Schumacher Charger/Converter

Wsufans · 12-14-2015, 09:35 AM

I finally found this unit. It was buried behind the 120V panel.

I would highly recommend that if you have one of these you find it and replace it. There doesn't seem to be much data available on the unit. From my testing this is a single stage constant voltage unit that has the potential to boil lead acid batteries dry.

While it claims to be a 55Amp unit mine would only charge at 15 amps. At this rate it could take all day on the gen set to charge the battery bank.

I replaced this unit along with the Xantrex inverter with a Magnum Energy pure sine wave unit.

The Magnum unit is a high quality multi stage inverter/charger. It will charge at 100+ amps so you don't have to run the gen set all day.

Being a multistage unit is will also make the batteries last a lot longer.

edgray · 12-14-2015, 09:52 AM

Quote:

Originally Posted by Wsufans

I finally found this unit. It was buried behind the 120V panel.

I would highly recommend that if you have one of these you find it and replace it. There doesn't seem to be much data available on the unit. From my testing this is a single stage constant voltage unit that has the potential to boil lead acid batteries dry.

While it claims to be a 55Amp unit mine would only charge at 15 amps. At this rate it could take all day on the gen set to charge the battery bank.

I replaced this unit along with the Xantrex inverter with a Magnum Energy pure sine wave unit.

The Magnum unit is a high quality multi stage inverter/charger. It will charge at 100+ amps so you don't have to run the gen set all day.

Being a multistage unit is will also make the batteries last a lot longer.

It is likely you know more about this stuff than me, but I always thought charging deep cycle house batteries was like smoking meat.....low and slow is better. I'm sure your new smart charger / inverter is better than the cheaper OE unit WBGO installed, in fact, I recently replaced my converter with a smart charger too. Please feel free to educate me if I'm wrong about the charge rate. Ed

Wsufans · 12-14-2015, 10:04 AM

Quote:

Originally Posted by edgray

It is likely you know more about this stuff than me, but I always thought charging deep cycle house batteries was like smoking meat.....low and slow is better. I'm sure your new smart charger / inverter is better than the cheaper OE unit WBGO installed, in fact, I recently replaced my converter with a smart charger too. Please feel free to educate me if I'm wrong about the charge rate. Ed

Take a look at the attached page and look at the chart near the bottom. The charge amps and volts start out high then taper off as the charge proceeds. Once charged the voltage drops off to 13.2 and amps to essentially zero. Now this is all programmable but the factory settings work pretty good.

If you do a bit of research on multi stage battery charging you will find that this is pretty much the same for all units even some of the lower end units from folks like Progressive Dynamics.

nothermark · 12-14-2015, 10:26 AM

Quote:

Originally Posted by edgray

It is likely you know more about this stuff than me, but I always thought charging deep cycle house batteries was like smoking meat.....low and slow is better. I'm sure your new smart charger / inverter is better than the cheaper OE unit WBGO installed, in fact, I recently replaced my converter with a smart charger too. Please feel free to educate me if I'm wrong about the charge rate. Ed

You are more correct than he is. One factor is the level of charge in the batteries to be charged. Another is the rate at which the particular battery can accept a charge. Cranking up the voltage to force a high current charge rate is how batteries get cooked. C/5 for bulk charging and c/10 for topping off is usually the maximum recommended. C= amp hours rating of the battery. Lower is fine. If you are running parallel strings you can total the string capacity to get the maximum charge rate.

Wsufans · 12-14-2015, 01:37 PM

Haven't cooked any yet with these units. But also note that these units also sense the battery temperature.

I HAVE cooked batteries with single stage constant voltage chargers running somewhere over 13.8 volts.

nothermark · 12-15-2015, 09:37 AM

FWIW The point is that even with temperature sensing the folks who make the batteries give charge limits to maximize battery life. The chemistry sets the speed at which a battery is comfortable accepting a charge. That is why a typical charge cycle is 12-16 hours for a happy battery. Charging too fast in any stage is a way to shorten life. That is why the multi stage chargers are the best but most expensive option. How much damage is done by shortening the cycle is too variable to comment on other than to say the manufacturers probably know. Few other folks have the time, need, or facilities to test enough to really understand it.

Duner · 12-15-2015, 11:18 AM

For those of us that do several days of dry camping, you don't charge at a 10 hr or 20 hr rate, it's just not practical. So when you fire up the generator, you try to get as much charge back in the batteries in 2-4 hrs running per day.

What's more critical to maximize the battery life is not to discharge below 50%. The Magnum MS series with 3 stage and temp charging can safely charge wet or agm batteries without sacrificing significant life expectancy. We use agm type batteries because they can take a recharge faster, so you run your generator fewer hours.

If you're plugged in 98% of the time and charge at C20 rate you may get 10 yrs or more out of your batteries. If you dry camp for a week once a month, your batteries may last 5-7 yrs.

Two ways to kill even "new" batteries....1) charge at 13.8 v for 6 months without adding water, or 2) discharge to 0 volts and leave it that way for more than a week or month.

aauummm · 01-29-2017, 11:57 AM

Quote:

Originally Posted by Wsufans

I finally found this unit. It was buried behind the 120V panel.

I would highly recommend that if you have one of these you find it and replace it. There doesn't seem to be much data available on the unit. From my testing this is a single stage constant voltage unit that has the potential to boil lead acid batteries dry.

While it claims to be a 55Amp unit mine would only charge at 15 amps. At this rate it could take all day on the gen set to charge the battery bank.

I replaced this unit along with the Xantrex inverter with a Magnum Energy pure sine wave unit.

The Magnum unit is a high quality multi stage inverter/charger. It will charge at 100+ amps so you don't have to run the gen set all day.

Being a multistage unit is will also make the batteries last a lot longer.

2010 Itasca Sunova 33c here. I'm going to replace the OEM Schumacher single stage converter/charger also. In accessing the converter did you go through the access panel below the sink in the bathroom or did you pull out the load panel? Also, would a slightly larger sized converter fit into the space?

I'd tear into it myself but the MH is in storage and it's cold here! I don't relish lying on my back in a cold MH messing around with it. I'd like to order the new converter now so that I'd be all ready to replace it as soon as it warms up but I'd like to know beforehand if there are any problems in accessing/removing the old one, and if there are any problems with putting the new one in, such as space.

Wsufans · 01-29-2017, 10:55 PM

You have to pull the main power panel to get to it. It has a standard 120V plug and it plugs into the same box as the outside TV. It is mounted to the structure behind the toilet.

I have a photo somewhere but....

While you have the panel out fish a string to the little compartment in the bin behind the passenger side tire then over across the coach to the water pump compartment and up to where the Xantrex inverter is.

Just saying for future connection to better charger. I would not put a new one back in where the old one was it is impossible to service and/or monitor.

wa8yxm · 01-30-2017, 07:45 AM

One caution about re-charge speed.. And a note: The NOTE: Many Top end Inverter/Chargers you can program the charger to limit amps and so on.

Now the caution: Charging a battery too fast is damaging
XANTREX for most battery types suggests no more than 30% of the C/20 rating of the battery.. Thus a Group 29 with about 100 Amp Hour (C/20) Rating wold charge at the max rate of 30 amps

A pair of 220 Amp Hour GC-2's.. 66 Amps max charge

LIFELINE AGM, consider that the minimum run converter "Full open"
But that ONLY applies to lifeline

NOTE: even slower recharge (on most types) will extend battery life, TROJAN recommends 10% of the C/20 rate for best life.

Note again, GEL type batteries (hard to find in RV sizes, 20% max recharge rate and monitor temp..
3

Wsufans · 02-02-2017, 08:38 PM

Ok but you also have to look at the voltage and current curves. The Magnsine will charge at 100 amps for only a few moments before it tapers down as the voltage increases.

A good designed unit will not charge at the full available amperage for the full charge time. If it charged at 100 amps until the charge was complete it would no doubt fry a battery quickly. But that is not how it works from what their documentation says.

The Magnasine manual has a great explanation of this. And yes you can limited the charge current if you choose to do it.

I programmed it for the battery type I have, Sealed Lead Acid and let it do it's thing. Haven't had a problem yet in 300+ days in the coach, about 30 of them dry camping with gen set charge. The battery monitor kit has been doing a good job at telling me the overall battery condition and state of charge.

If we don't move up to a DP when my current battery does decide to retire I will replace it with the taller Lifeline or Trojan AGM.