Quality Solar Charge Controller for 123W Panel and LiFePo4 Battery..? | MotorhomeFun | The Motorhome Support and Social Network

Quality Solar Charge Controller for 123W Panel and LiFePo4 Battery..?

Sep 14, 2020
1
0
Funster No
75,837
MH
Land Rover Defender
Exp
Since 2004
Hello All

I hope someone is able to advise me on my 1st post, and please correct any incorrect assumptions I have made.

I have an old Land Rover Defender 130 camper van which has been happily running a 123W (12v) solar panel going through a simple MorningStar PWM charge controller to 2 lead acid batteries with a total of 130Ah capacity.

Due to age and excessive discharge the batteries now need replacing.

Despite the relatively high initial cost, I rather fancy the Polinovel LiFePo4 deep cycle batteries to give me significantly more usable Ah capacity in the limited space available. They have some BMS built in, but does not include the all important charge cut-off at under 0 to +5 degrees C temperature to avoid damage.

So, I thought what might suit would be a Victron SmartSolar MPPT 75/10. Add a Victron Smart Battery Sense to show temperature and use the VictronConnect app to set the charge to cut-off at under 5 degrees C - will this set up work OK ?

But I am worried that the User Manual says the charger won't start until the battery has 5v less than the solar panel. As the LiFePo4 battery should keep a useable 12v down to say 20% of capacity, does that mean it won't start to be solar charged until almost flat at 0% ?

Maybe I should stick with a simple PWM charge controller - but how to detect and cut-off the charge at under 5 degrees C ?

I've done loads of internet research with no solid answer to my situation, and would be very grateful for your good advice.
=======
PS> My web research has now lead me to Votronic MPP solar charge controllers, which are looking more promising...

(Also posted on the Victron Community Forum)

Many thanks - James.
 

funflair

LIFE MEMBER
Dec 11, 2013
13,473
16,196
Guisborough
Funster No
29,351
MH
MORELO palace
Exp
since 2012
Stick a voltmeter on the panel connections at the regulator and that will give you a clue, my guess is 18+volts so you would be OK.

A Votronic MPP needs a temperature probe when set to LiFePO4 profile so that should do you as well.

I have found Votronic very good at answering question if you want it straight from the experts.

Martin
 
Mar 30, 2019
678
837
East Sussex
Funster No
59,486
MH
Trigano Tribute
Exp
Since 2017
The guys at Photonic universe are really helpful for advice I bought my Votronic 350 duo mppt from them after asking advice for the best controller for my 255watt panel.

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Dec 16, 2019
69
171
Funster No
67,427
MH
C Class
Exp
Newbie
So, I thought what might suit would be a Victron SmartSolar MPPT 75/10. Add a Victron Smart Battery Sense to show temperature and use the VictronConnect app to set the charge to cut-off at under 5 degrees C - will this set up work OK ?
I've got the 75/15 charge controller, superb bit of kit, it will do what you're asking regarding cut off and tons more. The controller has an inbuilt temp sensor, so I use that instead of the additional bluetooth one, although I'm going to buy the external one you're talking about and fit that for better accuracy. It also has a preset for LiFePo4, however check this against your battery manufacturers profile.

But I am worried that the User Manual says the charger won't start until the battery has 5v less than the solar panel. As the LiFePo4 battery should keep a useable 12v down to say 20% of capacity, does that mean it won't start to be solar charged until almost flat at 0% ?
No, it will charge just fine providing your panel is putting out 5v above the battery. So if your battery is at 12v, your panel will need to put out at lest 17v for the charger to kick in. Large panels will usually put out above well above this, for instance mine puts out 30v+. I think the Votronic require a similar margin to start charging.
 
Apr 27, 2016
2,134
1,889
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
I have an old Land Rover Defender 130 camper van which has been happily running a 123W (12v) solar panel
They are referred to as '12V' panels because their voltage range is up to maybe 22V. Since the controllers need to see a panel voltage 5V more than the battery, they are fine for 12V batteries. But no good for 24V batteries, which need 30V or more.
 
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