Total novice, need some guidance for small system

[TFoil]

Hi everyone

Just looking for some guidance and advice for a system that I have most parts for. I will be helping with the system but had no involvement in the purchases.

Parts thus far:
2x Risen 450W panels
2x Ecoworthy 25.6V 100Ah LFP batteries
Victron 100-20 MPPT charge controller

From some other bits of advice I've read I used the MPPT calculator on Victron's site and it looks like the controller might be too small if the panels are put in series.
*At his point it will basically just store charge and be used to recharge some devices. Kind of a proof of concept stage.
Eventually it should shoulder some backup duties.
But for now, can someone make some recommendations in terms of additional components I need to get things up & running?
Expanding solar input and battery capacity won't be happening in the near future unless perhaps massive price drops and/or technology developments.
Sorry if I'm not providing the required info, new to this, just let me know what I'm leaving out.
Basically just want to be able to have this system safely charge these batteries.
Looking at putting panels in parallel to remove any max voltage issue with the Victron.
Distance of Victron to panels will be 30 feet max. From Victron to batteries, under 5 feet. Some cabling was ordered and should be arriving within the next week or 2 but I have no specs on it.
Should the batteries be in series or parallel...and is that choice influenced by whether the panels are in series or parallel?

Any guidance and advice will be very much appreciated!

 

[DIYrich]

Basically just want to be able to have this system safely charge these batteries.

Wire to connect everything.

If you actually want to use the power, then you might want fuses, power distribution panel, etc.

Note:
The Victron is capable of 12/24/48v.
The battery is 24v (25.6v) in parallel, or 48v (51.2v) in series.

I believe your panels are Vmpp 44.0v, and Voc 52.82. two in series are 88.0Vmpp and 105.64Voc
I believe the Victron requires Vmpp at Battery Voltage plus 5v, and 100Voc.
So, you won't be able to charge two batteries in series (Vmpp of 44.0v is not high enough to charge a 48v battery).
With the panels in parallel, you can only charge the batteries in parallel (24v).

I don't think you have a compatible system to put the batteries in series (panel voltage too low for Victron).

 

[KnobCountry]

As Rich says, those panels are likely able to reach voltages of 51 or slightly higher in cold conditions depending on the specific model #

So you should be good to run them in parallel and set the system up for 24v with the batteries in parallel as well.

48v is not reliably achievable with those panels in parallel and the controller could be damaged by series. Sticking with the native 24v in parallel makes it dead simple. No balancing issues.

10awg PV wire should be good from PV to controller and controller to busbar/batteries.

 

[mikefitz]

Should the batteries be in series or parallel.

What voltage are you designing the system for, 24v or 48 volts ?
With the parts you have you are limited to a 24 volt system, batteries in parallel. To avoid exceeding the controller limit, connect the panels in parallel.
You have 900 watts of panel, to recover all the available power at 24 volts, you need a 40 amp controller.
It's important to know what voltage system you had in mind, before offering further advice.

 

[TFoil]

DIYrich, KnobCountry, Mikefitz thank you all for responding
Knew this was going to be quite a learning curve.

So the panels are actually rated a little lower! Vmmp of 41.3V, VOC 49.7V, lmpp 10.9A, V Temp coeff -0.29

The system was intended to be a 48V one.
So if panels in series is a hazard to the controller... panels & batteries in parallel seems to be the way forward.

I would like to eventually incorporate this system into providing some kind of failover backup.
FWIW I'm in the Caribbean so getting daytime temps below the 25 deg. Celsius is pretty rare.

Is there any way to add a small load to lower the incoming voltage to the controller? Like hooking up an IP camera or two?
Would that be rolling the dice on keeping the Vic safe?
Thanks again for the replies.

 

[mikefitz]

Would that be rolling the dice on keeping the Vic safe?

The two panels in series are just too close to the 100 volt limit, it's possible you may be OK , and also not OK. The ideal solution is to exchange the 100/20 for a 150 /35, twice the cost, but you will have a reliable 48 volt system, ( and the possibility of adding a series string with similar volts in parallel).

 

[DIYrich]

FWIW I'm in the Caribbean so getting daytime temps below the 25 deg. Celsius is pretty rare.

Morning temps below 25 c is what risks damaging the inverter. With a Voc of 49.7 it only takes 23 c when the sun comes up to be at the 100v max Voc.

 

[TFoil]

The two panels in series are just too close to the 100 volt limit, it's possible you may be OK , and also not OK. The ideal solution is to exchange the 100/20 for a 150 /35, twice the cost, but you will have a reliable 48 volt system, ( and the possibility of adding a series string with similar volts in parallel).

Long story short: looks like a 24V parallel panel, parallel battery system is what it will be, running with the 100-20 Victron.
So there should still be some value in using fuses on each battery, a DC breaker for the panels?
Thanks again for the heads up about using the AWG 10 wiring.
Guessing with a simple set up like this, aside from the rookie mistakes that Will Prowse's video outlines, it should be good to go.

 

[TFoil]

Morning temps below 25 c is what risks damaging the inverter. With a Voc of 49.7 it only takes 23 c when the sun comes up to be at the 100v max Voc.

Well just been informed that my plan of growing the system to possibly accommodate some degree of failover backup will NOT be happening.
So as it stands, the system will simply be charging the batteries for subsequent use to charge a specific device, which might be a couple times a week. Nope, don't have the power draw requirements on that device.
Charging time, speed, efficiency, etc are all non-issues as long as the batteries eventually charge to some degree.
Hmm, food for thought about the morning temps., things have trended hotter over the last couple years so I did assume a bit.