Using a DC power charger to acharge a 12v Battery via a non MPPT solar controler

It also depends on the type of DC output power supply you have... Some will current limit (i.e., 15 volts @ 4 amps or 12 volts @ 4 amps). Others will "hiccup" (try to take output to ~15 volts, see excessive current, shut down current output, try again).

If your DC charger overheats or otherwise behaves badly, you may have to add a resistor to limit the output current to below 4 amps:

• Voltage = Current * Resistance
• R= V/I = (15 volts - 14.2 volts charging) / 4 amps = 0.2 Ohms
• Power = I²R = (4 amps)² * 0.2 Ohms = 3.2 Watt minimum power resistor rating

And if your battery is significantly discharged (i.e., ~12.5 volts when charging), you may need a larger Ohm (and Wattage) rated resistor.

-Bill

W OK, lots of questions... I take a stab at a few (others may have different answers):

Atlas123 wrote: »

-From CALLD:
An AC to DC converter may cause a ripple effect that the Charge controller may struggle with (which is not the case with Solar DC current, I guess the ripple with solar is less?)

There are lots of different types of power supplies... Some are simply a transformer and AC rectifier--And output lots of ripple current. If you have good size loads + ripple current on a Lead Acid Battery--It can cause the battery to get warm or even "micro cycle" (i.e., pull the operating voltage down below ~12.7 volts every 1/2 cycle--Then >12.7 volts on the other 1/2 cycle--discharging/charging ~60x a second).

Also if using a PWM charge controller to keep the battery properly charged, these are "on/off" cycling too... Again can cause micro cycling in some cases (float voltage ~13.6 volts or so, generally the battery is kept above 12.7 volts and does not micro cycle).

Adding some electrolytic capacitors at the battery can help reduce "ripple current" in the battery and keep it cooler too (that how I understood CALLD's answer).

-From Bill:
If the DC charger overheats that means there is an issue between the DC output amp and the Charge controller amps input and therefore may need a resistance to help dissipate the heat outside the DC charger.

"It depends". If you have an electronic power supply, they generally will "protect" themselves against excessive current and overheating. How they do this can be very different between supply models and vendors. Some will keep at "4 amps" and simply let the output voltage drop--Not problem.

However, others may try to regulate to 15.00 volts and if it takes more than 4 amps, they "shut down the output" for a short period of time (fraction of a second to a few seconds) and they try again. This type of supply may need a power resistor to prevent it operating in the "over current" output protection mode. Using a power resistor is a waste of energy--And is only used if there is no other method to fix the problem.

A standard battery charger actually has two regulation modes. A maximum output current regulation mode (near dead battery, low voltage) that holds a maximum of "4 amps". And once the battery gets most of the way charged, it has a voltage regulation mode that holds 14.40 volts--And the battery charging current falls of naturally.

On CALLDs point: The AC to DC charger is designed for variable outputs to laptops (different voltage dependent on the laptop power requirements and swapping jacks) therefore I was assuming the DC current generated would be stable enough for a laptop (therefore also for a charge controller?).

Don't know... If you have a charger designed for a specific function (laptop charging) or is a "smart charger" that can configure itself for different applications--Most of the time, these are not designed for direct connection to a DC battery pack. Lead Acid batteries are pretty rugged--But improper charging can shave years off the life of a lead acid battery (over charging, boiling dry, under charging, etc.).

I read Inverters with modified Sine wave DC output could be risky for laptops (and pure sine too expensive). Of course I may be being too optimistic (or foolish ).

Another relatively complex subject. AC to DC switching power supplies typically had a full wave rectifier and a high voltage capacitor (~380 volts) to supply power do the switching output.

If you fed these types of power supplies with MSW (modified square wave) Inverter power, the "sharp edges" of the MSW would cause excessive current to flow in the diode bridge and capacitors (ripple current)--And because of I²R heating... The high peak currents could overheat and damage the power supplies.

If you had power supplies with small transformers--The poor "power factor" again can cause over heating of the step-down transformer (and circulating currents in the steel core).

Newer/higher power switching power supplies have a "power factor corrected" front end which can work very nicely with MSW inverters--However, it can be difficult to tell which type power supply you have--So, I like to recommend TSW/PSW (True/Pure Sine Wave) inverters for people that need "reliable power" for their electronics/LED lighting/refrigerators... It is more expensive, but it can save you a bunch of money in the long term... Something like 80% of the AC appliances will work fine and 10% will have an early failure--Trying to figure out the difference is not easy.

On the other hand, there are lots of MSW inverters out there running lots of loads/cabins out there--And the folks are reasonably happy with their installations.

Here is the detail about the charger that I am hoping has the necessary capacitors inbuilt for DC output:
http://www.ebay.es/itm/251533900420?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
I guess there is no way to check this without an oscilloscope or similar?

I see:

Supports input voltage worldwide 100-260V

Generally, this "wide range" of AC power (not 120/240 VAC with a "switch" but a broad input of 100-260+ VAC Input indicates that this is a PFC (power factor corrected) power supply. So, from my experience, this would be OK on a MSW power supply.

On Bills point: Is this again something relevant to an AC to DC charger but not relevant if from a solar panel? I was hoping that with a 10amp charge controller that it could handle the amp variation from solar but also from the AC to DC charger.

You are used to Lead Acid Batteries, DC power supplies, and utility power--Etc.... These are "voltage sources". The supply attempts to hold a fixed voltage no matter the current (until it is over loaded). Even an AC Utility outlet is a "voltage source" (just an AC voltage source).

Solar panels are, more or less, "current sources". The solar panel will attempt to output a fixed current from ~zero volts to ~17.5 volts (for a 12 volt solar panel). No matter the voltage.

From an engineering point of view, these are a "very different" type of power source and the rules governing how to use them are quite different. They are not simply "solar batteries" in the sense that most people understand.

Just if interested, the setup I am planning is as such:
-Solar panels (max 40W) or adjustable AC to DC charger 15V max 4 amps-->15a fuse--> 10a Charge controller --> Diode-->15a fuse-->12V Battery (9ah or 20ah)-->(maybe 15a fuse)-->Load
-The load will have USB outputs and car plug output--> The same AC to DC charger has a car plug that can be used for DC to DC adjustable Voltage output depending on the laptop model.

The details matter... I would be hesitant to use a universal laptop power supply as your DC power source--Unless it is really cheap and you don't mind experimenting/possibly ruining the supply.

Also, the input voltage to the Prostar.... 15 volts is about the very minimum that would work with a small 12 volt battery (that probably needs around 14.2 volts to charge). And Lead Acid batteries can require anywhere from 14 to 15 volts to properly/quickly recharge... It depends on the battery type (flooded cell, AGM, GEL, SLA/VRLA), temperature, etc. What works on a warm battery may not if the battery is near freezing or below. And holding 14.2 volts for days on end can overcharge and damage the battery too.

Connecting a bunch of different devices together may not work out well.

-Bill