DIY Doctor UK DIY Forums

hi guys. its been a while.last time on eric helped me with my garden pond pump wireing.heres a new one to ponder,have now got an allotment no electric,but have come across 2 batteries from a mobillity scooter,they are rated at constant voltage charge cycle use 14.5v at77 degrees and voltage regulation on standby 13.6-13.8 at77 degrees. now what i would like to know is there any way of wiring them up to run a light of any discription.would the light have to be of a car for example.any help would be much apprieciated, any ideas guys, cheers ian.

I would say you have two options as far as lights go either florescent for caravans and boats the 2D is about the best these will be between 8 and 21 watt and will last a reasonable time. Second is 12 volt LED spot lights these are about 3 watt will last for weeks but not too bright. I would not use tungsten bulbs as they use too much power and need spot on voltage.
Any lead acid battery will suffer from sulphating of the plates if left discharged for any length of time so I would recommend you recharge once a week even if not flat.
Always store in charged state opposite to NiFe or NiCad which should be stored flat but with NiCad there is also a issue with crystal growth when stored flat so never quite know which way to store them.
You have what are called “traction batteries” which are designed for deep cycling so are ideal for what you want. Batteries not in use should be charged at least once a month and the charger may be of two types constant current or constant voltage the latter is cheap option and will take about 24 hours to fully charge and I think you have that type but you can leave on charge all the time without having to do anything.
The constant current normally have two charge rates and will boost charge up to 80% charged and then float charge for last 20% these will take about 6 hours to fully charge and normally have some indicator to say charged often there is a fixed time for float charge and if left on the charger after a month will be going flat again and rely on being disconnected and re-connected again to restart the charge. You will see this type also used with NiCad drill batteries the smaller ones sometimes use battery heat to sense when the battery is charged as when electrical energy is converted to chemical energy it produces very little heat but once battery is charged then no longer is it being converted into chemical energy but it is converted into heat instead and it uses this to sense when charged sometimes this means the charger has more than two connections as the third goes to heat sensor.
I tell you this so you will not disconnect any battery sensor which is used.
My mothers scooter has all the electronics for sensing charging built into scooter quite a pain as whole scooter needs plugging in not just batteries.
You can make a battery charger but in the past I have used a CB power supply as they are regulated and will not over charge the battery. If your into some simple electronics you can also make a unit to add on to standard battery charger to stop it over charging and to give some indication to if battery is charged.
Florescent lamps for caravans and boats use a switch mode system which will correct for the voltage being high to start with and slowly decaying some are better than others look at the voltage range good ones will do from around 11 volt to 13.8 volt you could use car bulbs but these are designed to run on 13.4 volt and will be dim when used on a battery which is not being charged plus use more power than discharge types.
I am not sure on tolerance with the little spot lights using LED’s I would not expect any problems but I would not use tungsten halogen stop lamps as both under and over voltage will reduce their life and they use too much power.
I hope that helps
Eric

cheers Eric,This helps quite a bit,will give both a try and see witch one works best for job,again thank you.