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Home > Technical > TD5 Denso Alternator Voltage
What voltage does your alternator produce at cold start? (measured directly at battery terminals)
Less than 13.5v
10%
 10%  [1]
13.5v to 14.0v
0%
 0%  [0]
14.1v to 14.4v
50%
 50%  [5]
14.5-14.8v
40%
 40%  [4]
More than 14.8v
0%
 0%  [0]
Total Votes: 10

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rallysteve



Member Since: 10 Feb 2014
Location: South Yorks
Posts: 2194

United Kingdom 2002 Defender 110 Td5 DCPU Keswick Green
TD5 Denso Alternator Voltage
All, I now have very accurate voltage measurement in my TD5 which I have noticed reports a charging voltage of 14.8v when the engine is first stated from cold. This voltage seems to drop back down to 14.3v when the engine has warmed up.

This voltage really is too high and risks damaging batteries through overcharging. I am interested to know what voltage other peoples TD5 alternators produce when started from cold.

I have attached a poll to try and find out.

Cheers,
Steve 02' 110 TD5 Double Cab Rebuild Thread
84' 90 3.9 V8 Caged Pickup Build Thread


Mobile Diesel Heater Build Thread
Post #679197 17th Jan 2018 10:36am
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ericvv



Member Since: 02 Jun 2011
Location: Near the Jet d'Eau
Posts: 5816

Switzerland 2009 Defender 110 Puma 2.4 SVX Station Wagon Santorini Black
Post #679200 17th Jan 2018 10:54am
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Harry.O



Member Since: 25 Jul 2014
Location: Warwickshire
Posts: 704

United Kingdom 1989 Defender 90 300 Tdi ST Nato Green
Having fitted a brand new Denso unit to the TD5 the other week, cold start (but possibly with heater on) was 14.5V measured across the battery terminals. 2005 Td5 110 Hardtop
1989 300Tdi 90 Soft top
1992 200Tdi 90 Truck cab with Land Cruiser axles
Post #679202 17th Jan 2018 11:02am
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miker



Member Since: 13 Sep 2015
Location: Surrey
Posts: 1758

United Kingdom 1999 Defender 110 Td5 CSW Rioja Red
Up to 14.5V when really cold, gradually drops down to around 13.8-14.0
Post #679215 17th Jan 2018 11:44am
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Mash



Member Since: 09 Feb 2015
Location: Guernsey
Posts: 1674

Guernsey 1998 Defender 90 300 Tdi HT Nato Green
14.5-14.8 is about right, the 24v systems I work on often produce 28.8 volts to charge the batteries with no ill effects. 90 wolf - Jasmin http://www.defender2.net/forum/topic39408.html
90 V8 - Maggie http://www.defender2.net/forum/topic42564.html
110 TD5 - Buggsy http://www.defender2.net/forum/topic59029.html
52HG25 lightweight https://www.defender2.net/forum/topic72342.html
D3 Hse - Fiona
Capri 2l S - Anna

Think I might have a problem............
Post #679236 17th Jan 2018 1:01pm
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MadTom



Member Since: 10 Sep 2013
Location: Olomouc
Posts: 556

Czech Republic 1999 Defender 130 Td5 HCPU Baltic Blue
It is standard, that alternator output voltage is temperature dependent - when really cold the voltage is higher, and drops, when the alternator temperature rises. The same is with batteries - in when cold they need higher charging voltage for proper fast recharge after starting engine. It is because the chemistry in battery is slower in lower temperatures, so it need more energy (higher voltage) for work.
This is not a problem for short time after engine start, but for long run it is not good.
And one remark - "standard cheap board voltmeters" are all but nu quite accurate, and in high or low temperatures it is even worse. IT is good to check their accuracy with some high quality voltmeter/multimeter, just to be sure, that they work correctly. The same problem is with cheap multimeters. "Drobek" = The Small One - Discovery 2, "BlufĂ­nek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo Smile
Post #679258 17th Jan 2018 1:58pm
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sako243



Member Since: 08 Jul 2014
Location: Wales
Posts: 1184

Wales 1994 Defender 110 300 Tdi CSW Alpine White
Where's your reference for 14.8V is too high? It's precisely the right voltage for charging a typical lead acid battery in most situations.

Reference, Google lead acid battery charging, that and a masters project in it Razz Ed
82 Hotspur Sandringham 6x6
95 Defender 110 300Tdi
Post #680494 21st Jan 2018 6:02pm
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JWL



Member Since: 26 Oct 2011
Location: Hereford
Posts: 3443

England 2002 Defender 110 Td5 SW Coniston Green
Mine can often be seen charging at 14.8V both on the Nanocom as well as the monitor directly wired to the battery posts, seeing as the battery is still the factory fitted one it hasn't done it any harm. Mine was built in January 2002 Thumbs Up
Post #680550 21st Jan 2018 8:25pm
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