Lots of discussion last year on battery power for stokers. Intent here is to provide everyone with some practical hands on accurate data for system design purposes, especially battery capacity. The Assessment #1 noted in the subject is based on a pure load with 1.00 power factor. Assessment #2 in the future will be run on a Pocono with a power factors less than 1.00.
Caution here: I am long winded. IMO the devil is in the details for a good assessment. And for you flooded battery experts, the detail I provide may be boring to you...intent though is to help newbies as well.
I think there was general agreement that for the Coal Trol and phased motors that the LL's use, a pure sine wave (PSW) inverter was needed. I closed in on a 600 watt cont/1000 watt surge 12V inverter made by Samlex, Model PST -60A- 12A. The Poke and CoalTrol has successfully run last year with this inverter for 3-4 hrs will no ill noises, hums or excess motor heat up as far as I can see. Motors spool up from a dead start seems to be the same as on commercial power.
Batteries chosen were qty 4 225 amp hr 6V deep cycle golf cart batteries made by Crowne (CR225) . I've heard good things about Trojans and Crowns with Crowns a bit more economical to purchase. There is tech support at Crown. They will provide a direct e-mail to tech support . Wow.
The batteries were configured into a 450 amp hr 12 V config. The battery hook up was such that each pair of 6V batteries had an equal length of wire during charging or battery drain to ensure best effort charging or draining on each battery. Goal is to minimize the need to do equalization. 6 gage cables were used, no battery to battery cable was more that 1 ft long. PM me with your e-mail if you want the hookup wiring used.
A three stage charger took the batteries up to a 100% 14.42 volts. At that time the charger was removed. The batteries were left for a day to let the voltage go down and the voltage inverter installed. Point here is that the batteries in no uncertain terms were 100% charged. This may not be practical in daily emergency use as the final 20% of charge to top the batteries off to 100% takes a long time (HINT: more reason for an oversize battery capacity)
My experience is that the LL Pocono (2 convection motors) takes 160 watts @ ~.59-.69 PF (Kill-A- Watt measured) @ a Coaltrol ~40% fan speed , I'm running a constant fixed 22-25K BTU/hr, suggesting that a 80-90 % fan speed is never needed (The coal trol has a logic that can do this 24 hrs a day) . To simulate the LL @ 160 watts I used a 100 watt flood light and incadescent 60 watt light bulb. Actual Kill-A-Watt measured voltage on the inverter was 167 watts @ 1.00 PFand 59.9 cycles per sec. Again, there was no consideration in this test for the ~.59-.69 PF (I can't remember what PF I measured last year) that the LL Pocono creats.......a baseline pure induction test was done at this time.
The inverter was run in three hourly segments to get open voltages. Waited 2-hrs between segments to let the batteries rest so the free (unloaded) voltage would stabilize.
Plan was to run the system for 12 hrs, pretty much what could be considered a long night with the expectation that a generator could recharge the batteries during daylight.
Start...12.72 battery free voltage, voltage was 12.35 V under the 167 watt load @ inverter terminals.
After 5 hrs cumulative running......inverter intentionally shut off, wait 2 hrs, battery free voltage 12.61V
After 9 hrs cumulative running...inverter intentionally shut off, wait 2 hrs, battery free voltage 12.47 V
After 12 hrs (test end) cumulative running ...voltage under load @ inverter terminals was 12.02 volts, inverter was then intentionally shut off, wait 2+ hrs, free battery voltage was 12.32.
Assessment : It seems that about 14 amps of power is needed to power the 167 watts (P= ~12.4V x I) . Add to that the inverter efficiency of ~85% gives an amp pull of 14/.85 = 16.5 amps. There #'s are approximate so don't yell at me toooo much ..
A bit of a important discussion. Each pair of batteries exceeded their rated 225 amp hr C/20 capacity by ~ 5 amps (16.5 - 225/20) . This means that roughly a 50% depletion voltage would be somewhere around ~~12.15 -12.2 volts (see internet data) ........the test data shows a post test free voltage of 12.32 volts which suggests the batteries were nearing a 50 % charge depletion. Looking at it another way , 16.5 amps consumed x 12 hrs = 198 amp-hrs, which is pretty much a bit less than 1/2 of the 450 amp-hr capacity. So the theoretical depletion voltage vs the actual charge used kinda matches up.
Summary: All this pretty much suggests that to comfortably run a LL Poke for 1/2 day non stop with no human attention (ie: changing batteries during the night or interim battery charging) at a moderate convection fan speed requires a fairly large battery system. You can go to a much smaller amp-hr capacity battery system though consider that your "under load" voltage at the end of 8-12 hrs may cause the inverter to auto shut down around 11 v or so. This end voltage drop is difficult to predict.... my system saw my voltage drop was something like .3-.4 v between load and no load for only 167 watts. This delta increases as the load wattage increases or the amp capacity decreases.
Hope this helps coalies design their systems ...and again apologies for my level of detail. Also, I'm not perfect so please excuse any details I missed. I'm always open to constructive improvements that will make my next PF based test more accurate.