Help with off grid system for hifi

[Martin-Andersen]

Hi Solar geeks! This is a little different. I want to build an off grid system but without the solar part

For some of you this might sound crazy. But a hifi system sounds better running on batteries, that's the best. The next best thing is to run it with AC created from batteries and that’s what I want to do.

So I need a charger, batteries and a converter. But there are so many options so I need help with choosing the right components for the task.

I lent a Goal Zero Yeti 3000 and when I was playing my hifi system was using:

• 277 Watts
• 23 Amps

I would like to be able to play for at least 2 hours and as I understand it, the battery should not be drained more than 60% so there are 40% left.

I want the pure sin converter to have very low THD. Voltages and frequency should also be very accurate.

I should be able to move the system and it should run on 230v 50Hz and be VERY quiet.
I am not going to move it around. But I should be able to take it with me, so all in one box.

Questions:

• 12 or 24V?
• Can a battery charger be programmed to start charging at ie. 40%?
• How often do I need to Top/Bottom balance? If I never discharge below 40%

Charger? I haven't found one

Was thinking about using this cells:
https://www.aliexpress.com/item/400...99107d1c009f81b1-1586697671423-06460-pixtzdnE

This BMS:

12.64US $ 22% OFF|Daly 3.2v Lifepo4 8s 24v 15a 30a 60a 100a 200a 500a 18650 Lfp Pcm Battery Protection Board Bms With Balanced Lithium Battery - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Pure Sine Wave Converter
https://www.aliexpress.com/item/33000537707.html

I know this is a lot to ask. If you have any tips or ideas for this system, please let me know.

 

[JoeHam]

Well it’s not so crazy as I have been doing just that for an off grid amateur radio station for years. My needs are more power intensive as I receive and transmit. Sometimes using a 500w amplifier that consumes about 1 Kw when transmitting.

I simply used an ebay 48v 20 Ah scooter battery and a 3Kw reliable inverter. You could get by with the 1500w version. The scooter LiFePO4 batteries generally come with a charger. So I just charged up from the grid at home before I went in the field.

After years of this I added solar charging.

I will find some ebay links and add them for you below.

 

[JoeHam]

See here:

Pure Sine Wave Inverter 1500W 48V DC to 120V AC Powe Inverter Off Grid Solar 651519884645 | eBay

Full power rated power and double the surge power. 1500W rated power, 3000w surge power for a few miliseconds. Big and clear MCU LED Display for DC Volt and AC Volt output to moniter the actual working status.

www.ebay.com

And here:

48V 20Ah 51.2v Lithium Battery Pack for EbikeScooter 1000Watt 3.2v LiFePO4 cell | eBay

Find many great new & used options and get the best deals for 48V 20Ah 51.2v Lithium Battery Pack for EbikeScooter 1000Watt 3.2v LiFePO4 cell at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[JoeHam]

IF you proceed this way be certain to add a proper fuse/breaker and a precharge capacitor.

There are threads on the forum which explain each of these topics.

 

[Supervstech]

I understand your desire, but using solar COMPLETELY keeps everything DC. Chargers produce DC in pulses... so when charging, you are getting noise... keeping it solar charged really makes the entire setup
I don’t know of a way to automate the charger, maybe feed into a charge controller with parameters set for when to allow watts in below 40%...?

 

[Martin-Andersen]

I understand your desire, but using solar COMPLETELY keeps everything DC. Chargers produce DC in pulses... so when charging, you are getting noise... keeping it solar charged really makes the entire setup
I don’t know of a way to automate the charger, maybe feed into a charge controller with parameters set for when to allow watts in below 40%...?

I live in Denmark and in a flat, so not much sun and no place to put the solar panels

 

[Martin-Andersen]

Well it’s not so crazy as I have been doing just that for an off grid amateur radio station for years. My needs are more power intensive as I receive and transmit. Sometimes using a 500w amplifier that consumes about 1 Kw when transmitting.

I simply used an ebay 48v 20 Ah scooter battery and a 3Kw reliable inverter. You could get by with the 1500w version. The scooter LiFePO4 batteries generally come with a charger. So I just charged up from the grid at home before I went in the field.

After years of this I added solar charging.

I will find some ebay links and add them for you below.

That's a brilliant idea Can you help me calculate for how long I can play on my system before a recharge?

 

[JoeHam]

Well 48v times 20 amp hours is 960 watt hours.

IF you had zero losses AND could use 100% DOD (both not possible) you would have 3.47 hours of play time right?

Me? I would give it a try and just add a second battery if needed.

 

[JoeHam]

Remember, this is all free advice and worth at least twice that.

YMMV, proceed at your own risk, normal disclaimers apply ?