Battery charger 2

[garciaf]

There is a control panel (Diesel engine fire pump controller, FTA1100-J). This panel have 2 battery chargers, for 2 two battery banks one charger for each one). Each battery bank is compoused of 2 battery of 12V each one connected in series in order to give 24 V output to the starting motor of diesel engine. The battery voltage selector is set of in 24 V, and the battery type selector lead acid

The battery of diesel engine is Yokohama model N200 12 V 220 amp-hrs.

I have seen that floating charge is about 0.1-0.2 A, but the fast charging sometimes 4 amp, 5 amp, other days 8 amp or 9 amp, but everyday supply fast charging several times, for me this is not correct. the first batteries were damaged so we change all and put new.

for me is not correct this fast current everyday because this can damege the battery, the vast majority of time the voltage is high around 28 or 29 V, when is necessary to have 25 or 26 V, normally, sometime the battery rise up to 30 V and is injecting 4-5 amp.
I dont know what to do, the electrical engineer doesn't seem to know anything about it, and I'm worried about because this system is critical, in proper conditions.

please help

 

[RRaghunath]

These batteries used for Diesel engine cranking do not operate on float mode all the time. Large current demanded by cranking motor during Diesel engine starting comes from the battery (the charger is not sized that big to supply this current).
Hence, depending on how frequently the diesel engine is started, the battery fast charging current can go high, as the battery is partially drained with every start.
Could you not control frequent starting of the diesel fire pump!!
I understand once a day trial may be a mandatory requirement, to confirm the readiness of the vital equipment.

Rompicherla Raghunath

 

[garciaf]

the fire pump diesel engine is tested semanally in order to take their operating parameters.
between this days the motor is static. in the attached image the motor is not working and see the amp supply later this goes to 0.3 amp and continue all day long. see the voltaje is high there are batteries of 12V in serie= 24 V, but not 28 or 29 V. this can damage the battery.

 

[ScottyUK]

Why do you think 28V will damage the battery?

12V batteries normally float charge at about 13.8V, with cyclic charge usually being about 14.4V. For a 24V nominal system these volatges are 27.6V and 28.8V respectively. Your charger voltages don't look far off.

Check the actual charge voltage using a calibrated multimeter rather than relying on the controller display, and if necessary trim in the charge voltage. Before changing anything, make sure you know understand how to adjust the battery charger and also know what the correct charge voltages are for your battery. I'm not convinced you need to adjust anything.

 

[3DDave]

I think excess charge current goes to electrolysis of water into hydrogen and oxygen. I don't know of any harm that can happen to a lead acid cell once all the lead sulfate is converted to lead and sulfuric acid aside from water heating and water loss. You can check water levels and for the presence of combustible gasses and observe if bubbles are forming on the plates where visible through the battery fill caps. You can also check for proper acid composition with specific gravity testers or pH meters.

 

[waross]

I used to be called to service a number of residential standby generators. after several years the battery would fail, and I would get a call;
"The lights went out and my set didn't start."
Then I started seeing sets with trickle chargers installed in the control box to keep the battery at full charge.
The chargers extended the battery life for a number of months and then I would get a call:
"The lights went out, there was a big bang and my set didn't start."
On my way to the site I would detour past a grocery store and pick up some baking soda to clean up the acid from the exploded battery.
I started disconnecting the chargers when putting new sets into service.
It seemed like harm to me.
moral:
Check and maintain your water levels. Load test your batteries from time to time and replace batteries in bad condition before they fail.
I wouldn't worry about any charging voltage below about 32 Volts.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Cranking batteries aren't much different to the countless batteries on float charge in numerous other applications. If you set the float voltage correctly and do some basic maintenance then they should last a reasonable length of time. If you don't do those things then your battery will fail.

 

[3DDave]

Was it Generac?

 

[itsmoked]

garciaf; You may be on to something and I commend you for investigating.

Chargers of that type can have three modes of charging:
Bulk, Float, and Equalizing.

Bulk charge, is the mode used after they've been drained a bit and are being re-charged. A 24V lead acid battery will normally be bulk charged to 29.6V. Once a minimal current is reached the charger will switch to Float Mode. Float Mode is a fixed voltage of 27V for a nominal 24V LAcid stack.

Flooded LA batteries that are stationary will eventually have their electrolyte stratify based on specific gravity. This can damage the plates and always reduces the battery's capacity. To fix this a third mode is called upon to stir things up - dramatically. This is called the Equalization Mode. Here, the batteries are briefly over-charged to 32.4V which literally boils the electrolyte for about an hour. This homogenizes the electrolyte and cleans the plates a little.

Often the system fails to provide an Equalize Mode because they're just plain too cheap to provide it. But if it is provided that could explain you seeing +30V. However, I'd expect you to see that only once a month at the most!

If your fire system has had a failure of its power supply that normally runs the control system it may be drawing from the batteries as the normal form of battery backup. This can cause frequent draw-down below what's expected for Float Mode causing the charger to frequently kick into Bulk Mode shoving the voltage back up to 29.6V.

That can also be caused by the Float Mode being unable to supply the steady-state float current which for those batteries, if healthy, would be about 100mA and the controls load current. Correctly adjusted or designed float has to provide enough current to support both loads or the galloping charging you see will occur.

You stated the prior set of batteries had "been damaged". All LA batteries are eventually 'damaged'. I'd expect your batteries in this service to last about 4 years. If you are saying your first batteries lasted less than this time then yes you do have a "problem". If they lasted longer than that then just cycle them out every four years.

To troubleshoot this I'd put a data logger on the battery voltage and watch for a galloping situation where there is a bulk -> float -> followed by the voltage decaying below the float followed by another bulk cycle. This will be very apparent on a day or multi-day data capture. Better is to log the voltage and the current simultaneously as that shows the entire picture.

Barring having a data-logger use a clamp-on DC ammeter and watch for a larger than expected load being drawn from the batteries during the float mode.

Check too for someone having added load to the battery bank.




Keith Cress
kcress -

http://www.flaminsystems.com

 

[FreddyNurk]

waross, I've seen the same with a number of chargers, they're typically the older style that don't do end of charge detection and just sit there charging the batteries (I've even seen units with a 'boost' switch left permanently on) and they sit there overcharging the battery, normally along with some emission of hydrogen and oxygen, until the events you describe happen. If the water level gets low enough due to gas production, really nasty things can happen as there's a nice explosive mixture at the top of the battery waiting for a large current event.

The newer fancy 'multistage' chargers don't suffer from the same problems as they usually shut off after a period and leave the battery alone, only topping up as necessary.

Some chargers (like the ones for forklift or traction batteries) are designed to overcharge and produce gas in order to prevent acid stratification. Using them on automotive cranking batteries is asking for trouble.

EDMS Australia

 

[genhead]

I've come across several "fancy" multi-stage chargers which work fine as long as only the batteries are connected. If there is any standing load at all (controller, PLC etc) then the charger stays in boost mode forever.

 

[itsmoked]

I believe California chargers are required to stop charging after x number of hours. You will see on Amazon, "This charger not for sale in California".

Keith Cress
kcress -

http://www.flaminsystems.com

 

[FreddyNurk]

genhead, I've never designed a system that runs everything off the cranking batteries, but that doesn't surprise me.

I have used some of the isolation modules (Puls makes a couple of varieties, I don't doubt that there are others) and set up power supplies so that the behaviour you describe doesn't happen. All of the systems I've done have had their own system batteries for controller power anyway, although I'd expect that standby generators with permanently connected chargers and controllers would be susceptible to that behaviour.

I've also seen where voltage checks on the battery have shown the charger voltage, not the battery voltage, as the battery has been slowly overcharged, but looks like its fine. Most of the time that gets discovered the first time the power goes out, and so does the battery.

EDMS Australia

 

[Compositepro]

Itsmoked, the California restriction is more likely to be due to a lack of Proposition 65 warning labels on the charger, which deals with cancer causing chemicals.

 

[itsmoked]

Hi Comp. It's much more than that...
[URL unfurl="true"]http://www.energy.ca.gov/appliances/battery_chargers/documents/Chargers_FAQ.pdf[/url]

Or
California-passes-new-regulations-for-battery-charging-systems

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Compositepro]

Well thank you, itsmoked. I had not heard of this (not so) new standard.

 

[waross]

Actually I am not a big fan of battery chargers on engines equipped with battery charging alternators.
The engine driven charging alternator does a good job of restoring the charge when the engine starts and runs.
If the unit is excercised once a month there should be no need for a chearger. You can install a voltage monitoring circuit that will start the charger and send a trouble signal if the battery voltage starts dropping.
With no parasitic drains a starting battery will hold a sufficient charge for several months.
The energy may be better spent on a thermostatically controlled coolant heater.
I have used battery chargers powered by the generator set in a few instances. When the set starts and runs, the battery charger recharges the battery. Works fine.
If the set sits for several months I may connect an external charger for a few hours.

Bill
--------------------
"Why not the best?"
Jimmy Carter