A Tale of Two Chargers

I run into the same problem all the time. I have a trickle charge charger that I hook up and let it run for several hours with its low settings. Then I can hook up my VEC1093DBD and let it do its thing.

Car START batteries do not like being discharged all the way down for sure. You will lose a bunch of performance once they go all the way down. The deep cycle batteries are alittle more forgiving but do about the same thing. Once the get below the 50% charge state then they also drop off on performance.

The game plan is to plan where neither one gets belows the 50% charge state (Around 12.0VDC ever!!!)

You might want to use a trickle charge or small solar panel on your parked vehicles when left unattended for a long length of time. My JEEP used to sit alot when we were on camping trips. I just layed one of those small solar panels on the dash behind the wind shield where it would get full sun a big part of the day. Plugged it into the 12VDC cigarette lighter socket that was always connected when the ignition key was removed and always keep the Jeep start battery topped off - ready to go...

The B&D needs the battery to have 4 or so volts or it won't run, as you saw there. To beat that, first apply some charge from the dumb charger or jumper cables or solar, then start the smart charger and it will get going.

The B&D has a way better charging profile so it is worth using that once it can run.

You might also notice on a very low battery that the charger only does really low amps, so you might think something is wrong. Let it keep running and the amps will slowly increase as the battery comes back to life until the charger is at its max amps. Then after that, the charger will do its normal profile.

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Batteries; either starting, or deep-cycle, will not recharge with a smart-charger unless the voltage is around 10.5 volts (considered almost a dead battery).

Voltages less than that usually require charging at a lower rate of 2 amps (or less) for a few hours to bring the battery back up to around 11.6 volts (>20%soc). If the smart-charger has a small battery (2 amp setting) it would be used first. Then the smart charger could work to finish charging on a higher amperage setting. Using your "dumb" charger would also work as you found out.

However; starting batteries can only recover from being allowed to discharge only a few times. You may find yourself having to replace the battery in the next few months.