This one?Snap
https://www.google.co.uk/search?q=HR+1234W+F2&es_sm=122&source=lnms&tbm=isch&sa=X&ei=Xl1SVcrhG8bzUpmbgOgD&ved=0CAgQ_AUoAg&biw=1360&bih=643#imgrc=QvUxEzEoxWqGpM%253 (https://www.google.co.uk/search?q=HR+1234W+F2&es_sm=122&source=lnms&tbm=isch&sa=X&ei=Xl1SVcrhG8bzUpmbgOgD&ved=0CAgQ_AUoAg&biw=1360&bih=643#imgrc=QvUxEzEoxWqGpM%253)
Bob
| Specifications for CSB HR1234WF2 Battery | |
| Voltage | 12V |
| Capacity | 9Ah (34W) |
| Weight | 3Kg |
| Dimensions | 151mm x 94mm x 65mm |
| Lifespan | 3 - 5 years |
| Type | Sealed Lead acid battery rechargeable highly efficient, leak proof and maintenance free |
| Warranty | 12 months |
| [size=78%]Declan[/size] |
Sorry Declan,
I some how miss read it.
Regards Howard.
Further tinternet searching produced this
http://www.hardwarexpress.co.uk/hr1234w-f2-csb-battery-12v-9ah-457-p.asp (http://www.hardwarexpress.co.uk/hr1234w-f2-csb-battery-12v-9ah-457-p.asp)
Specifications for CSB HR1234WF2 Battery Voltage 12V Capacity 9Ah (34W) Weight 3Kg Dimensions 151mm x 94mm x 65mm Lifespan 3 - 5 years Type Sealed Lead acid battery rechargeable highly efficient, leak proof and maintenance free Warranty 12 months [size=78%]Declan[/size]
Vnkiwi
Ohm's Law describes the relationship between the current, the voltage and the resistance in a circuit when current is flowing. There is no mention of a unit of time because it's not part of that relationship.
I've just Googled the word "ampage" and the only definition I can find actually describes what most folk would call "current". You can't describe a battery by its current - such a definition would be meaningless.
However if you wish to describe the capacity of a battery to deliver a current then time comes into the equation, in as much as the capacity is a measure of a battery's ability to supply an amount of charge over a period of time. If you drain the battery very quickly then the charge it contains will not be delivered for as long a period as if you were to drain it slowly. Its capacity is the arithmetical product of the current it can supply and the time for which it can maintain that supply. Imagine it as like having a bucket full of water. If you drill a small hole in the bottom of it then the water will drain away very slowly while a large hole will drain it much faster, but the size of the hole doesn't affect how much water the bucket will hold before you start to drain it (its capacity).
In the equation V x I = W the W value is the power which is being supplied to a load where the voltage across that load is 12v and the current flowing through it is 2.83 Amps. The battery could equally be a 0.6AH lead-acid battery or a 5AH LiPo pack; it's just that the latter will last a lot longer than the former.
None of this stuff is clever or mysterious, guys. If it really was rocket science then I'd have taken up collecting car numbers years ago. There's more basic information here http://www.modelboats.co.uk/news/article/but-i-don-t-understand-electronics/18054 (http://www.modelboats.co.uk/news/article/but-i-don-t-understand-electronics/18054)
Dave M
12v at 1 amp = 12W which can be delivered for 9hrs.
12v at 9 amps = 108W which can be delivered for 1hr.
In theory
9Ah means the battery can deliver 1 amp for 9hrs
or 9A for 1 hr etc. etc.
But this can vary depending on the Rate of the battery (10hr rate or 20hr rate) which is determined by battery construction and intended use.
I agree, battery capacity claims do border on the fraudulent and the result is a lot of confused and unhappy people when the battery does not perform as expected.
It would help if manufacturers agreed a STANDARD for battery specifications which included the RATE, but I don't see this happening anytime soon.
Some are better than others in this respect but there are a lot who make some very wild claims.
As you say, they are relatively cheap and make useful ballast in our application, but that is no excuse for poor/misleading advertising data.
Keep Happy.
Sandy. :-))
Well said, Monsieur!
Far too many modellers are fooled by those seductive capacity ratings, to the extent that some believe they can even run two brushless motors from one SLA battery and obtain an hour's sailing from one charge. If I've seen one Huntsman or Perkasa lumbering round a pond like a narrowboat, weighed down by a huge brick of a battery, then I've seen a hundred. It makes me weep. It takes a great percentage of the motor's power just to get the battery moving, never mind getting the model up on the plane.
Unless they are of the special high-current, deep-discharge "leisure" type
No-one seems to have noticed the 15min on the end. I'd hazard that at 34W per cell (from full charge) it will hit 1.67V in 15 minutes. But I think I'd be wrong somehow.
Regardless of that, lead acid batteries should be charged with volts until they reach their fully charged voltage. Then they can be trickle charged. If you get a correctly sized auto charger (eg. one for say 5-20 Ah batteries (12V of course) then it should just do the job without you worrying about it.
Probably better to get one that is slightly oversize than under - it won't overcharge as the cut-off volts are not dependent on size but chemistry. Undersize may simply not have the oomph to get the battery up to the cut-off volts, so it never fully charges or terminates. (I had one that was like that from a popular supplier on here - pos. Had to get a better one from Greece of all places, via ebay.)