Advice needed on adding modern panels to a 10 year old installation

akallen
akallen Registered Users Posts: 10 ✭✭
in General Solar Power Topics #1
Hi,
I'm running tracking arrays using old Siemens panels with Vmpp of around 16.7 or 33 depending on the panels. They're setup as a 48V system back to my Trace inverters (SW5548s). I replaced the old charge controllers with the newer Xantrex MPPT units. My question is on the addition of another tracker with a whole new set of modern panels. It is highly unlikely I can buy current state of the industry panels that will mesh seamlessly with my existing setup, voltage-wise. I'm wondering if anyone has thoughts on the losses that can occur due to the mismatched voltages vs the options I might have such as dc to dc voltage regulation or perhaps even micro-inverting and bypassing my 5548's altogether. Probably other ideas as well. Any thoughts?
I'm new to the forum btw, so its not clear to me what the standards are in the Q&A. Thank you,
arlene
Twin Xantrex 5548 (48 V) with two MPPT60 controllers and Rolls batteries, Pre-2008, so the NEC was simple at the time.
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Advice needed on adding modern panels to a 10 year old installation

    Welcome to the forum. You're doing okay so far. :D

    If you're going to add a whole new tracker & array, the easiest solution is to add a new charge controller.

    Otherwise the rule-of-thumb of panel matching is to get the Vmp within 5% for paralleling and the Imp within 5% for series connections.

    Mostly it depends on the exact details of your existing array and whether or not you're near maxing the controller's capacity.
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  • akallen
    akallen Registered Users Posts: 10 ✭✭
    #3
    Re: Advice needed on adding modern panels to a 10 year old installation

    My limitation is the run back to the inverters and charge controllers. I was going to take the array and parallel it onto the existing copper going back to the equipment, hence my question. I hadn't really thought about a separate charge controller and run back. Around 150 ft or so. Certainly an option. Charge controllers still have capacity, so that's not an issue yet. Maybe the 5% difference will turn out not to be a problem. I'll do a panel survey and see what the options are. My thanks!
    Twin Xantrex 5548 (48 V) with two MPPT60 controllers and Rolls batteries, Pre-2008, so the NEC was simple at the time.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Advice needed on adding modern panels to a 10 year old installation

    150 feet is a lot of distance. There could be some really big Voltage drop. If you were to max out the controller using a 48 Volt array @ 4 Amps you'd need 10 AWG for that run to keep the V-drop below 3%.

    It still wouldn't be enough power for those batteries, though. Not by a long shot.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Advice needed on adding modern panels to a 10 year old installation

    you may be able to do it with the same wire and controller if you will not exceed the operating abilities of the cc that causes excessive waste by rewiring the pvs for a higher voltage within each array. in this manor if the present wire is good for 1 array then doubling the voltage of the array cuts the current in half and this would allow the current from the new tracked array to be paralleled to the present one.

    as coot mentioned, that is a long way for that run so you may need to examine that aspect.
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