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post #1 of Old 05-18-2019 Thread Starter
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Shore power chargers don't make any sense to me ...

I figured I'd start a new thread for this. It's a topic related to my batteries being dead but a bit standalone.

I've found a supplier that can get me Firefly Oasis batteries in a reasonable time frame, so I'm planning to go that route.

As a result, I need to replace some of my charging infrastructure, as it's old, not designed for anything other than FLA, and not programmable. FYI: I'll be replacing my alternator, but that's not really what I'm confused about.

The first thing I'm noticing is that a lot of these programmable chargers don't seem to really be programmable. It's tough to get details, but (as an example) the FF batteries don't require float charge, and the manufacturer recommends that you don't float them. I can't find any confirmation for any of the vendors I've checked that it's possible to disable float charging. To make matters weirder, the vendor recommends floating at 13.4v if you do decide to provide float charge. The chargers I've found don't seem to provide any way to adjust the float voltage.

Next, size recommendations. Given that my house bank will be about 300AH, I'm seeing most recommendations to buy a charger of at least 30 amps. This is ridiculous to me. If I'm plugged into shore power, it's going to be plugged in constantly. 10 amps seems perfectly fine since all it has to do is keep things topped off. Hell, the only thing on the boat that draws more than 10 amps is the windlass. I think if I turned on everything else all at once I might barely exceed 10 amps. I'm wondering if these sizing recommendations are based on usage patterns different from mine? People who make popcorn off their 12v system? Or people who rely solely on shore power for charging and therefor need fast charging between trips? (I have 300w of solar and am planning to upgrade my alternator so ... ?)

I'm kind of sick of talking vendors ... I usually get them trying to push stuff that feels massively oversized, and when I resist they say things like "what if you need to run an electric chainsaw off your inverter?!" (note, this is also a major factor for why I'm doing the work myself ... if I could find someone local that I trusted to do the work correctly and not sell me stuff that I didn't need, I'd probably pay to have the work done)

I'm also frustrated with product offerings. When I get down to chargers in the 10A range, they seem to be hack-jobs with a NEMA 5-15P plug on the end, as if any shore power pedistool takes that (the cable wouldn't be long enough either).

The most promising unit I've found so far is the Blue Sea 25A unit, which seems to have excellent programmability. It's very expensive though ... I guess if I'm going to dump the $$ into the FF batteries, it's worth it?

I guess this is as much a rant as anything else ...

Update: here is the information I'm using to plan the charging system:

Last edited by BillMoran; 05-18-2019 at 05:00 PM. Reason: Add document link
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