Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[byfly]

Can  anybody tell me what exactly is the difference between NiCad, Lead Acid Gel and Lead Acid battery chargers. Why can't a lead acid charger be used with a gel battery and why can't a NiCad charger be used with lead acid etc. What would happen if I used a lead acid charger on a gel battery. I can't find any reference to the physics of the different chargers and what would happen if I used the wrong charger. Some expert views would be much appreciated

[boatmadman]

I stand to be corrected, but, my understanding is that nicad/nimh chargers work on current charge, whereas gel cell/lead acid work on voltage charge.

I do know for sure you cant cross charge successfully, in fact it may well be dangerous to try it.

Ian

[byfly]

OK, but why can't a gel charger be used with an ordinary acid charger?

[Peter Fitness]

byfly, I'm no expert, but it may have something to do with the charging rate. My lead acid charger charges at from 1 to 4 amps depending on the state of charge of the battery, whereas the gel cell charger charges at 500mah, or half an amp.
Peter.

[Tom_DK]

Can  anybody tell me what exactly is the difference between NiCad, Lead Acid Gel and Lead Acid battery chargers. Why can't a lead acid charger be used with a gel battery and why can't a NiCad charger be used with lead acid etc. What would happen if I used a lead acid charger on a gel battery. I can't find any reference to the physics of the different chargers and what would happen if I used the wrong charger. Some expert views would be much appreciated

Charging Leaded batteries is mostly done by keeping the voltage at same level (voltage x 1,4). The current can then be limited to 1/10 of the capacity if you want to make a perfect charge. Charging 12-14 hours is norminel. Of caurse you can also charge the battery at higher current without any problem.
You CAN also charge any NiMh or NiCd battery at the same data (voltage x 1,4) and current at 1/10 of the capacity for 12 hours. How ever you can also charge NiMh and NiCd between 5/10C to 3C (C = Capacity) using a delta peak principle. Delta Peak charging is done by keeping the current at same level and monitor the voltage. The voltage will increase during the charging and when 95% fully charged, the voltage will begin to lower (which is the delta peak point). Delta peak charging dosn't work on Leaded batteries.
Some advanced NiMh and NiCd charges also include a trickle charge function, when delta peak has been reached, the charger switch to trickle charge where the current is lowered to something like 1/10 to 1/20 of the capacity.

When charging with 1/10 C at 12 hours, you should not exceed the 12 hours and only charge for 12 hours when batteries are empty.

Regards,
Tom

[malcolmfrary]

A normal battery charger for car use consists of a transformer to reduce the voltage to an acceptable level, a rectifier to turn this voltage into DC, and a meter to let you know that current is flowing.  Current is "regulated" by the impedance of the transformer windings.  For a car battery, this current is OK at about 4 amps, and the system will self-regulate to an extent.  Using the same charger on an SLA which will normally be much smaller than a car battery will cause the battery to fully charge very rapidly.  It is more than likely that over-charging will occur, and the battery will give off gasses, hydrogen and oxygen.  A car battery with screw tops can be topped up, an SLA lacks this ability, so an over charged one is expensive ballast.  Charging any Lead acid battery at too high a rate can cause the internal plates to warp.  As there is not much space between the plates, this can lead to internal shorts, which is a recipe for disaster.
So SLAs need a charger that supplies the appropriate voltage at a current that is safe for the battery.
NiCads and NiMHs have different chemistry and internal construction.  Voltage supply is not important as long as there is enough, but current supply is, and needs to be regulated down to a safe level.  Again, overcharging damages the battery by boiling off the irreplaceable electrolyte.
The different families of battery give different clues to indicate a full charge to the charger, so the charger needs to have the right kind of sensing circuit, hence the differing types of charger.
As a general rule, long and slow is better than short and fast.  Not just with batteries, come to think of it.

[byfly]

O.K. All well understood however my lead acid battery charger has a trickle facility which produces a very small current. Therefore could it be used with a gell battery? I understand that I would have to time the length of the charge (ie battery capacity v charge rate approx') to prevent boil off, heatbuild up and overcharge/damage to the battery.
Also my Nicad charger tells me a max number of cells (10)and max capacity (4500mh) chargeable. I have aquired a battery (not sure what it was intended for ?a large electric drill) with 8 cells which has a capacity far greater than this, therefore, can I use my charger on it (I do understand it will take longer to charge) and will the delta peak function still work?

[Colin Bishop]

however my lead acid battery charger has a trickle facility which produces a very small current. Therefore could it be used with a gel battery?

It depends on what the current is in relation to the recommended current for charging the Gel Cell. If it's less that or equal to the recommended charging rate then that will probably be OK. However, if it is the case that the charger reverts to a trickle charge once the battery is topped up then the initial charge rate will be too high.

I have a Halfords automatic battery charger which charges at 7.5 amps in "car" mode and 1.6 amps in "Bike" mode and it has a Gel cell setting. The recommended charge rate for a gel cell is 10% of capacity so I don't think the charger would be very suitable for anything under a 12ah battery.