Amps. Silly question but...

GaryKelly · Guru

Amps. Silly question but...

bill12 · Guru

Volts x watts =amps . 200watts @12volts=16.5 amps(aprox) . You can only use about 60% of 200 amp /hr fromthose two batteries as they just aare about flat after that.If you want your batterys to last keep them above 80% charged. Bill

brian · Guru

If the two batteries are connected in parallel, then the total Ah will be the sum of the 2, ie 100+100 =200Ah. If the batteries are connected in series and are identical Ah capacity, then the total Ah will be the same as that of just one battery.

GaryKelly · Guru

Which is fine if you understand the difference between parallel and series. For example, batteries installed in a torch or radio... are they in parallel or a series? And what's the reason for choosing one over the other?

oldbobsbus · Guru

GaryKelly wrote:
And what's the reason for choosing one over the other?

Size and weight...
If you work out you need 200ah to do your job then you need to find room for a 200ah battery or maybe 2 x 100ah batteries placed slightly apart for space or weight distribution purposes..

brian · Guru

GaryKelly wrote:
Which is fine if you understand the difference between parallel and series. For example, batteries installed in a torch or radio... are they in parallel or a series? And what's the reason for choosing one over the other?

Come on Gary, are you doing a bit of trolling here? confuse

mickm · Veteran Member

Don't forget to mention that the voltage of 2 12V batteries in series is now 24V.

Woolly · Senior Member

Don't know if he is trolling or not but I would like the answer, I don't know the difference between parallel & series or the reasons for it.

An explanation in layman's terms would be great for a simple bloke like me. In my van I have 2 100ah batteries with a cable running from - to - & + to +, is that a parallel or series.

-- Edited by Woolly on Wednesday 22nd of January 2014 04:51:55 PM

justcruisin01 · Guru

Woolly wrote:
Don't know if he is trolling or not but I would like the answer, I don't know the difference between parallel & series or the reasons for it.

An explanation in layman's terms would be great for a simple bloke like me. In my van I have 2 100ah batteries with a cable running from - to - & + to +, is that a parallel or series.

-- Edited by Woolly on Wednesday 22nd of January 2014 04:51:55 PM

Parallel; & the other is series which is ; + of one to load; the - of same to the + of the second batt & - of that batt to earth. This gives you a 24volt system.

bill12 · Guru

Gotta watch them trolls, Gary. They seemto be everywhere on the web.I take it you want to run the fridge off the batterys,is that right? Bill

oldboar · Senior Member

Gary, in theory the two 100AH batteries connected -to- & +to+ (parallel connection) will give you 200AH. However, in practice you'd be lucky to get much more than 50% of the battery rating without causing harm to your batteries. On the bright side you will get twice the practical power of a single 100AH battery (practical rating around 50AH).

Darrell

Woolly · Senior Member

Thank you Justcruisin, now know a little bit more.

So with that & a comment made on another thread of a fridge taking X per day, I am getting closer to knowing what I need.

Should have enough battery to run the fridge, leds, radio etc., won't be running much else and my greatest concern was the fridge.
Now just need to get the solar installation done to keep the batteries charged as currently it only charges of alternator

brian · Guru

Woolly wrote:
Don't know if he is trolling or not but I would like the answer, I don't know the difference between parallel & series or the reasons for it.

An explanation in layman's terms would be great for a simple bloke like me. In my van I have 2 100ah batteries with a cable running from - to - & + to +, is that a parallel or series.

-- Edited by Woolly on Wednesday 22nd of January 2014 04:51:55 PM

My sincere apologies if it was not trolling but I assumed this was a known thing.

For the below explanations we will assume that identical value items are being used, for instance 12v 100Ah batteries and 18Vmp 100 watt solar panels.

1. A parallel battery or solar panel connection is where you connect the positive terminals together and the negative terminals together and take a wire off each for the output.

In the case of batteries, the total voltage available will be that of one battery = 12v.

The capacity will be the sum of the individual capacities, two 100Ah batteries in parallel will give 200Ah. These could be different values as long as the voltages are the same

For solar panels, the total voltage will be that of one panel = 18v

The total wattage will be the sum of the individual wattages 100 + 100 = 200w. These could be different values as long as the voltages are the same.

The maximum available current will be the sum of the individual currents from each panel. These may be different if the wattages are different.

2. A series battery or solar panel connection is where you connect the positive of one battery or panel to the negative of the other, and take a wire from each of the other positive and negative battery or panel terminals for the output.

In the case of batteries, the total voltage available will be the sum of the individual battery voltages, 12 + 12 = 24v

The capacity will be that of one battery, 2 x 100Ah batteries in series will give 100Ah.

For solar panels, the total voltage will be the sum of the individual voltages, 18 + 18 = 36v

The total wattage will be the sum of the individual wattages 100 + 100 = 200w.

The maximum available current will be that of one panel.

3. For resistances in parallel, a formula is required to get the correct figure, but the total will always be less than the smallest resistance.

For resistances in series the total will be the sum of the individual resistances.

Hope this helps.

valiant81 · Senior Member

Hi all;

Parallel and /or series batterys , OK

If you have two 12 Volt 100 Amp batterys in Parallel , eg both + terminals connected together of each battery and also have the - terminals connected to gether. The total voltage that you would have is 12 Volts and the total A/H would be 100 +100 = 200 Amp/Hours. This is what you would call Parallel circurit.

Now if we now have two 12 Volt batterys both have a capacity of 100 A/H each and were wired in SERIES, eg the positive terminal from one battery is connected to the negitive terminal of the second battery and we mesured the voltage across the two remaining terminals, we would have a total voltage of 24 Volts, BUT still have a battery capacity of 100 A/H.

If you are a old fa*t like me and remember the xmas lights that you had on your xmas tree when you were young. Well if one bulb ( light ) failed , well the hole string of lights would not work, untill the defective bulb was replaced. If you remember this type of xmas tree lighting, well this is a series circurit. Parallel circurits and if we use the xmas tree theory, well if one bulb failed all of the other bulbs would still work.

I do hope this clears up a few things

Woolly · Senior Member

Thank you Brian & Valiant,

So in reality the only time you would have a series is if you want 24v or larger as in the case of the golf carts I hire out here which are 48v. As you can tell I don't service them & when something goes wrong someone else fixes them, that's why i pay a lease with full service & repairs.

Now in the case of a motor home, wouldn't a parallel setup be better for if you have 1 battery fail you will still have availability of power just not as much stored so not available for as long ?

Do people with existing 12v vehicle setups like mine ( Fiat Ducato) change to 24v setups & why, I could understand it if they had a 24v system already like in a large bus or truck base.

Sorry for the ?'s but I am learning and at this stage I think I'm keeping up with it. Usually when there is posts about Solar and amp, volts etc it is way to indepth and loses me after the 1st couple of lines.

brian · Guru

Woolly wrote:
Thank you Brian & Valiant,

So in reality the only time you would have a series is if you want 24v or larger as in the case of the golf carts I hire out here which are 48v. As you can tell I don't service them & when something goes wrong someone else fixes them, that's why i pay a lease with full service & repairs.

Now in the case of a motor home, wouldn't a parallel setup be better for if you have 1 battery fail you will still have availability of power just not as much stored so not available for as long ?

Do people with existing 12v vehicle setups like mine ( Fiat Ducato) change to 24v setups & why, I could understand it if they had a 24v system already like in a large bus or truck base.

Sorry for the ?'s but I am learning and at this stage I think I'm keeping up with it. Usually when there is posts about Solar and amp, volts etc it is way to indepth and loses me after the 1st couple of lines.

Not necessarily.

My own set up consists of 6 x 225Ah 6v batteries.

They are connected in series pairs which are then connected in parallel

The arrangement gives 12v @ 675Ah.

The reasons I have done this are

1. The batteries are cheaper,

2. Each battery weighs less, which is easier on my back

3. The total footprint for the achieved capacity is smaller.

4. Total weight for the capacity is lower.

Regarding battery failure, parallel setups can be a problem if you get a short circuit in one battery as the other one will discharge into it, but you will still have some capacity, and you can disconnect the faulty one and continue with what is left.

Series setups don't have this problem, but if one battery gets a short circuit you may lose part or all of your capacity.

An open circuit will cut the output completely.

A series /parallel configuration such as mine overcomes this problem.

Remember that ALL 12v lead acid batteries are a series string of 6 x 2v cells, and every one of those cells is a parallel configuration of plates.

It would be very unusual to change an existing motorhome setup to a different voltage as the vehicle electrics would be incompatible.

If the house supply is separate from the vehicle electrics, then you can do as you wish but there is more equipment available for 12v applications.

-- Edited by brian on Wednesday 22nd of January 2014 07:36:06 PM

SnowT · Guru

Ok here some pic's for you..

In nearly every RV out there, they do not have enough solar to recharge the batteries that they have.. especially if the same batteries are taken down to 50% SoC..

The best you can expect is to get your batteries to 85%.. So the best usage you can expect is a system that get's to 85% and gives you 35% of the total Ah of the system..

- So have I thrown the Cat among the Pigeons..

If you only use a small amount of power, like a few light's etc.. you should be fine.. The minute that you start to dive deep into the battery charge, don't expect to get a full charge unless you can hook up to an external power supply and charge it that way..

All of the above is respective of Lead Acid Batteries, no matter what form they come in.

Juergen

valiant81 · Senior Member

Hi all;

Thanks SnowT, One drawing is worth 1000 words , spot on. My own set up in my caravan and every thing runs off 12 Volts ( except the micro wave and air conditioner ). We traveled over to Victor Harbour for Xmas last year for a few days of R&R ( beer ). My caravan has 2x 120 Watt solar panels, 30 Amp controler and one 200 A/H deap cycle battery, sealed. I only got the after noon sun as we were parked under a big tree at the caravan park, and for a test i turned off the built in battery charger that came with my caravan from new. Running the two 40 Ltr Engle fridges (one as a freezer ) + the rest of the caravan load, eg 12 Volt led lighting, tv and a small 300 Watt pure sighn wave inverter for the vast sattilight receiver. the battery lasted 2 days befour the low voltage cutout, cut in ( battery voltage down to 10.9 Volts ) and disconnected the load from the battery. This battery was second had when it was given to me and had, and several others, had been replaced off a house boat that was on perminant hire. I have had this battery for now on 5~6 years and i was even able to carbon pile load the battery and still came up to about 95 % capacity, ended up sinking 650 Amps from the battery for about 20 seconds ( carbon pile started to smoke ) but the voltage at this point was still 11.9 Volts.

I would love to know how the battery would have held up IF i had more sunshine or had not been in the shade as mutch.

oldtrack123 · Guru

HI

A 200W solar panel will only put out a max of around 11.75A

If it is operating at RATED temp 25C & rated light input

Depending on TYPE of regulator used It will feed :

[a] with a PWM reguator & depending, on battery SOC, it will feed 11.75 A x battery voltage

Taking two extremes of battery SOC

[neglecting internal reg losses]

[1] With a battery SOC of 11.5 [dead flat ]it will put 11.5V x11.75V =138W= 69% of rated output

[2]With a SOC of 14V ,it will put 14V x11.75V =164.W =83% of rated output

Under the same conditions [in theory] A GOOD MPPT controller is not affected by battery SOC voltage

In the above cases it would put in:

[1]17.4A x 11.5V =200W

[2]14.3A x14V =200W

Both types could have internal losses of 5<10%

But Ahrs capacity cannot be defined in WATTS because most rechargeable batterries do not have a constant input or output voltage

The only ones that come close to constant voltage are LiFePo Batterries

-- Edited by oldtrack123 on Thursday 23rd of January 2014 09:53:12 AM

-- Edited by oldtrack123 on Thursday 23rd of January 2014 09:57:38 AM

Woolly · Senior Member

Thank you everybody,

Most of the comments were in terms that even I could understand.

I will sit down and work out oldtracks last comment when I have a bit of time, at work at the moment. It when you start getting abbreviations that I run into trouble, but will work out what they are.

It is really good to see a discussion that is readable by everybody & not just all technical mumbo jumbo, I know we need the mumbo jumbo to work out all the outcomes, but a lot of us just want to be told that you need this, this & this to have that, that & that.

WAssa41 · Senior Member

This is the best site http://www.smartgauge.co.uk/batt_con.html that I have seen that gives you all you need to know on how to connect batteries. The way to connect multiple batteries was very interesting and I thought I new it all (well almost). Gary once you have read it you will become an expert?

Wassa

beiffe · Guru

Oldtrack wrote
"The only ones that come close to constant voltage are LiFePo batteries".

I didn't think I would ever see you say that Peter.

Regards
Brian

Woolly · Senior Member

Just making Wassa41's link click-able,

http://www.smartgauge.co.uk/batt_con.html

-- Edited by Woolly on Friday 24th of January 2014 07:48:34 AM

WAssa41 · Senior Member

thanks Woolly What did IO not do

Wassa

Mr B2 · Senior Member

I like it, Its easy to follow, Piccys make it even easier, We are not all Wizz Kids with electricity,

GaryKelly · Guru

Thanks to all the technically minded for clearing that up. And no, I'm not trolling. My brain switches off when people start talking numbers, polarity, percentages, etc. I'm still trying to figure out what 36 22 34 means. And I still use a calculator only for additions and subtractions... forget all that percentage and square root gobbledegook.

So it looks like parallel is the way to go for me... 12 volt. To answer your question, Bill, I'll be running my fridge on gas when camped but there might be times when I'm parked for a while in town or whatever when I run it on battery. The battery is also charged by the engine's alternator so I could also run it on battery during a long drive.

brian · Guru

Gary, I would strongly suggest that you don't run your fridge off the van battery at ANY time, especially when parked, as it will kill it very quickly.

You should have a separate circuit from the car to the fridge for operation only when in motion, and another from the car to the van battery for charging.

oldbobsbus · Guru

brian wrote:
Gary, I would strongly suggest that you don't run your fridge off the van battery at ANY time, especially when parked, as it will kill it very quickly.
You should have a separate circuit from the car to the fridge for operation only when in motion, and another from the car to the van battery for charging.

See Gary, then When you get in you ute to move off you you will feel like an airline pilot with rows of switches everywhere to switch and you will need rows of gauges to tell you what everything is doing...lol.. so you could spend 15 mins just sitting on the runway/driveway getting ready for take/drive off.. confuse confuse confuse confuse confuse

Sorry Brian I could resist the opportunity.. smile

brian · Guru

oldbobsbus wrote:
brian wrote:
Gary, I would strongly suggest that you don't run your fridge off the van battery at ANY time, especially when parked, as it will kill it very quickly.
You should have a separate circuit from the car to the fridge for operation only when in motion, and another from the car to the van battery for charging.
See Gary, then When you get in you ute to move off you you will feel like an airline pilot with rows of switches everywhere to switch and you will need rows of gauges to tell you what everything is doing...lol.. so you could spend 15 mins just sitting on the runway/driveway getting ready for take/drive off..

Sorry Brian I could resist the opportunity..

You might need to explain that to me Bob, my suggestion would not place any more switches anywhere.

oldtrack123 · Guru

beiffe wrote:
Oldtrack wrote
"The only ones that come close to constant voltage are LiFePo batteries".

I didn't think I would ever see you say that Peter.

Regards
Brian

Hi Brian

What certain parties never did understand was THAT I did not have a problem with LiFe Po4s as such & WAS well AWARE OF THEIR VERY FLAT VOLTAGE CURVE right from the START

If that other forum was still available you would reread it ALL you wuld see that was ONE of my points of concern [regarding monitoring for SOC]

The other was what to many[who did not understand that you must always have some losses when charging or discharging ]but these batterries where constantly been given the impression that they were miracles that did not follow the normal laws of PHYSICS

THOSE laws have not changed EVEN NOW

THEN there were the posters who were always quick to post what they could do with their batterries but it took a LOOOONG

time for them to reveal the charging capacities they had available.

Then we had a leading light ,Who could never understand the Energy cannot be accurately measured in AMPHRS , THAT Even today is NO SUCH unit of energy measurement.

The basic unit for ALL electrical energy use is WATT HOURS!!

PeterQ