Converter Replacement Time - Can I put in a larger amperage unit?

[demort]

Hello all,
I see some posts near to my question but not quite what I'm
The Magnatek 6332 in my 1993 Itasca Sunrise got really noisy last week. So noisy that I shut it down and relied on my solar to keep the 12v system happy.
I have a pair of Trojan T145's for house batteries, so I'd kind of like to upgrade to a Progressive Dynamics Part converter/charger. I see that it's suggested to have a charge amperage of 1/3 the amp-hours.
My batteries have a 20 hour amp-hour of 260, so that's like 87 amps!

The PD converter units are available in 35/45/55 amp configurations

What size wires would you suggest in order to push 45 and/or 55 amps?
I assume the wires I have are at least rated for 32 amps since that was in there originally. I would think that even a upgrade to the PD4635 will be a big improvement, but the cost difference for +10 +20 amps is minimal.

I haven't traced the wires yet to see if upgrading these is feasible. When I look at that it, I'll also gauge the wires and try to measure the run.
Should I be using a voltage drop calculator to figure this out?

Thanks in advance for your advice.

Doug

 

[Optimistic Paranoid]

Ampacity is a made up word from AMPere capACITY.  All wire has an ampacity rating.  There are charts out there that list these figures, some of which vary slightly to allow for different insulation.  The one I've got says:

12 gauge wire 10 amps
10 gauge wire 15 amps
8 gauge wire 25 amps
6 gauge wire 40 amps
4 gauge wire 60 amps
2 gauge wire 95 amps

These figures are for single wires.  If you have a bunch of them in a bundle, you have to de-rate to a lower ampacity cause they can't shed the heat.

 

[John From Detroit]

One thing you need to know. if the wires are too small (Up to a point) it will slightly lower the Converter output.. So you can use the 45 amp quite likely with no changes but I would recommend upgrading the wiring.. OH and PD makes 'em up to 80 but I do not know if the 4600 line goes that high.

How do I know they make 80.... Yup. I'm sitting on one. It works great.

 

[solarman]

Hello all,
I see some posts near to my question but not quite what I'm
The Magnatek 6332 in my 1993 Itasca Sunrise got really noisy last week. So noisy that I shut it down and relied on my solar to keep the 12v system happy.
I have a pair of Trojan T145's for house batteries, so I'd kind of like to upgrade to a Progressive Dynamics Part converter/charger. I see that it's suggested to have a charge amperage of 1/3 the amp-hours.
My batteries have a 20 hour amp-hour of 260, so that's like 87 amps!

The PD converter units are available in 35/45/55 amp configurations

What size wires would you suggest in order to push 45 and/or 55 amps?
I assume the wires I have are at least rated for 32 amps since that was in there originally. I would think that even a upgrade to the PD4635 will be a big improvement, but the cost difference for +10 +20 amps is minimal.

I haven't traced the wires yet to see if upgrading these is feasible. When I look at that it, I'll also gauge the wires and try to measure the run.
Should I be using a voltage drop calculator to figure this out?

Thanks in advance for your advice.

Doug

T145's should be charged at C/8 to C/12  therefore 33 Amps
if you are in a hurry you could do C/6 and that's 43 Amps but this will shorten life a little

 

[Gary RV_Wizard]

My batteries have a 20 hour amp-hour of 260, so that's like 87 amps!

How did you come up with that number?

Traditional wisdom is that a flooded cell battery like the T145 can be charged at a max of C/4, where "C" is the combined Amp-Hour capacity.  Lesser rates work fine and are recommended for longer batery life, but may take a bit longer.  260/4 = 65 amps.  A rate of 45 or 55 amps is not necessarily a lot longer, though, because for most of the charging cycle the actual rate is well below the max anyway.  I would think a PD (or similar) 3-stage charger with a 45 or 55 amp capacity would do fine, and a 45 amp model  would be only a little slower than the 55.

This article may help understand:https://www.westmarine.com/WestAdvisor/Selecting-a-Battery-Charger

I think the ampacity table that Paranoid cited was for 15 ft wire lengths and battery connections are usually much shorter. Blue Sea (West Marine) has a table that covers shorter distances where voltage drop is insignificant. It indicates that 6 gauge wire will handle 50-70 amps at short distances.

https://www.bluesea.com/resources/1437

Your old Magnetek probably could not charge at more than about 15-18 amps at best, even though rated for a combined output of 32 amps. That is for both 12v use on the house circuits and charging. The old Magneteks could only charge with a portion of that total.  Even a PD 9245 will substantially outperform it.

 

[demort]

Ah - I had misread somewhere when I thought it was C/3, Gary.

The place I'm looking at recommends going for a converter/charger that has an option to charge Lithium batteries in case I ever want to switch to them someday. Downside is that it will bulk charge at 14.4 volts. This is the 4600 series and also looks super convenient to swap and go. These start at 35 amp which would be safest with my wires and what Solarman suggests.

He also carries a unit that will charge at 14.8 which is ideal for the Trojans, but no Lithium option for someday. 9200 deck mounted series - probably a slightly more complicated changeover. The 9200 starts at 45 amp.

I'm kind of leaning toward the 9200 since it's pretty unlikely that I'll ever afford lithium batteries with a similar capacity of the ones I have - or even be able to fit them in the current bay. If I do, the cost of a new converter would be a fraction of the batteries.

I am a little concerned/curious how far and what gauge the existing wires are. I think it must run from the middle of the rig to the disconnect switch on the dash then over to the bay by the door.

 

[Lou Schneider]

Unless the disconnect switch on the dash is a big red knob (not likely) it's not directly connected to the battery or converter wiring.

Instead, it controls a relay that does the actual connecting and disconnecting.  The relay can be mounted wherever it's convenient so there's no need to take the battery to converter wiring up to the dash and back.

 

[demort]

That makes better sense than what I was thinking Lou. I do hear a substantial clunk when pressing that switch, more like a relay triggering somewhere than just a rocker switch.

 

[John From Detroit]

The old magnetek was less than five amps. and it never stops.

The Progressive Dynamics (I'd go with the 45 amp and not bother with wires) will charge at UP TO 45 amps (A bit less with the smaller wires)  and knows when to stop

 

[Bobtop46]

I would also research the charging pattern voltages (bulk, absorption, and float) for the converter that you are considering.  Several questions you need to ask yourself.  How do you use your coach, is there a solar system attached, do you often discharge to a 50%? Does your coach charge the house batteries going down the road, most due, some don't.  What voltages (not amps) does your battery manufacture recommend?

Unless you boondock, have solar, or discharge deeply you will rarely use the higher amps because the converter will drop out of bulk (14.4v?) to absorption (13.7 or 13.8) almost right away, and you will spend the majority of the time in float (13.3 or 13.2).  Notice when the converter manual talks about charging patterns that amps are not mentioned.  An option to equalize manually or automatically is nice if possible. 

If you have plans to expand your battery bank, add solar or boondock then spend the extra money for a high amp converter and upgrade the wiring, if not get a smarter converter then what you have in the same amp rating and use your existing wiring.

 

[Gary RV_Wizard]

Ah - I had misread somewhere when I thought it was C/3,

The science here is not black & white, but generally the higher the charge rate, the shorter the battery life. Modern 3 or 4 stage chargers handle that by using a fairly high rate charge during bulk mode and then shifting to lower rates as the charge builds up. C/3 would be a fairly extreme "quick charge", such as a shop might do to get you back on the road in a hurry, but a lower rate, C/4 or c/5 is better practice if you can spare a little more time.  Since you only get anywhere near the max rate in the bulk stage (see bobtop46 reply), having some extra amps at that stage is often not a significant advantage.


In my opinion you are over-thinking the problem, focusing on small voltage differences that tend to get lost in the big picture. Other factors, e.g. battery temperature and average depth of discharge, probably have as much effect as optimal voltages.  Besides, battery engineers have differing opinions on what is optimal.  They can prove the value of  some voltage parameter in a lab with a controlled environment and a given set of working assumptions, but those are never achieved in an RV in real life.
Either the 4600 or the 92xx will do a good job for you. The wiring from the charger to the battery will be key, though. I'd plan on replacing it, but installation of either one is going to involve some wiring changes anyway. 

 

[demort]

You are right Gary. With all upgrades I tend to really over think it. I've been happy with how the solar setup I've applied have worked out so far - and that has been many hours of (over)thinking to engineer the solution.

For this situation though, probably any of the modern units will yield a nice and quieter improvement.

Same general amperage will give a gentler recharge, maximizing battery longevity and probably avoiding rewiring - while still making a great improvement.

sometimes it just helps to toss around ideas and get good feedback.

 

[Gary RV_Wizard]

If you could find a modern 35 amp converter/charger, it would probably out-perform the old Magnetec by at least 2x, even though it has the same theoretical capacity. I think PowerMax makes one in that range.

Here is an explanation of the 6332 internals that may help you in re-wiring:
http://windsurf.mediaforte.com/roadtrek/magnetek/Magnetek_6332_wiring_diagram.html

As I recall, the 6332 has direct 12v power feeds to its DC bus plus two external wires to the battery. You are probably going to replace those battery wires whether you replace just the conveter/charger or the entire AC/DC power center.