Opinions on backup chargers for Mid size battery bank

southerndiver · March 2016

I have six Trojan IND29-4V batteries for our off grid home. Total of 3200 amp hours @ 12v.

It looks like most readily available chargers are 75-100 amp max output. Anyone have preferences on any of the larger chargers that may be connected in parallel with a smart controller??

How large of a charger would you use with this size of battery bank?

BB. · March 2016

In general--For an actively cycling system, I would suggest a minimum of 5% to 10% rate of charge--Or 160 to 320 Amp @ 12 volt charger.

Iota makes some relatively rugged/reliable battery chargers... But the largest is only 90 Amps @ 12 volts--So you would be looking at 2-4 of them in parallel. And Iota do not have power factor corrected AC input--So, they can take a fairly large genset to power them:

http://www.solar-electric.com/batteries-meters-accessories/bach2/bach1.html

Perhaps some other folks here have suggestions for high amperage 12 volt battery chargers.

You may be committed to 12 volt power system... But given the high current that these batteries can draw/supply @ 12 volts--Is there anyway you can look at re-wiring to a 24 volt battery bank? That would cut your current flow by 1/2.

-Bill

southerndiver · March 2016

I bought this stuff from someone that spent a lot of money without really understanding what he was doing. I have three Outback Charge controllers on the PV that I can configure for whatever battery bank voltage I want , and of course its simple to reconfigure the battery bank to 24vdc,,,but There are multiple high wattage pure sine wave inverters that are 12 vdc input only( as far as I can tell) that would be expensive to replace

Probably going to end up with two 90 amp Iota chargers in Parallel, anything more than that and would need a larger generator also. Probably should just tell wife to stop using the hair dryer

thanks

BB. · March 2016

Yea--The inverters are the sticking point. I would at least look at replacing the multiple 12 volt Inverters with a single 24 volt inverter.

There are also inverter-chargers (combined AC inverter and AC battery charger) that are pretty nice. But, not cheap.

That battery bank can support a hair dryer--And so can the Outback (60-80 amp) solar charge controllers.

If the system is going to grow--Look at your end needs. There are reasons we suggest going from 12 to 24 to 48 volt battery banks as the systems get larger.

-Bill

Dave Angelini · March 2016

Where you live can help make the transition away from 12V much easier. I am guessing that the south part of your name is the location?

Winter is long gone if you are in the southwest US. Get more solar and it will be easier to re-wire later than buying 12 battery chargers.
Many of my clients do not need a non-solar battery charger or a generator. It sounds daunting to many but with the right design/location pretty easy.

zoneblue · March 2016

So often people come here asking the question they least need to be asking. The right question as others have alluded to is how to make this into a balanced system. Its off grid right? so the math is easy to grasp. Sell the inverters on ebay, and put the proceeds into the correct inverter/charger. If you want to go this route, outline clearly all the gear you have and we can do a design with you. As Dave said solar is now cheap and thats where you want to focusing.

southerndiver · March 2016

I have a crapload of solar available, just asked a simple question if anyone had preferences on large backup chargers. System has been running fine for years why would I want to tear it apart and sell components??

never mind

706jim · March 2016

A hair dryer is not that big of a deal to run. I used to run one from 4 GC's and a Trace 1500 watt inverter. If you think about it, a hairdryer doesn't really run that long compared to say an air conditioner, stove or other high amp load.

I don't think using one would make much of a dent in that huge battery bank.

vtmaps · March 2016

southerndiver said:

System has been running fine for years why would I want to tear it apart and sell components??

You are dealing with a bunch of folks who like to design optimal systems. 3200 ah at 12 volts is not an optimally designed system... you could have the same batteries hooked in series at 24 volts and cut your currents in half. At 48 volts (which you cannot do with your batteries), you would only need one controller and one battery charger (or inverter/charger).

It sounds like your system is running up against some practical limits... that's why you're getting all the opinions rather than the answer to your question.

If you want to find large battery chargers, look to the forklift battery companies. Beware that most large, industrial battery chargers use charging protocols that are not very compatible with the typical RE (renewable energy) charging protocols.

An industrial battery charger may use the terms 'bulk' and 'absorb', but they do not have the same meanings as those terms in the RE industry. They often use a constant current stage... and they assume that their measured output goes entirely and exclusively into the battery... in other words, no loads or other charging sources.

Some 'smart' battery chargers, before they start charging, run a series of tests on the battery to determine its condition or state of charge. That also doesn't work when the battery has a load or another charging source.

--vtMaps

Opinions on backup chargers for Mid size battery bank

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