ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

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Jaysen
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by Jaysen » Wed Sep 18, 2019 9:50 am

Couple hundred ohms of high watt resistance and a volt/ammeter. Any that you lost will work. I recommend an ammeter and potentiometer in-series to monitor draw and a voltage monitoring relay set for the desired drop voltage. That will let you set the draw rate and walk away.

Remember that I higher ohm resistance will lengthen the draw down which will prevent heat issues. Add that really and you can leave it unattended once set. (I would but you make be smarter than me)


Jaysen wrote:
Mon Apr 29, 2019 3:44 pm
I tried to say something but God thought I was wrong and filled my mouth with saltwater. I kept my pie hole shut after that.

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glossieblack
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by glossieblack » Thu Sep 19, 2019 4:45 am

Thanks Jaysen! :D

As a result of your welcome advice, this morning I went to the local auto and marine electrician I've been dealing with for nearly 40 years, and asked if I could borrow the necessary equipment.

F**k that, he replied, on the way to work tomorrow, he'll drop by to safely dissipate the 48V battery bank down to 20% of full capacity.

How? He's going to use an old fashioned battery testing unit he still has based on the introduction of high resistance loading. He'll be watching his readouts like a hawk.

And I'll be watching Skinnydip's smart 48V battery monitor readouts - volts, amps, watts, amp hours, % of battery energy left etc.

Gotta love this forum, the way generous members like Jaysen provide information that guide you towards productive tracks. :D
Completed R13 two part nesting rowboat. ST 21 under construction .... where seeking perfection is recognized as the enemy of the good.

Jaysen
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by Jaysen » Thu Sep 19, 2019 6:09 am

Ha! Figured you’d “have a guy” with the expensive version.
Jaysen wrote:
Mon Apr 29, 2019 3:44 pm
I tried to say something but God thought I was wrong and filled my mouth with saltwater. I kept my pie hole shut after that.

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icelikkilinc
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by icelikkilinc » Thu Sep 19, 2019 7:18 am

glossieblack wrote:
Thu Sep 19, 2019 4:45 am

F**k that
you gotta love the pros :lol: :lol:
Ilker

TW28 launch: viewtopic.php?f=12&t=23369

Jeff
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by Jeff » Thu Sep 19, 2019 7:34 am

Nice GB!!!! Jeff

Fuzz
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by Fuzz » Thu Sep 19, 2019 2:36 pm

Great news on two fronts! You will get your battery problem taken care of and now I know that boy is handy for something :lol:

Jaysen
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by Jaysen » Thu Sep 19, 2019 3:01 pm

Hey! I resemble that remark!
Jaysen wrote:
Mon Apr 29, 2019 3:44 pm
I tried to say something but God thought I was wrong and filled my mouth with saltwater. I kept my pie hole shut after that.

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glossieblack
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by glossieblack » Fri Sep 20, 2019 6:19 am

Thanks for the interest and laughs Jaysen, Ilker, Jeff, Fuzz, and Jaysen again. :D

My marine electrician mate took but a few minutes to dissipate the 48V lithium ion battery bank down to 20% capacity.


I then recharged it upwards using the 48V smart charger.

As the % built (approx. 30%, 40%, 50% etc), I measured the voltage of each of the 16 cells. Unfortunately they had slightly different voltages at each % point, with this pattern continuing all the way up. I'd been hoping that the differences would be smoothed out.

When the differences were still apparent at approx. 80% of full capacity, I decided I needed to dissipate each individual cell down to a common voltage level.

After some experimentation, I ended up cobbling together a dissipation unit using a bilge blower rheostat with dissipative heat coils, as per pic.

This was applied across the terminals of each the sixteen 3.2V lithium ion cells to run each down to a common voltage.

The multimeter was used to track each cell's journey down.

Image
Completed R13 two part nesting rowboat. ST 21 under construction .... where seeking perfection is recognized as the enemy of the good.

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OrangeQuest
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by OrangeQuest » Fri Sep 20, 2019 6:35 am

I am curious as to how smart your smart charger is. The Lithium ion battery packs used in R/C stuff also use multi cells, but the chargers plug into each cell and the little smart chargers then will apply voltage to each cell to balance them all out for a very even charge. The smaller pigtail plugs into the charger to monitor each cell.
5451

We use 4 smart (R/C) chargers to keep the batteries charged on our R/C sailboats. Really good chargers will more than double the battery life.

The batteries we use are only "AA" size but they work on the same principal.

Should look like this
5452
"that it isn't just an ordinary sort of boat. Sometimes it's a Boat, and sometimes it's more of an Accident. It all depends." "Depends on what?" "On whether I'm on the top of it or underneath it."
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glossieblack
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Re: ST21 Hybrid Powered "SKINNYDIP" Noosa Australia

Post by glossieblack » Sat Sep 21, 2019 3:35 am

OrangeQuest wrote:
Fri Sep 20, 2019 6:35 am
I am curious as to how smart your smart charger is. The Lithium ion battery packs used in R/C stuff also use multi cells, but the chargers plug into each cell and the little smart chargers then will apply voltage to each cell to balance them all out for a very even charge.
Thanks OQ, I like the way you can charge each cell individually. I can only charge the battery bank in total - i.e. 16 x 3.2 volts.

My only previous experience in charging a multiple battery bank has been with arrays of AGM or lead acid batteries in series. A single charger only needs to charge the whole bank. Equalization of each cell can be achieved by giving the whole bank a high voltage blast every now and again.

In Skinnydip, the ability to recharge the 48V battery bank as a single entity is part of the hybrid drive system - when she's being driven by diesel engine, the e-drive motor can be used as a 48V generator to recharge the battery bank.

I now realise I need to do my homework more thoroughly on my 3.2V x 16 cell lithium ion battery bank. Does it matter if individual cells have slightly different charges, so long as the battery monitoring system shuts the whole bank down if programmed safe operating parameters are exceeded?
Completed R13 two part nesting rowboat. ST 21 under construction .... where seeking perfection is recognized as the enemy of the good.

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