OK, I came across two graphs posted here. Both happened to be in Salvo posts but I think one originated with Bigfootford. ANYWAY...I'm sure each graph has been discussed and dissected on its own. I'd be interested in opinions as to which setup won a hypothetical 2 hour race. Graphs shown below. What I think I see is this.IOTA 55, 2x GC nominally 225AH, 50% SOC, C/4 charging rate:First 60 minutes: approx 50AH (to 72%)61-90: +11.5AH (to 77%)91-120: +6.8 AH (to 80%) (ignoring efficiency losses)Total 68AH into 50% 225AH batteryPD9260, 2x Grp 24, nominally 170AH, 50% SOC, nominally C/3 rate:First 60 minutes: approx 42 AH (to 75%)61-90: +12.5AH (to 82%)91-120: +9.5AH (to 88%)Total 64AH into 50% 170AH batteryNot apples to apples. But close enough to draw conclusions? To me it seems like the PD did better. No, it never delivered its rated amps. But in 2 hours it pushed almost as many AH as the IOTA, but into a much tighter box. Am I wrong? Too close to call, you pick em? Batteries too different to be able to say?source post for IOTA graphsource post for PD graph

Hi snow,As you said--very close. Close enough that there is no reason to move from a PD to Iota.Btw my PD 40 amp has never ever done more than 37 amps when in "boost" mode. That includes times when I was running the water heater from the old MSW inverter.I do "see" 125 amps from the Magnum inverter/charger. It can do so from a single 15 amp shore power cord.I have not yet tried running the PD and Magnum at the same time.

I'd like to see a race 1.200 to 1.280 similar batteries, in minutes elapsed.Of course, this would mean, I'm a meanieThis is a real life simulation of generator charging elapsed time which is not hypothetical.

MEXICOWANDERER wrote:I'd like to see a race 1.200 to 1.280 similar batteries, in minutes elapsed.Of course, this would mean, I'm a meanieThis is a real life simulation of generator charging elapsed time which is not hypothetical.What model batteries? And what charge controllers and what Voltages? I think you'd be pretty pleasantly surprised how well that Mega Watt 30 amp set with 8 gauge wire and 15.0V and a 2 foot run to the battery does, time wise. I'd be guessing 5 or 6 hours on a pair of GC-2's. You have to wait a couple of days on the SG to catch up, 3 days worth? It's getting the SG over about 1.265 to 1.280 that eats up most of the time, in my observation. It's just slow going there, you should be running a c/20 rate at the top charge portion, 10 to 11 amps charge rate fixed at 15.0V fixed. Huge waste of fuel spinning a generator for those last 15 points.IMHO, that's what it takes at the end to get that 1.280, if the plates are not sulfated at all.

Go a little big on the PD, 60+ is fine. You need 60 if you want to get 45.A little less on the IOTA, 45 amp is fine. Bulk less than an hour seems a bit much to me.JMHO.With a poor connection PD might be favored as it will hold 14.4 volts for 4 hours and can be reset. IOTA will get tricked and drop voltage to 14.2 fairly quick.Mostly a draw as both are excellent.

You can do better than that with a PD if you use really fat and short wires between it and the battery. However it will taper like that with only a little longer wire while some other actual constant amps chargers will do constant amps in the Bulk stage.http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27651123.cfm

IOTA graph vs PD graph | Good Sam Community

46 Replies

Snowman9000
Explorer
Nov 04, 2014
smkettner wrote:
Go a little big on the PD, 60+ is fine. You need 60 if you want to get 45.
A little less on the IOTA, 45 amp is fine. Bulk less than an hour seems a bit much to me.
JMHO.

With a poor connection PD might be favored as it will hold 14.4 volts for 4 hours and can be reset. IOTA will get tricked and drop voltage to 14.2 fairly quick.

Mostly a draw as both are excellent.

The short duration of bulk is thought provoking. He was at C/4, which by most people is considered quite aggressive. He got 50AH in an hour. 45 amps would be about C/5, still considered to be on the aggressive side but less so. With a 45 amper, the most he would have gotten in all likelihood is 45AH. So in a one hour race, the 55 wins. But in two hours, who knows. Salvo has another interesting graph in the same post, showing the SOC at X volts at given rate of charge. I interpret that graph to show what the SOC will be when in this case an IOTA drops from bulk, at a given rate of charge. Unfortunately C/4 is not shown, and I don't know if it can be reasonably extrapolated.
BFL13
Explorer II
Nov 04, 2014
You can do better than that with a PD if you use really fat and short wires between it and the battery. However it will taper like that with only a little longer wire while some other actual constant amps chargers will do constant amps in the Bulk stage.

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27651123.cfm
time2roll
Nomad
Nov 04, 2014
Go a little big on the PD, 60+ is fine. You need 60 if you want to get 45.
A little less on the IOTA, 45 amp is fine. Bulk less than an hour seems a bit much to me.
JMHO.

With a poor connection PD might be favored as it will hold 14.4 volts for 4 hours and can be reset. IOTA will get tricked and drop voltage to 14.2 fairly quick.

Mostly a draw as both are excellent.
NinerBikes
Explorer
Nov 04, 2014
MEXICOWANDERER wrote:
I'd like to see a race 1.200 to 1.280 similar batteries, in minutes elapsed.

Of course, this would mean, I'm a meanie

This is a real life simulation of generator charging elapsed time which is not hypothetical.

What model batteries? And what charge controllers and what Voltages? I think you'd be pretty pleasantly surprised how well that Mega Watt 30 amp set with 8 gauge wire and 15.0V and a 2 foot run to the battery does, time wise. I'd be guessing 5 or 6 hours on a pair of GC-2's. You have to wait a couple of days on the SG to catch up, 3 days worth? It's getting the SG over about 1.265 to 1.280 that eats up most of the time, in my observation.

It's just slow going there, you should be running a c/20 rate at the top charge portion, 10 to 11 amps charge rate fixed at 15.0V fixed. Huge waste of fuel spinning a generator for those last 15 points.

IMHO, that's what it takes at the end to get that 1.280, if the plates are not sulfated at all.
MEXICOWANDERER
Explorer
Nov 04, 2014
I'd like to see a race 1.200 to 1.280 similar batteries, in minutes elapsed.

Of course, this would mean, I'm a meanie

This is a real life simulation of generator charging elapsed time which is not hypothetical.
pianotuna
Nomad III
Nov 04, 2014
Hi snow,

As you said--very close. Close enough that there is no reason to move from a PD to Iota.

Btw my PD 40 amp has never ever done more than 37 amps when in "boost" mode. That includes times when I was running the water heater from the old MSW inverter.

I do "see" 125 amps from the Magnum inverter/charger. It can do so from a single 15 amp shore power cord.

I have not yet tried running the PD and Magnum at the same time.

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IOTA graph vs PD graph

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