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Author Topic: Battery Charge levels  (Read 2232 times)

Ghost in the shell

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Battery Charge levels
« on: July 26, 2007, 10:31:36 PM »

Ever wandered what voltage is safe to go to the lake with, well I did some simple tests with a Multi meter and a charger, charging up my packs, measuring them as soon as they have come off the charger then about 30 mins later after they have stabilised.  here are my results - see word attatchment.


Charging information for batteries         
               
Battery Type   Rated Voltage    just charged V   normal V      
4.8v 4cell   4.8   5.53   5.17      
7.2v 6cell   7.2   8.3   7.76      
8.4v 7cell   8.4   9.6   9.05     *caculated data based on 7.2v data
9.6v 8 cell   9.6   11.6   10.3     *calculated data based on 7.2v data
6v gel cell   6   7   6.56      
12v gel cell   12   14   13.12    * calculated data based on 6v data
               
This is intended as a guide, different readings on the meter may be given depending on
battery brand or age of battery.  Nickel metal hydride batteries, (ni-mh) may give
different readings to nickel cadmium type batteries, but on the whole, the difference
between ni-cd and ni-mh batteries will be slight.         
               
some results have been calculated based on other batteries, results may vary.

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Tug-Kenny

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Re: Battery Charge levels
« Reply #1 on: July 27, 2007, 10:57:55 AM »


Very interesting Ghost. Thanks for that.

When charging batteries, when does one stop.  That is to say, how do we know when they are fully charged if we only have a meter. 

When we have the battery in front of us, how do we measure the amp hours of use we can expext to receive ? I know that some chargers have sophisticated shut down systems when fully charged, but I only have the transformer type.

Hope someone can shed a light on this.

Cheers...Ken

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Stavros

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Re: Battery Charge levels
« Reply #2 on: July 27, 2007, 01:36:50 PM »

Batt charging is a very complex area!!!!!!!!!!!! I only wish someone would come up with a meter to actually check the percentage charge that is in a batt,yes I know that hi-tech do one that does 6v and 4.8 it would be so simple to be able to check exactly how much capacity a batt has in it.A simple voltage check in my opinion is not enough as a 6v batt will still read 6v even with only holding 40%charge so testing with a voltmeter will yes I know give you the voltage but not how much capacity the batt has.when testing a 6v batt for a yacht I find it so easy to connect to the hi-tech meter to see exactly how much % charge that is in it,so much more accurate then a voltmeter.So the big question is why does no one make such a meter for 12v and below ,so one can then check racing packs etc.Stavros
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sweeper

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Re: Battery Charge levels
« Reply #3 on: July 27, 2007, 04:35:32 PM »

Stavros, it may be of interest to you that there are such chargers available for use on 12V. I have recently replaced my old charger with one, it will do both lead acids and gel cells. It came as a surprise when I connected it up to be given the info that my battery was only 60% charged!. (Who reads the instruction leaflet anyway?) It will also take the battery through a very good sequence of charging over a period of time including de-sulphation of the plates. Cost about 35 for a 8A unit, they also do one that gives 12A.

I would be very cautious of relying on voltage readings taken from cells off-load. I was taught that to obtain a true value any cell or battery should be tested on-load. To use data obtained on one voltage cell and then extrapolate values for other value cells could also be very misleading.
A further rider to this would be on using a multimeter for the test. It was not stated in Ghosts data what type of multimeter was being used but, from practice, it should be noted that any analogue instrument is built to have a certain accuracy. Even good class instruments (AVO etc) have a tolerance. Having tested a number of the cheapo ones available under lab conditions I have found that they can tell a very different story!
I'll not comment on digital instruments as my practical stuff did not extend to them (although I have used them on occaision). No doubt one of the light current guys can provide the required info on them.

Just my observations.....
Regards.
 
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John W E

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Re: Battery Charge levels
« Reply #4 on: July 27, 2007, 05:13:33 PM »

Come on you gents on here, this is such good stuff.

Do you fancy doing an article/write up from start to finish about charging and recycling batteries and battery packs?    Good information this and there are a lot of people asking for it.

aye
johne
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Peterm

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Re: Battery Charge levels
« Reply #5 on: July 27, 2007, 06:25:16 PM »

I have got one of these fancy, all singing, all dancing battery chargers, but I very often use a much simpler method to check batteries.   I have a 500 type motor mounted on a small wooden board with its leads going to two terminals on the board.   When I want to check a battery, of any sort, I connect the leads of a digital multimeter, set to volts, to the terminals and then connect the battery.   This gives the battery voltage under load.    This little set up is also used to check out ESC`s and receivers.   Pete M.
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Tug-Kenny

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Re: Battery Charge levels
« Reply #6 on: July 27, 2007, 08:06:51 PM »


This would test whether the battery has the strength to run a motor, but it does not indicate the expected life span on the lake.

Could you point me in the direction of these all singing/dancing manufacturers, so that I can do some research. I am after the actual electronics that  'Knows'  what charge to give or not.


Cheers...Ken
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Peterm

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Re: Battery Charge levels
« Reply #7 on: July 27, 2007, 08:15:20 PM »

The one I use is a Pro Peak Super Nova.   Pete M
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John W E

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Re: Battery Charge levels
« Reply #8 on: July 27, 2007, 08:28:32 PM »

Hi all, very interesting replies and stuff, but, not being funny - but the idea of this thread is to be a read only - not questions and answers.   Going to leave it open for a bit longer and then possibly either move the questions and answers bit over to the other electronic thread and leave Ghost in the Shell's first topic.  I was hoping to get other procedures for charging batteries underneath Ghost in the Shell's



john
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Tug-Kenny

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Re: Battery Charge levels
« Reply #9 on: July 27, 2007, 09:16:06 PM »


Sorry John.   My rivits must have fallen out.  ;D

If you could put us 'battery query' people together, that would be great as I've been Googling and come up with more battery information than I need

Cheer...Ken
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justboatonic

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Re: Battery Charge levels
« Reply #10 on: July 27, 2007, 10:10:00 PM »

Good god, just what are some people using to charge batteries?

A decent charger that auto peaks and cuts off charging nicads and nimh cells are not expensive. For a few quid more if you have SLA's you can get a charger that does all 3.

Surely people arent using multi meters in series when charging their cells!?
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John W E

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Re: Battery Charge levels
« Reply #11 on: July 27, 2007, 10:20:34 PM »

Hi there Justboatonic - this is the reason that you have just stated, that we need someone to come on this thread and post the correct way of charging different types of battery.  As I have stated in my previous postings, this is supposed to be a 'read only' and we are looking for people like yourself to put a reasonably short, but comprehensive topic together, about charging different types of battery and then we can lock the thread

john
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Ghost in the shell

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Re: Battery Charge levels
« Reply #12 on: July 27, 2007, 10:33:56 PM »

as its my thread ~L~ thats been jacked here ~LL~ the idea there is more of a usage guide for when you bring batteries out of storage and charge them up.  I had a 10 cell pair, charged both up, yet 30 mins after comming off the charge, one had settled around 13v, the other had dipped to 0v, after recharging it again, the meter was put on it, and you could watch it plummet.

those packs were specific to the najade and are useless elsewhere, so they got recycled, 9.6v pairs replaced them
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