Solar panels in the 50-100w range?

[trae]

Afternoon everyone,

Looking for some specific suggestions for a solar panel. Currently travelling with a 500Wh home made lithium pack and interested in being able to recharge it. I live in the pacific north west so I suspect a 100 watt panel is likely the minimum I should go for. I need something portable - it's not going to live on my vehicle full time.

When I researched this a few years back, Renogy suitcase units came highly recommended. Is that still the case?
How about something foldable like this: https://www.amazon.com/gp/product/B...42e-e8f213ef368b&pf_rd_r=Y2KYF3C9GC13XZZJ5QF5

I understand the panel composition/wiring has a lot to do with the final efficiency. If anyone has any specific recommendations I'd appreciate it.

Thanks

 

[luthj]

With a lithium pack it should take whatever your panel will produce, right up till full. The rigid faced (glass) folding panels are the best bet. The flex units just don't hold up with routine usage. Any PWM charge controller will work. Obviously you will want to self disconnect when the pack gets full. Or choose a more advanced controller that won't try to absorb and float the pack. Most charge controllers are designed around lead batteries, so they don't terminate the charge, but instead sit for hours at the absorb voltage.

 

[trae]

With a lithium pack it should take whatever your panel will produce, right up till full. The rigid faced (glass) folding panels are the best bet. The flex units just don't hold up with routine usage. Any PWM charge controller will work. Obviously you will want to self disconnect when the pack gets full. Or choose a more advanced controller that won't try to absorb and float the pack. Most charge controllers are designed around lead batteries, so they don't terminate the charge, but instead sit for hours at the absorb voltage.

Thanks! I'm not worried about charge controllers 'cause my pack has a BSM which will terminate the charging current at the appropriate value. For rigid panels, do you have any suggestions? Is the aforementioned Renogy still a good buy?

 

[luthj]

These folding panels look decent to me. Its basically a rigid panel split in two with a controller attached. Should give a good life.

https://www.amazon.com/Renogy-Monocrystalline-Foldable-Waterproof-Controller/dp/B079JVBVL3/ref=sr_1_3?keywords=renogy+folding&qid=1570535640&sr=8-3

This panel looks comparable. The controllers aren't the best quality, for for lithium packs it doesn't matter as much.

https://www.amazon.com/HQST-Monocrystalline-Portable-Suitcase-Controller/dp/B07L8XWJ1X/ref=sr_1_8?keywords=renogy+folding&qid=1570535778&sr=8-8

 

[dwh]

You should be worried about charge controllers. The BMS serves a different purpose.

For a 40ah battery and a 100w panel, normally I would say an MPPT charge controller isn't worth the cost. But...for a lithium in PNW conditions I would reconsider that.

The main benefit of an MPPT controller is that it allows the solar to operate at the voltage of max power (Vmp) instead of operating at battery voltage, which it would do with a PWM controller or no controller at all.

Getting the max watt*hours out of the solar instead of 80% of max might be worth doing with a lithium battery in the PNW.

 

[trae]

You should be worried about charge controllers. The BMS serves a different purpose.

For a 40ah battery and a 100w panel, normally I would say an MPPT charge controller isn't worth the cost. But...for a lithium in PNW conditions I would reconsider that.

The main benefit of an MPPT controller is that it allows the solar to operate at the voltage of max power (Vmp) instead of operating at battery voltage, which it would do with a PWM controller or no controller at all.

Getting the max watt*hours out of the solar instead of 80% of max might be worth doing with a lithium battery in the PNW.

Thanks, I haven't considered that MPPT are more efficient. Especially with our not particularly sunny weather.

BMS will take care of not overcharing the batteries, that's why I'm not worried. I am worried about not getting sufficient charge though

Thanks for your advice.

 

[luthj]

You should not rely on the BMS to prevent overcharging, it should be the last line of defense. The charge controllers should be configured to charge at the correct voltage, and stop when the battery if full (no/short absorb) and no (or very low) float voltage. The only recourse a BMS has to stop an overcharge scenario is to disconnect the pack from the charge source. All-in-one drop in style batteries typically disconnect the both charge and discharge loads as one.