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Old 12-06-2021, 10:11 PM   #1
turbo_wagon
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Question Allied drop-in capacity question

Hello BGW Experts!

I have a question about the rated Ah capacity on the Drop-In style batteries. Should I expect to get the full amp hour capacity from each battery parallel connected in the pack per full charge?

Using a shunt-style coulomb counter SOC meter, I only get about 40Ah useable capacity from a 60Ah rated pack (2 X 48v @ 30Ah) before the pack shuts down and goes dead. I have all of the inputs and loads going through the shunt and calibrated the meter after the pack was at 100% according to the charger.

Any input would be appreciated
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Old 12-07-2021, 01:41 AM   #2
Pat911
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Default Re: Allied drop-in capacity question

Yes, you should get the rated capacity, anything less is false advertising.

Cheers
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Old 12-07-2021, 08:55 AM   #3
Volt_Ampere
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Default Re: Allied drop-in capacity question

It's also possible that your SOC meter isn't accurate.
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Old 12-07-2021, 09:22 AM   #4
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Default Re: Allied drop-in capacity question

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Originally Posted by Volt_Ampere View Post
It's also possible that your SOC meter isn't accurate.
The meter I'm using is on the cheaper side. It's the AiLi meter that was pretty well reviewed on the solar power forums and about $40 on Amazon. Definitely a possibility I'm keeping an eye on.

If it's not the meter, could it be that my pack of 2 got out of balance? Could that cause decreased capacity? I was running a power converter wired directly to the pack unswitched for about two months before switching to a switched power converter. I've heard people warning against running the converter directly off the pack due to the constant draw.
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Old 12-07-2021, 09:25 AM   #5
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Default Re: Allied drop-in capacity question

Batteries in parallel won't go out of balance (total voltage has to always be the same) The BMS's should keep your individual cells balanced. If your SOC meter was meant for solar, it's not going to be accurate on a golf cart. Currents are much higher and much more variable when running a traction motor with a switching controller.
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Old 12-07-2021, 10:00 AM   #6
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Default Re: Allied drop-in capacity question

Quote:
Originally Posted by Volt_Ampere View Post
Batteries in parallel won't go out of balance (total voltage has to always be the same) The BMS's should keep your individual cells balanced. If your SOC meter was meant for solar, it's not going to be accurate on a golf cart. Currents are much higher and much more variable when running a traction motor with a switching controller.
The meter isn't meant for solar per se, it's rated at 350A. You set it up by charging your pack 100% then set the Ah capacity and it counts the amps going in and out after that. I'm assuming that amps are amps regardless of what's drawing them.


I've searched around on the forums and it seems like people are still using pack voltage to measure SOC even with such a tight curve on lithium.
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Old 12-07-2021, 02:15 PM   #7
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Default Re: Allied drop-in capacity question

Amps when a controller is chopping them are hard to measure accurately - and many of these meters do not the best job of averaging accurately. With LiFe batteries, measuring SOC with battery volts doesn't work very well at all. The curve is way too flat to estimate SOC given all sorts of conditions. With my Leaf cells, I can get a fairly good estimate of SOC from battery voltage - probably good to 5%.
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Old 12-07-2021, 03:22 PM   #8
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Default Re: Allied drop-in capacity question

It may be your meter, I use this one,

https://www.amazon.com/Renogy-500A-B.../dp/B07RP5B5P7

I accurately measured the capacity of one of my leaf modules on the bench at 40Ah using a battery capacity tester. I have 21 modules in my cart so 3 in parallel. This meter is accurate in the cart when set at a capacity of 120Ah.

Where this meter fails is when it’s left for months unattended as I don’t think it’s measuring it’s own, and certainly not measuring the BMS current draw. That’s an easy fix though, just give the battery a full charge after it’s been sitting and you’re good to go.

It also could be that you have one faulty battery. Can you split the pack and test one at a time? You may not have the current capacity to run your cart as per normal but you should be able to limp it around for the test.

Cheers
Pat.
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Old 12-07-2021, 04:47 PM   #9
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Default Re: Allied drop-in capacity question

Quote:
Originally Posted by Pat911 View Post
It may be your meter, I use this one,

https://www.amazon.com/Renogy-500A-B.../dp/B07RP5B5P7

I accurately measured the capacity of one of my leaf modules on the bench at 40Ah using a battery capacity tester. I have 21 modules in my cart so 3 in parallel. This meter is accurate in the cart when set at a capacity of 120Ah.

Where this meter fails is when it’s left for months unattended as I don’t think it’s measuring it’s own, and certainly not measuring the BMS current draw. That’s an easy fix though, just give the battery a full charge after it’s been sitting and you’re good to go.

It also could be that you have one faulty battery. Can you split the pack and test one at a time? You may not have the current capacity to run your cart as per normal but you should be able to limp it around for the test.

Cheers
Pat.
Would you mind sharing the battery capacity tester you used?
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Old 12-07-2021, 07:27 PM   #10
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Default Re: Allied drop-in capacity question

Sure, it's definitely no big secret, it's just a cheapie from China but it does the job. It's sometimes referred to as an electronic load. But make sure you get the 4 wire one, not the 2 wire examples. The 4 wire will compensate for voltage drop in the cables.



https://www.aliexpress.com/item/4001...12705811%22%7D

https://www.ebay.com/itm/19443824374...3ABFBM3Ibv9rJf
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