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Old 10-14-2021, 06:29 PM   #1
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Recommendations on Higher Capacity Converter Charger

I'm not getting enough solar charge this time of year to keep my batts charged and am forced to use the generator - I hate the noise......

I have a four Trojan 6-volt AGM battery bank on my Desert Fox Toy Hauler with onboard Onan Generator. I have an OEM Progressive Dynamics 45 Amp converter / charger now, my Victron Battery Monitor says I get maybe a 25 Amp max charge when the batts are drained down to say 60% SOC - then drops as batteries charge. Consequently, I'd like to speed up this process.

With 434 AH in my battery bank, what would folks recommend for a new converter charger? Size of charger and make or model?

I have about a 12-foot run from the charger to the batteries - What size cable would be appropriate for a higher output charger? The wiring is "as-is" from the factory. How critical is this cable size to charging efficiency?

Having a unit with a lithium charging capability is attractive, my batteries are two+ years old now and lithium or something else will probably be the best choice down the road.
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Old 10-14-2021, 06:36 PM   #2
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20% of AH capacity so 75 to 95 amp converter.

Move the converter closer to the batteries or use 6 or 4 gauge wires, both positive and negative .
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Old 10-14-2021, 09:07 PM   #3
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Sounds like I should improve the cables first and see what that does for my charging performance.

Changing out the charger is the easy thing and the cables would need to be addressed in any case.

Thanks for the response.

Anyone have a recommendation for brand on a charger / converter?
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Old 10-15-2021, 09:36 AM   #4
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I have a four Trojan 6-volt AGM battery bank on my Desert Fox Toy Hauler with onboard Onan Generator. I have an OEM Progressive Dynamics 45 Amp converter / charger now, my Victron Battery Monitor says I get maybe a 25 Amp max charge when the batts are drained down to say 60% SOC - then drops as batteries charge. Consequently, I'd like to speed up this process.

With 434 AH in my battery bank, what would folks recommend for a new converter charger? Size of charger and make or model?

45 amps is OK, but a little small for generator charging of a 434 amp hour battery bank. The battery bank could easily use 60 amps or more when deeply discharged.

60% Soc is not deeply discharged, so a 45 amp charger is enough for that. Check the battery terminal voltage while charging when at 60%. 14.4 volts is the max. 13.6 would be normal.

A higher capacity charger would help a little when SoC is 20%.

I have about a 12-foot run from the charger to the batteries - What size cable would be appropriate for a higher output charger? The wiring is "as-is" from the factory. How critical is this cable size to charging efficiency?


8 gauge is enough to safely carry 45 amps.
6 gauge is efficient for 60 amps at 12 feet.
4 gauge is a little better for battery charging at 12 feet.

Most people feel wire gauge to be critical for battery charging when using a generator. Knowledgeable people choose larger when cost of cable is less important.

Summary:
  • Installing a larger capacity charger will not decrease charging time for 60% SoC.
  • Charging at the maximum of 14.4 volts may reduce charging time by 20 minutes only when deeply discharged.
  • 8 AWG wire gauge at 12 feet is more than adequate for charging at 25 amps.
  • 4 gauge wire at 12 feet is more than adequate for 60 amps.
  • A 400 amp hour lithium battery bank, discharged to 60% SoC, with a 100 amp capacity constant 14.4 volt battery charger would take less than 2 hours for a full 100% charge.
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Old 10-15-2021, 10:19 AM   #5
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You could get an 80A Progressive Dynamics charger. I suspect it would be a drop in replacement for your current chager except for wiring. Even though I suspect you will never see the full 80A you ought to size the wire for it. With a 12' run it will take #1 gauge wire to keep the voltage drop down to 1/4 volt for best performance.

Also check the specs for maximum AC draw. I suspect it will be within the existing 15A breaker capacity, but worth checking.

FWIW I get about 30 amps at 60% SOC into my 200 Ah bank of AGMs with PD's 60 amp charger. So don't expect a big increase.

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Old 10-15-2021, 10:38 AM   #6
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The importance of heavy gauge wiring is, as mentioned, voltage drop.

The charger is reading battery voltage internally while the battery is not seeing that voltage.
The charger voltage climbs out of the bulk/absorb range and cuts back to float charging, while the battery never saw any higher voltage.

Larger or shorter cabling removes the voltage drop.

I had a 55 amp converter/charger that would output its full 55 amps because it had 1 ft of 4 gauge wire to 8 feet of 2-0 gauge wire.
This was measured with a battery monitor.
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Old 10-15-2021, 05:10 PM   #7
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Quote:
Originally Posted by Oregon RR View Post
Sounds like I should improve the cables first and see what that does for my charging performance.

Changing out the charger is the easy thing and the cables would need to be addressed in any case.

Thanks for the response.

Anyone have a recommendation for brand on a charger / converter?
If youíre already committed to upgrading to LiFePo4, hold off on buying anything else until you get the new batteries. You might want to take a hard look at getting a hybrid inverter/charger that you can mount right next to the batteries with 1/0 wire, virtually eliminating voltage drop. A 2000w hybrid doesnít cost a lot more than an inverter/charger/transfer switch setup. And the biggie is the three top US brands can charge at 80amps, 100 amps for their 3000w models. And itís so convenient. With Bluetooth you can program the hybrid for the kind of batteries you have and the charge amperage.
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Old 10-15-2021, 05:31 PM   #8
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Also, keep in mind with SLA or AGM as you get closer to full the amps decrease.

I have 6 - 6v AGM. In bulk charge I am getting 125 amps, as it goes into absorption the amps fall as the battery gets closer to full. It spends several hours (shore or if we are using the A/C a lot) in the 15-25 amp range before it goes into float charge.

As others have reported my inverter/charger (3000w/125A) is very close to my batteries (on top of the box) and I have a short run (less than 3') of 4/0 wire connecting everything.
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Old 10-16-2021, 01:21 AM   #9
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Thanks very much for your replies. Several tangent issues raised. Cable size and length trump charger size at the level I've been draining batteries.

I'm not into going lithium now. I think I'll break even by upgrading the wiring and possibly the charger/converter with 3 to 4 years left on the batteries I have, I've treated them very gently. Sounds as if you guys think I could draw them down further than 60% SOC.

I'm going to try replacing the cables from charger to batteries first and see how that performs. Also kicking around adding some more solar on top of my truck topper, the current two panels - 320 watts - on my 21 foot Desert Fox about fills the roof. Flat rooftop solar panels this time of year don't provide much power.
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Old 10-21-2021, 03:34 PM   #10
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I have a 30 amp camper, two air conditions, a gas-electric refrigerator, microwave, and a heavy need for electricity use to operate my autovpap machine. I have central sleep apnea, so I can't use a normal c-pap machine to breathe with. I can go two and a half nights on one lead battery if only thing running is my air machine for breathing.

My wife loves her comfort so she demands some air condition use.

I just purchased this 34 ft 30 amp Fleetwood Bounder and have no idea how its system works, the person I bought it from is running lead batteries and they are on their last cycle, don't last more than 15 minutes lol so got to do something before I can spend even one night in it.

I have no knowledge to figure this stuff out. I don't know if I need to use 6 volt batteries, or 2 100 amp batteries or I am even willing to use 2 200 amp batteries. I don't want to blow up the RV lol, so I don't know what it can handle amp wise.

I was wondering about having two inverters, one for each side of the RV electrical circuit and two 100 amp batteries for each inverter. or 1 200 amp battery for each inverter. I have two things I want to accomplish.

Running a microw waive with out flipping a breaker while the air condition is on, and running my sleep apnea machine for a week. Can also do for 3 days at a time, some of the campgrounds we go to do not allow use of generators. I don't have a solar pannel installed but I will do it once I know what I need.

I am kind of weird in that I have two ways i can go. One is ultra conservative and that I can figure out on my own, but when it comes to luxury items and glamping, I want all the gagets with all the bells and whistles available to me. So I will be looking for inverter/converter charger system that has all the bells and whistles.

Pretend money is not an object... how would you build out my energy needs for my RV?
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Old 10-21-2021, 10:00 PM   #11
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Mr. White, you might want to move your request to a new thread, as it is only partly related to the original post. You may get more views and responses that way.

Running an air conditioner on batteries is a challenge. The draw is just too high. I can run mine, but only for a couple of hours. I think my AC pulls something like 85 amps out of my batteries, so it would run through my 300 Ah of battery pretty quickly.

Your question makes me wonder if you are mixing amps and amp-hours. You wonít blow up your rig by having too much battery.

I like Victron products, so have a 3,000-watt Multiplus hybrid inverter, and 300 amp-hours of lithium batteries. I can run anything in the trailer, but not necessarily all at the same time. I added the Victron VE.Bus dongle so I can control the inverter from my phone, and a BMV-712 to track usage. Victron has some pretty cool options for coordination and controlling the components of the system.

People talk about having 600, 800, or more amp-hours of lithium batteries. That is great, but you have to find a place to put them.
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Old 10-21-2021, 10:25 PM   #12
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Quote:
Originally Posted by Oregon RR View Post
Thanks very much for your replies. Several tangent issues raised. Cable size and length trump charger size at the level I've been draining batteries.

I'm not into going lithium now. I think I'll break even by upgrading the wiring and possibly the charger/converter with 3 to 4 years left on the batteries I have, I've treated them very gently. Sounds as if you guys think I could draw them down further than 60% SOC.

I'm going to try replacing the cables from charger to batteries first and see how that performs. Also kicking around adding some more solar on top of my truck topper, the current two panels - 320 watts - on my 21 foot Desert Fox about fills the roof. Flat rooftop solar panels this time of year don't provide much power.
I was having trouble finding cable locally. Some Amazon vendors sell precut lengths, but you can wind up with a lot of left-over material. I would up buying from wireandcableyourway.com - they will cut and sell by the foot. I bought 13 feet each of black and red 4/0 cable for $6 per foot.
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