new batteries are dead

We bought 2 new batteries from AndyMark and neither will charge. They show no potential across the terminals. When we plug them into the old style (like 6 years old) chargers, the charging indicator does not light up.

Do we need the new style charger (perhaps they have a conditioning mode or something) to get a new (and dead) battery running? Its hard to believe the batteries are actually dead.

Anyone have special knowledge of this failure mode and/or our goofy human error?


They may have been improperly stored ie: with no charge in them.

I know with car batteries (non-sealed) you can “shock charge” them back to life but I won’t even speculate what would happen if you tried this on a sealed battery. A vented battery during this process actually boils the electrolyte and produces a great amount of flammable Hydrogen gas. NOT a safe process by any means. I would recommend calling AndyMark and requesting replacements.

The only other option is to check if the Connectors are properly connected.

they are - thanks

If it measures nothing at all across the terminals I would guess that one or both of the terminals have broken internally.

If you shock a battery with a taser you can sometimes bring it back to life. However I DO NOT RECOMMEND THIS with large batteries. I’ve only done this with NICad 18v drill packs.


I have never heard of shocking batteries with a taser… I really don’t think it would have any sufficient amount of energy to have any effect on the cell whatsoever.

Traditional shock charging involves charging your batteries at an elevated voltage and amperage for a short period of time. The idea here is that when batteries sit for a long time with no charge in them, sulfates can build up on the internal plates and cause them to short out internally or significantly reduce their surface area. Now I have only ever done this on conventional lead acid batteries so I have absolutely no clue how a sealed maintenance free cell will react. With a conventional battery the technique involves hooking it up to a charger with a high amperage “start” setting for about 20 minutes. During this process a great deal of hydrogen gas is produced and it is not uncommon for it to leak electrolyte. This high charge rate forces much more power into the battery than it was ever designed for and as a result the electrolyte begins to “boil”. The thermal and mechanical action on the plates removes the sulfation. Again, NO idea how this would work on a sealed battery- my thought is that you could end up rupturing the cell. In any case, if you decide to try this (if AndyMark won’t give you a new one or you need to try and get one working) then just make sure you do this outdoors in a safe location where if the cell does rupture it will not hurt anyone or damage anything.

**!!! DANGER !!! **SLA AGM’s may have unvented internal hydrogen gas pockets!!

Taser provides high peak energy spark blasts (of a few joules ea?) that could ignite the hydrogen. BOOM!!!@!#!@# safety vent valve is designed for slow gas release… not impulse of blast proportion.

Note MK spec max charge current **5.4A **else warranty is void & as it reduces battery life! [from internal heating, causing disassociated gas release]

if battery is sulfated
OR there is an Open
(fused/melted open conductor, aka Pb Lead Vshaped-fuse link between cells)

likely be UNable to draw 5.4A unless voltage is substantially raised above 15.

Taser may be 100KV!! causing spark jump discharge blast between open ends!

(I have used electrolytic Capacitors charged up to ~200V to blast NiCads to successfully charge where conductive whisker growth short is defect mechanism not appropriate for SLA AGM chemistry!!!)

What is defective battery mfr date code?

SLA AGM left dormant (uncharged on shelf) for years may NEVER accept a charge!

=sulfated = high internal battery resistance, think K or Megohms) so draws NO noticable current even at max spec charge voltage of 15.0 v

even if it does initially draw a few uA & gradually charge, drawing mA’s to A’s
the final internal resistance achievable will likely be much higher than spec 0.01 ohm i.e. much lower load current available to robot & at lower terminal voltage i.e. limited & lower available robot power, unacceptable for nominal robot performance, due to battery internal resistance Voltage dip I^2R

motors especially: will exhibit decreased start-up peak power plus depressing terminal voltage to only a few volts- possibly causing dynamic cRIO resets
OR sluggish deeply sagging varying running power.

CIMs normally draw 100A-125A ea for .1-.3s upon full throttle depending on load being pushed (fixed wall, robot pushing head-Head=WorstCase) state of health & charge of a good battery is able to maintain terminal voltage above 9v under such load)

Rule of thumb: Most batteries in-use awhile drop 1v at terminals for each 50A drawn by the robot
(PM me for 50A load Vterminal Vs time, 10s incr 9min plot)

one CIM=100A peak @full throttle: 12.6-2 =10.6 brief terminal voltage sag
(observe with oscilloscope)

Who uses just one CIM in their drive?
2ea CIMs full throttle = 8.6v terminal dip for (~.1s?)

with healthy properly charged (& topped off after fast charge) non-abused fully charged battery:
dip time decreases quickly with increasing motor RPM as robot comes up to speed, and reason why when pushing bots geared down transmission-low permits higher motor RPMs while providing highest torque at reduced robot speed saving extending battery and keeping Vsags from resetting cRIO!

I took the batteries to a battery store and had a fancy (highly technical term we EEs often use) test run on them. They are dead and now make good door stops. We decided not to try to shock a sealed battery.

Thanks for all the input!

If the battery has been run down to zero volts, the smart chargers will not even try to charge them. Sometimes a simple charger will be able to pass enough current to charge them up to the point that a smart charger can then be used. If you use a simple charger or a bench supply, monitor current. If you cannot get a current flowing they are open internally probably due to a fall at some point in time.

Thanks Al!

I suggest you contact the company you purchased them from, tell them what you’ve found, and ask for replacements.