Do most people find that two pump 5min watering within an hour, back to back, is possible esp. on a grey day ? Advise
Also, I have a 25W solar panel in my greenhouse with control panel, 12V lead acid battery, could this be utilised or parallel spliced to the control unit for a backup ? I am going away from month in summer and a little twitchy. Any electronic brains here for advice Appreciated.
Hi there - the battery level and pumping capacity depends on more than just the current day's solar, it's quite complex; a combination of previous days lead-up, the time of day that you pump [based on when the sun came up and the battery was charging], how much current the pump is using and so on.
The maximum battery capacity for a single full charge [call it 2Ah factoring a safety margin], and pump drain of 4 amps [which again will vary based on what drippers / sprayers you have], gives in theory 30 minutes of pumping to completely flat. 4A is near the maximum C rating of the battery, where it won't be able to provide the full 2Ah, so let's take that to 20 minutes to be conservative. We have tested this and it's a realistic figure.
Boxes prior to V9 have a maximum charge rate of 400mA, which is possible from a 10W solar panel in decent sun, and a 5W at a push in full direct sun. At 400mA, the 2Ah battery will be replenished in 5 hours [assuming you get the full sun throughout those 5 hours]
That's the 1-day-full-sun-full-drain theory, without factoring in when during the day the charging and pumping are. We've done a 1-week partial sun calculation ( I won't share here as it's a spreadsheet ) which brings us to the more conservative "10 minutes per day" figure.
Adding a bigger solar panel will help; you are more likely to reach the maximum 400mA charge for a longer period during the day. With V9 and more recent boxes, maximum charge current is 1A.
Ultimately, it also comes down to how much water the plants need in varying weather. Cooler grey days ... less thirsty plants so a lack of full charge isn't necessarily a problem. Planning for multiple grey days ending up with a low battery, then a scorcher of a day when plants need more water ... we'd hope that in summer with a good solar panel placement you would get that full charge [5 hours as above] by midday. So plan longer pumping periods for the evening when you are most likely to get the full time period from a full battery.
As for your 12v system, I'm afraid that's not compatible; the Harvst system is Li-ion and 16.8V at peak charge. You could replace our 10W panel with your 25W one, but it would need to be connected only to the Harvst box and nothing else.
In summary - yes you should be fine with 5 minutes back to back.
Many thanks for this excellent reply. I , if I get into trouble,( which by the sound of it, is unlikely ) will plan pumping later on in the day and stagger the two solenoids.
Appreciated George
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Also, I have a 25W solar panel in my greenhouse with control panel, 12V lead acid battery, could this be utilised or parallel spliced to the control unit for a backup ? I am going away from month in summer and a little twitchy. Any electronic brains here for advice Appreciated.
The maximum battery capacity for a single full charge [call it 2Ah factoring a safety margin], and pump drain of 4 amps [which again will vary based on what drippers / sprayers you have], gives in theory 30 minutes of pumping to completely flat. 4A is near the maximum C rating of the battery, where it won't be able to provide the full 2Ah, so let's take that to 20 minutes to be conservative. We have tested this and it's a realistic figure.
Boxes prior to V9 have a maximum charge rate of 400mA, which is possible from a 10W solar panel in decent sun, and a 5W at a push in full direct sun. At 400mA, the 2Ah battery will be replenished in 5 hours [assuming you get the full sun throughout those 5 hours]
That's the 1-day-full-sun-full-drain theory, without factoring in when during the day the charging and pumping are. We've done a 1-week partial sun calculation ( I won't share here as it's a spreadsheet ) which brings us to the more conservative "10 minutes per day" figure.
Adding a bigger solar panel will help; you are more likely to reach the maximum 400mA charge for a longer period during the day. With V9 and more recent boxes, maximum charge current is 1A.
Ultimately, it also comes down to how much water the plants need in varying weather. Cooler grey days ... less thirsty plants so a lack of full charge isn't necessarily a problem. Planning for multiple grey days ending up with a low battery, then a scorcher of a day when plants need more water ... we'd hope that in summer with a good solar panel placement you would get that full charge [5 hours as above] by midday. So plan longer pumping periods for the evening when you are most likely to get the full time period from a full battery.
As for your 12v system, I'm afraid that's not compatible; the Harvst system is Li-ion and 16.8V at peak charge. You could replace our 10W panel with your 25W one, but it would need to be connected only to the Harvst box and nothing else.
In summary - yes you should be fine with 5 minutes back to back.
Appreciated George