step down converter

[tecnodave]

vtMaps,

I just went to solar-electric and read that thread, and I do understand the problem.  The Honda EU 2000 I is a high frequency 3 phase generator which is rectified to DC then switched to AC by a high frequency inverter.

There are two problems to this approach. High frequency generator does not have a high surge capability, same with high frequency inverter, poor surge capability.

Generally running a switch mode unit from another switch mode unit will be problematic

I have avoided this using low frequency wound rotor generator and hybrid high/low frequency inverter with massive 60 Hz transformers much like the outback and magnum designs.

True the inverter generators are much more efficient at small  loads due to the ability to throttle down, but I do not run my generator for battery charging alone. I have a deep well at 520 feet with a 3 wire 2 hp. Pump at 240 volts. Pump start pressure is at 150 p.s.i. Due to the head between water level and top of storage tank. Start surge is enormous, never run from inverters.  I have smoked several Honda and other small generators.
My bigger Onan (6.5kw.NH-3 120/240v.) can pump water, weld and run two Iota chargers without a problem. The smaller one (4.0 kW. Onan Emerald 3  120 volt only) easily runs shop and house and all chargers at once. Only need the big one for deep well and big mig box and stick boxes,all else use the smaller one, newer design, more efficient.

My opinion of high frequency stuff...inverters and generators......more efficient but at a price....not for wound rotor duty....not for high surge loads.

My 3200 watt Dynamote inverter will start a 2 h.p. Ingersoll Rand air compressor, belt drive, cast iron old school, no head unloader, not only start and run but will restart at 125 p.s.i......try that with a high freq inverter and you will see curly blue smoke and fire emitting transistors.

td

[opticalmike]

Mike and TomW,

Motorhome circuit breaker panels are vastly different than home panels,

They are multifunction as follows:

1). AC power distribution panel ...main breaker and branch breakers

2). Sometimes includes transfer switch for shore power/ Generator

3) DC power distribution panel with fuses for DC in from batt and branch circuits

4) AC to DC converter to supply 12 volts to trailer loads when AC is present

5) house lighting battery charger....part of converter but has separate voltage control

6) power transfer relay.....this relay has a 120 volt AC coil but 12 volt contacts.....no AC output connected to battery input.....AC present ...DC output connected to converter box


To do solar properly you need to shut off functions 4 5 & 6......this is simple as the same wire that feeds the converter in the bottom half feeds AC to converter and power transfer relay.

All the external AC circuits are Romex type wire ( white outer jacket over black , white and bare solid wires.  There is only one stranded wire in the AC compartment that feeds the AC - DC converter normally 16 or 18 g.a.

If you put power into the AC panel from either direction (shore power plug or back feeding ) you will turn on the converter and power transfer relay same if you add a transfer switch before the converter box.

If not sure about minor wiring changes post exact model converter box, mine is B&W 6300 as are many other motor homes and I will try to walk you through this easy modification.

Due to lack of availability of G-E Pushmatics, I drilled a half inch hole in panel and added a SPST toggle switch to turn off converter portion of power panel.

By the way, I have found that IOTA brand battery floater/charger to be way more efficient for RV use so when I get a damaged B&W converter I generally wire the Iota in place of the original converter portion of power control panel. $$$. Good Iota. 45amp. =$135.  or so. Original B$W box 45a.  $$850.

Iota is way quieter <edited>and more efficient than original transformer design.

td

Dave, I believe the wire that I disconnected in this photo goes to the converter charger from the generator breaker .Also I was wondering what you thought of the grape solar 160 watt panel from a compatibility standpoint with my 85 watt panels?

thanx again
mike

[opticalmike]

Mike and TomW,

Motorhome circuit breaker panels are vastly different than home panels,

They are multifunction as follows:

1). AC power distribution panel ...main breaker and branch breakers

2). Sometimes includes transfer switch for shore power/ Generator

3) DC power distribution panel with fuses for DC in from batt and branch circuits

4) AC to DC converter to supply 12 volts to trailer loads when AC is present

5) house lighting battery charger....part of converter but has separate voltage control

6) power transfer relay.....this relay has a 120 volt AC coil but 12 volt contacts.....no AC output connected to battery input.....AC present ...DC output connected to converter box


To do solar properly you need to shut off functions 4 5 & 6......this is simple as the same wire that feeds the converter in the bottom half feeds AC to converter and power transfer relay.

All the external AC circuits are Romex type wire ( white outer jacket over black , white and bare solid wires.  There is only one stranded wire in the AC compartment that feeds the AC - DC converter normally 16 or 18 g.a.

If you put power into the AC panel from either direction (shore power plug or back feeding ) you will turn on the converter and power transfer relay same if you add a transfer switch before the converter box.

If not sure about minor wiring changes post exact model converter box, mine is B&W 6300 as are many other motor homes and I will try to walk you through this easy modification.

Due to lack of availability of G-E Pushmatics, I drilled a half inch hole in panel and added a SPST toggle switch to turn off converter portion of power panel.

By the way, I have found that IOTA brand battery floater/charger to be way more efficient for RV use so when I get a damaged B&W converter I generally wire the Iota in place of the original converter portion of power control panel. $$$. Good Iota. 45amp. =$135.  or so. Original B$W box 45a.  $$850.

Iota is way quieter <edited>and more efficient than original transformer design.

td

I guess I posted the second pic first

[opticalmike]

I should unscrew the lead on the breaker itself and marett everything up.

[tecnodave]

Mike,

It looks like there were two wires on that breaker, the one in foreground with solid copper is one of the house lighting circuits, the other one with tinned stranded wire is the converter power. Put the solid one back on that breaker and  Converter wire on a separate breaker. 
That way when at home and plugged into shore power converter can be used.

Turn on converter when on shore power and turn off when using inverter.

These breakers are SquareD Homeline. They are the most common breaker in used in the states. It needs only a 15 amp breaker. Homeline 15 and 20 amp breakers are rated to be used as switches.

This panel does not have a built in transfer switch so it will  be easiest and safest to add a outlet box wired to the output of the inverter in the shore power cord storage compartment and plug the shore power cord into that into that when using inverter. Use 10 Guage. 3 conductor wire for this as main breaker is 30 amps. You will not need another breaker for inverter.

Most class C motor homes use this simpler method where the class A coaches have transfer switches.

If you were to accidently feed shore power back into most inverters they will likely blow up so the transfer method is important.

That is not true for inverters that are specially designed to back feed the utility grid of course.

td

[tecnodave]

Mike,

I missed that part about grape solar, I think that they are 60 cell grid tie type, same incompatable voltage.  If they are 72 cell type then you will likely have a match. Cells produce about .45 volts each so my method usually gets a close match, I just count cells as far as strings go, 4 of my Siemens 36 cell panels are 144 cell string at 69.6 volts and 2 of my SunTech are 144 cell at 70.4 volts , only .8 volt mismatch less ,than .6% mismatch! you do not have to have it exact! within 2% or so will work fine.

To make best use of your existing panels seek out the 72 cell ones.

td

[opticalmike]

Mike,

I missed that part about grape solar, I think that they are 60 cell grid tie type, same incompatable voltage.  If they are 72 cell type then you will likely have a match. Cells produce about .45 volts each so my method usually gets a close match, I just count cells as far as strings go, 4 of my Siemens 36 cell panels are 144 cell string at 69.6 volts and 2 of my SunTech are 144 cell at 70.4 volts , only .8 volt mismatch less ,than .6% mismatch! you do not have to have it exact! within 2% or so will work fine.

To make best use of your existing panels seek out the 72 cell ones.

td

dave the grape solar 160 watt are 36 cell

[tecnodave]

Mike,

Probably will be a good match. Check the v@pmax voltage for each type of panel, within 1-2% will work well, if the voltage of each is way off neither panel will work at maximum efficiency and the controller will have a hard time finding the maximum power point.

Your attachment did not post and I don't have the specs for all the panels.
I take a peek at Morningstar's String Calculator because they have most panel characterstics listed in it. Temp correction and all, it will not correctly calculate for Classic as the Classic can handle 50% more power than the TriStar and the TriStar  does not have hyper VOC. But you can get an idea from it. MidNites string calculator is better for Classic but you need those specifications at hand to use it.

td

[opticalmike]

18.5 volts
Cell Size 156mm x 156mm (6.14” x 6.14”)
Module Dimension (L x W x T) 1474mm x 660mm x 40mm (58.0” x 26.0” x 1.57”)
No. of Cells 4 x 9 = 36
Weight 12.0 kg (26.4 lbs)
Cable Length 900mm (35.4”) for positive (+) and negative (-)
Type of Connector
MC4
Junction Box IP65 or IP67 Rated
No. of Holes in Frame
8 draining holes, 8 installation holes, 2 grounding holes

[tecnodave]

It looks like specs on Amazon, missing the key stuff that you really need, the electrical charastics,

Specifically you need :

Pmax :                       Maximum power
V@pmax or Vmp  :    Volts at maximum power
Voc :                          Volts open circuit
Imp :                        Current at maximum power
Isc :                           Current at short circuit

The two most important numbers are  Vmp.     The voltage that the panels work at.
    and  Imp   The current that is produced at Vmp

Best specs are from the makers themselves.

td

[opticalmike]

open circuit voltage 22.2v
current at max power point 8.65A
Voltage at max power point 18.5V

[tecnodave]

Close enough, it does not have to be exact, if within 1-2% you will not notice the difference.
It's real nice to just buy a bunch of the same stuff but that is not always practical for $wise or space wise.

td

[opticalmike]

In my combiner box there is an Equipment grounding terminal block directly below the negative busbar that the breakers are mounted to. Can I attach a copper wire on the open lug of that busbar to the equipment grounding terminal block? Then I could run a wire from the chassis ground of the inverter to that and have a better way of grounding on the inverter?? Is this practical or even necessary? I was trying to provide the best ground for the inverter short of a portable grounding rod that is installed at each campground.

[opticalmike]

What would the percentage of charge be for a battery bank of Trojan T-105's if one only charges them up to the 14.3 volts the PWM charge controller goes to (cant program higher), instead of the 14.8Volts that is recommended by Trojan? I would like to get the kid controller and am justifying it to my wife as necessary.
thanx again,
opticalmike

[dgd]

What would the percentage of charge be for a battery bank of Trojan T-105's if one only charges them up to the 14.3 volts the PWM charge controller goes to (cant program higher), instead of the 14.8Volts that is recommended by Trojan? I would like to get the kid controller and am justifying it to my wife as necessary.

Don't bother trying to justify expenditure on KID.
Just accept the fact that a commensurate value item of jewellery is probably the only acceptable solution.

As for the charge voltage being too low I would advise you to get that jewellery ASAP before the batteries sulfate up.

dgd