Charger selection help please

[hammick]

I'm thinking about buying a Noco Genius G26000 26a smart charger for when the sun isn't getting my batteries charged.

I have a FR Stealth Toyhauler with two Interstate GC2 208ah batteries. They do everything I want and more when I am able to get them fully charged. 99% of our camping is boondocking and our solar system will get the batteries fully charged during the summer assuming it is sunny and we aren't in the woods. I have a crappy 55a Wyco converter that never gives more than 13.7a to the batteries.

We boondocked for four days over Thanksgiving and it got quite old hauling out my Schumacher 25a cart charger to get the batteries fully charged. Plus the Schumacher gets the batteries over 16v when in absorb.

When charging I use a 2000w Yamaha inverter. I do have a built in 4000w Onan if needed.

I've read about all the threads on replacement converters, the Meanwell power supplies and other options. But I keep coming back to the Noco for it's many charging options and convenience.

Can I get these batteries fully charged using the Noco in a reasonable amount of time or should I go with something like the Powermax Boondocker with adjustable voltage or a Megawatt. I'm willing to pay the premium for the Noco but not at the expense of hours of extra generator time.

[BFL13]

Cydog15 wrote:

BFL13 wrote:
So with the money you saved not buying all that other stuff, just get this and forget the over-priced puny 26amper. it will run on the 2000w gen.

http://www.boatandrvaccessories.com/powermax-pmbc-55adj-converter.html

Expect your JKill-A-Watt to show:
124.7v, 11.06a, 1383VA, 980w, PF 0.71 when unit is set to 14.8v output, with output 56.8a batteries to 13.7v and rising at the time.

Note the ad is wrong--it does not do three-stage, it runs at whatever voltage you set it to and stays there till you change it.

Forum member JiminDenver camps like you do at 10,000 feet without even an oxygen mask apparently. His set- up might interest you if he shows up here.

I bought this one. Better value, 5 more amps, real customer service (they answer phone) and better warranty.

Adjustable Converter

Makes sense. Does yours ( a Boondocker version) have the one volt drop after the first 15 minutes so you must reset the voltage? The straight PowerMax version does that unless you open it up and snip R1. (That feature was for their main customers at car dealerships)

[MEXICOWANDERER]

Neighbor/landlady and 11 year old daughter are heading out with me at 0700. Dawn. Returning after sunset. With aid of 300-watt CREE light bar. Must plug in laptop to send zip files. Brand new battery lasted 2 days. I have no time to image newly discovered need for half-inch diameter hole next to toroids in starboard case wall so note it now. It works.

[landyacht318]

hammick wrote:

Anybody have a link to the nifty shunt/voltmeter mod for the Megawatt? I can't find it on Ebay.

Not sure what you want, An Ammeter?

No shunt required with this ammeter:

https://www.amazon.com/gp/product/B01DDQM6Z4/ref=s9_dcacsd_bhz_bw_c_x_3_w

I have a GTpower meter on my Meanwell output, but I modified the leads to 8awg( from 12awg) so it can handle 40 amps continuous without heating excessively.


https://www.amazon.com/Tenergy-Precision-Meter-Analyzer-Backlight/dp/B017YCTRKK/ref=sr_1_7?ie=UTF8&q...

Modifying these with 8awg is not too hard, but I did destroy one with a solder bridge.
Another wattmeter clone comes with 8awg leads but proved to be a huge disappointment as the Wh and AH figures were inaccurate in extreme.

As far as modifying the MW for a larger 10 turn voltage trim pot, Mexwanderer/Mrwizard are in the process of doing a pictoral/write up on the process.

[MEXICOWANDERER]

Meanwhile back at the ranch...

Starting from 80% state of charge 6 cells of GC220s will start out at 35 amps then rapidly sag. About an hour's worth of charging with a 40-15-5 amp wheeled charger. Crank up the gen twist the timer dial to an hour and when the gen burps at charger off shut off the generator. At home fill the batteries, connect a battery maintainer and walk away.

A four hour timer is useful for every 2nd day or 3rd day charging. The main thing is to allow a 30-35 ampere initial charge rate. If those batteries started out from say 12.1 volts in the morning an 80-amp charger would be appropriate.

Generators are sorta funny you know: They plug up their ears when someone screams "You are working at 10% load therefore you should last 10 times as long!"

Running a 30 amp charger for an hour makes sense. Running an 8 amp charger for 4 hours requires a straightjacket.

[Cydog15]

BFL13 wrote:
So with the money you saved not buying all that other stuff, just get this and forget the over-priced puny 26amper. it will run on the 2000w gen.

http://www.boatandrvaccessories.com/powermax-pmbc-55adj-converter.html

Expect your JKill-A-Watt to show:
124.7v, 11.06a, 1383VA, 980w, PF 0.71 when unit is set to 14.8v output, with output 56.8a batteries to 13.7v and rising at the time.

Note the ad is wrong--it does not do three-stage, it runs at whatever voltage you set it to and stays there till you change it.

Forum member JiminDenver camps like you do at 10,000 feet without even an oxygen mask apparently. His set- up might interest you if he shows up here.

I bought this one. Better value, 5 more amps, real customer service (they answer phone) and better warranty.

Adjustable Converter

[hammick]

Fubeca wrote:
I bought a Nice genius charger a few years ago when I was looking for something better than my old manual charger. It was my start down the rabbit hole of automatic/worthless chargers. It wouldn't hold absorb for any significant length of time and would pop to"charged" shortly after reaching the absorb voltage. It is fine for a starting battery but worthless for a deep cycle.

Thanks. You have confirmed my suspicions that the Noco wouldn't hold absorption for any length of time even with the higher voltage settings.

[pianotuna]

Here is what I have observed

Limiting input to 13 amps @ 122 volts (1586 watts) limited output to 108 amps @ 14.6 volts DC

If the output is linear then 15 amps @ 122 volts (1830 watts) ought to limit output to 125 amps @ 14.6 volts DC.

If we drop the input volts to 120 @ 13 amps (1560 watts) should limit output to 106 amps @ 14.6 volts.

So 120 @ 15 amps (1800 watts) should limit output to 123 amps @ 14.6 volts

At 115 @ 13 amps (1495 watts) should limit output to 102 amps @ 14.6 volts

So 115 @ 15 amps (1725 watts) should limit output to 118 amps @ 14.6 volts.

So BFL13 is correct a 15 amp shore power is probably not going to do 125 amps--unless the voltage is on the high side.

[BFL13]

PT that is kind of weird IMO. I think every converter I have owned has exceeded its rated amps with decent wiring to the battery. EG, my 100 does 103, the 55 does 56, my old Paramode 55 did 60. It is just normal. I don't see how the Magnum design should be on such a hair-trigger if it goes over 125. Oh well, not my problem!! 🙂

[pianotuna]

Hi BFL13,

The voltage from the Yamaha without load is 122.

The shut down of the Magnum was not from lack of power from the generator. It was from the charger exceeding the maximum of 125 amps that it is capable of. It shut down because the bank was hungry and drew 127 amps. Sorry if I was not clear about that before.

The generator continued to produce power.

BFL13 wrote:
Thanks, so the Magnum is a little more efficient ( 87 vs 80 ) than my 100 amper, so scaling up doesn't go as high as I posted earlier, but it still goes way up.

Another thing is the (loaded) input voltage with the Honda was 123v while the Magnum figures are using 115ish. Since that voltage is part of the VA, that makes the VA assumed to be needed by the Magnum seem low. PT's Yamaha would have had the voltage above 120 too, so the VA in his case would be higher from that.

Anyway, even the spec 18 amps for the 125a output is well over 15 amps, so I don't think PT's claim that you can run a 125 amp Magnum charger at 125a output at 14.x volts from a 15a receptacle on 14 wire with a 15a CB is correct.

A mystery remains that he was using his 3000w Yamaha as the power source, so it should have worked with the Magnum set at 23a input.

[Fubeca]

I bought a Noco genius charger a few years ago when I was looking for something better than my old manual charger. It was my start down the rabbit hole of automatic/worthless chargers. It wouldn't hold absorb for any significant length of time and would pop to"charged" shortly after reaching the absorb voltage. It is fine for a starting battery but worthless for a deep cycle.

[BFL13]

Thanks, so the Magnum is a little more efficient ( 87 vs 80 ) than my 100 amper, so scaling up doesn't go as high as I posted earlier, but it still goes way up.

Another thing is the (loaded) input voltage with the Honda was 123v while the Magnum figures are using 115ish. Since that voltage is part of the VA, that makes the VA assumed to be needed by the Magnum seem low. PT's Yamaha would have had the voltage above 120 too, so the VA in his case would be higher from that.

Anyway, even the spec 18 amps for the 125a output is well over 15 amps, so I don't think PT's claim that you can run a 125 amp Magnum charger at 125a output at 14.x volts from a 15a receptacle on 14 wire with a 15a CB is correct.

A mystery remains that he was using his 3000w Yamaha as the power source, so it should have worked with the Magnum set at 23a input.

[jharrell]

BFL13 wrote:
When you do the input vs output thing, the trick is to state the output with both DC volts and amps because you want the watts. If you do the same output amps at a higher voltage, that will suck more VA input from the 120v source.

So when they say 18 amps input required to do 125 amps out, what is the output voltage at the time? And for VA, what is the "120v" loaded voltage when the charger is running at whatever output watts they used?

MAXIMUM Output voltage during high current draw is determined by the absorption voltage setting. In bulk current is held constant and voltage rises until absorb is hit then current tapers. So worse case is 16v which is the max setting for absorb, which no one does, more like 14.3 such as mine.

14.3 * 125 = 1787.5 W

1787.5 / .87 (87% effcient) = 2054 W

2054 / 18 = 114V minimum

Also some info in their manual:

The MSH-M Series is equipped with a PFC (Power Factor Corrected) and PI (Proportional-Integral)
multi-stage battery charger. The PFC feature controls the amount of power used to charge the
batteries to obtain a power factor as close as possible to 1 (or unity). This causes the battery charger
to look like a resistor to the line (forces the charge current wave shape to mirror the voltage wave
shape). The PI feature allows the charger voltage and current to change independently. These two
features maximize the real power available from the AC power source (i.e., shorepower or generator),
which translates into less power wasted and greater charging capabilities than most chargers today.

[BFL13]

When you do the input vs output thing, the trick is to state the output with both DC volts and amps because you want the watts. If you do the same output amps at a higher voltage, that will suck more VA input from the 120v source.

So when they say 18 amps input required to do 125 amps out, what is the output voltage at the time? And for VA, what is the "120v" loaded voltage when the charger is running at whatever output watts they used?

[jharrell]

BFL13 wrote:
PT are you saying that setting the Magnum to 15a input is the same thing as plugging a 125 amp charger into a 15a receptacle in a 15a circuit?

The 100 amper was pulling 122.7v, 15.57a , reading 1910VA and the watts with that was 1854. PF 0.97

Scaling up to 125 amps output, that 15.57 input would be 19.46a

I don't know why the Magnum quit when set at 23a running the 127a charger output. 19.46 is way under 23.

Were there other 120v loads on the Magnum besides the charger?

Did the Yamaha 3000 (23.3? ) pop or was it just the Magnum at 23 that popped?

My Honda 3000 (23.3) runs my 100 amper (15.57) and my 55 amper (11.06) total 26.63. I don't know how it can. I guess the combined load pulls down the input voltage more than it is when they run individually, so the combined VA is lower than the individual VAs added. Anyway it runs.

So really, the Yamaha at 23 should have run the Magnum's charger at 127 amps no sweat. Perhaps it is all about that Magnum (which was the duff one? )

Magnum 3000 Specs are listed as follows:

Continuous output at 25° C 125 ADC
Charger efficiency 87%
Power factor > .95
Input current at rated output (AC amps) 18

This seems in line with what I see at max charging current on mine, definitely never hits 20 amps. On the Magnum remote you set max input amps and it backs off the charger if loads + charger exceed, on the hybrid model that also determines when it load supports. I have mine set to 30 and if at max charge rate then A/C kicks on it backs down and keeps it under 30 total, responds pretty quick.

If OP is anal about batteries hard to beat the Magnum with fully adjustable Absorb/Float/Eq volts temp compensated and Absorb done based on time or amps or SOC (with BMK). Not cheap though, but you do get a nice inverter as a bonus.

[BFL13]

That'll work. LY or somebody can describe how to put a bigger pot knob on it.