Interested in the trolling motor side of things if get into fishing from the sib.
Unfortunately can only lay my hands on regular 9amp sealed acid which then becomes an issue with size and weight to power ratio.
Are these ex laptop or security batteries?
In real world use how would you compare this to traditional 4 stroke outboard hp power wise?
The Battery Managment System ( think "safety board" ) has just been disabled, while the cells inside are perfectly good. I found less than 5% of cells failed.
Quote:
Originally Posted by ShinyShoe
How are you charging?
I use a simple IMAXB6 hobby charger .
I bought it used for $15 , but they retail for $30.
Have you wired up all those cells so they can be balance charged properly? Those hobby chargers only had a balance connector for up to 4 (or was it 6?) cells at a time - have you done some clever wiring to get around that? Have you installed a BMS to avoid over discharge?
My concern would be that you wouldn't want someone who doesn't understand how battery cells work and the difference between the chemistries putting a pack of old, semi depleted and of a wide range of quality incendiary devices into a boat and toddling off for the day.
Much of the responsibility of the BMS is to prevent the rogue cells from overheating on discharge. This is how EV cars get away with avoiding hugely expensive cell grading and instead can just dump in all the cells they buy from the manufacturer regardless of their range of quality. It's what Tesla got a bit wrong in the early days of using Panasonic cells as the Panasonic factory that was set up on the US site wasn't running very well and quite a few duff cells were going through that then caused some car issues until they reworked the BMS. In the U.K. our Tesla's now import from China and have a Chinese sourced battery pack which I can't say is terribly reassuring. Chinese build quality and honesty combining with US hucksterism at its finest can't be that great a recipe for a car not burning your house down.
Obviously with used batteries there can be a pretty wide range of cell abilities and we all know how hot just a few of those cells get in our laptops so it's going to be a bit of a lottery as to whether a depleted one gets packed into the centre where it can not just overheat without being able to dissipate but also be heated by its neighbours while not having any form of pack cooling system.
Typically these old cells get used for remote power/grid storage where they can burn and do no lethal harm. But if they get used for domestic service like solar storage then you need to make sure they've been graded and have a good BMS to manage over heating.
The risk of someone putting their own pack together like we used to with radio controlled cars is that they might not do the grading that is very important if there isn't going to be a BMS, may not appreciate the heat risk from the sealed storage so put too much draw on the pack.
It's a great project but I'd suggest only for those who know exactly what they're doing as a lithium fire on a rubber dinghy is probably as desirable as one on a plane and those cells were all graded and controlled their discharge via a BMS.
One thing I would add re your pack is that Li cells are notorious for depleting slowly and then holding a threshold before capitulating rapidly. We tend to see it with our old phones in that they will show a high percentage all day, hang around the 50% mark and then just collapse and the system shut down before the cell is fully depleted. Is it worth testing in a bucket just how much usable juice you have after 50% as it may well be nowhere near 50%. Old Li cells tend to operate at the front end of the use just like they used to when fresh but the big loss is further along the depletion curve.
I think this is a great project & hats off to 909 for sharing. It’s not for everyone, but as long as you have the required skills & knowledge, projects like this can be very rewarding.
Thanks for sharing.
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Absolutely. Even then, the range of quality between a batch of cells tends to be very wide and one little turd from the factory and it buggers you're pack.
Well worth self grading each cell to ensure they're all pretty uniform in quality. Especially as some factories are turning out produce with really, really low quality control.
At one point when Panasonic, who make excellent cells, set up on US soil under Tesla, up to 25% of their output was junk.
The space industries shows very clearly that there is no need for a BMS if you grade all the cells and ensure uniformity.
Very interesting thread. 4 years ago I built a battery for my ebike using 42 brand new genuine Samsung 18650 30Q cells and a BMS. I configured it as 14S3P to give a max power output of 58.8 volts and 9ah. I made sure that all cells were balanced before assembly. According to my ebike dash I'm getting 1750w at full throttle
After 4 years it is still performing perfectly with no incidents.
During initial experimentation I built a pack using 25R cells. I spot welded these together with zinc plated steel (bought as pure zinc) and was not happy with the result, so took it apart with the intention of using copper connectors. During disassembly I inadvertantly shorted 2 cells! OMG, when these things go into thermal runaway it's seriously scary. That gave me huge respect for them. I managed to save half of the cells and have been using them since in my vapes.
After failing miserably at spot welding copper I designed and built a 'no solder/no spot welded' pack using compression. If anyone is interested I'll dig out some pics and post here.
Absolutely. Even then, the range of quality between a batch of cells tends to be very wide and one little turd from the factory and it buggers you're pack.
Well worth self grading each cell to ensure they're all pretty uniform in quality. Especially as some factories are turning out produce with really, really low quality control.
At one point when Panasonic, who make excellent cells, set up on US soil under Tesla, up to 25% of their output was junk.
The space industries shows very clearly that there is no need for a BMS if you grade all the cells and ensure uniformity.
Plus, it's a fun way to spend a weekend!!!
A weekend? You're having a laugh It took me months to figure it out, and even then I'm not totally sure I got it right
BLACK PIG
Piglet
It took me months to figure it out, and even then I'm not totally sure I got it right
