June 21, 20242 yr Hi Help!(please) I have a borehole and pressure pump supplying a number of cottages using a 0.75kw pump. When Eskom is off we have no water. I am thinking of a few panels and an invertor to run the borehole pump to fill the elevated storage tank. I have a 3 kw smart invertor to which I can add panels. I am trying to delay buying batteries . Does this make sense or is there a better solution? TIA Brooks
June 22, 20242 yr On 2024/06/22 at 9:11 AM, brooks said: Does this make sense or is there a better solution? Only some inverters can operate without panels a battery. Pump motors have a high peak starting current, which might necessitate a soft starter of some sort; I'm not familiar with these. The ideal solution would be an inverter designed for this, I think they are called solar pump inverters or similar. I don't know if they can have a battery added later as an option. These know about starting motors with ramping voltage (not suitable for most loads, but ideal for starting pumps from limited solar power). Something like this: Edited June 23, 20242 yr by Coulomb "without panels" → "without a battery"
June 22, 20242 yr 7 hours ago, brooks said: Hi Help!(please) I have a borehole and pressure pump supplying a number of cottages using a 0.75kw pump. When Eskom is off we have no water. I am thinking of a few panels and an invertor to run the borehole pump to fill the elevated storage tank. I have a 3 kw smart invertor to which I can add panels. I am trying to delay buying batteries . Does this make sense or is there a better solution? TIA Brooks Some assumption on this post. Inverter is a 24V 3kW. Even cheaper lead acid batteries will work if pump only runs during sun periods to fill the storage during peak sun. Battery is only used for assisting in starting as the panels cannot provide the I rush. Ensure panels are around 1.5kW. Ensure that one uses a differential level control to limit starts of pump. Indicate the actual storage size and pump actual volume pumped per hour tested while there is grid. Reason is to have a feel for how many hours a day the pump needs to run. Use of a remote timer desirable to prevent running the pump from the battery when there is low irradiation for longer than say 30min a day. Low irradiation can still recharge battery even when pump is not running to use for a short period say after 14h for a splash and dash. Ensure that a battery monitor is used to prevent lead acids to drop below 12.1V per battery to prevent running the pump. The above is only looking at the 0.75kW pump mentioned. This battery would perform like a car starting battery and could last about 3 yrs or more. The size of the borehole pump is not mentioned and can turn this whole reply on its head. I'm ducking and diving for daring to mention lead acids. 😀😀 Edited June 22, 20242 yr by Scorp007
June 22, 20242 yr 5 hours ago, Scorp007 said: I'm ducking and diving for daring to mention lead acids. 😀😀 No dont, lead acid makes perfect sense. Even low Ah battery will help If have experimented with. 75kW pool pump with Axpert in batteryless mode. 1. The pump will not start easily without the torque current from battery or grid , even if pv is good. 2. The dips in pv is no good for the pump and the battery must fill that valleys. The inverter will lower its ac accordingly and this can overheat the motor. Agree, monitor the max battery consumption and switch off if pv yield is poor. And of course if there is grid, set priority to pv, then grid, then battery. So if grid is available it fill the valleys left by pv. This means inverter must blend ac with pv. Edited June 22, 20242 yr by BritishRacingGreen
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