[RE-wrenches] Charging a 108V battery bank

[larry at starlightsolar.com]

Hi Jason,

Considering temperature affect on voltage, you would choose something just above the Vmp. As the array becomes illuminated, voltage will rise but the battery is always a full load to the PV array. Voltage will never go higher than battery OV protection while connected or the open circuit voltage when disconnected. 

If the Vmp is close to the battery max voltage, MPPT does not matter as the gains are small. The battery can be charged at 3C so current is not an issue either. 


Larry Crutcher
Starlight Solar Power Systems




On Jul 1, 2021, at 3:48 PM, Rockisland <wapalco at rockisland.com> wrote:

Hi Larry,

So no MPPT in that situation and how much extra Vmp on the PV’s is recommended above operating battery Voltage?

Thanks,

Jason

RemoteEnergy.org <http://remoteenergy.org/>


> On Jul 1, 2021, at 2:18 PM, larry at starlightsolar.com <mailto:larry at starlightsolar.com> wrote:
> 
> Just thought I would throw out that with an Elite Power Solutions Li-ion battery system you can connect a PV solar source directly to the battery, no PV controller needed. The EMS will monitor each cell and open the charge relay when the battery is full. The dual solenoid controller will allow loads to operate uninterrupted. 
> 
> Use a DC down converter to share power to the 48V battery or loads.
> 
> Larry Crutcher
> Starlight Solar Power Systems
> 
> 
> 
> 
> On Jun 30, 2021, at 1:50 PM, Dave Tedeyan <dave at sungineersolar.com <mailto:dave at sungineersolar.com>> wrote:
> 
> Hi All, 
> 
> I am going to be working with someone who plans to completely electrify a boat. The electric motor is meant to run on nine 12V batteries, or 108V. The motor manufacturer recommends a charger that can run on 120V or 240V. But has anyone seen a charger that can take solar power and directly charge a battery bank of 108V? The alternative that I see here is to have two separate battery banks, one for the motor, and one for house loads. Then we would have the solar charge a 48V battery bank, and then use an inverter to charge the 108V battery bank. It seems inefficient, although that may be the only choice.
> 
> A separate but related question: what is special about a marine inverter? If there is a 5kw charger for the battery bank, we will need a large inverter to handle this plus other AC loads, and I am not sure if there are "marine" inverters this large. And so other than concerns about getting wet, is there harm to putting a Radian, or a Sol-Ark on a boat?
> 
> Cheers,
> Dave
> 
> -- 
>  <https://www.sungineersolar.com/>	
> Dave Tedeyan, P.E.
> Owner | Sungineer Solar
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> a: 1653 Slaterville Rd. | Ithaca, NY 14850
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