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Old 08-07-2014, 01:20 PM   #11
Chad McCan
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Default Re: Lithium RXV - Talk me out of it

Good info benjylafond... I've read your build posts as well. I started out thinking I wanted the mini-bms system, but the more I think about it, it's really tough. You need it to work when the cart is off (for the charger), but also when the cart is on. That's my original reasoning for buying 2 dc converters. Ideally, my charger is my smart enough to charge the batteries the way they should be and stop when it should. I'll use the ev display to signal when the batts are low and maybe even shut off the cart, if need be.

sportcoupe, is there anything you would do differently as far as ordering your charger? Obviously the charging profile for the Leaf modules is unique, but does it work exactly the way you would expect it to?
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Old 08-07-2014, 05:37 PM   #12
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Default Re: Lithium RXV - Talk me out of it

Quote:
Originally Posted by Chad McCan View Post
sportcoupe, I'm ordering 7 modules initially, but I'm sure I'll end up with 14. I'd like to test 7 around the golf course. 48(ish) volt system. I'd love to get a description, parts list and/or photos of your bottom balancing rig. I assume I need a voltmeter, maybe with a trigger to a load? And this takes about 3 days???

cgtech - What size fuse/breaker? Just put it inline from the battery to the solenoid?
If you install 7 Leaf modules in series you will have 59v fully charged possibly frying your stock RXV controller.

You need a very special voltmeter to control the bottom balancing. It has to have a couple of programmable contacts inside it. Read this link. I used it to balance mine. No way you can do it in 3 days either even if you cheated and balanced all modules at the same time in parallel. If you do one at a time it's about a month. I didn't want to wait that long. It still took me over a week.
http://st1100ev.blogspot.com/2012/09...balancing.html
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Old 08-07-2014, 05:41 PM   #13
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Default Re: Lithium RXV - Talk me out of it

Quote:
Originally Posted by Chad McCan View Post
Good info benjylafond... I've read your build posts as well. I started out thinking I wanted the mini-bms system, but the more I think about it, it's really tough. You need it to work when the cart is off (for the charger), but also when the cart is on. That's my original reasoning for buying 2 dc converters. Ideally, my charger is my smart enough to charge the batteries the way they should be and stop when it should. I'll use the ev display to signal when the batts are low and maybe even shut off the cart, if need be.

sportcoupe, is there anything you would do differently as far as ordering your charger? Obviously the charging profile for the Leaf modules is unique, but does it work exactly the way you would expect it to?
The charging profile for the Leaf modules isn't very unique. If you don't have a charger with a lithium profile then you must have a BMS to prevent overcharging.

The biggest concern I'd have so far (besides blowing up the garage with an overcharge is if your RXV can handle the 59v of a 7 module pack.
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Old 08-07-2014, 08:40 PM   #14
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Default Re: Lithium RXV - Talk me out of it

If the high voltage of the Leaf module is 8.4v (x7 = 58.8v) and the high voltage of a 12v FLA is 14.4v (x4 = 57.6v) I don't see a problem, unless someone knows that the RXV Danaher controller can't handle the extra 1.2v? 6 modules would suck.

Thanks for the link for bottom balancing.
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Old 08-07-2014, 10:46 PM   #15
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Default Re: Lithium RXV - Talk me out of it

These are specs for max voltages while on charge? Sounds fishy to me. The lead batteries will never be that high, unless on charge (they should hit 58v + really).
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Old 08-07-2014, 11:02 PM   #16
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Default Re: Lithium RXV - Talk me out of it

Another tip, Do Not charge an rxv with a non original charger With the Key ON! (lead or lithium batts) The controller will activate the "burn-off coil" to try to fix what it sees as a high voltage situation. This will prevent the charger from charging, and will create lots of heat in the battery compartment. The controller MAY time-out and shut off after 20 minutes, but i didnt wait to find out. The burn-off coil has one main function. The rxv has no "real" brakes, and all stopping is done by reclaiming power and putting it back into the batteries (minus the heat lost in the controller, motor, axle, ect). If you live on top of a hill, and leave your house with fully charged batteries (fresh off the charger), where can the controller put the power generated by braking down the first hill when the batteries are already full? It "wastes" it in the "burn-off coil". In case you dont know what this "burn-off coil" is, its right behind the controller, wrapped around a ceramic spool.
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Old 08-08-2014, 04:05 AM   #17
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Default Re: Lithium RXV - Talk me out of it

Chad, I had forgot that the RXV was 48v. Never had one so I don't know it's particulars.
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Old 08-08-2014, 08:37 AM   #18
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Default Re: Lithium RXV - Talk me out of it

cgtech - Correct, these are peak charge voltages. The cells will settle at a little less than that. My point was, that's the highest the cart should EVER see, under worst case scenario.

Really good to know, about the burn off coil. I noticed the EZGO charge has a 3rd conductor. Seems like it would make sense for that to just turn off the solenoid, so the controller never sees the charger.

sportcoupe, do we agree then that 7 modules is the correct number? I'm leaning on you as much as anyone :) Bottom balancing for a month sounds wack. Starting to sound like a winter project.
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Old 08-08-2014, 09:44 AM   #19
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Default Re: Lithium RXV - Talk me out of it

7 modules in series will in fact net you a 59v fully charged 60Ah pack. Recharge by 50.3v.

I went with 14 modules to make a 120Ah pack for more range. With only 7 modules it won't take a month, a couple weeks yes if you do them one by one.
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Old 08-08-2014, 11:31 AM   #20
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Default Re: Lithium RXV - Talk me out of it

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