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07-13-2021, 05:11 PM | #21 |
Gone Wild
Join Date: Dec 2020
Location: Melbourne, Australia
Posts: 1,919
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
Voltage is not a good indicator of SOC for lithium batteries. You need a current shunt and measure the current flowing in and out of the battery. I use this one…
https://www.renogy.com/500a-battery-...RoCxiQQAvD_BwE It will also show you the current draw. Do you have a multimeter and are you able to measure the current to the input of the voltage reducer. Cheers Pat. |
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07-13-2021, 05:23 PM | #22 |
Not Yet Wild
Join Date: Jul 2021
Location: North Florida
Posts: 39
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
Thank you. That's good to know.
I'll have to get the right tools for that. My meter can do up to 10A, but I'll obviously need more. Irrespective of the voltage, it seems likely that the reducer is the issue, right? It's the one variable here that makes a big difference. |
07-14-2021, 10:49 AM | #23 |
Not Yet Wild
Join Date: Jul 2021
Location: North Florida
Posts: 39
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
Alright, I did this test. And . . . the reducer is not pulling much at all.
With the key switched off, and no load, the reducer pulls 0.082 amps. With the key switched on, and no load, the reducer pulls 0.113 amps. Which is strange, because, as far as I can see, it's the reducer being plugged in that is correlated with the LED meter showing the batteries draining. Last night, I charged up the batteries and then, when it stopped, I unplugged the charger. I then left the reducer plugged in and put the cart in Drive mode. Over the subsequent 12 hours, the LED meter dropped from 100% to 88%—a drop of 1% per hour. This implies that something is drawing 0.6 amps per hour. But it's not — at least, not as far as I can tell. I ran three tests already. In the first, nothing was plugged into the batteries at all. In the second, the cart was in Drive mode and the reducer was disconnected. In the third, the cart was in Drive mode and the reducer was connected. Only in the third test did the LED meter suggest the batteries were draining. This should lead me to conclude that the presence of the reducer is in some way "confusing" the LED meter (or the BMS that's informing it, if that's how it works). But that just strikes me as wrong, somehow. I guess I need to re-run my second test and, this time, make absolutely sure that the button is in Drive mode. I'm pretty sure I did it right last time around, but instinctively it makes more sense to me that some other element within the cart is pulling amps than that the LED is wrong. If the battery drains with the cart Drive mode and the reducer unplugged, I'll buy a stronger ammeter (my multimeter can do 10A, which was fine for the reducer test, but won't be for other tests, I imagine). I'll report back. |
07-14-2021, 07:00 PM | #24 |
Gone Wild
Join Date: Dec 2020
Location: Melbourne, Australia
Posts: 1,919
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
Hi,
If your SOC meter is purely voltage based, then it cannot be used to give an accurate SOC for a lithium battery, especially LiFePO4. See the chart below to compare the discharge curve of lithium to lead acid. As you can see, there’s a very similar voltage drop between 100% - 90% and between 90% - 20%. You really need a coulomb meter (current shunt) for accurate SOC. When the battery is fully charged a voltage based SOC meter will show a much greater loss in charge than if the battery were at say 85% for the same current draw. Your reducer is only drawing 0.082A, which at 60Ah only equates to 1.64% over a 12h period. Cheers Pat. |
07-14-2021, 07:18 PM | #25 |
Not Yet Wild
Join Date: Jul 2021
Location: North Florida
Posts: 39
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
This is my meter: https://relionbattery.com/products/l...ies-fuel-gauge. I don't know how it works, although I'd hope it's more than merely voltage based given that it's explicitly made to go with my batteries. (As an unrelated FYI: the meter itself pulls 0.03 amps, which means it should be costing me 0.7 amps/day, or just over 1% of my battery setup per day.)
Either way, having run some more tests, I'm now pretty sure that these three things are all simultaneously true: 1. The only circumstance in which the LED meter shows the batteries draining (at about 1% per hour, which implies a 0.6A draw) is when my reducer is plugged in. 2. My multimeter shows that the reducer draws only 0.082 amps when the key switch is off. 3. The LED meter is extremely accurate when I’m driving the cart, showing exactly the percentage reductions one would expect for each journey. (I did extensive testing on this when I first got the batteries.) As far as I can see, these things all contradict each other. So, frankly, I'm pretty stumped. Not sure where to look next, and happy to listen to any advice! I'm going to put a heavy duty switch between the battery and the reducer, but I'd ideally like to work out what's going on, because while that will work, it may in practice be merely covering up the problem. |
07-14-2021, 07:30 PM | #26 | |
Gone Wild
Join Date: Dec 2020
Location: Melbourne, Australia
Posts: 1,919
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
From the page you linked to
Quote:
Something strange is going on. |
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07-14-2021, 07:48 PM | #27 |
Not Yet Wild
Join Date: Jul 2021
Location: North Florida
Posts: 39
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
It's just bizarre.
This is probably nonsense, but is it possible that it's not the reducer per se or the controller per se or anything per se, but the combination? Is there some potential wiring setup that would cause the reducer to draw normally but some other part to draw abnormally? I bypassed the OBC. Could that have anything to do with it? I just don't know where to start. |
07-15-2021, 02:05 AM | #28 |
Gone Wild
Join Date: Dec 2020
Location: Melbourne, Australia
Posts: 1,919
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
Since your meter can measure up to 10 amps, connect it strait to the main positive terminal and measure the current. That will give you the real current draw. DO NOT run your cart with the meter connected. You will blow the internal fuse.
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07-15-2021, 08:43 AM | #29 | |
Not Yet Wild
Join Date: Jul 2021
Location: North Florida
Posts: 39
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
Quote:
(In all of these, the LED meter remained attached. It pulls 0.03 amps.) Cart in Tow mode, no reducer: 0.004 amps Cart in Tow mode, reducer attached: 0.093 amps Cart in Drive mode, no reducer: 0.085 amps Cart in Drive mode, reducer attached: 0.169 amps Cart in Drive mode, reducer attached, key on: 0.234 amps Cart in Drive mode, reducer attached, key on, lights on: 0.562 amps I also connected the charging cables into the run, in case there was some weird issue there. This made no difference either way. Obviously, only the lattermost of these measurements comes close to the draw that the LED meter is implying—which, at 1 percent per hour on a 60Ah array, is 0.6 amps. As such, I suppose there are really only two options: (1) The reader on the LED meter is inaccurate/the batteries' BMS is "thrown off" somehow by the reducer. (2) I have a bigger problem with my batteries somewhere. I can't quite see how (2) makes sense, given that the batteries' performance is excellent, and, thus far, in line with the expected range. I'd be tempted toward (1) if I could see any reason that the LED meter/BMS would be confused by the draw of a 0.082 amp reducer, but not by my driving six miles at 27mph. Baffled. |
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07-15-2021, 05:34 PM | #30 |
Gone Wild
Join Date: Dec 2020
Location: Melbourne, Australia
Posts: 1,919
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Re: Upgraded to 48v lithium; confused about blue wire, black/white wire for accessori
Hi,
Try leaving it in drive with reducer connected for a few days and see if the SOC draw tapers off. 0.169A is a little high for my liking anyhow. You could use a relay to disconnect the input to the reducer when the key is off, that would halve your idle power consumption. When leaving for long periods simply put it into tow mode. 0.004A is extremely low. Cheers Pat. |
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12v, 48v, club car, precedent |
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