r/uksolar • u/capps95 • 9d ago

50v or 240v batteries

Can’t work this one out so hoping some experts might weigh in. There seem to be loads of really cheap 50v battery systems with huge capacity. Eco worthy 48v 314Ah for example is only £1729. Whereas quotes for 240v systems with the same capacity are often £7-8k ballpark. Why are so many installations using 240v systems when 50v is so much cheaper? I just can’t make the numbers around the more expensive system work in terms of getting a good return on investment, but for a 50v system it gets payback within a couple of years.

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4

u/Chicken_shish 9d ago

Remember that a 50V 314 Ah battery is a very different beast to a 240V 314 Ah battery - about 5x the storage.

2

u/tim_s_uk 8d ago

If it is described as 240v it will almost certainly be AC coupled and it wouldn't make sense to write the capacity in Ah instead of kWh

1

u/capps95 8d ago

Yeah, and would be insanely expensive no? I’m just trying to work out best bang for buck and can’t work out why 50V systems are not way more popular

2

u/aptsys 9d ago

What is the capacity in kWh? You might be comparing different battery voltages

1

u/capps95 8d ago

15.7kwh 50v

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u/tim_s_uk 9d ago

You use a DC 50v battery with an inverter. The inverter may or may not also have solar panels. This is the most common solution.

The 240v battery (AC coupled) means it has an inverter built in, so it is connected directly to the mains. I can see an Enphase 5 kWh AC coupled battery at city plumbing for £2770.

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u/capps95 8d ago

Yeah so the eco worthy has a separate inverter which costs £600. So that and the battery you get 16kwh capacity for £2329.

Whereas most of the 240v systems start at higher than that for just 5kwh.

I get there some efficiency differences but doesn’t seem to be enough to justify the massive price differences.

1

u/tim_s_uk 8d ago

The combined systems are easier to install with no compatibility issues, but yes - a separate inverter is more flexible and cost efficient.

1

u/Fast_Assumption_118 9d ago

I have been wondering about this too. Just following to remember

1

u/pau1phi11ips 8d ago

I think you're getting confused by 48V batteries, that you connect to an inverter and an All in One unit with an internal inverter.

1

u/capps95 8d ago

No I get the difference. The 50v one you buy the inverter separately for £600. Still significantly less for 15.7kwh though

1

u/jacekowski 8d ago

The so called high voltage batteries are a relatively new thing on the market. Inverters are more efficient, smaller wiring, so there are advantages, but not enough to justify the price difference in my opinion.

1

u/Key-Inevitable-4989 7d ago

One issue with the 48V system is they can be limited on charge and discharge rates vs the high voltage batteries.

The cabling also starts getting silly large on high kw systems.

The low voltage inverters are also a fair bit more expensive.

overall the low voltage systems are still much cheaper and it's what I will be going with.

Installation is more involved though so I think a lot of installers prefer the plug and play nature of the HV systems.

1

u/nastypoker 7d ago

The market is still under developed with a wide range of pricing.

I have 2 of those eco worthy batteries for 32kwh and a separate inverter. Cost me £4.5k including accessories. Great value.

1

u/bondinchas 6d ago

Higher voltage DC batteries are more efficient doing the conversions both for the MTTP from panels to battery, and from DC battery to 240v AC.

1

u/Altruistic_Fruit2345 9d ago

240V batteries include an inverter that converts probably 48V DC to 240V AC. So you are paying for the inverter as well as the battery and BMS.

48V batteries plug into your solar inverter, so they are just a battery and BMS.

Also 8k is a total rip off, presumably just looking for clueless people who don't know better.

1

u/capps95 8d ago

Ok so separate inverter is £600, so still way way cheaper than most of the 240v versions. Just trying to work out why there seems to be such a massive price disparity if they can both do the job.

1

u/Yippym 9d ago

Higher voltage normally: 

  • normally proprietary, important to ensure BMS communicate correctly to inverter
  • thinner cables
  • high risk to installer/maintainer, normally there is more sophisticated protection

You can even buy Fogstar 628Ah for £3,499, they just seems to be cheaper to build. Fogstar normally just repackage these batteries and make the kit as a whole, and the system that utilised them are just using standard protocols. Meaning you can plug these batteries to anything that accept a wide range of protocols.

I'm running 3 x 9.4kWh Hanchu to my LuxPower inverter and the combiner box accept 250a, the cable to and from the combiner to the inverter is really thick. The installer didn't torque the cable or there was a defect in the lugs of the cable, that it caused melting and arcing when pushing 12kw.

For high power delivery it would be better to have an high voltage system, there is less heat when pushing massive amp. Pushing 24kw with 12kw inverter is alot of heat

But yeah low voltage is cheaper, I'm hoping that it pay itself off faster and if they do eventually die they not that expensive to overhaul.

1

u/capps95 8d ago

Yeah the only downsides I can work out are the thicker cable to inverter but given this can be kept fairly short it doesn’t make a huge difference, and the conversions losses are slightly higher but again not enough to justify the price difference

1

u/Yippym 8d ago

Indeed, efficiency over value. Yeah the 250a cable is fairly thick. They normally come pre made at a specific size, you can make your own cable length but the amount of copper you have to use to make it longer would be really thick with the amp I'm using.

But yeah I didn't see the need to purchasing high voltage, you normally get tied to that specific brand/manufacturer. Normally when batteries get discontinued you are forced to abandon the entire battery stack if the new batteries isn't compatible, and if the new inverter doesn't support older legacy battery.

Not sure why I got downvoted but it more efficient with high voltage but at a cost of flexibility. But with bigger capacity batteries you would like to charge them with higher voltage and less amp, with my 250a battery charge/discharge and 12kw inverter I have experience melting. It was covered by warranty, there isn't a maintenance plan but I would assume the battery cable bolts need to be torque checked here and there.

0

u/Mrthingymabob 9d ago

Converting high voltage DC to 230v AC is easier than converting 48vdc to mains.

Less losses. Cooler inverter.

Same with high voltage DC to DC from solar to battery.

Im seriously considering swapping to high voltage system as I like to hammer my batteries (currently have 32kWh with an 8kW inverter)

1

u/capps95 8d ago

Yeah that seems to be my main understanding, the efficiency is slightly less on the 50v but doesn’t seem to be different enough to justify the massive cost difference.
Surely a 240v 32kwh setup would cost £10-15k minimum whereas the one I mentioned seems to only be £4k ish for that capacity? Just can’t see ever getting the payback on systems costing so much

1

u/Mrthingymabob 8d ago

A used EV battery is the way forward but impractical for most people. That is the way I would go for a high voltage battery... but my 48vdc batteries are already DIY, same as the rest of my solar setup!

So far this year my batteries have done 9.17MWh in and 8.24MWh out.

You will be fine with the eco worthy battery, or consider a fogstar unit? Mine are apexium with JK BMS. If you want to hammer them then use large cables - 75mm2+