Hi,
i work in cctv and deploy off grid solar cctv towers
just looking for help on the best set up to get the max out of the batteries and solar
currently we have 3x 125AH agm 12v batteries, a victron mppt 100/20 and 2x renogy 175w 12v solar panels and a insytly BMS system
the 3 batteries are wired in parallel via a busbar as all the equipment runs on 12v which in turn give us 12v 375AH we have some towers where the solars are kept at 12v via busbar and some we have wired the 2 panels together to make a 24v solar system
we have noticed on the 24v solars the current on the solars drops by half
the main end goal is to try and make the best of what we have to get more time between having the go the the site and swap out the batteries with fully charged ones
if anyone could help with any settings or tips so we can get the most amount of solar back in to the batteries to keep them charged
Hello,
Just to understand, The BMS system is for ? Controlling and measuring the consbutions right ?
3 X 125AH X 50% (max) = 188AH
2 x 175W / 24V = 14,5A @24V from the solar panel
The best to results to charge an AGM battery is C10 or 10% of is capacity => 12,4 A
We ned to multiply per 3 as we have 3 bateries… 37A during 4-6 hours to recharge the batteries…
we need 222AH to complete a charge…
So with the existing panel we can get 14A @24V (solar pannel in serial mode - chain ) => around 28A @12V
28A x 5-6 hours of sun => 168AH, a bit far to complete the charge…
To optain the best result, is to cable the solar pannel in serial, remove one of the 3 battery.
If someone else could affirm or not my estimation of the system…
as its runs cctv the batteries dont run down the empty they shut down at 11.8v
i think im right in saying the victron mppt as a watt limit etc and in 12v thats 220 so we go far over that with 2x 175w that why i thought 24v would be better and the vbatt+5 for charging etc
the other thought was to swap to 305ah lifepo4’s
and/or changing to 200 or 300 watt panels instead
To be more accurate, we need the context of the system…
If your system is located in Finland or Italy the conditon are really not the same… (just to understand )
But you first need to define or tell us the criteria for the running CCTV. always ON, only some hours per day, how many day of self consuming needed … Power consubtion of the CCTV system…
To anwser technicaly
11,8V is… 70%/65% of a 12,8V AGM battery SOC… The system could works not the problem… The goal is to keep the battery healt in good condition… and not charging a battery at the “maximum” too often is the battery death with in few months …
For the MPPT, in fact it needs Vbat + 5V to start… so with 24v nominal solar panel voltage there will be no trouble to start… (even when the weather is cloudy)
Like I say, the x2 175W solar panel + MPPT + X2 175AH batteries wil work really fine.
(I use to have x2 150W solar panel + 100/20 MPPT + x2 135AH batteries on 2 systems for other purposes and one is running for 4 years now)
Lifepo must be OK too, just knowing, no recharge when temperature drop lower than 5°(internal)…
But perhaps you need a smaller battery. In fact you can use 50% of the Capacity of a LifePO vs 30-35% of an AGM… And you can drive more current to charge it… so a bigger MPPT is needed…
So to run the system with what you have in the best condition, (without knowing the CCTV consubtion) is to remove one of the 3 AGM battery.
If you whant to do thing step by step…
You can put up to 4 175W panels solar in serial mode if I’m right… and in this case add the third
battery. But we are at the high limits of the MPPT…
One point… I miss on my first answer, is the MPPT current is limited to 20A … so a bit small
main goal, is to run a cctv tower off grid 24/7 in the uk power consubtion of the load is about 50/60 watts everything runs on 12v but the cameras disconnect when the battery drops below 11.8v so the goal is to keep the overall battery voltage above 12volts
we have found 3x 125ah 12 volt batteries can run without solar for a week
so if we use what we have 2x 175 watt panels in a 24v config using only 2 batteries you the numbers work out better than having 3 batteries in the tower as the panels would be able to cover the load etc
uploading to images of the 100/20 from the other day when we did some tests one the solars in 12v and the other the same setup just solars wired for 24v
if i can add anything to help a rough paint drawing of how its wired up or anything let me know
Good !!
With Victron Connect app, you can also see the solar panel production with the “history” tab
And inside you can also see… Bulk Time, Absortion and Floating …
And it can help you to understand how the system is working… even the BMS can help it that…
Is you have some available history it will helps…
60W under 12V = 5AH in full mode… 120AH per day. So if you what the system to run 24/7
You solar panel in fact need to cover the daily CCTV consubtion + batteries charging…
Converting to Daily WH = 120AH x 12V = 1440WH/Day.
if you look at : MPPT Calculator - Victron Energy
follow the wizard and setup 175 x2 solar pannels in seral mode… it will propose you the 100/20… this is right !
here the result …
But you will see the Daily production … and the system wil cover the need only during May, June and July … the rest of the time the system willrun out of energy, so cut the CCTV…
thank you so much for all your help
i dont have any other snap shops but the engineers are out tomorrow so i will ask them to get me some and post them
This is a good study case …
Just for your info… here the BMS (Victron) giving the SOC and estimated life time capacity… (This is small lead acid batteries on a truck and I limit the discharge to 85-90% of SOC )
I have 2 days of batteries… (really 4 to 6 days) but the SOC will be lower…
And the goal is to keep the batteries working good to prevent trouble and surprises…
