Battery Chargin Questions!!!

[Bandit1317]

So we have some genesis NP18-12B batteries and we are not sure what a safe amperage for charging is. also what is the harm in using a higher amperage than recommended?

[F22Rapture]

Originally Posted by Bandit1317

So we have some genesis NP18-12B batteries and we are not sure what a safe amperage for charging is. also what is the harm in using a higher amperage than recommended?

2 Amps is "best" for those batteries, but can handle 4 as well. Do not try to charge them at 6 Amps as you will damage the battery.

Also, be extremely careful to always store your batteries in a charged state, and charge them as soon after being discharged as possible. Failing to do so will damage your battery. I just had to take one of ours to be recycled today because of this.

An explanation to your second question:

If we try to charge the batteries too fast, with a large charger, then they will not become fully charged. Only the surfaces will be charged. Deep inside the plates they will still be in a low state of charge. This causes the "insides" of the plates to sulphate up (a phenomenon usually associated with the surface of the plates).

"Surface charge" also has further consequences.

Remember Peukert's effect? If we instantly start to discharge a "surface charged" battery then we are effectively discharging just the surfaces of the plates. This means we are effectively discharging a smaller battery (think about it). As we are discharging a smaller battery with the same discharge current then the Peukert corrected discharge current will be much higher (again think about it). Thus Peukert's effect will be higher immediately following a charge. And the faster the charge was put into the battery, the higher Peukert's effect will be immediately following the charge cycle.

This means that discharging a battery immediately after charging (whilst there is still some surface charge present) will give us less available power than waiting for the surface charge to permeate deeper into the plates. If we wait some time for the surface charge to permeate deeper into the plates, we will get more available power from the battery.

...

Surface charge can also cause chargers to terminate the acceptance cycle too early and go into float charge well before the batteries are actually fully charged.

http://www.smartgauge.co.uk/surf_chg.html
http://en.wikipedia.org/wiki/Lead%E2...nd _discharge

[DonRotolo]

To expand on the above:

A Lead-Acid battery works with a chemical reaction between (what else?) Lead and Acid. In this case, Lead Oxide (PbO2) and Sulphuric Acid (H2SO4).

There's a bit more detail than I mention here, but when the Sulphue atoms move from the acid into the lead plate, you get PbSO4 (Lead Sulphate) and the acid becomes 2H2O (Water), and a release of electrons. Those electrons are your electricity coming out of the battery. Add electrons (= charge the battery) and the reaction reverses.

The problem is that the chemical reaction is not 100% reversible, and the longer the Lead Sulphate has to form crystals (= sitting not fully charged) the more difficult it becomes to convert the Lead Sulphate back into Lead Oxide. And so, your battery loses capacity, and cannot be fully recharged any more. So a battery sitting discharged gets ruined.

The charging process also generates heat. Charge too fast and you get too much heat, which hurts the battery.