10-12-2020, 07:55 PM | #1 |
Not Yet Wild
Join Date: Mar 2010
Location: Texas
Posts: 17
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Questions on maximum current when using drop in batteries
Hi experts, I am considering converting to lithium drop-in, and would appreciate your advice on calculating the optimal number of batteries.
I have read the many horror stories here of folks having undersized batteries cutting out on them, and don't want to go there... My cart is a stock 2008 Carryall 2 - it is 48volt with 8x 6v batteries, 500amp controller and 3.7hp DC motor - a little beefier than standard golf carts. Allied said I could start with a minimum of 2 ( they recommended 3) of their 48v 30AH drop-in batteries - https://alliedlithium.com/products/a...30ah-batteries - and add more if needed. I asked Allied what the technical specs were on these 48v 30AH batteries (as they are not listed online like their 12v tech specs are) - they said the 48v 30AH battery is 30-45A continuous, 90A (10-100ms) max. Given I have a 500 amp controller, how many batteries would be required to use my cart to it's full potential - will I have to buy 6 of the Allied 48v 30AH batteries (6x90A = 540A) to use my cart without risk of the batteries cutting out? And if I consider Roypow instead, I see their 48v 105AH battery (S51105) has a max current of 200A (10s) - https://www.roypowusa.com/?page_id=26237 - so do I need 3 to use my cart without risk of the batteries cutting out? Thanks and stay safe! |
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10-12-2020, 09:33 PM | #2 |
Gone Wild
Join Date: Apr 2017
Location: SE TN
Posts: 2,217
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Re: Questions on maximum current when using drop in batteries
There are two current ratings on Lithium batteries. One is max continuous discharge current and the second is maximum instantaneous discharge current. Ask Allied what the maximum instantaneous discharge current is. If I'm not mistaken an Alltrax 500A controller will only output 500A for 2 seconds. Then again all that doesn't matter. It all depends on how the BMS is wired and what the setting are or if the discharge path goes through the BMS or bypasses it. What it all boils down to is that you need to take the manufacturers word for what they say it will do.
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10-13-2020, 08:33 AM | #3 |
Not Yet Wild
Join Date: Mar 2010
Location: Texas
Posts: 17
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Re: Questions on maximum current when using drop in batteries
Thank Walter! I have asked Allied to clarify the max current specs they gave me - will let you know when I hear back.
My cart has a Curtis 500A controller - model 1520-5501 - googling around I found "Amature 2 minute current rating (amps): 275". So if one Allied 48v 30AH battery can deliver 30-45A continuous, in theory would I need 7 to 10 of them ideally? Thanks. |
10-13-2020, 11:10 AM | #4 |
Gone Wild
Join Date: Apr 2017
Location: SE TN
Posts: 2,217
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Re: Questions on maximum current when using drop in batteries
No, first of all where would you put 10 batteries? Four should do the job. Where you would run into trouble would be going up hills. And I don't think Texas has too many hills except parts of West Texas
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10-13-2020, 12:40 PM | #5 |
Not Yet Wild
Join Date: Mar 2010
Location: Texas
Posts: 17
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Re: Questions on maximum current when using drop in batteries
Thanks Walter. I heard back from Allied - they clarified the max current specs from earlier:
Max Continuous Discharge Current of a single Allied 48v 30AH battery: 30-45A continuous Max Pulse Discharge Current and duration of a single Allied 48v 30AH battery: 90A (10-100ms) They could not provide a "Max Instantaneous Discharge Current of a single Allied 48v 30AH battery" value for me. Texas does have hills in certain areas - there are times we go uphill with the pedal flat for a few minutes. My concern with using just 4 Allied 48v 30AH batteries (each capable of 30-45amps continuous), is that: At best, they can only supply 180amp (4x 45A) continous, At worst, they can only supply 120amp (4x 30A) continuous, Will this not result in my controller (capable of 275amp for 2 minutes) sucking too much from the 4 batteries during a pedal-flat loaded scenario? Ending up triggering the internal BMS to shut down the batteries? |
10-13-2020, 12:53 PM | #6 |
Gone Wild
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 9,329
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Re: Questions on maximum current when using drop in batteries
The "Max Pulse Discharge Current" rating at 0.1s of duration is a joke and only intended to fool folks that just glance at the specs.
At that maximum output rating of 2 minutes your controller is likely using about half as much current from the battery. If You get a controller with adjustable "Battery Amps" setting like the Alltrax SR model you may get away with 4 batteries that can deliver a continuous 120/180 amps. You should start with 150 amps limit on the battery current and see how the cart performs. That would still give you over 300 amps at the motor to start the cart. |
10-13-2020, 02:45 PM | #7 |
Not Yet Wild
Join Date: Mar 2010
Location: Texas
Posts: 17
|
Re: Questions on maximum current when using drop in batteries
Thanks Sergio! I appreciate your insight.
Replacing my controller with one that throttles current to match a lower battery capability, seems to be a case of fixing the symptom not the cause i.e. I want to be able use the cart's full power capability, so would prefer to increase battery capacity to match the controller and motor requirements. I've come to the realization that it would likely require 6 to 8 Allied 48v 30AH batteries to keep the stock controller fed during a pedal-flat loaded scenario - however it does not make financial sense to do this based on today's pricing of ~$900 per battery. Ditto for RoyPow - I would likely need 2 to 3 S1105's (if that many could fit) - however today at ~$2200 per battery it's too pricey. I guess I will stick with Lead Acid for now, while awaiting the price of larger drop-in lithium batteries to come down. Thanks gents! Stay safe! |
10-13-2020, 03:11 PM | #8 |
Gone Wild
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 9,329
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Re: Questions on maximum current when using drop in batteries
The battery that you use does not have to match the controller motor current in order to deliver full performance and deliver the controller full current output.
If you had a controller with data logging capability it would be helpful if you ran a few data logs and noticed the Battery vs Armature current relationship. You could then lower the battery current setting and see if you noticed any reduction in performance. |
10-13-2020, 04:12 PM | #9 | |
Gone Wild
Join Date: Jul 2018
Location: Ramer, AL
Posts: 1,447
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Re: Questions on maximum current when using drop in batteries
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10-13-2020, 05:02 PM | #10 |
Not Yet Wild
Join Date: Mar 2010
Location: Texas
Posts: 17
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Re: Questions on maximum current when using drop in batteries
Thanks Sergio! Hi Brad, thanks for the real-world feedback - appreciated! I am wanting peace of mind when fully loaded and running flat out uphill.
I must admit I am not well read on RoyPow - I did not know about the 160AH batt - so I did some reading. At first I saw that the 160AH lists a 100amp continuous draw, and 200amp for 10 secs maximum draw - this seems too low for me. Then I saw they have a P-version - S51160P - it has a 160amp continuous draw, and 315amp for 30 secs maximum draw - this looks good to me! I read the P series is coming out this fall - hoping they get here sooner than later! Thanks guys! |
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