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Battery charging

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Bob Abell18/07/2015 12:11:29
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8270 forum posts
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Hi chaps

This may seem an obvious question to some people, but I`ve scoured the net and found nothing relevant

How long will it take a Turnigy charger, charging at a rate of 1.2 amps, charge a Ni-MH 7.2 volt battery of 4600 mAh

Thank you

Bob

Dodgy Geezer18/07/2015 13:01:31
818 forum posts
59 photos

How long is a piece of string?

I am certainly not an electronics specialist, but my understanding is that you can charge batteries at different rates, so you select the amps for the time you want to take.

A convenient rule of thumb is that a slow charge is 1/10 of the nominal capacity of the battery for 14 hours. Every battery should be able to accept that. So you could charge a flat 4.6Ah battery at 0.5amps for 14 hours.

Some batteries can take a 'quick charge'. So your battery might be able to take a 1.2A charge for about 5 1/4 hours. Or a 5A charge for 1 hour. Or a 20A charge for 15mins. The battery should indicate what the maximum charge rate it can accept without blowing up is!

Of course, the battery has to be 'flat' for the full charge to be correct. More complex chargers can detect when a partially full battery is fully charged, and shut themselves off at that point...

Bob Abell18/07/2015 13:16:29
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8270 forum posts
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Many thanks DG, but your answer is very similar to the net answers I received

I should think I've supplied sufficient info to enable an exact answer

Bob

Dodgy Geezer18/07/2015 13:30:01
818 forum posts
59 photos

I should think I've supplied sufficient info to enable an exact answer

 

The exact answer, as I wrote above, is 5 1/4 hours. You will see that written in the 4th paragraph down. My calculation actually made it 5.38 hours, or 5 hours 23 mins. If you want any more precision, we will need to see the precise specification of the battery, since charging efficiency will vary depending on battery type.

Edited By Dodgy Geezer on 18/07/2015 13:30:23

Edited By Dodgy Geezer on 18/07/2015 13:31:24

Edited By Dodgy Geezer on 18/07/2015 13:35:05

Bob Abell18/07/2015 14:10:36
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8270 forum posts
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Thanks once again, DG........5 1/4 hours?

The batteries I'm using are the type that go in buggies and cars and in the old days, we used to fast charge them in about 15 mins

What further info do you need to know?

Bob

ashley needham18/07/2015 15:08:47
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5608 forum posts
177 photos

Bob. One would have thought the Turnigy charger is automatic and would cut off when the battery is charged?? or is that not the issue?

I have batts charging at the moment and every now and then I pop in and if one of the charge lights is green I unplug that one and put another in.

Ashley

Bob Abell18/07/2015 15:20:21
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8270 forum posts
2530 photos

Hello Ashley

I've got a top notch charger that certainly cuts out when the battery is fully charged

I just want to know the time it should take to charge the battery.....So that I am not caught out

At the moment, after about 30 mins running, I want to top up the battery

At the moment, I'm getting 30 Mins to 2 hours

I can't hang around for 5 hours per battery......That's a total of over 21 hours!

What do you think of my charging rate of 1.2 amps?

Bob

Paul T18/07/2015 15:20:30
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6751 forum posts
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Hello Bob

This subject is way out of my field of expertize, just like Ashley I plug them in and forget them until the green light pops up. However I have found this site a useful rule of thumb guide. **LINK**

Paul

Sorry all the link didn't work

Edited By Paul T on 18/07/2015 15:48:14

Bob Abell18/07/2015 15:50:37
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8270 forum posts
2530 photos

Thanks Paul

We are nearly there, but.......

How many mili amps are there in 1.2 amps?.......1200?

So it looks like.....4600 / 1200 = 3.8 hours......( Why does DG say 5 1/4 hours?)

Previously it only took 40 mins to top up the batteries

Now it's taking 2 hours......So I was getting a bit concerned

So the question wasn't that obvious after all!

Many thanks to all concerned

Bob

Paul T18/07/2015 16:19:15
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6751 forum posts
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Bob

Which Turnigy charger are you using, what make and cell size of batteries and how many in the stack, finally how old are the batteries and how many cycles have they had.

Paul

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