A common question is "how long can the WaterMate pump for?"
We've set the recommended maximum as:
10 minutes pumping during the summer (April - September), with the supplied 10W solar panel positioned for optimum sun angle, with no shade. This should be configured as a maximum of 6 minutes (3 minutes per zone) as a baseline with "hot boost" to give extra water on sunny days, when there is also more charging capacity.
This applies to both the WaterMate Pro and the Mini.
Note that charging is turned off when the internal temperature of the control unit goes above 45 degrees C, to protect the battery and prevent a fire risk. Always keep your control unit in the shade.
See the bottom of the page for how to see if your battery is charging.
Here's more background for the technically-inclined:
10 minutes maximum pumping capacity is stated as an average over multiple days, where some will be more sunny than others. It also assumes a starting point of a full battery. Pumping 10 minutes a day on a flat battery usually leads to the battery not charging well.
- A full battery will run flat in about 20 minutes of pumping (6amps/3 = 2Ah).
- A 10W solar panel in full sun with perfect alignment (900mA) will recharge the battery to full within 2-3 hours.
In reality, a 10W panel is not often giving out full capacity, due to dirt, angle of sun, temperature etc. So to be cautious we say the battery will recharge in 3-4 hours of perfect conditions. On a long sunny summer day you would potentially get two full cycles. However you can't guarantee sunny weather every day, so it's sensible to set the timer to a conservative level which can be maintained over an average week of sun (maximum 10 minutes per day in the summer, which means less on overcast days ... see the note at the top of this page).
If you have a few consecutive days of overcast weather and you continue pumping for 10 minutes each day, the battery will gradually decrease in charge and won't be able to pump for the full 10 minutes. The control unit will shut the pump off before the battery gets critically low, so no damage will occur to the battery.
Note also the time of day that you water. Watering in the morning when the battery may be less charged is more likely to lead to reduced (battery-limited) pumping times.
To water more on a hot day (which is usually also sunny), use the "hot boost" feature, which waters more when temperature is above your chosen level for a certain length of time.
Can I fit a larger solar panel, or more solar panels?
The control unit will charge at a maximum of 900mA, even if you fit a larger solar panel. However, a larger solar panel will speed up charging, because even when it's overcast, or sub-optimal angle, the panel will be able to provide more than 900mA.
A 10W panel will only provide around 1A in perfect conditions.
A 20W or 50W panel would provide full charging power during a wider range of weather conditions.
We provide solar panel splitters which allow you to put multiple 10W panels onto a single WaterMate. However they must all face the same angle, since if one is in the shade, the whole solar panel array will be adversely affected.
We also sell bare connectors for you to fit a single larger panel.
Can I charge the unit with a solar charger / leisure battery?
If you can provide power between 15V and 21V (a direct connection form a solar panel), the internal charge controller on the control unit will handle current and voltage limiting to the battery. Charging off a 12v leisure battery will not work.
If you have a separate 12v system in place, then use a Harvst mains control unit, which has a 12V power input which drives the pump directly. Your 12v system will need to provide up to 8 amps at peak current draw, with a higher inrush/surge current when the pump starts. If your 12v system can't provide a high inrush current, the control box may reboot when it starts to pump.
How do I know if the solar panel is charging?
Open the Device Control Panel on your phone, and go to Settings > Battery info. If the solar voltage is higher than the battery voltage, the unit will be charging.
Below is a diagram showing a typical charging curve (you won't see the grey battery level on your charts, this is admin-only). The yellow line shows the solar voltage (left axis) rising in the morning to a point at about 0630 when it stays flat at 18V. This is charging the battery. When the battery is full, the solar panel is not being used and the voltage rises depending on the amount of sun; up to approx 21V. At 2pm, the system water, draining the battery. The solar panel starts working again, and you can see the voltage is clamped to approx 18V (using MPPT technique in the control unit).
Why is my battery not charging?
If, even in full sunshine with your panel facing the sun, outside the greenhouse/polytunnel, you are not seeing more than 18V on the battery info screen, then your solar panel or cable is at fault.
Make sure that you are not running the pump for too long - the charging may not be able to keep up. Best practice is to set your timer for a fairly dry base-line, with short watering times, then use hot day boost to increase watering when the plants need it more, and there will also be more sun to recharge the battery.
Note that charging is turned off when the internal temperature of the control unit goes above 45 degrees C, to protect the battery and prevent a fire risk.
How long will the battery last, long term?
Full to empty is a full battery cycle, and is pushing the battery hard. The battery is designed for up to 500 cycles, so a new battery would be needed in a year or two. Using the recommended maximum of 10 minutes per day is not quite a full cycle, so the battery should last up to 2 years, after which a replacement will be needed.
We offer a return-and-replace service for new batteries, and a general control unit reconditioning (cleaning, new firmware, and any minor hardware updates possible).
For more detail, also see WaterMate battery health / lifespan.