Inherited an odd wind system, trying to learn about off grid setups

[Internet]

I recently bought a house that was owned by an electrician and he has some interesting stuff set up that I have been trying to learn about. The previous owner unfortunately died and nobody knows anything about all the stuff he set up, but I've been having fun learning about it. First he has a 4kw grid tied solar rig on the roof, which is nice as it's part of an old renewable scheme so I get paid something to generate electricity even if I use it. That's all professionally done and self explanatory.

The other main thing I found was a very interesting off grid wind setup. He has a huge pole with what looks like a 500w to 1kw domestic wind turbine on it. It runs down into a cabinet that has a cheap 12v wind controller connected to two 12v 72AH lead acid batteries in parallel.

He also had this interesting thing where a light detector switched on grid charging at night and then he ran DC lights off it, but I am ripping all that out as I just want to use whatever I can get out of the wind for free.

So I've started learning about how these systems work, and I bought what is probably a very oversized inverter to run AC off the batteries. I am in the UK so we are 240v, and I got a 2500w (5000w peak) 50hz pure sine inverter. I wired it to the batteries using 16 mm cables, and it works but I have some issues/questions:

1) The batteries seem to float around 12.4v to 12.7v (measured by inverter) and when the wind is blowing they get up to 13v+. Is this low, and is this an indication that the batteries are old and dying? Or is that normal for a charged 12v battery?

2) The voltage drops when there is load on the inverter, dropping a whole volt when under about 250w load. I'm guessing this is normal as we are drawing charge from the battery?

3) I tried putting 1000w+ load on the batteries just to see if it could handle it, and I got a low voltage cut out at the inverter after a second. Voltage dropped to 10.5ish before it cut out. Am I right in assuming I would basically need a much bigger battery bank and thicker cables to be able to draw that large a load without dropping voltage into the red?

4) It's clear that I bought a much too large inverter. Is that going to be a problem? If I am only putting 250 to 500w load on this system, would a lower rated inverter actually be more efficient or is it not a problem?

Looking forward to any advice and answers anyone can give me. I've been reading up a lot on this since moving in. My goal is to add a bunch more battery capacity and more solar panels to the system. My sheds are all wired up with lighting and extension leads (to run power tools) that come from the house via an external socket, and I'd love to be run them off the batteries instead.

 

[sunshine_eggo]

1) it's low, and it may or may not be a sign of dying batteries. 12V lead acid are typically charged to around 14.5V and float around 13.5V. The wind should have some sort of charge controller associated with it.

2) 1V drop from a 25A load on 144Ah of battery sounds excessive. Likely another sign of degraded batts. Could also indicate excessive voltage drop due to wiring or connections.

3) Would expect that you could get 1000W from that for brief runs and not hit cut-off. Resolve #2 first.

4) 2500W is definitely at the high end of what works for 12V.

Pictures?

 

[Internet]

1) it's low, and it may or may not be a sign of dying batteries. 12V lead acid are typically charged to around 14.5V and float around 13.5V. The wind should have some sort of charge controller associated with it.

2) 1V drop from a 25A load on 144Ah of battery sounds excessive. Likely another sign of degraded batts. Could also indicate excessive voltage drop due to wiring or connections.

3) Would expect that you could get 1000W from that for brief runs and not hit cut-off. Resolve #2 first.

4) 2500W is definitely at the high end of what works for 12V.

Pictures?

Thanks for the answers! I'll be able to take some pictures tomorrow, it's dark here in the UK. Word of warning that this setup does not look particularly well done or safe, and I think I need to rebuild it in a shed and do it right. But for now I am learning all I can about this and planning a new system.

The wind system does have a charge controller and it seems to be working, but I've never seen the batteries over 12.8v with the wind stopped. So maybe it is old batteries.

BTW isn't 250w actually just over 10a? It's a UK system so 240v. Or am I miscalculating that?

I was getting immediate low voltage dropout from the inverter under any load and fixed it by scrubbing the corroded connectors and installing bigger wires. How could I test whether the drop is still due to poor wire connections?

 

[sunshine_eggo]

Thanks for the answers! I'll be able to take some pictures tomorrow, it's dark here in the UK. Word of warning that this setup does not look particularly well done or safe, and I think I need to rebuild it in a shed and do it right. But for now I am learning all I can about this and planning a new system.

The wind system does have a charge controller and it seems to be working, but I've never seen the batteries over 12.8v with the wind stopped. So maybe it is old batteries.

After fully charging with 10+ hours of rest, 12.8V isn't bad.

BTW isn't 250w actually just over 10a? It's a UK system so 240v. Or am I miscalculating that?

250W /12V = 20.83A (I rounded up assuming some voltage drop)

I was getting immediate low voltage dropout from the inverter under any load and fixed it by scrubbing the corroded connectors and installing bigger wires. How could I test whether the drop is still due to poor wire connections?

Get a voltmeter/multimeter

1. Measure resting voltage at battery terminals
2. Apply 250W load
3. wait 30 seconds
4. Measure voltage at battery terminals
5. Measure voltage at inverter terminals

A big drop between 1 & 4 suggests weak/undercharged batteries.

A big drop between 4 & 5 suggests bad connections or insufficient wire gauge.

 

[12VoltInstalls]

Could also indicate excessive voltage drop due to wiring or connections

wired it to the batteries using 16 mm cables,

That is an issue imho. I think that’s like 6ga- I used 2/0 on a 1200W inverter.

250w actually just over 10a? It's a UK system so 240v. Or am I miscalculating that?

If you meant inverter load versus inverter input a 10A 240V is 200A at 12VDC, plus any losses and inverter inefficiency.

 

[Internet]

OK so here are the photos. Word of warning as before that this looks like a pretty dodgy setup so I'd appreciate any advice. This is how it was set up when I bought the house, the only difference is I added the inverter and replaced some old thin crocodile clip wires on the batteries with new terminals and 16mm cable.

The turbine is just a tiny 500w one I think based on the controller. I was experimenting with it again today, when the wind was high it pushed the battery to over 13v measured at the inverter and without wind it settled at 12.7v which should be full charge. I ran a 2.5a 240v laptop charger off it for about 30 mins and unfortunately the voltage dropped slowly to the 10.5v cutoff and I had to disconnect it. With no load on it, it's reading 12.3v at the inverter.

This is a tiny system so I wasn't expecting much out of it but that seems very odd, could the batteries be too old and damaged or the wrong type? I know nothing about the system and am just learning how everything works.

From all the comments so far, it's clear that to get any kind of higher wattage out of the inverter would require much thicker cables. The inverter is much larger than I needed (still learning ?), and the batteries may be old and damaged.

Ultimately, I'd like to build a new combined solar and wind setup in a large workshop we have. I'm learning about battery types and health, inverters, and such now while planning it. But any more tips would be appreciated! Next step is figuring out how to test the battery health I think.

 

[chrisski]

There's so much advice I want to give, but my experience is only research and I never decided to build my project.

I recommend Fieldlines.com. That is the most active wind forum I found.

 

[12VoltInstalls]

I'm learning about battery types and health, inverters, and such now while planning it. But any more tips would be appreciated! Next step is figuring out how to test the battery health I think.

Somewhere on this usenet forum there is a nice writeup for using a a hydrometer to test battery electrolyte. That will tell some about the batteries.

I notice the batteries aren’t a matched pair. A pair of new fla marine batteries from walmartha here is like us$300, so probably there they’ll cost 400euro each.