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DC power supply


Simon Paine

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The supply that you linked to would work just fine, with only one thing to consider: that is, the output voltage range from the supply. It is stated as OUTPUT VOLTAGE ADJ. RANGE: 10.8~13.2V, with 13.2 being the upper spec. Most of the cart power supplies that I have built using the float routine across the battery, have the ability to output up to around 13.8 vdc. For everything to work at optimum, I think a fully charged battery would prefer to have around 13.6 vdc when floated across. This would insure that the DC really "floats" since it is a voltage that is higher than the nominal fully charged battery. I really don't know enough about electricity either to assess how significant this observation is.

As far as hooking things up together, it is fairly straightforward. The AC (mains) connection is just hot (load), neutral and ground (earth) and the DC connection (output from regulated DC power supply) is just + to + on the battery and - to - on the battery. The XLR 4-pin outputs that you will connect your gear to should be fed from the same battery terminals you have connected the regulated power supply. I also make sure to put a fuse or a breaker in line on all hot leads: that would be a fuse on the output of the regulated power supply to the battery, a fuse on the output (+ terminal on the battery) on its way to your XLRs.

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thank you jeff, your're always very helpfull.

regarding the OUTPUT VOLTAGE ADJ. RANGE: 10.8~13.2V, with 13.2, i've searched on internet the MEAN WELL S-150-12power supply you linked in a previous post (here's the link http://www.meanwelldirect.co.uk/product/S-150-12/S-150-12/default.htm) and that one also seems to have that same adj. range value of 10.8~13.2V, but an ovp stated between 13.8 ~ 16.2V.

so, maybe these are two different things?

then, which kind of fuse could you advice to use for the purpose?

thanks again..

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thank you jeff, your're always very helpfull.

regarding the OUTPUT VOLTAGE ADJ. RANGE: 10.8~13.2V, with 13.2, i've searched on internet the MEAN WELL S-150-12power supply you linked in a previous post (here's the link http://www.meanwelld...-12/default.htm) and that one also seems to have that same adj. range value of 10.8~13.2V, but an ovp stated between 13.8 ~ 16.2V.

so, maybe these are two different things?

then, which kind of fuse could you advice to use for the purpose?

thanks again..

I think the discrepancy may be that the voltage adjustment range spec stated is not necessarily what the unit can do. So, maybe even if it says the range is only up to 13.2 it will go higher --- I don't know the answer to this.

As for fuses, I have gotten away from using replaceable fuses in favor of circuit breakers, usually 10 amp rating. I have two reasons for doing this: one is that I don't have to worry about having new fuses with me to swap out if one should blow, and the other is that I use a type of circuit breaker that is also a push-pull switch --- I can turn off the output to the XLRs, I can turn off the output of the regulated dc power supply, etc. These breakers are many times more expensive than a fuse but that's the way I do it.

post-1-0-00069700-1329603216.jpg

ordered through Digi-Key --- I think about $25.00.

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i've spended the last two days studying and reading about fuse protection for our gear, but i think i was not completely able to get a proper conclusion..

in the last post jeff said the he use a 10a circuit breaker. now, reading the specs of a lot of mixers/recorders, i found out the they require much less external current than 10a...

for example:

Zaxcom Fusion 10 to 18 VDC @ .7 A;

my AD149 Mixer DC source 750mA at 12V;

Sound Devices 788 external power from 10–18 VDC (4 amp minimum);

Nagra VI input voltage range is from 9-16 Vdc (max) and the recorder requires a minimum 3.3 A;

...

so what's the best way to go? it is to see what's the total amount of amperes required by the cart and select the nearest fuse, or it's to insert a fuse on every single line matching the specs of each device (so, if i understand, for a really effective protection, it'd be 1A fuse for the ZaxcomFusion, same for ad149, 5-6A for either the SD788 or nagra VI,...)?

i'm sorry if i'm saying fooleries, i'm only trying to learn more on the subject...

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in the last post jeff said the he use a 10a circuit breaker. now, reading the specs of a lot of mixers/recorders, i found out the they require much less external current than 10a...

I freely admit that I do not fully understand these things --- someone with greater fundamental knowledge of electricity should respond to this. I think that what I am doing with the 10 amp breakers is protecting for essentially a dead short situation, actually the only fault that I believe I need to provide for with the power supply. Since the overall current amperage of the supply is far in excess of the demand that any of the gear will need, the 10 amp rating on the breaker seemed appropriate since the power supply itself is able to deliver up to 10 amps.

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As far as I can see, a fuse on the input protects against surges, and is rated in AC amps. A power supply such as the Remote Audio Meon has a fast blow fuse rated at 5A @110VAC. This is purely on the input side and mostly to protect the unit from spikes coming in.

The outputs on the Meon are fuse protected at 18A @13.8VDC. This would be to protect against bad wiring or faulty connections, causing shorts.

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  • 3 weeks later...

So I've started the overhaul of my cart powering system.

Out is the Xantrex True Charge :

truecharge.jpg

And 30 AH SLA battery.

And in there place: 3 V-mount batteries (Swit 190 WH model) Mounted on V-lock plates.

01.jpg

and a 13 amp DC power supply, (variable output, I've set mine to 16.5 volts.)

I'm also incorporating a voltage detecting relay, that will seamlessly switch between the Power Supply or the batteries (whichever has the higher voltage) to create an uninterruptible power supply.

This system should save me quite a bit of weight and give me a longer runtime should I be cut off from AC power. Since I already had the V-mount batteries and charger (I use them for my bag system) this seemed like the best solution. My logic was also, that the V-mount battery seems to be the most common high capacity battery found on set these days, so if worst comes to worst and I'm really up the creek without a paddle, I could probably borrow a couple from camera dept.

Using the three v-mount plates allows me to be able to switch out one battery at a time without losing power to my cart, should I need to swap out dying batteries.

Here is the rough in. I'll be doing the final install and wiring this weekend. I'll also add some LED lighting to helps see whats going on down there, during use on dark sets.

post-55-0-51220200-1331256854.jpg

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yes, this won't charge them. My charger will be plugged in somewhere close by, but I didn't want to integrated a charger into this system right on the cart.

My last system was based around a charger. But I'm trying a different route.

This will be "hot swappable" if you switch out one V-mount battery at a time.

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  • 4 weeks later...

I am also trying to work out my cart power and would like to float a DC power supply over my 40Ah Lead Crystal battery I am trying out.

I found this chart of the Mean Well GS220 series and am trying to figure out if I want 12V - 15Amp OR 15V - 13.4Amp??

http://www.meanwell.com/search/gs220/default.htm

As Jeff said earlier I expect I need to have around 13.4Volts on the output.. which DC power supply did you end up going for Simon?

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Mean Well makes good stuff but I don't think you want the one you linked to housed in a plastic case. The supply can get hot and I have always gone with the ones in open frame metal case with perforated cover (for ventilation). You will want one that has adjustable voltage output in the range of 12 vdc to 14 vdc and probably no more than 12 amps. The adjustable part is difficult to determine at times when reading the published spec (it will be stated as being adjustable, 12 volts +/- 3 volts for example) and the plastic one you are looking at is probably not adjustable at all.

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About fuses (and circuit breakers), Justin and Jeff have it right.

You don't want to just figure your total current and then use that size of fuse. If you do that, you'll be blowing fuses (or throwing circuit breakers) on a regular basis. The purpose of a fuse is to protect your circuits when something goes wrong and pulls too much current (such as a short, etc.). A fuse is there to protect from further damage, or from damage to other components, or to prevent you from becoming a source of cryptic smoke signals.

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Thanks Jeff.. I was thinking that the ventilated case would soon get filled up with dust/garbage/beach sand etc on some locations but the adjustable output voltage is obviously important and the enclosed type does not seem to be adjustable. If you and Scott say the Mean Well S150 are ok.. I guess I cant go too far wrong. Just ordered the 13.5V version adjustable from 12V to 15V.

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"Thanks Jeff.. I was thinking that the ventilated case would soon get filled up with dust/garbage/beach sand etc on some locations"

I guess I didn't really understand what you were building. My cart power supplies are all built in one enclosure, battery, regulated DC power supply, fuses/breakers, distribution connectors, etc. This enclosure is either a rack mount chassis box or a Pelican case and in both instances the items are protected from the elements.

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Aaaah I get it Jeff. I wasnt planning on enclosing the power supply. Doesnt having it in a Pelican case or such negate any ventilation that the case might offer? I think I will just raise the power supply up and mount it inside my rack case where it will get some protection from the elements and hopefully still some airflow to keep it cool.

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"Doesnt having it in a Pelican case or such negate any ventilation that the case might offer?"

I forgot to mention that I also provide ventilation for the case that houses the items. I either put louvered plate or drill vent holes with a good convection path in mind to provide air flow with minimal contamination from the outside elements.

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I'm also considering a change to my cart setup. I'm pretty happy with distribution (I have a couple BDS's as I swap between bag and cart work constantly), but am thinking of going over to a larger capacity battery to stop the constant battery shuffle.

What's the current thinking for larger capacity batteries and chargers?

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I strongly suggest that using any power supply that is a CHARGER, particularly one that has staged charging, across the battery that is powering your equipment, is a really bad idea. You may not have had problems or maybe you are suggesting the Guess chargers to be used just as chargers for your batteries (while that battery is NOT powering your equipment).

Hi Jeff,

I'm just curious if the way I have my cart power set up is the same as you're referring to here... and if so, what are the dangers?

I'm running shore power (heavy guage stinger) to a Guest 10-amp marine charger which is connected (fused) to a 92AH AGM battery -- this is connected to a Xantrex 1800i inverter which feeds the main box on my cart. I've never had any problems with this set-up, and have gone as long as 8 or 9 hours on the battery.

If I understand correctly, might the possible danger be in a full load from the Xantrex on the battery being interpreted as a dead battery, this causing the charger to over-charge the battery / overheat?

I've operated this way for years now without a problem, but I certainly don't want to be doing anything that could be potentially dangerous to anyone and/or my gear.

~tt

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I'm just curious if the way I have my cart power set up is the same as you're referring to here... and if so, what are the dangers?

I'm running shore power (heavy guage stinger) to a Guest 10-amp marine charger which is connected (fused) to a 92AH AGM battery -- this is connected to a Xantrex 1800i inverter which feeds the main box on my cart. I've never had any problems with this set-up, and have gone as long as 8 or 9 hours on the battery.

I've operated this way for years now without a problem, but I certainly don't want to be doing anything that could be potentially dangerous to anyone and/or my gear.

~tt

I'm sure what you're doing (have been doing) is fine, otherwise you would have had a problem by now. My caution only relates to the use of some battery chargers that have staged charging cycles that can produce noise (in audio equipment being powered while charging). Evidently your setup and the specific Guest charger you are using is not causing this sort of problem. I wouldn't worry about it.

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  • 3 weeks later...

A cart power supply is something that takes a lot of thought.

First, you need to count up all of your DC load and size the system appropriately. Then you need to make a decision about how many hours of full battery operation you want and size the battery appropriately. You may run out of space or weight before you have enough battery. The actual discharge is not linear so don't assume that a 10 Amp/hour battery will give you 1 hour at 10 Amps load.

Most "quick" battery chargers can put noise into the DC buss so it is necessary to isolate the batteries from the DC buss when AC is applied. The lower loss method is a relay but that may cause a hiccup in the DC buss.

Diode isolation between the batteries and the AC to DC supply works well but you will lose some power across the diode. Set the output of the AC to DC supply slightly higher than the batteries under charge.

Trying to charge the batteries is tricky if you want to do it off of a single AC to DC supply. If the AC to DC supply voltage is set too low you'll never charge the batteries enough. On the other hand if the AC to DC supply voltage is set too high you'll cook the water out of "gell cell" batteries. Figure that the total load on the AC to DC supply is the DC load of the cart equipment plus the battery re-charge load. The battery re-charge load should be at least twice the cart DC load if you ever want to get the batteries back to full charge. Also remember that the atual charging voltage of the battery varies with temperature.

Baisc lead-acid "gell cell" batteries come in different designs. The smaller ones are designed for intermittent float applications and do not give many full cycle charge/discharge cycles. The ones designed for full discharge are larger. Look for ones that are used in motorized wheelchairs.

Be very, very careful with lithium batteries. Their charging requires a lot more care than lead-acid and is best done with a system that a manufacturer recommends. If you don't charge lithium batteries properly you will have a fire.

It is best to have several over-current protection devices between the source (battery and AC to DC supply) and the load. If you never have a cable short then you can skip this, but a short in the field might just burn up your cart. Fuses have lower voltage drop than circuit breakers but you need to carry spares.

I've done several systems. And learned a lot over time. There is no perfect solution and you need to understand all of the compromises to find an optimum balance between cost, performance, size and weight.

Bill Ruck

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