How & Why - Recharge Your Batteries (Dead / Low Battery)

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How & Why - Recharge Your Batteries (Dead / Low Battery)

Post by undysworld » Thu Jun 20, 2013 6:32 pm

I'm reading over another thread about how and why you should periodically recharge your batteries independently. It's tough to follow the pertinent info, as the discussion/s flow. So that others may more easily search the correct answers out, I'm quoting a knowledgeable forum member here. This is NOT a thread about charging problems, it's about recharging batteries. Please don't hijack this thread.

Why should you periodically recharge your truck's 12V batteries independently?
Jimm391730 wrote:The batteries (and other loads) are what defines the current coming from the alternator -- through the voltage regulator, the alternator current is adjusted to keep the ~27V output. If you were to turn on your headlights or other load, the additional current draw would make the battery voltage lower; so the voltage regulator tells the alternator to produce more current to make up for it.

In the daytime (and right after starting) the recharging of the batteries takes up most of the current from the alternator -- the ignition takes only a few amps. As the batteries come up in charge, their voltage does, too, so the regulator tells the alternator to decrease the current to keep the output voltage the same.

I wouldn't worry about the alternator's amps, unless the truck can't keep the voltage at 27V. This is why a voltmeter is important to monitor the health of your system. Any lack of current will show up as a reduced voltage. A voltage of 24-25 volts won't properly charge the batteries, and a voltage of 29 volts or more will be overcharging the batteries.

You can have battery problems even if you buy two brand new, identical batteries because they are NEVER exactly the same (although they will likely be closer than any other pair of batteries). One will have a little less capacity, and just starting the truck will have it drained slightly more than the other. Lead acid batteries will take LESS charge the further they are discharged, so that battery will never be charged as fully as the other (which actually is getting a tiny overcharge). The next time you start the truck, this problem gets compounded, again and again, and the batteries drift further than further apart in charge and capacity. Now in most trucks they are close enough together that this doesn't show up for years and then the owner says "well, must be time for new batteries". But all that is needed is the occasional independent charge to each battery; that is, put a 12V charger on ONE battery until it is fully charged, then charge the second battery in the same manner. This brings both batteries up to full capacity and "resets" the imbalance that gradually occurs. I do this with both my trucks about twice a year.
How often should you independently recharge the batteries?
Jimm391730 wrote: I do this with both my trucks about twice a year.
How do you independently recharge the batteries?
Jimm391730 wrote:It is REALLY simple -- just hook the red terminal from the battery charger to the positive (+) terminal of one battery, and the black lead to the negative (-) terminal of the same battery. There is no need to disconnect ANYTHING from the batteries first (although it doesn't hurt, unless you re-connect it wrongly). If you have two chargers, you can also connect the second charger to the other battery at the same time; however, I prefer to use the same charger as so to "top off" both batteries similarly.
When/How to Add Water to your Lead/Acid Batteries?
etoothpaste wrote:Watering is the single most important step in maintaining a flooded lead acid battery, a requirement that is all to often neglected. The frequency of watering depends on usage, charge method and operating temperature. A new battery should be checked every few weeks to determine the watering requirement. This prevents the electrolyte from falling below the plates. Avoid exposed plates at all times.

Exposed plates will sustain damage, leading to reduced capacity and lower performance. If the plates are exposed, immediately fill the battery with distilled or de-ionized water to cover the plates, and then apply a charge. DO NOT fill to the correct level before charging as this could cause an overflow during charging. Always top up to the desired level after charging.

Never add electrolyte as this upsets the specific gravity and induces rapid corrosion.

Source: courtesy of EToothpaste

The simpler it is, the more likely you will be to do it!