[RE-wrenches] 24 vs. 48

Kent Osterberg kent at coveoregon.com
Tue Jan 17 14:02:35 PST 2012


Mark,

If you are working with industrial batteries where you have lots of 
options for battery capacity, what you are saying makes sense. But not 
if you are assembling commercial (L16 or T-105 types) batteries to get 
more capacity. The reduced effort for measuring specific gravity 
watering for a 24-volt system with 12 cells, I'll concede to. But there 
is less to gain when it comes to watering, the 12 cells should end up 
taking as much water and almost as much time to put it in the cells.

In addition to being more efficient, the 48-volt inverter can operate 
with one or two 2-volt cells removed.

Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com
t: 541-568-4882


On 1/17/2012 11:19 AM, Mark Frye wrote:
> Interesting.
>
> I can choose an OB VFX3524 w/ 85 ADC or an OB VFX3648 w/ 45 ADC of charging
> capacity.
>
> And assuming that I need C/10 during bulk charging (and the importance of
> this is really what I am asking about) then:
>
> VFX3524: 85 ADC * 10 = 850 AH * 24 VDC = 20.4 kWH battery bank
>
> VFX3648: 45 ADC * 10 = 450 AH * 48 VDC = 21.6 kWH battery bank
>
> OK, so it's about a wash either way in terms of stored energy.
>
> But assuming for the moment that distances are short and the initial
> difference in copper costs are small, wouldn't you rather have half the
> number of individual cells to maintain...less watering, less SG measuring,
> lower overall "part" (individual 2V cells) count?
>
> Mark Frye
> Berkeley Solar Electric Systems
> 303 Redbud Way
> Nevada City,  CA 95959
> (530) 401-8024
> www.berkeleysolar.com
>
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of R Ray
> Walters
> Sent: Tuesday, January 17, 2012 10:38 AM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] 24 vs. 48
>
> The only advantages of 24 v are that you can create smaller KWH battery
> banks, and that Bergey's XL.1 was only available in 24 v.
> Anytime the design allows, I jump to 48 v.
>
> R. Walters
> ray at solarray.com
> Solar Engineer
>
>
>
>
> On Jan 17, 2012, at 11:11 AM, Nathan Jones wrote:
>
>>
>> Mark,
>> It would seem to be a wash. As the voltage is halved the amperage is
> doubled in the battery bank. This would seem to require doubling the
> charging amperage so nothing is gained. On a system of any size the 48 volt
> gets the default nod here. Charge controllers handle twice the solar.
> Parallel battery strings are eliminated, or at least held to two. Wire
> sizing might be reduced on the low voltage side of things. And much easier
> future expansion possibilities, too.
>> Cheers,
>> Nathan Jones
>> Power Source Solar Inc
>>
>>
>> ------------------------------
>> On Tue, Jan 17, 2012 10:56 AM CST Mark Frye wrote:
>>
>>> Not really on topic to Jay's question, but...
>>>
>>> Is 48v always better than 24v?
>>>
>>> How important is bulk charging current to overall battery life?
>>>
>>> In some cases, isn't it better to use a 24v inverter/charger which
>>> can develop a higher charge current for a battery bank that has a
>>> higher AH rating?
>>>
>>> Mark Frye
>>> Berkeley Solar Electric Systems
>>> 303 Redbud Way
>>> Nevada City,  CA 95959
>>> (530) 401-8024
>>> www.berkeleysolar.com
>>>
>>> -----Original Message-----
>>> From: re-wrenches-bounces at lists.re-wrenches.org
>>> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of jay
>>> peltz
>>> Sent: Tuesday, January 17, 2012 8:43 AM
>>> To: RE-wrenches
>>> Subject: [RE-wrenches] battery buss bars
>>>
>>> Hi All,
>>>
>>> Where do I find buss bars for a battery parallel problem?
>>>
>>> I've got to fix a brand new ( not me) system, that has 4 sets of
>>> L-16's at 24v.
>>> Yea yea why didn't they go to 48?
>>>
>>> So I want to use buss bars to parallel them, and looking for premade
> ones.
>>> Thanks in advance,
>>>
>>> Jay
>>>
>>> Peltz power
>>>
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