How to determine polarity of dead battery

[stugodwin]

I have a rechargeable battery for a bath-lift chair. Manufacturer was Merlin Bathlifter - now defunct.

I have lost the charger that came with the battery.

Only indications on case are as follows:
Voltage: 12Vdc
Rating: 2.1 Ah
Charge period: 8 - 10 hours

Battery is a sealed unit. Charging port consists of a receptacle about 1/2" deep, with a center post, that appears to accept a standard charger/power supply plug.

I need three pieces of information:
(1) What should be the rating of the charger to be used? I.e, what voltage, and how many mA?

(2) How can I determine the correct polarity? I have a gadget that will allow me to change the polarity of the charging current, once I determine what it should be.

(3) Can anyone direct me to a site that would discuss this in detail?

Thanks

stugodwin

 

[Taylortwocities]

Do you have a multi meter / volt meter? The battery may still have enough of a voltage in it to show polarity, but not enough to operate the chair.

Please take photos of the battery, use macro so we can see any engraving/markings near the battery terminals. Then post the pics on here

 

[YorksSparks]

Charger should be 12V - that's what the battery is!

Regarding the charging current - theoretically if it was to charge in 1 hour it would need to 2.1A (2100mA), but seeing as it says 8-10 hours then I would suggest either 2100/8 or 2100/10 ~= 250mA or 210mA.

What I would say is that the battery itself may show a maximum charge rate, in theory you could give it 2.1A for 1 hour but some technologies don't like that sort of intensive charging - it just shortens their life.

With respect to polarity - the general convention is that that the centre post/pin is +ve whilst the sleeve is -ve (or ground, depending on the system).

 

[empip]

???

http://www.medisave.co.uk/merlin-bath-lifter-spare-battery-for-models-before-52000-p-3890.html

Q. "Hi can you advise of the lifespan of this battery as the one I have does not seem to be recharging?"
A. "Hello. The manufacturer advise that as long as it is used correctly, it can have a lifespan of 2 - 3 years. The warrenty of the product is 12 months. I hope this is of assistance. "Asked on 06-03-2010 | Answered on 08-03-2010 by LS Faq No: 3299

Q. "is this a 12 volt 2 1 AH rating battery? I want to be sure I have the correct one. Thanks"
A. "Thank you for your enquiry. The manufacturers do not have this information, they purely work off whether the Model was manufactured before May 2000 (they have a single connector) or after (They have a double connector). I hope this information is of assistance."Asked on 03-10-2009 | Answered on 06-10-2009 by Matthew Lee

A charger :- http://www.medisave.co.uk/merlin-bath-lifter-battery-charger-models-p-3906.html
No specific info. re' the charger.
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[Taylortwocities]

Just noticed you are in the wrong forum.

You should be in Outside of UK as you are in USA.