10-28-2018, 10:01 PM | #21 |
Gone Wild
Join Date: Jan 2013
Location: Saint Petersburg, FL
Posts: 2,089
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Re: DIY Lithium Conversion
So for connecting my wires I needed to tap into the middle of the pack. There are electrical connections at each end, but that's not the voltage I was looking for.
I found a clamp made of copper at Home Depot that I think is for a large grounding cable. I inserted the welding cable into the connector and screwed it in tight, then soldered it. Before going on, if you are doing anything like this remember each and every silver tab at the top of the battery is live. Something as simple as tossing a towel over the pack can be invaluable in the case you accidentally drop a wrench. to connect to the middle of the pack I first covered the pack with a towel, then covered the nearest cell tabs with electrical tape. The cell I needed to tap was left exposed. I used a long, small drill bit to do a starter hole in the tab, then went to 1/4. The connection is actually great, I've done some hard runs on the cart and checked the pack, no heat buildup in the cables or the connection. Also you'll notice in the second pick that the pack is wedged in with wood from the drivers side so there's no left/right movement. The size is perfect to prevent front/back movement. To prevent the pack from flying up I took a 3/8ths rod and bent it so on the driver side it just has an L that comes down beside the frame and on the passenger side it has a C that wraps around the frame. The rod sits in a groove on the side of the battery and there is a tab I made in the middle that holds the rod secure. The battery isn't going anywhere. |
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10-28-2018, 10:16 PM | #22 |
Gone Wild
Join Date: Jan 2013
Location: Saint Petersburg, FL
Posts: 2,089
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Re: DIY Lithium Conversion
Here's another pic of the 3/8th rod and electrical connection mid-pack with the cover off. In this pick the 12v wires to the fuse block are not connected yet.
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10-28-2018, 10:25 PM | #23 |
Gone Wild
Join Date: Jan 2013
Location: Saint Petersburg, FL
Posts: 2,089
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Re: DIY Lithium Conversion
So earlier I mentioned I have 4 cells left that I am using for the accessory 12v source. My 12V charger likes to charge to almost 15V. If I used 3 cells that would very much over charge the cells. Supposedly this chemistry won't catch fire at 4.5vpc (well above the 100% charge) but I do not want to try that. So using 4 cells means I can easily use the normal 12v charger I just need to be cognizant that I need to not let my accessory pack go below 12V as that would be 3.0vpc. With my LED lights I rarely need to charge the 12V battery, it won't lose 0.02vpc in a month.
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10-28-2018, 10:47 PM | #24 |
Gone Wild
Join Date: Oct 2012
Location: Southwestern Pa.
Posts: 6,215
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Re: DIY Lithium Conversion
bronsonj, Your battery hold down bar is certainly interesting. Simple, yet it looks (as you said) like those batts aren't going anywhere.
All of my accessories, lights, cig lighter, front and rear winch(s), are already wired to a 12-V marine battery and they all work fine. In my case....if it ain't broke, I'm not gonna fix it. I have always done a separate charge on that 12-V with a regular 12-V auto charger. |
10-29-2018, 08:23 AM | #25 |
Gone Wild
Join Date: Jan 2013
Location: Saint Petersburg, FL
Posts: 2,089
|
Re: DIY Lithium Conversion
DaveTM, did you put in an external port to do your 12v charging? Right now the only charging I need to lift the seat for is the 12v. I've considered many options but haven't found a port connection I like. Specifically, I want a port that someone else wouldn't confuse for a different type of electrical connection.
Did you have any luck with that or do you still lift the seat to charge your 12v? |
10-29-2018, 08:36 AM | #26 |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: DIY Lithium Conversion
I use my 12 volt power jack (cigarette lighter). It's the only 12 volt accessory that isn't switched.
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10-29-2018, 08:59 AM | #27 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,192
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Re: DIY Lithium Conversion
I much prefer top balancing. That is the only way to get the pack fully charged without overcharging some cells. I pick a very safe minimum voltage for my pack and I only charge to 4.1V per cell. I made my own BMS and balancing circuits and they work very well after a couple iterations on the design.
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10-29-2018, 09:35 AM | #28 |
Gone Wild
Join Date: Jan 2013
Location: Saint Petersburg, FL
Posts: 2,089
|
Re: DIY Lithium Conversion
I teased earlier about the easiest 36v conversion.
My buddy has a 36v Taylor Dunn cart he bought from military surplus (A beast of a machine). He replaced the batteries at the time, but that's several years ago and the batteries are tired now. His cart has an onboard charger as well. Going on the assumption that the controller should be able to handle whatever finish voltage the charger produced we decided to use the FLA charger to charge a lithium pack. I've heard that a 36v pack can reach 45ish volts under charge. So we took a 48V lithium pack, put it in his cart and his charger pushed it to 44.0v and cutoff. The extra voltage really gave his cart a performance boost and the lithium pack in his cart is good from the max V his charger will produce (44v, 3.66vpc) down to 36V (3.0vpc) cutoff. This means his analog needle-type battery gauge still functions for telling him if his cart needs charged and no cart hardware needs to change. He does need to upgrade to digital gauge eventually. This was done out of pure convenience... The 12 cells as a unit have nice and easy electrical connections on either end and fit nicely in his battery tray. If we made his pack 11 cells instead of 12, it would still take his full charge to 44v (4.0vpc) but it could discharge lower to 33V (3.0vpc) and would possibly have more usable watt hours, but that requires tapping into the pack at the 11th cell and leave the 12th cell unused. We may still do this at some point, but for now he's really enjoying the cart as it sits. The danger here is if he draws the pack V too low. That isn't really a concern for his short distance driving but we will have to address that in the future. Lastly, for his cart there is no alternate 12v lithium power source so he'll have to reuse two of his 6V batteries to power lights or use a separate 12v battery. He was tapped into two 6v from his pack before. |
10-29-2018, 09:40 AM | #29 |
Gone Wild
Join Date: Jan 2013
Location: Saint Petersburg, FL
Posts: 2,089
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Re: DIY Lithium Conversion
Yurtle, good idea on using the cig lighter! I may steal that idea.
Volt_Ampere, thanks for the input on top balancing. My cells are within 0.01v of each other now but I will need to balance them at some point as I assume they will drift. I bought a Chargery BMS but haven't installed that yet. I had it installed at one point but didn't like the install I did so it's awaiting more time from me to get it right. |
10-29-2018, 09:48 AM | #30 |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: DIY Lithium Conversion
Mine's not a true "cigarette lighter". Lighters have a bimetallic strip, which grabs the lighter when cool, and releases it when hot. Mine's just a power port, rated for 30 amps.
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