Rechargable batteries

PowerSlapper

PowerSlapper

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I have a little problem that I hope someone can help me with. I am always running out of "D" and "C" cells for various gadgets which I keep onboard "Jules' Quest". This usually happens at the most inconvenient times and leaves me rather frustrated. I am afraid the duracell bunny is not doing it for me so I thought of buying some rechargable batteries and a charger but I cannot find a 12v operated charger for "D" and "C" cells. There are plenty of 240v operated chargers but I really need a 12v one. Any suggestions as to where I could look?

Unfortunately none of my gadgets run on 12v so I cannot connect them directly to the boat's batteries.

Also what type of rechargable is recommended? NiMH or Li-ion? The batteries will probably be flattened and recharged many times and will need to be suited to fast discharge and fast recharge.

Jules
 
Try Maplins.
Most people use NiMH these days, but your question will probably kick off the usual techie debate about the relative merits of the different types.
FWIW I understand that fast recharging is likely to greatly reduce the life expectancy of the batteries.
 
[ QUOTE ]
I have a little problem that I hope someone can help me with. I am always running out of "D" and "C" cells for various gadgets which I keep onboard

[/ QUOTE ]

D and C cells eh! Now, not just yer average rechargable A and AA batteries for yer average handheld GPS etc. Now I wonder what "gadgets" you have onboard that use such large batteries? /forums/images/graemlins/wink.gif Must be very "frustrating" /forums/images/graemlins/frown.gif




















I'm smelling a "Rat" here /forums/images/graemlins/grin.gif
 
For NiCad or NiMh batteries all you need to recharge on the boat is a holder for the battery or several holders in series and a suitable resistor to recharge off 12v.
The resitor value is given by the voltage divided by the current. (in amps).
The voltage being dropped by the resistor is the number of cells in series multiplied by 1.2v ( for each cell) subtracted from the supply voltage 12v or 14 volts with battery on charge.
The current is the charging current. For safety of cells at most thios is 10% of the Amp hour capacity of the cells. So D cells might be 4AH so .4 amps for 14 hours is the safest charge rate. You can charge faster but the 10% rate is safe to leave on charge long term without cooking the cell. Wheras if you charged at 1amp you would have to disconnect after 5 hours or risk overheating the battery. This simple recharge method has no auto turn off.
Finally the power rating of the resistor is given by voltage multiplied by current. So for 4 cells the voltage dropped across the resistor with engine running is about 9volts multiplied by .4 amps is 3.6 watts of heat dissipated by the rsistor. So buy a resistor of at least 5 watt rating preferably 10 watts and yes it may get hot. In the case of a resistor the watt rating is the max it can handle before melting it the voltage and current that determine how much power it dissipates unlike a light bulb. if you can cope with longer recharge times I would suggest you reduce the current to 50% of the max 10% current. Resitors come from Maplin RS etc and are very cheap.

As for Li-ion batteries they are far more fussy about recharging and require a very accurate voltage source so buy a charger for them.

good luck olewill
 
I use rechargeables whenever possible and use mains rechargers via a sine wave inverter. On a boat of your size and power, you would benefit from a decent inverter onboard but do make sure that it is genuine sine wave, not modified sine or anything else as they can and do blow things up.
 
Major consideration

Rechargeable cells usually have a slightly lower terminal voltage than disposables.

This means that your various gadgets may run a little slower than usual, also they may not last as long per charge as with Duracells. Hopefully this combination of slower running for a shorter duration will not lead to further - ahem - frustration.

Even if you have a rapid charger and can swap batteries quick, you may lose your place.

On the otherhand, some equipment - especially motor driven - is fine with a higher voltage. Some motors will go mind 'numbingly' fast at 12V. Some electrical 'hobby shops' sell false arrays of cells that you could substitute into the battery compartment and connect direct to 12V.

AWSOME!

Forget the Duracells, that little rabbit would be rampant with 12V up it's jacksie!
 
I have seen adaptors so that "AA" type Cells can be used when "D" or "C" type size are required. The capacity will be reduced but it allows you to standardise on the cells for the various gadgets and to have one standard charger and you can get 12Volt chargers for "AA" type cells
I have standardised on "AA" NiMh and I have even had my HH VHF repacked with NiMh when the Ni Cad failed

I don not think you can get "AA" ,"C" or "D" cells in Li-ion as the voltages are not compatable.
Lithium-ion batteries have a nominal voltage of 3.6 V and NiMh have a nominal voltahe of 1.2 V
 
Re: Rechargeable batteries

I don not think you can get "AA" ,"C" or "D" cells in Li-ion as the voltages are not compatible.

It is very difficult to buy individual Li-Ion cells in anything other than made up battery packs mainly for safety reasons. The pack has to incorporate overcharge protection as the cells can otherwise precipitate Lithium which is a hazardous material, and over-discharge protection which they are susceptible to damage from (forgotten the exact figure but Li-Ion packs only discharge to something like 20% capacity for that reason).

If you pull a pack apart (which I don't actually recommend you do) you will find the protection circuitry inside it.

John
 
Edit

YUP, Rechargeables only 1.2V instead of 1.5 or 1.6 for primary cells.

That means your equipment would run 25% slower using re-chargeables.

Enough of a difference to notice I would imagine.
 
Like has been suggested already, Maplins have a charger which does Ni Cads or Nimh in all the sizes including C and D. They call it Map Universal Charger - it's about £40 and does mains or 12V dc.
 
you could try overlander (.co.uk, I think). Nicads have the possible advantage that the power drop off is later, but more pronounced than a normal battery, though Nimh is becoming more popular in some areas because of a slight weight advantage. You can get specialist fast chargers that will discharge and recharge them in.. well 20 minutes. Poly-lithium are much much more unstable in fast charge situations.. in fact fire and explosion seems a real risk.
Also try local specialist hobby shops like plane/boat/car where fast recharging is a norm. Didnt check where you are based, but hobbystores,Als hobbies,sussex model centre. just check the charges would do your size batteries though, and depending on the sophistication , cost from £10 to £100+
 
[ QUOTE ]
check the MaH

[/ QUOTE ] Just to be pedantic, as I'm in that sort of mood, that should be mAh.

It is good advice though.

Personally I'm not a great fan of rechageables in place of alkaline, or even Zn/carbon, batteries for several reasons.

<ul type="square">[*] They have lower capacities than alkaline ones (That bunny will run for much longer than his NiMH brother) [*]The voltage is lower so that may affect some equipment [*]They do not hold their charge for anything like as long [*]They do not like being left discharged or even partially discharged [*]What a fag it is to have to recharge them. Much simpler to use disposables, just bin the old one and fit a new one. [/list]
 
Does Anne Summers not sell rechargeable "gadgets" that you can get a 12v charger for?

/forums/images/graemlins/blush.gif not that I wud know anyfink about that sort thing /forums/images/graemlins/blush.gif

That would save you finding summat to charge the batteries.

/forums/images/graemlins/laugh.gif
 
[ QUOTE ]
Personally I'm not a great fan of rechageables in place of alkaline, or even Zn/carbon, batteries for several reasons.
They have lower capacities than alkaline ones (That bunny will run for much longer than his NiMH brother)

[/ QUOTE ] Is that the case nowadays? Back a long time ago, Mallory Duracell used to be specified as 750mAh in AA size, compared to 500mAh for typical NiCad of the day. Of course nowadays AA rechargeables are over 2000mAh - but I don't know what modern alkaline AA would be.
 
A recent pub conversation is repeated here.

rechargeable AA or AAA cells seem to work well for a short time. For example in a Kodak digital camera we were able to get over two hundred "flashes" with the camera before the batteries run down.
However if left for more than a few days the cells seem to self discharge. These were 2400 m batteries and brand new of a good make
My other Kodak camera ( SLR ) uses a Lithium Iron call (dedicated) and this seems to last for 4-6 months without discharge.

Finally many "garden solar lights" actually use a rechargeable AA battery as the power source.

Saw three such on the back of a boat where the fenders were stored and asked why - answer fitted with 2400 m batteries, they last 8 hours as riding lights, and the other two were used to recharge his battery razor!
 
OK ... best place is to find a Radio Control Model Shop. They have all sorts of field charging items designed to run of 12 car batterys.

I have a 9.6v and 4.8v output charger which has battery carriers fitted for 4 and 8 cells etc. - plus standard pin plugs to fit VHF HH's etc.

The cells - get them from maplins ...... NiMH or Lion .......

There are various manuals for items that say do not use recharge cells .... I ignore that and have had no trouble at all. Some will say that items can be voltage sensitive ... yes - but I've yet to find any that don't respond to recharge cells ...
 
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