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rob1210 · Nov 20, 2023

Hi I have 3x12v 110ah battery in parallel connecting to 2x170w solar panels a pvm controller connecting to a 3500w/7000w peak also a smart charger will be connected will this be enough to power a 2000w hottub the batteries are lead acid will the controller stop them discarging below 50% I do plan to change to mppt.thanks

SamDeleted · Nov 20, 2023

rob1210 said:
Hi I have 3x12v 110ah battery in parallel connecting to 2x170w solar panels a pvm controller connecting to a 3500w/7000w peak also a smart charger will be connected will this be enough to power a 2000w hottub

Hi Rob sadly I think your system is way too small to run a hot tub,

12v/110ah leisure batteries have only 660wh usable capacity (50%dod)

660wh X 3 = 1980wh (1.98kwh) ... so enough to power your hot tub for 1 hour

Your 2x170w solar panels will make average of 1,700wh per day south facing in summer , a LOT less in winter (350wh per day)

WindWizard · Nov 20, 2023

No it does not look good for you. The batteries are 110 x 12 = 1320 watts each. Lead acid you can only use about 50% so that means you have 1320 x 3 = 3960 watts /2 = 1980 watts available. A 2000 watt hot tub will suck those batteries down in less than an hour. It is not even considering the inefficiency of the inverter.

340 watts of solar panel will not keep up with the hot tub.

It sounds like you will need to purchase a lot more panels and batteries to make it all work.

I can run my hot tub on what I have. It is a 6kwatt hot tub. I have 128 280 ah LFP cells and 42 panels.

42OhmsPA · Nov 20, 2023

rob1210 said:
Hi I have 3x12v 110ah battery in parallel connecting to 2x170w solar panels a pvm controller connecting to a 3500w/7000w peak also a smart charger will be connected will this be enough to power a 2000w hottub the batteries are lead acid will the controller stop them discarging below 50% I do plan to change to mppt.thanks

Welcome to the forum.
Short answer is No. Maybe for a few minutes. At 2000w on the ac side you'll be pulling over 150a from your batteries.
You're going to need a much bigger system.

SamDeleted · Nov 20, 2023

Consider solar hot water heaters? Your system is big enough to run the pump and filter the hot tub , just not to heat it

These can be surprisingly effective, especially if you get a few

Solar Pod Swimming Pool Heater | eBay

One Solar Pod is ideal for pools up to 5,000 litres of water. • Zero heating costs. One Solar Pod is suitable for up to 5,000 litres. For larger pools simply connect several units in series. • Simple to install.

www.ebay.co.uk

Supervstech · Nov 20, 2023

rob1210 said:
Hi I have 3x12v 110ah battery in parallel connecting to 2x170w solar panels a pvm controller connecting to a 3500w/7000w peak also a smart charger will be connected will this be enough to power a 2000w hottub the batteries are lead acid will the controller stop them discarging below 50% I do plan to change to mppt.thanks

You have two questions here.

1. Will the system power the hot tub? Yes. For around 1 hour before damage is done to the batteries.

2. Will the controller stop them from being discharged? Maybe? It depends on your inverter.
Most inverters will pull down to 10V before shutting down. That is far too low and the batteries will be severely damaged.

Also, the batteries need to be recharged to full every day with a minimum of 60A...
Your pair of solar panels cannot output above 20A...

So, to do this right, you need to double everything... tripple would be better.

rob1210 · Nov 20, 2023

Thanks everyone think I've wasted a fair bit of cash lol

42OhmsPA · Nov 20, 2023

rob1210 said:
Thanks everyone think I've wasted a fair bit of cash lol

You could make use of what you have to offset other loads...

SamDeleted · Nov 20, 2023

rob1210 said:
Thanks everyone think I've wasted a fair bit of cash lol

It'd run your house lights , or fridge maybe in summer

Phone chargers , laptops ,

but that big 3.5kw inverter is going to chew through idle power , maybe more than your panels are making most of the year

rob1210 · Nov 20, 2023

If I got a smaller inverter say 2000w/4000w peak would that make any difference or will it still be the same thanks everyone

chrisski · Nov 20, 2023

SamG340 said:
Consider solar hot water heaters? Your system is big enough to run the pump and filter the hot tub , just not to heat it

These can be surprisingly effective, especially if you get a few

Solar Pod Swimming Pool Heater | eBay

One Solar Pod is ideal for pools up to 5,000 litres of water. • Zero heating costs. One Solar Pod is suitable for up to 5,000 litres. For larger pools simply connect several units in series. • Simple to install.

www.ebay.co.uk

You’ve used these? Im skeptical for heating 5000 liters.

There’s only 180 watts per meter of electricity, so probably less than 180 degrees watts of heating power. There’s 1000 watts energy total per meter square.

chrisski · Nov 20, 2023

rob1210 said:
If I got a smaller inverter say 2000w/4000w peak would that make any difference or will it still be the same thanks everyone

Insignificantly better, so actually the same.

More panels and more batteries is the only way to get this to work.

JBoffgrid2022 · Nov 20, 2023

I may be waaaaay off here but had you thought about designing a "solar hot water heater" and running these lines into your outside tub? No need to use a power hungry hot tub when the sun can heat your water free of charge without taxing your solar power needs. Just a thought

Solar Water Heaters

Solar energy isn't just for electricity. Learn how a solar water heater works.

www.energy.gov

SamDeleted · Nov 20, 2023

chrisski said:
You’ve used these? Im skeptical for heating 5000 liters.

There’s only 180 watts per meter of electricity, so probably less than 180 degrees watts of heating power. There’s 1000 watts energy total per meter square.

Not those specific ones, we made our own similar to this quick YouTube link

But yes they do work very well

There is a calculation available online there but I can't seem to find it

Something like 1m² of solar hot water panel will raise 1,000l by 1°c in 1hr ... But I do not know the correct figures

rob1210 · Nov 21, 2023

chrisski said:
Insignificantly better, so actually the same.

More panels and more batteries is the only way to get this

chrisski said:
Insignificantly better, so actually the same.

More panels and more batteries is the only way to get this to work.

If I added another 410w panel and 2 more battery I guess it still won't be enough

Nobodybusiness · Nov 21, 2023

rob1210 said:
Thanks everyone think I've wasted a fair bit of cash lol

We call it tuition..

chrisski · Nov 21, 2023

rob1210 said:
If I added another 410w panel and 2 more battery I guess it still won't be enough

If you want to find out do a power audit. Once you know kWh, run a solar calculator To determine how many panels needed. You could probably run the hot tub off a Tesla powerwall, about 13 off your batteries.

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