I used the search engine looking for threads on portable charger viability, to no avail...so here goes my query:
My onboard shorepower charger recently went kerplunk (might be diodes, might be windings, who knows?), and until I either: 1) take it apart and ascertain what's wrong with it, 0r: 2) buy a new multi-step "smart" charger (if I can find one at a decent price, that is!), I am wondering about the eficacy of temporarily using a Walmart "Ship & Shore 15/10/2 amp" portable "marine" charger to charge my system while at dock. I see nothing in the documentation with the thing about any type of internal isolation, but that doesn't necessaily mean it doesn't have it. It's a $49 "marine" portable marine charger, so I figure it's gotta missing something.
My present system
: Bank #1
= 1 separate 12v 24 series 500cca starting battery; Bank #2 = 2 100 ah deep cycle house batteries connected in parallel. The two banks are seperated by 4-way batt switch. There is also one emergenncy 12v 24 series starting battery kept on a solar maintenance charge, and one emergency 12v deep cycle instrument battery on a seperate solar maintainer.
: At dock - 4 small incandescent lights (2 amp total draw or so); stereo (can't be more than 1 amp, I'd guess)...so 3 amp maximum total, or could be much less. All my water is manual pumps. And right now reefer unit is down for the count, so zero amps there
. Underway: VhF radio on scan standby; stereo; depth sounder (Hummingbird), Garmin GPS; very rare radar usage(simrad 18"); tricolor running lights under sail, powerboat running lights otherwise; no more than 2 cabin lights at a time, augumented with kerosene/oil lamps. That's about it. All sailing gear is manual. No reefer use underway or at anchor.(hey....not THAT kinda reefer!); 75 watt inverter for notebook computer. And VERY occasional use of a 150 watt inverter for charging E-Cell AA batteries.
In short, either at dock or underway, my electrical load isn't huge. Barely use radar underway.
What I would like to do, then, while at dock is to temporarily use that walmart portable charger. By temporary I mean I won't have charger online 24/7 while aboard like I would with my regular AC charger. I would go off charger, monitor the housebanks to 50 - 60%, put charger back online at 8amps medium setting(it has 15 amp maximum), then take charger offline again as it nears 100%. I would charge starter battery with it separately.
I can't see this format as that much different than being at anchor and using engine every 36 hours to charge batteries. The main thing is to keep that charger offline when not actually needed.
Would using this portable charger in only such on/off format be doing any damage to my 12 volt system galvanically...as the batteries ARE hooked up to my 12 volt wiring while shore-charging? Is this a no-no with a portable charger, due to some aggregate galvanic situation? I've never needed to rely on a portable unit before.
Truth-be-told, I would rather spend money on a new main, and a trim-tab self-steering, and things like solar panels than on a dedicated shorepower charger, if this portable will work...it is supposedly a 'smart-charger' and will automatically go into maintenance monitoring and then re-'step up' the amperage if it senses a load...it just isn't a multi-stage unit. bulk and all that.
Problem is: it's now been on for 7 hours on a 2 battery, deep cycle 200 AH, house-bank that started at 70% and after 7 hours at 8 amps it's at a whopping 78%!! Wow! And that's with NO load on household bank at all. Been using headlamps! I could switch to it's maximum of 15 amps, but I always thought that too much amperage can kill a battery if their is no load on it.
I realize it takes far longer for the last 20%, but it hasn't moved from 78% for HOURS now! Bad purchase?
Anybody have experience with these silly Walmart portable chargers? I just bought it last night. It's a Shumacher "SpeedCharge" SSC-1500A. Ha ha...."speedcharge"!! Yah, right!