PWM charger so slow

teopap · August 2019

So I bough a few days ago a 300W solar pack.

- 2 x 150W 12V panels connected in parallel

- One 40amps PWM charger (the common blue one)

- One 1500W pure sine wave inverter

- 180AH Lead Deep Cycle battery

For the first day everything worked great as the batery full. As the days were passing, the charger couldn't even make it to 12.5V in full hot summer sun throughout the day. I started charging at 13:00pm at 12.3V and at 19:00 where I turned the panels to stare directly at the sun the voltage went up to 12.6 barely. Under normal condition, I think It should have made it to at least 13.5V right ? (the inverter was shut down to prevent losses during the charging state)

What worries me, it's the PWM charger. The LCD arrow that is next to the solar panel and goes to battery is blinking. In the manual it says when it is blinking it means it's in float charging mode. If I am not mistaken, float mode is enabled when the battery reaches at 13.7V so it starts charging slowly as it's almost full ? Why then it uses float mode while it is in so low voltage ?

Yesterday in fact the inverter shut down due to low battery voltage. The float mode is set in the PWM charger at 13.7V. This is a point that starts going into float mode ? Maybe I need to set it much lower so it goes into bulk mode ? Bulk mode is the "arrow" staying on the screen, not blinking. Never seen it staying static at the screen....

Maybe I should change the battery type ? Now it's currently at 601...

Thank you for your assistance.

mcgivor · August 2019

Think of the battery as a bank account, you can withdraw as long as there is a sufficient ballance, once the ballance is depleted no withdrawals can be made. When the daily withdrawals are greater than the daily deposits the ballance the account ballance starts to become depleted. This bank however only bank allows withdrawals to a certain point, there needs a minimum ballance available to keep the account alive and there is no overdraft protection, so the daily deposits need to exceed the daily withdrawals.

When designing a system it's best to start with the loads, once a baseline load is established, the battery capacity to support the loads is determined, the final step is calculating the solar array capacity to sufficiently recharge the battery. Geographical location as well as hours of unobstructed sun play a significant role in determining the array capacity.

There are glaring deficiencies in the described system on face value, those being inverter too large for the battery capacity and the array being too small for the battery capacity but without load values its near impossible to offer any meaningful information.

With a lead acid battery the voltage should reach ~14.4V depending on construction and temperature, it should be held at that value until current diminishes to a certain level, ~2% of battery capacity, before transition to float.

My suggestion is to stop doing what you're doing, start fron the beginning again with the loads and time of use. Reverse engineering is extremely difficult and it would appear you're way out of the ballpark currently.

Don't feel bad it's common to make mistakes, we've all made them and you've come to the right place to get assistance.

Welcome to the forum.

teopap · August 2019

Thank you for your reply. Yes I know that the inverter is big for that battery, but the solar technician told me it's not a big deal and it should not be a big problem for your setup. Apparently it was. I don't have any heavy loads, just using a 40W 32'' LED TV 3-4hrs a day, LED Lights in the house only when really needed at night and a WiFi VDSL router 24/7. Probably there's a lot of consumption from the standby devices that I can't cut off (as I'm using a 4kW gasoline generator for those) such as oven, stove, microwave oven, dish washer, A/C unit and these consume power on standby and can't be disconnected as there is no outlet for them, just a wire directly in the interior wall cables.

I realized that I probably used those days the wrong battery charging type, it took a lot of search and I realized that I was charging the battery to 601 mode which is AGM battery while mine is a flooded lead battery (603) (and the 602 mode for GEL). The charge controller manual is a joke. I hope I didn't destroy permanently the battery.

I live in Greece so at the moment the sun angle is great and the outside temperature is 40°C.

Thom · August 2019

You could list the components you by manufacture. The common blue one is a bit vague. Tiny battery for 1500w inverter.

BB. · August 2019

As the guys said above... Design to support your loads, or at least, design a "balanced" system.

AC inverters are "cheap", so most people get a very large AC inverter and small battery bank and solar array (more expensive components).

For example, a 180 AH 12 volt flooded cell lead acid battery would normally be coupled with a 450 Watt solar array and AC inverter (typical maximum supported devices... 1/2 those values are typical/nominal suggested array/loads).

A 180 AH @ 12 volt battery will be drained:

1,500 Watt inverter * 1/0.85 AC inverter eff * 1/10.5 battery cutoff = 168 Amp max continuous current @ 12 volt bank

So, your battery will be sucked dead in about 1 hour or less... And really could only reliably support that load for 30 minutes or less (from full charge, assuming battery could even support C/1 discharge rate--Which an FLA battery cannot really do that for more than a few seconds or minutes typically).

If you need 1,500 Watts for only a few minutes a day--Then this system could work (using AGM or GEL batteries)--But usually most people want many hours of energy usage per day... For example 2 days of energy usage, 50% maximum discharge (for long battery life), and 5 hours per night, the 180 AH @ 12 volts will reliably supply around:

180 AH * 12 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge * 1/5 hours per night = 92 Watt load @ 120 VAC for 5 hours per night for 2 nights

And a 1,500 Watt AC inverter may draw ~10-30 Watts just by itself (larger inverters have greater Tare draw)--And your system could end up supplying 1/3rd of your energy just to run the "oversized" AC inverter (a 300 Watt inverter will draw around 6 Watts Tare).

-Bill

teopap · August 2019

Thank you for your reply. Yes I know that the inverter is big for that battery, but the solar technician told me it's not a big deal and it should not be a big problem for your setup. Apparently it was. I don't have any heavy loads, just using a 40W 32'' LED TV 3-4hrs a day, LED Lights in the house only when really needed at night and a WiFi VDSL router 24/7. Probably there's a lot of consumption from the standby devices that I can't cut off (as I'm using a 4kW gasoline generator for those) such as oven, stove, microwave oven, dish washer, A/C unit and these consume power on standby and can't be disconnected as there is no outlet for them, just a wire directly in the interior wall cables.

I realized that I probably used those days the wrong battery charging type, it took a lot of search and I realized that I was charging the battery to 601 mode which is AGM battery while mine is a flooded lead battery (603) (and the 602 mode for GEL). The charge controller manual is a joke. I hope I didn't destroy permanently the battery.

I live in Greece so at the moment the sun angle is great and the outside temperature is 40°C.

Photowhit · August 2019

Let's look at your loads.

The loads you are speaking off are

teopap said:

40W 32'' LED TV 3-4hrs a day,

Okay that's 40 watts an hour for 4 hours or 160 watt hours + your inverter likely uses 20 watts to run the minimal load so we'll add 20 x 4 = 80 watthours + 160 = 240 watt hours.

teopap said:

LED Lights in the house only when really needed at night

Okay, no firm figures here, but say 2hours during the day and 3 bulbs using 7 watts for 4 hours at night = 3x7x4 = 84 watt hours.

teopap said:

WiFi VDSL router 24/7.

So I will assume you have found a 12 volt router, since you run it 24/7 and you are turning your inverter off at night. They use 4-20 watts, I'll use 10 x 24 = 240 watt hours.

teopap said:

Probably there's a lot of consumption from the standby devices that I can't cut off (as I'm using a 4kW gasoline generator for those) such as oven, stove, microwave oven, dish washer, A/C unit and these consume power on standby and can't be disconnected as there is no outlet for them, just a wire directly in the interior wall cables.

All those things will add up, Not sure if you are running more than you have suggested, but just run an extension cord and turn off the other home appliances. If your inverter is on for more than the 3-4 hours to run the Tv then you are just inviting energy drawn from your system.

To run this items you have loads totaling240 + 84+ 240 + 564 watt hours.

Your system;
2 - 150 watt solar panels, they can produce close to their rated amperage for a 12 volt system. Perhaps your charge controller can tell you how much amperage they are producing. To guess 300 watts of 12 volt panels will produce about 15 amps. I would expect that for 5-6 hours during the day, but it appears you either have bad access to the southern sky, or
no safe place to leave the panels out....

teopap said:

I started charging at 13:00pm at 12.3V and at 19:00 where I turned the panels to stare directly at the sun the voltage

13:00 half of the available charging is done...

I'd suggest that you are maxed out at the load you have suggested, if I'm close, lots of guesses...

PWM charger so slow

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