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diy solar

Balancing SLA, battery profile and charging from the grid?

Archerite

New Member
Joined
Sep 22, 2021
Messages
102
Location
Netherlands
I am just starting and still learning about solar power and everything related to it. Because of budget and space limitations I only have a relatively small experimental setup:
- 3 x 10 Watt panels
- Victron MPPT 75/15
- Victron SmartShunt
- 2 x Kung Long 12v SLA 7.2Ah. (WP7.2-12)

Yeah, the victron stuff does not seem like "low budget" but I really love the app and possibilities to add data logging later. These components were selected after weeks of watching youtube and reading about the details of wiring and safety. My main goal with this setup is learning and if possible power a few small computer/networking gear. I know I need more panels and wattage for that though ??

The first experiments from behind the window were quite dramatic and I only got like 2-3 watts at a maximum. Putting the panels on the balcony for testing is possible but I did not have any connectors yet...so twisted wires it was...I could get 11-14 watts with two panels in series. The third one only arrived yesterday after the sun was hiding behind the roof already. Today all three are outside with better connectors (not weather proof by any means!) and I got 13 watts...which was a little disappointing. But it was only around 10:30 so not full peak sun efficiency yet and there are a couple of clouds here too.

Sorry for that long intro....but here are my main questions:
  1. I have only connected a single battery at the moment to the MPPT controller. The reason is I learned about balancing the batteries and that they need to be at the same (or very close) voltage level before putting them into a parallel battery bank. Is this true? I don't have a wall charger yet but I am looking at getting a victron one....because of the monitoring with Bluetooth and for those days the sun does not give enough power for my needs. (which are still undetermined but I am guessing around 20-40watts at 12 volt)
  2. Second question about the charger is how to hook it up. Of course the positive and negative wire are obvious...but do I charge each 12v battery on it's own? Both as a single larger 12v 14.4Ah? Can I leave the MPPT connected while charging from the BlueSmart? Do I need to disconnect the PV while using the charger?
  3. For the battery profile I have done my best to match the settings from the datasheet into the MPPT. But I am still not confident if I chose the right values for everything. Some help with that would be really appreciated.

I am sorry if these are dumb questions or in the wrong place at the forum. New to solar and on this forum too ;)

The idea is to get the VE.Direct logging data into HomeAssistant and/or grafana for both monitoring and dashboards. No idea what components I am going to use for it but that is roughly my plan for this tiny setup. I also like the ability to charge my phone, tablet and powerbanks from the power collected by the panels. I have tested it with a USB QC2.0 charger board connected to one of the batteries and it uses around 1.3Amps at 12v for an hour or two per device.

I am sorry this got so long, but it doubles as my "introduction" I guess :ROFLMAO::ROFLMAO:...

Thanks for reading.
 
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