Replacing a 55 amp converter with a 45?

Smk may be right about the voltage surface charge etc, although I think that would be more applicable to a slow charge overnight. I gather it has to do with filling/exposing the rough surface of the plate

You don't get 50 minutes at 80 amps, but you do get more than two-(I recognize that smk was exaggerating to make a point) Look at the ugly graph and see how the SOC when tapering starts is lower as you go up in charging rate.

You are into the diminishing returns area on the left as the acceptance rate curve goes vertical, so 80 amps will not be much faster than the 70 amp curve shown, but you might get about 15 minutes of constant amps.

Yes, 50-90s drop the SG into the red and getting back to full, baseline SG is a chore. If you only do 85-99s on solar it doesn't hardly happen and it is easy to get to 100--you don't even need to do a serious overcharge. But I have no comparison on ease of getting back from 90 after doing a 50-90 at 40 amps vs at 80 amps. Somebody who is keen can run those tests! :)

smkettner wrote:

jrnymn7 wrote:
This is all normal when charging flooded lead acid batteries. Moreover, sulfation is reversed during charging, not created, so how bulk charging a pair of 6 volt gc-2's at 80 amps will increase sulfation is a complete and utter mystery to me???

BFL consistently speed charges his batteries and reports lost capacity until a top charge is done upon return.
Call it what you like... lost capacity is sulfation in my book.

But it is not the speed of the charge (within reason, of course) but rather the lack of 100% charging. "speed charging" does not necessarily cause heavy sulfation or stratification, incomplete charging does. And continually floating batteries at 13.6v from 80-??% does result in capacity loss. Just look at all the threads about folks waking up with dead batteries. In every single case, they are using a low V low A converter to try to float charge their batteries from 80-100%... with disappointing results.

As for surface charge vs. 'real' charge... there will always be a level of surface charge, regardless of the charging voltage or charge rate. To prove this, all one needs to do is start charging a battery at any voltage setting of their choosing... charge for say 15 minutes, or to what you believe to be 90% charged... turn off the charger... and watch the voltage reading quickly drop.

This is why voltage readings cannot be used to determine battery SOC, while under load or being charged. Only by counting Ah's replaced can one accurately determine SOC while charging. Likewise, static amps at near full charge can also give a good indication of SOC.

jrnymn7 wrote:
This is all normal when charging flooded lead acid batteries. Moreover, sulfation is reversed during charging, not created, so how bulk charging a pair of 6 volt gc-2's at 80 amps will increase sulfation is a complete and utter mystery to me???

BFL consistently speed charges his batteries and reports lost capacity until a top charge is done upon return.
Call it what you like... lost capacity is sulfation in my book.

Nothing wrong with this routine as long as you also disclose the downside.

Charging a battery is not the same as winding a spring or filling a bucket.

smkettner wrote:
80 amps for what two minutes? Then you are tapering quickly and will have BFLs sulfation issues requiring extended top charging upon return.

A pair of Trojan T-105's in series have a capacity of 225Ah's. At 50% dod, that is (-) 112.5Ah's. (let's say -112).

At 80 amps charge current, it would take a little more than two minutes to do a 50-80% bulk charge... more like 50 minutes... during which time ~ 67Ah's would be replaced... regardless of how many current limiting chargers are used to produce that 80 amps of charge current.

(But yes, a 79.988149% - 80% charge would only take 2 minutes).

Then, amps would begin to taper slowly from that 80a charge current. Shortly thereafter, the charge current would indeed drop off rather quickly, as the battery builds resistance. This will result in the next 10% charge (80-90%) taking about 30 minutes to replace only 22Ah's. The final 10% would take upwards of 2-3 hours, depending on the particular battery's inherent resistance.

This is all normal when charging flooded lead acid batteries. Moreover, sulfation is reversed during charging, not created, so how bulk charging a pair of 6 volt gc-2's at 80 amps will increase sulfation is a complete and utter mystery to me???

Perhaps smkettner is referring to BFL doing 50-80% cycles; which will indeed result in sulfation build-up, and even stratification... IF AND ONLY IF left unattended to for prolonged periods. But other than this, charging at a higher charge rate, which btw, requires higher Boost/Vabs settings, simply cannot, and will not, lead to increased sulfation. In fact, the higher voltages and resulting higher currents will decrease sulfation better than charging at barely more than a float charge (i.e; at 13.6v) from 80-100% for days on end. And the simple fact that the batteries are accepting the charge rate, AND quickly building resistance proves that desulfation is indeed occurring.

BFL13 wrote:

smkettner wrote:
80 amps for what two minutes? Then you are tapering quickly and will have BFLs sulfation issues requiring extended top charging upon return.

When you do a 50-90 either of the three ways shown in my ugly graph, you still end up at the same 90, so what difference is there wrt sulfation?

I suspect smk still believes there is a "quality" to the recharge using a lower charge rate. I can't see that in doing 50-90s. 90 is 90 no matter how you get there. There are not two kinds of 90, one better than the other.

Yes I do believe when speed charging there is a bit of 'surface' charge to the 90%. I further believe some of the natural sulfation is harder to remove and takes more time that a speed charge does not allow. So you get home and you have to deal with this more difficult sulfation. A slower charge reduces the effect. JMHO

You already have the PD. Only cost is a bit of time. Go for it, I think you'll be more than please with the results.

RKW wrote:
Thanks for the responses folks.

Just to clarify, my old trailer is incandescent bulbs throughout, the new trailer is LED throughout.

The old trailer's battery bank consists of dual Trojan T-105's. The 45 amp PD did an excellent job of maintaining the battery bank. The first pair of batteries were replaced after 8 years and were still good, just requiring frequent watering. Boondocking with short, daily recharging from a generator was no problem. I have a Link 10 battery meter and I monitored the recharging. A 45 amp converter/charger is a good match for a 225 amp-hour bank.

What batteries came with the new trailer?

smkettner wrote:
80 amps for what two minutes? Then you are tapering quickly and will have BFLs sulfation issues requiring extended top charging upon return.

When you do a 50-90 either of the three ways shown in my ugly graph, you still end up at the same 90, so what difference is there wrt sulfation?

I suspect smk still believes there is a "quality" to the recharge using a lower charge rate. I can't see that in doing 50-90s. 90 is 90 no matter how you get there. There are not two kinds of 90, one better than the other.

80 amps for what two minutes? Then you are tapering quickly and will have BFLs sulfation issues requiring extended top charging upon return.