mppt vs pwm

[benno77gu]

hi fellas whats the better solar regulator mppt or pwm, i have a 190w rich solar panel with a mppt reg and want to use it to top up two 100ah agm deep cycle batteries on my camper will this reg be suitable, thanks

[Wizard52]

I have a Powertech MPPT for my 140 watt panel and I have seen 9.1amps going into my battery around midday so more than happy with that.
Yesterday mid afternoon with clear skies still had 6.3amps while parked in driveway.

[Drew]

I use a ctek d250s to charge 2 x 120Ah batteries in my van, solar (mppt) and dc-dc charger to charge from the car.


“The best way to cheer yourself is to cheer somebody else up.” - Albert Einstein

[Cuppa]

A decent pwm reg is better than a cheap mppt reg.

Most of the time there will be very little difference between a pwm & mppt reg, but where a quality mppt reg comes into it's own is when it is most needed, ie at times of poor solar conditions.

Most if not all the mppt regs supplied with the cheap solar panels cannot be considered 'quality', & thus any medium priced pwm reg is likely to be better.

From friends who have a strong tech background, who have examined this issue, most mppt regs that do not cost a minimum of several hundred dollars are unlikely to be any better than similar priced pwm regs. I don't understand the maths, but it all has to do with the charging algorithms the makers use, & I am led to believe there are algorithms & algorithms. A case of getting what you pay for.

I am happy with my Redarc BCDC1240 an mppt reg. I am equally happy with my Morningstar Tristar reg, a pwm reg.

Bottom line - if you want a decent reg you have to pay for one. I consider most, if not all regs supplied with eBay solar panels as throw away & replace items. They will work, but most will work better, & have other desirable features like temperature compensation. A good reg will look after batteries better, giving them a longer life.

Cuppa

[Maxhead]

Thanks Cuppa great info as always.

Sorry Benno but on a similar subject, what is the connection procedure for the MPPT regs?

Correct me if I'm wrong but you need the battery (load) connected before you switch your MPPT On, is this correct? and with PWM this is not necessary?

This bit has always confused me.

[Cuppa]

I'm not aware of any difference in connection procedure between MPPT or PWM.

Many folk don't bother using the 'load' function of their regulator, I'm one of them (with a minor exception - in our bus I have a Steca regulator & have a single red LED connected to the 'load' connection. This gives us an automatic nightlight. Comes on when solar input ceases, & goes off when the sun comes up in the morning - uses the solar panels as a 'photosensor'). This may be particular to the Steca reg & their clones?? I've never really heard a convincing reason for why it is worth using the load function for anything else. I think they usually have a Low Voltage disconnect built in, so you don't discharge your battery too far, but generally these are really set far to low to actually protect the batteries (like most of the 12v fridges). If a reg had a 'settable' LVD & a reasonable number of amps the 'load' function could handle it could be worthwhile, but otherwise I reckon it's largely a waste of time.

Most of my experience has been with solar panels permanently mounted on the roof of the bus, so I haven't needed to be concerned about connecting/disconnecting much. Portable panels are relatively new to me. I have heard a couple of stories of people frying their cheap (stuck on back of panel) regulators when connecting them in full sun. Not sure if it's necessary, but when connecting my portables to the reg in the patrol I first connect all panels together, but before making the final connection to the reg in the vehicle (anderson plug) I lay the panels on their face or cover them, so they are not putting out any current. Whether I really need to do this or not I'm not sure, but better safe than sorry.

Cuppa

[benno77gu]

hi cuppa do you know the preferred voltage to charge the agm deep cycle batteries, thanks mate

[Cuppa]

hi cuppa do you know the preferred voltage to charge the agm deep cycle batteries, thanks mate

Hi Benno, it varies a bit between manufacturers, with American made AGM batteries generally being a bit lower(14.1v) than the Chinese made batteries (14.4 -14.6v). It can also vary between different types of AGM from these same manufacturer. (e.g., DC series, Golf cart batteries, HGL series etc etc) Generally the DC series are considered the best option for our sort of purposes, but all of them will work. DC series will tend to be longer lasting though.
My DC series Ritar (Chinese) recommended bulk charge rate is 14.6v, but my reg only takes them up to 14.4/14.5v. This isn't a problem, just means they don't charge quite as quickly. My DC Fullriver's (Chinese) are 14.5v.
Generally most AGM's will be around 14.4 to 14.6 but best to google your brand & see what the manufacturer's recommendation is if your reason for wanting to know is so you can select an appropriate charger/regulator. If you already have a charger/reg which has a bulk charging voltage of around 14.4/14.5 it will probably be close enough.
Better regs allow you to set the charging voltage. They also have temperature compensation, usually increasing voltage by around 0.03v for every degree.C above 20 degrees.C. In hot weather it is not uncommon to see close to 15 volts charging.

Float voltage (what the battery is held at by a smart charger once fully charged) is commonly around 13.6v to 13.8v. Interestingly my Redarc charger regulator floats the batteries at only 13.2v /13.3v. I can't see why this should be a problem but am uncertain of why Redarc decided to do this.

Cuppa

[oncedisturbed]

Thanks Cuppa great info as always.

Sorry Benno but on a similar subject, what is the connection procedure for the MPPT regs?

Correct me if I'm wrong but you need the battery (load) connected before you switch your MPPT On, is this correct? and with PWM this is not necessary?

This bit has always confused me.

Mine came in today (mppt controller 10 amp) and there is no switch for it, plug in the leads and attach to battery.

1 thing I did notice though is the charge indicator light is on almost instant from opening the panels and then load light when attached to battery and both remained lit when everything is disconnected???