Low Charging Current

A

Affinite

Joined
Aug 30, 2023
Posts
19
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46
Location
Derby, UK
Funster No
98,515
MH
Compass Kensington
Exp
New to MotorHoming
I've been concerned that my leisure battery wasn't being charged properly so I fitted a Victron shunt to monitor it.
I see no more than 3 Amps going in when charging from Alternator or mains charger even with a pretty depleted battery.
I observed it after a long run a few weeks ago in case the start battery was being charged as a priority but even after 6 or so hours, the charge current to the leisure battery was pitiful.
The mains charger is a 20A unit and I would have expected to see 20A + when charging from Alternator
The MH (2020 Compass Avant Garde/Peugeot Boxer) has a strange little BCA PDU that the charging wires go through - I wonder if it is somehow managing/reducing the charge current.
Any ideas ?
 
What made you think the battery was not getting the charge it needed.

Perhaps it’s at more of a charged state than you think it is.
Does it ever reach full state of charge.
Or
There’s an issue with the battery itself.
 
Or you fridge is powered through the same source and most of the power is going to that. 3 way fridges in 12v and 240v modes use a lot of power.

A few years ago, when smart alternators first appeared, some people were finding their hab batteries were depleting while they drove!
 
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Do you have a multi-meter? If so it might be worth checking the voltage at the battery. At least then you'll know the batteries actual state of charge.
 
The Victron shunt needs to be synchronised before it can indicate the state of charge. I think synchronisation can only be done when the battery is full. What voltage is the shunt showing and what type of leisure battery have you got.

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Thanks for quick responses. :giggle:
I have a remote monitoring device which tells me that the battery is currently at 12.2v (Victron shunt thinks that is 84%) with no charge going in because the solar panel is covered with snow !
I'll go to the yard and start her up again tomorrow and see what the charging current is then.
I have see full state of charge after prolonged hook up to mains
AGM battery
 
What type of battery is it? - A lead acid is around 60% at 12.2v, you could manually set the shunt to that, but assuming it's settings are correct then best to fully charge the battery then it should sync to 100%, that way it's set to a known standard vs your settings. If LA remember to put a reasonable capacity in allowing for any capacity loss due to age.

Assuming the charge sources are not bypassing the shunt (so giving a false current) and if none of them are charging the battery at a "sensible" rate, is there a single point they all connect through?

You can calibrate the shunt which is simple to do (disconnect the load side, and use the Connect app to set it to 0), but I'm pretty sure I've not heard of one being out, but the facility is there so I guess it must be possible.
 
AdrianChen said:
What type of battery is it? - A lead acid is around 60% at 12.2v, you could manually set the shunt to that, but assuming it's settings are correct then best to fully charge the battery then it should sync to 100%, that way it's set to a known standard vs your settings. If LA remember to put a reasonable capacity in allowing for any capacity loss due to age.

Assuming the charge sources are not bypassing the shunt (so giving a false current) and if none of them are charging the battery at a "sensible" rate, is there a single point they all connect through?

You can calibrate the shunt which is simple to do (disconnect the load side, and use the Connect app to set it to 0), but I'm pretty sure I've not heard of one being out, but the facility is there so I guess it must be possible.
Click to expand...
Our battery is around 6°c this morning so the chargers are about to stop charging, but that's Lithium.
 
Affinite said:
Thanks for quick responses. :giggle:
I have a remote monitoring device which tells me that the battery is currently at 12.2v (Victron shunt thinks that is 84%) with no charge going in because the solar panel is covered with snow !
I'll go to the yard and start her up again tomorrow and see what the charging current is then.
I have see full state of charge after prolonged hook up to mains
AGM battery
Click to expand...
The Victron shunt calculates the % charge by counting the Amps going in and out of the battery not from the Volts. 12.2V on your AGM battery suggests it is not fully charged. Is the + wire from your shunt connected directly to the + on the leisure battery or is your Voltage reading from something else?

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Pausim said:
The Victron shunt calculates the % charge by counting the Amps going in and out of the battery not from the Volts. 12.2V on your AGM battery suggests it is not fully charged. Is the + wire from your shunt connected directly to the + on the leisure battery or is your Voltage reading from something else?
Click to expand...
The voltage sense wire should be a thin red cable with inline fuse connected from the battery + to the shunt Vbatt+ terminal.
 
Whatever the state of charge of the battery, the shunt should accurately measure the amps going into and out of the battery, all the time. The amp-hour state of charge takes a bit of setting up, but has no influence at all on the instantaneous amps measurement.

It is important that all the possible amps flows are routed through the shunt, otherwise it can't measure them and will give false amps and amp-hour readings. Is the shunt connected on the battery negative terminal? That's the usual place to locate it.

The battery side of the shunt should be connected to the battery negative terminal. Nothing else at all should be connected to the battery negative terminal. It is a common mistake to leave the chassis earth connected to the battery terminal - this is incorrect, it needs to be moved to the load side of the shunt. That may be complicated if the chassis earth has a battery lug rather than an eyelet-type termination.

All the loads, including the chassis earth, should be connected to the load side of the shunt, so that all the amps flows are channelled through the shunt.

The only other wire permitted on the battery side of the shunt is a link wire between the negatives of the batteries, if you have more than one leisure battery.
 
Affinite said:
The mains charger is a 20A unit and I would have expected to see 20A + when charging from Alternator
Click to expand...
I agree, I would expect to see a minimum of about 19A from the mains charger if the battery is below about 80% charged.

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Thanks for all suggestions, sorry about "radio silence"

I realise that reported SOC is probably a distraction at the moment - I was more concerned about the instant current readings.

I did go to the MH on Wednesday and confirm that;
The only connection on the shunt (Batt) terminal goes to the battery neg and there are no other connections to the battery neg.
The Batt+ve connection on the shunt is taken (via a bus-bar and a fuse) from the battery +ve post
When I arrived, the leisure battery voltage (reported by the shunt) was 12.2V and start battery was 12.8V
When I started the engine, the leisure battery voltage rose quickly to 13.2V and Start rose to 13.9V
Current reported by the shunt was 4A dropping to 2A after a couple of minutes

I do intend to go back and put a multimeter in-line to verify the Current and Voltage readings but it was too darn cold yesterday !
I realise I've got too many variables at present so I'll report back when I have confirmed those readings
 
Assuming you've not got a DC-DC charger (so the hab battery is charged from the alternator pretty much directly) I think you'd expect to see a similar charging voltage on both batteries when the alternator is running. Is it possible that there's too much voltage drop to the hab battery?
 
Affinite said:
When I started the engine, the leisure battery voltage rose quickly to 13.2V and Start rose to 13.9V
Current reported by the shunt was 4A dropping to 2A after a couple of minutes
Click to expand...
Is your leisure battery shot? AGM usually need 14.6V to keep them in good condition and as the current flow drops off I would expect to see the voltage rising to that sort of level.
 
Affinite said:
When I started the engine, the leisure battery voltage rose quickly to 13.2V and Start rose to 13.9V
Current reported by the shunt was 4A dropping to 2A after a couple of minutes
Click to expand...
That's too much of a voltage difference. Imagine you had a jump lead clipped onto the starter batter positive, and the other end clipped onto the leisure battery positive. You would expect the battery voltages to be practically identical.

The split charge relay is supposed to be doing exactly what a jump lead would do, the only difference is it disconnects automatically when the engine stops. If you have 0.7V voltage drop, with a current of only 4A, then there is some resistance somewhere in the wires, connections or inside the box that houses the split charge relay.

You could try going along the wire, at each connection, until you find exactly where the voltage goes from 13.9V to 13.2V. That's where the resistance is.
 
Affinite said:
I do intend to go back and put a multimeter in-line to verify the Current and Voltage readings but it was too darn cold yesterday !
Click to expand...
It's a lot easier and safer to measure current with a clamp meter. Especially if you want to measure the amps from the alternator to the starter battery. You should never disconnect the alternator from the starter battery, without a good reason like changing the starter battery. All kinds of bad things happen if the alternator to starter cable gets disconnected while the engine is running, even for a fraction of a second. A 60V prolonged surge is not unusual. Use a clamp meter, which just clips round the wire and doesn't require any disconnection.

Note that if you are buying a clamp meter, there are two different technologies for measuring current: a current transformer (CT) and a Hall probe. The CT type only works with AC. The Hall probe type works with both AC and DC, and is a bit more expensive.

Many of the advertised clamp meters only measure AC current. Even if it says 'AC/DC Clamp Meter' on the box. They measure AC and DC volts, but only AC current. So you need to read the small print, and see what DC range it measures.

I have a Uni-T UT210E, which is very popular on here. It measures up to 100A DC, but also has a 2A range which is useful for tracing small leakage currents. The 210D model will measure up to 200A DC, if you prefer that. Note that the 210A, B and C models have CT sensors, and only measure AC current, not DC.

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Returned to MH this pm
Turned off the Solar Panel MPPT (Panel covered in snow but turned off so as not to confuse the test)

Voltage when I arrived was 12.5V (200mA draw for alarm and remote monitoring device so not truly a resting voltage)
Started engine
Voltage rose to 13.1V
Current (charging) constant at around 2A !
Voltages and Current were measured Victron shunt and MultiMeter

I do have the option of taking the MH back to the supplying dealer as I still have 4 months left on the warranty but I wanted to try to understand what might be going wrong.
I'm now pretty sure its not my installation of the Victron Shunt but I still dont understand why the charging current is so low.

autorouter - thanks for the advice. I don't have a clamp meter but I'm hoping Santa is watching this thread.
Yes, I do know not to disconnect the alternator from the start battery but felt Id be safe with putting a meter in-line with the leisure battery for this test.
 
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Can you get a different charger on to the battery directly? Only things apart from connections/fuses that can supress the current would be a duff SCR, or a tired battery. Do you have any jump leads or something similar?
 
Yes, I thought (after I got home ) of taking it off getting it tested - doh!
 
Took the battery off and put it on a DC supply/charger. I set the charging voltage to 13.8V and saw the battery pulling 6.5A. When I put the charge voltage up to 14.1 the current draw was 10A.
So I don't think the battery is the problem.
The MH charging voltage didnt seem to rise about 13.1 so more head scratching but I think Im going to take it to the dealer to checkout the charging circuit
 
That's good - battery OK, they can work back from there.....

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