Charging 10 1.2v nimh in series?

[knobby]

Any idea if /how I could charge 10 rechargeables without taking them out of a holder ... ie 12v? But what charger?

They're 2500 mah

Cheers all

[keithatrochdale]

Hi

You can use something like this;

http://www.ebay.co.uk/itm/B6-Lipo-NiMH-Balance-Battery-Charger-for-RC-7-4v-11-1v-/261072482848?pt=UK_ToysGames_RadioControlled_JN&hash=item3cc921f220

In the auto mode.

[knobby]

Thanks Keith.

Do you think that would work, how would I know what settings to use?

Cheers

[Gina]

I think you need to be very careful how you charge NiMH cells - do it wrong and they could explode. I know lead-acid cells are commonly charged in series but NiMH are a totally different chemistry.

[Capricorn]

Doubtfull, and is it really that hard to take them out of the holder?

[JCJC]

Much the same as charging radio control models, the B6 charger above will do what you want and is common in RC, it runs from 12v (car battery or mains adapter [extra]). You may have to make up a cable from charger to battery pack, 4mm banana to.....

Manual: https://astecmodels....x-B6 manual.pdf

Depending on your batteries (AA's ?) you will need to set a charge rate (around 0.5Amp), not to high I would have thought. It is possible to find a 230v 'dual' version for approx £30.

JCJC's dad

[knobby]

Cheers guys, no its not hard to take them out but I'm making a 'kind of ' mini power tank. It would be nice to just ' plug it in' to something

[knobby]

Well ... the prototype "mini powertank' has been on test since 18:30 on my 4se, its been tracking with several mock goto's thrown in for good measure. Also a bit of manual up down left a bit right a bit!

Its now 22:45 and its still going strong.

It would still be nice to be able to charge it without taking it apart though ...

Edit : been out using the tour since 22:45 ,its now 23:30 and pack is dying!

So in summary 10 2500 mah nimh AA's provided 13 v ish for 5 hours with a mix of tracking, goto and manual slewing and its small and neat.

Pretty happy.

[knobby]

Posting a couple of pics ... all bits obtained from maplin

[keithatrochdale]

There is no problem charging them in series, been doing similar for years (NiCads prior to NiHms).

The charger I point out to you has an AUTO mode so you do not need to worry about charge rates etc.

As they are 2500mAh then it would be possable to charge at 1/10C (C= capacity) with total safety, but let the charger do it for you as it senses the battery state and adjust accordingly.

Just for info. the Maplin quick charger that charges these cells seperatly (and is often packaged with thses cells), charges at 2A. But if you look at the battery manufactures data they warn that it will reduce the number of charges considerably; so instead of 1000 cycles you can only expect half that at high charge rates.

Gina - charge any cell wrongly could lead to explosion, but NiHms are very user friendly and with an AUTO setting as suggested quite safe. You would be better worring about the LiPo batteries you put next to your ear when using you mobile phone. Now when they go up the only thing to do is cover them with sand and let them burn out, or chuck them in the sea!

[woodbob123]

All been said but what ruins batteries is the heat caused internally when charging, higher the charge rate greater the internally heat, so using a good auto charger will help but with out good ventilation will damage cells eventually, r/c packs are in a film and can pass a lot of the heat yours will have the box to insulate. So keep the charging rate down whenever possible.

[knobby]

Thanks guys ... what have i started ?

[keithatrochdale]

... r/c packs are in a film and can pass a lot of the heat yours will have the box to insulate.

Are you sure? Most packs I have seen over many years are ofter wrapped in foam, which is a very good insulator.

The AUTO setting will monitor the packs charge state and adjust the charge rate accordingly. This should keep heat to a minimum.

.

[JCJC]

We use a B6 charger as above, its amazing value and easy to use. Keith has it about right.

JCJC dad

[woodbob123]

Just being cautious my r/c days are long gone sure that new chargers are excellent, charging time is not critical so a slow charge would do the job and if available may be the best option..

[keithatrochdale]

Just being cautious my r/c days are long gone sure that new chargers are excellent, charging time is not critical so a slow charge would do the job and if available may be the best option..

Hi, indeed better to be cautious.

.

Most of todays chargers work in a completely different way to the early days. Charging then was worked out on a 16hour charge at 1/10C, ie fixed current and often they were only 500mAh packs. Todays chargers of the types talked about are very clever and sample the cells state to calculate the charge rate; they even calculate the number of cells in series. Some even push a small charge in and then reverse it for a very short time, IIRC this is called 'BURP' charging and is supposed to reduce heating. When charging NiCad and NiMh cells there are two ways to determin when full charge is reached, as overcharging rapidly shortens their life, heat and voltage. When full, heat is generated as the charge has no other place to go, alternativly the voltage can be monitored, as the cell aproaches full the voltage stops climbing, flattens out and then starts to drop. At this point todays clever chargers switch off.

NowdaysiLiPos (lithium polymer) are now more commonly used in R/C, especially electric models and they need a whole new system for charging. The chargers mentioned will charge them as well.

[knobby]

Just an update ... used the mini pack on Friday for about 4 hours quite heavily, trying to auto align several times with no luck. Did give the pack a good workout though ,and it was pretty cold out!

so looks promising.