Harry, Starting Battery load testers are never a good tool to assess an EV battery, 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... Success! Cor. -----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of harry henderson via EV Sent: Friday, May 26, 2017 4:47 PM To: email@example.com Subject: [EVDL] looking for cheap load tester for trojan T125 6v floodies 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 batteries? http://www.ebay.com/itm/New-Battery-Load-Tester-100-Amp-Load-Type-6V-12V -Mechanics-6-12-Volt-Car-Truck-/400774129287?hash=item5d4fffe687:g:I-gAA OSwhQhYyBBw http://www.ebay.com/itm/6V-12V-500-Amp-Carbon-Pile-Battery-Load-Tester-A lternator-Starter-1000A-Testing-/400801422805?hash=item5d51a05dd5:g:EFEA AOSw8w1YBSTQ harry Albuquerque, NM current bike: http://www.austinev.org/evalbum/1179 current non-bike: http://evalbum.com/1000 _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)