Battery - Retro-Renault

**The T.I.B.** · 19th November 2006, 09:55 PM

I'm lucky to get 5 days out of my battery when the car's not been used.
Any tips, any ideas? It's all securely grounded.

If i get a chance i'll leave it disconnected this week to check if the voltage drops on its own.

farnboy16v · 20th November 2006, 12:11 AM

you have got a bad earth somewhere mate check all your earth wires if they are in bad condition replace them.

farnboy16v · 20th November 2006, 12:12 AM

also the alarm system will run down the battery.

terrastudios · 20th November 2006, 07:29 AM

When the car is switched off, disconnect the + from the battery and sit a multimeter inline with the + and the power cable, set the multimeter to current and see how much is being drawn. It is important to note that you should only do this when the car is switched off - a multimeter usually is fused at 10A, trying to fling the car over on the starter with the multimeter inline will upset the multimeter.

Once you can see how much current is being drawn whilst the car is off, you can easily calculate how long the car battery will last. For example, if the battery is 70Ahr, which means I can draw 70 amps for one hour before it goes flat, but it also means I can draw 1 amp for 70 hours before it flattens.

Unless the alarm is physically setting the siren off (false alarms etc..) then I would not of thought it would draw much current as it is likely to only be a MCU, which draw milliamps at the most.

Are you sure the battery is being charged correctly? Run the car up and test the voltage across the battery, it should be near +13.8v. When the battery goes flat, are you charging it with a mains charger? Are you sure the mains charger is fully topping up the battery?

Dependant on the age of your current battery it might be a good idea anyway to invest in a brand new one, and even if its not that, at least you'll have a spare!

Matt.

**The T.I.B.** · 27th November 2006, 06:21 PM

OK after a drive, i turned the car off and checked the battery: 16V according to my multimeter (although the reading started at 13.5 and climbed slowly up, must be a multimeter thing)... so i guess the alt's working fine.

Tried the ammeter in line with the +ve but couldn't get a reading.

I'll leave it all connected and check it every day to see if it's losing charge

**Chris H** · 27th November 2006, 08:40 PM

nope the alts fooked new alt time.

Nothing will be happy at 16V for very long.

Battery will probably have moisutre at the top of be swollen as well if you look

**The T.I.B.** · 27th November 2006, 08:57 PM

do i open up the battery? everything's fine and dandy from the outside

**Chris H** · 27th November 2006, 10:55 PM

no where did you get that from?

**The T.I.B.** · 27th November 2006, 11:05 PM

Well there's no signs of moisture or swelling at least. Always a possibility my multimeter might be playing up.

I'll check the voltage when the alt's running. Besides that, I could stick a new battery in i guess but i was hoping i'd make do with this one.

terrastudios · 28th November 2006, 12:59 AM

If youve not changed the 9v (usually) battery in your multimeter in a while this might be a good idea, you tend to get weird readings when the battery in the multimeter is getting a bit iffy.

If you do suspect the meter, why not go and get a spare, maplins etc.. usually have them on sale for £2.99 or something daft (also check eBay). Handy things to have about.

**The T.I.B.** · 28th November 2006, 09:20 AM

well i did try but the maplins i went to they started at £14, think they'd sold out of real bargain basement ones. and i ain't paying that for a multimeter so i thiought i'd wait and pick up one for a fiver somewhere else!

**The T.I.B.** · 28th December 2006, 07:16 PM

Multimeter needed new battery.

I'm getting about 0.4A flowing with eveything off (apart from clock and central locking i spose). This seems a bit more than ideal but shouldn't run down the battery too quick

**hooverphonique** · 30th December 2006, 04:34 PM

well, a 50 Ah batt will last around 5 days at 0.4A, so that fits with what you say..

**The T.I.B.** · 30th December 2006, 06:21 PM

thanks.

Now got a bigger battery (cheers again bbracer

) and i'll re-wire the terminal connections which i think will improve starting.

bbracer16valver · 30th December 2006, 06:49 PM

and no pink lights

ya woofter

20th November 2006, 07:29 AM	#4 (permalink)
terrastudios Membre Join Date: Oct 2006 Location: County Durham Posts: 147	When the car is switched off, disconnect the + from the battery and sit a multimeter inline with the + and the power cable, set the multimeter to current and see how much is being drawn. It is important to note that you should only do this when the car is switched off - a multimeter usually is fused at 10A, trying to fling the car over on the starter with the multimeter inline will upset the multimeter. Once you can see how much current is being drawn whilst the car is off, you can easily calculate how long the car battery will last. For example, if the battery is 70Ahr, which means I can draw 70 amps for one hour before it goes flat, but it also means I can draw 1 amp for 70 hours before it flattens. Unless the alarm is physically setting the siren off (false alarms etc..) then I would not of thought it would draw much current as it is likely to only be a MCU, which draw milliamps at the most. Are you sure the battery is being charged correctly? Run the car up and test the voltage across the battery, it should be near +13.8v. When the battery goes flat, are you charging it with a mains charger? Are you sure the mains charger is fully topping up the battery? Dependant on the age of your current battery it might be a good idea anyway to invest in a brand new one, and even if its not that, at least you'll have a spare! Matt.

28th November 2006, 12:59 AM	#10 (permalink)
terrastudios Membre Join Date: Oct 2006 Location: County Durham Posts: 147	If youve not changed the 9v (usually) battery in your multimeter in a while this might be a good idea, you tend to get weird readings when the battery in the multimeter is getting a bit iffy. If you do suspect the meter, why not go and get a spare, maplins etc.. usually have them on sale for £2.99 or something daft (also check eBay). Handy things to have about.