[RE-wrenches] 24 vs. 48

[Nathan Jones]

Dan,
The typo I didn't catch on the quick proofread. I was actually referring to the wire sizing on the low voltage side of the charge controller and assuming higher module voltage than battery nominal. In light of that, the 48 volt system might allow reduced sizing of conducters over the 24.
I started my off grid life with 5 strings of T105s at 48 volts. I managed to keep that ship floating for 9 years but the bailing the last few years got pretty frantic. Life nowdays is a 48 volt string of 2 volt HUPs and the care and watering is delightful by comparison. There have been some good points on this thread for 24 volt banks but IMHO 48 is the way to go the vast majority of the time. Thanks for referencing the typo.
Nathan


------------------------------
On Tue, Jan 17, 2012 3:54 PM CST Exeltech wrote:

>The most common reason to go with a higher
>voltage (and thus lower current for a given
>overall wattage) is to allow the use of
>smaller conductors, which are generally
>easier to work with, and lower cost.
>
>There are fractional performance advantages
>to 48V over 24V in *some* equipment, but the
>advantages typically require lab-grade
>equipment to measure.  Equipment such as
>charge controllers and MPPT often benefit
>from operating at a higher voltage due to
>reduced energy loss in the copper.
>
>
>The above aside, Nathan appears to have
>mis-typed when he said:
>
>> "Wire sizing might be reduced on the low
>> voltage side of hings. 
>
>
>Wire sizes *increase* for a lower-voltage
>system at a given wattage and the same
>conductor losses as in a higher-voltage
>configuration.  A 24V system will have
>double the current than a 48V system at
>the same wattage.  Larger conductors are
>needed if the loss is to be the same in
>the 24V as in the 48V configuration.
>
>Dan
>Sr. Engineer
>Exeltech
>
>
>
>
>Dan
>
>
>--- On Tue, 1/17/12, Nathan Jones <solardude97 at yahoo.com> wrote:
>
>> From: Nathan Jones <solardude97 at yahoo.com>
>> Subject: Re: [RE-wrenches] 24 vs. 48
>> To: re-wrenches at lists.re-wrenches.org
>> Date: Tuesday, January 17, 2012, 12:11 PM
>> 
>> 
>> 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 
>
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