I wish someone would review my temporary solution design while I wait for my Panasonic Panels to arrive so I can do it correctly...

GEBIII

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I would appreciate anyone poking holes in the attached design while I wait for the correct panels to arrive that have been delayed... I have all of the components except for those so this is a make do... My training and experience says it will work fine, but I always like to have other eyes look for things I may have missed...
 

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rmaddy

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To make it a lot easier for people to review this you need to post the specs for everything in that diagram. For the two types of panels you should post the Vmpp, Voc, Isc, and Impp. For the solar charge controllers you need to post the max input voltage and the max output amps.

You should also show what size wire you plan to use everywhere.
 

rmaddy

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Once you post all of those details people can verify a lot more but one glaring problem I see is that you have 4 batteries in series for a 48V system (that's fine) but then you plan to separately charge two batteries per SCC. That's not going to end well.

You need to treat the 4 batteries like it's one unit with a single pos and neg connection. Those four batteries must always be at the same voltage and SOC (state of charge).

Add a negative bus bar to one end of the battery string and add a positive bus bar to the other end of the battery string. Now connect both charge controllers and the inverter to those bus bars. Nothing should ever be connected into the middle of the battery string with the small exception of a possible midpoint voltage monitor and/or battery balancer.
 

Pappion

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Your beakers are too high current. Should be about 1.25x to 1.5x the expected current. Are you using HV DC solar breakers, and 48v breakers and switches?
Agreed, Your split charge arrangement will go out of balance. Also your upper pair would have 25v on the ground.
"You need to treat the 4 batteries like it's one unit with a single pos and neg connection."
37.5 volts from panels will not charge 48v battery. 4 in series is 72v and 75v, should be good enough. Higer voltage will save on wire size and duplicate runs.
Maybe you should make it a 24v system. EPEVER 2210AN are 12/24v controllers, can be paralleled. Amperetime claims series-parallel of 4 batteries OK. 4K watts inverter easily supported by 24v.
 
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GEBIII

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Your comment with regard to the 24 volt split charge of the 48 volt system is exactly what I was worried about. I am scratching my head trying to figure out how they could interact improperly. Please advise what you mean when you say it will not end well? The plan is to have identical charge voltage and current out of each controller. All of the components are brand new.

The panels are connected with 12awg wire. All of the battery connections will be very short (less than 12") lengths of 6awg. The controllers are 100v max at 20a. The panels already show the working voltage and current, just not the open circuit voltage and short circuit current. I will update the drawing as you suggest.

The final system will only use a single 150v 40a mppt charge controller for the full 48 volt array. That charge controller will be fed by four identical Panasonic 320w panels with 70 volt oc outputs and the full 20 amps recommended for the LifePO4 batteries.
 

jwelter99

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Your comment with regard to the 24 volt split charge of the 48 volt system is exactly what I was worried about. I am scratching my head trying to figure out how they could interact improperly. Please advise what you mean when you say it will not end well? The plan is to have identical charge voltage and current out of each controller. All of the components are brand new.

The panels are connected with 12awg wire. All of the battery connections will be very short (less than 12") lengths of 6awg. The controllers are 100v max at 20a. The panels already show the working voltage and current, just not the open circuit voltage and short circuit current. I will update the drawing as you suggest.

The final system will only use a single 150v 40a mppt charge controller for the full 48 volt array. That charge controller will be fed by four identical Panasonic 320w panels with 70 volt oc outputs and the full 20 amps recommended for the LifePO4 batteries.

Each 24V "side" of the battery will see different charging profiles due to the different MPPT's and PV arrays which will bring the two sides out of balance.

Even with 4 series 12V batteries to form a single 48V pack with 48V charging you will see some imbalance over time due to different battery performance and some interconnect variances.

You really need a 48V output capable MPPT to get this up and going in a correct way.
 

GEBIII

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The controllers in the drawing are also only 12/24volts that I use on my 12 volt system. I have one 48volt mppt controller and one 48volt pwm controller but I did not want to mix the two types?

I really appreciate the input, sorry for the lack of information...
 

jwelter99

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The controllers in the drawing are also only 12/24volts that I use on my 12 volt system. I have one 48volt mppt controller and one 48volt pwm controller but I did not want to mix the two types?

I really appreciate the input, sorry for the lack of information...

I can't comment on mixing the two types, but many run multiple MPPT's charging the same complete battery pack so I would assume the two can co-exist.

Are the ratings on the MPPT and PWM 48V units high enough for the input side?
 

Pappion

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PWM just switch on and off very rapidly, stay on for max charge. This can smoke. Saving grace is the panels source resistance and low voltage overhead, 17v-18v panel charging at 12v - 14v battery. I would not want to scale this up.
 

GEBIII

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The 48 volt MPPT charge controller has 150 volt max input voltage and the 48 volt PWM charge controller has a max input voltage of 100 volts. I read that there would be a potential conflict with using the two different types charge controllers on the same battery bank.

It looks like my best bet is to just wait on the Panasonic panels to arrive and do it right the first time...;) The only other solution seems to be to acquire another 48 volt MPPT controller. My pile of unused equipment is growing...
 

GEBIII

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Your beakers are too high current. Should be about 1.25x to 1.5x the expected current. Are you using HV DC solar breakers, and 48v breakers and switches?
Agreed, Your split charge arrangement will go out of balance. Also your upper pair would have 25v on the ground.
"You need to treat the 4 batteries like it's one unit with a single pos and neg connection."
37.5 volts from panels will not charge 48v battery. 4 in series is 72v and 75v, should be good enough. Higer voltage will save on wire size and duplicate runs.
Maybe you should make it a 24v system. EPEVER 2210AN are 12/24v controllers, can be paralleled. Amperetime claims series-parallel of 4 batteries OK. 4K watts inverter easily supported by 24v.
Ah so the worst culprit would be the negative ground from the charge controller in the middle of the battery bank. That makes sense. Are these inverters capable of being rewired internally to operate at 24 volts?
 

Pappion

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Victron Smart Charge Controllers communicate with each other and coordinate charging.
Other pairs will work, but it's not optimized. Maybe one is late to startup up due to the sun, and sees a reasonable level, and only floats. Less of an issue LiFePO4 which has a simpler charge profile.
 

rmaddy

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Your comment with regard to the 24 volt split charge of the 48 volt system is exactly what I was worried about. I am scratching my head trying to figure out how they could interact improperly. Please advise what you mean when you say it will not end well?
You have a 48V battery bank. You need 48V capable charge controllers and a 48V inverter. You can't use two 24V charge controllers each charging half of the battery bank. Each pair of batteries will get charged at very different rates and go terribly out of balance. Over time some batteries will be overcharged and some will be undercharged as the inverter tries to draw power from the whole string.

The plan is to have identical charge voltage and current out of each controller.
You can't get identical charge voltage and current. Each controller is connected to a separate set of panels. Even if all of the panels were identical you can't assume the output of each controller will be identical. One panel might be dirtier than others, for example. Or one panel gets different shading, etc.

The controllers are 100v max at 20a. The panels already show the working voltage and current, just not the open circuit voltage and short circuit current.
Voc is what matters when it comes to the max input voltage of the controller.

The final system will only use a single 150v 40a mppt charge controller for the full 48 volt array. That charge controller will be fed by four identical Panasonic 320w panels with 70 volt oc outputs and the full 20 amps recommended for the LifePO4 batteries.
Then what is the system in the diagram you posted? The final system sounds much better than the diagram you posted.
 

jwelter99

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The 48 volt MPPT charge controller has 150 volt max input voltage and the 48 volt PWM charge controller has a max input voltage of 100 volts. I read that there would be a potential conflict with using the two different types charge controllers on the same battery bank.

It looks like my best bet is to just wait on the Panasonic panels to arrive and do it right the first time...;) The only other solution seems to be to acquire another 48 volt MPPT controller. My pile of unused equipment is growing...

Or go live with the 48V MPPT you have and the existing PV array sized to not overload it.
 

GEBIII

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You have a 48V battery bank. You need 48V capable charge controllers and a 48V inverter. You can't use two 24V charge controllers each charging half of the battery bank. Each pair of batteries will get charged at very different rates and go terribly out of balance. Over time some batteries will be overcharged and some will be undercharged as the inverter tries to draw power from the whole string.


You can't get identical charge voltage and current. Each controller is connected to a separate set of panels. Even if all of the panels were identical you can't assume the output of each controller will be identical. One panel might be dirtier than others, for example. Or one panel gets different shading, etc.


Voc is what matters when it comes to the max input voltage of the controller.


Then what is the system in the diagram you posted? The final system sounds much better than the diagram you posted.
Oh I totally agree, the system in the diagram was my idea for a "make do" alternative until the correct panels arrived. I appreciate all of your comments about why it will not work. All of my experience thus far has been with 12 volt systems with separate panel arrays and charge controllers that are all matched. Since the LifePo4 batteries have become more reasonable I decided to step out...
 

GEBIII

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Aug 1, 2021
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Your beakers are too high current. Should be about 1.25x to 1.5x the expected current. Are you using HV DC solar breakers, and 48v breakers and switches?
Agreed, Your split charge arrangement will go out of balance. Also your upper pair would have 25v on the ground.
"You need to treat the 4 batteries like it's one unit with a single pos and neg connection."
37.5 volts from panels will not charge 48v battery. 4 in series is 72v and 75v, should be good enough. Higer voltage will save on wire size and duplicate runs.
Maybe you should make it a 24v system. EPEVER 2210AN are 12/24v controllers, can be paralleled. Amperetime claims series-parallel of 4 batteries OK. 4K watts inverter easily supported by 24v.
I was hesitant to connect the two different banks of 100 watt panels in series-parallel together because I had read they would interact strangely unless they were separated by using two charge controllers. Do you think these panels are close enough to combine in two series/parallel strings?
The RNG are 22.3 Voc, 18.6 Vmp, 5.38 Imp, 5.86 Isc. The EBS are 22.24 Voc, 18.0 Vmp, 5.56 Imp, 5.90 Isc. Thanks for your input.
 

GEBIII

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Or go live with the 48V MPPT you have and the existing PV array sized to not overload it.
I will then ask you the same question I just posted...
I was hesitant to connect the two different banks of 100 watt panels in series-parallel together because I had read they would interact strangely unless they were separated by using two charge controllers. Do you think these panels are close enough to combine in two series/parallel strings?
The RNG are 22.3 Voc, 18.6 Vmp, 5.38 Imp, 5.86 Isc. The EBS are 22.24 Voc, 18.0 Vmp, 5.56 Imp, 5.90 Isc. Thanks for your input.
 

GEBIII

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Much thanks for everyone's help, guidance and assistance. I just ordered another 48 volt MPPT Charge controller (150 volt and 40 amps) to match the one I have. It is the safest solution even on a temporary basis and gives me the option to add or change panels going forward. Have a Great Day!
 
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