Do I have to disconnect my converter when charging

[Van Go]

I am currently set up to charge my battery using a Schumaker charger...run off my generator. My question is, do I have to disconnect the factory installed converter from the battery when I charge it with the Schumaker?

 

[highdesertranger]

you shouldn't have to. but to be on the safe side check and see what the max voltage is for the invertor, then check your battery while charging to make sure you are within spec. highdesertranger

 

[Van Go]

@hdr, thanks for the reply. I don't have any specs on the convertor. Don't know who made it. Don't want to disassemble the whole wiring mess ....I think I'll play it safe and disconnect it since there is some doubt. Am I correct in stating that I am backfeeding the convertor if I connect the charger?

 

[Optimistic Paranoid]

Just off the top of my head, I would say anyone who has solar panels and a converter is backfeeding the converter whenever the solar panels are charging, and no one ever seems to unhook the converter for that.

Regards
John

btw, notice that your post said CONVERTER and HDRs post said INVERTER.

 

[Van Go]

@op, thanks for pointing out the in vs. con thing. My original thought was like yours. If you charge your battery with your alternator, solar system, etc. you don't see people disconnecting the converter.

 

[Van Go]

just to clarify things. I'm talking about the device that plugs into shore power and then provides 120vac and 12vdc

 

[SternWake]

There is no danger of running multiple charging sources at the same time.


However, they might not combine their amperage as planned or desired.

Smart battery chargers, when hooked to the battery, and they see 12.8 volts plus, they consider the battery fully charged and will apply only enough amperage to raise the battery voltage to ~13.2v which is  considered the  float stage.

This is fine if the battery is indeed fully charged or nearly so.

BUT,  If the battery is not full, and the voltage is only artificially high, because it either recently saw alternator charging current, or if the Converter has already gotten the battery voltage above 12.8v, then it will not add anything, or very little charging current.

Why does this matter?  because if the battery can take 30 amps to be pushed upto 14.4v as it is still less than 80% charged, but the converter/charger sees an artificially high surface charge voltage, then it does not try to achieve 14.4v and the actual charging occurring is very very slow. 
And a battery needs about 2 to 4 hours in the 14.4v range in order to reach full charge that same day after a depletion to 50%

What might take 2 to 4 hours at 14.4v, can take a week or more at 13.2v.  And certain flooded batteries that have seen some cycling and abuse in the past might never have their specific gravity return to the maximum when fed only 13.2v, no matter how long it is held there.

So what to do?  one needs to be smarter than their 'smart' charging sources.  One can apply a larger load to the battery, draw to voltage below 12.8 or further, and then plug in and start the charging sources, then remove the temporary loads.  If one can start both charging sources at nearly the same time when battery voltage is still below 12.8v, then both will combine their amperage until a certain point.

Some converters are fixed voltage, such as 13.6v, and when both charging sources together get the battery to 13.6v, then the converter will stop contributing any current, and the other battery charger will complete the rise to ~14.4v on its own.  This might slow charging a little, it might not.

Lots of variables.

So basically, if your automatic battery charger instantly flashes the green light and tries only for 13.2v, you have to trick it by lowering battery voltage to below 12.8, and restarting the charger.

If time is a factor, and you want both charging sources to feed a 50% depleted battery together, then they should be turned on at  the same time or as close as possible to doing so.

And this will only be successful if the voltage is held below 12.8v when the chargers kick on.

Some 'smart' battery chargers will apply current, then stop and see how fast the voltage drops on its own, and then decide as to what voltage to shoot for and at what amperage rate, and outsmarting such a smart charger and getting both to contribute their maximum current, might be futile.

Do note that if powering 12v devices while an automatic charger is going, then the DC loads on the rv's electrical system will confuse the  charger which is trying to achieve a steady voltage, and it might shut off thinking something is wrong with the battery.  Converters are designed to power dc loads while charging the battery, but since there are loads on the battery, the charge profile cannot be made Ideal as the converter has no idea what is going to power devices and what the battery is accepting. It basically says okay 2 hours at 14.4 then revert to 13.6, when 4 hours were needed at 14.4v.

Bottom line is do not fear running 2 charging sources at the same time.  Some trickery might be required to get them to work together to charge the battery at a faster rate.

And do not worry about the higher charge rate.  Depleted batteries can accept huge currents easily, and as long as the voltage is held below ~ 15 volts, it is perfectly safe to do so, despite the 'trickle charge' mentality that is often spouted as best always in every scenario, because grandpa once said so.

High charging currents can indeed wake up a battery which has been chronically undercharged, and in the case of many AGM batteries, is required to get a satisfactory cycle life from them.

It is better to get the battery to fully charged status as  a high rate, than it is to begin the next discharge cycle having only got the battery to 92% charged because the initial charge back up to ~80% took too long.

If one has all the time in the world to plug in and recharge, then one need not really worry at all.  but if one has 8 hours and very depleted batteries, then one only has about 4 hours to get the battery to 80% charged, because that last 20% is going to take ~4 hours no matter how powerful any charging source might be.

Wfco converters come as standard equipment on many RV's.  They are not very good or long lived converters.  Usually the charging circuit is too long and too thin and the converter never shoots for 14.4v.  Thicker wiring might help it attempt to get the battery to 14.4v, it might not.

When the Wfco converter fails, as it will at some point, there are simple drop in replacements which can indeed shoot for 14.4v and will do a much better job charging the battery and extend its useful lifespan  Progressive Dynamics, and Iota, and powermax are 3 of the better products, and they come in  different amperage flavors upto 100 amps.

I would lean heavily toward the progressive Dynamics, because it has a button one can push and it will force the unit to seek 14.4v for 4 hours, and one can also use this button to force 13.6v, or 13.2v. 
  it is a fully automatic charger, but if the surface voltage is artificially high, and one is running a generator to charge a depleted battery, forcing the converter to seek 14.4 will force the converter to its maximum output and charge the battery as fast as it can, and allow one to run the generator for shorter periods and return more charge into the battery.

Running the generator to power the Wfco converter to charge batteries as fast as possible is like shooting oneself in the foot.  A waste of gas, and the batteries will live their severely shortened lifespan undercharged, and perhaps not even  be charged enough to run the DC loads overnight.

 

[Van Go]

@sternwake, thanks for that very expansive reply. a lot of information there. I'm really just concerned that I might harm the converter by connecting a charger to the battery. you indicate that multiple charging sources are not a danger. i think that is the answer to my question. just don't want to see that "magic blue smoke" you guys talk about.

 

[SternWake]

@sternwake, thanks for that very expansive reply. a lot of information there. 

I included the extra info, as you might find your automatic charger might see surface charge from the converter or alternator or other charging source, and decide to not charge your battery(s) at the rate it desires to be happy and perform properly for an acceptable timespan.

Batteries hate to be cycled over and over without getting to 100% state of charge at least every few cycles, and AGMS are even more petulant in this matter.

If you know the battery is depleted, but your automatic charging source prefers to flash the green light and only achieve 13.2v or 13.6 on the AGM setting, it is not doing you or it, any favors.

A Progressive dynamics PD9245 installed, would make your automatic charger unnecessary.  If space becomes an issue, or you get tired of having to be smarter than your smart charger by tricking it into doing its job, then the converter upgrade to the PD9245, is worthwhile.

Best of luck.

 

[Milk Hauler]

Haha! Stern Wake is the go to guy so you don't zap your equipment or worse, yourself.
[emoji95]

 

[SternWake]

One thing I should have included in post#9, is to note is that some AGMs indicate they have upper limits on their maximum amperage. These are generally the less expensive AGM's and they will say not to exceed a 30% rate, or no more than 30 amps for a 100 Amp hour battery.

So the PD9245 , at 45 amps, might be too much charger for such a battery. It is possible that this high of a rate on these lesser AGMs could cause it to vent slightly. Hardly instant death, but damage it is cumulative.

Other higher $$ AGMS like Lifeline/Odyssey, and Northstar have basically no achievable upper limits on charging amperage.

Odyssey says their 100AH group 31 can safely accept 500 amps.
Lifeline says their 125AH group31 can accept 350 amps
Universal Battery says their group 27 should not be charged at more than 30 amps.

So the Ideal battery charger for any specific AGM battery, is not necessarily ideal for any other brand of AGM battery.

Automatic battery chargers paint all AGMS with the same brush though.

 

[ccbreder]

I am currently set up to charge my battery using a Schumaker charger...run off my generator. My question is, do I have to disconnect the factory installed converter from the battery when I charge it with the Schumaker?

If you have the Schumaker plugged into the generator, my assumption is you are not connected to grid power. Your converter is not powered, and unless something is bad in the converter, you will have no problem charging with the Schumaker. If there is something bad in the converter, it has already run your battery dead and you know that.

 

[ZoNiE]

If you think about it, a fully charged battery back feeds a converter when not plugged in.

 

[highdesertranger]

my bad with the converter/inverter mix up. with a converter you shouldn't have an issue. highdeserranger

 

[Sabatical]

If you have an adequate solar setup, couldn't you just disconnect the converter wiring so any chance of it goofing up the process is negated?
On our travel trailer, I plugged the shore whip into the output side of the inverter in order to power the 120v receptacles. When I noticed a hum from the converter I questioned it's necessity. Our system is far larger than our full timing needs and we never plug into shore power. It seemed easiest just to remove the converter from the loop.
I had also bought a 45 amp smart charger and installed it in the mix, but have yet to use it in 8 months of camper living. Cheap insurance I guess.

 

[ZoNiE]

I don't plug into shore power when I store my trailer. My 400W of Solar and MPPT charger do a better job on the batteries. I water them much less.

 

[ccbreder]

The battery will not back feed into the converter. Otherwise it would kill the battery when not charging. If the converter is bad, then it may back-feed, but only if the converter is bad. If the converter is bad, throw it away.