[RE-wrenches] bad battery = system overvoltage = dead inverter

[Ryan]

Chris
Yes some charge controllers regulate pretty slow. So if the battery goes 
away on them they can skyrocket in voltage on there battery side before 
they can catch themselves. This may only be for 2-3 seconds or so but 
that is all it takes to send an inverter up in smoke.

This is also the reason you here people complain of small AGM battery 
banks going over voltage from time to time. These same slower 
controllers will take that same 2-3 seconds to catch themselves if a big 
load is turned off.

Ryan
-- 
Ryan Stankevitz
Technical Support Manager
MidNite Solar Inc.
ryan at midnitesolar.com
360-403-7207 XT 151
Skype ID ryan.midnite

On 3/16/2013 10:28 AM, Chris Mason wrote:
> I want to understand the issue if you don't mind. Are you saying that 
> an MPPT charge controller has no voltage limits? I would have presumed 
> a CC would know that there is no batteries attached.
> From your email, you want a device that will measure the CC output 
> voltage, and shut it down if it exceeds a limit. For the 48V systems I 
> normally install, that would be ...65V?
> It would be trivial to setup an Arduino with a voltage input to 
> monitor the CC output voltage. The harder part would be to turn off 
> the CC when there was excessive voltage. Unless the CC had an Aux 
> input, you would need a contact rated for the DC Current. Other than, 
> it's very simple to do.
>
>
> On Fri, Mar 15, 2013 at 11:05 PM, Dan Fink <danbob88 at gmail.com 
> <mailto:danbob88 at gmail.com>> wrote:
>
>     This has been happening all too frequently here. We live in a big area
>     of off grid homes, dozens of systems.
>     Lost a customers Trace 2624 this morning; One L-16 in older 24v bank
>     opened internally. PV array/MPPT control zorched inverter as soon as
>     the sun came up. First indication of problems last nite when customer
>     hit microwave to warm up dinner and inverter went crazy. This morning
>     the bad battery showed 3.2v (yes, I would expect 2 or 4 also) the rest
>     the usual 6+v. Turned on PV array, bad battery immediately up to 11v
>     (yes, 6v L16).
>
>     Somebody needs to build a "battery condom" with big stacked diodes on
>     a big heat sink or some such solution. A voltage brick wall for system
>     charging inputs. MPPT PV controllers do NOT protect a inverter from
>     input overvoltage if all or part of the battery bank disappears! And
>     last year we saw a nice battery box fire and zorched inverters due to
>     similar -- dual 48v L16 strings, one cell failed and opened, other
>     string dumped everything into the bad one, smoke and flames. Parallel
>     fusing would have stopped that......but not stopped the loss of dual
>     stacked XW inverters from PV overvoltage.
>
>     Or am I missing something here?
>
>     Dan Fink,
>     Executive Director;
>     Otherpower
>     Buckville Energy Consulting
>     Buckville Publications LLC
>     NABCEP / IREC accredited Continuing Education Providers
>     970.672.4342
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> -- 
> Chris Mason
> President, Comet Systems Ltd
> www.cometenergysystems.com <http://www.cometenergysystems.com>
> Cell: 264.235.5670
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