With 24v charging on a 24v battery is everything the same as 12s except half the amps? Same charging profile, SOC vs time etc? Is 8.3 amps with 24v the same exactly as 16.6 amps on a 12v bank of the same AH capacity? (Do you express the "AH" as half too?--Please, no Watts here! :) )If so it would be easy to compare results. With my 230w panel and MPPT I was getting 15.5a in the Spring and 13.5a in the Summer. With PWM I would get 14.5a all the time based on my 130w having 8.2 Isc. (which I got all the time no matter Spring or Summer)The Isc of the 230w panel is 8.3 and in the Summer I often saw 8.4 or so. (Isc goes up with heat) Since I get Isc with a 12v panel I should get Isc with the 24v? I notice that the 230w and the 130w have about the same Isc, so it is not twice really. Confusing. Panel brands do vary in Isc per Watt though.I would sure take the 16.6 worth at 12 getting 8.3a on 24v instead of 13.5 on 12 if that is how it works.

Watts makes it easy to compare systems. Yes, 24v charging is half the amps.

Half the amps and exactly twice the voltage.I am curious if Vmp of 30 will be enough in hot conditions.

2oldman wrote:Watts makes it easy to compare systems. Yes, 24v charging is half the amps.So when panel temps get high and the voltage and power drops but the Isc goes up, do you think you are missing a trick by using an MPPT at 24v instead of PWM and Isc at 24v on your 24v bank?Ever measured either way?Of course it means nothing when the MPPT controller goes PWM. We are talking about the buck converter here actually, which is always in place except in "PWM controllers" that don't have one.So a buck converter type controller is vulnerable to a hot panel, but a PWM controller could care less about panel heat. It just keeps getting Isc no matter what.

smkettner wrote:Half the amps and exactly twice the voltage.I am curious if Vmp of 30 will be enough in hot conditions.Define "hot" I have been puzzled by my results at 25C ambient (not that hot at 77F) resulting in panel temp of 51C (10% loss of power from 25C panel rating STC according to the graphs on that)So we have two votes that if I see 8.3a going into a bank of two 12s in series (24v) that is the exact same (just as good) as seeing 16.6a going into the same two 12s in parallel (12v) Right?

BFL13 wrote:So when panel temps get high and the voltage and power drops but the Isc goes up, do you think you are missing a trick by using an MPPT at 24v instead of PWM and Isc at 24v on your 24v bank?I don't pay a lot of attention to MPPT vs PWM, hence I don't know enough to understand what you're asking.At 835w of solar I guess it doesn't make a whole lot of difference.

Is 24v Charging the Same as 12v Charging? | Good Sam Community

24 Replies

BFL13
Explorer II
Feb 06, 2015
smkettner wrote:
Half the amps and exactly twice the voltage.

I am curious if Vmp of 30 will be enough in hot conditions.

Define "hot" I have been puzzled by my results at 25C ambient (not that hot at 77F) resulting in panel temp of 51C (10% loss of power from 25C panel rating STC according to the graphs on that)

So we have two votes that if I see 8.3a going into a bank of two 12s in series (24v) that is the exact same (just as good) as seeing 16.6a going into the same two 12s in parallel (12v) Right?
BFL13
Explorer II
Feb 06, 2015
2oldman wrote:
Watts makes it easy to compare systems. Yes, 24v charging is half the amps.

So when panel temps get high and the voltage and power drops but the Isc goes up, do you think you are missing a trick by using an MPPT at 24v instead of PWM and Isc at 24v on your 24v bank?

Ever measured either way?

Of course it means nothing when the MPPT controller goes PWM. We are talking about the buck converter here actually, which is always in place except in "PWM controllers" that don't have one.

So a buck converter type controller is vulnerable to a hot panel, but a PWM controller could care less about panel heat. It just keeps getting Isc no matter what.
time2roll
Nomad
Feb 06, 2015
Half the amps and exactly twice the voltage.

I am curious if Vmp of 30 will be enough in hot conditions.
2oldman
Explorer II
Feb 06, 2015
Watts makes it easy to compare systems. Yes, 24v charging is half the amps.

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Is 24v Charging the Same as 12v Charging?

24 Replies

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