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How often are you benchmarking the performance of your DPV batteries? I used to do a full cycle every 6 months, but decided that was causing undue wear on my DPV's.
How often are you benchmarking the performance of your DPV batteries? I used to do a full cycle every 6 months, but decided that was causing undue wear on my DPV's.
To be 100% honest, I do not have as good a handle on the electricity stuff as I would like. I'm using the same resistor array that George uses. According to him (and he's a source I trust) this array reproduces the load on the scooter when it is pulling a diver, stages, and tow scooters at full pitch.
By hooking up the resistor, checking voltage every 10mins, and stopping the test when that batteries hit 20v, I know how long the batteries burn under the above conditions. Since the very max I ever plan to burn a scooter for is 66%-80% of that time, I have quite a bit of cushion to allow for inconsistencies with the motor, my equipment load, pitch, contingency stuff, etc.
I get 120mins on my Powersonic 35Ah batteries. 42s get 160mins, 26 gets 90mins, 18 gets 60mins, IIRC. There is variance between manufacturers and individual batteries. If you don't have a Gavin, all this might not apply to you.
I burn test using a resistor bank and a data recorder annually, then, sticker the battery with the result in Watt-hours.
Using a data recorder is an extra expense (buying a Eagle Tree recorder is about $80), but I think it's worth the money.
Here's an example of the graphical output from such a burn test:
This contains a lot more information than you'd get just from timing a burn test. For example, RPM is related to voltage; in this case, you can see that the voltage doesn't begin to decline significantly until 2/3rds of the way through the discharge.
This is useful, because (with this particular battery pack) when you feel the scooter begin to slow down, you'd know the battery is only has 1/3 of of it's life left. So, that's good data.
Also, a data recorder can warn of impending failure. For example: in a NiMH, or, Lithium pack, the battery pack is made of individual cells. When one of these cells begins to go bad, it will stop supplying voltage before the rest of the pack.
As the cell stops producing voltage prematurely, the voltage of the unit will suddenly drop. Eventually, the rest of the pack will "make the catch", and the voltage will stabilize.
This behavior is very distinctive, and is called a "hook". Below we can see a burn-tested pack with a weak cell. The hook warns that this cell will fail soon, and a repair is imminent.
It is tempting to think of Lead-Acid batteries as a single cell battery, because of their monoblock construction. In reality, they, too, are composed of individual cells, and these cells will typically begin to fail a cell at a time.
Because of their construction, the "hook" is nowhere as dramatic, and is actually quite subtle. It is still there in the end of the discharge curve, however, and signals the impending failure of the entire battery (since you can't replace an individual lead acid cell, eh?).
Below we can see the output from a lead acid with an impending cell failure, if you look closely you can see the characteristic wobble of a lead-acid's version of a hook.
The other big advantage of a data recorder is you can take it diving! Very quickly, on typical dives, you can get a feel for your typical scooter consumption in Watt-hours. Reference this to your known battery capacity, and you can tell if you're exceeding 1/3rds for mission planning.
To the OP's question: I watch my battery characteristics pretty closely by running a data recorder often. I haven't seen a decrease in battery performance from annual burn testing.
If I was to point to anything that extends scooter battery life, if would be to dive them often. Batteries that aren't used often seem to lose capacity much quicker.
I burn test using a resistor bank and a data recorder annually, then, sticker the battery with the result in Watt-hours.
Using a data recorder is an extra expense (buying a Eagle Tree recorder is about $80), but I think it's worth the money.
Here's an example of the graphical output from such a burn test:
This contains a lot more information than you'd get just from timing a burn test. For example, RPM is related to voltage; in this case, you can see that the voltage doesn't begin to decline significantly until 2/3rds of the way through the discharge.
This is useful, because (with this particular battery pack) when you feel the scooter begin to slow down, you'd know the battery is only has 1/3 of of it's life left. So, that's good data.
Also, a data recorder can warn of impending failure. For example: in a NiMH, or, Lithium pack, the battery pack is made of individual cells. When one of these cells begins to go bad, it will stop supplying voltage before the rest of the pack.
As the cell stops producing voltage prematurely, the voltage of the unit will suddenly drop. Eventually, the rest of the pack will "make the catch", and the voltage will stabilize.
This behavior is very distinctive, and is called a "hook". Below we can see a burn-tested pack with a weak cell. The hook warns that this cell will fail soon, and a repair is imminent.
It is tempting to think of Lead-Acid batteries as a single cell battery, because of their monoblock construction. In reality, they, too, are composed of individual cells, and these cells will typically begin to fail a cell at a time.
Because of their construction, the "hook" is nowhere as dramatic, and is actually quite subtle. It is still there in the end of the discharge curve, however, and signals the impending failure of the entire battery (since you can't replace an individual lead acid cell, eh?).
Below we can see the output from a lead acid with an impending cell failure, if you look closely you can see the characteristic wobble of a lead-acid's version of a hook.
The other big advantage of a data recorder is you can take it diving! Very quickly, on typical dives, you can get a feel for your typical scooter consumption in Watt-hours. Reference this to your known battery capacity, and you can tell if you're exceeding 1/3rds for mission planning.
To the OP's question: I watch my battery characteristics pretty closely by running a data recorder often. I haven't seen a decrease in battery performance from annual burn testing.
If I was to point to anything that extends scooter battery life, if would be to dive them often. Batteries that aren't used often seem to lose capacity much quicker.
All the best, James
Hey there fdog,
I realize I'm waking this thread up after a short nap....
I'm getting into doing my own testing of my scooter and dive lights power supplies and operational efficiency and I have a few questions regarding some of the tools out there for testing batteries among other parameters...
Have ever used the CBA III battery analyzer before, If so, do you find it sufficient to test scooter power supplies or do you think the amplifiers are required (I ask based on the Wattage scooters use vs the CBA specs sheet). Also, about the eLogger: Do you find that using any of the add on components, such as RPM monitor and the LCD display would be beneficial in any way? I believe the LCD display is something very similiar to the "watts up" meter, so I sometimes wonder if I could find a use for it, or would it just be an extra tool, because the CBA or elogger already has its capabilities?
I'm also curious about how to connect them to the scooter and power source? Do you have to find a seperate vendor that has connectors that fit your scooter or lights connectors or do you have to solder it to the data recorder? I thought thats how the medusa oracle was, but they are no more and you are the first person to post, that I've found, about the eLogger being used in this type of testing (since its mainly used for RC applications)... Well thanks for your time and I look forward to anything you may have to add...
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Originally Posted by diverdoug1
