MPPT upgrade

[Raven]

Currently I am using a PWM 7 A charge controller. It came with the 100 watt solar panel. I plan to upgrade the battery from a group 27 to two 6 volt batteries & may add another 100 watt solar panel. I would like to know if I should upgrade to an MPPT 20 A or 30 A.

[Jchism759]

Looks like you will need to upgrade the existing charge controller if it is a 7Amp PWM. This controller is rated to only handle about 105 watts of solar input, so adding another 100 watt panel will overload the charge controller. If you still have the specifications for the charge controller you can verify this information.
If you do upgrade to MPPT it may be good to upgrade to the 30 Amp controller, this will allow you to have up to 400 watts of solar power input if you decide to add more panels later. The 20 Amp charge controller will max out at 260 watts of solar input.

Good luck!

[Raven]

Thanks so much for this info. Exactly what I needed to make an informed decision. Will probably go with 20 amp as 200 watts will be ample for our needs.

[Jchism759]

One more thing to consider is price and efficiency. A 20 amp PWM can be found for less than $20 and a 20 amp MPPT will be around $100.

The MPPT will only give about 20% to 30% more efficient or additional charge to the batteries.

If the added 100 watt panel will be sufficient for your charging needs then you may not need to pay the $80 or more extra for the MPPT controller.

[Raven]

Definitely something to think about. Thank you