Batteries Charging at 10 amps for 24 hours

[rockfordpi]

very atypical Battery Situation

Have a 36 volt cart with HUGE 178AH 6 volt batteries. Lester 36v older transformer type Charger, control board failed, replaced with manual timer.

Initially charged cart about 18 hours with a different 12 amp charger. Cart load tested at 75 amps for 55 minutes, but most of those minutes were at the low end of the voltage range.

Next Cart was charged 30 hours on and off, batteries were still taking 10 amps from charger. Stopped charge. let batteries sit 12 hours, had SG of around 3 per cell and 6.45 volts per battery. Electrolyte above plates.

Put cart back on charger for 24 hours straight, and and batteries are still taking 10 amps from charger.

I understand there is no voltage cut off with manual timer. However, should it continue to pull 10 amps after 24 hours of charge?

Should I cut charger off and load test again or keep charging?

Is this a charger issue and/or battery issue?

I do realize batteries are about shot, but 55 minutes is still useable for a "going to the mailbox cart." Just not sure how to go about keeping it charged and how long to allow charge and why amps are not falling to near zero after 24 hours, even if charger does not shut off.

[cgtech]

Ok, so what is pack voltage "at 10 amps" after 24 hours while on charge? I imagine they might stink at that point? Obviously they are in poor health, and probably fed "garden hose water" for their life? Not denying any claims, just looking for data.

[rockfordpi]

Originally Posted by cgtech

Ok, so what is pack voltage "at 10 amps" after 24 hours while on charge? I imagine they might stink at that point? Obviously they are in poor health, and probably fed "garden hose water" for their life? Not denying any claims, just looking for data.

Took batteries off charge and let sit overnight last night. This morning pack voltage was 39v, 6.46 volts per battery.

Put charger back on, initially showed 20 amps, but slowly dropped to 14 amps with on charge voltage of 44 volts. After 30 minutes, charger fell back to 8 amps which is lowest yet. On charge voltage is 45.1v

There is some acid smell, but no real bad, I have smelled much worse, and the cart is in an enclosed area.

[cgtech]

That charger is "hot", most manual chargers aim for about 45v at end of charge.

[rockfordpi]

Originally Posted by cgtech

That charger is "hot", most manual chargers aim for about 45v at end of charge.

So, if I understand, you are saying charger is good and the issue is the Batteries?

Just checked again, now batteries are back to drawing now 10 amps again, I was not expecting that. The on charge voltage is now 44.7.

Should I continue to charge? I am keeping check on water and adding as needed.

[rockfordpi]

Originally Posted by rockfordpi

So, if I understand, you are saying charger is good and the issue is the Batteries?

Just checked again, now batteries are back to drawing now 10 amps again, I was not expecting that. The on charge voltage is now 44.7.

Should I continue to charge? I am keeping check on water and adding as needed.

After about a 36 hours total charge time, batteries were still taking 10 amps.

Stopped charging and load tested; got 90 minutes at 75 amps, a tad over half their original rating.

However, volt decrease under load did not seem to be linear, a much greater time was spent at the lower end of the voltage range. Not sure if this is normal or not or if it matters.

Back on charger now, set for 12 hours, will check amps then. I guess my only question now is HOW long should I set the timer on charger normally to charge the batteries?

[cgtech]

I think the batteries are compromised, likely by using tap water. It sure is a shame to see 90 minute batteries acting so badly. I bet when you check them in the morning while still on charge, they are real nice and warm too. Like 120f . Bummer, likely bad batteries. Tried your charger on anyone else's cart?

[rockfordpi]

Originally Posted by cgtech

I think the batteries are compromised, likely by using tap water. It sure is a shame to see 90 minute batteries acting so badly. I bet when you check them in the morning while still on charge, they are real nice and warm too. Like 120f . Bummer, likely bad batteries. Tried your charger on anyone else's cart?

Have not tried charger on another cart, but if I understood Johnny B's comments in another post, this type transformer charger should stop putting out amps and fall to zero when batteries are full and stop taking amps.

However, I may have misunderstood JB on that. Could there be a problem with charger that would cause it to continue to force amps into fully charged batteries?

Have charged about 20 hours now since discharge, they are still taking 10 amps.

[JohnnieB]

Originally Posted by rockfordpi

Have not tried charger on another cart, but if I understood Johnny B's comments in another post, this type transformer charger should stop putting out amps and fall to zero when batteries are full and stop taking amps.

However, I may have misunderstood JB on that. Could there be a problem with charger that would cause it to continue to force amps into fully charged batteries?

Have charged about 20 hours now since discharge, they are still taking 10 amps.

Ferroresonant transformer type chargers do not stop putting out amps, the amps merely decrease to a lower amount as the on-charge voltage increases.

When the charger is first connected to the battery pack, the transformer core saturates when about 20A or so are flowing through battery and stays at the amp flow until the on-charge voltage climbs into roughly the 40V neighborhood and then begins to taper off. The on-charge voltage reaches a plateau at about 2.35VPC (Volts per Cell), which is 42.3V for a 36V pack, but the amp flow continues to decrease until it reaches a minimum flow rate, typically about 1% to 3% of the AH rating of the batteries. At that point the on-charge voltage will eventually start to climb again and will eventually reach the voltage the charge's control board shuts the charger off, or the charger's maximum output voltage is reached, or the on-charge voltage ceases to increase because the batteries are fully charged.

The attached chart shows the volts and amps relationships. (These old charger designs were based on Trojan battery recommendations.)

Of course the above relationships assume the batteries are healthy and the capacitor's µF value has not drifted with age, but with old batteries and an old charger, one or both of those is likely to be false.

If the batteries are 178AH, than a 10A charge is only about 5.6% of the AH rating and they ought to be able to tolerate that amp flow for days, or at least until the temperature of the electrolyte climbs up to about 120°F.

What is the individual battery voltages and pack voltage while on charge after several hours at 10A?

[rockfordpi]

Originally Posted by JohnnieB

Ferroresonant transformer type chargers do not stop putting out amps, the amps merely decrease to a lower amount as the on-charge voltage increases.

When the charger is first connected to the battery pack, the transformer core saturates when about 20A or so are flowing through battery and stays at the amp flow until the on-charge voltage climbs into roughly the 40V neighborhood and then begins to taper off. The on-charge voltage reaches a plateau at about 2.35VPC (Volts per Cell), which is 42.3V for a 36V pack, but the amp flow continues to decrease until it reaches a minimum flow rate, typically about 1% to 3% of the AH rating of the batteries. At that point the on-charge voltage will eventually start to climb again and will eventually reach the voltage the charge's control board shuts the charger off, or the charger's maximum output voltage is reached, or the on-charge voltage ceases to increase because the batteries are fully charged.

The attached chart shows the volts and amps relationships. (These old charger designs were based on Trojan battery recommendations.)

Of course the above relationships assume the batteries are healthy and the capacitor's µF value has not drifted with age, but with old batteries and an old charger, one or both of those is likely to be false.

If the batteries are 178AH, than a 10A charge is only about 5.6% of the AH rating and they ought to be able to tolerate that amp flow for days, or at least until the temperature of the electrolyte climbs up to about 120°F.

What is the individual battery voltages and pack voltage while on charge after several hours at 10A?

Pack Voltage is 44.8 volts, amps have fallen to 8 amps after charging all day and all night last night. Individual batteries run from 7.43 to 7.48 volts.