Adding to my existing system...

[LoveSailing]

Hello! I'm new to this forum, but not entirely new to solar. I have an old sailboat with limited solar real estate, and here are my current specs:

House batteries: Duracell Ultra AGM 105ah (2) in parallel
Panels: (2) Siemens 55watt 12v panels in parallel, connected to a Renogy Wanderer pwm controller
(1)HQST 100watt 12v panel, connected to a Victron Smart Charge 30amp MPPT controller

I just installed the Victron unit, and it's great, but I bought it with adding to the system in mind...

I ordered 2 new TP Solar 12v 50 watt flexible panels that I want to mount on my dodger. They should arrive today.

My question is, how should I connect my new panels to the Victron unit? The new and existing panels will not be close together and wiring will be tricky. Should I install a buss bar near the controller and wire the three panels in paralell? Or should I wire the 2 new panels together in series, then...?

Any thoughts and input would be greatly appreciated. Thanks!

 

[LoveSailing]

I just realized that adding the specs of the 2 new panels and existing 100watt panel would probably help.

 

[Hedges]

Voc and Vmp differ significantly. If you parallel HQST with 18V output and flexible with 24.2V, one backfeeds the other.

If you had PWM charger I'd say use a diode in series with lower voltage panel, then parallel the panels (assuming charge controller OK with current.)
Since you have MPPT, should get separate MPPT charge controller.

I mix panels, but much longer strings in series, so I can put enough of each to reach same voltage.

 

[LoveSailing]

Voc and Vmp differ significantly. If you parallel HQST with 18V output and flexible with 24.2V, one backfeeds the other.

If you had PWM charger I'd say use a diode in series with lower voltage panel, then parallel the panels (assuming charge controller OK with current.)
Since you have MPPT, should get separate MPPT charge controller.

I mix panels, but much longer strings in series, so I can put enough of each to reach same voltage.

Thanks for your reply. I'm trying to figure out if I overdid it with the victron controller. If I can't utilize it with these new panels together with my existing one, maybe I spent too much money. Or, maybe that HQST panel is inferior to some of the newer ones out there. I do have a pwm controller also, and it's running my really old panels. Maybe I just get rid of those, since they are from like 1995, and down the road add a similar panel in parallel to my HQST...

 

[Hedges]

Could use the PWM you've already got.

Nothing wrong with the HQST, just a different voltage. You can parallel more of the same voltage, even if different brand.

MPPT - are you sure 18Vmp of HQST is even sufficient for MPPT operation? check specs of your charge controller. Typically we connect several panels in series.

Looks to me like PWM is a better fit for the 18V panel, and MPPT better for 24V panel.

Don't know the specs of your Siemens panel.

 

[LoveSailing]

Could use the PWM you've already got.

Nothing wrong with the HQST, just a different voltage. You can parallel more of the same voltage, even if different brand.

MPPT - are you sure 18Vmp of HQST is even sufficient for MPPT operation? check specs of your charge controller. Typically we connect several panels in series.

Looks to me like PWM is a better fit for the 18V panel, and MPPT better for 24V panel.

Don't know the specs of your Siemens panel.

Thanks again for the reply, maybe I will try switching it up like that. My mppt controller has only been connected to that HQST panel for about a week and my batteries are already in much better shape, but I do get why I would want higher voltage there. Maybe I'll put the two new 50watt panels in series. I'm attaching the Seimens panels specs below. My other idea was to see if it was possible (because of similar voltage specs) to connect the Seimens panels with the HQST one, however the wattage is off...

 

[Hedges]

Siemens and HQST have similar voltages, different current. They can be connected in parallel but not in series with each other.
The voltage is probably good for PWM.

This will deliver constant current around Imp, into a low battery of 12V HQST would give 12V x 5.83Isc = 69W if panel is cool. Well below full power; this shows one of the benefits MPPT offers. As battery comes up to 15V, close to Vmp and more power delivered.

If connected to MPPT it will work, but power output might taper off as battery voltage goes above 12V (5 or 6V below PV panel Vmp) but still produce some up to battery voltage 15V (5 or 6V below Voc).

If you had two HQST in series and two Siemens in series, then the voltage would be enough for MPPT. It would deliver full power at any battery state of charge.