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Battery Charger query

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Posted

Simple question 

What voltage should I expect to see from a battery charger 

said charger is 24v  12Amp - -  -- it is delivering 27.3v not the 28+v I'm expecting the charge is then split into two batteries and they are coming out at 13.3v and 13.4v each when the charger says they are full

I was expecting them to read 14.5v at least 

 

can anyone help me with this or do I buy a new charger and a pair of new batteries

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Posted

:wine:

Here we go ...

Given that you're using a 24v charger delivering 12A to charge two 12v batteries then the batteries are in series. Without getting too complicated (Mainly cos I can't remember all my electrical theory from 1976) the current flow will be affected by the small differences in resistance of the batteries - they will NOT be identical in terms of their electrical characteristics ! The result of this is that the potential difference (Voltage) across each battery will be different despite the same current flowing through both.

As for getting a lower voltage than you expect, assuming you're measuring the voltage with the charger working then the voltage could be being dragged down by the load of the batteries OR if you are using a smart charger it could be that the batteries are near full charge and the charger has reduced the voltage in order to avoid boiling the electrolyte.

If you can clarify any of my assumptions I should be able to come to more precise conclusion

 

:wine::wine::wine:

 

:England:

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Posted

I would go with Bob on this , further suggesting , using a 12v charger and charging the batteries  separately so each battery is unaffected by the other

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Posted

I would echo the sentiment about charging each battery individually,particularly if you have access to a smart charger.

 

Cheers

 

Keith

 

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Posted

I have just the one charger for my scooter it is "Supposed" to be a smart charger and it does drop to trickle when the batteries are "full"

When the batteries are discharged  it delivers 27.4v when the batteries are charged it delivers 27.2v 

the voltage on the batteries are when disconnected 

there is no perceptible voltage drop when comparing the voltages from the charging plug to the battery terminals 

I know that both batteries WILL be different even though they are the same age but the surprise for me is that when not in use or on charge they retain their charge but once under strain they quickly drop yet the charger never shows any more than 25% loss but the controller says they are 80% (the controller goes into limp home mode for 15 minutes then cuts out)

So 

My thinking is 

Batteries may be life expired - - replacement cost £200

Battery Charger may be faulty - -  replacement cost £80

Controller may be faulty too - - replacement cost £150 min

 

OH my more money needed

 

 

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Posted

:wine:

My first suspicion would be that the batteries are buggered - how old are they and have they ever been left fully discharged for an appreciable time ?

 

:wine::wine::wine:

:England:

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Posted

Could you beg/borrow/steal a 12v battery charger , even a cheap one from Halfords etc , and check each battery .perhaps even use your caravan charger , then a better picture of the condition of each battery can be gained.

We deduce this is a mobility scooter with on board/remote  charger , and gell batteries ,

Do you know the age , or perhaps the number of charge/discharge cycles of the batteries ?  Gells are more robust and are able to stand deep discharge better than standard batteries but do have a finite life  , so a period of full charge whith a different charger may well help to revitalise  ,When , in the deep and distant past I was working on fork lift trucks and electric tugs , over the weekends the batteries were put on "equalising charge " this was to gently fully charge and desulphate the cells.

Chargers are funny things , open terminal voltages can not be related to the output when connected , so if you can, it would be useful to eliminate the dedicated  charger one way or another by using an alternative charger

Then Google/ Amazon it is

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Posted

Now I understand the question....

Get your batteries tested with one of these:

media.nl?id=2162&c=317638&h=1d93f5ffc770

If as you say your batteries are dropping by 80% then that's what I'd be looking at

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Posted

Now I understand the question....

Get your batteries tested with one of these:

 

If as you say your batteries are dropping by 80% then that's what I'd be looking at

Picture deleted for space 

 

Where do I find a user of such a contraption is that an Amperage tester ??

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Posted

:wine:

My first suspicion would be that the batteries are buggered - how old are they and have they ever been left fully discharged for an appreciable time ?

 

:wine::wine::wine:

:England:

Just for clarity the batteries are from 2014 and have never been left in a discharged state  the are Lead Acid Gel and in line with the instructions given when purchased (my usual practise anyway) they are always connected to the charger except when in use  

 

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Posted

Picture deleted for space 

 

Where do I find a user of such a contraption is that an Amperage tester ??

Halfords will do it for you

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Posted

Batteries used as a pair should be replaced as a pair...

2 year old batteries should be under guarantee

Have you had the motors checked? If there is a lot of carbon (from the brushes) in them it could be causing a short

Unfortunately the battery supplier has gone to the wall so no chance there and they are sold in pairs £337 a pair for equivalents

Motor is clean as a whistle gearbox is new and free running

Also priced up new 12 Amp charger £175

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Posted

Gel batteries will always be more expensive - do you intend rolling your scooter a lot or putting it on it's side?

If you aren't doing that perhaps you should look at Sealed Lead Acid Batteries - think you'll find them a lot cheaper.

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Posted

Gel batteries will always be more expensive - do you intend rolling your scooter a lot or putting it on it's side?

If you aren't doing that perhaps you should look at Sealed Lead Acid Batteries - think you'll find them a lot cheaper.

Or AGM batteries  which can also be inverted (but not recommended).

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As I go on I've been discussing stuff with an auto electrician and got this item recommended as a useful DIY tool 

6v&12v 100amp load drop battery tester and charging system tester and just under £20 on fleabay 

 

So I will be able to tell just WHAT I need to replace

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Posted

Batteries used as a pair should be replaced as a pair...

2 year old batteries should be under guarantee

Have you had the motors checked? If there is a lot of carbon (from the brushes) in them it could be causing a short

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