On 02/14/2011 05:58 PM, Percival P. Cassidy wrote:
On 02/13/11 03:36 pm, philo wrote:

I'm looking for charger/maintainer -- either an off-the-shelf unit
or a
schematic so I can build my own -- suitable for a flooded deep-cycle
battery, either a pair of 6V "golf cart" batteries in series or a
Group
31.

snip

You do not need anything too fancy...
to "float" the batteries all you need to do is keep them at approx 2.25
volts / cell...so it's possible that your 13.8 v charger will do the
job...

You can test it by checking the total voltage after a 24 hour period...

ideally, a 12v battery should float at about 13.5 volts.

If the float voltage is a little higher or lower it won't be too
critical...but make sure it's well below the 14.2 v gassing point.

I've been in the lead-acid battery business for 36 years...
so have quite a bit of long term empirical data

The West Mountain Radio people told me that their "Super PwrGate"'s
13.5V float setting voltage (not adjustable) might be too high for a
flooded deep-cycle battery. Their user manual refers users to

www.windsun.com/batteries/battery_FAQ.htm

which recommends per-cell float voltages flooded deep-cycle batteries
that translate to 13.02V to 13.20V for a 6-cell battery.

"Perce"



That link did not work...but really, the exact float voltage is not that
critical...the free gassing point of a lead acid battery is 2.37 volts
/cell or 14.2 v for a 6 cell battery...

to float the battery you must stay reasonably below the gassing point or
there will be considerable water consumption...hydrogen and oxygen
production and heating.


OTOH: the nominal open circuit voltage of a fully charged lead acid
battery is 2.12 volts / cell or 12.7v for a 6 cell battery....

so anywhere from 13.1 - 13.8 volts would work for "floating".

Back in the old days when I started in the industry,
the settings on the chargers could drift a bit...so we'd try to keep
everything in the middle of the accepted range or about 13.5 volts


If the battery is going to be on float for an extended period of time...
though the water consumption is minimal...it still needs to be checked
periodically and topped off as needed (never fill a battery up into the
"neck" area...the water level should be a bit below it)

Finally...a few times a year the battery should be equalize charged to
avoid the possibility of sulfation. Usually 6 hours will suffice.
The battery should be brought up to 14.2 volts and allowed to rise to
approx 15 volts depending on the type of charger

On 02/14/11 08:29 pm, philo wrote:

I'm looking for charger/maintainer -- either an off-the-shelf unit
or a
schematic so I can build my own -- suitable for a flooded deep-cycle
battery, either a pair of 6V "golf cart" batteries in series or a
Group
31.

snip

You do not need anything too fancy...
to "float" the batteries all you need to do is keep them at approx 2.25
volts / cell...so it's possible that your 13.8 v charger will do the
job...

You can test it by checking the total voltage after a 24 hour period...

ideally, a 12v battery should float at about 13.5 volts.

If the float voltage is a little higher or lower it won't be too
critical...but make sure it's well below the 14.2 v gassing point.

I've been in the lead-acid battery business for 36 years...
so have quite a bit of long term empirical data

The West Mountain Radio people told me that their "Super PwrGate"'s
13.5V float setting voltage (not adjustable) might be too high for a
flooded deep-cycle battery. Their user manual refers users to

www.windsun.com/batteries/battery_FAQ.htm

which recommends per-cell float voltages flooded deep-cycle batteries
that translate to 13.02V to 13.20V for a 6-cell battery.

That link did not work...but really, the exact float voltage is not that
critical...the free gassing point of a lead acid battery is 2.37 volts
/cell or 14.2 v for a 6 cell battery...

The link worked for me just now -- at least when I added the http://
ahead of it.

to float the battery you must stay reasonably below the gassing point or
there will be considerable water consumption...hydrogen and oxygen
production and heating.


OTOH: the nominal open circuit voltage of a fully charged lead acid
battery is 2.12 volts / cell or 12.7v for a 6 cell battery....

so anywhere from 13.1 - 13.8 volts would work for "floating".

Back in the old days when I started in the industry,
the settings on the chargers could drift a bit...so we'd try to keep
everything in the middle of the accepted range or about 13.5 volts


If the battery is going to be on float for an extended period of time...
though the water consumption is minimal...it still needs to be checked
periodically and topped off as needed (never fill a battery up into the
"neck" area...the water level should be a bit below it)

Finally...a few times a year the battery should be equalize charged to
avoid the possibility of sulfation. Usually 6 hours will suffice.
The battery should be brought up to 14.2 volts and allowed to rise to
approx 15 volts depending on the type of charger

The "Super PwrGate" claims to take care of all phases except equalizing
-- but only for Gel-Cell and AGM batteries. "No Spam" says that the
Iota/IQ system even does regular (weekly!) equalization charges.

I was hoping to find or build something cheaper that could serve as a
controller to make use of one of the power supplies I own already as the
power source.

"Perce"

On 02/14/2011 10:08 PM, Percival P. Cassidy wrote:
On 02/14/11 08:29 pm, philo wrote:

I'm looking for charger/maintainer -- either an off-the-shelf unit
or a
schematic so I can build my own -- suitable for a flooded deep-cycle
battery, either a pair of 6V "golf cart" batteries in series or a
Group
31.

snip

The link worked for me just now -- at least when I added the http://
ahead of it.

to float the battery you must stay reasonably below the gassing point or
there will be considerable water consumption...hydrogen and oxygen
production and heating.


OTOH: the nominal open circuit voltage of a fully charged lead acid
battery is 2.12 volts / cell or 12.7v for a 6 cell battery....

so anywhere from 13.1 - 13.8 volts would work for "floating".

Back in the old days when I started in the industry,
the settings on the chargers could drift a bit...so we'd try to keep
everything in the middle of the accepted range or about 13.5 volts


If the battery is going to be on float for an extended period of time...
though the water consumption is minimal...it still needs to be checked
periodically and topped off as needed (never fill a battery up into the
"neck" area...the water level should be a bit below it)

Finally...a few times a year the battery should be equalize charged to
avoid the possibility of sulfation. Usually 6 hours will suffice.
The battery should be brought up to 14.2 volts and allowed to rise to
approx 15 volts depending on the type of charger

The "Super PwrGate" claims to take care of all phases except equalizing
-- but only for Gel-Cell and AGM batteries. "No Spam" says that the
Iota/IQ system even does regular (weekly!) equalization charges.

I was hoping to find or build something cheaper that could serve as a
controller to make use of one of the power supplies I own already as the
power source.

"Perce"


I'd give one of your power supplies a try and see if it gives you an
acceptable float voltage...

If not, then one of the commercial ones would probably be a lot easier
than trying to build one yourself

If not, then one of the commercial ones would probably be a lot easier
than trying to build one yourself-

Hey ole timer:


First and formost this is a homebrew group.
To suggest to not build and to buy a commercial of the shelf reay to
use product, is like those sex ads that get posted here, they both
have nothing to do with homebrew.

Lastly I built a flooded lead acid charger. I only bought one part the
IC UC3906, I already had a solderless breadboard, the resistors and
capacitors in my junk drawer
The hardest part was figuring the resistor values and how to make
those values, and that was easy.
The heatsink fan came from an old CPU fan heatsink, and I mounted the
pass transistor to that heatsink fan.
I think that the UC3906 was the best think since sliced bread

73 ole timer
de n8zu

On 2/16/2011 10:15 AM, raypsi wrote:

If not, then one of the commercial ones would probably be a lot easier
than trying to build one yourself-

Hey ole timer:


First and formost this is a homebrew group.

So stop cross-posting to rec.radio.amateur.equipment

That's EQUIPMENT. Commercially built as well as home brew.

I ignore hams when it comes to battery equipment and pay attention to
people who trust their lives to their batteries,
http://www.morganscloud.com/2011/02/...-battery-life/

On 02/16/11 11:34 am, Audio1 wrote:

If not, then one of the commercial ones would probably be a lot easier
than trying to build one yourself-

Hey ole timer:


First and formost this is a homebrew group.

So stop cross-posting to rec.radio.amateur.equipment

That's EQUIPMENT. Commercially built as well as home brew.

I guess it's my (the OP) fault: I cross-posted my original question --
asking about off-the-shelf or homebrew solutions -- to both
r.r.a.equipment and r.r.a.homebrew, and all the responses have gone to both.

I ignore hams when it comes to battery equipment and pay attention to
people who trust their lives to their batteries,
http://www.morganscloud.com/2011/02/...-battery-life/

I'll check that out.

"Perce"

On 02/16/11 10:15 am, raypsi wrote:

snip

... I built a flooded lead acid charger. I only bought one part the
IC UC3906, I already had a solderless breadboard, the resistors and
capacitors in my junk drawer
The hardest part was figuring the resistor values and how to make
those values, and that was easy.
The heatsink fan came from an old CPU fan heatsink, and I mounted the
pass transistor to that heatsink fan.
I think that the UC3906 was the best think since sliced bread

I've seen schematics and board layouts for SLA chargers based on the
UC3906. VK3EM's uses SMT components, while N5BIA's uses discrete
components -- but both are only for charging currents of 2A or so.

For what current did you build yours? If high-current, what pass
transistor(s) did you use?

N5BIA offers a kit, and I was wondering whether this could be beefed up
to handle 25A by adding 12ga wire to all the charging-current traces and
substituting higher-current pass transistor(s). I'd have to recalculate
the resistor values to suit a flooded battery, of course. And what about
using a P-channel MOSFET device, such as the STP80PF55 that the "Micro
M+" uses?

"Perce"

On 02/16/2011 12:00 PM, Percival P. Cassidy wrote:
On 02/16/11 11:34 am, Audio1 wrote:
d r.r.a.homebrew, and all the responses have gone to
both.



snip
I ignore hams when it comes to battery equipment and pay attention to
people who trust their lives to their batteries,
http://www.morganscloud.com/2011/02/...-battery-life/


I'll check that out.

"Perce"



You can take my advice or leave it...
that's up to you.

I'm a senior service engineer who's been in the (lead acid) battery
business for 36 years.

I assure you that "float charging" a battery is not rocket science
and you do not have to get too fancy

(but if you want to, that's fine )

On 02/16/11 03:22 pm, philo wrote:

I ignore hams when it comes to battery equipment and pay attention to
people who trust their lives to their batteries,
http://www.morganscloud.com/2011/02/...-battery-life/

I'll check that out.

You can take my advice or leave it...
that's up to you.

I'm a senior service engineer who's been in the (lead acid) battery
business for 36 years.

I assure you that "float charging" a battery is not rocket science
and you do not have to get too fancy

(but if you want to, that's fine )

I know that I can connect a *suitable* P/S set to an appropriate voltage
to "float" my batteries *if that is all I want to do* (my little Astron
"switcher" is doing it right now), but I was hoping to get or build
something that will handle the initial phases of charging a
significantly discharged battery then switch automatically to "float" mode.

"Perce"

In article ,
Percival P. Cassidy wrote:

N5BIA offers a kit, and I was wondering whether this could be beefed up
to handle 25A by adding 12ga wire to all the charging-current traces and
substituting higher-current pass transistor(s).

.... and huge heatsinks.

I'd have to recalculate
the resistor values to suit a flooded battery, of course. And what about
using a P-channel MOSFET device, such as the STP80PF55 that the "Micro
M+" uses?

The thing about a low-Rds-on MOSFET, or a low-Vce-sat PNP, is that it
really only gains you a benefit under one circumstance: when it's
"hard on", acting as much as possible like a short-circuit. This will
happen only during the "bulk" fast-charge stage... and only if the
charge controller "sees" that the raw (unregulated) power supply
circuit isn't capable of pushing more amps into the battery than the
design allows.

If the charge control circuit finds it necessary to reduce _either_
the charge amperage, or the voltage being delivered to the battery, in
order to charge the battery safely, then the pass transistor will be
"partially off". There will be a significant voltage across it
(roughly speaking, Vsupply - Vbattery) and lots of amperage, and so it
will be dissipating a lot of energy as heat.

At that point, the actual Rds-on of a MOSFET, or the Vce-sat of a PNP,
will matter not at all. You'll have to dissipate (Vsupply-Vbat)*Icharge
watts of heat in the transistor.

Now, if you happen to have been careful (or lucky) enough in the
design of your "raw" power supply, things will look good. By "careful
or lucky", I mean that you've put together a raw supply which just
happens to run out of "oomph" at exactly the right moment... the
effort of delivering 25A into the battery just happens to cause the
supply to sag down to the right voltage (equal to a voltage in the
range you want to be charging at). Under those conditions, the
whole system will be running "flat out", the pass transistor will be
turned on as hard as it can be, and heat dissipation in the transistor
will be minimized by using a low-voltage-drop transistor of some sort.

However, this approach has pitfalls... it will be finicky to get right
(component selection will be difficult) and it will probably be very
sensitive to variations in the AC power-line voltage. In real life,
you'd find that much of the time, either you aren't getting the full
25A of charge current (line voltage too low), or the voltage and/or
current are potentially too high and the charger is having to back off
turn down the pass transistor (at which point there's no longer an
advantage to a low-voltage-drop transistor).

If you want to deliver a high charging current, with good control and
low losses, under a fairly wide range of conditions, I think you'd
probably want to use a different approach... use a buck-mode switching
regulator rather than a linear pass-transistor system. With that
approach, the pass element would almost always be fully-on or
fully-off, and thus there'd be a real benefit to a low-resistance
MOSFET or a low-saturation power bipolar part.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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