# Leisure Battery Not Charging Although Receiving Voltage



## Micro Camper (May 26, 2020)

Hi all, I'm pretty new to all this so please forgive me if this has been mentioned before. However I couldn't find anything relating to this exact problem. So here goes, I recently did a micro camper conversion and the leisure battery is not charging. I can't work out why. I have installed a voltage sensing split charge relay which comes on when I start the engine and supplies voltage to the leisure battery. I have also installed a battery indicator which displays both the voltage and the battery percentage. I can start the engine and leaving it running for a while or take the van on a long drive but the battery doesn't seem to charge, in fact it might lose 1% or 2%. I've instead been charging the battery with a battery charger that plugs into the mains, and that seems to work fine. When I look at the battery indicator it suggests that the battery is charging fine from the mains. 
So I'm rather confused. If the battery is receiving voltage from the van battery through the voltage sensing relay then why should it not be charging?

I would really appreciate any help anyone can offer. And if I've left out any details that may be relevant to solving this mystery please let me know.
Many thanks


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## rayc (Jun 3, 2008)

Any chance of checking the amps flowing into the battery when you think it is charging. It may be receiving a voltage but is there current flowing?


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## EJB (Aug 25, 2007)

Posting the actual voltages under the different situations would help someone to advise you.


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## raynipper (Aug 4, 2008)

Often an earth poor contact. But just guessing with the limited info.

Ray.


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## Penquin (Oct 15, 2007)

When charging the voltage at the leisure battery should be 14.4v approximately. Is this what you are finding ? If not it suggests a break somewhere or a circuit preventing the charging by eg a poor connection or a component failure.

More details are needed of voltage at battery terminals when engine is running.

Also voltage at various places in the charging circuit, with the engine OFF for more than 30 minutes, check the battery voltage again (should be around 12.6 - 13 volts )

Check the split charge relay is wired correctly - again, a voltage checkis needed.

Check the current using an in line ammeter for an accurate result. If the voltage is correct the current should be OK, unless there is a thin wire in the circuit refusing the current (and creating a fire risk as it heats up).

Do come back with some more details as I am sure many people will be keen to help. My knowledge has come from many years of working on motor vehicles, retiring a caravan and now playing around with the wiring on our motorhome when we want to modify things, coupled with a science background....

.


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## Micro Camper (May 26, 2020)

Thanks for all your advice so far. So I ran the engine today for 15 minutes checking the voltage running to the leisure battery at regular intervals, it remained at 14.2v throughout. Leisure battery voltage after the engine had been off for 30 minutes was the same as before I started the engine - 12.7v. All the wires are relatively thick and short, 16mm and no more than 3 meters from the main battery to the leisure battery. And I'm pretty sure the earth connection is ok. 
Rayc do you know how I might check the amps flowing into the battery rather than just the voltage?


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## Penquin (Oct 15, 2007)

If you have 12.7v 30 minutes after running, IMO your battery is fully charged

https://mashley1975.files.wordpress.com/2015/06/screenhunter_02dec051817.gif

To check the current flowing you EITHER need a heavy duty ammeter in series in the circuit to charge or you can use a meter that surrounds the chargibgvwire (usually red for positive) and measures the electrical field it produces, the higher the current, the higher the field strength.

I believe these "wrap around" meters give a reasonable result at high currents, but are not so accurate at low Ines eg less than 5a.


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## rayc (Jun 3, 2008)

Micro Camper said:


> Thanks for all your advice so far. So I ran the engine today for 15 minutes checking the voltage running to the leisure battery at regular intervals, it remained at 14.2v throughout. Leisure battery voltage after the engine had been off for 30 minutes was the same as before I started the engine - 12.7v. All the wires are relatively thick and short, 16mm and no more than 3 meters from the main battery to the leisure battery. And I'm pretty sure the earth connection is ok.
> Rayc do you know how I might check the amps flowing into the battery rather than just the voltage?


Then the battery is charged. On the face of it your system is working . Why not discharge the battery by leaving the lights on for some hours. Check the voltage and when it gets to 12.3v or so rerun your test and see how long it takes to get back to 12.7v after receiving the alternator charge? It is not worth checking for current flow as with 14.2v applied to a fully charged battery it will be negligible.


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## bc109 (Sep 17, 2016)

Errrrrrr......these "wraparound" meters, otherwise known as clamp meters will only measure AC currents, not DC currents, unless you have a special, very very expensive one not worth buying.

To measure AC, you need to split a two core or three core mains lead to clamp the live or neutral wire only otherwise the live and neutral magnetic fields will cancel each other out and produce no reading whatever.
Bill


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## Penquin (Oct 15, 2007)

bc109 said:


> Errrrrrr......these "wraparound" meters, otherwise known as clamp meters will only measure AC currents, not DC currents, unless you have a special, very very expensive one not worth buying.
> 
> To measure AC, you need to split a two core or three core mains lead to clamp the live or neutral wire only otherwise the live and neutral magnetic fields will cancel each other out and produce no reading whatever.
> Bill


Thank you for that, it sounds exactly correct, they are NOT something I have ever used, although one was suggested to me, now I know it's not worth worrying about. I have only ever used an in line meter but have never really been concerned with charging value other than from our solar panels where the feed current is displayed by the gizmo.


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## Micro Camper (May 26, 2020)

I recently charged the battery with the mains charger so it is pretty full. It's at 86% at the moment. When it's fully charged it reads 12.9V.


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## peribro (Sep 6, 2009)

My batteries are generally 12.7v when fully charged and have been allowed to rest for a while - 24 hours or so.


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## Penquin (Oct 15, 2007)

Micro Camper said:


> I recently charged the battery with the mains charger so it is pretty full. It's at 86% at the moment. When it's fully charged it reads 12.9V.


I suspect that with the charger still operating or after it has been disconnected/switched off for at least 30 minutes ? That is the recommended time to read the voltage as has been said before by several people.

If it is reading 12.9v have you calibrated your meter in any way ?

A difference of 0.2v would not be significant to me. Generally a significance value of + or - 5% is a commonly accepted value, which for 12.9v would be + or - 0.6v.

That is my way of thinking anyway. If I was you I would probably accept what you have until something indicates a major problem.


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## Micro Camper (May 26, 2020)

I have two devices which test the voltage at full capacity and both say 12.9V. One of them also has a battery percentage indicator. But regardless of that the problem still stands that the battery is not charging from the main van battery. The voltage is pretty good at the moment due to me charging the leisure battery from the battery charger I plugged into the house mains electricity. But prior to that, and now, when I drive the van or start the engine the battery doesn't seem to charge. The battery reader and other voltage indicator I have both stated 12.9V at full charge and subsequently the battery percentage reader stated 100%. Now it's at 84% and 12.7V. After I drive the van for 30 to 45 minutes nothing changes. Same as before I charged the battery at home (but with different readings).

Please let me know if I haven't been clear but I've tried to describe it the best I can.

Thanks


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## Penquin (Oct 15, 2007)

Have a look at the picture on the link I posted earlier, 12.7v IS fully charged if you are getting a reading of 12.9v was that obtained after the charging system, whatever it was - the alternator or the battery charger, has been switched off for AT LEAST 30 minutes ?

Your gauge saying the % may well be where the misinformation comes from, 12.7v is fully charged.

The ONLY way that I know of to reliably check whether the alternator is charging, assuming that you have checked the operation of anysplit charge relay, is to partially discharge using a light for instance, so that the voltage drops to say 12.3v and THEN try driving to test the charging, once again waiting at least 30 minutes after stopping any potential charging, then test the voltage which should now be higher than the 12.3 earlier.

If it gas gone up, the charging system is working correctly, if not there MAY be a fault. BUT, it takes a long drive to raise the charge - typically several hours to restore full charge. The reason for the slowness of the charging is due to characteristics of the control system for the alternator which primarily recharges the vehicle battery until it is fully charged, it then reduces the output from the alternator which is what slowly charges the leisure battery.

It is possible to fit a larger alternator or modify the charging control system, but suchbthings are beyond me although they have been discussed on here many years ago I think.

30 - 40 minutes charge will make little difference to the leisure battery charge as I have said, during that time the charge drained from the vehicle battery for starting is being replaced only then will current trickle into the leisure battery.

The leisure battery should not change on starting the vehicle,nthat is why there are two batteries.

.


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## rayc (Jun 3, 2008)

My guess is that the alternator regulation is 'seeing' that the cab battery is charged. The leisure battery, due to the size and length of the connecting wires, has no influence on this and therefore gets about 2A maximum charge. These systems should only be regarded as maintaining ones and not as a charge from flat especially with a low daily mileage. 
Only my opinion as an amateur of course. I was though a radio engineer in the Army and our radio vehicles were specially equipped to charge the comms batteries from the alternator and had hand throttle controls to increase the revs when parked up. It was possible to input 16A into the comms batteries independent of the state of charge of the cab battery. I suspect the OP's simple split charge system is nothing like that and as I said perhaps 2A max.


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