Solar charge controller, what for?

[PNjunction]

Regarding calibration, you can check how accurate your multimeter is with a low cost voltage standard from this crowd http://www.voltagestandard.com/, for checking LFP batteries I think accuracy down to 10mV is probably enough.

That's a great idea. I run the great risk of turning this into an endless multimeter thread, but I think the simplest tool to get *that you can trust out of the box* is of course a Fluke. It doesn't have to be expensive. I run a recent model "low end" Fluke 114 since there is no need to use my more expensive 87v for my lifepo4 monitoring. The measurements are the same. There are many multimeter alternatives, but only the Fluke comes with a level of TRUST for an out of box experience without intensive calibration.

Man, I hope this reply wasn't a mistake ...

[SunEagle]

That's a great idea. I run the great risk of turning this into an endless multimeter thread, but I think the simplest tool to get *that you can trust out of the box* is of course a Fluke. It doesn't have to be expensive. I run a recent model "low end" Fluke 114 since there is no need to use my more expensive 87v for my lifepo4 monitoring. The measurements are the same. There are many multimeter alternatives, but only the Fluke comes with a level of TRUST for an out of box experience without intensive calibration.

Man, I hope this reply wasn't a mistake ...

I agree with PNjunction. A reliable multimeter is an important tool to have.

While I have professionally used a Fluke meter for many years I have found that the Extech line is as reliable and accurate as the Fluke at a lower cost.

I personally have a multimeter and clamp on ammeter made by Extech and feel very safe using them on energized equipment. Although if I can afford it my first choice would still be a Fluke.

[bungawalbyn]

[QUOTE=karrak;164450]

I am interested to know what controller you are using for this.

http://www.ebay.com.au/itm/331509855668?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

There are guys selling load dump/diverters for wind/hydro in the States who use these.

- It needs more than 4 volts to operate so you will need to connect more than one cell to each device.

-

The little volt meters I'm using for individual cell monitoring are 3 wire, + - 12V with sensor wire

My system is a "Work in Progress" and I would be pounced on if I posted pictures of it. I might post pictures of a system I have installed for a friend when we reinstall it in its new and permanent home in the next few months. Here is a description of my system from a previous post http://www.solarpaneltalk.com/showth...l=1#post154470, One thing not mentioned in that post is that the batteries are from Winston.

I wouldn't worry about that. My set up will be something out of Professor Ratbagy's Manufactory

[karrak]

http://www.ebay.com.au/itm/331509855...%3AMEBIDX%3AIT

That looks like a good start, just a word of warning, remember that your expensive battery relies on this part. A large part of engineering design looks at what sort of things can fail or go wrong with components of/in the design and what impact this will have. If the failure of a part can cause a safety issue or cause expensive damage, steps have to be taken to stop these faults or make sure they can't cause a problem.

When you buy cheap parts from an anonymous manufacturer you do not know how well designed they are, if they uses components that will do the job, or if the components are fakes. Now most of the time these parts work OK although I would always derate their specifications, so if an inverter says it will deliver 150W, assume it will only really safely deliver 100W. If I use parts like this, I assume they will fail and ask myself what will happen if they do fail, actually I also do this with components from well known companies who have a reputation to upheld as well.

In the case of this part, if it fails and does not disconnect the solar panels from the battery when it is full, it will very quickly, and I mean very quickly drive the battery voltage up to nearly the open circuit voltage of the panels of around 20 volts which could cause irreversible damage to the battery. If it fails and does not connect the panels to the battery, the battery could be damaged by being over discharged.

Whenever you are designing or putting together anything always ask yourself what will happen if any part of the system should fail and what the consequences of this failure will be.

While on this subject, do you have any plans to provide an alarm if any individual cell voltages go out of the safe operating range?

Simon

[bungawalbyn]

Hi Simon,

I take your point, only I am not relying solely on one of these. I have a BMS for Hi Lo emergency cut offs should everything else fail for both pack and cell voltages. The module shown is switching charge on and off. I'll have another one in the system set at lesser values to switch on and off my HWS as a load dump/diversion when approaching charge cut out. Plus I'm wiring in cell and pack voltmeters and low cell voltage alarms. I have manual cut offs on both PV in and Battery in.
Everything will be cut off if low cell voltage is reached. All supply to meters etc will come from circuit after the main low voltage magnetic latching contactor (Doesn't need current to hold open)

If a cell goes far enough out of balance to cause a problem without me catching it going there on the meters, then it's probably going to be a cell fault. Any drift should be evident well before.

Until I'm comfortable with it's reliability, I will switch it all off when I go out, and even when comfortable I will probably switch it all off if I'm going away over night or longer.

Hey, life's a risk and the high end craps out too, which can be worse if you believe it won't.

[karrak]

Hi bungawalbyn,

Looks like you have given this quite a bit of thought and done some research on this, will be interested to see how things turn out.

Simon

[bungawalbyn]

We have voltage cut off.

I finally received enough of the bits in the mail to get stuck into the control board, unfortunately not yet all I'm waiting on, so It's no finished set up for you guys, or me.

I have all the heavy cable work done, save the main fuse, but I'm waiting for bus bars to finish all the thin wire work for the controls. While waiting I'm making a poly carbonate cover for the batteries and covers for the circuit boards.

I finally hooked up the HiLo voltage cut off sensor and programmed it. Works a treat. Run the power supply up to cut off 13.8V, main relay cuts current, run the power supply back to 13.3v relay cuts back in. I still have to do the HWS relay that I'll set at Hi 13.7V and Lo 13.4V. I'll start with these parameters and adjust as/if necessary.

A slight change of plans. Turns out after giving it more thought, the idea of individual volt meters for each cell turns out to be not terribly practical. A rats nest of wires and can't power them from cut off side of main contactor. Fortunately whilst browsing Ebay for bits I came across a RC cell sensor.

http://www.ebay.com.au/itm/321502999136?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

$8.50 in Aus, a couple of days delivery, or about $2.40 from Hong Kong with 3 to 4 weeks postage

I've opted for the quick delivery as I'll go nuts waiting any longer.

From what I've seen of how it's hooked up I can power it from the main circuit. ie will cut out if main contactor is tripped.


I'll post some pics when it's finished.

[PNjunction]

I've opted for the quick delivery as I'll go nuts waiting any longer.

I won't comment until I see the stuff, but what I want you to say when you get the package and rip it open with beating heart is to:

SLOW DOWN

You've got 1000ah of battery there. Here is a tip: if for some reason you end up having to debate yourself on a wire you can't see, like "did I put the positive lead on?" and end up spending ANY time trying to remember, STOP! Do not try to figure out the answer, and just physically check. As you run around, if you ask yourself this same question again - stop again, even if you feel foolish. Ie, it is not the question itself, but the fact you are spending ANY time debating yourself is the danger.

Recognizing that the start of an internal debate as a safety trigger can take some practice for guys like us who like to figure things out. Here - don't figure it out. Just do the check, even if you have to do it multiple times for the very same thing.

Just sayin' ...

[SunEagle]

I won't comment until I see the stuff, but what I want you to say when you get the package and rip it open with beating heart is to:

SLOW DOWN

You've got 1000ah of battery there. Here is a tip: if for some reason you end up having to debate yourself on a wire you can't see, like "did I put the positive lead on?" and end up spending ANY time trying to remember, STOP! Do not try to figure out the answer, and just physically check. As you run around, if you ask yourself this same question again - stop again, even if you feel foolish. Ie, it is not the question itself, but the fact you are spending ANY time debating yourself is the danger.

Recognizing that the start of an internal debate as a safety trigger can take some practice for guys like us who like to figure things out. Here - don't figure it out. Just do the check, even if you have to do it multiple times for the very same thing.

Just sayin' ...

Measure Twice and cut once is a good safety protocol in carpentry.

For electricity. The circuit isn't dead until it is grounded. (keeps you from getting shocked or worse)

And never try to remember how a circuit it is wired. Make a document and refer to it before you energize it.

[J.P.M.]

I won't comment until I see the stuff, but what I want you to say when you get the package and rip it open with beating heart is to:

SLOW DOWN

You've got 1000ah of battery there. Here is a tip: if for some reason you end up having to debate yourself on a wire you can't see, like "did I put the positive lead on?" and end up spending ANY time trying to remember, STOP! Do not try to figure out the answer, and just physically check. As you run around, if you ask yourself this same question again - stop again, even if you feel foolish. Ie, it is not the question itself, but the fact you are spending ANY time debating yourself is the danger.

Recognizing that the start of an internal debate as a safety trigger can take some practice for guys like us who like to figure things out. Here - don't figure it out. Just do the check, even if you have to do it multiple times for the very same thing.

Just sayin' ...

FWIW: BIG ++1 on that one.

[bungawalbyn]

Thanks for your concern. I'm mindful of the dangers and risks.

I'm not a total noob. This is my third solar system, + I've upgraded one of my neighbours systems. I'm used to handling dangerous items. Tractors, Chainsaws, Power tools, motorbikes, GF and the like. I built and wired my house without drama.

Safety is one of the reasons I stick to 12V. You can still get a reasonable tingle off 12V panels in good sun, and I know DC is more dangerous than AC

I'm bench testing everything before going live.

But of course it's normally the thing you don't see that bites, and that's why I'm here mainly. While not a noob I know I am no expert, so keep the advice coming and hopefully we will avoid any mistakes.

A bit of chilli gives the stew a lift.

[SunEagle]

Thanks for your concern. I'm mindful of the dangers and risks.

I'm not a total noob. This is my third solar system, + I've upgraded one of my neighbours systems. I'm used to handling dangerous items. Tractors, Chainsaws, Power tools, motorbikes, GF and the like. I built and wired my house without drama.

Safety is one of the reasons I stick to 12V. You can still get a reasonable tingle off 12V panels in good sun, and I know DC is more dangerous than AC

I'm bench testing everything before going live.

But of course it's normally the thing you don't see that bites, and that's why I'm here mainly. While not a noob I know I am no expert, so keep the advice coming and hopefully we will avoid any mistakes.

A bit of chilli gives the stew a lift.

Just don't put too much of that Dave's Insanity Hot sauce in the Chili.

[PNjunction]

Thanks for your concern. I'm mindful of the dangers and risks.

I suspected so, but know there are lurkers who may tend to rush into things. Like the general rule about voltages and cabling ...

For every 1000 watts of AC, add 12v. Ie, if you go beyond 1000 watts of load, you should build a 24v system instead and so forth.

PEER REVIEW request: is the statement above basically for lead acid and peukert concerns? Hmmm....

I'm actually excited to see this baby in action, but don't let me push you - take your time...

[bungawalbyn]

OK guys

Here is the board. The relay hanging over the front of the board is a 12v to 240Ac to switch on and off HWS as load dump.

It's a little Prof Ratbaggy but I kind of like that aesthetic.

Oh and don't freak out about the crappy circuit breaker, I have a 400A t class fuse between it and the battery.

All the relays and voltage sensors have been bench tested and are working to plan. I haven't figured out a way to run the BMS and cell meter/alarm through their paces without hooking it up to the battery. Though meter/alarm has been checked pin by pin and does what it should. It will need adjustment when hooked up. Default alarm setting is a little high. (Designed for LiPo's but has suitable range with adjustment.)

I just have to make a cover for the BMS and alarm and a frame to hang it in. Make up the cell to sensor loom and it's ready to install

Inverter cables will be attached to PV side of battery cut offs on the contactor terminals

[bungawalbyn]

How about that, it works.
It charges anyway.
Yet to have it go anywhere near hi or low.
I still have to integrate the HWS dump relay into the house wiring so that part of the controls is inactive.
I only have half my panels hooked up to it at present, It charged at 30 amps at 13.6V for a couple of hours then dropped back as the sun went off the panels.
I'm using them now to power the house, voltage is 13.26 under a light load. All cells identical

There is a bit of a voltage drop between the meters and the battery terminals. Something to think about.