Club 80-90 Forums

Ok so this has got me thinking about how leisure batteries discharge. Do they hold their voltage up relatively high (eg in the region of 12v given some of the units linked to on here cut off at 12.1v!) as they run down or does the voltage start to drop off pretty much as soon as charge is removed and load applied? I thought the whole point was they could withstand more frequent and deeper cycling than 'starter' batteries (fully accepting that going to less than 50% or even 60% is not advisable). I guess what I want to avoid is having the auto switch kill my lights, water pump, music etc after just a few hours camping when in reality I could safely operate those items for a lot longer without hurting the leisure battery... /heads off to google 'battery discharge graph'...

Ok so some interesting info here http://www.leisurebatteries.net" onclick="window.open(this.href);return false;

Probably very basic for a lot of the folk on here but very useful for me. Looks like 12.1v or even a bit higher is a good cut off. Going to order one of the 12.1v cut off units and see how I get on!

Will report back....!

OK, so I got this Low Voltage Disconnect off of Fleabay for £19.99p:

http://www.ebay.co.uk/itm/251395005819? ... 1497.l2649

Decided to give it bench test before I took the time fitting it, and made this discovery.

Before the disconnect kicks in it works 100% fine:



All was looking good as I dropped the voltage, the cut off voltage seems great (I've measured it at approx 12.1 Vdc), and the first stage alarm sounds for 30 seconds followed by the second stage alarm which sounds for 10 seconds (Just as described in the instructions)

However 10 seconds after the second stage alarm the unit does not fully disconnect the loads ? Instead it just drops the output voltage to approx 9.80 Vdc ?



Now am I missing something, or is this just not working at all ?????

Surely I should see 0v on the Output after the disconnect voltage has been exceeded ? Even at 10v (Well below the disconnect) it still has 9.88Vdc on the Output

Ghost is our man on this, but one possibility is that that 9.8V won't carry any load. Have you tried running a bulb from it for instance? I have an auxiliary fusebox which lights up an LED next to a blown fuse, and this has the side effect that my multimeter still detects a voltage on the circuit even when the fuse has blown. The tiny current through the LED isn't enough to light a test bulb though. Maybe your LVD is passing a tiny current to the output via a diode?

Can't think why, apart from this sentence in that ebay advert: "Alerts you when you have used a certain amount of battery power, (lights, radio, heaters etc.), inside your car so that you can shut off the power before your battery goes flat."

Chris is right, your meter is so sensitive it is reading what is known as "residual" voltage/current, as mentioned, leaking through the circuit (a normal thing to happen). As said, if you put a load on it, the voltage will drop to zero (or very very close).

Try this = connect your meter's black lead to the -ve of a 12 volt battery. Put your finger on the +ve terminal whilst holding the bare end of the meters red lead in your other hand (no, you won't get a shock). You will note that although the red lead is not connected to the battery, you will still see it read ~12V. The voltage is going through you, but it wouldn't be enough current to light even the tiniest bulb, but it is enough to get a reading on your meter. Similar circumstance to your LVD.

Here endeth today's lesson and I am going to the village pub for an early doors (it's darn hot here) pint (or 3) of Salamander Ale

Cheers Ghost & CJH, full marks to you both

Volts are still on the output, but no current



Managed to get the output voltage down to almost nothing by loading the output with a resistor after I took this photo.

Enjoy your well earned Salamander Ale (Which I just googled, and looks very nice)

Heads up, I just found this one HERE on Ebay. It looks good what with the LCD meter etc. You need to add a relay, but that is dead easy.

ghost123uk wrote:Heads up, I just found this one HERE on Ebay. It looks good what with the LCD meter etc. You need to add a relay, but that is dead easy.

Hi Ghost

I'm going to try to fit one of these. Sorry to be a pain, but could you let me have a few sentences of instruction. Eg what wires connect to what terminals, what relay to fit, where to mount it etc etc.

Much appreciated.

Thanks

Ian

I'm a little confused about safe battery voltage. It seems the general concensius is not to run wet batteries below 50% or 12V. Is this measurement taken when underload or at rest? I generally find there is about 0.3V between these two measurements .

isaune wrote:

ghost123uk wrote:Heads up, I just found this one HERE on Ebay. It looks good what with the LCD meter etc. You need to add a relay, but that is dead easy.

Hi Ghost

I'm going to try to fit one of these. Sorry to be a pain, but could you let me have a few sentences of instruction. Eg what wires connect to what terminals, what relay to fit, where to mount it etc etc.

Much appreciated.

Thanks

Ian

Hi Ian, I know the REUK guys are not very good at clear and concise instructions. I offered to re-write the ones for their other one, but they didn't seem interested. I have not had one of that version in my hands (yet) and was going to say "you will need to post up a pic or summat of the instructions, or at least what it says to do" then I would have been able to work it out.

However, I found this on their site that makes it pretty clear



I like the way, in that diagram, the required thickness ratio of the wires is clearly indicated


More info re programming etc HERE

The relay needed is any general purpose relay rated at say around 10/15/20 Amps, depending on how much "gear" you are using on your leisure circuits. Most leisure circuits are nearer to 5 amps usage ( unless you have a Diesel Eber heater, in which case special needs apply)

ninja.turtle007 wrote:I'm a little confused about safe battery voltage. It seems the general concensius is not to run wet batteries below 50% or 12V. Is this measurement taken when underload or at rest? I generally find there is about 0.3V between these two measurements .

Under load, though in reality it doesn't make a lot of difference in our T25 applications as the load is usually pretty small and so does not affect the voltage drop at the battery. If you were pulling say 25 Amps, then yes the voltage at the terminals may read a volt down under load, compared to no load (due to summat called the batteries internal resistance) but as in your case you only see 0.3V difference.

However, yes, the answer to your question is, measure under load and at the battery terminals.

(note though a stored battery is not under load, the same rules apply re not leaving them long enough, without charging, to allow them to drop to less than 12V)

Thanks for the info.

Why are the LVD's set to 11.5v? Surely the battery would be damaged at the voltage?

Cheers Ghost for the advice a few posts ago - that's next weekend's project sorted!!

Showing my ignorance of all things alchemy and sparks here, but could you tell me if i've labled the correct terminal numbers to wire in a standard 4 post relay



Would like to know I've got it correct as i dont really want to create a bonfire just yet!

That is correct