Question - Relay/timer boards 36 volt?

[gardnerphoto]

I have been buying relay/timer boards from a (will keep name secret) reputable source for my powerwise and total charge chargers,I have had trouble with some batteries,maybe 1 out of pac of 6 couple of times,going bad,thankfully they were under warranty,no problem getting them replaced,contacted my relay/timer board supplier,This is what they told me...

"Older boards will reach 45 volts within 12 hrs,To be safer we made ours to do it within 3 hours and/or 42-43 volts to be less harmful to battery."
Is this info correct to be safer for the batteries?
Only 3 hours,is this enough time?
Please help....

[mgray70]

It don't sound right to me. Time would depend on condition and state of charge of the batteries, and cutting off under 45 volts would be under charging the batteries.

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[JohnnieB]

Originally Posted by gardnerphoto

I have been buying relay/timer boards from a (will keep name secret) reputable source for my powerwise and total charge chargers,I have had trouble with some batteries,maybe 1 out of pac of 6 couple of times,going bad,thankfully they were under warranty,no problem getting them replaced,contacted my relay/timer board supplier,This is what they told me...

"Older boards will reach 45 volts within 12 hrs,To be safer we made ours to do it within 3 hours and/or 42-43 volts to be less harmful to battery."
Is this info correct to be safer for the batteries?
Only 3 hours,is this enough time?
Please help....

Wow, I don't know where to start.

In ferroresonant transformer type chargers such as the one you mentioned, the actual battery charging circuit consists of the ferroresonant transformer, the boost capacitor and diodes. The control board is a semi-smart on/off switch that turns on the charging circuit if the battery pack voltage is high enough to energize the relay on the board and shuts of the charging when the on-charge voltage reaches a pre-selected voltage, such as 45V. There is also a safety timer that shuts off the charging circuit is the on-charge voltage fails to climb to the per-selected voltage with in a pre-selected time, typically 12 or 16 hours. There is absolutely nothing the control board cam do to alter how fast the battery pack is charged.

The control board can be altered to shut off the charging circuit at a lower voltage (IE: 42V - 43V), but that only means the battery pack will be even less charge that it is when the charging circuit doesn't shut off until 45V.

The back up timer on the control board can also be altered to shut of the charging circuit is 3 hours, but that limits how long the charging circuit has to charge the batteries and the batteries will not be charged.

In a nutshell, a control board that shuts off the charging circuit at 42V - 43V is guaranteed poor cart performance (undercharged batteries) and dismal battery lifespan (low average SoC), as does a 3 hour backup timer.


If anything the cutoff voltage ought to be raised the 46V or 47V to more fully charge the batteries.

FWIW: A Lead-Acid battery isn't fully charged until the on-charge voltage stops increasing and 45V was picked because it was high enough to almost fully charge newer batteries without overcharging older batteries.

BTW: Fully charging a lead-acid battery doesn't harm it.

[gardnerphoto]

So all these boards,that I have installed,and some still on my shelf should be returned,

[JohnnieB]

Originally Posted by gardnerphoto

So all these boards,that I have installed,and some still on my shelf should be returned,

If they are shutting off the charging circuit at less than 45V +/-1V, or in 3hrs, yes!!!!!

Of course, I'd verify what the cutoff voltage is and how long it took for the timer to time out. The info you got over the phone might not be factual, I'd have to see those specs in writing to believe them.

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The ferroresonant transformer type chargers are designed to comply with the attached recommended charging profile. It shows a recommended end voltage of 2.45VPC (Volts per Cell) to 2.79VPC, which equates to 44.10V to 50.22V for a 36V pack (18 2V cells). The plateau in the voltage curve at 2.35VPC (42.3V for a 36V pack) is the onset of the gassing stage.

As for how long it take for a ferroresonant transformer type charger to charge a battery pack, it depends on how deeply the batteries have been discharged. Max recommended discharge is 50% and the 225AH Trojan T-105 is the standard battery for a 36V pack, so 112.5AH would have to be returned to the battery pack. The output amps of a typical 36V ferroresonant transformer type charger is about 18A, so that would thak 6.25 hours, IF the charger's output stayed at 18A, which it doesn't, it when the on-charge voltage reaches about 2.35VPC (42.3V for a 36V pack), and starts tampering off. At the gassing stage , the SoC is at about 80% to 90%. So it takes about 5.5 hours to reach 80% to 90% and another 2 to 4 hours to reach the max recommended end voltage. Plus the charging process is not 100% efficient, so another 10% to 30% can be added to the overall charging time and you could be bumping into a 12 hour back up timer.

BTW: In order to charge a 50% discharge standard 36V battery pack in three hours, the charger would have to put out over 40A.