Vehicle battery not charging when hooked up.

AlastairH

AlastairH

Joined
Apr 10, 2017
Posts
128
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70
Location
Dunfermline
Funster No
48,116
MH
Bessacarr E520
Exp
Since 2013
Our motorhome has been in store for all of this year and hooked up to keep the batteries charged. In June I discovered that the vehicle battery had gone flat. It was quite old so I assumed that it had simply expired and I replaced it. Much to my horror, I have discovered that the new battery is now flat. I should mention that the vehicle battery and leisure batteries are maintained through the Sargent electrical unit which has worked fine for years and that the leisure batteries are fine.

Can anyone suggest what the problem might be?
 
Have you got a switch that selects or priorities one battery or the other.
 
Thanks for your response.

Not that I am aware of. I have the Sargent unit set to Smartcharge which determines battery condition of the vehicle battery and leisure batteries and keeps the batteries in good condition.
 
You don't mention you leisure battery's, are they charging on ehu
 
Yes, the condition of the leisure batteries is good. It looks like the power is not getting to the vehicle battery.

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As mentioned above check if you have a switch that changes charging from engine to leisure batteries (mine has) Check any fuses to the battery, have you tried a multi meter on both batteries just to confirm one battery is charging and the other is not
 
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Sounds like a fuse has blown to me, I too have the Sargent system and it maintains both sets of batteries. You should be able to confirm from the control panel that the cab battery has been selected to charge then just put a volt meter on the terminals to confirm current is being supplied.
 
Thank you all for your assistance. Looks like a fuse has gone but not at the Sargent board as the Leisure batteries are good. I will change the fuse on the Sargent unit to be sure though. I think there must be another fuse for the cab battery somewhere. Any suggestions?
 
Does the output on the Sargent controller have voltage signal at or above 12.6 when on EHU.
Check with multimeter.
If unsure which wire to check, post the Sargent model number here and we’ll google elec diagram / layout
 
Thanks, HandyAndy.
I may not get back to the MH until Sunday. I will let you know how I get on.

I am rather keen to get the battery back in because the passenger door cannot be locked without a power supply. Cheapskate Fiat have not fitted a manual lock!

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AlastairH said:
Thanks, HandyAndy.
I may not get back to the MH until Sunday. I will let you know how I get on.

I am rather keen to get the battery back in because the passenger door cannot be locked without a power supply. Cheapskate Fiat have not fitted a manual lock!
Click to expand...
I think that they do that because they know that their 12v electric is crap. Haha
 
Be aware that sometimes you need to leave the black shutdown switch left on ! If you turn this off it will only charge leisure even when smart is selected.
See Sargent website for a download if the manual if you don't already have one.
 
Just as an aside Alistair if you've not already chucked it the first dead battery may be salvageable, I flattened a car battery to sub 1v so that neither of my smart chargers would even attempt to charge it. So I used an old dumb 500ma trickle charger and eventually had it back to 12.7v and still seems to hold that charge.
 
Thanks again to everyone for your support.
To be honest, I am struggling with this problem. The battery, sadly, is not holding a charge so I need a replacement.
My electrical control unit is a Sargent EC400 which does not list a fuse for the charger. I am also struggling to find a fuse in the cab that might be linked to the battery. Also, I cannot find a fuse close to the battery as suggested by PhilandMena.
Help!

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Look on page 8 of the EC 400 Manual.
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Just had a light bulb moment. Are three fuses built on to the positive battery terminal?
 
You may well have 3 fusees there. I do too. One is for my Webesto heater and the other probably battery related. A quick look will determine if any have blown.
 
i thought I should let all the contributors to this post the outcome of my problems. I would also like to thank all of you contributors who took the time and trouble to get in touch. Thank you.

All fuses and connections are intact and no fault was found in the EC400 PSU or the 3 Stage Switching Mode Battery Charger connected PSU.

However, Sargent have advised that the relay which selects which battery is to be charged can sometimes stick. Since I discovered the problem, the van has been driven to and from an auto electrical engineers and both the engineer and myself have been poking around inside the PSU so it entirely possible that if the relay had stuck it has now been been inadvertently released.

I already have a power outage alert set up when the MH is in storage so my next task is to find a way of remotely monitoring battery voltages. Sigh....

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