Replacing a 55 amp converter with a 45?

If you hit a 200AH bank at 50% SOC with a current limited charger doing 100a, I think amps would taper right away. On my ugly graph that would be way to the left on the vertical where there is no constant amps stage at all.

It is still the old lower SOC at start of taper with a higher charging rate only now you have such a high charging rate, I think the SOC at start of taper would be less than 50% (at 14.x voltage)

I had an ugly graph somewhere back when I had the bank of three 27s in the cold at 50% and hit them with the big amps. No constant amps, just a taper.

Here is one--check A3 on the 27s when bank capacity was lower, increasing the charge rate from what it was at A1

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/24849190.cfm

Thanks, Niner, but I (we) are trying to determine whether or not using a higher charge rate, i.e; using BFL's mega AMP approach, is resulting in increased sulfation/stratification. SMK has expressed his concern that such a fast replacement of Ah's does not allow for sufficient cleaning of the plates.

I, for one, think this is a very reasonable concern on smk's part, and believe it is deserving of further investigation. That said, I have yet to see any evidence to support such a notion. But then again, I read an interesting article this morning that mentions the 'Amp Hour Law' which suggests limiting Charge Current to the amount of Amp Hours needing to be replaced.

So, for example, a 200Ah bank, at 50% dod, should be charged at no more than a 100a charge current. And as Ah's are replaced, the charge current should decrease accordingly. So, by the time the bank is at 20% dod, the current should have tapered down to 40a max.

Of course, this cannot be accomplished using any power supply / smart charger that operates in a constant current mode from 50-80% soc. It would require a single stage dumb charger, with a particular max amp output, set to the appropriate voltage, to best approximate such a charge profile.

mena661 wrote:

jrnymn7 wrote:

If it is true, 'speed charging' leads to lower sg readings, I would definitely like to see the evidence.

My experiences with my own batteries. C/7 charging doesn't get my SG any higher than BFL with his fast charging. I've even charged at C/5. The best I've seen was 1.265 (C/7) with it mostly hitting 1.260 or a bit lower. I've been using BFL's charging methods since I got my batteries. I've tried the converter only method with 3 different models. My batts are pampered big time. Doesn't work for me. YMMV.

A week of camping with the PD 9245 in winter, and the Trojan Scrubber battery, running solo, pulling 40 amps amps a day, had me at one cell at 1.250, and the rest at 1.260. My idiot gauge always said I was 2/3 charged, as soon as the generator was turned off. Voltage was about 12.62 to 12.68 with the surface charge removed. With the Mega Watt, 12.73 is pretty common. SG is up 10 to 15 points also when using the MegaWatt at 15.0V. Since I see only 50% discharge cycles allowed, going from 50 to 90 to 50 to 97% adds about 14%, or the battery ends up at 57-97%, is my guess, hypothetically.

As landyacht318 found out 15.3 doesn't seem to hurt a thing on his Group 31. I don't think the T-1275 is much different. GC-2's are just much more efficient at charging back up quickly, with less effort, baby sitting or hand holding. Some shapes and designs need a little bit of brute voltage to get them topped off while charging, others, GC-2's, maybe L-16's too, seem fine with running the 14.4V the PD 9245 or 9260 puts out, or if you have big battery banks, the 9280 or 92100 models.

Run what makes you happy, for a charge controller, if it doesn't make you happy, change it, or get a pendant, charge wizard or the IQ-4 for the Iota series. Or spring for the new Boondocker adjustable voltage model that Randy makes over there at Best Convertor.

OK. It's a done deal. As soon as I energized the PD it went directly into the bulk mode.

Ryan,

I'm not sure whether you're aware of it, but your tank heaters (we have 12V heating pads in our Class C, too) are not ON constantly - they cycle ON and OFF.

It's not likely that all three of your heaters be all ON at the same time very long, so a 30 amp current draw would be happening only on hit or miss basis. I would think that a 45 amp converter should handle your tank heaters ... expecially since you mention that your lighting is LED, like ours.

Now .... if you were to drycamp in cold weather with those tank heaters going ... then that's a different set of challenges, but still not requiring a change of your converter. You'd probably need big batteries plus A LOT of solar/sun/daylight, or a lot of generator run-time if using your tank heaters several hours per day under those conditions. We carry a small and very quiet generator along for conditions such as this, but only enough gas for it for 25-30 hours of continuous running.

RKW wrote:
I just realized something that might be significant to my decision. My new trailer has 12 volt heating pads on the holding tanks. I have 2 gray tanks, and of course a black tank. I have no practical experience with that aspect of the 12 volt side of life, but the spec sheets for those pads show an amperage draw of 9.9A for a small one. If there were three heating it would be a 30 amp draw. That could be a game changer as far as boondocking goes. A bigger battery bank and a bigger converter to charge the bigger battery bank might be prudent. Even hooked to shore power, a 30 amp draw for a 45 amp converter is not a good thing. The trailer also heats the tanks by blowing a portion of the furnace heat to the holding tank areas. The dealer indicated the best use for tank heaters are when you are going down the road, when the furnace should be off. Like I said, I have no experience with tank heaters or the philosophy of use of the tank heaters. I don't plan of using my trailer in weather that cold, but you never know what you may unexpectedly encounter.

Thoughts?

I think if you are camped at temperatures where the tank heaters are needed you will be plugged in or running the generator 24/7. Either way the 45 amp PD will be fine with the 30 amp heaters that should cycle some. With continuous power the battery will stay topped up.

jrnymn7 wrote:
Since we've veered off to the subject of heat, for a moment, what should one's concerns be regarding heating the fridge cabinet? I have a dometic (forget which model) two-way 110v/propane. I've never ran it at below freezing temps, but this year I likely will.

AFAIK, the refrigerant doesn't like real cold temps. I've read that anything below 40f, it's a good idea to use a lamp or small heater adjacent to the coil area. I use a 120V fridge so I'm sure other Northern campers can reply better to the question.

BTW, I like your ideas about the hydronic heating solution. I am thinking about using my solar diversion load to heat my fresh water tank water, I have an inboard steel tank under the dinette seat so even heating one degree above indoor ambient would net me some passive heat transfer. I'll need to do some calculation for the heat rise. If I went this route, I'd probably get more module....hmmm, that didn't take long to need more power.:B

Since we've veered off to the subject of heat, for a moment, what should one's concerns be regarding heating the fridge cabinet? I have a dometic (forget which model) two-way 110v/propane. I've never ran it at below freezing temps, but this year I likely will.

RKW,

A mechanic friend, way back, told me, anything to do with heat is a killer on power; be it creating heat, or removing it. And he was absolutely right! A 30a draw is enormous, in 12v terms. Heck, that's a large draw ac wise, even.

I envision a day when rv's are built with hot water in-floor radiant heat. Then heater hose and finned copper elements could be installed to heat areas like the tanks, batteries and fridge compartment. It would be way more efficient and effective. Until such time, though, one can install their own little system by replacing 1) the furnace with a propane hot water heater, 2) the power hungry fan with a small efficient 12v pump, and 3) the duct work with 5/8" heater hose.

Your only other choice is more solar; which is hit and miss, and harder to come by in the colder months; and another pair of 6's to power those blankets. Hot water heat just keeps looking better and better, wouldn't ya say?

westend wrote:

Yeah, she's holed up in a coral reef somewhere last I heard.

Recent sighting---

Looks like she just got back from the beauty parlour there. Here is what she looks like first thing in the morning