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Old 21-11-2014, 20:48   #1
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Raise Battery Voltage For The Inverter?

Is it possible to raise a battery's voltage for a 700 watt inverter?

I have a battery that puts out a lot of power, but its max voltage is 10.6 volts, which isn't enough voltage to keep my inverter from cutting off while using the corded drill (about 400 watts).

The corded drill/inverter combo worked great with my normal 12 volt battery, but the inverter automatically cuts off at 10.something volts.

So, V=IR, so if I wire a .8 ohm, 600 watt resistor in series with the battery, is there any way that could increase the voltage? I know it sounds stupid & doesn't even make sense to me, but, is it possible at all?

Step-up & step down voltage regulator units are things I've looked at, but they're rarely over 300 watts.

I've also considered wiring 2 of these low-voltage batteries in series and adding a 1.65 ohm resistor (600 watt rated) to get around 12 volts for the inverter. That sounds more plausible to me. But really, I'd have to buy 6 separate 100 watt, 1.8 ohm resistors and wire them in parallel before hooking them in series with the 2 deep-cycle batteries that would be in series.

This makes sense, right?
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Old 21-11-2014, 21:02   #2
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Re: raise battery voltage for the inverter?

Quote:
Originally Posted by liveaboardL View Post

So, V=IR, so if I wire a .8 ohm, 600 watt resistor in series with the battery, is there any way that could increase the voltage?

This makes sense, right?
Nope. Changing R will not increase V, instead it will reduce I. You need a more complicated, and less efficient, circuit to increase I. But, they are available for purchase.

Fundamentally, your problem is that your voltage makes no sense, especially if they are lead-acid cells. Under 10.8 is effectively discharged.
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Old 21-11-2014, 21:04   #3
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Re: Raise Battery Voltage For The Inverter?

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Originally Posted by liveaboardL View Post

...its max voltage is 10.6 volts, which isn't enough voltage


This makes sense, right?
Perhaps it would be helpful to explain how you ended up with a battery or bank that only does 10.6 volts.

Then we may be able to help.
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Old 21-11-2014, 21:06   #4
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Re: raise battery voltage for the inverter?

What kind of battery gives 10.6 volts?

You can't do what you're trying to do with resistors. You need a regulator like a Zener diode.

The problem with the resistors is that the voltage drop across them is dependent on the current. So unplug the load on your inverter, no current, no drop across the resistors, and suddenly the inverter is seeing 21.2V. Bang.

None of the other equipment on the boat will be happy on 10.6V, which begs the question why you have it.
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Old 21-11-2014, 21:06   #5
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Re: raise battery voltage for the inverter?

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Originally Posted by MYTraveler View Post
Nope. Changing R will not increase V, instead it will reduce I. You need a more complicated, and less efficient, circuit to increase I. But, they are available for purchase.

Fundamentally, your problem is that your voltage makes no sense, especially if they are lead-acid cells. Under 10.8 is effectively discharged.
Sorry. I've left out the whole picture. Lets assume either one of the cells is damaged or there's a different than normal electrolyte, but the batterys have plenty of power at 10.6 volts.
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Old 21-11-2014, 21:11   #6
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Re: Raise Battery Voltage For The Inverter?

Then the only practical solution is to replace the battery with a healthy one.

It's not possible to have a battery with one bad cell and plenty of power, as current will be discharged into the faulty cell. It might explode. Seen it happen.

Can I strongly suggest reading one of the excellent books on marine electrics, and leave your questions until afterwards, in the hope that they have gone away by then.
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Old 21-11-2014, 21:15   #7
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Re: Raise Battery Voltage For The Inverter?

Different than normal electrolyte? What were you thinking of putting in?

"I know it sounds stupid & doesn't even make sense to me". Sounds like there's one thing we agree on.
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Old 21-11-2014, 22:14   #8
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Re: Raise Battery Voltage For The Inverter?

The proper method is to get a DC-DC converter, probably a step-down
from the 20 volts of two in series.

You could buy a 3.2 volt Lithium battery to add in series to boost the voltage, but me thinks spending any money isn't an option here.

Maybe you can take apart the 10.8 volt battery and bypass a cell to reduce it to a "6 volt" one, so two in series would give you 12 volts.
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Old 22-11-2014, 00:39   #9
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Re: Raise Battery Voltage For The Inverter?

Quote:
Originally Posted by liveaboardL View Post
Is it possible to raise a battery's voltage for a 700 watt inverter?

I have a battery that puts out a lot of power, but its max voltage is 10.6 volts, which isn't enough voltage to keep my inverter from cutting off while using the corded drill (about 400 watts).

The corded drill/inverter combo worked great with my normal 12 volt battery, but the inverter automatically cuts off at 10.something volts.

So, V=IR, so if I wire a .8 ohm, 600 watt resistor in series with the battery, is there any way that could increase the voltage? I know it sounds stupid & doesn't even make sense to me, but, is it possible at all?

Step-up & step down voltage regulator units are things I've looked at, but they're rarely over 300 watts.

I've also considered wiring 2 of these low-voltage batteries in series and adding a 1.65 ohm resistor (600 watt rated) to get around 12 volts for the inverter. That sounds more plausible to me. But really, I'd have to buy 6 separate 100 watt, 1.8 ohm resistors and wire them in parallel before hooking them in series with the 2 deep-cycle batteries that would be in series.

This makes sense, right?
NO!

Your bad deep cycle LA battery (originally ~12.6V+ fully charged) has one defective cell, likely benignly shorted, (a 12Vnominal battery has 6 LA cells of ~2.1V+ each in series = ~12.6-13.0V full/at rest; ( 12.6 - 2.1 = ~10.5/6 ) .
Battery repairs are not normally done now (internal ones, anymore; once upon a time 'open' LA cells were used for some apps, with no top (exposed liquid electrolyte pools), the acid could be drained and plate repairs done in a pinch).
You could try a good charging cycle, ideally an "equalization cycle" if you have (or can get) a smartcharger with that feature and it allows it.
Possibly shaking or jarring the batt might shake the internal short loose, for a while; or not. Or it might really short out and do something exciting.

The 5 remaining good cells can continue to supply a usable current indefinitely at ~10.6V (until they too fail); but as you found out, most equipment aboard isn't going to work very well on just 10.6V, period, end of discussion (if you have anything designed for a 9V supply however...).

Trying to rig 'something' up with other batteries, resistors and whatnot may get your boat burned to the waterline, and judging from your ID, maybe fry the whole marina.

Also, running things at 10.6V that normally like to have a 12.6V+ supply will cause them to draw/consume more current than is normal/designed for, which will generate more heat and electrical 'wear' in them (and the feed wiring). None of which is healthy for anything.

You need a replacement battery (or two?). No way around it, hardly.

[edit] Sterling, and others, make batt-to-batt chargers (Pro-C? model?). I think one might accept a solid current source 10.6V as an input, and then output the needed (stepped up) 12.6V+. But the cost of one is more than a new battery.
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Old 22-11-2014, 01:31   #10
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Re: Raise Battery Voltage For The Inverter?

Is this an Alum battery, and if so does it have bad cell or that is what the new voltage is?
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Old 22-11-2014, 05:15   #11
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Re: Raise Battery Voltage For The Inverter?

"Let's ban together to ban sillycone"

The correct term is "band together", not ban.
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Old 22-11-2014, 06:57   #12
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Re: Raise Battery Voltage For The Inverter?

You are correct sir, but that would have a little less humor. I might have even misspelled sillycone.
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Old 22-11-2014, 07:04   #13
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Re: Raise Battery Voltage For The Inverter?

Building resistors in parallel also decreases the total resistance

http://www.sengpielaudio.com/calculator-paralresist.htm


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Old 22-11-2014, 07:12   #14
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Re: Raise Battery Voltage For The Inverter?

Quote:
Originally Posted by liveaboardL View Post
Is it possible to raise a battery's voltage for a 700 watt inverter?

I have a battery that puts out a lot of power, but its max voltage is 10.6 volts, which isn't enough voltage to keep my inverter from cutting off while using the corded drill (about 400 watts).

The corded drill/inverter combo worked great with my normal 12 volt battery, but the inverter automatically cuts off at 10.something volts.

So, V=IR, so if I wire a .8 ohm, 600 watt resistor in series with the battery, is there any way that could increase the voltage? I know it sounds stupid & doesn't even make sense to me, but, is it possible at all?

Step-up & step down voltage regulator units are things I've looked at, but they're rarely over 300 watts.

I've also considered wiring 2 of these low-voltage batteries in series and adding a 1.65 ohm resistor (600 watt rated) to get around 12 volts for the inverter. That sounds more plausible to me. But really, I'd have to buy 6 separate 100 watt, 1.8 ohm resistors and wire them in parallel before hooking them in series with the 2 deep-cycle batteries that would be in series.

This makes sense, right?
I am asking an honest question here. Is this a legit question?

If you have a 12V nominal battery at that voltage you have a bad or shorted cell. The battery is now borderline dangerous..
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Old 22-11-2014, 10:07   #15
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Re: Raise Battery Voltage For The Inverter?

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Originally Posted by liveaboardL View Post
...I have a battery that puts out a lot of power, but its max voltage is 10.6 volts...
I know it sounds stupid & doesn't even make sense...
You betcha!

Your battery is shot. Replace it.
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