[RE-wrenches] Ladders for Inspectors

[Jason Szumlanski]

Is anyone being forced to leave ladders up and secured in place for
inspectors? One jurisdiction in our neck of the woods is insisting that
we do this. I believe this is a serious risk to public safety, and I
won't be responsible for some homeowner or curious child getting injured
on or around a ladder propped against a building. The jurisdiction does
not do timed inspections, so we can't even be there to raise the ladder
for them.

 

Can anyone point to some resources (OSHA?) that I can use to convince
the building official that this is a very bad idea?

 

Jason Szumlanski

Fafco Solar

 

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Re: [RE-wrenches] Ladders for Inspectors

[Dave Click]

A letter from your insurance company may do the trick here. They 
probably wouldn't be too happy about the homeowner, curious child, OR 
inspector using your ladder even if you are on site watching it.


On 2011/9/1 7:45, Jason Szumlanski wrote:

Is anyone being forced to leave ladders up and secured in place for
inspectors? One jurisdiction in our neck of the woods is insisting that
we do this. I believe this is a serious risk to public safety, and I
won’t be responsible for some homeowner or curious child getting injured
on or around a ladder propped against a building. The jurisdiction does
not do timed inspections, so we can’t even be there to raise the ladder
for them.

Can anyone point to some resources (OSHA?) that I can use to convince
the building official that this is a very bad idea?

Jason Szumlanski

Fafco Solar



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Re: [RE-wrenches] Ladders for Inspectors

[Benn At DayStarSolar]

This issue came up for me as well.
 I dont recall at the moment where it is written, perhaps it was OSHA,  but 
apparently the contractor (permit puller) is responsible for supplying access 
and safety equip ie, fall protection (with exception of personal PPE, boots, 
hat, glasses) for inspectors to inspect the permitted work. 

You do bring up a valid issue re leaving a ladder up for them, especially 
considering they typically leave a pretty big window open for when they will 
drop by. I believe that this puts the onus on the inspector to provide an 
accurate inspection time. 

I'm impressed that your inspector even wants to get up on a ladder!!!

benn
Sent from a 'smart' phone, with tiny keys. Please excuse shortcuts and typos. 

On 2011-09-01, at 8:46 AM, "Jason Szumlanski"  wrote:

> Is anyone being forced to leave ladders up and secured in place for 
> inspectors? One jurisdiction in our neck of the woods is insisting that we do 
> this. I believe this is a serious risk to public safety, and I won’t be 
> responsible for some homeowner or curious child getting injured on or around 
> a ladder propped against a building. The jurisdiction does not do timed 
> inspections, so we can’t even be there to raise the ladder for them.
> 
>  
> 
> Can anyone point to some resources (OSHA?) that I can use to convince the 
> building official that this is a very bad idea?
> 
>  
> 
> Jason Szumlanski
> 
> Fafco Solar
> 
>  
> 
> ___
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> 
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Re: [RE-wrenches] Ladders for Inspectors

[Jason Szumlanski]

Ha – The roof we are dealing with today has 26’ high eaves and it is a steep 
metal roof. There is no way they are actually getting up there. When we do 
timed inspections in other jurisdictions they rarely step foot on a ladder. 
Maybe it’s a testament to our reputation, but we are paying for the inspection 
- it would be nice if it were actually done.

 

Jason Szumlanski

Fafco Solar 

 

 

From: re-wrenches-boun...@lists.re-wrenches.org 
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Benn At 
DayStarSolar
Sent: Thursday, September 01, 2011 1:55 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Ladders for Inspectors

 

This issue came up for me as well.

 I dont recall at the moment where it is written, perhaps it was OSHA,  but 
apparently the contractor (permit puller) is responsible for supplying access 
and safety equip ie, fall protection (with exception of personal PPE, boots, 
hat, glasses) for inspectors to inspect the permitted work. 

 

You do bring up a valid issue re leaving a ladder up for them, especially 
considering they typically leave a pretty big window open for when they will 
drop by. I believe that this puts the onus on the inspector to provide an 
accurate inspection time. 

 

I'm impressed that your inspector even wants to get up on a ladder!!!

 

benn

Sent from a 'smart' phone, with tiny keys. Please excuse shortcuts and typos. 


On 2011-09-01, at 8:46 AM, "Jason Szumlanski"  wrote:

Is anyone being forced to leave ladders up and secured in place for 
inspectors? One jurisdiction in our neck of the woods is insisting that we do 
this. I believe this is a serious risk to public safety, and I won’t be 
responsible for some homeowner or curious child getting injured on or around a 
ladder propped against a building. The jurisdiction does not do timed 
inspections, so we can’t even be there to raise the ladder for them.

 

Can anyone point to some resources (OSHA?) that I can use to convince 
the building official that this is a very bad idea?

 

Jason Szumlanski

Fafco Solar

 

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[RE-wrenches] Western Massachusetts installer needed

[Larry Crutcher, Starlight Solar Power Systems]

I am looking for someone to install a PV solar and inverter/charger system in 
an RV is Western Massachusetts. It is similar to an off grid system. Please 
contact me off list if you can help.

Larry Crutcher
Starlight Solar Power Systems
11871 S Fortuna Road, #210
Yuma, AZ 85367

la...@starlightsolar.com
(928) 342-9103




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[RE-wrenches] San Francisco electrician referral needed.

[William Miller]

Friends:

Thanks for any referral for a customer.  Please respond off-line.

Thanks,

William


William Miller
Miller Solar
Voice :805-438-5600
email: will...@millersolar.com
http://millersolar.com
License No. C-10-773985
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[RE-wrenches] No referrals on list, please

[Michael Welch]

Hi gang. Just a reminder to **not** use this list to either find customers, 
find installers, or to refer potential customer to others.

If you have any questions about this, please contact me off list.

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[RE-wrenches] unique battery bank design question

[mac Lewis]

Hello wrenches,

I have a battery bank questions.  I have an Oil & Gas client interested in
setting up an off-grid control system that has a various DC loads at 12VDC,
24 VDC and 48 VDC.  My thought is to build a 48 V battery bank and tap off
the bank at various points to create a 12V bus, 24V bus and 48V bus.  I am a
bit concerned about unequal loading of the batteries.  Has anyone dealt with
something like this that would like to share some insight?

Thanks

-- 



Mac Lewis

*

"Yo solo sé que no sé nada." -Sócrates
*
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Re: [RE-wrenches] unique battery bank design question

[Jason Szumlanski]

I always thought that a very small 12V or 24V tap relative to the total 
capacity would be inconsequential. I was recently told otherwise by a battery 
mfr rep, but that is not surprising. I suppose the real question is what 
constitutes inconsequential. A 1A @ 12V fan on a 1000aH @48V battery bank can't 
make any real difference. Correct me if I am wrong! 

 

Jason Szumlanski

Fafco Solar 

 

 

From: re-wrenches-boun...@lists.re-wrenches.org 
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of mac Lewis
Sent: Thursday, September 01, 2011 3:52 PM
To: RE-wrenches@lists.re-wrenches.org
Subject: [RE-wrenches] unique battery bank design question

 

Hello wrenches,

 

I have a battery bank questions.  I have an Oil & Gas client interested in 
setting up an off-grid control system that has a various DC loads at 12VDC, 24 
VDC and 48 VDC.  My thought is to build a 48 V battery bank and tap off the 
bank at various points to create a 12V bus, 24V bus and 48V bus.  I am a bit 
concerned about unequal loading of the batteries.  Has anyone dealt with 
something like this that would like to share some insight?

 

Thanks


 

-- 

 

 

 

Mac Lewis

"Yo solo sé que no sé nada." -Sócrates

 

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Re: [RE-wrenches] unique battery bank design question

[Exeltech]

Mac,

Don't tap the battery.  Bad idea.  Uneven loading = unequal charge/discharge, 
which leads to shortened battery life and other troubles.

Better idea:  If you know the maximum load current, use high-efficiency DC-DC 
supplies of adequate current and other ratings to step 48V down to 12 or 24V.


Dan
Sr. Engineer
Exeltech


--- On Thu, 9/1/11, mac Lewis  wrote:

From: mac Lewis 
Subject: [RE-wrenches] unique battery bank design question
To: RE-wrenches@lists.re-wrenches.org
Date: Thursday, September 1, 2011, 2:52 PM

Hello wrenches,
I have a battery bank questions.  I have an Oil & Gas client interested in 
setting up an off-grid control system that has a various DC loads at 12VDC, 24 
VDC and 48 VDC.  My thought is to build a 48 V battery bank and tap off the 
bank at various points to create a 12V bus, 24V bus and 48V bus.  I am a bit 
concerned about unequal loading of the batteries.  Has anyone dealt with 
something like this that would like to share some insight?

Thanks

-- 


Mac Lewis
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Re: [RE-wrenches] unique battery bank design question

[Allan Sindelar]

  
  
mac,
Don't tap off various voltages. Use DC-DC converters for any voltage
other than nominal. Anything else will lead to uneven charging and
shortened life.
Allan


  
  
  Allan Sindelar
  al...@positiveenergysolar.com
NABCEP Certified Photovoltaic
  Installer
  NABCEP Certified Technical Sales Professional
  New Mexico EE98J Journeyman Electrician
  Positive Energy, Inc.
  3201 Calle Marie
  Santa Fe, New Mexico 87507
  505 424-1112
  www.positiveenergysolar.com
  
  
  
   

On 9/1/2011 1:52 PM, mac Lewis wrote:
Hello wrenches,
  
  
  I have a battery bank questions.  I have an Oil & Gas
client interested in setting up an off-grid control system that
has a various DC loads at 12VDC, 24 VDC and 48 VDC.  My thought
is to build a 48 V battery bank and tap off the bank at various
points to create a 12V bus, 24V bus and 48V bus.  I am a bit
concerned about unequal loading of the batteries.  Has anyone
dealt with something like this that would like to share some
insight?
  
  
  Thanks


-- 



  


Mac Lewis


  
"Yo solo sé que no sé nada." -Sócrates

  
  

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Re: [RE-wrenches] unique battery bank design question

[Dan Fink]

I always thought small multi-voltage taps, for example a 12 volt 
domestic water pressure pump center-tapped from a 24 volt battery bank, 
would be no problem, too, but experience and troubleshooting calls have 
proved otherwise. Even such a low-power intermittent use has caused 
serious problems in systems I've looked at.


Hopefully you don't have any huge DC loads, and can use 48V DC-DC 
converters at a reasonable price.


Dan Fink,
Executive Director
Buckville Energy Consulting
Buckville Publications LLC
NABCEP / IREC accredited Continuing Education Providers
970.672.4342 (voicemail)
970.373.1311 (FAX)


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Re: [RE-wrenches] unique battery bank design question

[Jason Szumlanski]

Dan,

 

What kind of efficiency level (%) can you get out of a DC-DC supply on a
small load, say <5A @ 12V with a 48V->12V converter? Is the efficiency
level highly variable depending on load as a percentage of the
converter's maximum capacity, or is it pretty constant?

 

I run into this once in a while, so this piece of information would help
me make some better decisions.

 

Thanks,

 

Jason Szumlanski

Fafco Solar 

 

 

From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Exeltech
Sent: Thursday, September 01, 2011 3:58 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] unique battery bank design question

 

Mac,

Don't tap the battery.  Bad idea.  Uneven loading = unequal
charge/discharge, which leads to shortened battery life and other
troubles.

Better idea:  If you know the maximum load current, use high-efficiency
DC-DC supplies of adequate current and other ratings to step 48V down to
12 or 24V.


Dan
Sr. Engineer
Exeltech


--- On Thu, 9/1/11, mac Lewis  wrote:


From: mac Lewis 
Subject: [RE-wrenches] unique battery bank design question
To: RE-wrenches@lists.re-wrenches.org
Date: Thursday, September 1, 2011, 2:52 PM

Hello wrenches,

 

I have a battery bank questions.  I have an Oil & Gas client interested
in setting up an off-grid control system that has a various DC loads at
12VDC, 24 VDC and 48 VDC.  My thought is to build a 48 V battery bank
and tap off the bank at various points to create a 12V bus, 24V bus and
48V bus.  I am a bit concerned about unequal loading of the batteries.
Has anyone dealt with something like this that would like to share some
insight?

 

Thanks


 

-- 

 

Mac Lewis

 

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Re: [RE-wrenches] unique battery bank design question

[Hugh]

At 15:57 -0400 1/9/11, Jason Szumlanski wrote:

 A 1A @ 12V fan on a 1000aH @48V battery bank can't make any real 
difference. Correct me if I am wrong!




Yes that is wrong, because after 4 days you have removed 10% of the 
nominal capacity or about 20% of the usable capacity.


Tapping off batteries is bad practice as universally agreed.  One way 
to mitigate it could be to use separate shunt regulators (diversion 
load controllers) for each 12-volt portion.  This would probably be a 
healthy feature for 'balancing' any 48 volt battery and would 
possibly rescue a tapped battery, given enough surplus energy 
availability (which is usually the key thing for battery health).


Just a thought.

The snag is the cost.  ho hum.
--
Hugh Piggott

Scoraig
http://www.scoraigwind.co.uk
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Re: [RE-wrenches] unique battery bank design question

[Exeltech]

Hi Jason,

Well designed off-the-shelf converters can achieve 90% efficiency, and as you 
mention, this will vary a bit depending on the rated output current of the 
converter vs. the actual load current.

I've designed and built  24V @ 25A to 12V @ 50A converters for my own use that 
are in the 95% realm.

Your mileage may vary.

Dan


--- On Thu, 9/1/11, Jason Szumlanski  wrote:

From: Jason Szumlanski 
Subject: Re: [RE-wrenches] unique battery bank design question
To: "RE-wrenches" 
Date: Thursday, September 1, 2011, 3:07 PM

Dan,  What kind of efficiency level (%) can you get out of a DC-DC supply on a 
small load, say <5A @ 12V with a 48V->12V converter? Is the efficiency level 
highly variable depending on load as a percentage of the converter’s maximum 
capacity, or is it pretty constant?  I run into this once in a while, so this 
piece of information would help me make some better decisions.  Thanks,  Jason 
SzumlanskiFafco Solar 
   
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Re: [RE-wrenches] unique battery bank design question

[The Solar Powered Office of Tom Duffy]

Mac
 
Don't do it! ...use a dc to dc converter to step down to each bus 12v 24v
etc. and then just hook up the equipment thru breakers to each bus
 

  Tom Duffy

  Systems Design Engineer

 t...@thesolar.biz

   575-539-2111 X 301

Although no trees were killed in the sending of this message, a large number
of electrons were terribly inconvenienced.


 

Confidentiality Notice: This message including any attachments is for the
sole use of the intended recipient(s) and may contain confidential and
privileged information. Any unauthorized review, use, disclosure or
distribution is prohibited. If you are not the intended recipient, please
contact the sender and delete any copies of this message.

 

  _  

From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of mac Lewis
Sent: Thursday, September 01, 2011 1:52 PM
To: RE-wrenches@lists.re-wrenches.org
Subject: [RE-wrenches] unique battery bank design question


Hello wrenches, 

I have a battery bank questions.  I have an Oil & Gas client interested in
setting up an off-grid control system that has a various DC loads at 12VDC,
24 VDC and 48 VDC.  My thought is to build a 48 V battery bank and tap off
the bank at various points to create a 12V bus, 24V bus and 48V bus.  I am a
bit concerned about unequal loading of the batteries.  Has anyone dealt with
something like this that would like to share some insight?

Thanks


-- 





Mac Lewis



"Yo solo sé que no sé nada." -Sócrates


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Re: [RE-wrenches] unique battery bank design question

[John DeBoever]

Mac,

Never tap a battery bank off various voltages. This will result into unbalanced 
battery units, thus confusing the charger, resulting into unbalance charge, 
boiling ones and sulfating others occurring, killing the battery fast...
When facing various loads with various operating voltage 12V, 24V, 48V, 
configuring the battery bank for the larger load voltage is recommended (due to 
losses optimization) and use DC/DC converters for the other loads.  Note that 
it is easier to find step-down DC/DC converters. Consider high efficiency DC/DC 
converters. Typically not less than 85%. Expensive ones have 90-95% 
efficiencies.

John
John F. DeBoever
Global Projects Director - Renewable Energy
Trojan Battery Company

12380 Clark Street
Santa Fe Springs, CA 90670
Tel: +1-562-236-3000 Ext. 3139
Cell: +1-514-514-7600 - Time Zone: EST USA (GMT-5)
Fax: +1-562-236-3239
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From: re-wrenches-boun...@lists.re-wrenches.org 
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of mac Lewis
Sent: Thursday, September 01, 2011 3:52 PM
To: RE-wrenches@lists.re-wrenches.org
Subject: [RE-wrenches] unique battery bank design question

Hello wrenches,

I have a battery bank questions.  I have an Oil & Gas client interested in 
setting up an off-grid control system that has a various DC loads at 12VDC, 24 
VDC and 48 VDC.  My thought is to build a 48 V battery bank and tap off the 
bank at various points to create a 12V bus, 24V bus and 48V bus.  I am a bit 
concerned about unequal loading of the batteries.  Has anyone dealt with 
something like this that would like to share some insight?

Thanks

--



Mac Lewis

"Yo solo sé que no sé nada." -Sócrates



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Re: [RE-wrenches] unique battery bank design question

[Jason Szumlanski]

1a x 12V x 24hrs = 288 watt-hours on a 48,000 watt-hour battery. My math
shows 0.6% of the nominal capacity. And that assumes there is no
charging source present.

That being said, I would agree that avoiding it altogether is the wise
decision, but there has to be a level at which the tapped load is
inconsequential. I'm just curious what that level is! 

Jason Szumlanski
Fafco Solar


-Original Message-
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Hugh
Sent: Thursday, September 01, 2011 4:21 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] unique battery bank design question

At 15:57 -0400 1/9/11, Jason Szumlanski wrote:

>  A 1A @ 12V fan on a 1000aH @48V battery bank can't make any real 
>difference. Correct me if I am wrong!
>

Yes that is wrong, because after 4 days you have removed 10% of the 
nominal capacity or about 20% of the usable capacity.

Tapping off batteries is bad practice as universally agreed.  One way 
to mitigate it could be to use separate shunt regulators (diversion 
load controllers) for each 12-volt portion.  This would probably be a 
healthy feature for 'balancing' any 48 volt battery and would 
possibly rescue a tapped battery, given enough surplus energy 
availability (which is usually the key thing for battery health).

Just a thought.

The snag is the cost.  ho hum.
-- 
Hugh Piggott

Scoraig
http://www.scoraigwind.co.uk
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Re: [RE-wrenches] Ladders for Inspectors

[Andrew Truitt]

> Jason - In my experience AHJs run the gamut on this issue, from refusing to
> get on the roof to requiring OSHA compliant access to all areas of the
> system supplied by the installer.  In the latter case I would ALWAYS have
> someone on site, even if they had to wait all day (not uncommon).  They
> didn't have to be a crew leader, but I did try to send someone who could
> speak intelligently about the system.  In my commissioning work I also
> require that the contractor supplies OSHA compliant means to access all
> system components and I've never gotten any push-back on that, though the
> definition of "OSHA compliant" is sometimes debated and I've probably gotten
> on some ladders that I shouldn't have.  If you needed a man-lift to access
> the system you wouldn't expect the inspector to provide that, so why is a
> ladder any different?
>
> That being said, if they are requiring it and costing you money to supply
> it, and then not using it, that would pickle my giblets a little bit too.
>
>
> For a brighter energy future,
>
>
> Andrew Truitt  MSc., LEED GA
> NABCEP Certified PV Installer™ (ID# 032407-66)
>  Principal
> Truitt Renewable Energy Consulting
> (202) 486-7507
>  
> http://www.linkedin.com/pub/andrew-truitt/8/622/713
>


>
> "Don't get me wrong: I love nuclear energy! It's just that I prefer fusion
> to fission. And it just so happens that there's an enormous fusion reactor
> safely banked a few million miles from us. It delivers more than we could
> ever use in just about 8 minutes. And it's wireless!"
>
> ~William McDonough
>
>
>
>
>
>
> On Thu, Sep 1, 2011 at 12:09 PM, Jason Szumlanski wrote:
>
>> Ha – The roof we are dealing with today has 26’ high eaves and it is a
>> steep metal roof. There is no way they are actually getting up there. When
>> we do timed inspections in other jurisdictions they rarely step foot on a
>> ladder. Maybe it’s a testament to our reputation, but we are paying for the
>> inspection - it would be nice if it were actually done.
>>
>> ** **
>>
>> Jason Szumlanski
>>
>> Fafco Solar 
>>
>> ** **
>>
>> ** **
>>
>> *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto:
>> re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Benn At
>> DayStarSolar
>> *Sent:* Thursday, September 01, 2011 1:55 PM
>> *To:* RE-wrenches
>> *Subject:* Re: [RE-wrenches] Ladders for Inspectors
>>
>> ** **
>>
>> This issue came up for me as well.
>>
>>  I dont recall at the moment where it is written, perhaps it was OSHA,
>>  but apparently the contractor (permit puller) is responsible for supplying
>> access and safety equip ie, fall protection (with exception of personal PPE,
>> boots, hat, glasses) for inspectors to inspect the permitted work. 
>>
>> ** **
>>
>> You do bring up a valid issue re leaving a ladder up for them, especially
>> considering they typically leave a pretty big window open for when they will
>> drop by. I believe that this puts the onus on the inspector to provide an
>> accurate inspection time. 
>>
>> ** **
>>
>> I'm impressed that your inspector even wants to get up on a ladder!!!
>>
>> ** **
>>
>> benn
>>
>> Sent from a 'smart' phone, with tiny keys. Please excuse shortcuts and
>> typos. 
>>
>>
>> On 2011-09-01, at 8:46 AM, "Jason Szumlanski" 
>> wrote:
>>
>> Is anyone being forced to leave ladders up and secured in place for
>> inspectors? One jurisdiction in our neck of the woods is insisting that we
>> do this. I believe this is a serious risk to public safety, and I won’t be
>> responsible for some homeowner or curious child getting injured on or around
>> a ladder propped against a building. The jurisdiction does not do timed
>> inspections, so we can’t even be there to raise the ladder for them.
>>
>>  
>>
>> Can anyone point to some resources (OSHA?) that I can use to convince the
>> building official that this is a very bad idea?
>>
>>  
>>
>> Jason Szumlanski
>>
>> Fafco Solar
>>
>>  
>>
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>

Re: [RE-wrenches] unique battery bank design question

[mac Lewis]

Glad I asked!  Do these converters have a decent expected lifetime?  If
anyone has any good DC-DC converters to peddle, please contact me off list.

Thanks for the help.

On Thu, Sep 1, 2011 at 2:48 PM, Jason Szumlanski wrote:

> 1a x 12V x 24hrs = 288 watt-hours on a 48,000 watt-hour battery. My math
> shows 0.6% of the nominal capacity. And that assumes there is no
> charging source present.
>
> That being said, I would agree that avoiding it altogether is the wise
> decision, but there has to be a level at which the tapped load is
> inconsequential. I'm just curious what that level is!
>
> Jason Szumlanski
> Fafco Solar
>
>
> -Original Message-
> From: re-wrenches-boun...@lists.re-wrenches.org
> [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Hugh
> Sent: Thursday, September 01, 2011 4:21 PM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] unique battery bank design question
>
> At 15:57 -0400 1/9/11, Jason Szumlanski wrote:
>
> >  A 1A @ 12V fan on a 1000aH @48V battery bank can't make any real
> >difference. Correct me if I am wrong!
> >
>
> Yes that is wrong, because after 4 days you have removed 10% of the
> nominal capacity or about 20% of the usable capacity.
>
> Tapping off batteries is bad practice as universally agreed.  One way
> to mitigate it could be to use separate shunt regulators (diversion
> load controllers) for each 12-volt portion.  This would probably be a
> healthy feature for 'balancing' any 48 volt battery and would
> possibly rescue a tapped battery, given enough surplus energy
> availability (which is usually the key thing for battery health).
>
> Just a thought.
>
> The snag is the cost.  ho hum.
> --
> Hugh Piggott
>
> Scoraig
> http://www.scoraigwind.co.uk
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-- 



Mac Lewis

*

"Yo solo sé que no sé nada." -Sócrates
*
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Re: [RE-wrenches] unique battery bank design question

[Darryl Thayer]

I am both interested in the idle power, and the operating efficiency

This often comes up, but what does it require to allow a DC appliance to wait 
and simply turn on when when necessary and not waste power when it is off?  
Darryl

From: Exeltech 
To: RE-wrenches 
Sent: Thursday, September 1, 2011 3:30 PM
Subject: Re: [RE-wrenches] unique battery bank design question

Hi Jason,

Well designed off-the-shelf converters can achieve 90% efficiency, and as you 
mention, this will vary a bit depending on the rated output current of the 
converter vs. the actual load current.

I've designed and built  24V @ 25A to 12V @ 50A converters for my own use that 
are in the 95% realm.

Your mileage may vary.

Dan


--- On Thu, 9/1/11, Jason Szumlanski  wrote:


>From: Jason Szumlanski 
>Subject: Re: [RE-wrenches] unique battery bank design question
>To: "RE-wrenches" 
>Date: Thursday, September 1, 2011, 3:07 PM
>
>
>Dan,
> 
>What kind of efficiency level (%) can you get out of a DC-DC supply on a small 
>load, say <5A @ 12V with a 48V->12V converter? Is the efficiency level highly 
>variable depending on load as a percentage of the converter’s maximum 
>capacity, or is it pretty constant?
> 
>I run into this once in a while, so this piece of information would help me 
>make some better decisions.
> 
>Thanks,
> 
>Jason Szumlanski
>Fafco Solar
>
>
>  ___List sponsored by Home Power 
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Re: [RE-wrenches] unique battery bank design question

[Darryl Thayer]

I would guess that it depends upon the use cycle, you always put more electrons 
back in than you take out, If you are assuming a 90% recharge efficiency 
recharging once every three days, a few percent of the recharge excess energy 
could be used.  BUT I strongly agree I have seen too many problems with taped 
battery banks so avoid is the first rule.  
 
This would make an interesting measurement. 

From: mac Lewis 
To: RE-wrenches 
Sent: Thursday, September 1, 2011 3:59 PM
Subject: Re: [RE-wrenches] unique battery bank design question


Glad I asked!  Do these converters have a decent expected lifetime?  If anyone 
has any good DC-DC converters to peddle, please contact me off list. 

Thanks for the help. 


On Thu, Sep 1, 2011 at 2:48 PM, Jason Szumlanski  wrote:

1a x 12V x 24hrs = 288 watt-hours on a 48,000 watt-hour battery. My math
>shows 0.6% of the nominal capacity. And that assumes there is no
>charging source present.
>
>That being said, I would agree that avoiding it altogether is the wise
>decision, but there has to be a level at which the tapped load is
>inconsequential. I'm just curious what that level is!
>
>Jason Szumlanski
>Fafco Solar
>
>
>
>-Original Message-
>From: re-wrenches-boun...@lists.re-wrenches.org
>[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Hugh
>Sent: Thursday, September 01, 2011 4:21 PM
>To: RE-wrenches
>Subject: Re: [RE-wrenches] unique battery bank design question
>
>
>At 15:57 -0400 1/9/11, Jason Szumlanski wrote:
>
>>  A 1A @ 12V fan on a 1000aH @48V battery bank can't make any real
>>difference. Correct me if I am wrong!
>>
>
>Yes that is wrong, because after 4 days you have removed 10% of the
>nominal capacity or about 20% of the usable capacity.
>
>Tapping off batteries is bad practice as universally agreed.  One way
>to mitigate it could be to use separate shunt regulators (diversion
>load controllers) for each 12-volt portion.  This would probably be a
>healthy feature for 'balancing' any 48 volt battery and would
>possibly rescue a tapped battery, given enough surplus energy
>availability (which is usually the key thing for battery health).
>
>Just a thought.
>
>The snag is the cost.  ho hum.
>--
>Hugh Piggott
>
>Scoraig
>http://www.scoraigwind.co.uk
>___
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-- 



Mac Lewis

"Yo solo sé que no sé nada." -Sócrates

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Re: [RE-wrenches] unique battery bank design question

[Exeltech]

At the risk of sounding sarcastic (and I assure this is not my intent) .. to 
allow a DC appliance to wait and simply turn on when when necessary and not 
waste power when it is off would take a battery ..  internal or external to the 
appliance.

Something has to keep the appliance powered.  The best we can do is minimize 
the idle power consumption.

"Super capacitors" can provide some degree of backup for very low-power needs 
(micro-watts), but they too will go dead over time if not used, or when given a 
long-term power draw without being recharged (sounds like a battery again .. 
no?).

Dan


--- On Thu, 9/1/11, Darryl Thayer  wrote:

From: Darryl Thayer 
Subject: Re: [RE-wrenches] unique battery bank design question
To: "RE-wrenches" 
Date: Thursday, September 1, 2011, 5:01 PM

I am both interested in the idle power, and the operating efficiency

This often comes up, but what does it require to allow a DC appliance to wait 
and simply turn on when when necessary and not waste power when it is off?  
Darryl



From: Exeltech 
To: RE-wrenches 
Sent: Thursday, September 1, 2011 3:30 PM
Subject: Re: [RE-wrenches] unique battery bank design question
 




Hi Jason,

Well designed off-the-shelf converters can achieve 90% efficiency, and as you 
mention, this will vary a bit depending on the rated output current of the 
converter vs. the actual load current.

I've designed and built  24V @ 25A to 12V @ 50A converters for my own use that 
are in the 95% realm.

Your mileage may vary.

Dan


--- On Thu, 9/1/11, Jason Szumlanski  wrote:


From: Jason Szumlanski 
Subject: Re: [RE-wrenches] unique battery bank design question
To: "RE-wrenches" 
Date: Thursday, September 1, 2011, 3:07 PM






Dan,
 
What kind of efficiency level (%) can you get out of a DC-DC supply on a small 
load, say <5A @ 12V with a 48V->12V converter? Is the efficiency level highly 
variable depending on load as a percentage of the converter’s maximum capacity, 
or is it pretty constant?
 
I run into this once in a while, so this piece of information would help me 
make some better decisions.
 
Thanks,
 
Jason Szumlanski
Fafco Solar 


 
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Re: [RE-wrenches] unique battery bank design question

[Hugh]

At 16:48 -0400 1/9/11, Jason Szumlanski wrote:

1a x 12V x 24hrs = 288 watt-hours on a 48,000 watt-hour battery. My math
shows 0.6% of the nominal capacity. And that assumes there is no
charging source present.


Wrong again.  Sorry.

You are taking out four times that percentage out of just one quarter 
of the whole battery.  In four days it will amount to 20% of the 
usable capacity (which is only really 500Ah) of one 12V battery. 
Charging the whole battery will not restore balance unless you dump 
an equivalent 98 Ah of charge out of the other 36 volts, making this 
process at best 25% efficient and probably ending in tears.

--
Hugh Piggott

Scoraig
http://www.scoraigwind.co.uk
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Re: [RE-wrenches] unique battery bank design question

[Jason Szumlanski]

Sorry - I missed the 4 days part of your post. I'm not sure where you
came up with 4 days - sounds kind of arbitrary.

I'd be interested to know if it makes any difference at all if you tap a
12V load only when there is a 48V charging source present (assuming the
charging source current is significantly greater than the load). Assume
you want to run a small 12V fan only when batteries are charging. In
that case, I would guess the impact is far less important, or perhaps
nil. Maybe this is a case where a tap is acceptable. Not sure...

I'm not trying to argue that a tap is a good idea - it's clearly not
ideal. I'm just trying to be devil's advocate and run this issue to
ground. If there is a legitimate reason to pursue this course of action
(cost, simplicity, size, weight, etc,) it's a good idea to talk about
it.

Another option I've been reading up on is a Battery Equalizer/Battery
Balancer. These seem to be commercially available to tap 12V off a 24V
battery, but I am not sure about the efficiency or cost comparison to a
DC-DC converter, or how/if multiple units could be implemented in a 48V
system.

Jason Szumlanski
Fafco Solar

 
-Original Message-
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Hugh
Sent: Thursday, September 01, 2011 5:05 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] unique battery bank design question

At 16:48 -0400 1/9/11, Jason Szumlanski wrote:
>1a x 12V x 24hrs = 288 watt-hours on a 48,000 watt-hour battery. My
math
>shows 0.6% of the nominal capacity. And that assumes there is no
>charging source present.

Wrong again.  Sorry.

You are taking out four times that percentage out of just one quarter 
of the whole battery.  In four days it will amount to 20% of the 
usable capacity (which is only really 500Ah) of one 12V battery. 
Charging the whole battery will not restore balance unless you dump 
an equivalent 98 Ah of charge out of the other 36 volts, making this 
process at best 25% efficient and probably ending in tears.
-- 
Hugh Piggott

Scoraig
http://www.scoraigwind.co.uk

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Re: [RE-wrenches] unique battery bank design question

[William Miller]

Or a switch...




At 03:14 PM 9/1/2011, you wrote:
 .. to allow a DC appliance to wait and simply turn on when when 
necessary and not waste power when it is off would take a battery 
..  internal or external to the appliance.
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