Lensun Panel Voltage Too Low for MPPT and LiFePO4?

[FrugalNomad]

Hello DIY Solar Forum,

This is my first post to the forum. I am putting together my first "system", but just the start of one, that hopefully will expand as my vehicle changes over time. I have searched for this minimum voltage for MPPT, and found some posts that make it sound like I need at least 17 volts to use MPPT to Lithium. Is that 17 volts Open circuit, or Max Power voltage?

Currently traveling in a Prius, and want to power a small 12VDC compressor fridge, and maybe some other devices from time to time. So, after mulling over the options, I decided to err on the side of safety, and ordered a Battle-Born 12V 100ah. My water jugs never freeze, so I doubt I will have a cold charging problem.

I found a Lensun 110watt 18V flexible ETFE on amazon that is the perfect size for mounting on the back hatch glass. The only problem is it said 18V on amazon, but 16V on the panel label:

Amazon Electrical Information:
Peak Power: 110W
Solar cell efficiency 23%
Maximum power voltage: 18v
Maximum power current: 6.11A
Open Circuit voltage: 21.24V
Short Circuit current: 6.72A
Power allowance range: +/- 3%
Maximum system voltage: 500V

Panel Label:
Model LS-110FX2-SUN
Pm: 110W
Vpm: 16V
Imp: 6.88
Voc: 18.88
Isc: 7.56A
Max System Voltage: 500V
Test Condition: AM=1.5, E=1000W/m Tc=25 Deg.C

This must be a different panel. On a grey overcast afternoon in SC, it measured 17.14VDC open circuit. I don't yet have a charge controller, but was hoping to go MPPT, and allow for adding another smaller panel in parallel, possibly in the future. But I'm thinking this will not work for MPPT to BB LiFePo4 at such a low voltage. I have free returns on amazon prime, so, considering returning for a different option (maybe two smaller panels in series). Or would it make more sense to just get a good PWM, and then expand with a solar suitcase with another charge controller if my needs increase?

My other concern is that I have no way of testing the panel until I get a controller, and one post on Lensun recently has made me start to doubt that it is a good choice.

Cheers,

FrugalNomad

 

[Maast]

For a MPPT controller it'll need about 1.5 times the battery voltage to turn on and work properly since they're (usually) whats called a 'buck' (voltage reducing) converter. What you need to do is get the same panel again and then wire them in series.

 

[mikefitz]

The Victron range of mppt solar controllers need to 'see' a panel voltage, the panel open circuit voltage, 5 volts higher than battery volts before powering up. The unit will continue operation until the panel voltage is less than 1 volt above battery volts.
Your test indicated the panel is somewhat marginal on volts and is different from the Amazon specification. You could use a PWM controller, available at low cost up to 30 amps rating, that would allow another panel in parallel. Since you need to extract maximum solar power available, a mppt controller is preferred, as well as increasing the power to the battery by up to 30% more from typical panels, and allowing panels in series, they have more accurate and compressive user control over charging parameters than many PWM controllers.

In your position I would return the panel and search for more ideal replacement. An alternative would be to add a second panel of the same type and use two in series.
Mounting and security of the panels is a challenge but I guess you have plans in place for this.

Mike

 

[GSXR1000]

Hello DIY Solar Forum,

This is my first post to the forum. I am putting together my first "system", but just the start of one, that hopefully will expand as my vehicle changes over time. I have searched for this minimum voltage for MPPT, and found some posts that make it sound like I need at least 17 volts to use MPPT to Lithium. Is that 17 volts Open circuit, or Max Power voltage?

Currently traveling in a Prius, and want to power a small 12VDC compressor fridge, and maybe some other devices from time to time. So, after mulling over the options, I decided to err on the side of safety, and ordered a Battle-Born 12V 100ah. My water jugs never freeze, so I doubt I will have a cold charging problem.

I found a Lensun 110watt 18V flexible ETFE on amazon that is the perfect size for mounting on the back hatch glass. The only problem is it said 18V on amazon, but 16V on the panel label:

Amazon Electrical Information:
Peak Power: 110W
Solar cell efficiency 23%
Maximum power voltage: 18v
Maximum power current: 6.11A
Open Circuit voltage: 21.24V
Short Circuit current: 6.72A
Power allowance range: +/- 3%
Maximum system voltage: 500V

Panel Label:
Model LS-110FX2-SUN
Pm: 110W
Vpm: 16V
Imp: 6.88
Voc: 18.88
Isc: 7.56A
Max System Voltage: 500V
Test Condition: AM=1.5, E=1000W/m Tc=25 Deg.C

This must be a different panel. On a grey overcast afternoon in SC, it measured 17.14VDC open circuit. I don't yet have a charge controller, but was hoping to go MPPT, and allow for adding another smaller panel in parallel, possibly in the future. But I'm thinking this will not work for MPPT to BB LiFePo4 at such a low voltage. I have free returns on amazon prime, so, considering returning for a different option (maybe two smaller panels in series). Or would it make more sense to just get a good PWM, and then expand with a solar suitcase with another charge controller if my needs increase?

My other concern is that I have no way of testing the panel until I get a controller, and one post on Lensun recently has made me start to doubt that it is a good choice.

Cheers,

FrugalNomad

you really can't hook a second "smaller" panel to the charge controller without losing a lot on larger panel... maybe just run 2 PWM controllers

 

[FrugalNomad]

Thank you all for posting replies. I returned the Lensun (First Amazon return, simple/easy, dropped off at Kohls nearby).

I’ve decided on Will’s favorite MPPT Epever, 30A with MT50, and I’m taking a chance on 4 of the Kingsolar cheap 50W ETFE Sunpower knock-offs (2 for mounting in series, and 2 for backup or “portable 100W series suitcase” should the mounted ones continue to work).

I realize that flexible degrade faster and don’t last very long, but weight and space are always an issue. I will report back on how this beginner system works for me.

Cheers,

FrugalNomad

 

[Impatient]

Bump. Between this and your subsequent KingSolar experience, it sounds like Amazon needs to police their sellers’ claims a bit better. I know these are old posts, but I was drawn to them because LenSun has a model with good form factor. Nonetheless, if their specs are bogus, why trust them…or Amazon (well, at least Amazon might allow returns within 30 days…which is somewhat compelling).

 

[ken_am]

Hi Impatient, that has always been 1 of my major concerns when buying on line. The advertised description either is incorrect, or incomplete making online comparisons impossible. Caveat Emptor