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Author Topic: Multi Battery Monitor, LVD, Display & Data Storage.  (Read 10657 times)
Andy the Inverter Man
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« Reply #15 on: January 02, 2012, 07:24:54 PM »

Hi Andy,
Its true i am afraid, there is a difference between Inverter UPS battery systems than Off Grid battery banks.

As i originally said somewhere in my posts, when i allowed the UPS LVD to function and auto shutdown at about 42v for a couple of months, i very quickly lost 2 of my 12v 110ah battery's, with 2 others damaged, (would not hold voltage). To me caring for the expensive batteries is a must as i need them to last as long as possible and at the same time give their best.

Listening to the wise old sages on this forum who are actually using batteries Off Grid day in day out, made me understand real operating usages with batteries. And it was seemed that 12.2v to 12.3v LVD was a good way to care for operational batteries without causing them excessive deterioration.

Again, i will report back on how this 12.2v LVD works with my particular system, but with my observations to date, the last 18 months my 20 12v 110ah batteries have behaved. But the new circuit should give me more accurate data.

Also recharge times are not consistant like a UPS when it reverts back to mains supply, some times my batts get a quick charge if its sunny and its blowing a good wind, sometimes becalmed it can take days just trickle charging from overcast solar PV.  Again, the new circuit data will give me info on the most efficient charging rates.

Sustainability matters to me so the care and quality of my equipment and its longevity is very very important.

Unfortunately as i get older and wiser, i realise that a lot of data sheets issued by manufacturers is not allways telling realistic tales.. Roll Eyes

Hi Leslie,
I'm afraid I have been very much misunderstood in my previous post.
I think part of the reason is the incorrect use of terminology.
And perhaps you missed my caveat about batts in good condition?  (by good condition I mean the batt is new or virtually new, the quality of the manufacture of the batt, etc)

I'm an electronics engineer.  Bachelor of engineering B.Eng. 2:1
In electronics when we say 'irreparable damage' we mean something has had a 'sudden and total failure'.  E.G. a transistor blowing up.
What you described with 2 of your batts failing within a couple of months is what I would call wear & tear.
The rate of wear & tear can vary considerably.
A brand new quality battery should be able to withstand 100% discharge (e.g. down to 10.5Vdc) a couple of hundred times.
But a used battery can be very different.  I've had used batts that deteriorated quite a lot from a few 100% discharges/charges (cycles).  But equally I've had used batts that have been fine with 100% cycles.
And there are other factors to take in to account.
E.G. the size of the load.  I suspect the manufacturer's use a small load when testing the number of 100% cycles. Probably the 20 hour rate.
Also the charge rate, the ambient temperature, etc are all factors when cycling the batts.

In my previous post I quoted number of cycles vs depth of discharge.
Effectively I was saying for cyclic use, a lesser depth of discharge gives disproportionately more cycles.
From the example in my previous post.... 100% depth of discharge 250 cycles and 30% depth of discharge 1200 cycles.
If it was proportionate then at 30% depth discharge, you should get 100/30 x 250=833 cycles.  But you actually get 1200 cycles.
But it is disproportionate, so I was agreeing with you that it is better to do lesser depth of discharge in cyclic applications.  Hence my saying I've been misunderstood.  Smiley

Also your sample size is very small.
You can have poor batches of batteries.  Even brand new ones direct from the manufacturers.
I bought a batch of brand new batts of a well known make and they were terrible.  Less than half their supposed run time.  I had bought this make before many times and they were fine.  Just got a bad batch on that occasion.

To Summarise....
As we've said a lesser discharge is better.  But a cut off of 12.2Vdc is very high.  You must have a very small load relative to your battery bank?
Stop charging the batts when fully charged.  Constant trickle charging will cause wear & tear to the batts.
Keep an eye on ambient temperature.  You should lower your charge voltage as temp goes up.
Measure the voltage drop across your battery cables at full load.  I.E. measure it to make sure your cables are thick enough.
The best batts to use (IMHO) are the ones that have terminals accessible for each cell.  E.G. Yuasa do a 6V one with 6 terminals.  Over time it is nearly always the middle cell that fails.  But it can be bypassed as all terminals are accessible.
Most 12v battery failures are a single cell failure.  The other 5 cells are normally fine but can't be accessed.

Regards
Andy the UPS, Inverter & Battery Man
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pb
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« Reply #16 on: January 03, 2012, 02:43:18 PM »

Did you consider using something like a chain of LTC6803s instead of your big stack of reed relays?  That would avoid the need to bring the actual battery voltages onto the CPU and, in turn, would make it rather easier to measure the load current since you could now just use a shunt in the battery negative lead rather than a Hall sensor or CT.
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ericw
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« Reply #17 on: January 03, 2012, 05:41:03 PM »

Certainly an interesting chip which I wasn't aware existed and it would have made the design much easier.
Looking at the 48v battery application note it does seem to need quite a lot of (cheap) components but with 8 banks of batteries the cost would be starting to rise.
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clockmanFR
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« Reply #18 on: January 03, 2012, 06:49:32 PM »

Looks like each LTC6803s is about 15 each. Measures up to 12 individual cells at max 5v each.
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« Reply #19 on: January 04, 2012, 09:42:45 PM »

Well i managed to get through the Arduino tutorial and do some basic programming and get it to talk.

Now that Christmas is moved on, i can now get this circuit working?

Tested the circuit board and all the bits and all seem to function now, but had to add a jumper wire on the 0v feed as i had missed it, and only found one dry solder joint, (actually i had missed the joint when soldering up).

So now await bench testing and installing the software and formating the SD card.
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clockmanFR
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« Reply #20 on: January 04, 2012, 10:21:15 PM »

Hi andy, cheers for the enlightenment.

Yes i would like brand new 2v individual batteries, plus forklift to move them, but sadly my pockets are not very deep at present, perhaps one day?.

On my 2 gel batts (actually felt pads between the plates) that failed, when i took the top off, it was the first cell and the last cell that had failed and both had buckled plates that had shorted out on the opposing top plate grid connection, as a i said in a previous post there seems to be only about 5 to 8mm clearance during normal working conditions.

Regards cyclic conditions even at 1200 cycles that's only 3 and a bit years and accordingly the batteries are stuffed, so hence me setting a high LVD voltage at this time, however it is very possible to re set the LVD lower depending on the load.

In general my observations,  800amph batts, with turbines and PV off after a full charage the batteries settle at 52.6v after 5 days.
Switch the 3.7kw inverter on and a 1.3kw load, with battery's at float mode 54v, voltage drops in 5 minutes to 52v approx and gently falls to 51v over the next hour. The voltage then holds at 51v for many hours and then starts to drop, at 48.2v i shut the inverter down. However during this time the turbines and PV are still kicking power in, so the rate of power draw from the 1.3kw load is at present unknown. Hence the circuit and the data storage system.

Once the charge rate has dropped to float mode i normally switch on the inverter and use the power. So its unlikely the batteries will get overcharged, and i am more concerned that they are not getting enough charge!  Shocked

Regards cables i use 16mm/2 as standard but would like to use 25mm/2 but then it becomes a fight with a snake with rigermortice, (they tell me).
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Andy the Inverter Man
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« Reply #21 on: January 06, 2012, 04:56:10 PM »

Hi andy, cheers for the enlightenment.

Yes i would like brand new 2v individual batteries, plus forklift to move them, but sadly my pockets are not very deep at present, perhaps one day?.

On my 2 gel batts (actually felt pads between the plates) that failed, when i took the top off, it was the first cell and the last cell that had failed and both had buckled plates that had shorted out on the opposing top plate grid connection, as a i said in a previous post there seems to be only about 5 to 8mm clearance during normal working conditions.

Regards cyclic conditions even at 1200 cycles that's only 3 and a bit years and accordingly the batteries are stuffed, so hence me setting a high LVD voltage at this time, however it is very possible to re set the LVD lower depending on the load.

In general my observations,  800amph batts, with turbines and PV off after a full charage the batteries settle at 52.6v after 5 days.
Switch the 3.7kw inverter on and a 1.3kw load, with battery's at float mode 54v, voltage drops in 5 minutes to 52v approx and gently falls to 51v over the next hour. The voltage then holds at 51v for many hours and then starts to drop, at 48.2v i shut the inverter down. However during this time the turbines and PV are still kicking power in, so the rate of power draw from the 1.3kw load is at present unknown. Hence the circuit and the data storage system.

Once the charge rate has dropped to float mode i normally switch on the inverter and use the power. So its unlikely the batteries will get overcharged, and i am more concerned that they are not getting enough charge!  Shocked

Regards cables i use 16mm/2 as standard but would like to use 25mm/2 but then it becomes a fight with a snake with rigermortice, (they tell me).

Hi Leslie,
A few months ago I was offered a load of 2 to 3 year old 6V 160Ah Yuasa Endurance batts.  I didn't take them due to the weight and price being asked.  And they are difficult to sell on ebay.
But if I know you and others on here would want them then maybe next time I could get them.  Are you interested?

A fully charged SLA AGM battery should settle at 13 to 13.1Vdc.  So 4 in series would be 52.4Vdc  So looks like you've got some good batts there.
So basically a very large battery bank and a very low load.  Wink

Better if you could stop charging the batts when fully charged.  Some UPSs do that, some don't.

AWG wire gauge here....
http://en.wikipedia.org/wiki/American_wire_gauge
16mm2 is about 5AWG which has a resistance of 1mOhm per metre. 
So your UPS (I mean inverter) at full load would draw 3700 watts from a 48Vdc battery bank.  Which is 77amps.  Round up to 80 amps to allow for inefficiencies.
So at full load you would drop 80mVolts per metre of cable.  May not sound a lot but over a few meters of positive cable and likewise negative cable it can start to add up.
So you had 3 metres of positive cable including what is inside the UPS and the same on the negative side.  So 6 metres in all.  Then almost half a volt dropped at 80 amps.  Or to put it another way 40 watts worth!
But then you probably never run at full load.  Smiley

I used 2x 8AWG which comes to the same resistance.
Expensive heavy duty cable, isn't it?

I was thinking of doing a deal on 3kva inverters/UPSs.  Buy 2 get 3rd one free.  Would anyone be interested?
230 each with cables and conversion done ready to use.

Regards
Andy the UPS, Inverter & Battery Man
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biff
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« Reply #22 on: January 06, 2012, 06:30:58 PM »

hi andy,
        i would certainly be intrested in the yousa 6volt 150ahs but would need a pallet of 20 at least, i would normally get about 36 x 100ah yousa on a pallet(40kgs each) but these might be a lot heavier,
                                                        biff
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« Reply #23 on: January 06, 2012, 06:33:09 PM »

Hi Andy, thanks for your information. Especially that i have 40 watts in losses, but then its rare that i run at full load, however the last 2 days the inverter was running at 3kw because the turbines were kicking out serious amounts of power.

Regards Batteries, i had been getting, (chap retired) my Gel jobs 4 off 110ah (a string) for 160 - 180 range. My New deep cycle industrial jobs for a string best price has been 360.

So would defiantly take 8 off your 6v 160ah batteries, if the price was right, no rush, have friends that will store and i can allways pick them up or send the Mrs, me or her travel up the Uk from Dover to Newark, Notts about once a month. Ebadger, (he's off Grid) is just down the road so together we may be able to arrange something. 

I get my 16mm/2 and other armoured cables from e.bay some one somewhere allways has offcuts and the price is about scrap value, one just has to wait. And considering i have 2 PV trackers to install and another wind turbine to put up, good cable is allways handy.
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Andy the Inverter Man
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« Reply #24 on: January 07, 2012, 01:03:32 PM »

Hi Andy, thanks for your information. Especially that i have 40 watts in losses, but then its rare that i run at full load, however the last 2 days the inverter was running at 3kw because the turbines were kicking out serious amounts of power.

Regards Batteries, i had been getting, (chap retired) my Gel jobs 4 off 110ah (a string) for 160 - 180 range. My New deep cycle industrial jobs for a string best price has been 360.

So would defiantly take 8 off your 6v 160ah batteries, if the price was right, no rush, have friends that will store and i can allways pick them up or send the Mrs, me or her travel up the Uk from Dover to Newark, Notts about once a month. Ebadger, (he's off Grid) is just down the road so together we may be able to arrange something.

I get my 16mm/2 and other armoured cables from e.bay some one somewhere allways has offcuts and the price is about scrap value, one just has to wait. And considering i have 2 PV trackers to install and another wind turbine to put up, good cable is allways handy.

My figures were example figures.
At full load-ish, measure the voltage drop across either the positive lead or neg lead.  Need a good multi-meter like a Fluke.  See what it measures.
Plus if you have a fuse in series with the batts, measure across that too.  You might be surprised how much you drop across the fuse!

What make / model are your new deep cycle batts?
90 per New batt sounds too cheap.  What's the date code?
You can call any lead acid battery deep cycle.  Inc leisure batts!  Sad
And I doubt they are really industrial grade.
In electronics you have 3 grades - commercial, industrial and military.
For example, take PSUs.  The PSU in a PC is commercial and would cost about 20.  An industrial PSU would be more like 200.  I don't what a military spec PSU would be, but probably 10 times as much again.

Google, shopping Yuasa EN160-6 batts comes up with 220 to 340 depending on which model of EN160-6.
But I have missed the boat on the last lot.  But if I get offered them again and they are not too old I can offer them on here.
For Yuasa EN160-6 that are no more than 2 to 3 years use, I would be looking for about 50 each.
I would have to pay a lot for them as scrap lead prices are sky high.  Plus I've got to drive a long way to get them.

Regards
Andy
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clockmanFR
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« Reply #25 on: January 07, 2012, 06:06:07 PM »

Andy, count me in, 8 definitely for 50 each.

No fuses, (can't risk the turbines not being connected), except the isolator and DC MCB 100amp for the inverter and the DC MCBs in each Turbine controll box.

Regards my 12v new jobs, no idea nothing written on them, but weight wise each is about 30Kg. My gels ones are 32kg. I go on weight.
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Andy the Inverter Man
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« Reply #26 on: January 07, 2012, 09:34:19 PM »

Andy, count me in, 8 definitely for 50 each.

No fuses, (can't risk the turbines not being connected), except the isolator and DC MCB 100amp for the inverter and the DC MCBs in each Turbine controll box.

Regards my 12v new jobs, no idea nothing written on them, but weight wise each is about 30Kg. My gels ones are 32kg. I go on weight.

It does of course depend whether I get offered any more.  And what age they are.

Do you not have a fuse between a couple of the batts?
What happens if your batt string gets shorted out?    thousands of amps!  cable melting!  fire!  batts knackered!  Smiley

Looking at Yuasa AGM data sheets....
EN160-6   6v 160Ah weighs 35Kgs.  Think of it as a 12v 80Ah.
And NPL100-12   12v 100Ah weighs 39Kgs

Stick your batts on your bathroom scales.  See what they weigh. 

PS: No one interested in my buy 2 get 3rd one free offer on inverters(UPSs)?

Regards
Andy the UPS, Inverter & Battery Man
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« Reply #27 on: January 07, 2012, 10:18:47 PM »


Stick your batts on your bathroom scales.  See what they weigh. 



If I do that I might bust the scales. The book weight on the single battery I am using is 1200kg & the back up (the one I was using but keep on stand by fully charged till I get more charging power & join them together) comes in at 570kg.
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Andy the Inverter Man
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« Reply #28 on: January 08, 2012, 10:09:24 AM »

If I do that I might bust the scales. The book weight on the single battery I am using is 1200kg & the back up (the one I was using but keep on stand by fully charged till I get more charging power & join them together) comes in at 570kg.

Have you got a link to your battery?
Is it actually a number of 2Vdc cells linked together?

Andy
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« Reply #29 on: January 08, 2012, 12:40:35 PM »

With LVD give yourself an over-ride option. My 12 year old 24V/400Ah Yuasu NPL AGM pack was down to 24.8V after 10 days/200Ah use in cloudy/rain.  I looked at the sheets which showed I could go down to 21V.  It's not ideal, but it's better than a slap from the missus when she misses  a TV program :-)  Whether it would cause permanent damage, the manufacturer thinks not.  I tend to agree.  When I got these batteries at 9 YO, they were at about 6V instead of say 11-12, after a year+ of storage (and a standby life since new) If you aggressively cut the inverter off at say 50V, it could also be dangerous (keep a torch with you at all times?)

To monitor each battery, you could use a simple potential divider array into the ADC?  If you havent got enough inputs, use a couple CMOS  switches like the  the 4066. For the current, measure across the fuse using the ADC and 0.1% resistors to drop the voltage down and subtract in software.  If you've got 12 bits and a 2.5V reference that'll give 0.6uV resolution (and not too much switching noise)   I use a hall effect device robbed from an old inverter.  Does the inverter have a serial interface you could get the info from?
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