cycles on there is a really big load – the starting surge – that only lasts a second or two. The AC might only draw 5 Amps while running but it might draw 15 when starting. Many circuit breakers are designed to allow this momentary overcurrent. The fridge might draw 3-5 Amps. Unlike home fridges that are mini air-conditioners that also have a starting surge, RV fridges are usually absorbtion types that draw a steady current. A hair dryer might need 10 amps. The converter draws almost nothing when the batteries are charged, but may draw 8 or 10 amps when the batteries are empty.

If you want to run the AC and the fridge while at home it might be a good idea to get a dedicated circuit put in. Also if you use your RV like a guest cottage you might have a problem if the fridge and AC are running and the guest tries to use a hair dryer. If you are going to the effort of putting in an outlet, spend the extra $200 or so to put in a 50 amp circuit. The labor cost is the same plus you have it if you get a bigger better RV, to charge an electric car in the future, you can run a welder, etc.

(When I had my driveway redone I also put a dry well in the ground. That way I can occasionally dump at home if I need to. During COVID-19 a friend lived in my RV for a few weeks to isolate as well. It was very useful then. It didn’t need to be sized to handle a family full time. A 50 gallon dry well if more than enough for the handful of times a year I might use it.)

When my motorhome is parked at home I just want to keep the batteries conditioned. That takes very little electricity. A day or two before a trip I’ll turn on the fridge. That is also fine. If it is hot I’ll turn on the generator and run the AC for a few hours before leaving to cool the interior.

In the winter I have one of those “oil filled radiator” style electric heaters. I’ll plug that in to keep the interior from getting too cold, just as extra protection. It runs fine on a good quality extension cord as well.

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