Adjustable voltage booster?

"John Fields" wrote >

On the contrary. That is exactly the reason I can't afford it.

Sorry, I had thought that this might be a rather simple question so I asked here. Perhaps I should have asked in s.e.design where everyone was most helpful last year in the development of my remote lighting and watermaker controls.

--
Glenn Ashmore

I\'m building a 45\' cutter in strip/composite. Watch my progress (or lack 
there of) at:  http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

--
You bet! 

If you can afford to be building a boat you can surely afford my
design services.  Email me if you\'re interested. :-)

I think the easiest method might be to add one or more diodes in series with the output and connect the sense line directly to the alternator output. The battery isolators used with dual battery setups might be suitable. If the regulator circuitry is accessible modifying it would be very easy. There are also electronic circuits that will also do this job but would take a little design work.

Don Young

since this unit has a sense line, is there not also a calibration pot somewhere on it that you can adjust down to suit your needs? To boost by 1 volt means you'll need to build a power supply that switched the DC across an inductor to boost up the voltage, then rectify it again and add it to your original 13.2 volts. seems to me that a circuit that would use a couple hi current diodes in series with the alternators output would work for the motoring, and then use a high current relay to enguage and bypass the diodes when the load increases to a certain threshold point of your choosing.

good luck

Specs on the Echo-Tech alternator

Since the alternator has a 14.4V set point a battery will not "fry" when fully charged because the battery voltage and the alternator voltage will be equal at the set point, hence zero charging current will be the case when the battery is fully charged.

The whole idea of having this alternator in emergency vehicles is to ensure that the battery is not discharged by heavy loading at low rpm such as when idling with pumps, radio etc going flat chat. The alternator supplies the bulk of the load at such times with the battery supplying instantaneous short duration peaks. However, when the vehicle is cruising and the battery loading is light the alternator simply maintains the battery voltage at 14.4V without pushing undue charging current into it. I'm sure that the battery on emergency vehicles would also be "fried" if your assumption was correct, and that really would set a new standard for the word "emergency". They would be on the radio requesting a new battery during an emergency if this was the case.

I doubt that you would have any worries with the alternator as is.

PS: Sorry, they would be on the mobile phone cos the radio wouldn't work due to a fried battery :-)

"Ross Herbert" wrote

The problem is wet cell batteries start outgassing at 14.2V. That is not really a problem with an emergency vehicle that only runs for a few hours a day without any accessories working but a cruising sailboat may motor for several days at a time.

It looks like the diode idea might be the answer with a relay to switch them in and switch the sense line from the battery to the alternator output.

--
Glenn Ashmore

I\'m building a 45\' cutter in strip/composite. Watch my progress (or lack 
there of) at:  http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

I assume that you read the literature on the Eco-Tech website eg,

Note that at the bottom of page 1 it says that the output voltage when fitted to a vehicle is regulated to 14.1V.

On page 2 under Equipment Savings it refers to the non-requirement for load shedding devices. This would seem to indicate that overcharging a battery will not happen.

If you have any concerns then it might be a good idea to explain your situation to Eco-tech via

and see what they have to say. If you don't need to do anything then you might be worrying without good cause.

Look for an RV show, or RV dealer near you, and ask for an "isolation diode". In vehicles with a separate engine battery and "utility" battery (like a fire truck - in RVs, they call it the "house" battery), they boost the alternator output voltage by the Vf of a diode, so that the alternator can charge both batteries but their outputs are isolated.

Depending on what kind of amps you're going for, you could be looking at some pretty hefty diodes, e.g.:

?Ref=398254&Row=43989&Site=US

If you're only charging one battery, you only need one diode, or you could try fiddling with the regulator, if you're brave and know what you're doing.

Good Luck! Rich

Don't worry. This is the basics group - no question is unwelcome here.[1]

We try to keep the signal-to-noise ratio up, to give newbies someplace where they'll feel welcome no matter how new they are.

Occasionally, one of the regulars forgets which group he's addressing - please ignore them. :-)

Have Fun! Rich [1] well, as long as it's got electronics in it somewhere. ;-)

Switching the diode(s) and sense line should not be necessary. The alternator can still provide full current output when the battery is below the regulator control point.

Don Young

an LM555 powered from the battery (via the ignition switch) that drives a capacitor-diode pump (cockroft-walton multiplier) to produce a higher voltage (about 26V), this higer voltage is the regulated using a LM317 with the ref pin connected to a voltage divider (across the battery supply) that puts it 0.2V below a your ideal voltage. the altenators sense line gets connected to the 317 output which will be about 1V above battery voltage.

if it breaks your battery will probably get baked, so check the data sheets etc for how to use them, and make it solid and waterproof.

Bye. Jasen

"jasen" wrote

Thanks, I will do some research on that idea.

I am getting conflicting information from the battery makers. All the books and Surrette, the super high quality deep cycle maker, insists that wet cell batteries should not be held above 13.2V for more than 4 hours after reaching 85% charged. The Trojan, #2 in deep cycle wet cells, engineers say 14.1 is OK as long as the amperage does not exceed 10 to 15A. If that is true the stock regulator should be OK.

Time to delve into the physics of battery charging .

--
Glenn Ashmore

I\'m building a 45\' cutter in strip/composite. Watch my progress (or lack 
there of) at:  http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn, I just re-read your original postto check on the type of battery you were charging and noted there were 4 x L16 - which appear to be aimed at renewable energy (solar) applications. You are planning to use them in a marine environment.

Rolls/Surrette recommendation concerning the use of their solar batteries in mobile and marine situations appears at the top of this webpage

Other than that, info gleaned from the Trojan website seems to indicate that their batteries should be charged on a daily basis at

14.8V (as would be the case for a vehicle), 13.2V float charging, and 15.5V equalizing (not really applicable for your case).

Since the Eco-Tech alternator is a constant voltage regulated charger set at 14.4V, - and based on the manf's document I referred to earlier saying that a vehicle battery would read 14.1V fully charged, I can't see why your batteries would be fried. If it were me, I would simply try it by taking the boat out for a day and checking to see if excessive gassing occurred. One trip would not cause any damage, and if they did gas, then you could add your diode dropper or whatever. Why do it if it isn't necessary?