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Old 12-05-2023, 09:38 PM   #21
InvalidUsername
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Default Re: upgrade to Lithium, how many AMPS do I need?

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Originally Posted by augiedoggy View Post
You know multiple 48v golf cart batteries that fit in regular 6 or 8 spaces are sold for this right? Most people just remove the plastic liners and install larger batteries though. If it's working for you and you have a 12v charger to rebalance them as they drift and otherwise shorten the battery life then your good. Many of the cheap solar rc battery warranty are trash and don't mean much when you need them.. just read the Facebook reviews to see this.
No 48V battery is going to fit in my CC battery compartment without a major renovation. The controller is mounted on a vertically oriented metal plate that divides the battery compartment in half. Why would I want to go to the trouble of ripping out the molded tray and finding a way to remount and rewire the controller, solenoid and OBC just so that I could use a 48V battery? 4 12Vs will do the same job, although not as perfectly as some people would like. I understand and accept their sentiment and I also accept the trade off of using 12V batteries. Life ain't perfect.

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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Old 12-05-2023, 10:17 PM   #22
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Default Re: upgrade to Lithium, how many AMPS do I need?

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Never? What about when you don't have any other option due to a 48V battery not being able to fit? Or don't want to ruin your back by lifting 100 lbs when bent over and off balance? I have a 5 year warranty on 4 12V LiFePO4 batteries that cost a little bit more than 4 LA batteries. I seriously doubt I could buy LA batteries with a 5-year warranty. And being able to lift out a battery with one hand is such a relief and a blessing
Correct, NEVER! 12v lithium in series is more trouble than it's worth.

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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Old 12-05-2023, 10:35 PM   #23
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Default Re: upgrade to Lithium, how many AMPS do I need?

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Correct, NEVER! 12v lithium in series is more trouble than it's worth.
Please explain how they are more trouble than LA batteries.
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Old 12-05-2023, 11:06 PM   #24
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Default Re: upgrade to Lithium, how many AMPS do I need?

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Please explain how they are more trouble than LA batteries.
There's a big difference between LA and Lithium 12v batteries as explained below. There are absolutely no pro's in going with 12v series connected lithium batteries in high current discharge use, as in a Cart. Firstly they are not designed for that. They are designed for standby power in solar, RV and UPS marine applications and as such cannot reliably provide the current required.

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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Old 12-06-2023, 07:34 AM   #25
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Default 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.
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Old 12-06-2023, 07:37 AM   #26
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Default Re: upgrade to Lithium, how many AMPS do I need?

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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 series with none of the issues detailed above with the 12v series. You can run up to 10 of these in series 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.
Correction…..Parallel.
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Old 12-06-2023, 07:56 AM   #27
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Default 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.
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Old 12-06-2023, 08:05 AM   #28
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Default 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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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.
I don't understand how the remaining batteries will no longer charge once the first reaches 100% and disconnects them from charging, yet they are catching up after the 1st reaches 100%, which suggests they are still charging. Or are you saying that the remaining 3 will never reach 100%. If that's the case then why are my batteries at the exact same voltage after being recharged? Or are you referring to AH capacity rather than voltage?
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Old 12-06-2023, 08:33 AM   #29
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Default Re: upgrade to Lithium, how many AMPS do I need?

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Correction…..Parallel.
Damnn iiitt I do this every time! lol
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Old 12-06-2023, 08:38 AM   #30
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Default Re: upgrade to Lithium, how many AMPS do I need?

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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.



I don't understand how the remaining batteries will no longer charge once the first reaches 100% and disconnects them from charging, yet they are catching up after the 1st reaches 100%, which suggests they are still charging. Or are you saying that the remaining 3 will never reach 100%. If that's the case then why are my batteries at the exact same voltage after being recharged? Or are you referring to AH capacity rather than voltage?
Your understanding is correct in that they will not all reach full charge. With Lithium the voltage drop is vastly less than FLA. So a .5v deference is massive compared to FLA. As he explained further up the imbalance will start small but will grow quickly over time to resulting in the down stream batteries being at a much lower SOC in a fairly quick fashion. This obviously will be exacerbated if you run accessories without a reducer as well.
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