Max Charging Current of typical GC2 battery

BFL13 wrote:

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Meanwhile--yes, on solar it is not always possible to get to full each day. You can go days and days with an incomplete recharge, and get sulfated. Later on, when the sun shines and you can get to full, it does not mean you are out of the woods.
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Yes equalization is important after a couple of weeks of partial charge. One of the reasons I've been avoiding AGM, as they seem more difficult to recondition afterwards. Not sure how long these batts will last like this, but we're only snow birds, not full-timers, and they may well get stolen before they die anyway (like happened last winter in storage).

And Berries? About the only thing I miss about the Wet coast are the Salmon berries and fish. Certainly don't miss the fires further inland where it's not wet.

We've had a wet year here in Central-North Ontario, but it's great for the berries, and no forest fires, thank gawd. Not so good for my solar charging though.

North Pacific coast. Where there is fog the berries grow. Blueberries like it a little warmer. Raspberries are the most delicate. Now I have to go to Costco when I go north and buy an assortment for my toast.

i love black berries and rasberries

Ooooo I could take that one and go a looooong way - but I'll be nice.

MEXICOWANDERER wrote:
I went to Hornby Island in August BFL. Thick Pendleton Shirt all day, jacket in the morning, Flowing water was fit for penguins. What size wet suit did you use at "The Lake"?

Skipping your meds isn't good.

Constant voltage charging at 14.8 volts is the highest rate I would recommend. And you'd better believe there is a significant difference between 14.4 and 14.8 voltage set points in relationship to overall charge time. Yes, between 1.260 and 1.280 charge acceptance is much lower. but then a Delta T (differential amperage) needs to be clearly stated between the four tenths volts spread. It is anything but insignificant.

But then the issue will refocus on feasibility of obtaining a device that can support fill voltage in constant voltage mode throughout the procedure.

Again the entire subject of constant voltage charging is irrelevant if the device is not subject to a long term off-grid heavily cycled use.

I went to Hornby Island in August BFL. Thick Pendleton Shirt all day, jacket in the morning, Flowing water was fit for penguins. What size wet suit did you use at "The Lake"?

Yer gonna get Eee-clip-sed soon. That otter drop yer banana boat tropical clime another 2c. You can watch an Al Gore, movie to help ease the shivers.

Actually I am quite envious of the Blue, black, rasp, and huckleberries in your neck of the woods.

OldSmokey wrote:
I'll give you a pro tip here and it's for Trojan T105's
but is applicable to other GC2's if used with care..

it's all about max heat capacity, for a T105 the best figure I would use is 0.05 watts per Ah. a T105 has an internal resistance of 0.003 Ohms . so that's 0.001 Ohms per 2 volt cell.

The max thermal charge limit is square root of (.05 x 225Ah) / .001 = 106 amps. yes.. you can charge a T105 at this rate..
this is approx c/2

I wouldn't advise you do this often, but it can be done.

Somebody a few years back posted that he was talking to a Trojan tech support guy about all this, and he said the Trojans could accept any amount of amps at first.

The whole thing is based on the simple fact that the acceptance rate at any SOC depends on the voltage. If you are at a lower SOC then at any same voltage the batt will accept more amps than at a higher SOC. (which is why amps taper in the Absorption Stage). For the same SOC, jack up the voltage, and it will accept more amps.

If you hit the batt with a huge amps rate, the voltage will spike and amps will immediately taper to what the battery will accept.

You can see in my ugly graph above how that works where there is a diminishing returns in going to higher amps for how long it takes to do a 50-90. Even if the battery will accept way more amps, you might only save 10 minutes of generator time going to a 70 vs a 55, so why pay way more for a way higher amp charger and then need a way higher wattage generator to run that higher amp charger, just to save 10 minutes of gen time? OTOH there is a big diff in time between 55 and 35 amps on 220AH.

(You double the times for doubling the AH at the same amps, BUT you do not halve the charging time on the same AH by doubling the charging amps.)

You have to do a proper analysis of the whole picture to decide on your best bet for a set up for how you (not some other guy) camps.

Meanwhile--yes, on solar it is not always possible to get to full each day. You can go days and days with an incomplete recharge, and get sulfated. Later on, when the sun shines and you can get to full, it does not mean you are out of the woods.

You still need to desulfate from all that time earlier on. You can avoid a lot of that if the weather forecast is any good, by doing a bit of gen charging in the morning so there is time for the solar to catch up that same day and get it done.

Above, I described winter camping, but here in August on solar it is way different. Gottaluvit! Who cares about batteries? It is all about corn on the cob, BBQ steaks, and picking blackberries for dessert (after a swim up at the lake of course) :)

I'll give you a pro tip here and it's for Trojan T105's
but is applicable to other GC2's if used with care..

it's all about max heat capacity, for a T105 the best figure I would use is 0.05 watts per Ah. a T105 has an internal resistance of 0.003 Ohms . so that's 0.001 Ohms per 2 volt cell.

The max thermal charge limit is square root of (.05 x 225Ah) / .001 = 106 amps. yes.. you can charge a T105 at this rate..
this is approx c/2

I wouldn't advise you do this often, but it can be done.

i posted this last night in my AGM battery thread
take note these are Surplus server batteries removed from routine service
they are going on month 14 of daily use & recharge, they are at 400+ cycles

just a quick note

70 minutes after stopping all charging
down 15 ampHr aka 3AH per battery
load 10amps , 2amp per battery
battery SOC 97.7%
battery voltage 13.00v

fully charging batteries everyday of use, makes a significant difference
in batteries maintaining voltage

now at 4:45 am this morning (restless night)
4 amp load
91.0% SOC
12.87v

i routinely see over C 10% charge starting and see 1/2% when done charging
yes i'm using more gas than i used too, i need the genny for A/C anyways
winter time will see some reduction in generator hours
this set of batteries has never seen 50% SOC from my use
it does see full recharge almost every single day

i'm not a weekend camper, we are full time
many of you will never see 400 cycles on your batteries, before you replace them or the RV

getting 5years by going weekend camping twice a month is ONLY 120 cycles
that should be an easy life for ANY battery, but many die with only 2yrs of use

Battery Mantra "charge charge charge"

MEXICOWANDERER wrote:

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What DOES hurt batteries sir, is to constantly undercharge them for weeks or months at the stretch. They will sulfate, and few people want to learn how to never mind actually equalize a battery. That ends up killing a battery.
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Sadly this is what we often do with only solar and no generator.

So far only 2 weeks of under-charging max though, with a 32V equalization afterwards. Truck charging as we travel between boondocking sites should help.