Lifepo4 battery/panel/controller questions

[Gphoto125]

I purchased a lifepo4 110ah Litime w/bms and cold temp shutoff battery to replace my tired agm 41/2 year old battery for a small camper, which was connected to 1-100w panel and a pwm 20a controller. I thought the 100w panel would only just take longer to charge the new battery, instead I am told I should have 300w of panels to charge battery successfully. Now it sounds like I might also need a 30a controller and maybe it should be an mppt instead of pwm ? The total amps I would draw on this system if everything was running ( maxxfan-6-7 amps, on demand water pump 3 amps, and small led lights 1.5 total amps) would be appx 10-12 amps. I use the fan in summer only. I live in NM, so sunlight is no problem. Any insight as to just using 2 100w panels instead of 3 and keeping my 20a pwm controller ? Or, should I bite the bullet and buy 2 more panels and a new controller? All this because I thought I would save $ long term by switching to Lifepo4. ( should have done more research ! )
Thanks for any suggestions anyone might have….

 

[Topper]

With the integrated bms protecting your battery, your current setup should be 100% fine. It's all a matter of managing your loads, like you have done in the past with your agm. More is usually better, but always comes down to $$..

 

[400bird]

Anyone telling you that you "need" a specific amount of solar based on battery alone doesn't understand math (for a lithium battery, lead is different)

You only need enough solar to recover the energy used. I'm surprised 100 watts worked, previously but if your loads are low enough...

If your only change was the battery, and the single 100 watt panels was enough before, it's probably still enough.

Personally, I'd add the second 100 watt panels just to have the extra charging.

Not really related, but what are you using to monitor the battery state of charge? You may already know this, but you can't use voltage to know anything other than basically full battery and empty battery. The display on your charge controller likely just reads the voltage and puts you a useless SOC.

 

[Gphoto125]

Anyone telling you that you "need" a specific amount of solar based on battery alone doesn't understand math (for a lithium battery, lead is different)

You only need enough solar to recover the energy used. I'm surprised 100 watts worked, previously but if your loads are low enough...

If your only change was the battery, and the single 100 watt panels was enough before, it's probably still enough.

Personally, I'd add the second 100 watt panels just to have the extra charging.

Not really related, but what are you using to monitor the battery state of charge? You may already know this, but you can't use voltage to know anything other than basically full battery and empty battery. The display on your charge controller likely just reads the voltage and puts you a useless SOC.

Thanks !

 

[Gphoto125]

Anyone telling you that you "need" a specific amount of solar based on battery alone doesn't understand math (for a lithium battery, lead is different)

You only need enough solar to recover the energy used. I'm surprised 100 watts worked, previously but if your loads are low enough...

If your only change was the battery, and the single 100 watt panels was enough before, it's probably still enough.

Personally, I'd add the second 100 watt panels just to have the extra charging.

Not really related, but what are you using to monitor the battery state of charge? You may already know this, but you can't use voltage to know anything other than basically full battery and empty battery. The display on your charge controller likely just reads the voltage and puts you a useless SOC.

I plan on taking your advice re. adding another 100w panel. I don’t have any monitor to monitor soc. What would you suggest ? Also, Can I still use my Renogy Voyager 2018 model 20a pwm controller when adding the 100w panel or do I need to : Get a 30a pwm controller, or a 20 or 30a mppt controller? Thanks so much for your help !!

 

[mikefitz]

Can I still use my Renogy Voyager 2018 model 20a pwm controller when adding the 100w panel

Your 100 watt panels generate around 5 amps each maximum, so two in parallel is well within the 20 amp rating of your controller. The manual for the latest version of the Renogy Voyager suggests a maxinum solar input of 260 watts. The default lithium charge voltage is 14.2 volts, if your early model Voyager does not have the lithium option, the GEL setting should be suitable.
Future updates could introduce a MPPT controler that may give a slightly higher yield.

 

[400bird]

5 amps is the panel output (my estimate)
MPPTs are rated for their current output.
200 watts is still within limits of the charger, but using a good majority of the 20 amp capacity, not 10 amps.

 

[mikefitz]

200 watts is still within limits of the charger, but using a good majority of the 20 amp capacity, not 10 amps.

The Renogy Voyager is PWM 20 A rating, with two panels that's 10 amps output for sure.