4@12v = 24v

BFL13 wrote:
Also I am not sure you are better off with 24v batts and a 24v panel than you were with a 12v batt and a 12v panel.

About the same in most cases.

I can't figure out this 24v battery with MPPT or PWM. Also I am not sure you are better off with 24v batts and a 24v panel than you were with a 12v batt and a 12v panel.

The MPPT with a 24v on a 12 has all that voltage diff but that goes away with 24 on 24v?

Anyway--it seems the OP with four 12s as a 24 in S/P would not do better if he had them in series for 48 and had a 48v inverter, if I follow that and from what PT says.

pianotuna wrote:
Would not a 60 amp charge controller make that "limit" for 12 volt more nearly 720 watts?

That's how I understand it.

I think the mfrs assume with larger arrays you are not running a 12v system.

BFL13 wrote:
Would an MPPT still be able to do its thing on a 24 to get more amps?

Mine does.

BFL13 wrote:
Would an MPPT still be able to do its thing on a 24 to get more amps?

You would still get the power point tracking so you would still get the boost. I was just looking at it from a cost perspective.

EDIT: The Morningstar Tristar PWM can accept 125V input, 4kW arrays, 45 or 60A output, 12-48V banks. The 45A controller only costs $146.

Not sure about the PWM controller as mena mentioned. On a 230w panel with 8.3a Isc you would get almost twice the amps with MPPT feeding a 12v battery, but with PWM your max is still the 8.3a whether on a 12 or 24v battery ???

But on a 24v battery, that 8.3a is as good as 16.6 on a 12v battery (?) but you don't have MPPT. You are still limited to the same Voc intake of the controller too (not sure that matters)

Would an MPPT still be able to do its thing on a 24 to get more amps?

2oldman wrote:
In my case, both played a role.

Thanks.

Hi BFL13,

It is not quite a wash. The 48 volts means 1/2 the chemical reaction speed compared to 24 volts. The speedier the reaction the more internal resistance matters. However, since 2oldman is going AGM, where the internal resistance is already pretty low, the advantage of 48 volts is fairly small from a battery point of view.

From an inverter point of view 48 volts wins hands down.

From a wire size point of view 48 volts wins hands down.

From a voltage drop point of view 48 volts wins hands down.

From a solar charging wattage point of view 48 volts wins hands down. (The new Rogue 3048 could look after 1440 watts @ 48 volts).

BFL13 wrote:
24v

I have lost it. Your microwave wants 1500w from the inverter. 48v means half the amps so that is easier on the batteries but you also need twice the batteries so that is even fewer amps per batt?

But the 48v four 12s in series has half the AH as the 24v four in S/P so isn't that a wash? Can't be right. I bet this is to do with those nasty watts things again :(

BFL13 wrote:
I bet this is to do with those nasty watts things again :(

Yes, the watts thing. :) Amp hours is still the important measure here so go with that. IMO, the benefit of high volts is skinny wires (and access to larger inverters) and the use of cheap PWM controllers on 24V solar panels.

A 150Ah, 48V battery bank has the same storage capacity as a 12V, 600Ah bank (using the T1275's as an example). Watts.

24v
A. two 12s in series (1275) 150AH 164 lbs
B. three 8s in series (890) 190AH 207 lbs
C. four 6s in series (105) 225AH 248 lbs
D. four 12s in S/P (1275) 300AH 328 lbs

48v
A. four 12s in series (1275) 150AH 328 lbs
B. six 8s in series (890) 190AH 414 lbs
C. eight 6s in series (105) 225AH 496 lbs

I have lost it. Your microwave wants 1500w from the inverter. 48v means half the amps so that is easier on the batteries but you also need twice the batteries so that is even fewer amps per batt?

But the 48v four 12s in series has half the AH as the 24v four in S/P so isn't that a wash? Can't be right. I bet this is to do with those nasty watts things again :(

http://www.batterysales.com/downloads/TrojanSpecs.pdf

Hi,

Would not a 60 amp charge controller make that "limit" for 12 volt more nearly 720 watts?

Salvo wrote:
Charge controllers are current limited. A 12V battery system may limit solar to 300W. The same controller in a 24V system is limited to 600W, while a 36V system is limited to 900W.

Sal