Tristar MPPT-45 and eliminating the converter

doug30293 · January 2016

My 5th wheel trailer has a rather dated converter/charger (2002). I am in the process of selecting solar components for boondocking. Oil Pan 4 seems to be having good luck using his solar charge controller as a converter. I am wondering if it would be practical to build/purchase a simple power supply to work in conjunction with the PV array and do all my charging through the charge controller. A separate converter/charger for shore power seems redundant since the Tristar MPPT-45 is capable of properly servicing the batteries as long as it has incoming power. Is there any reason why I really need a dedicated converter/charger?

mike95490 · January 2016

Tristar MPPT-45 can ONLY accept solar PV power, not from a shore cord.

animatt · January 2016

Well I believe more accurately would be to say it only accepts DC input. There is a wind mode for the Tristar mppt controllers.

You could possibly get away with finning a thru a transformer to drop voltage a bit then to bridge rectifier. Then finally to the mppt charge controller.
That scenario is hard on components and may require a bit more processing of electricity before it is sent to the mppt controller.

But I guess your answer would be much simpler for the average Joe to understand.

doug30293 · January 2016

I can emulate the DC signature from the PV array such that the MPPT-45 doesn't know the difference. So the question still stands. Is there any reason to have a dedicated shore power charge controller when the only thing missing from the MPPT is an input voltage when the sun isn't shining?

mike95490 · January 2016

doug30293 said:

I can emulate the DC signature from the PV array such that the MPPT-45 doesn't know the difference. So the question still stands. Is there any reason to have a dedicated shore power charge controller when the only thing missing from the MPPT is an input voltage when the sun isn't shining?

Well, that is actually a $3,000 trick to emulate a PV panel (truly emulate it). A good fake could use a power resistor as a ballast to limit current, a better fake is a active resistor. But easier is to get a decent AC mains battery charger. What is your battery voltage? There are decent chargers for 12 & 24V banks. With shore power, you don't need 45A, you have power for hours to charge with,

48V, maybe getting a dedicated supply and ballast resistor is good enough. The trick is to not let the MPPT suck so much power from the power supply that it cooks the supply, nor to let a "stiff supply" cook the MPPT.
PV panels are Current sources, not Voltage sources, and wind turbines have the internal winding impedance that helps limit amps.

doug30293 · January 2016

Another method of current limiting is a transformer wound for loose coupling of the windings, the opposite of a "stiff supply." The battery bank is four T105's in series/parallel for 12V. Iota has a 45 amp charger for about $180 which may not be much more costly than rolling my own. So the next question is what methods are commonly used for switching between the PV/MPPT and the line voltage charger?

mike95490 · January 2016

Generally, all charging sources and loads are connected permanently (bolted) to the batteries, (With proper fuses or circuit breakers). The IOTA has large filter caps which spark a bit when you connect to the battery bank, leave it connected all the time, and leave the MPPT connected all the time, If both units are working right, they should throttle back independently as the battery reaches full charge,

doug30293 · January 2016

Thanks Mike, that was the information I needed.

scrubjaysnest · February 2016

Removed our converter last year; been doing fine with a TS-45 PWM. About three times last summer we had shore power and I hooked up the smart charger we carry just in case.

Shadowcatcher · February 2016

Progressive Dynamics make a replacement head unit that is three stage converter http://www.progressivedyn.com/pd4600_converter_replacement.html I for one would not want to have a converter as well as solar.

Shadowcatcher · February 2016

Progressive Dynamics make a replacement head unit that is three stage converter http://www.progressivedyn.com/pd4600_converter_replacement.html I for one would not want to have a converter as well as solar.

Tristar MPPT-45 and eliminating the converter

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