I am confused!?

[bbilly]

Hi,
Iv got a gel redflash starter batt. and a wet acid battery. During the winter I decommission them and put them in the shed and every couple of months give them a check with voltmeter and if necessary charge. My cheapy bosch charger has packed up and I need to buy another one. Are there any specifics regarding charging these batts. offline. Are cheapy chargers ok for the redflash which theoretically holds its charge for 2 years. Do i need a three step charger, a digital charger, 2 chargers?? Or a cheapy charger?

Thanks in advance

BB

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[johna]

I have been considering buying a Red Flash as a starter battery what has been your experience with the battery and what capacity do you have?

John

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[snowleopard]

if you use a cheapo charger, keep an eye on it and check the voltage. mine (11A charger) goes up to around 15.5v when the battery is full and it gasses like mad. ok for getting rig of some sulphation but not to be recommended!

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[Scubafill]

Have a look at the Clarke ATC12V charger available from Machine Mart
www.machinemart.co.uk
About £9.95 + vat

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[bedouin]

For keeping batteries in good condition at home I just use a cheap "automatic" model from Halfords. Automatic is good since it switches off once it gets to a certain level of charge so prevent you from damaging the battery.

These are not very good as the main charging device (because they don't get the battery to 100% charge) but I think they are fine for off season maintenance.

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[William_H]

The older style or cheap chargers are quite crude in that they rectify the AC from a transformer. The current going into the charger rises from zero to full current then back to zero at 50 times each second. Most rising once per cycle some full wave rectified types rising twice every cycle. This means that the peak voltage is a lot higher than the battery voltage can rise to, even though the average current into the battery can be quite modest. (you need a mechanical analogue amp meter to measure this average current) This means that when the battery becomes charged and it's own voltage rises the current will fall but there is still a part of the cycle when voltage is way above the battery voltage so some current will still go into the battery. The good news is that it will fully charge a battery while the bad news is that if you leave it on too long you will continue to boil the electrolyte until it is dead.
Now an automatic charger (like your engine generator) provides reasonably smooth DC so that with a voltage of 13.75 a good current will enter a flat battery but as the battery's own voltage rises to 13.75 volts the current will diminish to near zero. (current is a result of the difference between the charging voltage and the battery voltage)( you can't measure this difference however because the voltage of the charger is pulled down by the current flow in the internal resistance of the charger) Obviously the battery can never get to 13.75 volts just very close. This means you can leave it on for ever but will never fully charge the battery. The smarter chargers in the interest of quicker charging will charge at a higher current until the battery voltage approaches 13.75 volts (or thereabouts) then reduces the current to permit safe long term charging. Again it will never really charge the battery fully and can not be used for a furious de sulphating charge.
So please yourself but I always use the crude type charger for preference. Just don't leave it on too long. If you know the charging current then divide that into the Amp Hour rating of the battery. This will give you an idea of how long to charge for. regards will

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[bbilly]

Johna,
My worst nightmare is the wet batt. packing up and being stranded with a perfectly serviceable boat. So after weighing up the pros and cons of adding anothet wet battery, switches, wiring and securing the extra batt and keeping a small, bulletproof powerpack on board i decided on the latter so it's an emegency backup and is not connected and so far Iv never used it. Plans are for it to become the starter battery and when the current wet batt. is kaput replace this with a deepcycle for services so I can keep drinks nice and cold with a fridge. I researched quite a bit and the Redflash 700 (which fits snugly in the existing battery box with the std wet) provides enough power (theoretically but I am confident - in practise) to start my TAM22D (105hp 2000cc Turbo Diesel).
People have been very helpfull on the forum and I consulted the Oracle before deciding. There are differing opinions regarding charging the RedFlash on board see this thread:
http://www.ybw.com/cgi-bin/forums/showflat.pl?Cat=&Board=pbo&Number=591870&part=1

WillH
Electricity has always been an occult science probably coz I got thrown across a room by a shock as a child so I am very wary of it and probably in my subconcious dont want to know. Thanks for the detailed explanantion but I dont get how it works. As the redflash is my "last escape route" I want to be absolutely sure it is fully serviceable, so once a year I will recharge offline in the shed.

Scubafill,
Had a look at the device, do you use it to charge a gel battery?

Thanks

BB

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[William_H]

Sorry BBilly with the detail. The short answer is as with any battery give it some charge preferably every 2 weeks (don't know redflash) not too much but enough to ensure it is reasonably charged. Any charger will do but if it is a cheap one it is more important not to forget it and leave too long on charge. good luck hope you survive winter will


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