Batteries
- Thread starter Revid
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You might get more total amp hour by wiring in parallel but you need to understand that the total wattage stays the same.
1 - 125ah 12vDC battery has ~1500wh
2 - 125ah 12vDC batteries gives you a 250ah 12vDC battery. or double to 3000wh
Wired in series 2-125ah 12vDC batteries gives you a 24vDC 125ah battery, also 3000wh
1 - 125ah 12vDC battery has ~1500wh
2 - 125ah 12vDC batteries gives you a 250ah 12vDC battery. or double to 3000wh
Wired in series 2-125ah 12vDC batteries gives you a 24vDC 125ah battery, also 3000wh
DIYrich
Solar Wizard
Depends upon what you intend to do with the power. Power native 12v or 24v devices? Invert to 120v AC? How much load?
Bob B
Emperor Of Solar
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One way you have a 12V pack .... the other way a 24V pack ..... as others indicated the power you get will remain the same.
wpns
Solar Joules are catch and release
Higher voltage is better because lower losses in the interconnects and other wiring, but as DIYrich pointed out it depends on your load.
It’s a small cabin, fridge, tv, cell booster and led lights. Just wondering cause I switched from 12 v to 24 v and it seems like I loss ahs when I went to 24v. At 12v I had 6 batteries in parallel but now at 24 I have three sets of 24,total ah at 375!!
Bob B
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AH at 24V is going to be 1/2 the AH for the same amount of power. AH is only a fair comparison if comparing the same voltage.
hwy17
Anti-Solar Enthusiast
Don't put 12v lithium batteries in series.
Bob B
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The same amount of power .... the power from the batteries is what you want to know .... AH is irrelevant with 2 different voltages.
Maybe more power at 24V because there will be 1/2 the amount of current and therefore less loss.
Yes power to 3000 w inverter
WH? Wattage hrs? When I switched to 24v I was told it was better for wiring and on the overall setup. So before I had the same 6 batteries in parallel I would have 750 ah. Now on 24 I have 375 hr. It seems to me I lost half of my usable power!
No... as @Mattb4 explained. Ah is not power, it is a measurement of capacity at a given voltage.
Power is Amps x Volts. Energy is Power x time.
What is most important to you powering your devices via the inverter is total energy available from your batteries. That is measure in Wh (Watt-hours), often with larger values expressed with the prefix 'k' for kilo = 1000.
750Ah @ 12V is identical to 375Ah @24V in terms of stored energy.
Regarding...
...looked at in very basic terms, there is no difference in the energy you get from having 6 in series or 2s3p in 24V.
However, in practice, there will be losses due the resistance on your DC wires from batteries to inverter and those losses are inversely proportional to the square of the voltage. So when running heavy loads at 24V you will have less losses than the same loads at 12V.
Hence, overall, you should be better off running at 24V rather than 12V.
Thanks that’s very well explained! So like you said Wh is what Iam looking for in terms of comparing systems.
Assuming you mean "2 x 12v 300 ah in series with each other and in parallel with the other three 24V pairs"...
I'll let others confirm that, as I'm not experienced with lead-acid systems, but I can't think of any reasons, electronically, why that wouldn't work.
The higher your voltage the lower the amperage needed to transmit the same amount of power. So at 120w load at 24v uses 5 amps. At 12v it uses 10a.
24vDC advantage over 12vDC means that smaller wire and components can be used.
Rednecktek
Solar Wizard
Or in the water analogy world, which is better, a pair of 5 gallon buckets OR a 10 gallon bucket. Same capacity, different form.
The big advantage of 24v over 12v is in your wire and SCC sizes. For rough napkin math a 3000w inverter ÷ 12v = 250a of current which needs 3/0 honkin welding cable to connect. However, 3000w ÷ 24v = 125a which is only 4awg or so. Much smaller wire, much smaller fuse, easier to handle for crimping and fishing.
The other place the 24v is better is your charge controller. Since charge controllers are rated by OUTPUT amps, a 40a SCC can do 40a × 15v = 600w of panels, but the same controller at 24v does 40a × 30v = 1200w of solar on the same unit.
When you're looking at amp hour ratings, that's how many hours you can draw 1 amp, but what's important is watts (amps × volts = watts × hours = watt-hours) and that's your loads. So, say you want to run your MargaritaMaster 3000 for a party (that you'd better invite us to!) and it needs 240 watts to run. On a 12v system that would be 240w ÷ 12v = 20a. So, if you made margaritas for an hour that would be 20 amp-hours. Now, say you had a 24v system and made margaritas. Now it's 240w ÷ 24v = 10a, or 10 amp-hours for an hour of margarita making. Either way, you're still using 240 watt-hours. And by now you're probably a bit tipsy.
Does that help make sense?
About the only place amp-hours comes into play is when you're going from lead acid flavors to lithium. In general a lead acid battery can only be drained to 50% of it's rating before you start hurting it, so when you look at that cheap WallyWorld 100ah battery, you can only really USE about 50ah of it, which meand if you replaced it with a 50ah lithium you'd get the same Usable Energy out of it. With the cost of lithium coming down and the fact that you need twice as many amp-hours of lead to get the same usable watts, lithium is pretty much the answer outside of specific use cases like long periods of sub-freezing temps.
The big advantage of 24v over 12v is in your wire and SCC sizes. For rough napkin math a 3000w inverter ÷ 12v = 250a of current which needs 3/0 honkin welding cable to connect. However, 3000w ÷ 24v = 125a which is only 4awg or so. Much smaller wire, much smaller fuse, easier to handle for crimping and fishing.
The other place the 24v is better is your charge controller. Since charge controllers are rated by OUTPUT amps, a 40a SCC can do 40a × 15v = 600w of panels, but the same controller at 24v does 40a × 30v = 1200w of solar on the same unit.
When you're looking at amp hour ratings, that's how many hours you can draw 1 amp, but what's important is watts (amps × volts = watts × hours = watt-hours) and that's your loads. So, say you want to run your MargaritaMaster 3000 for a party (that you'd better invite us to!) and it needs 240 watts to run. On a 12v system that would be 240w ÷ 12v = 20a. So, if you made margaritas for an hour that would be 20 amp-hours. Now, say you had a 24v system and made margaritas. Now it's 240w ÷ 24v = 10a, or 10 amp-hours for an hour of margarita making. Either way, you're still using 240 watt-hours. And by now you're probably a bit tipsy.
Does that help make sense?
About the only place amp-hours comes into play is when you're going from lead acid flavors to lithium. In general a lead acid battery can only be drained to 50% of it's rating before you start hurting it, so when you look at that cheap WallyWorld 100ah battery, you can only really USE about 50ah of it, which meand if you replaced it with a 50ah lithium you'd get the same Usable Energy out of it. With the cost of lithium coming down and the fact that you need twice as many amp-hours of lead to get the same usable watts, lithium is pretty much the answer outside of specific use cases like long periods of sub-freezing temps.
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