battery bank charging

Started by hnash53, January 17, 2007, 07:15:25 PM

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MountainDon

#50
Basically Yes, you should see higher volts, especially when run at higher speeds. However, if you have a basically stock alternator, that is with magnetic coils instead of permanent magnets it won't make power unless the magnetic coils are powered. The little I do know about std auto alternators is that they use power from the battery to energize the magnetic field. Once it reached a certain rotational speed it then becomes self powered. A good auto elec tech would know.

If you had a battery that was discharged quite a bit you would see a higher voltage until the battery charge built up.

And I don't know if you will damage anything if you diconnect the battery while running. In a car that would be a disaster for a variety of electronic components.

The amp-hr rating is a way of stating how much energy you have stored. The 134 amp-hr is the amount of work stored. However one thing to remember is that if the battery is rated at 134 and you suck all that power out before recharging the batteries will fail in a short time. For best life using only about 25% of the batteries capacity is best, with std. wet cell batteries.  (going to 50% is okay if not done all the time) The AGM will stand up to a deeper discharge rate than wet cells. Your battery manufacturer's info should detail the proper care and feeding of the ones you have.
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The 20 hour rate means that if you draw all the power out evenly over 20 hours you will get 134 amp-hours. However, if you draw all the power out over 10 hours the capacity will be less. Conversely if drawn down over a longer period, say 100 hours you will get more capacity out. Think of it like a gas gauge on your car that tells you how many miles you can go, instead of how many gallons you have. The gas gauge says you can go 400 miles at 60 MPH. But if you go 80 MPH you will not go as far; if you go 40 MPH you will go farther

glenn-k

#51
Unless that is a internal regulator alternator, you need power to your field.  It won't put out without power to the field but you don't want to leave it energized all the time or it will pull the battery down.  With no regulator and high RPM it may charge but will soon overcharge the battery and burn it up I think - or burn out the alternator.  They are made to charge a fully charged good battery and keep it up but my old electrical repairman was always on my case to get the battery charged before hooking a new alternator to it.  I never did blow one because of not heeding his warnings but you never know -- he was one of the best.

At the very least if you hook a wire to the field, I would have a volt meter on it.  If it gets much over 14 I would get a regulator on it for a 12 volt system.  I'm the guy who charges batteries with  a welder - I've burned up /blown up lots of them over the years.  :-/



hnash53

OK.  Here's what I ended up with.  I ditched the unregulated Chrysler alternator, and went with a one-wire Delco-Remy alternator (it has a built-in regulator).  No fields to eff with.  Just pos and neg.  The 12 v battery charger works great.

NOW, the label on my AGM sealed batteries says they have a FLOAT CHARGE VALUE OF 13.5-13.8.  What does that mean?

It's my understanding (and my volt meter tells me the same thing) that my alternator is putting out about 16volts.  As long as the batteries can absorb the charge, everything's cool.  But when they get full, how can I know that they are full?

I plan to use a dump regulator to dump the excess charging, such as in summer when the panels are always charging, and dump the excess into a 12V water heater element.

Thanks.

JRR

#54
I believe "float charge" is the highest, perhaps optimum, voltage limit that a battery can be charged to before being "overcharged".   Or in other words, it may OK to charge such a battery with a 14 or even a 15, or higher, volt source ... if, after removing the charger, the voltage quickly settles to 13.5 volts.  Of course, temp and current limits have to be also observed.

A lot of science has been recently been done in determining the best current waveform for charging a battery.  "Pulse charging", instead of pure DC, has some promises for lead-acid batteries.   A number of patents have been filed.

Time will tell.


glenn-k

After bulk charging an inverter switches to float charge just peaking up the batteries and keeping them there.  A solar guy here told me you want to float charge quite a bit to keep the batteries optimum.  Mine don't see much of it.

QuoteA multi-stage charger first applies a constant current charge, raising the cell voltage to a preset voltage (Stage 1 in Figure 1). Stage 1 takes about 5 hours and the battery is charged to 70%. During the topping charge in Stage 2 that follows, the charge current is gradually reduced as the cell is being saturated. The topping charge takes another 5 hours and is essential for the well being of the battery. If omitted, the battery would eventually lose the ability to accept a full charge. Full charge is attained after the voltage has reached the threshold and the current has dropped to 3% of the rated current or has leveled off. The final Stage 3 is the float charge, which compensates for the self-discharge.

http://www.batteryuniversity.com/partone-13.htm  

I need to read more of the above. :-/

glenn-k

QuoteOK.  Here's what I ended up with.  I ditched the unregulated Chrysler alternator, and went with a one-wire Delco-Remy alternator (it has a built-in regulator).  No fields to eff with.  Just pos and neg.  The 12 v battery charger works great.

NOW, the label on my AGM sealed batteries says they have a FLOAT CHARGE VALUE OF 13.5-13.8.  What does that mean?

It's my understanding (and my volt meter tells me the same thing) that my alternator is putting out about 16volts.  As long as the batteries can absorb the charge, everything's cool.  But when they get full, how can I know that they are full?

I plan to use a dump regulator to dump the excess charging, such as in summer when the panels are always charging, and dump the excess into a 12V water heater element.

Thanks.

That Delco is highly recommended in the alternate energy world.  Good deal. :)

The dump  load is great for wind generators as you don't want to unload them - some regulators such as the Trace will just disconnect from the panels and let them go high which is OK also.  The MPPT regulators such as the Outback will put out more power to the batteries from the panels, and also allow higher input voltage allowing a decrease in wire size while still putting out 24v to the batteries.

MountainDon

#57
Whoops! I didn't see Glenn's responses coming in!   :)

Quote
NOW, the label on my AGM sealed batteries says they have a FLOAT CHARGE VALUE OF 13.5-13.8.  What does that mean?
The following quote is directed at wet lead-acid batteries. AGM type batteries have slightly different recommendations and may differ between manufacturers. Obtain and use the manufacturers directions. In general AGM batteries can handle higher charging current rates and higher voltages as well. But go by whatever the manufacturer states.

"The first step is bulk charging where up to 80% of the battery energy capacity is replaced by the charger at the maximum voltage and current amp rating of the charger. When the battery voltage reaches 14.4 volts this begins the absorption charge step. This is where the voltage is held at a constant 14.4 volts and the current (amps) declines until the battery is 98% charged. [highlight]Next comes the Float Step. This is a regulated voltage of not more than 13.4 volts and usually less than 1 amp of current. [/highlight]This in time will bring the battery to 100% charged or close to it. The float charge will not boil or heat batteries but will maintain the batteries at 100% readiness and prevent cycling during long term inactivity. [highlight]Some gel cell and AGM batteries may require special settings or chargers.[/highlight]"

QuoteBut when they get full, how can I know that they are full?
The best way is to buy and use a good float hydrometer; not the ones with the balls, but one with a numerically calibrated float. If we're talking about using the home made battery charger gen with the Delco Alternator, the output is regulated. It will should not overcharge.

MountainDon

#58
Quote
I plan to use a dump regulator to dump the excess charging, such as in summer when the panels are always charging, and dump the excess into a 12V water heater element.
Thanks.

I don't understand? Power from solar panels is usually routed through a charge controller specifically designed for PV systems. Unlike a windmill they can have the charge power throttled down electronically. They are phenomenally reliable. Depending on the # of 12 volt panels you have you can even get PV controllers that will handle 48 volts and higher and that can cut down on the size of cabling even more. The higher voltages such as 48 VDC are then notched down to match the battery pack voltage.

That's the route my remote system will take.... 48 volt, or maybe 60 depending on some variables not yet settled upon, from the panels to the controller (Outback MX60A) which will be at the battery location. Distance from PV panels to controller/batteries will be approx. 150 feet.


glenn-k

Solar panels can get throttled as you say or really gradually disconnected by their regulator.  Wind generators can't be disconnected - they must have some kind of a dump load to burn off the excess power - I pump water by having a set of relays hooked to my dump load of the wind generator along with the excess being throttled.

A wind generator goes wild and may fly apart if not loaded hence the dump load or other way to get rid of the excess generated power.

MountainDon

#60
I really wish I had enough reliable wind to make use of a wind charger. But then too, the location is so heavily forested I would need a rather tall tower to get the windmill high enough above the tree tops.  :(


glenn-k

About 30 feet minimum to avoid the turbulence but a 100 foot tower will get about three times the wind of a 30 foot tower.

MountainDon

#62
That's pretty much what I thought. Maybe someday.    :-/  I'd need at least a 100' tower. Of course then I could put a ham radio antenna up there as well.... Hmmm.

youngins

Here you go, Glenn:



Our local Super Wal-Mart is one of two concept stores (the other is in Denver) which testing the use of energy conservation teniques.  They have two other smaller windmills which I think pump irrigation water.


glenn-k

That's a start.  Now if only it was against the law for people to not like them or think they don't look nice.  I think we need some legislation. ::)

hnash53

Hey, guys, AGM batteries are SEALED.  There's no way one can test these with a hydrometer.

AS frequently occurs, I'm getting a variety of answers.  And as usual, I'll just have to rely on what I discover for myself.

Thanks for all the help.

MountainDon

OOOPs! I'm sorry about that; my error. The only way to tell state of charge with the AGM would be to measure the voltage. That should be done two or three hours after the last charge or discharge so the cells can normalize themselves. That is, they may show higher than they really are after receiving a charge, or lower then they really are after a discharge. Probably not too much of a difference if the load or charge current has not been too high.

Once again, sorry 'bout that.

glenn-k

Seems a battery tester - load checker with a heater or carbon pile should show you a bit about how they take a load.  A bad battery will drop off within a few seconds usually.