Yippee! Charging The Lithium Polymer Beast

[SnowDog]

Ok Jeremy,
Just pulled the trigger on a charging setup: 24+ PSU from you and an iCharger 306B w para board. I also have 2 AC680s and parallel boards and cords for all. Ready to push some Amps! Only thing missing is a "field" supply. Don't have 110 or a generator (Cody, what's up with that pipe dream gas power station?! ha) so a Deep cycle battery seems to be the ticket. Any recommendations? Ratings? Prices? I'm planning on using one of the 680s to charge the deep cycle (when it needs it, which sounds like won't be that often). Any suggestions for "closing this charging circuit" are welcome. Thanks

A deep cycle marine battery like this one: EverStart MAXX-29 Marine Battery (or something similar) should work pretty good for field charging.
(at least, it works for me).

 

[Steve_B]

One thing to bear in mind with any lead acid battery is that when you pull high amps from them you do two things:

• You reduce the Amp hours available from the battery
• You shorten the battery life

Most people reasonably assume that if you have a 125 amp-hour battery and you pulled 125 Amps from it it would last an hour.. seems logical.. No?. The reality is that it would reach it's safe discharge limit in about 15 or 20 minutes!

The reduction in Amp hour rating is a function of the battery's Peukart number. There is a online calculator here that tells you what you will really get out of a battery at your required discharge rate: http://www.csgnetwork.com/batterylifecalc.html
if using a 306B charger at max capacity then you would pull 30 Amps from the battery which would half it's Ah capacity (from 125Ah to 65Ah in the case of the MAXX-29). It would go from fully charged to minimum safe discharge level in about 1.5 hours, maybe enough for five or six LiPo charge cycles. If this is enough totally depends on how big the batteries are that you are charging and how fast you charge them, but you might flatten the lead acid much quicker than you ever expected.