Battery charger options for NON-12v banks?

[Rednecktek]

Hey gang, I know some of you out there have battery chargers you plug into a generator to recharge your banks when the sun isn't playing nicely. I'm throwing together 240Ah worth of 24v FLA batteries, so I figured I'd need at LEAST a 25a battery charger to get them fed in the krappy winter. I'd really rather have 50a of charging so it doesn't take all bloody week, and if I make more banks I'll need yet more amperage.
Problem is the only things I'm finding that will even come close are either $800! or only run on a timer and don't do the whole absorbtion/bulk/things.

Anyone got recommendations for a better value option? At worst this thing will be used about once a year.

Thanks all!

 

[DThames]

No easy answer but is there a real need above some bulk charging? I mean if you can bring the batteries up to 85-90%% in X hours, is that not okay, considering the sun will shine again someday soon.

 

[rmaddy]

One possible solution is the Victron line of Blue Smart Chargers. The IP22 version, for example, comes in 24V and 8, 12, or 16A. The 16A version sells for a bit over $200. The nice thing is you can buy multiple chargers and connect them in parallel. They have Bluetooth and can be setup to perform synchronized charging making them act as one larger charger. Makes it easy to add more as you need more amps.

Blue Smart IP22 Charger - Victron Energy

The Blue Smart IP22 Charger is the new professional battery charger with built-in bluetooth. Find a Victron Energy dealer near you.

www.victronenergy.com

 

[OzSolar]

This has always been a challenge for me, especially outside of 12v.

Higher priced inverters normally have very stout chargers built into them. More affordable inverters don't have a charger so now you need a decent battery charger which still often stinks (low amps, no adjustments, etc.) compared to the ones built into most inverter chargers so you probably were better just starting off with the higher priced inverter. Plus you have an automatic transfer switch built in. But... that's not what you asked about, sorry.

Scouring eBay for a deal on a used inverter-charger like an old Trace modified sine DR3624 inverter might eventually pay off. You might also keep your eye on used industrial chargers like for scissor lift & forklifts. Don't forget about Iota Chargers as well.

Otherwise the best new charger I've bumped into is this Aims recommended by Will which is rated for 37.5v at 24 or 75A at 12v.

 

[Rednecktek]

OK, so next question on C rates...

Going under the understanding that 0.1c is 1/10th the AH rating of the battery...

If I have a battery bank made of 2s4p batteries, in 24v, and use 120Ah FLA's, what should be my charging rate?

12a because that's 1/10th of a 120Ah battery?
24a because there are 2 batteries in series?
96a because that is 4 banks?
960a because it's 12a for each of the 8 batteries?

 

[DThames]

Series circuits have the "same current", which not "equal" but one in the same. So any current that is in battery #1 of a series string, is also in battery #2 of that same string, so you would never do anything but take that series current as 1x. If you want 0.1c of 120ah, that is 12amp times 4 parallel, 48amps.

 

[OzSolar]

10% of the C/20 is what Rolls says in thier manual which is the best written resource on FLA batteries I have found.

 

[rmaddy]

Going under the understanding that 0.1c is 1/10th the AH rating of the battery...

If I have a battery bank made of 2s4p batteries, in 24v, and use 120Ah FLA's, what should be my charging rate?

You have a 24V 480Ah battery bank. 0.1C of 480Ah is 48A.

 

[Warpspeed]

How about a used fork lift battery charger ?
These are available in various sizes and voltages, and an old one that has maybe seen better days, might not be that expensive for something pretty gutsy.

Quite often when a very expensive fork lift battery is being replaced, the battery supplier INSISTS that a new charger be bought as well, or the warranty might not be honored. So perfectly good secondhand chargers can sometimes be had for scrap value.