Now I may look like an idiot in a Stormtrooper uniform but as well as working as an extra on "Star Wars IV" I also have a Ph.D. in electronics, so let's see if I can help you with your battery problems.
Sealed lead acid batteries, otherwise known as Gel batteries, are used in many household items such as ride on toys, golf trolleys, invalid carriages, electric wheelchairs, computer back-up power supplies, rechargeable high power torches etc. etc. They can be used in any orientation, even upside down as they are sealed and can't spill in normal use.
If you buy one of these batteries - commonly made in the UK by Yuasa - to replace an identical battery that has failed then there is no problem, just connect and carry on using as before. What you must NEVER do however is confuse these Gel batteries with car batteries - the type that you put water inside, and you must certainly never ever use a car battery charger on this type of battery. It will blow it up before you can even think guarantee claim!
So how do you recharge Sealed Lead Acid batteries, and what are the most important points to remember?
First if you have a supplied charger for whatever item the battery is powering - use it before any other type of charger, but check first that it is working properly. If your charger is faulty it may easily be the reason why the battery needed replacement in the first place! Faulty chargers can ruin rechargeable batteries before you have time to blink.
If you have to use any other sort of charger then you first really need to go out and buy a cheap multimeter to check how the charge is going. These can be bought on eBay for well under a tenner.
To measure the battery voltage first switch on the meter and set it to a suitable voltage range - usually the 20Volt range. Most meters have three sockets for the leads to be plugged into. The black negative lead usually stays in one socket all the time and then the red positive lead can be plugged into a choice of two sockets. One socket is for voltage V readings and the other socket is for current Atests. If you plug into the current A socket and then try to measure the voltage you stand a really good chance of damaging the meter, AND possibly of damaging your battery too!
To actually read the voltage first disconnect the battery from any attached equipment and then put the meter leads onto the battery terminals - red to red, black to black. Then simply read off the voltage shown. The normal point at which charging a nominal 12Volt battery should stop is usually when the meter reads 12.87 volts. Yes, you can easily squeeze a bit more juice in but this may well reduce the life expectancy of your battery. There should be no problem leaving a correctly set up meter connected to read the voltage while your battery charges.
The current range on your meter is to measure how much electricity is going into the battery AS it is being charged. Unfortunately when measuring current the circuitry inside the meter will overheat if left connected for more than a few seconds, so you'll have to keep measuring and then removing the meter - inconvenient but necessary!
To measure the current going into or out of your battery set the meter to a suitable A range - usually 10A -and connect the leads IN LINE with the battery or batteries. So one lead goes to one of the battery terminals and the other goes to the charger or device that is being powered.Instead of this you could connect it BETWEEN two batteries connected inline if that is easier - what goes into one battery will automatically go into all the other batteries connected in series.
So to summaries, you connect one meter lead to one of the wires from the charger and the other meter lead to the battery itself to read the current. In the olden days you had to be extremely careful which way round all this was connected. Fortunately things are much easier these days! If you connect the meter the wrong way round you will just see a little sign before the numbers but the reading is perfectly valid.
To reiterate the meter is connected BETWEEN the battery and charger to check the charging current, and the meter is connected ACROSS the battery to measure voltage.
There is an excellent free guide to the use of different sorts of Gel batteries on the Yuasa web site called The Little Red Book of Batteries. Weearnestly suggest that you download it and then read it!
By the way we recently saw a chap being denied permission to take a unit powered by a rechargable Gel batteryas hold baggage in a commercial aircraft. We could perhaps understand if he was denied permission to take it into the cabin but this was to take it onto the aircraft at all.They actually made him remove the battery and throw it away! Most of these batteries are completely safe to take on aeroplanes. Why? They are actually used to power the avionics on commercial jets when there is no ground power supply, the plane probably had three 60Ampsizes of these batteries installed already! The ground staff obviously didn't know the difference between a car battery with its liquid acid and a sealed Gel battery, after reading this guide you will.
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Thanks, Rob.
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