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Best $1500 option for 4000 watt hours of battery power? Help......I'm getting very lost in this.

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wired1

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Joined
May 30, 2021
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166
Location
New Hampshire and Bahamas
Hi Folks,

There seems to be so many solar savvy people on here, it's staggering. Lots of knowledge to comprehend. Hoping there's an easier answer than learning the whole Solar Handbook!

I mentioned earlier I already purchased a Renogy 12 volt INVERTER which I can return if there's a better solution available. I saw this at Bigbattery.com

36V A123 LIFEPO4 BATTERY for $1499​

and wonder if it's the way to go for me. I hope to someday add solar panels but for today, I just want some backup for our rolling blackouts. Should I return the 12 volt unit and go with 36 volts? I know it will be cheaper for the wire. There are no people where I am that have any clue so I'm just dizzy searching and reading and not getting very far. I want to get something setup in the next couple of weeks. Ideas? Can I pay someone online to map out a good way to go for this. I have 100's of hours researching but my brain is getting old and I'm getting lost in it all....
 
Last edited:
Amp hours x Volts = Watts hours
Watt hours / cost = cost per watt hour.
What option is the biggest bang for your buck?
Since your starting from scratch it is easier to pick a direction.
IMO I much rather go with 24v, 36v or 48v over 12v unless we are talking a very small load requirement.
4000 w / 12v = 333.3 amps 0000 gauge wire only handle 260 amps
4000 w / 24v = 166.6 amps 0 gauge wire
4000 w / 36v = 111.1 amps 2 gauge wire
4000 w / 48v = 83.3 amps 4 gauge wire
 
Last edited:
Not too many people use 36V
You may have difficulty finding 36V components.
12V
24V
48V

What's a Renogy "transformer?"
wired1 said:
Hi Folks,

There seems to be so many solar savvy people on here, it's staggering. Lots of knowledge to comprehend. Hoping there's an easier answer than learning the whole Solar Handbook!

I mentioned earlier I already purchased a Renogy 12 volt transformer which I can return if there's a better solution available. I saw this at Bigbattery.com

36V A123 LIFEPO4 BATTERY for $1499​

and wonder if it's the way to go for me. I hope to someday add solar panels but for today, I just want some backup for our rolling blackouts. Should I return the 12 volt unit and go with 36 volts? I know it will be cheaper for the wire. There are no people where I am that have any clue so I'm just dizzy searching and reading and not getting very far. I want to get something setup in the next couple of weeks. Ideas? Can I pay someone online to map out a good way to go for this. I have 100's of hours researching but my brain is getting old and I'm getting lost in it all....
Click to expand...
 
12 and 24 volts is fairly easy to find DC parts for. For 48 volts, that seems to be designed for an inverter. For example, there’s not a lot of 48 volt LED bulbs out There. For 36 volts, that’s an oddball.

I recommend you define what the power requirement is. 4000 watt hours usable is about 8 golf cart batteries. That will be plenty of power to take my RV through the night, but won’t run my air conditioner. With 8 golf cart batteries, they could be set up in 24 volt with 4S2P or all 8 inn series for 48 volts.

If you have no DC requirement, perhaps 48 volts would be better.
 
chrisski said:
12 and 24 volts is fairly easy to find DC parts for. For 48 volts, that seems to be designed for an inverter. For example, there’s not a lot of 48 volt LED bulbs out There. For 36 volts, that’s an oddball.

I recommend you define what the power requirement is. 4000 watt hours usable is about 8 golf cart batteries. That will be plenty of power to take my RV through the night, but won’t run my air conditioner. With 8 golf cart batteries, they could be set up in 24 volt with 4S2P or all 8 inn series for 48 volts.

If you have no DC requirement, perhaps 48 volts would be better.
Click to expand...
OK Thanks, then I will probably return this inverter and go with 24 volts. I am not running any DC loads. I also want to go with either AGM or Lithium batteries as they need to be shipped to me by boat and there's less legal requirements for shipping.
 
Northernchateau said:
Amp hours x Volts = Watts hours
Watt hours / cost = cost per watt hour.
What option is the biggest bang for your buck?
Since your starting from scratch it is easier to pick a direction.
IMO I much rather go with 24v, 36v or 48v over 12v unless we are talking a very small load requirement.
4000 w / 12v = 333.3 amps 0000 gauge wire only handle 260 amps
4000 w / 24v = 166.6 amps 0 gauge wire
4000 w / 36v = 111.1 amps 2 gauge wire
4000 w / 48v = 83.3 amps 4 gauge wire
Click to expand...
If I'm only going like 5 feet with 24 volts would I still need 0 gauge wire? I'll never draw near the 4000 watts at a given time unless everything starts all at once and then only for a very short time.

That being said do you think the

24V HAWK - LIFEPO4 - 170AH - 4.3KWH​

would be the best choice for batteries?
 
I'm sure there's an easy answer to this but I don't know it. After going through the inverter, how many watts are available from this,

24V HAWK - LIFEPO4 - 170AH - 4.3KWH​

at 120 volts?
 
Last edited:
wired1 said:
I'm sure there's an easy answer to this but I don't know it. After going through the inverted, how many watts are available from this,

24V HAWK - LIFEPO4 - 170AH - 4.3KWH​

at 120 volts?
Click to expand...
4300W X 80%=3440WH minus standby current 30w x 24 hours=720wh3 so 2.7 KWH
 
That’s really based off the inverter. I only see the battery size.

If you are asking what size inverter to buy, that’s a loaded question based off loads and how long you run them.
 
wired1 said:
If I'm only going like 5 feet with 24 volts would I still need 0 gauge wire? I'll never draw near the 4000 watts at a given time unless everything starts all at once and then only for a very short time.

That being said do you think the

24V HAWK - LIFEPO4 - 170AH - 4.3KWH​

would be the best choice for batteries?
Click to expand...
www.altestore.com

Wire Sizing Chart for 12V/24V/48V DC Systems - DIY Solar Resources

Information on wire sizing and a universal AWG/mm2 wire sizing chart to help in designing a 12V, 24V, or 48V DC renewable energy system.
www.altestore.com www.altestore.com

0 gauge will work for that short distance.
If you want to use 2 gauge make sure your fuse or circuit break is 130 amps max.
130 amps x 24 volts = 3,120 watts
3120 watts / 120 volts = 26 amps - some inverter usage.
How much power do you think you need?
 
chrisski said:
That’s really based off the inverter. I only see the battery size.

If you are asking what size inverter to buy, that’s a loaded question based off loads and how long you run them.
Click to expand...
I would likely be using between 300-400 watts per hour when the grid is down, just enough for my refrigeration, led lights and dc fans
 
Northernchateau said:
www.altestore.com

Wire Sizing Chart for 12V/24V/48V DC Systems - DIY Solar Resources

Information on wire sizing and a universal AWG/mm2 wire sizing chart to help in designing a 12V, 24V, or 48V DC renewable energy system.
www.altestore.com www.altestore.com

0 gauge will work for that short distance.
If you want to use 2 gauge make sure your fuse or circuit break is 130 amps max.
130 amps x 24 volts = 3,120 watts
3120 watts / 120 volts = 26 amps - some inverter usage.
How much power do you think you need?
Click to expand...
I think that's about what I need for overnight during an outage. More until bedtime when the lights and TV goes off. Next morning if it's still out I will recharge with my Honda genny.
 
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GSXR1000 said:
4300W X 80%=3440WH minus standby current 30w x 24 hours=720wh3 so 2.7 KWH
Click to expand...
Is the standby current you speak of when the inverter is running? I think I would only turn it on during and outage and have it wired only to critical loads when I'm present at the cottage. When I leave everything is off. Or is the 30 watts used by something else?
 
GSXR1000 said:
so you have a refrigerator on your inverter but don't leave it on?
Click to expand...
Sorry GSXR1000, I had written that in another post and I just realized I didn't state it here. I am tied to the grid and we have rolling blackouts and weekly outages. I'm looking for an overnight solution when the power is out for now and I want it to power a few loads that I can manually switch on. I just don't want to listen to the generator at night but really need the fans and fridge as it's in the Bahamas. Down the road when I'm there on a more regular basis I will want to add panels.
 
 
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