Solar panel controller

On Thursday, December 31, 2020 at 4:08:21 PM UTC-8, jfitch wrote:
Using the BMS to control charging is not considered good engineering practice. The BMS may or may not be designed to operate that way, but once it disconnects the power bus driven by the solar will be at uncontrolled and possibly damaging voltage. Also, different designs of BMS reset (and reconnect) in different ways, and maybe not how you expected.
On Thursday, December 31, 2020 at 3:25:05 PM UTC-8, Eric Greenwell wrote:
Moshe Braner wrote on 12/31/2020 11:12 AM:
On 12/31/2020 12:50 PM, kinsell wrote:

Might want to be careful there. LFP's can be badly damaged when charging under cold conditions.

Good point. "Cold" as in "below freezing" (0C, 32F) for charging, not discharging. It seems
like an arbitrary number (these batteries are not made of water after all) but that's what they
say. I'd recommend at least several degrees above that for charging. If heading into the wave
with an LFP battery, if you have solar charging, you may want to disconnect that (unless the
charge controller does that automatically - do the LFP-aware ones do that?). Would need a
switch for that disconnection. Otherwise it's another reason to avoid solar panels in the
glider, which can't help a lot with the battery running time anyway.
Do some LiFe batteries with a BMS stop charging at a low temperature? If so, maybe that's one
to put in the glider.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

The BMS is being used for exactly what it is designed for: preventing over-voltage charging. Any question about recovering from an over-charge condition should be directed at the battery manufacturer, not speculated on. Additionally, the solar panel isn't charging the battery at all in flight, so this would only be an issue on the ground. My position is don't bother with the panels, they just don't contribute that much.

Tom

Most of the industry doesn't agree with you, but I expect you're used to that situation. The BMS is usually regarded as a safety device, the controller of last resort, to prevent fault conditions. What you propose is kind of like using the over current circuit breaker as the limit stop on your motor jack. Run 'er 'till she trips. Yeah it works, but not the best way. There is little downside in having a proper charge controller, and much potential downside in leaving it out.

On Thursday, December 31, 2020 at 6:19:20 PM UTC-8, 2G wrote:
On Thursday, December 31, 2020 at 4:08:21 PM UTC-8, jfitch wrote:
Using the BMS to control charging is not considered good engineering practice. The BMS may or may not be designed to operate that way, but once it disconnects the power bus driven by the solar will be at uncontrolled and possibly damaging voltage. Also, different designs of BMS reset (and reconnect) in different ways, and maybe not how you expected.
On Thursday, December 31, 2020 at 3:25:05 PM UTC-8, Eric Greenwell wrote:
Moshe Braner wrote on 12/31/2020 11:12 AM:
On 12/31/2020 12:50 PM, kinsell wrote:

Might want to be careful there. LFP's can be badly damaged when charging under cold conditions.

Good point. "Cold" as in "below freezing" (0C, 32F) for charging, not discharging. It seems
like an arbitrary number (these batteries are not made of water after all) but that's what they
say. I'd recommend at least several degrees above that for charging.. If heading into the wave
with an LFP battery, if you have solar charging, you may want to disconnect that (unless the
charge controller does that automatically - do the LFP-aware ones do that?). Would need a
switch for that disconnection. Otherwise it's another reason to avoid solar panels in the
glider, which can't help a lot with the battery running time anyway..
Do some LiFe batteries with a BMS stop charging at a low temperature? If so, maybe that's one
to put in the glider.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
The BMS is being used for exactly what it is designed for: preventing over-voltage charging. Any question about recovering from an over-charge condition should be directed at the battery manufacturer, not speculated on. Additionally, the solar panel isn't charging the battery at all in flight, so this would only be an issue on the ground. My position is don't bother with the panels, they just don't contribute that much.

Tom

cold weather, I have charged LFP batteries for years in cold hangar (often below zero at night) without any problems. Solar panels do not charge batteries, unless your glider is on the ground with all devices off.

I have 100k glider with 2k solar panels, I still have 100 bucks left for solar panel controller.

On Friday, January 1, 2021 at 8:47:15 AM UTC-8, jfitch wrote:
Most of the industry doesn't agree with you, but I expect you're used to that situation. The BMS is usually regarded as a safety device, the controller of last resort, to prevent fault conditions. What you propose is kind of like using the over current circuit breaker as the limit stop on your motor jack. Run 'er 'till she trips. Yeah it works, but not the best way. There is little downside in having a proper charge controller, and much potential downside in leaving it out.
On Thursday, December 31, 2020 at 6:19:20 PM UTC-8, 2G wrote:
On Thursday, December 31, 2020 at 4:08:21 PM UTC-8, jfitch wrote:
Using the BMS to control charging is not considered good engineering practice. The BMS may or may not be designed to operate that way, but once it disconnects the power bus driven by the solar will be at uncontrolled and possibly damaging voltage. Also, different designs of BMS reset (and reconnect) in different ways, and maybe not how you expected.
On Thursday, December 31, 2020 at 3:25:05 PM UTC-8, Eric Greenwell wrote:
Moshe Braner wrote on 12/31/2020 11:12 AM:
On 12/31/2020 12:50 PM, kinsell wrote:

Might want to be careful there. LFP's can be badly damaged when charging under cold conditions.

Good point. "Cold" as in "below freezing" (0C, 32F) for charging, not discharging. It seems
like an arbitrary number (these batteries are not made of water after all) but that's what they
say. I'd recommend at least several degrees above that for charging. If heading into the wave
with an LFP battery, if you have solar charging, you may want to disconnect that (unless the
charge controller does that automatically - do the LFP-aware ones do that?). Would need a
switch for that disconnection. Otherwise it's another reason to avoid solar panels in the
glider, which can't help a lot with the battery running time anyway.
Do some LiFe batteries with a BMS stop charging at a low temperature? If so, maybe that's one
to put in the glider.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
The BMS is being used for exactly what it is designed for: preventing over-voltage charging. Any question about recovering from an over-charge condition should be directed at the battery manufacturer, not speculated on. Additionally, the solar panel isn't charging the battery at all in flight, so this would only be an issue on the ground. My position is don't bother with the panels, they just don't contribute that much.

Tom

The recommendation WAS intended as the course of last resort if an appropriate solar charge controller was unavailable.

Tom

https://airbatt.de/navi.php?a=9114&lang=eng

On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
https://airbatt.de/navi.php?a=9114&lang=eng

Unfortunately they don't ship to countries outside of Europe.

Tom

On 1/4/21 2:22 PM, 2G wrote:
On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
https://airbatt.de/navi.php?a=9114&lang=eng

Unfortunately they don't ship to countries outside of Europe.

Tom

I have one of these:
https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

--
Dan
5J

On Monday, January 4, 2021 at 3:32:11 PM UTC-8, Dan Marotta wrote:
On 1/4/21 2:22 PM, 2G wrote:
On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
https://airbatt.de/navi.php?a=9114&lang=eng

Unfortunately they don't ship to countries outside of Europe.

Tom

I have one of these:
https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

--
Dan
5J
Besides been quite large and unavailable, it is not for use with LFP batteries.

Tom

On Monday, 4 January 2021 at 23:22:14 UTC+2, 2G wrote:
On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
https://airbatt.de/navi.php?a=9114&lang=eng

Unfortunately they don't ship to countries outside of Europe.

Tom

Well that's not a problem for me, but I don't buy anything from AIRBATT. They sold me a crap chinese LFP battery rebadged with AIRBATT-sticker, which then died after a year of use (BMS failure, unrepairable). First they tried to charge me for checking the battery, after sending it back at my expense. Then they told my that their battery warranty policy follows basically the same EU regulation as warranty for a banana bought from grocery store, and effectively told me to **** off. At a same time local car parts store gives 5 years no-hassle warranty to their cheapest made-in-poland car battery..

On 1/4/21 6:35 PM, 2G wrote:
On Monday, January 4, 2021 at 3:32:11 PM UTC-8, Dan Marotta wrote:
On 1/4/21 2:22 PM, 2G wrote:
On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
https://airbatt.de/navi.php?a=9114&lang=eng

Unfortunately they don't ship to countries outside of Europe.

Tom

I have one of these:
https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

--
Dan
5J
Besides been quite large and unavailable, it is not for use with LFP batteries.

Tom


Oops, I thought the thread was about charge controllers, not about the
batteries they're charging.

There ARE MPPT chargers suitable for LiFePO4, however. They do cost
quite a bit more but they deliver a higher percentage of the energy to
the batteries.

--
Dan
5J