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Registered Users Posts: 3
I am from Namibia,Africa.

Use to do a few solar intallations for friends,but this time one of my friends ask me to help him install a solar system for his inline pressure pump.And after a lot of trouble we still get it to work.Here is what we have...

Pump
380 watt 220 ac set to 2 Bar pressure

3 x 200 watt 12 volt panels

2 x 150 AH deepcycle battries

30 Amp controller

2000 watt cont power and 4000 watt peak power

• Solar Expert Posts: 963 ✭✭
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we still get it to work.Here is what we have...

You say you already have it working. What do you want to know from this forum. If you have it working good you sould be telling us the problims you had and how you fixed them. I for one would like to hear about that.

What do you want to know?
gww
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moerboer wrote: »
Pump
380 watt 220 ac set to 2 Bar pressure
3 x 200 watt 12 volt panels
2 x 150 AH deep cycle batteries
30 Amp controller
2000 watt cont power and 4000 watt peak power
Are you saying you are still trying to get it working?

First, the 200 Watt solar panels... What is the Vmp/Imp (voltage maximum power/current maximum power) of your panels... 200 Watt "12 volt panels" (typically Vmp~18 volts) are pretty rare these days (at least in the US/North America).

Next, the 2x 150 AH deep cycle batteries... Are these 12 volt batteries, two in parallel, for a 12 volt @ 300 AH battery bank? If so, the rough power you can get from such a battery bank:
• 12 volts * 300 AH * 0.85 inverter eff * 1/20 hour rate = 153 Watts average long term discharge (optimum AC power)
• 12 volts * 300 AH * 0.85 inverter eff * 1/8 hour rate = 382.5 Watt average long term discharge
• 12 volts * 300 AH * 0.85 inverter eff * 1/5 hour rate = 612 Watt maximum continuous power (pretty hard on the batteries)
• 12 volts * 300 AH * 0.85 inverter eff * 1/2.5 hour rate = 1,224 Watt maximum surge power (seconds to minutes draw)

Using Solar Electric Handbook, we can estimate the amount of sun you will receive for a 600 Watt array (note, software bug, use "facing south" for array, even though you would face it north as you are south of the equator):

Windhoek
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 67° angle (from vertical):
(For best year-round performance)

Jan
Feb
Mar
Apr
May
Jun

6.26
6.17
6.34
6.33
6.62
6.29

Jul
Aug
Sep
Oct
Nov
Dec

6.34
7.04
7.17
6.70
6.57
7.36

Assuming this is near where you live/similar climate, you have lots of sun there (and not much rain?):
• 600 Watt array * 0.52 off grid system efficiency * 6.26 hours minimum average sun per day = 1,953 Watt*Hours per winter day

Your 380 Watt motor may draw upwards of 5x 380w = 1,900 Watts starting

And, depending on how your motor is rated (i.e., 380 Watts output power may draw upwards of 760 Watts input--worst case), you could expect it to run:
• 1,900 WH per day * 0.85 AC inverter eff * 1/760 Watts running load = 2.125 Hours per day minimum run time (on a sunny day)

For average loads, you should only expect to run ~66% to 75% of average power every day (leave a little bit left over for bad weather, optional loads, etc.).

Your battery bank may be a bit on the small size, and the AC inverter may be way over-sized--The maximum practial AC inverter that your present battery bank would support will be around 600-800 Watts or so. A 2 kWatt inverter would "kill" the battery bank if operated at full power at night. The motor is right on the ragged edge of running on your battery bank.

Assuming the batteries are in good shape and the solar array is charging OK:

600 Watts * 0.77 panel+controller derating * 1/14.5 amps = 32 Amps "typical" maximum charging current. Your 30 amp PWM charge controller may be too small for your 600 Watt array--PWM controllers do not take well to being "over paneled" (too much current, charge controller may shut down/get overheated/damaged).

Lastly, look at your wiring from the battery bank to the AC inverter--Assuming 1,900 Watts of starting power (yours may be lower starting power):
• 1,900 Watts * 1/0.85 inverter eff * 1/10.5 volts inverter cutoff = 181 Amps of worst case 12 VDC starting current

So--you need to check the wiring on your battery bank... It needs to be short/heavy copper cables from the batteries to the AC inverter. Too long of cable, too small of diameter, and the resistance will cause too much voltage drop from the battery bank (if you assume 11.5 volt battery under load, and 10.5 volt inverter, you can only have 1 volt drop).

Your actual starting current is probably less than 181 amps--But it sounds like (if you hare having problems) either the battery bank is not capable of supplying the starting current for the motor and/or your wiring has too much voltage drop (by the way, review this website for "proper" battery wiring).

We would also need to learn more about your water pumping needs and setup... A 380 Watt water pump is quite a bit of power for a domestic water system (sink, shower, etc.). You might be better off looking at a 12 volt (or 24 volt) DC pump (typically used in Recreational Vehicles/Caravans/etc.). Do you have a pressure tank to store up water pressure from the pump?

Note that the links provided are to our host in the US--And examples of classes of products you may want to think about using... Understand that you should purchase locally to ensure you get good support from local vendors.

Does this help?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 3
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BB thanks a lot, this really helps.
To answer the questions, the system does not work, infact it damage the pump to a stage where it wont run on any power Anymore.The panels is max 18v.the battery bank is connected to deliver 12 volts.Cable from battery to inverter is 8 mm.

This pump is used as a irrigation pump and a householp pressure pump.It has no pressure tank, only a automatic kickin switch when pressure in pipeline drops.

What system would you recommend for this pump?
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good job bill
gww
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MoerBoer,

Very simple question with very complex/detailed answers. I will try to give you short answers (not my usual style)--And if they do not make sense, I will go into more details.

This is a bit difficult, two people separated by a common language (American English with American + English units; vs your English with metric units).

First, the more simple question... Is your wire 8mm or 8mm2? If it is 8mm wire, that is very large diameter and 8mm2 is not near as large...

Also, need to know how long the cable run is between the battery bank and the AC inverter DC input.

Second--Water pump... Lots of questions there.
• Basically what will you use the pump for?
• How many liters per minute at what pressure will you need to pump?
• Does the pump need to cycle on/off based on water pressure or tank level (as in transfer pump)
• How many hours per day does the pump run (i.e., low or high duty cycle)

For example, here is a specification sheet for a simple 12 volt DC pump that is used in a small home or Recreational Vehicle (around USD\$115):

http://www.solar-electric.com/lib/wind-sun/2088-443-144.pdf

At 2bar and ~ 9 liters per minute, it will use around 8 amps @ 12 volts or ~ 96 Watts...

How does that pump specification meet your needs (or not)?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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moerboer wrote: »
I am from Namibia,Africa.

Use to do a few solar intallations for friends,but this time one of my friends ask me to help him install a solar system for his inline pressure pump.And after a lot of trouble we still get it to work.Here is what we have...

Pump
380 watt 220 ac set to 2 Bar pressure

3 x 200 watt 12 volt panels

2 x 150 AH deepcycle battries

30 Amp controller

2000 watt cont power and 4000 watt peak power

There is a lack of necessary detail in this data.

How many Volts is the pump? How much power does it really draw? If this hasn't ben measured you're in the dark.

What are the actual specs on the panels? 200 Watts is unusual for a "12 Volt" panel which would have a Vmp around 17-18.

Batteries configured for a 12 Volt system or 24 Volt? Either way there's not much stored power there: about 1800 Watt hours which with zero losses (which is never the case) and assuming the 380 Watt load is correct would be 4.5 hours run time maximum. Further to that the start demand of the pump (again making design assumptions here) would be near 160 Amps on the DC side at 12 Volts and this would flatten that battery bank instantly, meaning the pump would not start much of the time.

30 Amp controller of what type? If it is PWM you may be losing some potential charging power. A 200 Watt 12 Volt panel could actually put out 11 Amps each, so all three in parallel would exceed the controller's rating.

What kind of inverter is used? If it is MSW type then there is even more loss and less efficiency for running the pump motor. A poor quality inverter may not start the motor at all, even with sufficient power "behind it".

The devil, as always, is in the details.
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another point may be the type of output of the inverter. if sine wave then that is fine, but a square wave output could destroy items with induction coils like a pump.
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