Hi,
Actually I was not really planning on buying more batteries at this time, I wanted to go lifepo4 in a few years, but I could buy some unused powersafe 12v92f for 40€/piece.
Some may find it to much but used batteries are verry rare over here at those prices, I've seen them used for 200€ on sites.
They were not new, some 2y others are 4y old. Seller says that they were a long time not being charged, so I hope there is not to much sulfation on those plates. All the batteries are reading between 12.25 and 12.65V, when connected to a 55W car bulb the voltages were not crashing, I saw a drop of 0.1-0.2V. So I guess that's ok.
My current setup:
800W DIY solar panels, 400w grid tied (26-30V mppt tension), 400W are feeding the batteries in 12V configuration
The panels (400W) are connected to an MPPT-10 Juta controller, I made 2 holes in it and put on 2 small fans to cool it down, no problems so far, I mostly see charging with 15- 20A, around 25 A max. I did soldered the wires directly to they pcb. Without the fans it goes in temperature protection.
- 12V 155Ah powersafe 12v155f (7years old)
- 12V 90Ah northstar 12v 90ft (at least 5years I think 2e hand)
- 12V 55Ah pbq agm long life (the litle one of the system :p) (must be 7 years as well)
A few weeks ago I drained it to 11.5V (under load) with a load of 4A and I had 206Ah
With a load of 6-7A the northstar is giving me 52.3ah (623wh) drained to 11.3V under load
The pbq was giving me 37ah drained with 7-4A to 11.3V under load
The powersafe was not tested yet.
All batteries are in parallel with a few brakers and switches. There is also a 1500W sine inverter.
The originally plan was to power TV and receiver (80w), workshop lights (180w), electronic chargers and some small powertools, that was working verry well, but I was facing a high idle current of the inverter, +/-2A but that dropped to 1A when voltage was over 13.5V. I didnt want to disconnect/ connect every time to safe power, so the next plan was to drain the battery overnight with a step up converter (constant current and constant voltage), it was set at 1.5A and 35V this puts out 0.7kwh every evening/night/morning. This is working verry well a few weeks now, I know the efficiency is bad (75% for the whole system, without battery efficiency) but it works and I dont want to wake the grid company before I have my next solar setup (2-4kwhp) approved.
Ok now you know my basic setup, we go further with the other batteries.
So I placed the 10 batteries of the 92Ah in parallel, yes I know most people here would shoot me
But this was the easyest way to charge them for me, they are all hooked up with 10mm² solid wire, for now it will do the trick since the load is less then 10A I don't expect a lot of unbalance here.When I have more time I will make more cables to connect and have 20mm² together. The plan is to provide each battery with a fuse, I was thinking to connect 20A car style type, it should protect other batteries when one would fail. And then have one wire of 50mm² to the mainfuse and switch and go to the inverter.
But for now it will do.
First I want to do the best treatment for getting the batteries in good shape! All batteries are in parallel now and I'm charging with about 10A during the day and 3A over night. I know this could take a few days to complete. But I don't think it will harm. What is the best way after such a long time of storage?
I read a lot about batteries! So I go on with what I know.
-these are AGM type mostly used in telecom and hold at float
-long periods of uncharged /partial state will make them sulfate
-to high charging voltage will make them gass and will damage them (no electrolyt can be filled back in)
-extreme temperature will make them sulfate also
-undercharged will make them sulfate
Now I'm a big scared about undercharging because of the sulfation as I'm planning to have them always at floating voltage.
How will I use them?
During the day I will charge them with the 400w solar system, voltage will not go higher then 13.8V (when its colder sometimes 14V for a few hours) and the solar controler has temperature compensation. So actualy I will charge with floating voltage. During the night I will dicharge and will take out 1-1.5kWh, about 5-6 amps per hour. During the day solarpower will put back in the consumed power and will hold voltage around 13.8V probably not more then 3 hours a day. If the next day is sunny I will use more the night before if there will be not much sun I will use less power to feed the grid.
Will this cause a lot of sulfation on the plates? If so how could I minimize sulfation?
I know I don't need such a system but it's fun/hobby
, the grid is very reliable over here, I could count on one hand the interuptions in one year, and if there are, normally they don't last verry long <30min. But I think it could be a problem verry soon when there are more and more people with solar, at this time we actualy buy power from neighbour countries because we can't produce enough. That could be a problem in the future.
I hope this post is not to messy :p
foto as it is now:
