[RE-wrenches] Charging 48V Battery with One Module

[Kent Osterberg]

Genasun is a very interesting option and it looks like they also have a 
charge controller set for 54.2 volts which is probably the right charge 
voltage, but it is only rated for a PV max power point current of 8 amps 
(maybe 9). Ten amps from a 420 W solar panel might be pushing it too 
hard, certainly beyond its specs.

Most "dumb" voltage converters operate around 85% efficiency. If taking 
that much loss, it would be better to use a lower power, higher voltage 
PV module with a common MPPT controller. That is one less part to fail too.

Kent Osterberg
Blue Mountain Solar

On 4/12/2021 7:27 PM, Jason Szumlanski wrote:
> That's what I was thinking. Not a MPPT controller... Just a "dumb" 
> booster that put the voltage high enough for any off the shelf MPPT 
> controller. But it can't really work like that. The MPPT function need 
> to be at the lower voltage side of the device I think.
>
> On Mon, Apr 12, 2021, 9:38 PM Nick A Lucchese <lucchesesolar at me.com 
> <mailto:lucchesesolar at me.com>> wrote:
>
>     Jason, Mack, Maverick, Kent and John,
>
>     Looks like the Genasun absorb set points are 57.6 right? Were you
>     still needing this for a LiFePO4 battery option Jason? Maybe they
>     offer a different voltage setpoint option I’m not seeing? I’ve
>     needed something like this for a couple applications as well. Even
>     if something like this existed to boost output voltage before
>     going into a larger controller like an FM60 or Midnite option.
>
>     At least with today’s newer 60 cell modules we can put a couple in
>     series and Vmpp will still be high enough to hit absorb set points
>     for lithium options even after heating up. A luxury we didn’t have
>     in the past with FLA and periodic requirements for EQ’ing. I know
>     two 60 cell modules is much more footprint than a single but at
>     least we have that.
>
>     Enjoy your night, Nick
>
>>     On Apr 12, 2021, at 10:40 AM, Jason Szumlanski
>>     <jason at floridasolardesigngroup.com
>>     <mailto:jason at floridasolardesigngroup.com>> wrote:
>>
>>     I want to charge a 51.2V LiPO battery with a single 420W 72-cell
>>     module. Vmp is 40.14V.
>>
>>     It's one of those situations where I just need a lot of battery
>>     capacity as a backup for a specified time period, but it doesn't
>>     matter how long it takes to charge it back up. And I have space
>>     for exactly one 72-cell module.
>>
>>     It's going to be a Victron inverter. I'm not sure if they make a
>>     DC-DC solution for this charging scenario or if there is another
>>     way to accomplish it without too much cost and complexity. I was
>>     half-heartedly thinking about an AC coupled microinverter, but
>>     that has drawbacks in terms of efficiency I think. Maybe that's
>>     not any worse than DC-DC conversion - I'm not sure. AC Coupling
>>     would probably be cheaper and easier. Monitoring might be
>>     difficult/limited. And AC coupling would require that the
>>     inverter be on (inverting) which isn't ideal for this situation
>>     either.
>>
>>     Thanks in advance,
>>
>>     Jason Szumlanski
>>     Florida Solar Design Group
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