Undervoltage

Also known as PWM control.

Your charging voltages should be about 36.8V and Boost charge at 38.4

Be careful with your ventillation due to Oxygen and Hydrogen gasses building up during charging, the mixture is explosive

Ok, 36 Volt system, I calculated for a 32V system

Charge = 41.4V

Boost = 43.2V

Low Voltage Disconnect = 34.2

So, at 32 Volts your batteries are being over drained, this could also shorten the life of them, and on a 36V system, the controllers are possibly not designed for under 33.5 or so.

I have maintained 36V systems on marine applications, but without exception, we used 6-6V batteries and they were supplied by A/C generators and constant volts, not alternators. We pulled 12V and 24V for different components off of the battery system. I can't remember where we had the output voltage of the constant volts set--But I guess that it was 38-40V when we operated most components and we turned it down closer to 36V when the vessel was moored.

I think that it is normal to charge a system with higher voltage than the output when there is a load on it.

I know that a 12V alternators output will be as high as 14.4V.

The implications and issues depend on what the 32 or 36 volts will run, I would suppose.--

32V versus 36V would draw a higher current, but the potential difference between its terminals would show charging systems voltage.

Question is--Is the system 32V or 36V?--Sounds like a definitive 32V.

The system is actually 36V.

Someone decided to substitute the original batteries with four 8V's. There are issues with charging circuits and propulsion controls.

I am trying to analyze if the reduced battery voltage has something to do with it.

Thanks.

Do you have access to three 6 volt batteries or one 6 and one 12? They should not have to be as strong as the main batteries. If you connect the additional 18 volts to the end of the third battery (24 volts from ground) you would have returned to 36 volts. If that returns your controls to proper functions, you know the answer. Good luck.

Many systems have relatively wide operational voltage ranges. You need to check the system specifications to determine if 32V is well within the normal operating voltage range of the system. If yes then everything in system should be designed to work correctly and reliably at that voltage.

One of the first problems I see is the charging system will probably be overcharging the batteries. This would shorten the life of the batteries and could damage the charging system.

If the control system is set up for 36 volts you would not be getting top performance out of your system. Some possibilities depending on the controller and its makeup could be:

1. If it is setup to maintain a certain speed, it would have to draw more current due to the low voltage and could overload the drive.
2. Some controllers monitor the battery charge and shut down certain features as the batteries become discharged. Your system when fully charged would show below discharged due to insufficient voltage.
3. Your application would not achieve full torque, would probably run hotter than normal and have shortened discharge cycles.

These are possibilities with limited information. I don't know what your load is, what the output of your alternator is, what type of drive you have or how any of this is being used. Unless your drive and regulator are adjustable for varying input and output voltages there could be long term consequences.

could you tell where I can find technical reference for case like this?

I am thinking of generating a problem report and submitting to our engineering group.

Thank you.

Folks, thank you for responses.

Propulsion ECU can tolerate voltage as low as 28V. However there are issues with charging contactors and fuses. The batteries were said to be replaced in 24 months interval but it happens not regularly and we experience battery chargers issues.

Lead Acid batteries replaced original NiCad set and they are running on 36.5V on board LV system which provides 2.28V/cell float charge. It is said to be "at the low end of range".

System is regulated by solid state control unit via saturable reactor coils. Regulator is set at 36.5V, which means it will never see voltage of 36.5V from 32V battery bank. Rectifier designed to provide range 35V-45V.

My opinion is - this arrangement leads to eventual overcharging of the batteries and reducing relaiability of a vehicle.

Your thoughts.

For a 32V battery system,

For Standard/trickle charging, you'll be running 1.15V/cell, or 36.8V charge

For Boost charging, you'll be running 1.2V/cell, or 38.4V charge

Low Voltage Disconnect (undercharged batteries) you'll try and disconnect at about 0.95V/cell or 30.4

The propulsion ECU may be able to handle down to 28V, but this is below what I would discharge a battery bank down to, also this allows the controller to to remain stable until the batteries are disconnected, or it shutsd down the drain on the cells, if its allowed to discharge to 28V, you will kill the cells quicker.

I cannot see that your overcharing the cells at 36.5V, as the standard I have shown above that is what we used to work to (Lead Acid, AGM/Gel... Sonneschein - however its spelt)

I would hesitate to guess that your killing the batteries from over discharging them, and causing reliability problems

thanks snaketails.

I aired my concern and supported it by conclusion that the charger was optimized for NiCad's and will not work well with lead acid's. We will be thinking on periodic may be monthly charging/equalizing batteries with external 32V 100A charger to increase reliability of charging system components.

retrofitting back to NiCAd's is not an option due to remained equipment useful life .