Battery going flat

[sparky Paul]

35mA sounds within the realms of normal.

The amp hound is a great little tool, they can quickly give you a pointer to where any parasitic drain is going - next best thing to a crystal ball. The only drawback is that they are not cheap for something you might use very rarely.

You can do the same job with an accurate digital voltmeter, a lookup chart and a bit of head scratching. Not as quick as the amp hound, of course, but just as effective. There are various charts around, they are all pretty similar - I can find one out and add it here if anyone is interested.

[UKjim]

To be honest £59 is less than an hours labour at most garages, so money well spent and I can always loan it out to any one local who has a similar problem.

[Jocko]

I can find one out and add it here if anyone is interested.

That would be good.

[sparky Paul]

I can find one out and add it here if anyone is interested.

That would be good.

Your wish, etc., etc..

Attached, two charts - 0-4.9 mV and 5-10 mV - handy to print them out if possible.

Using a digital multimeter on the lowest DC volts range, measure the voltage across the contact on the top of the fuse, find the value on the left of the chart. Find the type of fuse on the top, and cross reference - the value in the box is an estimate of the current flowing through the fuse in mA.

It's exactly the same principle used by the 'amp hound'. Not perfectly accurate, as fuse resistance does vary a little, but good enough to give you an indication of where any likely problem is.

[culzean]

Despite the battery tester telling me the battery has good health, am I right in thinking suspicion is on a duff battery?

Not possible to really test a battery in the short time most places do it,  they only test CCA, which is only part of the story,  it is hard to test charge acceptance and reserve power ( Ah ).  If a battery has been allowed to remain below 70% charge for any length of time sulphation is a real risk, and 70% is about 12.4 volts,  which is why I am replacing my 5 year old motorbike battery as it settles at 12.4 volts a few days after fully charging,  and I know there is no parasitic drain.

Fitted new Yuasa battery to motorbike today ( to replace the OEM Furukawa ) and tested the voltage etc.  Battery actually reads 12.7 volts with no load,  drops to about 12.4 when I put a load on it by turning ignition key to on position (headlights and sidelights on, ECU, fuel pump etc. ) but quickly recovers back to over 12.6 when load removed. Even though I thought the bike was starting OK  with 5 year old battery ( OK engine spinning over slightly slower than I remember when new ) I was genuinely surprised how quickly bike starts now    Problem is that batteries fail so slowly that you get used to it,  and it is only when you slap a new one in that you see how they really should behave.  The 5 year old battery on bike dropped below 12 volts when ignition was turned on without engine running, and only recovered to about 12.3volts very slowly, and as said before a few days after a full charge was back down to 12.4.

As embee said, treat a battery as a consumable

[t0m]

Just as a side post .....

I remember a post on the Civic site from a dealer who said that when you lock the car you should always double lock via the keyfob second press.

The second press, as well as deadlocking, also shuts down all unneeded circuits. If you don't deadlock then some circuits are left open.

Whether the Jazz is the same ?

Thanks for the idea. I just tested and unfortunately there's no difference to the current drawn whether the car is unlocked, locked or double locked.

[t0m]

If you are thinking of replacing the radio, why not take the opportunity of updating it to a modern double din with CarPlay or Android Auto? I have just installed an excellent unit from Amazon which performs really well and looks so much better. Have a look at my post in the ‘in car entertainment’ section.

I bought the cheapest car stereo I could find on eBay just to prove if it was the factory-fitted radio drawing excessive current or something else on the "Back up" circuit. With the new stereo fitted the current draw is too small for my meter to read so that is pretty conclusive. Time for a replacement!

@UKJim How much was that double DIN unit from Amazon?

I don't want to spend a huge amount as the car is 17 years old. It only has 77K miles on it though so I should think it will last a couple more years.

[UKjim]

£170, but currently out of stock. you will need the fascia and a Connects2 wiring loom, all in probably about £230-£250

[E27006]

Despite the battery tester telling me the battery has good health, am I right in thinking suspicion is on a duff battery?

Not possible to really test a battery in the short time most places do it,  they only test CCA, which is only part of the story,  it is hard to test charge acceptance and reserve power ( Ah ).  If a battery has been allowed to remain below 70% charge for any length of time sulphation is a real risk, and 70% is about 12.4 volts,  which is why I am replacing my 5 year old motorbike battery as it settles at 12.4 volts a few days after fully charging,  and I know there is no parasitic drain.

Fitted new Yuasa battery to motorbike today ( to replace the OEM Furukawa ) and tested the voltage etc.  Battery actually reads 12.7 volts with no load,  drops to about 12.4 when I put a load on it by turning ignition key to on position (headlights and sidelights on, ECU, fuel pump etc. ) but quickly recovers back to over 12.6 when load removed. Even though I thought the bike was starting OK  with 5 year old battery ( OK engine spinning over slightly slower than I remember when new ) I was genuinely surprised how quickly bike starts now    Problem is that batteries fail so slowly that you get used to it,  and it is only when you slap a new one in that you see how they really should behave.  The 5 year old battery on bike dropped below 12 volts when ignition was turned on without engine running, and only recovered to about 12.3volts very slowly, and as said before a few days after a full charge was back down to 12.4.

As embee said, treat a battery as a consumable

A new battery is good for the voltage regulator unit of a motorcycle, old tired batteries need a lot of charging which can overheat or damage the regulator unit. Certain Honda and Suzuki motorbikes were prone to such damage which could also burn out the alternator wiring.   A new battery will save you money in the long-term. Also if you have a very discharged  battery,  it is good practice to remove it to recharge with a  mains charger and not use the  vehicle alternator, this applies to cars as well as motorbikes

[culzean]

A new battery is good for the voltage regulator unit of a motorcycle, old tired batteries need a lot of charging which can overheat or damage the regulator unit. Certain Honda and Suzuki motorbikes were prone to such damage which could also burn out the alternator wiring.   A new battery will save you money in the long-term. Also if you have a very discharged  battery,  it is good practice to remove it to recharge with a  mains charger and not use the  vehicle alternator, this applies to cars as well as motorbikes

With a standard 'shunt' RR ( rectifier / regulator ) as fitted to most bikes the permanent magnet rotor alternator is always working flat out, with no way to control actual output of stator coils,  the 'shunt' ( parallel ) regulator shunts any 'unused' (not being used by bikes headlights, ignition etc ) current down to earth ( common or battery negative ) and excess heat is dissipated by the RR heatsink.  I fitted a 'series' Electrex RR to my latest bike ( this switches the power from generator on and off like  light dimmer to match the power needs of the electrical system ) - the 'series' heatsink runs 30 deg C cooler than the OEM 'shunt' type,  which ran at over 70deg C,  and the stator coils of the generator will also be running a lot cooler.  The problem with the shunt type RR is that if you fit say LED headlight to the bike which draws 3 amps less than the filament one, that is 3 extra amps that have to be shunted though heatsink, rising heatsink and electronics temperature, and the stator coils see no drop in demand.   Car alternators have a much more sophisticated wound rotor on which 'magnetism' can be varied and is used to control the output of the alternator to match demand.   

[UKjim]

As a point of interest it certainly looks like my new Yuasa battery has cured my problem.


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