Electrical gremlin, possibly battery problem

Mike Woolstencroft

Mike Woolstencroft

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Hi All

I wonder if anyone has any idea's as i'm all out :( I'll try and put as much info as possible, so this may be a bit long.

I moved into my van in January and until a couple of months ago my set up worked great, no problems at all that i noticed. Its just a basic set up, with 2 x 120ah AGM batteries (talking to Phil, they are wired correctly). The problems have started since i was installing my inverter and i accidently touch the van's earth lead on one of the positive battery terminals (it melted the corner off it), since then i have struggled to get the batteries past 97% on my monitor, seems to take a lot longer than it used too. Also when i'm charging via the Victron B2B it goes into float and says they are full but the monitor says its only at 96/97%.

When nothing is on i usually draw about 0.3 amps, and its always been like that.

So far i've changed the battery monitor, i've had the B2B exchanged for a new one also, i've checked all my earths and connections in most cases undone and redone the connection to make sure. I've changed the vehicle earth strap under the body (wasn't looking that great). At the request of the company i got my batteries off, i got a midtronics test done on battery i touched the earth cable with (that came back as good?)

Yesterday i ran the engine with it on float for an hour (still getting 5amps), then turned it off and used it for a couple of hours, started the engine again to go to work and it went straight to float. today same again it went to float on 96%, so im at my mums so i plugged in and put the battery charger on and thats been on now for an hour, obviously not full.

So from my point of view it seems like im losing amps somewhere, or my batteries are not working like they used too, as i have tried or renewed as much as i can. Anyone got any idea's or it is just me going loopy?
 
Well, firstly a Battery Monitors SOC is only a "best guess", even for the best ones. It is not unusual for a monitor to either get stuck at a nearly full number, or conversely jump to 100% too early. I would recalibrate to 100% after the chargers have been on for a while and the batteries are not taking any more charge (at that time they must logically be full and at 100% of their capacity).
I think making the conclusion that your batteries are never full solely because your Battery Monitor does not say 100% is not the thing to do.
Chargers going to float early then they really should is not conclusive either - Chargers and Batteries and Monitors don't talk to each other, it is all kind of "best guesses" for everything in truth.

When nothing is on, you draw 0.3A? well, something must be on then?
If there is nothing on, then the draw is 0.00A. It is that simple - it depends on what Monitor you have, but I think it might be worth recalibrating the current reading with no load connection on the battery (so if say a Victron BMV, remove the LOAD cable on the Shunt and then check the current draw and if not at zero, recalibrate the current. If you put it back on and a current is showing, then you know that is a load on the system even if "nothing" is on (on my system, I have a 0.9A draw when all the Habitation systems are turned off, for example, due to other monitoring systems)
 
Thanks for the reply :)

The 0.3A is when everything is turned off, but somethings are on standby, If i remove the load then the monitor is using something like 0.002A which is nothing :) Sorry i dint explain it better :)

I've lost count how many times ive recalibrated it recently, something ive never had to do before. Currently charging via the mains charger at the minute, thats been on for 3 hours and still going.

Before all this happened, i would just normally charge via the B2B to float and it would usually match up with the monitor. Where as now like the other week, i drove for an hour and half back, plus the same going and the monitor was still only showing 97% full, where as before all this it would normally show full after a drive like that. As i drive pretty much 6/7 days a week as i work, so it not like i run my batteries down much below 90% most of the time.

Power just seems to go a bit quick but harder to get it back in, if that makes sense. Might just be me but i've never had to mess about so much with the batteries, i pretty much just fitted them and forgot about them and let them do their thing.
 
I would keep an eye on the monitor and specifically not the SOC percentage but the AH value and see how that goes up and down and try and make sense of that.
The SOC value can be incorrect repeatedly if the charging efficiency is wrong (too high and it will show full too early; too low and it will never go full). On discharging, the Peukert Efficiency value can cause the SOC to drop either too quickly or too slowly if that is not right.
When you changed the monitor, did you adjust these from the defaults?
I don't think your shorting incident with the earth lead would have had an effect - the batteries shorting momentarily wouldn't matter except given you a hell of a surprise.
 
I just fitted the monitor the same way as i fitted the first one, set the AH's and cabrilated when the battery were charged. its just a chinese cheap one. but it normally gave me a decent indication of where i was at with the power.
Yeah your not wrong a few choice waords were used as i thought i had knackered a battery. If you think that wouldn't of had much of an affect on the batteries, then i'll just try and get used to seeing the monitor differently, like i said i move into the van in january so this is my first autumn in the van and it just might be me with the sun lower and using more power and not being able to put it back in unless im driving.
 
It is amazing how soft the lead posts are! I melted one a touch by connecting the +ve and -ve terminals with a 13A fuse to blow it (for a specific reason).
Sounds like you have maybe a Aili Monitor (round one?) - they are pretty good. Check the screws on the shunt are nice and tight - that can mess up the current info.
I think in your position I would try a discharge test when you have a chance to not use the van for a couple of days to check the batteries .... start from as fully charged as you can be (chargers not putting any significant current in) and put a constant load of 6A (1/20th of the 240Ah total capacity) on for 10 hours, turn everything off (inc any standby loads) and check the voltage immediately and then around an hour later. Rule of thumb would be around 12.05V
 
Just as a double check of the battery you are concerned about, try removing it altogether and run with one battery for a while to see how your system responds. If things go back to normal then it could well be your suspect battery is not happy.
 
When I want to be sure I have fully charged my battery’s I put the van on hookup and leave it for between 24 and 48 hours. Not had to do it for a long time but that is the only way I would be happy starting out. SOC is important to me as I am running Lifepo4 battery bank but my understanding is Voltage is much more accurate/useful for lead acid type of battery’s. No confusion with capacity drop that way but I may be wrong on this, Dave will correct if I am 👍
 
Yes i do have an Aili Monitor, and it was good before this. Just so i don't miss anything out, before all this happened it was pretty good, as i said i was fitting the inverter and if the touching the battery hasn't harmed them, when i was fitting it, it was the inverter ground that touched the battery, which was connected to my buzzbar with everything on it.
Random question, since installing the inverter its been a bit haywire, now the inverter is earthed to my buzzbar, which then goes to the vehicle earthing point, but the inverter also has a ground that goes to the vehicle earthing point, is there any need for it to have essentially 2 earths to the same point? or could that be making my readings go haywire?

May try that Allan, and go with 1 battery for a couple of days and see how that works out, then change to the other one, see if theres a difference :)

May struggled discharging, as i live in the van and work.. might see if i can work something out when im off work :)
 
From the batteries, The earth is wired to my Aili monitor shunt which is then wired to the buzzbar (where all my earths go), that buzzbar is then also wired to the vehicle earth point.

the inverter is a Edecoa 1500w, it has the usually positive and earth underneath, positive wired to the battery (with a 50amp fuse inbetween), the earth is wired to the buzzbar with everything else. Then on the side of the inverter there is a small nut that says it is for the ground which i wired to the vehicle earth point.
I've seen someone who has the same named inverter and they have the ground on the side but they haven't wired it, so maybe that was where i was going wrong?

As i was driving again today after charging the batteries up the other day and resetting the monitor, they were 4% out again today. So i have disconnected the inverter for now(dont use it that much) just to see if there is any difference :)
 
Ah, now I understand. The inverter has a +12v connection and a battery negative connection. They're the cables that provide it with power. The inverter has a three pin power output with an earth connection. That's what the other ground will be for.
With mains power, normally the earth connection is supplied by the power distribution network, and generally it is also kept at more or less the same voltage as the neutral line. So the neutral is about 0v and the live is +-240v.
In a motorhome, it's probably safer not to link either of the mains lines to earth potential, but to let it float. The inverter generates a potentially lethal voltage across the two output wires, and it is best not to tie either to something you might be holding
The earth connection should be connected to the vehicle structure. You don't want a voltage between the case of the toaster and the kitchen sink!
So I would connect both earth cables.
 
Ok will do that, and wire it back up as i had it before then :) So that 2nd ground probably isn't my problem then. Oh well i'll keep trying to sort it out :)
Thanks everyone for your input so far :)
 
Looks like you are suffering from Battery Anxiety so perhaps you should take two aspirin and have a lie down. I have a 120Ah lithium and never seen it above SOC 96% They have said I should run it completely flat and then charge it up again. It's only an indication of what's in the battery. As time goes on the batteries will hold less charge and start to sulfate inside. So nothing really to worry about.
 
It seems to me that you are worried about the battery meter reading 96% instead of 100%. There is a simple fix for that. You should already have the materials needed in the van.
Take a pair of scissors and a roll of gaffer tape.
Carefully cut a piece of gaffer tape to precisely fit the battery status meter display.
Make it neat, because at first you will be looking at it frequently.
Cover the display with the tape. You'll soon learn that the batteries work just fine without you looking at the meter.
After between 12 and 24 months, when you've got the hang of not looking at the meter, it's best to remove the gaffer tape in case the glue goes nasty and too permanent.
 
Yeah your probably right, I am probably panicking a bit too much. To me they just don't seem to be performing as well, which i can kind of understand if they were a couple of years old, but these are less than 12 months old. Anyways i will try my best to stop worrying as much and just use them until it is obvious that they aren't well :)

Thanks for the advice all (y)
 
It's worth mentioning that when I had a battery fail (after only nine years of service*) the charge status wouldn't go above 70% and rapidly dropped to 60% or so.

I didn't notice that, though. What alerted me to the problem was the CO alarm going up whenever the sun shone: seems they're triggered by a battery venting gases. And no, I hadn't connected a vent pipe like you should.

*In fairness to that battery, it was a SLA being charged as an AGM, which probably shortened its life significantly.
 
Mike Woolstencroft said:
Yeah your probably right, I am probably panicking a bit too much. To me they just don't seem to be performing as well, which i can kind of understand if they were a couple of years old, but these are less than 12 months old. Anyways i will try my best to stop worrying as much and just use them until it is obvious that they aren't well :)

Thanks for the advice all (y)
Click to expand...
Treatment is much more important than age in a battery. I managed to ruin 3x90ah Bosch PowerFrame battery’s in around 12 months but drawing too much and not being able to get charged back enough. Battery’s are still working and I use one as a starter battery but capacity has dropped drastically (maybe over 50%).
 
nabsim said:
Treatment is much more important than age in a battery. I managed to ruin 3x90ah Bosch PowerFrame battery’s in around 12 months but drawing too much and not being able to get charged back enough. Battery’s are still working and I use one as a starter battery but capacity has dropped drastically (maybe over 50%).
Click to expand...
A starter bat below 80 % wont turn a engine over for more than about 10 seconds if at all, may not be as knackered as you think.
 
trevskoda said:
A starter bat below 80 % wont turn a engine over for more than about 10 seconds if at all, may not be as knackered as you think.
Click to expand...
Do you mean 80% charge or 80% capacity? Either way, something is wrong if you have to run the starter for ten seconds.
 
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