Drop in voltage when lights on

An alchemy of sparks, copper wire and earth

Moderators: Moderators, User administrators

Post Reply
TONYT25T25
Posts: 881
Joined: 16 Sep 2013, 17:19
80-90 Mem No: 13596
Location: Hampshire

Drop in voltage when lights on

Post by TONYT25T25 »

I recently replaced my fluorescent strip lights with a much brighter LED strip light, more for a bit of a project than necessity, however the LED are extremely bright compared to the original fluorescent ones. They are connected to the leisure battery and out of curiosity I connected a Multi meter to the battery to check how much drain there was when they were on.  The battery read 12.62V and on switching on one of the strips the reading dropped quite rapidly and kept on dropping, ie 12.61, 12.60 and so on as I watched it. I expected a drop but not so quickly, anyway switched off the lights and the battery regained its original voltage quite quickly.  Is this normal operation, I have no comparison as did not to the same check with the fluorescent lights.
1984 Campervan 1.9DG Petrol WBX

User avatar
ZsZ
Posts: 873
Joined: 12 Feb 2009, 16:28
80-90 Mem No: 14899
Location: Budapest, Hungary
Contact:

Re: Drop in voltage when lights on

Post by ZsZ »

It is normal to have a drop in the battery voltage when some load is added on.
The voltage should drop and be steady for a while on a lower level if the load is not huge and the battery is OK.
I am sure that the fluorescent lamps draw more and the voltage would drop to a lower level.
Zoltan
1986 Multivan ex-Caravelle. Van since 2006, running mTDi 1Z since 2008 with Fiat Croma 1.9 TDid pump 2008-2019, custom pump since 2019
5spd custom box 4.57 diff + 0.74 5th

TONYT25T25
Posts: 881
Joined: 16 Sep 2013, 17:19
80-90 Mem No: 13596
Location: Hampshire

Re: Drop in voltage when lights on

Post by TONYT25T25 »

Thanks, next test I may leave them on for a bit longer and see how far the voltage drops, within reason of course.  Only use them when off grid and have a small solar panel as a backup trickle charge.
1984 Campervan 1.9DG Petrol WBX

User avatar
Robsey
Posts: 310
Joined: 19 May 2012, 20:45
80-90 Mem No: 11137
Location: East Manchester

Re: Drop in voltage when lights on

Post by Robsey »

I am sure the current rating should be written on any sales blurb or packaging.

Modern LEDs can use a lot more current than early simple LEDs.
It is not unusual to find multiple 1 watt LEDs, as used on daytime running lights etc.
Not much less currant than normal filament bulbs used in the same context.

Being that the leisure battery is supplying the voltage, at least you know that you would not killing the "starter" battery. So more an inconvenience than a major hassle if you do drain the battery.

It also depends on many factors like size (capacity) and age of the battery in use.
They all weaken over time... especially if not attended to / charged once a month.

Lockdown has caused a lot of battery issues due to lack of use...
1983 Tin Top with a poorly DF and 4 speed DT box.
Soon to have a whizzy 1987 DJ.

Post Reply