Inverter vs Converter

[mlh1936]

I've been doing research on battery tenders,minders,inverters with built in chargers and converters. I noticed in the archives that there was hardly any mention of converters. Are there any disadvantages to using a converter? We rarely ever do any dry camping so feel I don't need to spend the big bucks on an inverter. All the comments pro and con on tenders and minders have confused me. Am now using two 12V AGM batteries for the house system. Most of the house is on 110. Does anyone have a recommendation on a particular converter that could safely keep my batteries charged?  Or am I better off just trying to determine which smart charger is best? Thanks very much.

[technomadia]

A converter will take A/C power (ie. 'shore power') and charge your 12v batteries, and allows your 12v systems to work while you're plugged in running the rest of your 110 household.  (Such as an 12v lights, outlets, vent fans, fridge controls, water pump, etc.)  

An inverter w/ charger will do that AND allow you to run your 110 systems off the batteries when you are not plugged in.  Which can be handy even if you only occasionally blacktop dry camp while in transition between locations (such as Walmarts, rest stops, etc) and want to run things like your coffee maker, charge laptops (without needing 12v chargers), run a TV, microwave, etc.  If those things aren't important to you, than the expense of household wide inverter may not be worth it, and you can always get small inverters that plug into 12v cigarette lighter style outlets to run a device or two at a time as needed.


In either case, as you're using AGMs, it would be wise to seek either a converter or inverter with smart charging profiles for the best battery life... as they should be charged in stages.

- Cherie

[luvrbus]

? Cherie brings up the topic AGM should be charged in stages why, is that only for rv use the ones in other applications like air planes the alternator charges the battery till it reaches full capacity doesn't seem to affect the battery life just a inquiry on my part so don't get upset just asking.

The Concord rep says it doesn't hurt their batteries they do recommend stage charging but like he told me the solar chargers don't have great control for charging and their largest battery market is for the off grid crowd ?

[technomadia]

Well, technically - all lead acid batteries prefer to be charged in stages.  Most chemistries can 'fast charge' up for the first 80%, then ramp down the rate for the remaining 20%.

However, AGM batteries can be more harmed by not stage charging, as there's not as many options for counteracting for the damage (with flooded, you can top off the distilled water, do an equalizing charge, etc.) While AGM batteries can be equalized, it's a more delicate process.  

In our opinion, if one is going to shell out the extra cash for AGM - investing in smart charging is a wise component of the battery setup to prolong that extra expense.

And yes, these things can become more important in a house system designed for off-grid living than a starting battery application charged directly off an alternator.


Charging off solar does make it difficult to reach a full charge - as that last 20% of charging is slower and the day is only so long. Many who are focused on the health of the batteries will do a regular topping off by generator or other means.  Or some just factor in a potentially decreased lifespan of their batteries by not worrying about topping off beyond 80%, and having a lower depth of discharge, into their long term battery costs.  

That's one of the many reasons we decided to experiment with Lithium Ion for our buses' batteries, as they don't need to get a regular full charge to extend the health, and we feel they are ideal for the base of our upcoming solar install.

- Cherie

[opus]

I have a 70A Iota converter.  When we park we use it to run our 12v stuff.....which is mostly what we have shy a couple 110v outlets.  I have isolated it from the batteries though, so it doesnt do a thing to them.  I can have it charge them with a simple switch throw, if need be.

[Sean]

... I noticed in the archives that there was hardly any mention of converters. ...

Actually, there are tons and tons of posts in the archives regarding converters, how they differ from chargers (whether integral to an inverter or stand-alone) and the pros and cons of both.  Here are two posts I wrote on this very subject (easier to link them than to retype it all here):
http://www.busconversions.com/bbs/index.php?topic=16283.msg175122#msg175122
http://www.busconversions.com/bbs/index.php?topic=8911.msg88297#msg88297

There are many more such posts in the archives with more particular details on converter installation, models, and so forth.  "Converter" is a very common word with more than one meaning, so it is important to structure your search query to get the results you want.  FWIW, Google's search is more flexible in this regard.  To search this site with Google, simply add "site:busconversions.com" (without the quotes) after your search term.

... why, is that only for rv use the ones in other applications like air planes the alternator charges the battery till it reaches full capacity doesn't seem to affect the battery life just a inquiry on my part so don't get upset just asking.

Well, it doesn't really reach full capacity, or else it overcharges and cooks.  The problem with most single-stage chargers, and this includes automotive alternators, is that they are strictly voltage-regulated (there is no means for measuring current or state-of-charge) with just one voltage set point.

If you set that setpoint (assuming you have an adjustable regulator) to the manufacturer's specified "float voltage" for the battery, then you can pretty much "charge" the battery at this voltage indefinitely without hurting it.  But it takes hours and hours and hours to get a battery to full charge at this voltage.  Because automotive batteries must recover most of their lost charge in anywhere from a few minutes to a few hours of driving, the alternator/regulator setpoint is usually set higher than this float voltage, to something closer to the battery's "bulk charge" voltage.

This lets the battery charge quite a ways while driving.  And mostly, it works, because virtually no vehicle drives 24/7.  But if you did, in fact, connect the battery to this voltage permanently, as would be done with a single-stage AC-powered charger while on shore power, you'd overcharge the battery and damage it.

All of the foregoing, BTW, applies to all lead-acid batteries, whether AGM, flooded, or gel.  Each of those has slightly different voltage settings, and AGM is slightly more tolerant of both over and under charging than the others.  But any lead-acid battery will have its useful life (in cycles) reduced by continuous or successive over or under charging.

What a multi-stage charger (and, BTW, these are available as alternator regulators as well) does for you is to give the battery a bulk charge rate to fill it back up to nearly full charge, then switch to a float rate to keep it there without damaging it.

The Concord rep says it doesn't hurt their batteries they do recommend stage charging but like he told me the solar chargers don't have great control for charging and their largest battery market is for the off grid crowd ?

Well, the Concord rep is a salesman, after all

BTW, my solar controller does have three charging stages (four, if you count the manually-activated equalization stage), as do most modern controllers made for off-grid use, so I am not sure where he is getting that information.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

[luvrbus]

I was talking to to him about the cheaper controllers like used on most RV's not the high dollar MPPT and PWM chargers chargers serious bucks when one pays 6 to 7 hundred for a charger fwiw I have a Blue Sky SB 2000E it is not that great for a 300$ controller


good luck

[bobofthenorth]

My farmer-understanding of the controller thing is that single-stage regulators like the internal regulator in most over the road alternators or any cheap automotive battery charger won't put a large charge into the batteries rapidly.  Over a long time they will get your batteries charged but it will take time. 

In the boating world there is a big emphasis on using 3-stage charging to control the propulsion engine alternator(s) as well as the inverter/charger.  I'm not sure why that concern doesn't carry over to the RV/bus world. For that matter I'm equally uncertain about why it is such a concern in the boating world.  The frenchy-bus has a simple connecting solenoid that links the house bank and the start bank while we are going down the road so both banks charge off the (internally regulated) alternator.  I suspect that is the most common arrangement on all RV/bus conversions but it is less common on boats.

[gus]

My 4107 came with a 45 amp converter which provides 12v power when parked and plugged in. It also charges the batts with a three-stage smart charger, works great.

It came without the 3-stage charger but I added it in the form of a kit.

[Uglydog56]

Technomads, could you point me in the direction of the 3 stage reg for alternators?

[luvrbus]

I can point you too one the Xantrex XAR regulator 200 bucks and not that great I just replaced the one on the S&S only works with a 3 wire alternator so I was told 

[Sean]

Technomads, could you point me in the direction of the 3 stage reg for alternators?

Balmar, hands down.

Ample power also has one that is quite good.

-Sean
http://OurOdyssey.BlogSpot.com

[robertglines1]

. Hi Mal; Best toMary. Been awhile.  If you are doing simple system like mine I just use a charger like we used on our tournment boat. It has 4 seperate chargers built in one unit I and don't know stages or how the technology works but it keeps the battery bank up in the boat that are deep cycle marine batt  and also the 31's (4 ea ) in the 89 Prevost are fresh. The boat batt are prob close to 7yrs old now. Availabe at any place that sell marine battery support chargers for bass boats.   Bass pro Shop.  About $250  Must be unplugged when motor running or it will fool your voltage regulator. This for info only. I know nothing about the new off grid Chriss and Cherrie  or Sean are working with.   Best to you Guys.   Bob & Judy     

[luvrbus]

I never used a converter like Bob I used a Iota 75 amp charger worked for me for 20 years and kept the batteries in good shape all 12v ran through the batteries the charger supplied the charge to keep the batteries up

good luck

[gus]

The Iota smart charger you guys are using is probably the same as the one in converters since they make converters. Can't figure out why a charger needs to be 75 amps unless it has a starting boost feature?