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diy solar

voltage being throttled down ?

garyr

New Member
Joined
Nov 30, 2020
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Hello from Ohio,
I have a sprinter van conversion with 450 watt pv panels and an epever 40 amp mppt charge controller.
It has always seemed fine until now.
pv array shows 19.4 to 19.8 volts at the circuit breaker when breaker is off.
flip breaker on wired to the epever mppt 40 amp charge controller and after a minute the
incoming voltage reads 14.2 to 14.3v raising sometimes to 15.0 both at the breaker and the controller.
The lifepo4 battery bank will read 13.3 on some days never higher.
Does the charge controller throttle down the incoming voltage?
The charge controller settings are what has been accepted on here.
I am trying to understand here if I have a problem.
THis is the second year for this system. For the first year the mt50 meter would read incoming voltage
ranging upwards to over 20 volts at times but always over 15 volts even on cloudy days and the battery bank
would read up to 13.9 volts on many evenings generally settling down to 13.3 or 13. 4v overnight.
The only draw on the system lately is the mini fridge and there have been some times lately when the voltage drops low enough
to shut off the charge controller altogether. First time was frightening but if I goose it it will start up again.
I do not know if somehow the charge controller is damaged or what.
Not being an electrician I am assuming that if a good solid 19+ volts is coming into the charge controller throttling it
down to 14.2 volts that that 14.2 volts is a solid 14.2 volts if that makes sense.
BUT why is it losing 5 volts??
Any thoughts that a lay person can understand??
Thanks in advance gary
 

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BUT why is it losing 5 volts??
I assume your charge controller is changing the 19 volts at the panels to 14.2 volts to charge your batteries at the correct voltage. The current may be increasing so you may not be losing power.
 
The 19v-20v you read is "open circuit voltage". As soon as there is some electrical load on the panels, the voltage will drop according to the size of the load, the panel size/power, and the amount of sunlight. The charger tried to create a load to draw the most power from the panels and put that power to the battery, when the battery needs charged and can take that amount of power.

Try to determine if you can see on the charger the following information.
Float voltage setting
Boost voltage setting
Battery voltage (right now)
Charge current/amps (right now)

If there is sun, the charger should be trying to keep the battery at Boost voltage for a period of time (120 minutes default) and after that keep it at Float voltage. If you have good sun, if you don't have a large load, and if the battery voltage is less than float voltage, you should be seeing several amps going into the battery. If not, you have a problem.

If the battery is right at float voltage, look at the amps, then turn on some load. The amps should go up as the charger tries to hold the float voltage.

Those two tests should help you determine if you have a problem. Both tests might be okay and you still have less than ideal settings. If you turn off your load and let the battery charge up, it should charge to the boost voltage and then drop back to float. It should boost to about 14.2v to 14.4v, or somewhere in that range.
 
Consider a series connection for your panels - you'll get 40V from them, give or take.
The images show battery voltage at 14.0V, which would be either fully charged or near.
And yes, PV input voltage will be different (lower) under load/charging.

I have a Tracer 30A, 2X215W panels in series, and if there are other charge sources it will cut back the PV input voltage - I don't have a good explanation for why it does it. But if I switch off the panel breaker and back on, it comes back up to the 40V I normally see. Most of the time it runs fine, day to day, but occasionally I'll look at it and it's sitting at about half voltage - no apparent reason. I think it's just buggy software.
 
Consider a series connection for your panels - you'll get 40V from them, give or take.
The images show battery voltage at 14.0V, which would be either fully charged or near.
And yes, PV input voltage will be different (lower) under load/charging.

I have a Tracer 30A, 2X215W panels in series, and if there are other charge sources it will cut back the PV input voltage - I don't have a good explanation for why it does it. But if I switch off the panel breaker and back on, it comes back up to the 40V I normally see. Most of the time it runs fine, day to day, but occasionally I'll look at it and it's sitting at about half voltage - no apparent reason. I think it's just buggy software.
Chris, when you say "....it's sitting at about half voltage", it the PV voltage still higher than the battery and it is still charging? I see my 40A sometimes appear to drop out of MPPT mode and be more like a PWM charger, with the PV volts a little over the battery. This normally happens when there is very little sun on the array. The array voltage (open circuit) is in the MPPT range but as you suggested, the firmware doesn't seem to always handle that correctly. Mine will jump back up to MPPT when it gets more sun on the panels.
 
Chris, when you say "....it's sitting at about half voltage", it the PV voltage still higher than the battery and it is still charging? I see my 40A sometimes appear to drop out of MPPT mode and be more like a PWM charger, with the PV volts a little over the battery. This normally happens when there is very little sun on the array. The array voltage (open circuit) is in the MPPT range but as you suggested, the firmware doesn't seem to always handle that correctly. Mine will jump back up to MPPT when it gets more sun on the panels.

Yes, sounds normal, due to solar energy available.

What I get is the controller will display PV input at about half it's rating, for no apparent reason. It's like other charging inputs rendered it at a reduced input - like it throttles back the input, based on circuit voltage being higher from other charging. I just don't get it, but seems to be somewhat common with this brand of solar controller. If it becomes a real issue I would replace the controller with a Victron unit. So far it hasn't been a problem, when we're using active solar charging we're actually traveling and living in the unit. So if I see reduced voltage and charging, I'll just reset the input and that restores it back to normal.

When we're using the coach I tend to keep an eye on what the power levels are doing. It's not like a remote set it and forget it type situation with the RV.
 
Yes, sounds normal, due to solar energy available.

What I get is the controller will display PV input at about half it's rating, for no apparent reason. It's like other charging inputs rendered it at a reduced input - like it throttles back the input, based on circuit voltage being higher from other charging. I just don't get it, but seems to be somewhat common with this brand of solar controller. If it becomes a real issue I would replace the controller with a Victron unit. So far it hasn't been a problem, when we're using active solar charging we're actually traveling and living in the unit. So if I see reduced voltage and charging, I'll just reset the input and that restores it back to normal.

When we're using the coach I tend to keep an eye on what the power levels are doing. It's not like a remote set it and forget it type situation with the RV.
"other charger inputs" ? I guess I don't understand what you are saying. Can you explain?
 
"other charger inputs" ? I guess I don't understand what you are saying. Can you explain?

My system has four charging inputs:
2 solar controllers - a fixed array and a portable, both Tracer mppt
Victron Orion dc to dc charger when driving
12V converter/charger when plugged in to shorepower or generator

My hunch is when the main Tracer charge controller sees high enough battery voltage is throttles back the input voltage from the panels. Not sure why it would do that, as it properly tapers current when it charges the battery by itself - PV input voltage remains constant as long as there's solar input. I think it's a bug in the programming. At first I thought I had some kind of connection failure from the panels, but no, they remain the same. Disconnect them and reconnect and Tracer sees correct PV voltage.

Seems like a known/common problem with the Tracer charge controllers. Others have reported them charging in excess voltage from the parameters setting. And other voltage variances and drop offs.
 
My Bad....The system acted exactly as I described and every night
the voltage would drop really low and turn off the charge controller
BUT I was studying the battery yesterday AND I only had 2 of the 4 cells
actually hooked up. Had to bring those low voltage cells up to equal
voltage before reattaching the whole thing.
I have:
16 3.2v lifepo4 50 ah cells tying 4 together to make 4 13.2v 50ah batteries
HELP PLEASE
I have been looking at all the charts on how to wire these things and the harder I
try the less I understand. My thought is that electricity should flow like water
through a water hose but I have not been able to configure this setup where it seems right.
Would one of you be kind enough to tell me how to wire these cells properly?
The individual cells came with a harness that keeps them roughly 1/4" apart. I have
read where you should compress/sandwich the cells together with non conducive
separators but this battery is 2 years old with no noticeable loss of juice to date and no deformation
of the cases.
Anyway would someone please show me the optimal wiring configuration.... representation
attached.
Thanks to all of you
Gary
 

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If the mppt input voltage is dropping to 14V, the panel isn't putting out properly.
Check the panel for bird droppings or something blocking it.
 
The panels are putting out 19.8 volts
then a roughly 10 foot run to the circuit breaker
which has 19+ volts before the tripped breaker.
Engage the breaker which attaches to the cc and
voltage drops to 14.2 +or-
 

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Right.
So under load, your panels are dropping below vmp voltage.
Either the mppt has failed and is shunting the panel voltage to the batteries, or the panels are shaded or defective.
 
The panels are putting out 19.8 volts
then a roughly 10 foot run to the circuit breaker
which has 19+ volts before the tripped breaker.
Engage the breaker which attaches to the cc and
voltage drops to 14.2 +or-
If your panels are in full sun with that low of amps, yes something is wrong. 450w at 20v, you must have panels in parallel. Can you easily disconnect some and see what happens? Maybe connect one at a time until you find something that looks odd, looking at both volts and amps.
 
Hello from Ohio,
I have a sprinter van conversion with 450 watt pv panels and an epever 40 amp mppt charge controller.
It has always seemed fine until now.
pv array shows 19.4 to 19.8 volts at the circuit breaker when breaker is off.
flip breaker on wired to the epever mppt 40 amp charge controller and after a minute the
incoming voltage reads 14.2 to 14.3v raising sometimes to 15.0 both at the breaker and the controller.
The lifepo4 battery bank will read 13.3 on some days never higher.
Does the charge controller throttle down the incoming voltage?
The charge controller settings are what has been accepted on here.
I am trying to understand here if I have a problem.
THis is the second year for this system. For the first year the mt50 meter would read incoming voltage
ranging upwards to over 20 volts at times but always over 15 volts even on cloudy days and the battery bank
would read up to 13.9 volts on many evenings generally settling down to 13.3 or 13. 4v overnight.
The only draw on the system lately is the mini fridge and there have been some times lately when the voltage drops low enough
to shut off the charge controller altogether. First time was frightening but if I goose it it will start up again.
I do not know if somehow the charge controller is damaged or what.
Not being an electrician I am assuming that if a good solid 19+ volts is coming into the charge controller throttling it
down to 14.2 volts that that 14.2 volts is a solid 14.2 volts if that makes sense.
BUT why is it losing 5 volts??
Any thoughts that a lay person can understand??
Thanks in advance gary
Hi GaryR

If you connected your paneks directly to your flat battery, the panel would be pulled down to the battery voltage. The power output of a solar panel is very sensitive to this and at such a low voltage it would provide very little power to charge the battery.

So then what is happening??? The charger....mppt or pwm essentially gathers the energy from the panel at its best most powerful voltage position. This power is stored and then released to the battery as soon as it is sufficient to do so AND maintain the best panel voltage position. The voltage to the battery is also accordingly controlled to the optimum charging value.....the amps supplied however change according to what the panel can give. Hope this helps
 
What are you using for panel connectors?
My cheap MC4 had contact pins would not stay locked in place. Epoxy fixed it.
SAE are terrible. The barrel side has a split that might need an occasional squeeze. Use a contact cleaner/dressing.
Also check for worn/stretched wires near the connectors. Too much bending and not enough strain relief.
 
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