charger rating vs battery capacity

[jdfs]

If I have a 800Ah charger that takes 8 hrs to charge a battery to 800Ah, and a 1600Ah lead acid battery, is the 800AH charger able to charge the 1600Ah battery to its full capacity given enough time? Or is the 800Ah charger not able to charge the battery to its full capacity at all? What negative effects if any(I assume sulfating?), does using a significantly smaller rated charger have when charging a larger capacity battery?

Also, are there any ill effects of using a larger capacity charger to charge a smaller capacity battery, for example a 1200Ah charger with an 800Ah battery? Thanks.

 

[alehman]

I've never heard of a battery charger being rated in Ah, and I'm not sure how I would interpret such a rating. Are you sure it's not rated 800A?

If you put too much current through the battery, it can be damaged.


Alan
----
"It’s always fun to do the impossible." - Walt Disney

 

[DanEE]

Ditto Alehman's post above.. your question does not compute.. chargers are spec'd by continuous duty current capacity.

We don't directly size charger capacity in relation to battery size in our DC Power Plants..

Chargers are first sized based on plant load, allowing for load growth, then adding the degree of redundancy (at least N+1) unless the customer specifies an even higher degree of redundancy.

Battery AH capacity to be installed is then computed based on plant load and customer specified run time.. The typical range we are asked to provided, generally is no less than 2 hours, and have a number of hospital sites requiring 6 hour run time.

If you have charger capacity so small that they are going into current limiting for an extended period of time, trying to charge batteries and at the same time support the DC plant load, you don't have enough charger capacity, nor most likely any redundancy if a charger were to fail.

If the chargers are not into current limiting, they are going to bring the batteries up to "full" charge period, assumming of course the chargers are properly set to the correct float voltage per battery manufacturer's specifications and ambient battery temperature.

We have a number of sites with Absolyte 100G33's installed (a 1600AH battery stack, since you mentioned systems in that ballpark) and, a fairly wide range of charger capacity, when again is computed based on plant load and, the redundancy requirements specified by the customer. While these size batteries can draw some serious current when the chargers come back on line after an outage, they taper back in time and pretty well take care of themselves.

If you have a really large excess in charger capacity, (as will typically be indicated by the chargers setting the low current alarms and inability to load share), simply shut off some of the excess capacity, but leave the chargers installed, ready to go, in case you loose a charger..

We have some sites in that situation, and we rotate the active chargers on/off line at maintenance visit intervals to make sure all are in good condition.

 

[IRstuff]

Generally, typical rechargeable batteries are charged at a fraction of their rated capacity, to prevent overheating and other deleterious effects arising from rapid charging.

So, while you might not instantaneously clobber a battery with one that's designed for larger batteries, you might definitely decrease its useful life.

And as Alehman states, you could also overcharge and damage the battery, depending on how the charger was designed.

TTFN

FAQ731-376

 

[cherry2000]

If you really wish to size the Battery charger (assuming that the A-H of the battery is fixed), refer to attached Template, developed for Lead Acid Battery, based on Charger sizing criteria from IEEE 946.

Caution : refer to IEEE 946, check all input data, modify the calcs accordingly. For any spreadsheet/software, the truth is : "Garbage in, Garbage put".

If the calculated value compares favorably with the Charger rating, then all is well.