I think it would be better to measure at a higher amp rating if possible. (Make your test go faster, and more accurately model the true draw on the battery under load).

How many amps will the batteries see under your particular usage scenario? If you can replicate that same amp draw (either with lots of lights, a big resistor in a bucket of water or whatever....) it would probably be the best test for your situation. (Plus, if the amp draw is higher, the precision of the amp meter would matter less....)

Jay

On 3/13/19 3:38 PM, Dan Baker via EV wrote:
Thanks guys- never thought of this, I have a similar unit in my boat
already.  I typically use it just for monitoring amp output and volts.  I
have two throttles on my boat, a spring loaded Curtis-PB6 which I use for
docking/ maneuvering and a 5k knob style pot that I switch over for
cruise control, set the pot for desired amps/speed off of the gauge.  I'm
not sure if it will accurately pick up a small 1 amp load as it is rated
for up to 400 amps.  Anyone share what they used for a test load- a
resister or a bulb?  I assuming around 1 amp (12 watts) will be closest to
measuring true a/h readings.  Given that these lithiums only charge to 12.6
volts means my cut-off voltage will likely be closer to the stated BMS
cut-off, somewhere between 9-10 volts or when the voltage starts sharply
falling off?

On Wed, Mar 13, 2019 at 3:23 PM John Lussmyer via EV <ev@lists.evdl.org>
wrote:

On Wed Mar 13 11:06:36 PDT 2019 ev@lists.evdl.org said:
Yep Totally agree. I use several of these to monitor voltages and
currents in my DIY EV. Nice thing about them is that they work both ways
and will take into account regen and charging as well as discharge. I
found them to be as accurate as shunt based meters at a similar price
range BTW.

I use this one:

https://www.amazon.com/Programmable-Digital-meter-battery-monitoring/dp/B0043BDFYA/ref=sr_1_1

has 2 relay outputs, counts AH in both directions, uses a shunt for
currents over 5A.
I've found it to be pretty accurate.


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