Starting Battery load testers are never a good tool to assess an EV
except maybe their ability to weed out duds that drop out as soon as you
put a little load on them,
but the best way to verify EV batteries is capacity test, after first
making sure you have added distilled water to
bring the level above the plates if any are too low, then fully charge
them, then fill them to standard level
(I always used a special bottle with the automatic refill cap that will
stop filling as the electrolyte level
reached the nozzle of the cap, stopping air intake).
The capacity test means applying a load and measuring how long it takes
till the voltage drops to minimum
There are automated testers for that, but you can also set up your own
tester as there is no rocket science to it.
In essence it is a circuit to measure voltage and this can be as simple
as a voltage watchdog that is used in
microprocessor circuits, plus a way to take its control output and turn
off a load, for example a heavy duty relay.
As a load for a 6V battery most people use a piece of wire that will
give you a somewhat constant current.
By measuring time from the moment the test starts with a fully charged
battery to the moment the relay
is disengaged due to reaching minimum voltage on the battery, and
multiplying by the current through the wire,
you can estimate its capacity.
I once needed a way to measure this discharge time on my battery tester
and so I took a cheap clock that runs
from a single AA battery, removed the battery and replaced with 3 diodes
in series in forward direction and a parallel electrolytic
capacitor. Then I used a resistor to feed the clock from the load
resistor, so it would run as long as the load is powered.
I could reset the hands to 12:00 and start the test, when it stopped the
hands would tell me how long it ran...
Since the clock needs only a few milliamp, I did not affect the test
with the clock. I think I used a 1k Ohm resistor,
while the resistance of the wire I used was about 0.15 Ohms, resulting
in 80 Amps discharge at 12V.
Mark each battery that has decent capacity and set the duds aside for
recycling (you should get some money for them!
I returned the bad batteries from a "need new batteries" EV to O'Reilly
and have still not spent everything that they
put on the gift card...)
After going through all, you have a good idea if it makes sense to use
the 16 best or you need a new pack...
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of harry henderson
Sent: Friday, May 26, 2017 4:47 PM
Subject: [EVDL] looking for cheap load tester for trojan T125 6v
the 16 trojan T125 6v floodies in my bradley are 5 years old with around
5k-10k miles on them, however, because of abuse and negligent some to
all of them need replaced. i am retireing my 69 bus that has 20 trojan
T125 6v floodies from the same pallet and those batteries are in better
shape. i would like to have an easy and cheap way to find the best 16
batteries out of those 36. would specific gravity be enough or should i
get a load tester? if i need a load tester would either of these below
suffice to at least let me rank the batteries. i don't think either are
perfect solutions but maybe good enough to weed out the worst of the
harry Albuquerque, NM current bike:
http://www.austinev.org/evalbum/1179 current non-bike:
Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag
racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
Read EVAngel's EV News at http://evdl.org/evln/
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)