What converter/charger amps do I need?

I know chargers have been discussed to death, so I'm sorry in advance for any repetition here.  As mentioned in another thread, my MH's Progressive Dynamics PD9160 converter/charger has bit the dust and I'm currently shopping for a replacement.  The Progressive products seem to be the most recommended on the market so I'll probably stick with one of those.  I'd be happy to buy used and save money over a brand new charger, but I'm not having much luck finding anything there.  The dead charger is a 60-amp model.  Should I be ONLY shopping for 60-amp (or higher amp) replacement chargers, or could I get by on a lower output model like 45 amps?  How do I know?  I read a couple threads on how all that can be calculated, but it's still a little foreign to me.  Any tips are appreciated.

P.S. If you know firsthand of any RV salvage (or any other place) that may have these chargers available used & tested, please let me know.

The MAXIMUM size of the converter is determined by your batteies.. The minimum size by your needs

For example.. A standard pair of golf car batteries such as a Trojain T-105 or Interstate U-2200 can take charge at up to around 70 amps safely  That is 30 percent of their capacity.

Thus either a 60 or 80 amp converter is best for those. The 80 will re-charge them faster but the 60 might make 'em last just a bit longer.  Either one works fine though (I'm assuming some use of power within the trailer or coach)

Damon gave me a 9180 with charge wizard

I recommend either the 9100 WITH wizard or the 9200 line which has them built in.

IT works very well

If you use a smaller converter .. Say a 40 amp, it just takes longer to re-charge the batteries

If you use one too big. you can boil your batteries dry fairly quickly and damage them

30 percent of your battery capacity .. Rounded off to the nearest size

The rating on my batteries states "132 mins @ 75 amps".  I have two batteries, so 75+75 = 150 amps.  30% of 150 amps is 45 amps.  So are you saying that the 45-amp charge rate is the maximum my batteries should have, or would at least be more than sufficient?  Charging time is not really an issue for me, since my rig is nearly always plugged in and we don't rely on running the genset for charging.

Amen on Progressive Dynamics and Charge Wizard.

Make sure your generator can handle the charger (Power Converter) if you plan to dry camp.

I have a 40 amp charger, 1000 watt generator, and 220 amp hours of battery. They all work together nicely.

40 amps at 14.4 volts plus losses ~600 watts - comfortable for my 1 kw.
60 amps ~ 900 watts - maxes out the 1 kw's continuous rating.

Dry camping, I go down to 50% and then recharge back up to 80% - so I need to put 66 amp hours back in when I charge.  That takes about two hours.

Once you get to about 80%, the charge accepted starts to taper off so you're turning gasoline into noise mostly.

Joel

scottydl said:

The rating on my batteries states "132 mins @ 75 amps".  I have two batteries, so 75+75 = 150 amps.  30% of 150 amps is 45 amps.  So are you saying that the 45-amp charge rate is the maximum my batteries should have, or would at least be more than sufficient?  Charging time is not really an issue for me, since my rig is nearly always plugged in and we don't rely on running the genset for charging.

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Then it really doesn't matter much.  Get another 60 amp, or drop back to 40 if there is a significant cost difference.  But do get the PD and (or including) the Charge Wizard.  It won't boil your batteries.

Joel

Stay with the Progressive Dynamics and the charge wizard.

I'm surprised your converter failed.   Was it due to a voltage surge?

Going to a larger sized converter will not change your charging rate.   The output voltage determines how many amps are provided to your batteries.   If you're getting a 30 amp charging rate from a 45 amp converter, you'll get the same rate from a 60 amp because the output voltages are the same.   The only way your charging rate will change is if it's being limited by the current capacity of the converter.

Keep in mind your converter has to power all of your 12 volt loads in addition to charging your batteries.  How many light bulbs does your rig have?  Each bulb pulls about 2 amps.  Your furnace pulls about 10 amps.  Running the furnace and a half a dozen light bulbs will consume the majority of power available from a 40 amp converter.   Add a couple of discharged batteries and the converter will be running flat out to satisfy the demand.

I don't see any benefit in going to a smaller converter that would have to work harder to do all of this.

I recommend staying with the 60 amp model or even upgrading to a larger size.  If you go larger, you'll have to verify the wiring and fuses between the converter and the main distribution panel are large enough to handle the increased current.

Lou Schneider said:

I recommend staying with the 60 amp model or even upgrading to a larger size.  If you go larger, you'll have to verify the wiring and fuses between the converter and the main distribution panel are large enough to handle the increased current.

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Not sure I'm up for all that.    I'm a DIY and could probably handle the job, but I think I'd rather spend the extra $10-20 to stick with the 60-amp.   

Lou Schneider said:

I'm surprised your converter failed.  Was it due to a voltage surge?

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So am I quite honestly since the PD products are so highly regarded here, and honestly I have no idea what caused the failure.  My house batteries went completely dead while the rig was plugged in continuously, but appeared to take a recharge okay when I removed them and hooked them up in my garage to my standard auto battery charger.  The converter power supply tested fine, all the unit's fuses are good, but it's only measuring a 3 volt output.  PD tech says it should be at least 13 volts and the unit is dead.  That's how I've gotten to this point.  The MH is winterized and we're not camping for several more months, so I'm taking my time in solving this problem and making sure I'm aware of all the options and possibilities.

The fuses should only blow if you connect the batteries backwards and send a bunch of current through the converter.  I don't think they blow otherwise.  You could have a short circuit that's pulling down the voltage on the converter without blowing the fuse.

Try disconnecting the wires from the output and see if the voltage goes back to normal.  If it does, I'd look for a short in the house wiring before replacing the converter.

scottydl said:

The rating on my batteries states "132 mins @ 75 amps".  I have two batteries, so 75+75 = 150 amps.  30% of 150 amps is 45 amps.  So are you saying that the 45-amp charge rate is the maximum my batteries should have, or would at least be more than sufficient?  Charging time is not really an issue for me, since my rig is nearly always plugged in and we don't rely on running the genset for charging.

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132 minutes at 75 amps is around 150 amps for one hour, those are good size batteries  Hold on I looked at the US battery specification chart located here http://www.usbattery.com/usb_specs_deep_cycly.html and found no battery on that chart that was 130 minutes at 75 amps, However the US2200, which is a six volt golf car battery very common on RV's was 122 minutes at 75 amps

The amp hours on that battery at the 20 hour rate are 232. and when you hook two in series to make a 12 volt RV battery it remains at 232 amp hours.

(When you wire in series you add voltage, in parallel amp hours

So when I used the example of the Interstate U-2200 or Trojain T-105.. All equivlant  batteries to the US-2200

I have a feeling that the Original Size may well be best for you, or 60 amps.

Lou Schneider said:

Try disconnecting the wires from the output and see if the voltage goes back to normal.   If it does, I'd look for a short in the house wiring before replacing the converter.

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I'm almost positive I did disconnect the converter output before testing (as directed by the PD tech) but I will double check.  Thanks for the tips everyone.

60A is fine but a 50A would do just as well, if you can find one of those. And an Iota with the Smart Charger is as good as the PD + Charge Wizard.