Emergency Lighting Central battery system design

[stescott1]

Hi All,
I am new to this site so be gentle please....

My question is this... I have been to an existing job which has 55 slave EMLs throughout the building. We are experiencing volt drop on the longer routes with the LED fitting, approx 40 lights. The LED fittings start to strobe as they hit below about 22vdc. The batteries in the unit are 2x 100Ah batteries and the load of the existing lights is approx 14.5A.
I was wondering how I can ramp the voltage up to 30vdc when on load. I was thinking say 6vdc batteries but not sure how to work out the Ah rating etc.
My question is, is it ok to mix the sizes of the batteries inside the unit i.e. 2x 100Ah and 1x 15Ah or do I have to replace them all for alike?

If there is anyone with this type of knowledge or experience please point me in the right direction is possible.

Many thanks
Stescott1

 

[ImpededLoop]

I would start by contacting the manufacturer to ensure you're within the limit for the number of luminaires for the charger/batteries.

If that is ok, you then need to calculate the required cable sizes which should then be compared to those that have been installed.

 

[tazz]

Suggest then problem lays in battery capacity more than voltage drop. Batteries need load testing

 

[HandySparks]

I don't think that adding an additional battery in series with the others is the answer, particularly one of a lower capacity. The lower capacity battery will be dead when the others are only partly discharged. You might also exceed the maximum permissible voltage for the lighs.

What's the voltage at the batteries when the lights are getting 22V?

 

[tazz]

As previous, you need to do some testing.....check voltage of batteries off load, Should be 27.6 volts. Then check batteries on load, should be aprox the same. If 22v then batteries require load testing. Batteries will only last between 5-7 years with constant charging. And voltage decrease will occur when battery capacity is low, on load.

 

[stescott1]

Thanks for the answers.
The batteries are new and are about 27v on and off load. I have a circuit which is not too long and lights work fine. It seems to be that they flicker around or below 22v. I have load tested the batteries and they pass. I have contacted the manufacturer of the fittings and he has done a batt calculation, the result was the existing batteries are over sufficient for the 3 hour duration. The fittings also should work up to 30vdc, I have been told.

My only other idea was to have 5 6vdc batteries all at 15Ah capacity which will work but I'm not sure for how long. Any ideas??

Thanks again for the posts.

Steve

 

[tazz]

If you are getting 27v off load and 27v on load....then you have a big problem if your stating 22v at the light fittings, thats a 5v loss in cable run

 

[stescott1]

I know its a big drop...
I am not sure of the cable run lengths of 4 of the circuits.
I may have to run new cables for the additional fittings we installed! maybe this might help if I run them in 2.5mm FP.
Cant think of any other ways around it....

 

[tazz]

I would start breaking up the circuits, and continue testing. You need to prove the cables and their terminations in each fitting. Incase there is a manufacturing fault with the fittings....so one step at a time, if you can link the fittings out, even better. You can conduct a full insulation and r1 + r2 test.

 

[davesparks]

Does it work properly if you disconnect the additional fittings you installed?

 

[ImpededLoop]

I may have to run new cables for the additional fittings we installed! maybe this might help if I run them in 2.5mm FP.

If the existing luminaires worked before you added some, this is likely to tbe your best bet.

 

[Risteard]

Normally when doing central battery system emergencies 2.5mm2 FP200 is used throughout due to volt drop issues. (The luminaires are likely 24Vd.c.) 1.5mm2 may be used to tee off for a fitting, but certainly I wouldn't be wiring multiple fittings in 1.5mm2.

 

[bossian]

Out of curiosity, were the original fittings 8w fluorescent's? I've known the old type too work happily on long runs with voltages down to less than 20v. It maybe the LED type are much more voltage critical?

 

[Engineer54]

Never seen a central emergency battery system with just two batteries...
The central battery systems we have, require substantial storage racking in an Ex Zone room to house the batteries!!

 

[tazz]

The type you have E54 is to supply essential db boards at inverted 230v. Boards will possible supply em lighting, fire alarm, va, firemans lift etc. Usually large inverter cabinets, with stacked batteries, dotted around the building, or lined up in on large vented room.
These 2 battery em packs, are basic power supplies solo for 24v em lighting, good enough for aprox 100 x 8w bulkhead for 3 hours

 

[stescott1]

This is something I haven't checked. Although The existing fittings are 8w fluorescents which is why we haven't seen any problems until fitting LED.
Thanks Ill try this tho.

 

[ImpededLoop]

Do the LEDs work if you connect them directly to the batteries eliminating any volt drop on the cabling?

 

[tazz]

This is something I haven't checked. Although The existing fittings are 8w fluorescents which is why we haven't seen any problems until fitting LED.
Thanks Ill try this tho.

You are using 24v led bulkheads ...? if yes, then check all cable runs, as I suggested, then we can look at compatibility of led

 

[stescott1]

Do the LEDs work if you connect them directly to the batteries eliminating any volt drop on the cabling?

Yes they do there doesn't seem to be a problem with the fittings themselves. I think like Bossian said the LEDs may be more sensitive to voltage drop. Some of the 8w existing fittings are further down the line than the LEDs and seem to work fine.

Im starting to think Ive F'd this job up putting the LEDs in instead of 8w bulkheads.

 

[stescott1]

You are using 24v led bulkheads ...? if yes, then check all cable runs, as I suggested, then we can look at compatibility of led

Yes they are 24v LEDs. I will try splitting them up and then if that works I can wire the LEDs on a dedicated line.

Wish me luck....