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GlennWest

Dc/dc step down coverters

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2 hours ago, GlennWest said:

I don't have a motorhome though. No onboard generator, so no real need for 12v batteries.

Glenn, As long as you have a quality high voltage (say 40 to 60 or so VDC) to 12 VDC Converter with sufficient power to operate all your typical 12 Volt Appliances (Vent fans, furnace, water pumps, slide outs, lights etc) I agree you have no need for additional 12 volt batteries.... BUT this is a choice and preference, sure there are other suitable methods should one so choose for whatever reasons such as the method posted above ... Hey you already have plenty of electricals lol

John T

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I don't have much to add to the technical specs but a cheap converter without a battery could fail.  Moving the slides and jacks on a Teton is difficult without power.

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7 hours ago, Randyretired said:

I don't have much to add to the technical specs but a cheap converter without a battery could fail.  Moving the slides and jacks on a Teton is difficult without power.

Who said I had no battery. No 12v battery but a hugh 48v battery pak. 21KWH

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FOR THE RECORD, a typical RV has an internal often referred to as a "Converter/Charger" or just "Charger" which Converts 120 VAC shore power down to 13/14 VDC to Charge the 12 Volt Batteries.

HOWEVER what Glenn needs and is talking about is a "DC to DC Converter" so he can uses his 48 Volt Battery bank (Converted to 12 Volt) to power his RV's 12 Volt lights and vent fans and water pumps and furnace and slide motors etc. etc.

His 21 KWH 48 VDC Lithium Battery bank can power SEVERAL of our RV's lol much more then a typical say 100 Amp Hour to even 500 to 1000 Amp Hour 12 Volt Battery banks many use.

John T   

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On 11/21/2019 at 11:16 AM, GlennWest said:

That why wanting to try these Chinese units. 100.00 dollars so if it doesn't hold up not out of a lot. 

What I was trying to say if the DC to DC converter fails the slides and Jack's are without power.  This can be very inconvenient.  A 12v battery for backup could be mighty handy.

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Yes, I think everyone understood John. The question is whether he wants to go from his 48 V to converters To his load OR go from 48 V pack to small 12 volt pack to load. The idea being that the 12 volt pack could better handle any draw surge(I am thinking small lithium pack) and be less at the mercy of any malfunction in the 8 to 12 converters. 

There is no magic either way. Just a design question. 

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37 minutes ago, sushidog said:

Here's a 60a 48-12v one that goes up to 56v. They claim up to a 95% conversion efficiency.It's only $120 too.

 

Do you feel lucky?

Edited by hemsteadc

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In the coach I have li which is a little higher that start voltage, , so I just have a small battery charger off the inverter charging the start batteries, not so efficient but works.

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16 hours ago, GlennWest said:

I don't have a motorhome though. No onboard generator, so no real need for 12v batteries. Slideouts are on 50 amp relays. 

Have you checked the full load amperage of the slides? 

Any leveling system?

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I have electrical leveling Jack's. I had thoughts of changing out to hydraulic but see lots of issues with others. So stayed with what works. There are 40 amp circuit breakers on my slide outs. The only time they tripped was reversing direction while going in other direction. Also my 120v to 12v converter is 50 amp. So I choose 60amp for buck converter. 

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7 hours ago, sushidog said:

Here's a 60a 48-12v one that goes up to 56v. They claim up to a 95% conversion efficiency.

https://www.amazon.com/Cllena-Voltage-Converter-Waterproof-Transformer/dp/B07QVJNQF2/ref=sr_1_6?keywords=power%2Bconverter%2Bdc-dc%2B48v-12v&qid=1575342138&sr=8-6&th=1

It's only $120 too.

Chip

That is the one I originally looked at. States not to use when charging battery. That is why I passed on it.

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Only one comment on this - other than that I think the data is there to make a decision.

High output buck converters - especially those that are stepping down a big "step" - typically do not handle large loads (near their ratings) well. Especially surges. So be aware of that and prepared to remedy that situation in your design, should you encounter it. Since your largest load is well below the converter rating, you may be fine. You probably have no way to figure that our without trying it. 

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12 hours ago, Daveh said:

The question is whether he wants to go from his 48 V to converters To his load OR go from 48 V pack to small 12 volt pack to load. The idea being that the 12 volt pack could better handle any draw surge(I am thinking small lithium pack) and be less at the mercy of any malfunction in the 8 to 12 converters

Good Point Dave, if he goes with a 48 to 12 Converter and no 12 volt batteries whatsoever, he needs a good quality and a sufficient rated, especially surge rating, DC to DC Converter. I prefer as simple as possible and as few as possible devices and appliances and black boxes, that's one reason Id opt for a SINGLE 120/240 Volt Inverter with enough power to run allllllllllll his 120 and 240 loads and no extra 12 volt batteries IF FEASIBLE THAT IS...…….?????? But of course, your method of having a 12 volt battery certainly has some advantages.....

Best wishes Dave, nice sparky chatting with you

John T

Edited by oldjohnt

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Well, that converter went to someone in NY. How Port Arthur TX and NY got confused with is beyond me. Well got refund from Amazon. So back in searching again

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