Any input on Noco's BLSOLAR5 5-watt solar auto battery maintainer?

goffredo

Hey gang.  I've got an Eurovan camper, and for the auxiliary battery, I use a 50Ah Optima 34M AGM.  We park the van over the winter, and I removed the aux battery and keep it in a corner of my house so it isn't subject to freezing temps.  I understand it's safe to keep this indoors because AGM batteries don't emit gasses.  I'm looking for something to keep it charged, and I came across this Noco BLSOLAR5 5-watt solar charger: https://no.co/blsolar5, it's $50 bucks on Crutchfield free shipping.

I figure I can stick the solar panel in a window, connect it to the battery, and forget about it until next summer.  My concern is that its specs indicate "1.2 - 20Ah" for Battery Capacity, and my Optima 34M is 50Ah (C20), but then the specs go on to say "Maintains all battery sizes" which kind of confuses me.

Does this sound like it can do the trick?  Or is it underpowered, and I'd be better off just getting one of their "genius" AC chargers and charging it once a month? 

The BLSOLAR5 also appeals to me because it appears during the summer that I can plug it into the cigarette lighter of the Eurovan, and it will help reduce the aux battery consumption a smidge when we're camping.  We usually camp in the desert, so plenty of sun, and we typically drive the van every couple of days, and we only rarely have an issue with the aux battery getting low, such that we don't really need a full blown multi-hundred-watt solar charging solution yet ... so hopefully this guy can serve double-duty to maintain the battery during winter storage, and give us a little extra boost during actual camping trips during the summer.

mcgivor

You would probably be better off fully charging the battery and leaving it in a freezing environment. The self discharge would be so low with slim to no chance of freezing https://www.optimabatteries.com/en-us/experience/2013/12/can-batteries-freeze just recharge when temperatures rise.

Estragon

I tried a small solar maintainer panel on my sailboat, but found it discharged the battery in the dark.  That could be solved with diodes, but as Mcgivor notes, self discharge is pretty minimal in cold temps, and a fully charged L.A. battery won't freeze until extreme cold.

goffredo

Interesting -- I had always heard (only anecdotally) that cold is bad for batteries, but as I read up, it seems cold is only bad for not-fully-charged batteries.  Sounds like I'm best off spending my money on a decent AC battery charger, and just check and make sure it's fully charged every month or so.  And plopping it in the basement where it will keep cool.

That BLSOLAR5 panel just seems too dinky to do anything useful.

mcgivor

The cold retards the ability of the battery to supply current, once warmed up it will return, the reason automotive batteries are rated in cold cranking amps. Storing disposable cells AA, AAA etcetera in a freezer will extend the shelf life for the same reason, by slowing down the chemical reactions which causes self discharge.