Solar Battery Charging and Diodes

You seem to be thinking of an intelligent charger connected to a single battery through diodes. That makes no sense - no diode is needed.

Go back, look at your schematic, add the capacitor across the charger and decide what happens when you start the charge cycle with one battery fully discharged at say 11.5 volts, and the other fully charged at say

13.8 volts. Do you see how the charger's intelligence is defeated? I can't see a way for the battery that started out fully charged to benefit from the fact that we're using an intelligent charger. It is going to be overcharged, severely. That 150 mV figure is totally bogus. It might be accurate for 1 battery, but it can never be expected to accurately reflect the voltage on more than one.

Ed

the capacitor shows the lower voltage, and when the charger turns on the current will flow to the lower voltage battery,

No I can't. Can you explain it?

it can't until the other batteryy catches up.

how is that going to happen? the source is photovoltaic cells the current won't be high enough to achieve that.

only the voltage of the weaker one...

Bye. Jasen

Correct. And it will flow to the higher battery, too. The charger will want to force a lot of current into the discharged battery and will produce a voltage above the fully charged battery. Why do you omit that fact?

See above. Or think. You have two batteries connected to the intelligent charger. How can it apply its intelligence to both at the same time, when the batteries need different charge rates?

When the battery reaches full charge, the intelligent charger will switch rates or terminate, in a normal setup. In the diode isolated, multiple battery setup, the intelligent charger will continue to charge the already fully charged battery at a high rate while the other battery is low. The intelligence is defeated.

If you understand that, then how in the hell can you say above that you can't see how the intelligence is defeated? Are you being purposely obtuse?

The fully charged battery would benefit by the charger turning off, or reducing its rate, just as is designed into the intelligent charger, if the intelligent charger could "see" it. But the charger can't "see" it. Therefore, the battery does not get the benefit of the charger's intelligence.

It gets worse: Meanwhile, assuming the capacitor scheme deceives the charger into "seeing" the other battery at much lower voltage, the charger continues to charge at a high rate, which works to the detriment of the fully charged battery.

That's engineering by assumption. You have no way of knowing the capacity of his solar bank.

QED. Thus the problem.

Ed