13.9 at alternator 12.8 at leisure battery with engine running. (1 Viewer)

[grahammay2]

12.4 at leisure battery without engine running. This is on an autosleeper Broadway fb 62 plate. Anyone with some knowledge of this would be very handy.
Graham

 

[funflair]

Sounds about right I imagine, depends a bit on the size of the cable to the leisure batteries but at 12.4 they will be sucking the power up hence only showing 12.8, it should go up as the charge goes in.

Martin

 

[grahammay2]

My problem is the LB is hardly charging at all from alternator, it does charge fine from ehu.

^{_{Subscribers  do not see these advertisements}}

 

[Guigsy]

Could the batteries be linked via a diode? They cause quite a lot of voltage drop.

 

[tonyidle]

The alternator is low output. Measure on the starter battery with the engine running - it should show at least 14.2v.

 

[grahammay2]

I've no idea about diode thought.

^{_{Subscribers  do not see these advertisements}}

 

[funflair]

Quite possibly the cable to the Leisure batteries is too small so the alternator sees the starter battery as being charges and then starts to reduce its charge output, how long are you giving it to say that it doesn't really charge.

Martin

 

[Guigsy]

This page suggests that if you are split-charging with a diode driven device, 1v difference is typical:
http://www.12voltplanet.co.uk/split-charging.html

 

[Wagoneer]

The output from the alternator should be 14.4v and a similar voltage should be recorded at the leisure battery although possible slightly less if you've got the fridge working on 12v with engine running.

Suggest you initially connect a test lead between engine block and a good chassis earth point and check LB voltage with engine running. If no improvement then further testing can be carried out as indicated on the following link by Aandncaravan services under "Suggestions on how to check the effectiveness of various earth points": http://www.aandncaravanservices.co.uk/add-a-second-battery.php

^{_{Subscribers  do not see these advertisements}}

 

[Flamenca]

@grahammay2 I would check the connections to the alternator. I had a similar problem a number of years ago and found one of the cable connections partially 'burnt out' and when I replaced the connector all was good.

 

[Mike800966]

Dont forget that by using a voltmeter you can measure the voltage drop between the ends of the LB Feed cable from the alternator, if you are only getting a rise of 0.4v (12.8-12.4v)between engine off and engine running then thats not going to push much current into the battery. Bear in mind that the earth returns are also part of the circuit as already mentioned, again the voltmeter might give you a clue

Mike

 

[soreeyes]

I was told by my dealer when the engine is running the starter battery gets priority then charges the leisure battery and when on EHU the the leisure battery has priority and then the starter battery charges .

^{_{Subscribers  do not see these advertisements}}

 

[funflair]

I was told by my dealer when the engine is running the starter battery gets priority then charges the leisure battery and when on EHU the the leisure battery has priority and then the starter battery charges .

That sounds about right to me, although not all motorhome chargers charge the starter battery on hook up.

Martin

 

[mitzimad]

the alternator isnt that clever it sees both batteries as one its just the distance and resistance that will down grade the charge to the leisures
if you have a larger vehicle with tandem batteries you dont get one charged and one not

 

[Richard n Ann]

When our fridge is switched to battery with the engine running the charge to the leisure battery drops. It's normal and caused by thin cable which let's the voltage drop.

^{_{Subscribers  do not see these advertisements}}