mr2web
New Member
Hi!
I did build a solar array on the roof of my RV last summer. This solar array including the solar charger was scaled to be able to provide for both a 12V battery system as well as for a 48V battery system. Naturally it would also fit a 24V battery system as well.
My initial plan was to run the old 12V GEL battery until it gave up or I decided that I needed more power and then choose what battery system to replace it with. Now that day have come as the old battery gave up a few weeks back. I have got a temporary replacement AGM battery whilst I make up my mind on the matter of what battery system to go for.
All pros points for a 48V system for many reasons that I might leave out as it probably have been discussed here multiple of times and it would be to kick in open door for sure. BUT there is one thought in my head that I need to have more opinions on to be able to make up my mind.
A very short backstory to understand my usecase a bit better:
I did design this solar system to be very efficient/cm2 even in very poor solar exposure. That gives that I today even can get some power of the array even from the moon at special conditions... let's not dive into that rabbit hole but I just like to explain that the array do produces energy at very low sun exposure.
I live in the middle/south-middle of Sweden and we averages 4.95 hours of sun/day. My array is build up by 3*110W Monocrystal PERC panels in series having an open circuit voltage of 23.2V per panel (69.6V@25C VOC and at lowest temperature this array would ever be exposed to 83.38V@-30C VOC). I have a Victron SmartSolar MPPT 100/20 (12-48V) solar charger. Having the array providing a higher voltage then the current 12V battery do not require much sun rays at all as I have measured a few watts produced already at around 30V coming off the array that at full exposure operates at around 68-69V. I did measure this using the Victron connect app tonight as the whole day have been overcast and it started to poor down just as the sun set clockwise. I do have graphs showing that the array did procure in tonight very poor conditions 24-ish watts averaging 52V off the array. As the voltage off the array dropped further it still produced just short of 10W at 46-ish volts as well as 5-ish watts just short of 45V... at a voltage off the array averaging 29-30V it still produced 1-2 watts. I know that we are not talking about a lot of power, but still it is power that is going into the 12V battery as is today...
If I was to go for a 48V battery system then I feel like I'm going to loose out of the low sun exposure power as the array will drop below 56V (48V) quite quick compared to a 14V (12V) or even 28V (24V) battery system. What do You think? This is what I need Your thought on.
I do not run a large inverter today but plan with the new battery system to increase the inverter to something in-between 1500W-3000W depending on battery system.... My daily need when it comes to energy consumption is about 1KWh/day. I'm calculating with quite a few different configurations, naturally providing different level of resilience to poor solar days. My largest configuration is providing me with at least 4 days of no sun before I have to alter my power usage patterns. This is another rabbit hole that we can dive into at another time as I really like to focus on the possible drawback in regard to the potential loss of the low sun exposure power with a 48V over a 12V or possible a 24V battery system. Adding a fourth 110W solar panel, in series with the other three, will unfortunately push me over the limit of 100V with the solar charger taking the VOC voltage of the whole array at lowest temperature into consideration.
So what are Your thoughts om the topic?
Thanks in advance for sharing them with me and others in this forum.
/Toby
I did build a solar array on the roof of my RV last summer. This solar array including the solar charger was scaled to be able to provide for both a 12V battery system as well as for a 48V battery system. Naturally it would also fit a 24V battery system as well.
My initial plan was to run the old 12V GEL battery until it gave up or I decided that I needed more power and then choose what battery system to replace it with. Now that day have come as the old battery gave up a few weeks back. I have got a temporary replacement AGM battery whilst I make up my mind on the matter of what battery system to go for.
All pros points for a 48V system for many reasons that I might leave out as it probably have been discussed here multiple of times and it would be to kick in open door for sure. BUT there is one thought in my head that I need to have more opinions on to be able to make up my mind.
A very short backstory to understand my usecase a bit better:
I did design this solar system to be very efficient/cm2 even in very poor solar exposure. That gives that I today even can get some power of the array even from the moon at special conditions... let's not dive into that rabbit hole but I just like to explain that the array do produces energy at very low sun exposure.
I live in the middle/south-middle of Sweden and we averages 4.95 hours of sun/day. My array is build up by 3*110W Monocrystal PERC panels in series having an open circuit voltage of 23.2V per panel (69.6V@25C VOC and at lowest temperature this array would ever be exposed to 83.38V@-30C VOC). I have a Victron SmartSolar MPPT 100/20 (12-48V) solar charger. Having the array providing a higher voltage then the current 12V battery do not require much sun rays at all as I have measured a few watts produced already at around 30V coming off the array that at full exposure operates at around 68-69V. I did measure this using the Victron connect app tonight as the whole day have been overcast and it started to poor down just as the sun set clockwise. I do have graphs showing that the array did procure in tonight very poor conditions 24-ish watts averaging 52V off the array. As the voltage off the array dropped further it still produced just short of 10W at 46-ish volts as well as 5-ish watts just short of 45V... at a voltage off the array averaging 29-30V it still produced 1-2 watts. I know that we are not talking about a lot of power, but still it is power that is going into the 12V battery as is today...
If I was to go for a 48V battery system then I feel like I'm going to loose out of the low sun exposure power as the array will drop below 56V (48V) quite quick compared to a 14V (12V) or even 28V (24V) battery system. What do You think? This is what I need Your thought on.
I do not run a large inverter today but plan with the new battery system to increase the inverter to something in-between 1500W-3000W depending on battery system.... My daily need when it comes to energy consumption is about 1KWh/day. I'm calculating with quite a few different configurations, naturally providing different level of resilience to poor solar days. My largest configuration is providing me with at least 4 days of no sun before I have to alter my power usage patterns. This is another rabbit hole that we can dive into at another time as I really like to focus on the possible drawback in regard to the potential loss of the low sun exposure power with a 48V over a 12V or possible a 24V battery system. Adding a fourth 110W solar panel, in series with the other three, will unfortunately push me over the limit of 100V with the solar charger taking the VOC voltage of the whole array at lowest temperature into consideration.
So what are Your thoughts om the topic?
Thanks in advance for sharing them with me and others in this forum.
/Toby