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Author Topic: Benefits of 24v over 12v system?  (Read 9251 times)
Justme
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« Reply #15 on: March 09, 2014, 02:52:31 PM »

one that's been as low as 5.8v is not worth carrying down a mountain  Grin


At 55p per kg scrap value it should be worth carrying down.
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« Reply #16 on: March 09, 2014, 03:56:58 PM »

one that's been as low as 5.8v is not worth carrying down a mountain  Grin


At 55p per kg scrap value it should be worth carrying down.


Depends on the mountain  Wink

Is it really 55p JM, phoned up three places in Inverness last week and was quoted 35p 38p and 40p, I've got around 750kg or about 15 years worth of fecked leisure and car batteries to weigh in. Perhaps a trip to Wales  hysteria

Cheers, Paul
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marcus
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« Reply #17 on: March 09, 2014, 09:24:10 PM »

...If the inverter and charger both shut down automatically on low voltage (about 10.4v) and there are no 12v loads connected how does the battery then discharge further down to 5.8v? I checked my multi meter on my car battery and it was reading ok.
Paul 

batteries don't like going that low (10.4 - I wouldn't go below 12.0), but more importantly, they don't like being left in that state for any length of time. If batteries are to be left then they should be left as close to full charge as possible if you want a long life.

As for recharging the old battery;- I would do so if it still takes a charge. I wouldn't buy a new one until the charging system and low-voltage disconnect are set up properly, and the user knows how to look after batteries - otherwise he might be buying another one next year.
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Justme
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« Reply #18 on: March 10, 2014, 01:40:39 AM »

Just checked & its down to 43p / kg at the min.

Highest last year was 52p in March.
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biff
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« Reply #19 on: March 10, 2014, 09:37:39 AM »

For some reason or other,
                        Some members are giving the impression that it is OK to take batteries down to 12 volts.Well it is not,! That kind of advice should be discouraged because taking batteries down to 12 volts really hammers the poo out of them.They will not live long.Like Paul, I have killed a few batteries in my time and that is exactly how I did it.I thought it was OK to let them sink to 12 volt but soon found out that they had a hell of a job trying to recover.
         Batteries at 12 volts are a bit like a weightlifter under maximum lift with his knees bent unable to get that little extra to get straightened up,Needless to say,@ 10.5 the poor las is on the ground on his back.
 The best thing to do it to keep above 12.4v and increase your bank to achieve that.Clockman is happy at 12.35volt,We will sometimes,the very odd time drop below 123(12 x 10=120volt) under heavy load but soon recover.
     Any battery that is hammered down to 6volts is a lost cause.
                                                                                 Biff
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camillitech
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« Reply #20 on: March 10, 2014, 03:20:26 PM »

For some reason or other,
                        Some members are giving the impression that it is OK to take batteries down to 12 volts.Well it is not,! That kind of advice should be discouraged because taking batteries down to 12 volts really hammers the poo out of them.They will not live long.Like Paul, I have killed a few batteries in my time and that is exactly how I did it.I thought it was OK to let them sink to 12 volt but soon found out that they had a hell of a job trying to recover.
         Batteries at 12 volts are a bit like a weightlifter under maximum lift with his knees bent unable to get that little extra to get straightened up,Needless to say,@ 10.5 the poor las is on the ground on his back.
 The best thing to do it to keep above 12.4v and increase your bank to achieve that.Clockman is happy at 12.35volt,We will sometimes,the very odd time drop below 123(12 x 10=120volt) under heavy load but soon recover.
     Any battery that is hammered down to 6volts is a lost cause.
                                                                                 Biff

Wot he said  genuflect I can never understand why LVD's are set so low, it's as if inverter manufacturers know nothing about batteries  Roll Eyes
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Justme
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« Reply #21 on: March 10, 2014, 05:40:50 PM »



Wot he said  genuflect I can never understand why LVD's are set so low, it's as if inverter manufacturers know nothing about batteries  Roll Eyes


I have spent lots of time on this one.

The problem is that with a big load for a short time your V can fall to sub 11v & the battery is still fine as its real non loaded V is well over 12v & its SOC is still quite high. Yet the same bat with a small load that is on for hours will be stuffed if its gets to 11v as thats its real voltage & the SOC will be low.

As far as I can find out no maker uses the size of the load to actively change the low V disconnect level.
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camillitech
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« Reply #22 on: March 10, 2014, 06:55:54 PM »



Wot he said  genuflect I can never understand why LVD's are set so low, it's as if inverter manufacturers know nothing about batteries  Roll Eyes


I have spent lots of time on this one.

The problem is that with a big load for a short time your V can fall to sub 11v & the battery is still fine as its real non loaded V is well over 12v & its SOC is still quite high. Yet the same bat with a small load that is on for hours will be stuffed if its gets to 11v as thats its real voltage & the SOC will be low.

As far as I can find out no maker uses the size of the load to actively change the low V disconnect level.

The Trace does JM and the values are adjustable,

the default setting is 11v but you can set it as high as you want then adjust the delay to compensate for heavy loads, it's also augmented by the parameters of load sharing or battery charging. There's a whole load of setting that you can play around with in the menu related to load, voltage and time. My voltage can drop as low as 44v (11v) but if there's a huge current flowing it won't cut out or are start the generator to assist until a certain time/amperage has elapsed. Conversely if it's sits at 49.2v for more than two hours it will start the generator, if the generator fails to start and the voltage creeps down slowly it'll disconnect around 48v in theory, but that's never happened.

Having said all that perhaps these facilities are only available on inverter/chargers?? with a generator start function built in.

Cheers, Paul
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Justme
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« Reply #23 on: March 10, 2014, 07:53:54 PM »

Sounds neat. My Victron has all of that apart from the variable low V disconnect.

Its used for the genny start.

I can set it to start on:-

load higher than X for X seconds
Udc lower than X for X seconds
Udc higher than X for X seconds
when not charging for X seconds
when int fan on for X seconds

Also when led alarms are active
temp for X seconds
low bat for X seconds
overload for X seconds
Udc ripple for X seconds


You can set it to go off using the reverse of the above plus set min run times & to stop on bulk charge finished for for X seconds.

With all that you would think they could do variable cut off voltages.
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« Reply #24 on: March 10, 2014, 08:16:31 PM »

when not charging for X seconds
when int fan on for X seconds

Also when led alarms are active
temp for X seconds
low bat for X seconds
overload for X seconds
Udc ripple for X seconds


That's quite a comprehensive selection JM

You can program the Trace to all kind of barmy things like export to the grid when the batteries are full. You can even get it to sell to the grid from the batteries to make use of higher tariffs at different times of the day. Not that it's certified to do any of these things in the UK, but the manual makes interesting bedtime reading. It is also written in plain English, extremely easy to follow and requires no access to a computer or extortionately priced lead like the Victron, SMA or Studer.

Having said that I'd never buy another, their ethics and backup are pants.

Cheers, Paul 
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SMA SI6.OH, 800ah Rolls, 8kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
Justme
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« Reply #25 on: March 10, 2014, 10:07:10 PM »

Those "sell" features sound like the Outback range. Very popular with Americans with large solar arrays.

If I have the money come inverter charger replacement time I will be looking at the SMA range as they also sell a long warranty for a sensible price. To be honest Victrons is a joke at just 12/24 months for the price of the kit.
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30 x 58mm panel 259L TS
1200watts solar 120vdc
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2 x Victron Multiplus II 48/5000/70
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BMV 700
6kva genny
48v 1000ah
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camillitech
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« Reply #26 on: March 10, 2014, 10:24:12 PM »

Those "sell" features sound like the Outback range. Very popular with Americans with large solar arrays.

If I have the money come inverter charger replacement time I will be looking at the SMA range as they also sell a long warranty for a sensible price. To be honest Victrons is a joke at just 12/24 months for the price of the kit.

Aye, JM,

I think semi 'off grid' is also very popular over there, though I believe that's more to do with survivalist mentality and 'preparedness' for the 'new world order' than any wish to save the planet  hysteria

Yup, going SMA myself at the new house, the new SI 60H to start with, as you can put up to 12kw of solar or 6kw of wind via a GTI through it. This 'AC coupling' really fits in well with my diverse 'inputs' and outputs' which are spread over a large area.
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SMA SI6.OH, 800ah Rolls, 8kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
marcus
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« Reply #27 on: March 10, 2014, 11:11:46 PM »

For some reason or other,
                        Some members are giving the impression that it is OK to take batteries down to 12 volts.Well it is not,! That kind of advice should be discouraged because taking batteries down to 12 volts really hammers the poo out of them.They will not live long.Like Paul, I have killed a few batteries in my time and that is exactly how I did it.I thought it was OK to let them sink to 12 volt but soon found out that they had a hell of a job trying to recover.
         Batteries at 12 volts are a bit like a weightlifter under maximum lift with his knees bent unable to get that little extra to get straightened up,Needless to say,@ 10.5 the poor las is on the ground on his back.
 The best thing to do it to keep above 12.4v and increase your bank to achieve that.Clockman is happy at 12.35volt,We will sometimes,the very odd time drop below 123(12 x 10=120volt) under heavy load but soon recover.
     Any battery that is hammered down to 6volts is a lost cause.
                                                                                 Biff

well firstly; as others have pointed out, unless you have a sophisticated LVD that will ignore high-load blips below the setpoint then 12.4 can be impractical.

secondly; I try to avoid 'tripping' my LVD - it's only there as a safety net in case something's gone desperately wrong - so my current battery has never actually got that low in 6 years. Simply setting it at 12.4 and ignoring it 'till it trips is bad battery management IMHO.

Thirdly; I would hesitate to suggest that there is a 'right' value at 12.4v or any other voltage as it depends on your specific battery/setup: My previous set of batteries were some old, much abused Clhoride 'Motive-power' traction batteries which were down to ~25% of their rated capacity but still working. They had fully-charged 'rest' voltages between 11.97v and 12.20v, so setting my LVD at 12.4v for them would have been plain stupid.

I for one was not suggesting that it was OK to take a battery down to 12v, but merely suggesting that 12v would be a better LVD setting than 10.4v for a typical battery.
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greenhouseparos
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« Reply #28 on: March 19, 2014, 10:23:51 AM »

Battery is finished.
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