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<p>HI Mac;</p>
<p>I don't think the generators will be overloaded. i may be wrong,
but I believe they will just put out what they can, and the
batteries will slowly come up in voltage. I have a large fork
lift battery charger that is essentially unregulated, and it never
has been overloaded. It will definitely over charge the batteries
if left on too long, however. </p>
<p>The dead batteries are not going to act like a short circuit,
they will have quite a bit of internal resistance that will limit
the total current flow when charging. Again, you didn't mention
the brand or type of generator, so I can't say if I have
experience with it, so this is just my uninformed 0.02 worth.</p>
<p>Ray Walters</p>
<p>Remote Solar<br>
</p>
<br>
<div class="moz-cite-prefix">On 1/28/18 8:23 PM, Mac Lewis wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAOABG48u2yVWvf4QZeJudZBYmZMMJzt5NQxnHkQAnVnBvivPwQ@mail.gmail.com">
<div dir="ltr">Hello wrenches,
<div><br>
</div>
<div>I'm working on 3 off-grid telecom sites. They are designed
to operate solar only under most conditions but the project
manager ordered a custom-built 48 VDC generators, intended to
be used as the battery charger/backup power for the site.
These are ~20 kW generators, and can probably do about ~350Adc
at 48 Vdc at the elevation that these are sited. The battery
banks are 4 x 1000 Ahr GS Nanocarbon 48 battery strings and
can gobble up the 350Adc easily when they are discharged.</div>
<div><br>
</div>
<div>While discussing the generator operation with the generator
supplier, we have found this generator isn't capable of charge
control, or limiting its own output. The charge control
functionality isn't necessary at this site because we really
just need it to keep things online until the sun returns, a
simple 54 VDC float voltage would work. However, without the
generator being able to self-limit its output, we expect this
generator to stall when started because it can't regulate its
output current and will immediately become overloaded by the
discharged batteries.</div>
<div><br>
</div>
<div>I am trying to come up with some options to rectify this
serious design issue. One idea that immediately came to mind
was putting in some parallel solar charge controllers between
the DC generator output and the battery bank. If the
generator output could be dialed up to around 60-70 VDC, could
parallel solar charge controllers be used for charge
regulation? It would be kind of like charging a 48 V battery
bank from a 70 V battery bank. MPPT isn't applicable, could
the max current limit in the charge controller(s) be used to
regulate charge rate? Will the charge controllers blow up?
If not, what brand might work. Each site has 8 x Midnite
Classic 150s but I'm open to other manufacturers if it would
work. I am open to blowing up a charge controller in the shop
but I thought it best to ask first.</div>
<div><br>
</div>
<div>What are other ways to put this generator to use, and limit
its load?</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>Thanks for your input/comments</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
-- <br>
<div class="gmail_signature" data-smartmail="gmail_signature">
<div><br>
</div>
<div><font face="'times new roman', serif" color="#305A78"><br>
</font></div>
<div><br>
</div>
Mac Lewis<br>
<br>
<span style="font-family:'Times New
Roman';font-size:medium;color:rgb(255,153,0)"><b><font
face="Arial, Helvetica, sans-serif" size="3">
<p align="left"><font face="Verdana, Arial, Helvetica,
sans-serif" color="#000000"><span
style="font-size:small"><span
style="font-family:arial;font-weight:normal;color:rgb(48,90,120)"><font
face="'times new roman', serif">"Yo solo sé
que no sé nada." </font><span
style="font-weight:700;color:rgb(104,104,104)"><font
face="'times new roman', serif">-Sócrates</font></span></span></span></font></p>
</font></b></span></div>
</div>
</div>
<br>
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