04-29-2021, 07:18 AM | #471 |
Gone Wild
Join Date: Oct 2019
Posts: 646
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
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04-29-2021, 07:28 AM | #472 | |
Gone Wild
Join Date: Oct 2019
Posts: 646
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
Quote:
I'd add that of course a "good bms" can fail too. A few threads here detailing issues with Chargery and Zeva (which aren't on your list, but many use them as such). Maybe it is less often, I just don't know. I started out intending to build a Leaf pack, bought a "pretty good" BMS and other parts already before deciding for my use It made more sense to me safety and otherwise (new -vs- used cells etc) to go LifePo4 inside a steel box, so sold the parts I'd already bought. More than one way to skin a cat, that's for sure. Some inventive folks on this forum have come up with great solutions to all kinds of things. |
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05-22-2021, 01:08 PM | #473 |
Getting Wild
Join Date: Dec 2018
Location: Music City USA
Posts: 149
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
Well I have been a way from the boards for a while. My system worked great until last weekend. I went for a ride and right before I got back home the BMS cut out for LV. I was basically in front of the house so no big deal, I pushed and coasted back to the garage. I plugged it in and checked it later that night and it would not charge beyond 47 volts. I checked the charger was putting 56.7 volts. I figured something was wrong with BMS or relays but I had to leave it until this weekend. I thought I left everything unplugged but there must have been some kind of parasitic drain because the batteries are down to 39V. Yikes.
I tired to connect the charger directly to the main positive and negative lead from the battery pack but it will not charge. When not underload it puts out 56.7v but as soon as I connect it to the pack it will not charge. So BMS may be good but the charger may be bad. I am leaving town for 2 weeks. What is the safest way for me to deal with this? I pretty can accept the pack is a loss but how should I leave it while I am gone? Thanks for any thoughts you may have. |
05-22-2021, 01:35 PM | #474 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,193
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
What are your individual cell voltages?
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05-22-2021, 03:24 PM | #475 |
Getting Wild
Join Date: Dec 2018
Location: Music City USA
Posts: 149
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
Okay if the BMS is accurate
3 of them are toast for sure, less than 1V. the other are 2.790 or better. I will need to take the box apart and check because the total voltage with the meter and the BMS are 10V a part. Still a problem. I will get back that info by in the morning. Thanks. |
05-22-2021, 05:45 PM | #476 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,193
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
Measure the cell voltages with your multimeter. All are very low but no way they should ever be that different. Mine are always within 10mV (.010V)
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05-22-2021, 09:55 PM | #477 | |
Gone Wild
Join Date: Oct 2019
Posts: 226
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
Quote:
Nothing under 2.75 volts should ever see the inside of your garage or barn again. Buy a higher quality BMS because this one just cost you your battery. This is why I keep telling people to get a quality BMS instead of the cheap Chinese garbage. Get a REC BMS, set your max cell voltage to 4.05 and your cells should last a long time. |
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05-23-2021, 08:04 AM | #478 | |
Gone Wild
Join Date: Oct 2012
Location: Southwestern Pa.
Posts: 6,215
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
Quote:
I have been using a ZEVA BMS for (I'm gonna guess) 3-4 years now with no real issues. (Pouring rain in the monitor....but that dried out and all was good again) at a cost of $500. I don't see the benefit of spending another $500 for a unit that does the same thing. Maybe that's me. |
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05-23-2021, 09:00 AM | #479 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,193
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
My home designed BMS is completely isolated from the pack when the power is off. (either key off or not charging) In addition when I left the cart for months I completely isolated the pack. It was exactly at the same voltage when I returned 5 months later.
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05-23-2021, 09:05 AM | #480 |
Getting Wild
Join Date: Dec 2018
Location: Music City USA
Posts: 149
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Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS
Thanks for all the replies. Here is what I have right now for voltage, all batteries isolated and measured between center taps and then outer taps.
Module 1 2.8v 2.8v 5.6v 2 2.8 2.8 5.6 3 2.9 2.9 5.8 4 2.9 2.9 5.9 5 2.8 2.8 5.6 6 2.8 2.8 5.6 7 2.8 2.8 5.6 I think I may have avoided disaster but clearly the BMS is not functioning. I will worry about that replacement after vacation. For now I am going to replace the bus bars and try to attach my charger to the main pack negative and positive and see if I can get it to charge. If not, do you guys think this pack will sit okay for the next two weeks until I can figure out how to get it charging? Thanks again for all the helpful replies. |
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