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Author Topic: Charging rates/times  (Read 6262 times)

oooo

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Charging rates/times
« on: September 07, 2006, 07:38:38 pm »

I've some sealed lead acid battery's, 6 volt 4-5ah  and 6 volt 12ah.

My basic charger is 400ma.

My question is how do i work out the charging times. thank's in advance.
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Peterm

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Re: Charging rates/times
« Reply #1 on: September 07, 2006, 07:53:40 pm »

Divide battery AHr by charging current, eg 4.5 AHr divided by 400mA equals 11 hours approximately.   Pete M
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oooo

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Re: Charging rates/times
« Reply #2 on: September 08, 2006, 12:49:50 am »

Cheer's 
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oooo

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Re: Charging rates/times
« Reply #3 on: September 16, 2006, 11:56:34 pm »

I'v two 6 volt 12ah sla's, i'v been told i can wire them in series and use a 12 volt battery charger. Is this possible and can anyone explain how to do it?
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chromedome

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Re: Charging rates/times
« Reply #4 on: September 17, 2006, 09:18:22 am »

Great website PKM.!!

   chromedome :o
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malcolmfrary

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Re: Charging rates/times
« Reply #5 on: September 17, 2006, 10:10:20 pm »

I must go along with ambernblu - its not given to everybody to understand the electric bits.  I spent much of my working life in the electronics industry, so I find that part easy, my sanding and painting and measuring and cutting is fairly dismal.  If we were all as good as each other at everything there would be no need for a forum.  I cant remember if it was in this forum or  the MB one, but somebody had the motto "the only dumb question is the one that doesn't get asked", or something like that.
Anyway, 2 of six volt 12 AH batteries when connected with the + of one to the - of the other will make a 12 volt 12 AH battery.  For anybody not familiar with battery chargers a sealed lead acid battery is best charged using the appropriate type of charger, i.e. one that is both voltage and current regulated to ensure no damage to the battery.  When making a series chain it is important that all the batteries are of the same capacity, to avoid over-charging the smallest.
In the original post you mention having a 400mA charger.  Do you know what its output voltage is?  Is the output current controlled, or is 400 mA its maximum output?  The difference is that a controlled one will probably charge at 400 mA as long as it is connected, one that can only give 400 mA might give that at the start of the charge, but the output will fall as the charge progresses.  The one that can only give 400 mA will also probably get over-warm and mis-behave if overloaded.  Using a very basic one it is a good idea to have a meter to check current and voltage, but for anybody not used to such items a trip to a reputable model shop for a "proper" charger will pay for itself fairly rapidly.
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JayDee

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Re: Charging rates/times
« Reply #6 on: September 17, 2006, 11:18:25 pm »

PMK,
Quote
You take the terminal of one battery, then connect it to the other terminal of the other battery. Then you take the opposite terminal and connect it to that.

Not exactly clear, for a Beginner, as to which wire goes to where ???.
I know what you are on about, but, will others ??.

How about this.
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ambernblu

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Re: Charging rates/times
« Reply #7 on: September 18, 2006, 12:41:59 am »


Thats great Jaydee.

Yep, like you, I thought the previous offering was completely pointless (no names, no pack drill  ;D) - unless it was to state that those who don't know what they are doing shouldn't get into model boats..... but then I didn't know you had to have a degree in electrical engineering?  >:(
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oooo

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Re: Charging rates/times
« Reply #8 on: September 18, 2006, 12:23:59 pm »

Thank's for the kind word's lad's, and also to the people who sent pm's. Cheer's for the diagram jaydee.

It is of course simple when explained (like alot of thing's) but it must be obvious that someone with no experience of modeling/electrics is going to ask what may appear to the more experienced as very simple question's. If certain people feel the question is "below" them, then just ignore it and leave it to those with a diffrent outlook to help people.
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kikkari

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Are there any issues with balancing of SLA type batteries?
« Reply #9 on: September 18, 2006, 12:54:17 pm »

Does it matter if both batteries are in different states of charge before connecting them in series and charging? 

ie if one is already fully charged and and the other is flat would the fully charged battery suffer any damage during charging?



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MCAT

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Re: Charging rates/times
« Reply #10 on: September 18, 2006, 02:09:43 pm »

jaydee   Any chance of the diagram   on this site for others  would be a good one for hints and tips.. then when I need it I will  know were to look.

Nice to see you took the time to reply to the request.

Mick
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JayDee

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Re: Charging rates/times
« Reply #11 on: September 18, 2006, 03:55:29 pm »

Hello Mick,

What a good idea !.
A hints and Tips Section, so good I have already done it !!.

We will ALL have to monitor the contents that are posted, no accidents PLEASE !.

There must be a great wealth of knowledge on this Forum, we really should be sharing it.

For all of us, long ago, Walking and Talking was a BIG thing, but we were guided through and learned !.

John.  ;D  ;D  ;D.
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malcolmfrary

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Re: Charging rates/times
« Reply #12 on: September 18, 2006, 07:32:05 pm »

kikkari
Yes it is important that both are in a similar state of charge.  While the lesser charged one is catching up, the higher charged one will be overchargeing.  In unsealed batteries this was realatively unimportant, as the products of overcharging could be replaced.  (Probably didn't do the life expectancy of the battery any favours).  You can't do that with a sealed battery. 
Another bit of "obvious afterwards" - if you measure the voltage, disconnect the charger first, otherwise you are measuring the voltage of the charger rather than the battery.
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justboatonic

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Re: Charging rates/times
« Reply #13 on: September 18, 2006, 09:20:25 pm »

Be careful using a car battery charger on small lead acid or gel 12v batteries. As these generally have a capacity of around 3 to 5 amp range and some car battery chargers can whack in a lot more charge than this, you could find your model lead acid or gel battery fully charged in less than an hour.

Even if it switches to trickle charge, you could end up frying your battery. I know through experience!
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malcolmfrary

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Re: Charging rates/times
« Reply #14 on: September 18, 2006, 11:17:09 pm »

It was because of the probability of frying the SLA that I mentioned going to a reputable model shop to get a "proper" charger.  For anybody unfamiliar with building electronic add-ons the only safe way is to grin and bear it and give the man the money.  A good charger and an inexpensive meter are a good investment.  The charger will give predictable results, the meter will let you check that all of the bits should work, or give clues as to which bit is broken.
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kikkari

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Re: Charging rates/times
« Reply #15 on: September 19, 2006, 01:23:35 pm »

kikkari
Yes it is important that both are in a similar state of charge.  While the lesser charged one is catching up, the higher charged one will be overchargeing.  In unsealed batteries this was realatively unimportant, as the products of overcharging could be replaced.  (Probably didn't do the life expectancy of the battery any favours).  You can't do that with a sealed battery. 

Thanks, I wondered if the sealed types were more robust to this kind of abuse compared to the old unsealed batteries.

I have a 12v SLA that I use to charge LiPos, it's just the job being so portable I can always find a safe spot to put my charging LiPo packs well away from anything else.  I've been very impressed with it and I suppose my expectations have lulled into believing SLAs are now a consumer item that is totally impervious to any abuse I might think to dish out in a brainless moment.  I think the contrast with LiPo technology is interesting, LiPos have the spectre of danger, like somehow just charging them is some kind of extreme sport.  I guess the real answer is to treat all containers of power with respect. 
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malcolmfrary

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Re: Charging rates/times
« Reply #16 on: September 19, 2006, 09:48:23 pm »

It is as well to remember that all rechargeable batteries of whatever type are potentially dangerous, being full of either acid or caustic substances, depending on type.  When batteries are installed in consumer equipment, and come with the proper charger they are much safer, or should be.  We on the other hand, install them in a box of our own design and often try to figure a cheaper way of keeping them charged.
It was mentioned somewhere else that using car or motor cycle type lead-acid batteries was a no-no, due to the corrosive nature of the fumes given off doing the innards of the boats no good at all, with special reference to the finer bits inside radio gear.
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laserblue16

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Re: Charging rates/times
« Reply #17 on: September 23, 2006, 01:20:49 pm »

What you have to remember,OOOO, is that we were all in the same boat at 1 time(sorry!!!). None of us were born with a complete understanding of everything you need to know about model boat building. If no-one bothered asking questions, this site would'nt exist, there would be no modellers, and life would probably be a lot more boring.I am also new to the whole world of modelling, but have found everyone on this forum to be more than helpful, after all without us beginners the hobby would die out. So just keep asking questions and most people will be only to happy to help.
 Chris
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dpbarry

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Re: Charging rates/times
« Reply #18 on: September 27, 2006, 04:03:13 pm »

I'v two 6 volt 12ah sla's, i'v been told i can wire them in series and use a 12 volt battery charger. Is this possible and can anyone explain how to do it?

Yes, it is possible, and loads of people can explain how to do it. What you do is this... You take the terminal of one battery, then connect it to the other terminal of the other battery. Then you take the opposite terminal and connect it to that. By then you'll be ready for your first 'Please-let-me-learn-how-to-do-even-the-most-basic-of-basics-before-they-let-me-on-the-water-and-create-mayhem-among-everyone-else' test.
A bit like giving your woman joy BEFORE yours, sort of thing.
And don't forget to connect the black wire to the other terminal of your 12-volt charger.



Hmmm!!  Not sure of the logistic of charging 2 - 6V batteries in series with a 12V charger but the response you gave is very dangerous and sarky especially since you didn't explain which terminal (+ or -) connects to which terminal on the other battery.

The potential in your reply is for an almighty bang!!

Declan
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warspite

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Re: Charging rates/times
« Reply #19 on: September 27, 2006, 07:12:02 pm »

 To follow in a similar manner - it was mentioned about connecting a multimeter into the system to measure the charge, this is going to sound dumb, but how? i.e. several multimeter designs can flumax some people and which lead connects to which terminal, what settings do you start at, ie a higher one and select down till the meter registers. what would be an acceptable compromise on the reading + or - 0.001 (it could make a difference if the scale is digital compared to anologue - and those who are unsure of what a multimeter is, whats digital ;D).

As i said, i know this seems dumb, but like others, i am not great with electrics, pictures and diagrams are an invaluable addition and explain what others cannot say in words or spell ;D

Martins main site has a superb section for the wiring etc but diagrams and photo's help, what i have is not the same as the next guy and a variety of different arrangements help, tips and tricks are what gives us experience, my main problem at the moment is seating motors in very small boats, pictures of putties, plastics, sealants, resins help give clues what to look for, how many times have we gone to the shop with a product name only to be met with bemusement or given an option for a comparable product only to leave without it because we were not sure as to how good it is, delaying the project even further.

a rant for sure but we have all been there in one form or another and will continue to as we are always learning and new products come on line.

To Martin
In the hints and tips section on the main site (or even here on the forum) what would you say to having threads on certain core products etc resins, glues, motors etc (with a picture so we know what it looks like as well) where members put forward a product and others vote on its pro's and cons based on their experience etc, eg P38 60% like it 25% hate it 15% are indifferent something along these lines (figures are representaive and are not factual - just thought i would put in a disclaimer just in case :D). See what other forum members think.

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OMK

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Re: Charging rates/times
« Reply #20 on: September 28, 2006, 08:10:57 am »

To Martin
In the hints and tips section on the main site (or even here on the forum) what would you say to having threads on certain core products etc resins, glues, motors etc (with a picture so we know what it looks like as well) where members put forward a product and others vote on its pro's and cons based on their experience etc, eg P38 60% like it 25% hate it 15% are indifferent something along these lines (figures are representaive and are not factual - just thought i would put in a disclaimer just in case :D). See what other forum members think.

Now that's a good suggestion. In these days of digital cameras, it surely wouldn't be too difficult to post a picture of said products, along with a few words to say if they're any good or not.
Neat idea.

To follow in a similar manner - it was mentioned about connecting a multimeter into the system to measure the charge, this is going to sound dumb, but how? i.e. several multimeter designs can flumax some people and which lead connects to which terminal, what settings do you start at, ie a higher one and select down till the meter registers. what would be an acceptable compromise on the reading + or - 0.001 (it could make a difference if the scale is digital compared to analogue - and those who are unsure of what a multimeter is, whats digital ;D).

See your point.... pictures speak louder words.
Measuring current is just as easy, but slightly different than measuring voltage.
You measure voltage across a load, but measure current through a load. A load can be described as anything that carries a potential difference (P.D). PD is always measured in volts. Said load can be anything from an incandescent lamp, a light-emitting diode, a motor... you name it.
The formula for calculating current is I=V/R. In straight money that means the current (I) equals V (volts) divided by R (resistance). So in order to measure the voltage across, say, a motor, simply connect the meter + and - leads to the corresponding + and - terminals at the motor. This is called a parallel connection. Measuring current involves breaking the connection between the P.D and the load. The meter is then connected at the point of the break. This is called a series connection.
Referring to the first sketch, you can see where this series connection is made between the battery and the LED. Since the battery potential is at 9 volts and the resistance is at 470 ohms, the calculated current should be somewhere around 0.019 amps (the same as saying 19 milli-amps, or just 19mA). Notice I said 'somewhere around'. This is because the battery may be anything other than its rated voltage. It might be as high as, say, 9.5 volts. Also, the resistance has a tolerance rating... commonly 5%. In the real world, the resistor could be any value between 446.5 ohms and 493.5 ohms. This means your meter may show a slightly different reading than the expected 19mA. Nothing to be too concerned with in this instance, but it is something to be aware of when measuring close-tolerance circuits. Notice how the meter is set to the milli-amp range.
But in order to measure high-current loads, e.g: motors, set your meter to the Amps range (see sketch #2). A motor will pull a lot more juice than a LED. Measuring high currents on a low-current range will blow the meter's internal protection fuse. Most of today's digital multi-meters can handle up to 10 or 20 amps, so when measuring high currents always start at the highest range setting.
If you should inadvertently get the red and black leads reversed, nothing bad will happen. A negative (-) sign will appear at the left-hand side of the most significant digit, and this is indicative of a wrong polarity connection. But this applies to digital meters only. If you're using an analogue meter do bear in mind (when measuring current) that the red/black leads will have to be transposed. Bear in mind also that an analogue meter is not as forgiving as its digital counterpart. If you should accidentally stuff it with 20amps with the wrong polarity, there's every chance of damage to the delicate meter movement. If you're lucky your analogue meter may be protected with an internal fuse.

Once you have the current reading, it's then a simple matter to ascertain the power drain. Power is measured in Watts. Watts are calculated by simply multiplying the voltage by the current (P=V*I). So if you power your model with, say, a 12-volt gel-cell, and your motor pulls 5 amps, the power drain will be in the order of 60 watts.
There are other ways to calculate power, resistance, current and volts. Formulas shown here are derived from basic Ohm's law.

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OMK

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Re: Charging rates/times
« Reply #21 on: September 28, 2006, 03:26:00 pm »

Great website PKM.!!

Hey, Chromedome. Thank you.
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Re: Charging rates/times
« Reply #22 on: November 20, 2006, 09:05:43 pm »

Topic moderated as request.
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Telstar

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Re: Charging rates/times
« Reply #23 on: November 21, 2006, 12:45:59 am »

Hi May I recap some of the points made allready. The AHr rating of a battery is a measure of the charge capacity, and is as already mentioned the product for current and time (amps x hours) When I was in industry we used to have a variety of batteries to maintain. For normal charging we took the 1Hr current ( for 4AHr it would be 4 amp) divided this by 10 to give normal charging current (in this case 0.4A or 400mA) then because you never get out as much as you put in we charged for 14hrs, this rule of thumb came from the manufacturers info that was supplied with many of the batteries when new. With all the battery chargers there was an ammeter fitted, and the output could be regulated. As was also mentioned before, this way of charging was monitored by people who had training, there are a large number of "automatic" and "intelligent" electronically controlled chargers on the market so untrained users don't get problems but you should only use these controlled systems with the type of battery they are designed for. The charge characteristics of a Ni Cd battery is very diffrent to those of a Lead Acid battery be it wet or gel pack. I have seen Ni Cads explode when put on charge and forgotten, on a uncontrolled charger. In most cases charge at a lower current, and don't leave unattended when "fast charging", If the battery starts to get hot switch off
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