Voltage Drop - Diesel heater - Battery Function issue?

[EdRedBird]

So I have a Transit The starter and default house nattery (A transit comes with 2) are under the driver seat and
2 Halfords Leisure Batt-HLB700 - 100Ah under the passenger seat.

A Renogy 12V 50 DC to DC controller behind the driver seat (No solar connected yet

Thick leads going up to the controller and to the passenger side house batteries

I have a second "patch" board behind the driver side as I like to get my left side wiring from there and my shore / AC to DC charger positioned here
I am measuring 13 V at points A and B (see image)

Point D drops 0.5V ...and at the point my fridge kicks in the voltage drops and goes back up when it goes in "standby"
Point C is the bloody issue though

As soon as my chinese dieselheater kicks in Voltage drops enough to get an E1 error on point C ... The voltage at poinmt D reads (I have one of these) about 11.9 / 12

I have shortened the orriginal lead on the heater and replaced it with a thicker cable

Last winter I did not have leisure batteries...i had 2 spare starter batteries under the driver seat and no issue

Now this issue is only there during diesel heater startup ...once its going all measuring points go up to above 12.6V

I have been considering a 3rd battery anyway but can you mix and match on AGM...could I place a starter battery beside the heater to overcome the initial powersurge

 

[Lenny HB]

Assuming your batteries are OK which they probably are as they recover to 12.6v with a load on them.
The cable to the heater is probably still undersize, you need to measure the volt drop from the battery to the heater when the heater is starting up ideally it wants to be less that 0.3v.
Those heaters can take 8 to 10 amps on startup. For a 3m cable run you need at least 4mm sq cable for a 5m run 6mm sq.

Also the volt drop you are getting to the fridge suggests the cable is also too small.

 

[Raul]

Yes, the 4mm is good up to about 4m at 10A load. Any longer needs to be 6mm2, and exceeding 6m needs to be 10mm2 cable.

 

[EdRedBird]

I am running a full sized charger cable to the heater and I shortened the actual cables that are connected.
As this previously worked on STARTER batteries I am wondering if the house batteries are up to the job

These batteries were only bought the 11th of June
No more than 30 cm 20 inches of original cable untill i go to cable thickness that would make some women jealous

 

[Two on Tour]

The simple option is to set the under voltage setting on your diesel heater control panel to 10.5 or 11 volts as I have done on mine.

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[autorouter]

It's not just the wire. A bad connection or a duff switch can have enough resistance to cause that kind of problem. And don't forget the negative return path, there can be voltage drops along that if there is a bit of resistance. Can you start from the leisure battery itself to be sure that the battery voltage isn't dropping?

 

[EdRedBird]

Two on Tour How do you do that ?...

Seriously this is thick (thicker than starter cables) cable gooing from my leisure battery to a patch pannel (10MM bolts) same thickness cable on the same bolt go to the shortened standard cabl
es ...(And I did not have that issue when I ran this of old (came with the van when bought) starter batteries that were replaced with new ones last winter
I really tought that going from 75 to 100 would get me MORE

 

[Two on Tour]

Two on Tour How do you do that ?...

Seriously this is thick (thicker than starter cables) cable gooing from my leisure battery to a patch pannel (10MM bolts) same thickness cable on the same bolt go to the shortened standard cabl
es ...(And I did not have that issue when I ran this of old (came with the van when bought) starter batteries that were replaced with new ones last winter
I really tought that going from 75 to 100 would get me MORE

Is it a Chinese diesel heater your running ?

 

[EdRedBird]

It's not just the wire. A bad connection or a duff switch can have enough resistance to cause that kind of problem. And don't forget the negative return path, there can be voltage drops along that if there is a bit of resistance. Can you start from the leisure battery itself to be sure that the battery voltage isn't dropping?

I dont understant your question regarding starting from the leisure battery This morning at 6 AM it was a bit nippy
The Light switch pannel read 12.9 V Thats D on that drawing (Again when the fridge kicks in which is branched off just before it this drops to 12.7 12.6 )

The Heater starts .... but conks out on an E1 .... I can see the voltage on the control panel (Point C) drop too but there is 0.5 / 0.7V difference with D (Heater starts D drops too)
As soon as I get the E1 ... Voltage reading goes back up and I can even restart until the next E1

Now can I mix my battery bank ... can I add a cheap starter battery in the mix close by the heater ... I mean I SHOULD not go near the current starting the vehicle takes ....

Could it be the "harness" for the heater at fault?

 

[EdRedBird]

Is it a Chinese diesel heater your running ?

是的，它是
Yes it is

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[autorouter]

I dont understant your question regarding starting from the leisure battery

Just to confirm that the leisure battery voltage itself isn't dropping when the heater kicks in. I know it shouldn't, but if there's a battery problem it might.

 

[Two on Tour]

I have been running an Afterburner 3rd party controller for the past 3 years, but when I was running our Chinese diesel heater with the standard Chinese LCD controller, I seem to remember that there was an option in the controller's advanced setting via the 1688 pin code.

 

[EdRedBird]

Just to confirm that the leisure battery voltage itself isn't dropping when the heater kicks in. I know it shouldn't, but if there's a battery problem it might.

Now I see ... I have a voltage meter in the car

Just to confirm that the leisure battery voltage itself isn't dropping when the heater kicks in. I know it shouldn't, but if there's a battery problem it might.

OK so checked the van
12.6 on point C
12.7 directly (well almost directly) at the leisure batteries (Cant take chair out so taking at my patch pannel
12.5 on point D controller

Trurning on the heater
D dropsdown to 10V , and my patch pannel drops down to 12.1...comes back up to 12.3 after the controller was unplugged

 

[Raul]

If batteries don’t hold the voltage with a 10a draw, unless the wiring is really weak, my gues is your batteries have much more reduced capacity than you think. With a 10a draw may drop 0,2-0,3v on healthy full batteries it’s a C/20 discharge rate on a 200ah bank, pretty reasonable, even at C/10 a 20A draw.

 

[Hoovie]

If batteries don’t hold the voltage with a 10a draw, unless the wiring is really weak, my gues is your batteries have much more reduced capacity than you think. With a 10a draw may drop 0,2-0,3v on healthy full batteries it’s a C/20 discharge rate on a 200ah bank, pretty reasonable, even at C/10 a 20A draw.

As an indication, I find on an approx 5A load on my 500Ah bank, the voltage drops by 0.1A (13.19V to 13.10V for example). A pure Lead-Acid based system would sag more and a pure Lithium system slightly less. Once the load is away, the voltage recovers.
(this pattern occurs every hour for around 15 minutes - compressor fridge)

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[gus-lopez]

The simple option is to set the under voltage setting on your diesel heater control panel to 10.5 or 11 volts as I have done on mine.

Some chinese heaters only have the simple 'on/off' + rotary fan speed control. Mine does & I prefer it as it is far simpler.

 

[Raul]

As an indication, I find on an approx 5A load on my 500Ah bank, the voltage drops by 0.1A (13.19V to 13.10V for example). A pure Lead-Acid based system would sag more and a pure Lithium system slightly less. Once the load is away, the voltage recovers.
(this pattern occurs every hour for around 15 minutes - compressor fridge)

I agree with your figures up to the lead acid point. Even with a C/20 load, the voltage should not dive that much and should recover pretty much quick almost to where it started. My 48v bank, over 7 years old 375ah new, with a 2,5kw load batteries stays on 48,9v, then bounces back to 50,5-51v where it started. That’s a C/7 draw, not C/10 or even C/20 in OP’s case. A C/20 draw should be very little drop.