Buck boost charging [RE-wrenches]

[Kirk Herander]

Drake,

I have been using buck-boost transformers for years to max out mod-sine's
battery chargers. it does work quite well, and I have never experienced an
inverter or load problem because of the higher voltage. I wire the xformer
to boost the genny's voltage by 10%, so after the boost a no-load voltage is
typically 130 vrms. Since you usually only need the boost when using an
undersized, "el-cheapo" generator, the voltage will still be depressed by
6 - 8 volts when under charger load. An average generator charge voltage of
122 - 125 vrms is well within the tolerance of a DR series inverter (Trace
tells me the AC FETs are rated at 200 vrms). On a DR 2424 with a 3500 watt
generator, for instance, I have seen the full 70 amps generated up to
standard bulk charge of 28.8 vdc. Before the boost, a max. charge rate was
45-50 amps with the same generator.

You could also raise the generator's AC output by adjusting the throttle,
increasing engine/generator speed, but the frequency will increase also as a
result.

Kirk
----- Original Message -----
From: "Drake Chamberlin" <solar at eagle-access.net>
To: <RE-wrenches at topica.com>
Sent: Sunday, June 16, 2002 2:56 PM
Subject: Buck boost charging [RE-wrenches]


> Hi Wrenches,
>
> The idea of using a buck boost transformer to improve battery charging
> efficiency from cheap generators makes sense.  My only concern is what
> effect boosted voltage would have on the loads fed through the transfer
> switch when using a modified sine wave inverter.
>
> Does anyone have any data on this?
>
> Thanks,
>
> Drake
>
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