Elk power consumption

[mikefamig]

From the symptoms you described previously about your problem with the P212S and the 18Ah battery, I strongly suspect that the P212S was bad right out of the box.  I don't think that the battery caused the failure, although we have no way to know for sure.
 
Elk's description of the charge ramping doesn't tell us much.  It's normal for the current to ramp down as a SLA battery charges.  Some chargers actually ramp the current up a bit at first, until certain conditions are detected, then ramp it down.   Either way, the charging circuit has to limit the current so that it does not exceed the maximum permissible rate.   Larger batteries can handle larger currents, so in general, that should not cause a problem.  Using too small a battery is the condition that would worry me.
 
It would be nice if Elk would provide an explanation as to why they set the maximum battery size at 12Ah.  Digger may be on the right track that it has to do with charging time and the NFPA requirements.
 
But lacking any further information, I would be hesitant to exceed the maximum spec.  Elk had some reason for setting it, and without knowing the reasons, it's hard to say whether there would be any risk of damaging another P212S or the battery if you exceed it.   Theory says it should be ok, but I'd still hesitate to do it without knowing more.
 
One of the things I would like to do one of these days is to monitor the voltage and current to the battery on a P212S and see how it varies with battery size. 

[SIZE=11pt]Answer from Elk:[/SIZE]
[SIZE=11pt] [/SIZE]
[SIZE=11pt]The ELK-P212S Power Supply battery leads have the ends to accommodate the F1-Faston 187 Battery Tabs. The ELK-12120 is the largest AH Battery in the ELK Product Line with the F1-Faston 187 Battery Tabs. The ELK-P212S is a trickle charger and should be able to recharge up to a 12 AH in a reasonable amount of time whereas larger AH for example the 18 will take a lot longer to recharge. It is for this reasons (F1 Faston 187 Tabs; and recharging time) we suggest not using a battery larger than 12 AH.[/SIZE]
 
I received the above from Elk and it agrees with what Digger and you have been saying adding the point about the connectors on the battery posts. I think that I'll do my stanby calcs and use whichever battery serves my purposes.
 
Mike.

 

[RAL]

The size of the Faston connectors on the P212S vs what's available on different size batteries is something that hadn't occurred to me.  Makes a lot more sense now!

 

[Del91574]

The size of the Faston connectors on the P212S vs what's available on different size batteries is something that hadn't occurred to me.  Makes a lot more sense now!

Almost all the larger batteries, especially those with lugs and bolts, generally come with faston tabs in addition to allowing the connection of rings.
 
The charging circuit is part of the equation.