48V Solar system / 24V water pump

[patrickboileau]

I'm quite the beginner here, so excuse some of the ignorance. We are off grid cabin. I've got the growatt 3000 inverter, and a 48V battery set up (8 x 6V). My water pump is 24V and so we connected it directly at 24V (just 4 batteries). The pump is about 100ft way from the solar system. When I tested my batteries this spring, a couple of them were worse off than others and don't seem to be recovering as well. Is this set up hurting my batteries? Is there a better solution?

Thanks for any advice/help!

 

[wpns]

Unless you gave an inter-battery equalizer (and even probably if you do) this is a really bad idea. You need a 48->24V buck converter sized to run your pump.

 

[Mattb4]

Have you considered changing your pump to AC? A 100ft run at 120vAC has very little loss vs a 24vDC run. If you have to stay with a 24vDC pump because it is down in the well you might want to consider a dedicated 24v battery just for it with its own charger from your Growatt. Some loss of efficiency but your present setup is not optimum for your batteries.

 

[x98myers7]

I would check the specs on the pump, because many DC water pumps are rated for a wide voltage range, 30-300v. you can probably run it on 48v. if not, upgrade to a grundfos and run it at 48v.

 

[v_green57]

I would check the specs on the pump, because many DC water pumps are rated for a wide voltage range, 30-300v. you can probably run it on 48v. if not, upgrade to a grundfos and run it at 48v.

"Danger, Will Robinson!"

Don't assume this. Given his description of "off-grid cabin", he may have a RV diaphragm pump for fixtures in the cabin. Those definitely will NOT tolerate anything but the voltage they are rated for.

 

[wpns]

"Danger, Will Robinson!"

Don't assume this. Given his description of "off-grid cabin", he may have a RV diaphragm pump for fixtures in the cabin. Those definitely will NOT tolerate anything but the voltage they are rated for.

Yeah, let's start with what he has now before optimizing it. https://www.amazon.com/ECO-WORTHY-Submersible-Alternative-Energy-Battery/dp/B015QRXWA6 for instance only draws 4 amps, so the answers are going to be all over the map until we know...

 

[patrickboileau]

It's a "Jetmaker" https://www.alibaba.com/product-detail/Jetmaker-24v-dc-solar-submersible-pump_60697558971.html

 

[SupraSPL]

Maybe put a small-ish 24V battery near the pump and use a small 48V to 24V buck to keep it charged

 

[v_green57]

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www.amazon.com

I always oversize things. 10A is 2X what you are supposed to need, per the data sheet.

You should check the voltage drop on that 100 ft. of wire. It would be better to run the 48V out to where the pump is and do the conversion to 24V there.

 

[wpns]

It's a "Jetmaker" https://www.alibaba.com/product-detail/Jetmaker-24v-dc-solar-submersible-pump_60697558971.html

That's the Eco-Worthy I pointed at from Amazon, or a clone thereof), which in turn is a design-clone of the Shurflo 9300. But then the Shurflo is a kilo dollar, and the clones are $65, so just stock lots of spares (one Eco-Worthy lasted over a year, a second one lasted about 6 months).

 

[patrickboileau]

Loading…

www.amazon.com

I always oversize things. 10A is 2X what you are supposed to need, per the data sheet.

You should check the voltage drop on that 100 ft. of wire. It would be better to run the 48V out to where the pump is and do the conversion to 24V there.

Thanks for all the insights. So by connecting the water pump wire at 48V at the batteries (instead of 24V) and stepping down with a 48>24 buck converter, that would help my with the battery damaging issue?

 

[MrBuisson]

it will help. Also, place the buck converter close to the pump - far away form the battery. This will reduce the cable losses by reducing the voltage / increasing current at the last moment. Don't forget a fuse at the battery contact in case someting happens to your cable / buck converter / pump.

for the batteries ... you are charging all your batteries in series so they get the same charge current - but you discharge half of them independently.
the issue come with charging back. How do you recharge the batteries used for the pump without charging those above them ?
you end up with a mix of overdischarged lower battery and overcharged upper batteries. both are bad so you actually need to check all of them. It's not burning only because you have (I guess) lead batteries. Lithium would have protested in a much more dstructive way.

 

[v_green57]

Thanks for all the insights. So by connecting the water pump wire at 48V at the batteries (instead of 24V) and stepping down with a 48>24 buck converter, that would help my with the battery damaging issue?

You should. if possible, disassemble the battery bank and charge each one individually to Float. Then reconnect them. This should help minimize the damage you have already done, but it won't undo it completely.