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Post Info TOPIC: 240 to 12v transformer ?


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240 to 12v transformer ?


Is anyone using transformer to run 12v when batteries are low ? †It seems the chargers out there are not rated high enough or very expensive ?? †I have 40 amp charger but supplies 18 to 22 amps on 300 AH battery pack . I assume its the regulator reducing charge ? †seems these regs are designed for single car batteries ? The solar charges them in morning by 10am on a nice day . Often wander if transformer connected to solar reg would do a better job ?? Or is it just the battery cycle and Im worrying, thinking of it too much ?? †



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Hi AK,

I've got a transformer in my MH, I rewired it with a couple of relays to ensure it disconnects from the batteries when in use.† I did this because it cooked my batteries when we where in a shed for 3 months, when we replaced the motor 2 years ago. When we went into the shed the batteries were fully charged and we were running everything 12v off the transformer, problem was it was feeding a constant unregulated charge in to the batteries which in turn fried them.

Considering solar panels feed in to the solar controller at around 18 volts, I don't think the transformer could be used connected to the solar controller because it would only be outputting in the 12 volt range. Unless you can tweak the output to something that the solar controller is expecting to receive.† That said, if you have an MTTP controller it might work but I have my doubts, I would think a Battery Charger would be a better option.

Regards Steve.



-- Edited by madaboutled on Sunday 25th of February 2018 01:09:20 PM

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Steve, Di & Ziggy We named our Motorhome "Roadworx" because on the road works "Home for Summer"
Ford Transit with 302 Windsor V8 conversion, C4 Auto, 9 Inch Ford Diff All Lighting L.E.D., 260 Amp/h AGM, 530 Watt Solar + Kipor Backup Gen.



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Yes that‚s what I‚m thinking 16 to 18v transformer . Let the solar reg to the regulating . Plus enough amps to drive anything with 240 . Something that charges quick as per solar in day time good sun !!

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Maybe something like this....

https://www.ebay.com.au/itm/Variable-Power-Supply-Switch-Mode-4-15V-60A-13-8V-12V-Ham-Radio-Car-motor-240V/263437746925?epid=625786113&hash=item3d561d02ed:g:maYAAOSwCkZZVKg3

Looking at the specs something a bit bigger that can be run continuously might be the go.

Steve.



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Steve, Di & Ziggy We named our Motorhome "Roadworx" because on the road works "Home for Summer"
Ford Transit with 302 Windsor V8 conversion, C4 Auto, 9 Inch Ford Diff All Lighting L.E.D., 260 Amp/h AGM, 530 Watt Solar + Kipor Backup Gen.



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Shocking misuse of terminology !!!
Pun intended
Any one with a basic understanding of electrics should know that a†"Transformer." is purely an AC devise

Connect one to DC & the only thing that limits the current is the winding resistance[Ohmic Resistance]
But on AC ,the iron core increases the apparent resistance [IMPEDANCE ]greatly & that is referred to as inductive IMPEDANCE.

The simple term for DC devices that change voltage is '" DC CONVERTER"

They are now usually electronic† {DC/DC Chargers} but use to be motor generator† sets

Ones that changed DC to AC† where called "rotary inverters"

The today's " INVERTERS "are the electronic version

The "Thing " that charges your battery from mains power is a BATTERY CHARGER often referred to as a "MAINS CHARGER"

IT "TRANSFORM ", by rectification , the AC [alternating current] to† DC {Direct Current ]†

A DC >DC charger cannot† be used in series with a solar panel and solar regulator .

Some are designed to have† solar panel/s connected DIRECTLY to them .NO solar regulator, as that function is performed within such DC /DC chargers



-- Edited by oldtrack123 on Tuesday 27th of February 2018 01:24:18 PM

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Aus-Kiwi wrote:

Is anyone using transformer to run 12v when batteries are low ? †It seems the chargers out there are not rated high enough or very expensive ?? †I have 40 amp charger but supplies 18 to 22 amps on 300 AH battery pack . I assume its the regulator reducing charge ? †seems these regs are designed for single car batteries ? The solar charges them in morning by 10am on a nice day . Often wander if transformer connected to solar reg would do a better job ?? Or is it just the battery cycle and Im worrying, thinking of it too much ?? †


It is the battery "Impedance" that is limiting the charge

Battery "Impedance " [resistance to current flow]& is a combination of the batteries internal "Ohmic "resistance PLUS the actual battery voltage @ that point.in time. Any voltage drop in the battery charger† DC leads & connections can limit current flow

The charger sees that as part of the battery impedance

Check for voltage drop in DC† leads & connections while under load [charging]

The total should not exceed 0.25V, the lower the better!

You cannot / should not connect a "Transformer" to any solar panel or solar regulator or even to a battery[any DC source]

The solar panel & regulator will see that as a dead short [virtually no ohmic resistance]† the output of the transformer will be ZERO



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madaboutled wrote:

Maybe something like this....

https://www.ebay.com.au/itm/Variable-Power-Supply-Switch-Mode-4-15V-60A-13-8V-12V-Ham-Radio-Car-motor-240V/263437746925?epid=625786113&hash=item3d561d02ed:g:maYAAOSwCkZZVKg3

Looking at the specs something a bit bigger that can be run continuously might be the go.

Steve.


†THAT is a power supply, definitely not suitable for battery charging as it does not / could not regulate the battery SOC

Ok for what it is designed for ,Regulating the BATTERY output voltage to maintain a constant preselected voltage @ the device's output terminals



-- Edited by oldtrack123 on Tuesday 27th of February 2018 01:50:05 PM

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Connect between reg and diode on solar . Mainly thinking at night or bad overcast days . One of two things to charge batteries quick to say ?? 12.6 volts or supply enough to supply feed. The trouble with MOST battery chargers is they drop the amps . The load is confusing the reg ?? Of course this is for short term charge . Not to be used full time !!

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oldtrack123 wrote:
madaboutled wrote:

Maybe something like this....

https://www.ebay.com.au/itm/Variable-Power-Supply-Switch-Mode-4-15V-60A-13-8V-12V-Ham-Radio-Car-motor-240V/263437746925?epid=625786113&hash=item3d561d02ed:g:maYAAOSwCkZZVKg3

Looking at the specs something a bit bigger that can be run continuously might be the go.

Steve.


†THAT is a power supply, definitely not suitable for battery charging as it does not / could not regulate the battery SOC

Ok for what it is designed for ,Regulating the BATTERY output voltage to maintain a constant preselected voltage @ the device's output terminals



-- Edited by oldtrack123 on Tuesday 27th of February 2018 01:50:05 PM


†No kidding.... EDIT deleted following comments



-- Edited by madaboutled on Tuesday 27th of February 2018 03:55:13 PM

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Steve, Di & Ziggy We named our Motorhome "Roadworx" because on the road works "Home for Summer"
Ford Transit with 302 Windsor V8 conversion, C4 Auto, 9 Inch Ford Diff All Lighting L.E.D., 260 Amp/h AGM, 530 Watt Solar + Kipor Backup Gen.



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Aus-Kiwi wrote:

Is anyone using transformer to run 12v when batteries are low ? †It seems the chargers out there are not rated high enough or very expensive ?? †I have 40 amp charger but supplies 18 to 22 amps on 300 AH battery pack . I assume its the regulator reducing charge ? †seems these regs are designed for single car batteries ? The solar charges them in morning by 10am on a nice day . Often wander if transformer connected to solar reg would do a better job ?? Or is it just the battery cycle and Im worrying, thinking of it too much ?? †


The battery acceptance rate is what is causing the charge reduction because the regulator within the charger is trying to limit the charge voltage. If you force the charge voltage higher the current will increase, the battery will have the electrolyte boiling both from heat and electrolysis bubbles of hydrogen and oxygen and if it can't vent the gas the case will start to bulge. If it does vent the battery compartment is now so full of the perfect mix of gases to blow the thing to bits so you sure don't want a spark in there.

The end†result will be a stuffed battery with buckled plates. Setting the charger to equalise mode will do just what you are trying to do and have the same results on all but flooded cell batteries.

If you don't want the battery internal resistance to cause the rise in charging voltage that is causing the charger to slow down, you need a better chemistry battery .... Maybe you are starting to understand one of the reasons†people are changing to this better chemistry battery, this is the faster charging part, just one of the many benefits winkbiggrin

T1 Terry†††

EDIT: By the way, you are not seeing fully charged from the solar by 10am, you are seeing the end of the battery acceptance of that charging rate and that is not even close to fully charged. If the charge rate is low then you might have reached 80% SOC, but generally more like 70% SOC and the remainder needs to be added at a much reduced charge rate, that is what you can see your mains charger doing.†



-- Edited by T1 Terry on Tuesday 27th of February 2018 04:20:46 PM

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I guess that could work as direct 12v supply ? Taking load off storage batteries. ? I have inverter / charger built into motorhome . It seems the 60amp charger section is not working. From memory a Mastervolt . The DC side doesn‚t get used much or more the point . Over 4 years I have hardly known the DC charger doesnt work .

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Aus-Kiwi wrote:

I guess that could work as direct 12v supply ? Taking load off storage batteries. ? I have inverter / charger built into motorhome . It seems the 60amp charger section is not working. From memory a Mastervolt . The DC side doesn‚t get used much or more the point . Over 4 years I have hardly known the DC charger doesnt work .


Hi Aus-Kiwi,smile

I had a Mastervolt unit in a previous MH. It was not charging correctly and I had it fixed. A really good bit of kit and worth the effort to fix it, 3 stage charging with temp compensation. The electronics tech was impressed with the quality of the older unit.† I believe the previous owner had connected the batteries back the front which is specifically warned against and it had blown a couple of items. It worked well then as a DC house supply and heavy duty charger and a seperate trickle to the truck batteries too. Better built than newer units you commonly find.

Jaahn† † †



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www.ebay.com.au/itm/Variable-Power-Supply-Switch-Mode-4-15V-60A-13-8V-12V-Ham-Radio-Car-motor-240V/263437746925 I use a similar powersuply for charging my deep cycle battery in my van when solar is not keeping up. Been using it for 3 years now & never had any problems at all. But I do have a large diode in series with one lead to stop back flow of a bout 250Ma when switched off, And its on a decent heat sink. I just alow half a volt increase to over come voltage drop across the diode.



-- Edited by DeBe on Wednesday 28th of February 2018 04:00:09 PM

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Yes battery voltage is up over 13v by 10am ., what I am seeking to fix is the charging system at night even with charger on . It hardly charges batteries . The built in reg I guess is for a single 12v battery ? Where I have 3 X 120 AH batteries . The load which is sat box, TV . LED lights , maybe little 12v fan ? Another LED TV . . The charging is mainly an issue on overcast days . Yes I will get the Mastervolt fixed ! Yes it has temp sensor between batteries . Hope I explained this correct . At no point am I trying to charge without a regulator !! Was looking at transformer to imitate solar ., either through 240 or gene .. The Mastervolt i would guess has never worked ? Mainly because I have hooked up to 240 and batteries went low on overcast day.

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Aus-Kiwi wrote:

Yes battery voltage is up over 13v by 10am ., what I am seeking to fix is the charging system at night even with charger on . It hardly charges batteries . The built in reg I guess is for a single 12v battery ? Where I have 3 X 120 AH batteries . The load which is sat box, TV . LED lights , maybe little 12v fan ? Another LED TV . . The charging is mainly an issue on overcast days . Yes I will get the Mastervolt fixed ! Yes it has temp sensor between batteries . Hope I explained this correct . At no point am I trying to charge without a regulator !! Was looking at transformer to imitate solar ., either through 240 or gene .. The Mastervolt i would guess has never worked ? Mainly because I have hooked up to 240 and batteries went low on overcast day.


†The voltage for lead acid batteries of any type must be over 14.4v before the 70% SOC min can be deemed to have been reached, fully charged is up to 24 hrs after this point but the last 2% can take more than 12 hrs for the battery to absorb.

A bit of information to help with the proper understanding of a fully charged lead acid battery:

That 14.4v is only an indication on non sulphated batteries, the greater the level of sulphation the quicker the battery voltage will climb when charging and the faster it will fall when charging stops and a load is applied. Genuine state of charge can only be determined by applying a 5 amp load per 100Ah advertised capacity and reading the voltage after 5 mins so the surface charge is removed. If it still reads 12.8v then the battery is truly fully charged and has the capacity advertised, 12.6v is roughly 80% SOC, 12v or less is 50% SOC or less and the battery has passed its use by date.

T1 Terry



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Yes. I‚m just trying to prevent flat batteries or too much drain keeping the amber light on . At times it goes into red . From memory 12.5 v which I am trying to prevent go to . If I have 240 or able to start QUIET generator. Not so bad now we have fitted a low voltage sensitive cut out relay for motor batteries . Being diesel, auto .. Maybe I am looking into it too much or worrying over nothing !! No point trying to pioneer when there is a system there !! Just need to repair or replace it !

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I suggest this from Terry ,hits the nail on the head

"That 14.4v is only an indication on non sulphated batteries, the greater the level of sulphation the quicker the battery voltage will climb when charging and the faster it will fall when charging stops and a load is applied. Genuine state of charge can only be determined by applying a 5 amp load per 100Ah advertised capacity and reading the voltage after 5 mins so the surface charge is removed. If it still reads 12.8v then the battery is truly fully charged and has the capacity advertised, 12.6v is roughly 80% SOC, 12v or less is 50% SOC or less and the battery has passed its use by date.

T1 Terry"


You have at least one of three possible problems
[a]

Excess voltage drop between the regulator & the Battery ,very easy to check.

The battery has lost storage capacity
Due to :
[1}
Loss of ACTIVE material on the plates, irrepairable & caused by :
Vibration


Overcharging†

Excessive charge rates

Heavy discharge rates

[2]
Sulphation
Usually caused by leaving the battery in a discharged state for a long period.
If not set too hard ,may be recovered to some extent by using a charger with desuphate mode ,but very unlikely to ever regain full rated capacity as the surge currents used in desuphation mode tends to blast the lead sulphate off the surface rather than reconvert it



-- Edited by oldtrack123 on Thursday 1st of March 2018 06:32:34 PM

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