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Hello from Alabama
#1
New here, been lurking for a while and figured I should register and say hello.

My applications on batteries is very basic, I am restoring several vintage Garden tractors and I am looking to replace the lead acid batteries with my own built li-ion packs. I have 5-6 tractors so my plan is to just take the pack to the tractors when needed and I only need 1-2 packs as they will never all be run at the same time. I am tired of trickle charging through the winter when I can use the packs in the winter for other projects.

I already have a source of used batteries and I am starting to do my first charging and testing on the first 30-60 cells (18650). Not even sure how many but they are free so who's countingSmile

Most everything I have figured out, looking through the site now to learn more on the BMS boards used. 


Where I am confused about is how the system will work when the charging output of the tractor will only be about 13.8V, current not sure of yet. Not worried about it charging the battery as that can be done at night. But will have to determine the cranking loads and make sure it can at least crank it for a days work.

Oh almost forgot, I am building an electric riding mower. Got the motor mounted and test running on 2-24V power tool batteries. So will be building two packs for it. One for power and the other for the blades which will be driven by a separate battery. Might be a good one to post in the project forum, might give me the incentive to finish it.

Here is a video, just remember this was a test. Wasn't worried about being neat on the wiringSmile.. 

Well, video will be in next post as it requires me to post one time before using URL's...



BTw.. Name is Randy 

Here is the video of the riding mower conversion.

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#2
Hello,
The thougths that come to mind are :
1. Starting current spike (the pack would need to deliver a fair current to start - unless they are old hand crank !)
2. "when the charging output of the tractor will only be about 13.8V" - what voltage would the starter be getting from the battery pack ?
3. Start current should bypass the BMS..... and allow a smaller Amp rated BMS to be used.
4. Charge via a buck/boost converter from the alternator (dyanamo if it is older ?) which is then current limited.

Free cells - way to go, build a pack large enough to run a kettle and your done. Tractor running and a cup of tea !
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#3
A youtube by @jehugarcia titled "4000A BMS?" https://youtu.be/J2KH21Fwi9o shows a technique to use a cheap BMS to toggle a contactor (400amps) for high current instead of trying to buy / bypass a BMS that is capable of high amps. Looked like a good technique and might apply in this case.
Headrc likes this post
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#4
(08-10-2019, 01:53 PM)completelycharged Wrote: Hello,
The thougths that come to mind are :
1. Starting current spike (the pack would need to deliver a fair current to start - unless they are old hand crank !)
2. "when the charging output of the tractor will only be about 13.8V" - what voltage would the starter be getting from the battery pack ?
3. Start current should bypass the BMS..... and allow a smaller Amp rated BMS to be used.
4. Charge via a buck/boost converter from the alternator (dyanamo if it is older ?) which is then current limited.

Free cells - way to go, build a pack large enough to run a kettle and your done. Tractor running and a cup of tea !

I have not had a chance to determine the starting current spike, but I use a li-ion starting pack for a car to start my tractors now, the lead acid is not enough to crank them but is enough to keep them running (lights, ect). 

Max voltage on the starter would be 16.8 volts from a fully charged pack, that should be OK however I will check the specs if I can find them or test on a older starter. These are Briggs and kohler 10-20hp engines, so a small lawn tractor battery is the equivalent. The extra voltage may give that initial faster spin to crank. They have to be spun at a certain RPM to bypass certain features.

Not sure about #3&4 will have to do some more searching on the site for that. Now that I think about it the starter is not the issue but the coil/condenser and points would be the issue. Not sure how the higher voltage would effect them. Maybe I need to look at a circuit that would do what I am doing now, use the battery to jump and disconnect it. 

Thanks for making me think moreSmileill post later in the Projects forum just so more eyes will see it. Probably not as many people look at the introduction section.

I have a close friend who works as a copier/PC technician and installs security systems. He has talked the owner into letting me have the discards and use and then I will properly dispose of the dead cells. Saves him the hassle.

(08-10-2019, 03:07 PM)OffGridInTheCity Wrote: A youtube by @jehugarcia titled "4000A BMS?"  https://youtu.be/J2KH21Fwi9o  shows a technique to use a cheap BMS to toggle a contactor (400amps) for high current instead of trying to buy / bypass a BMS that is capable of high amps.  Looked like a good technique and might apply in this case.

I saw his video last night after I posted, but fell asleep.. hmm.. That didn't sound good. I meant I was already tired and will watch it again when I can pay attentionSmile.

I have a Schumacher booster pack and I accidentally moved the toggle switch from 6A start/charge to 300A boost. I blew 3 solenoids before I realized the toggle switch could move to the higher boost setting.  So I know 300A will blow the solenoids for sure. I would not want to run more than a few amps MAX  through these solenoids. I also will never design something with a toggle switch where it can be changed without first turning the unit off.
 

Cheap BMS I haveSmile
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Sean (08-10-2019, 09:07 AM), Tonka (08-13-2019, 05:18 AM), dewki (08-12-2019, 07:37 PM), Magnum164 (08-11-2019, 02:26 AM), ben teker (08-10-2019, 09:36 PM), OffGridInTheCity (08-10-2019, 07:08 PM), ajw22 (08-10-2019, 09:07 PM), Solardad (08-10-2019, 10:40 AM), Generic (08-11-2019, 03:11 AM), Wolf (08-10-2019, 10:35 AM), chuckp (08-10-2019, 11:41 PM), Riplash (08-11-2019, 06:28 AM), completelycharged (08-10-2019, 01:53 PM), Headrc (08-11-2019, 02:36 PM), bogptrsn (08-10-2019, 03:50 PM), Tentious (10-27-2019, 01:30 AM), Geek (08-12-2019, 12:24 AM), is0lated (08-19-2019, 10:20 AM)

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