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Small Cabin Forum / Off-Grid Living / Faster battery charging possible
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groingo
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# Posted: 18 Jun 2014 23:01 - Edited by: groingo
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I charge my deep cell atteries via a Schumacher automotive battery charger and generator
but soon noticed how quickly the charger reduces charge in a very short period of time so I got to wondering and writing down information and discovered a pattern which showed that the charger was reducing the charge rate too quickly.

Contacting Schumacher I spoke to an engineer that enlightened me why all consumer automotive and ship to shore chargers use the same resistance sensor for the mass market products to increase the margine of safety and they are in fact reducing charge at 10 percent bulk charge rather than 70 to 80 percent.
Industrial and commercial chargers are very different.

The bottom line is it is taking far too long to recharge batteries than it should which means added wear and fuel when using a generator.

It makes me wonder how quickly the solar chargers actually begin reducing charge?

As far as my situation as it is, am still making power for much less than the power company was charging me and will continue too even if gas goes to 8 bucks a gallon.

creeky
Member
# Posted: 19 Jun 2014 11:22
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groingo the solar controller reduces charge amperage based on the rate the batteries fill up.

Once the bulk charge stage takes the voltage to 14.5 (this morning I saw as much as 70 amps or over 800 watts) the controller begins to reduce the amperage to maintain the battery voltage at 14.5.

Today, at 11 a.m. I am currently (sorry) charging at 20 amps. Even tho my solar panel read out is showing they could be creating 60 amps of current.

This is the fastest way to reliably charge your battery.

I believe your Crown batteries should be charging at 14.5v for 180 (or even 210 if discharged more than 20% last night) minutes in order to be "fully" charged.

This is one advantage of solar. The controllers do a better job of battery maintenance.

Or. to answer your question: solar controllers begin to reduce the charge rate (amperage) as soon as the batteries reach the prescribed voltage (in this case 14.5v).

buckybuck
Member
# Posted: 20 Jun 2014 15:32
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Here's what I do. YMMV.

When it's been cloudy or I haven't been to my place for a while and the batteries are low, I have a Iota battery charger (my guess is it voids the warranty if you do this, but there's a plug you can pop out on the back in order to access a POT screw that adjusts the charge voltage) that I hook up to the batteries. I then run the charger through my tiny Harbor Freight generator for an hour or so to perk up the batteries.

I'm not at my cabin right now, but I think the battery charger I've got is either the 45 or 55 amp model, which I seem to recall someone here recommended that I use. I'm looking on eBay right now and Iotas seem to be running for more than I'd want to pay, but I've seen them at times on eBay or CraigsList for less.

groingo
Member
# Posted: 20 Jun 2014 17:12
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Just heard back from Schumacher and they verified the charge numbers I was looking for, I ordered the Ship to Shore model which puts out a constant 10 amps till the battery is 80% charged then after 80% it will taper off but not before.

This will still operate within my generaters sweet spot for best fuel mileage and also cut charge times by at least 20% overall while providing a deeper charge for the batteries extending time between charges....that's the plan anyhow.

creeky
Member
# Posted: 22 Jun 2014 09:56
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Hey buckybuck. I use a powermax, cheaper than the iota, for supplemental charging in the late fall/early winter. I also opened the box and tweaked my control pot. To 14.5. I was trying for 14.7 due to the cold ... but an hour of genny charging in the morning helps the limited solar input get the batteries to absorb... tricks and tips.

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