an unusual charging problem

[pianotuna]

Hi all,

I'm generator charging from need for the first time in my life. It is not hot enough to run the roof air.

Here is a bit about the system.

Magnum 3000 Hybrid 12 volt to 120 volt with ARC remote

Yamaha 3000 sIEB inverter generator

4 139 amp-hour surplus acid telecom 12 volt batteries totaling 556 amp-hours. These are a bit unusual as their specific gravity is 1.3 rather than the more normal 1.275. They have a slightly higher voltage.

256 watts of solar into a Blue Sky 3024 di controller.

voltage monitored with a kill-a-wall unit

Wattage monitored by an Efergy Elite classic watt meter.

Charging rate monitored by the Magnum remote.


Conditions:

Batteries were not fully charged yesterday and were used overnight. Remote display said 12.5 volts.

I started the generator leaving it at maximum output.


I made the following observations:

Remote went immediately to float charging at 10 amps

Load was the fridge at 311 watts (2.5 amps)

Voltage was 122.

I turned off the fridge. No change in charging rate or voltage

I increased the load on the system by turning on the water heater 1300 watts (11 amps) voltage 118

Charging rate increased to 39 amps.

I turned off the water heater and charging amps slowly dropped back down to 10.

The "trigger" point for higher amp charging appears to be about 1300 watts. Doing so may double the fuel consumption rate. I'd prefer to avoid this.

[BFL13]

I don't understand PT's set-up at all. but perhaps he can actually get his batteries charged without all this power sharing stuff the Magnum does if he just splits his battery bank when doing a recharge, and does half at a time where the charger can do its full rated amps?

I doubt it is a generator limitation. I can charge at 155 amps with my Honda 3000 using a PF corrected 100 and a non-PF corrected 55 both set at 14.8v.

PT is doing something weird! 🙂

[GordonThree]

BFL13 wrote:
"which could be more useful than expect it to boost power."

I would assume that it cannot boost Power since you can't get more out than in, but it could perhaps boost voltage while reducing amps for the same power?

This is the trade off. You can't increase power, volt-amperes but you can increase or decrease voltage, the volt-amperes remain the same minus losses.

[BFL13]

"which could be more useful than expect it to boost power."

I would assume that it cannot boost Power since you can't get more out than in, but it could perhaps boost voltage while reducing amps for the same power?

[time2roll]

pianotuna wrote:
I'm beginning to wish I had spend more and gotten a Victron.

Unless you talk to a knowledgeable person that has a Victron I would not worry about it.
Victron website says they have their own charging algorithm. It may not do as expected either.

I think these inverters with assist are primarily designed to be plugged in 24/7 to limited power.
I would keep that PD40 in the circuit if you can.

[GordonThree]

Happy, why do you state an auto transformer can't step up output?

When you set your taps at 1:1 output tracks input. If you set your taps beyond 1:1, your output will exceed the input. Taps below 1:1 will reduce the output. The transformer can also be connected backwards, giving you more boost ranges.

That's why AC is so handy, simple magnetics can step up or down the voltage as needed. Of course it's not magic, there are some trade offs. Wikipedia can explain them.

[happycamper002]

pianotuna wrote:

Nec may forbid "hard wired" installation of devices, but since my autoformer unit is a plug in device it is not forbidden and is perfectly legal. There are many thousands of these in use in Mexico.

Mexico is not US. Besides, you can google some manufacturers who jumped into this bandwagon only to discontinue this product or went belly up because they cannot fool all the people. No one will stop you from using it or simply using it as foot rest which could be more useful than expect it to boost power.

There is no doubt this can be useful in Mexico because some rural areas there are feed by 240Vac. Having a center tap will enable you to use 120Vac appliances sold for US consumer.
I refuse to open the link you provided because I don't want to be suckered just like the rest.

[GordonThree]

Page 41 of the 2013 MSH3012M and MSH4024 manual states charging current will be reduced if the inverter temperature is high or the input AC voltage is below 90 VAC. It also states low charging rate with a generator can be caused by low power capacity of the generator. Maybe your Yamaha is acting up at low loads?

Come to think of it, one of my Yamaha 2000 was doing the same thing. It would stutter and spit at low wattage loads, but run a space heater just fine at full speed. That really confused the Magnum since it likes to "ramp up" its charger load (part of the pfc circuit I think). The generator would reject the light load and the so magnum wouldn't qualify the generator as a suitable power source (blinking charge light on the ARC.) I switched to my other yammy and everything was normal. Back home I ran a lot of carb cleaner and a tank of fresh gas through the yammy that was acting up and it recovered.

MrWizard: From page 43 of the manual:
AC input voltage range 60 to 140 VAC (120 VAC nominal)

[GordonThree]

What did Magnum say?

MrWizard: I find it odd that 122v would be considered too high for the charger to operate properly.

[pianotuna]

Smk,

It is a pretty freaky design then.

Let me try to be crystal clear.

At 122 volts I get 10 amps of charging. The only load was the fridge.

At 118 volts I get 40 amps of charging. The only load was the water heater.

That is the exact opposite of what I expected. So either the Magnum tries to protect something or else it is a (another) fault in the programing.

I'm beginning to wish I had spend more and gotten a Victron.

[pianotuna]

Hi happycamper002,

We had quite a long thread on this. autoformers for dummies

My Sola Basic has three levels of boost and one of buck. I have documented in other threads how well this works.

Nec may forbid "hard wired" installation of devices, but since my autoformer unit is a plug in device it is not forbidden and is perfectly legal. There are many thousands of these in use in Mexico and I have personal knowledge of at least five other RV'ers who use autoformers successfully.

Now, do you have anything to offer on the current thread, which has nada to do with autoformers as I'm using it for a foot rest at the moment?

happycamper002 wrote:


Contrary to popular belief, auto transformers, being a single winding doesn't boost low voltage conditions. They are merely designed to be connected directly to the single winding with a center tap (or anywhere between extreme ends of the winding) depending on what output you would expect at the load end.

In order to boost the voltage, you would need a buck/boost transformer which is basically a two-winding transformer with primary and secondary windings. Some manufacturers sell a product they call autoformer which hasn't gained any traction especially who are familiar with transformers.

Besides,NEC (National Electrical Code) forbids autotransformers in RVs because of potential over voltage if a winding is open (burned portion of the coil).

[time2roll]

MrWizard wrote:
but i prefer to keep my bank above 70% if possible
I can't let it charge on shore power for a week in the driveway

OK that is still below 12.5

Magnum apparently wants to go straight to float at 12.5 volts, pianotuna wants a full bulk/absorption cycle.

Probably working as designed. That is all I am saying.

Likewise I have my controller set for a very short absorption if it wakes up to 12.5 volts. If it wakes up to 12.2 the absorption is much longer. If it wakes up to about 11.8 (yikes) the battery gets no float all day.

[happycamper002]

MrWizard wrote:


he just recently got an auto transformer for Boosting low voltage shore power conditions
but it sounds like he needs to 'BUCK Down' the generator output, because of the finicky Magum

Contrary to popular belief, auto transformers, being a single winding doesn't boost low voltage conditions. They are merely designed to be connected directly to the single winding with a center tap (or anywhere between extreme ends of the winding) depending on what output you would expect at the load end.

In order to boost the voltage, you would need a buck/boost transformer which is basically a two-winding transformer with primary and secondary windings. Some manufacturers sell a product they call autoformer which hasn't gained any traction especially who are familiar with transformers.

Besides,NEC (National Electrical Code) forbids autotransformers in RVs because of potential over voltage if a winding is open (burned portion of the coil).

[MrWizard]

Yes if you were at 40% the voltage would be much lower and I would recommend running the generator early to let the solar do the long absorption work later in the day.
In these conditions Magnum should run the voltage to 14.4+

if i was at 40% I would be Down 402ampHrs
an awful lot to return
6~8 hours of generator with PD70 and NO A/C, before solar could be used for absorption

Not gonna happen in this weather
maybe in Mid-winter
but i prefer to keep my bank above 70% if possible
I can't let it charge on shore power for a week in the driveway

[pianotuna]

Hi MrWizard,

I do have my old PD 40 amp converter and could easily plug it in. I've never had both the Magnum and PD charging at once. I have used the PD with the new battery bank due to GFCI problems with the Magnum.

I might try turning off the Magnum charger and then plugging in the PD. Fortunately I have a nice hall effect meter on the PD so I'd know the net amps going to the battery bank.

The threshold appears to be 118 volts / 14xx watts.

I have seen 127 amps from the Magnum which causes it to fault. After I investigated I throttled it to 108 amps. I've seen that a few times, but not often.

MrWizard wrote:
I think PT is saying the Magnum reduces charging at 122v input (some kind of thermal ? protection for the Magnum )
turning on the water heater (using genny power not inverter) reduces the yammy output line voltage to under 120v or less and the magnum then turns on and charges the batteries
it Is an unusual situation

Don
don't you have another converter you can plug in in this situation
39amps is no where near the max of the magnum
IIRC you do have something else that will supplement that 10 amps and get back to near 40amps charge

[time2roll]

MrWizard wrote:
while thats true for weekends or part timing
get a big bank too low and you could spend a whole lot of time in bulk mode generator run time

with a 20% 12hr use (IF i did not charge during the day) i would be at 60% before bed tonight and 40% tomorrow morning
NOT the place i prefer to be
i can do that in a bad weather pinch, and the solar does mitigate the situation making it less strenuous than the straight math, and i could limit some of the power drain at night and make (2) with no charging
put that is winter time use, cool weather and no A/C, and less cooling strain on the fridge



different routines for different folks

Yes if you were at 40% the voltage would be much lower and I would recommend running the generator early to let the solar do the long absorption work later in the day.
In these conditions Magnum should run the voltage to 14.4+