12-05-2023, 09:38 PM | #21 | |
Gone Wild
Join Date: Nov 2023
Posts: 1,716
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Re: upgrade to Lithium, how many AMPS do I need?
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As I understand it charging each 12V battery separately is not required to balance them. Simply connecting them in parallel for a period will do the same. Do you have an opinion on how often they should be balanced? I'm sure you're right about many of the warranties being trash, but that doesn't necessarily mean all of them are. |
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12-05-2023, 10:17 PM | #22 | |
Gone Wild
Join Date: Dec 2020
Location: Melbourne, Australia
Posts: 2,064
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Re: upgrade to Lithium, how many AMPS do I need?
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As Augiedoggie said, you can get small footprint 48v 30Ah batteries that fit in a standard 8v LA footprint and you can install multiples of those, 2, 3, 4.. etc. whatever you need to make up the range and discharge capacity you need. But, I stand by my original comment, it's a one time installation, get some help, a lift etc. and do it properly. Eco Battery make kits that will fit pretty much any cart. Once you've installed lithium, you'll never go back to Lead Acid so the battery tray becomes redundant. |
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12-05-2023, 10:35 PM | #23 |
Gone Wild
Join Date: Nov 2023
Posts: 1,716
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Re: upgrade to Lithium, how many AMPS do I need?
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12-05-2023, 11:06 PM | #24 | |
Gone Wild
Join Date: Dec 2020
Location: Melbourne, Australia
Posts: 2,064
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Re: upgrade to Lithium, how many AMPS do I need?
Quote:
Second is keeping the 4 batteries balanced. When it comes to charging series connected batteries there’s a problem with Lithium and that is that as soon as the first battery becomes fully charged it’s BMS will disconnect and the other batteries will no longer charge. You have 4 BMS’s all doing their own thing and not knowing what the other is doing. When charging series connected LA, the battery that gets to 100% first will be overcharged while the others catch up. LA can accept slight overcharging and are essentially top balanced at every full charge. The charge/discharge efficiency of lithium is very high, generally above 92% but typically as high as 97%. Now let’s assume that the charging efficiency of your 4 12v batteries varies between 97% and 98%, a 1% difference. I’ll use round numbers and assume 0% to 100% charge discharge cycles to keep things simple. Battery capacity is 100Ah. You have 4 fully charged batteries with 100Ah each and they are discharged to 0%. Now they’re recharged but because one battery gets to 100% first charging stops and because there’s a 1% difference in charging efficiency, the lowest battery is only at 99%. Your 100Ah pack is now only 99Ah as the pack capacity is only as good as the least charged battery. Now you discharge back to 0%. There’s still 1% left in your highest battery. Charging to 100% again will see the same battery get to 100% first but the lowest battery will now be at 98%. Each discharge/charge cycle will see the pack capacity diminish. Assuming 2 cycles per week, after 6 months (52 cycles) your battery capacity could be down to 70%. It’s not 48% as the lower the pack capacity gets the less loss per cycle. And that’s with 1% difference and not accounting for different discharge efficiencies, only different charge efficiency. The cheaper you go with the batteries the more pronounced this problem will be as cheaper cells will be used in the battery. When a manufacturer states that up to 4 batteries can be connected in series, what they are really saying is that the mosfets being used in the BMS’s have a high enough VDS (drain source voltage) so that they can withstand the voltage of the other three batteries connected in series If/when a BMS trips. They are not saying that they will work optimally, long term in that configuration. |
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12-06-2023, 07:34 AM | #25 |
Gone Wild
Join Date: Sep 2022
Location: Minnesota
Posts: 1,659
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Re: upgrade to Lithium, how many AMPS do I need?
Here is an example of one of the options that are 48v and same foot print as a single 8v FLA.
https://www.epochbatteries.com/produ...ithium-battery You can run these in parallel with none of the issues detailed above with the 12v series. You can run up to 10 of these in parallel although I am sure your limitations for space to hold batteries and available funds for the cart will run out well before you hit that limit. |
12-06-2023, 07:37 AM | #26 | |
Gone Wild
Join Date: Dec 2020
Location: Melbourne, Australia
Posts: 2,064
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Re: upgrade to Lithium, how many AMPS do I need?
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12-06-2023, 07:56 AM | #27 |
Gone Wild
Join Date: Apr 2008
Location: Western NY
Posts: 2,393
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Re: upgrade to Lithium, how many AMPS do I need?
Noco does make a special charger for charging all the batteries individually while they are still wired in a series. I ts a good solution I've read, to the balancing issue.
I'm not trying to give anyone a hard time. I just want to make sure people are aware of the shortcomings of using the rv batteries in a golf cart. Even when they truly can deliver say 100amps output without bms issues, the smaller cells they use will usually be pushed harder than optimum so the battery life will be shortened possibly dramatically vs advertised lifespan (lower current output in a camper or boat situation). All that said it could work fine depending on actual cart and use. |
12-06-2023, 08:05 AM | #28 | |
Gone Wild
Join Date: Nov 2023
Posts: 1,716
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Re: upgrade to Lithium, how many AMPS do I need?
Thanks for the explanation. Makes sense. If this is the case then I'll just have to deal with it because I can't put a 48V battery in my cart and I'm not going back to LA. I've emailed the company with your comments and asked for their response.
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12-06-2023, 08:33 AM | #29 |
Gone Wild
Join Date: Sep 2022
Location: Minnesota
Posts: 1,659
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Re: upgrade to Lithium, how many AMPS do I need?
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12-06-2023, 08:38 AM | #30 | |
Gone Wild
Join Date: Sep 2022
Location: Minnesota
Posts: 1,659
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Re: upgrade to Lithium, how many AMPS do I need?
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