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Re: [Amps] LDMOS amp off battery?

To: Manfred Mornhinweg <>
Subject: Re: [Amps] LDMOS amp off battery?
From: Roger <>
Date: Mon, 23 Oct 2017 13:29:14 -0700
List-post: <>
6v batteries would be a better option.

73, Roger
Grid Busters

On Mon, Oct 23, 2017 at 10:49 AM, Manfred Mornhinweg <>

> Steve,
> Is anyone running a 50V LDMOS amp off a 48V battery system?
> I have considered it, but not done yet. I generate my own power, with a
> turbine in a creek, and in summer I can generate only about 400 to 700W, so
> I absolutely need batteries to run a legal limit amp.
> But there are two choices: A local battery bank just for an amp, or using
> the main battery bank I have in place for the whole house - in that case
> the amp needs just its normal AC supply, and my DC-AC inverter takes care
> of the rest. That solution is cheaper to implement in my situation, but
> incurs in higher losses.
> I've been rolling this idea around for a while for portable use, but the
>> problem is a "48V" battery system on equalise is more than a little bit
>> more than 50V - more like 58V !
>> Any ideas?
> First idea: Don't equalize the batteries while you are operating! During
> operation keep the charger regulated to 50V. The system voltage will then
> vary between about 48 and 50V as you operate, which should be OK. The
> batteries will lose charge, but will not go into deep discharge. After the
> operating session, raise the charge voltage to whatever is necessary for a
> complete charge, including equalization once every several months. Even if
> the voltage remains applied to the LDMOSFET, it's no problem while it's not
> being driven, since its maximum drain voltage rating is well over 100V.
> And another idea: Use a battery bank of whatever voltage you like, either
> lower or higher but not 48V, run the batteries at their proper voltage, and
> use a switching regulator to produce a stable, clean 50V. Depending on the
> battery voltage that can be a buck or a boost circuit. It gives you the
> advantage of a stable, constant supply voltage, and if the battery voltage
> is reasonably close to 50V, then the size and weight and cost of the
> regulator is small.
> Manfred
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