Batteries behaving strangely / still reading high voltage

[HarryHamsta]

Hi all,

My moho is a Laika Ecovip 6. Imported last year from Germany. I overhauled the 12v system as previously it was running on a single 70ah leisure battery and we do a lot of wild camping / so I need an inverter to power my laptop for work.

Last June I installed 2 x 140ah Bosch leisure batteries in parallel, a Victron charger controller connected to a 300w pv panel, a 1000w inverter, and a few other bits and bobs (USB plugs and the like). I rerouted the existing wiring from the engine bay (where original leisure batt was) to the rear, where both new leisure batteries located. Everything worked fine. I will admit I mistreated the batteries somewhat over autumn / winter as the nights drew in, and they discharged to 11.9v on a fairly regular basis. We have been in an airbnb in France since mid-December. When I drove back to the UK in January then a number of appliances stopped working. Using anything with a medium / high wattage (water pump, electric step) would result in lights completing blacking out. When I returned to France then I used a smart charger to recondition the batteries. Since then I spent this evening in the campervan and am still experiencing the same problem. Lights work but go out when turning on pump. Turn off the pump, lights are back but very dim. All the hallmarks of battery with no charge.

What is confusing me is that the voltage is still reading 12.5/12.6 when this is happening. This is from a multimeter on the battery terminals. The inverter still turns on when the lights have blacked out, although I haven't tried charging anything from it. AFAIK it doesn't have a low voltage cut-off like other inverters I have used.

I have a good practical understanding of 12v but my theory is lacking. Is it possible for a battery to be 'dead' but for it still to register a high voltage / fully charged? I'm happy to replace the batteries but I don't want to spend £200/300 on batteries only to find out this isn't the problem.

Any thoughts would be greatly appreciated.

Harry

 

[tonyidle]

It sounds more like a poor connection. With a small load the voltage at the device being powered is near enough the same as the battery voltage. When a heavier load is connected (pump or inverter) the voltage AT THE APPLIANCES being powered drops. The battery voltage remains the same. First check is voltage at the pump or inverter when switched on. If as I suspect it is substantially lower than the battery voltage you have a poor connection. Try battery +ve and earth connections first.

 

[Raul]

I think the batteries are done, try take a reading at the battery terminals when you operate a high drain appliance and lights are going out.
The inv. has a very low cut off and still works on 10-11v while the led drivers says no.

 

[Raul]

From memory the victron inv 12/1200 va has a built in non adjustable 10.5v cut of, like most other stand alone inverters.
In regard to your last question as if batteries can be dead and still show good voltage; yes they can. They just bounce back after the drain is of, the capacity has reduced so much that they can’t sustain that discharge rate anymore. In other words voltage is not a definite indicator for a healthy battery, load drop test is. That’s why flooded cells are better at monitoring as you can sample the specific gravity of the electrolyte and give you a precise indication.
A work around it on sealed batts, is a batt monitor with a shunt, so you can keep track of what you take out , you must replace back, and not work in deficit charging.

 

[Lenny HB]

Does sound like battery failure to me, OK on a light load but can't support a heavier current discharge.
May only be one battery that has failed and is dragging down the other one. I would separate the batteries and test each one with a slow discharge.

Best way to test is to do a controlled discharge.
First charge the battery fully and leave it to settle for an hour then:-

For example if it's a 100a/h battery load it with a 5 amp load and run for 5 hours, this will represent a 25% discharge. (adjust load/time to suit the size of battery)
Disconnect the load and leave to stand for at least 30 min then measure the voltage.
Repeate the the test and you will have discharged the battery to 50%.
You can repeat again then it will be 75% discharged.

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[Pausim]

Is it possible for a battery to be 'dead' but for it still to register a high voltage

Yes sulphation can cause this. Parts of the plates become sulphated but the unaffected bits can still charge up to a reasonable voltage. In effect what started out as a 140Ah battery might perhaps be down to less than half this. A bit like a home hot water tank might get very badly scaled, the pressure might still be ok but the hot water soon runs out.

 

[Jev88]

On a related note, you could get a 12v adaptor and stop using the inverter for your laptop.

 

[HarryHamsta]

It sounds more like a poor connection. With a small load the voltage at the device being powered is near enough the same as the battery voltage. When a heavier load is connected (pump or inverter) the voltage AT THE APPLIANCES being powered drops. The battery voltage remains the same. First check is voltage at the pump or inverter when switched on. If as I suspect it is substantially lower than the battery voltage you have a poor connection. Try battery +ve and earth connections first.

Thanks Tony. Just to clarify, the existing control panel (zig unit style) is connected to the new batteries through one 10mm2 cable that runs from the control panel and under the van. I have checked this and recrimped it but I think I will maybe strip it back to fresh cable and recrimp. I'll also check all the earths and also the voltage at the pump end.

Something else I can do is try and run the blender when all the lights are out, as this will run off the inverter which is on the 'new' circuit. I think if that works then that suggests the problem is with the wiring for the 'original' appliances.

 

[HarryHamsta]

Yes sulphation can cause this. Parts of the plates become sulphated but the unaffected bits can still charge up to a reasonable voltage. In effect what started out as a 140Ah battery might perhaps be down to less than half this. A bit like a home hot water tank might get very badly scaled, the pressure might still be ok but the hot water soon runs out.

Hi Pausim, to add some extra information there was a lot of build up on one of the negative terminals (the one connected to the earth), this first appeared in autumn and only got worse over winter. Also when installing the batteries I unfortunately bridged the + & - terminals of one of the batteries (not the one with the build up) with a spanner and this took a chunk out of the - terminal! Luckily my facial features and digits remained intact.

 

[HarryHamsta]

From memory the victron inv 12/1200 va has a built in non adjustable 10.5v cut of, like most other stand alone inverters.
In regard to your last question as if batteries can be dead and still show good voltage; yes they can. They just bounce back after the drain is of, the capacity has reduced so much that they can’t sustain that discharge rate anymore. In other words voltage is not a definite indicator for a healthy battery, load drop test is. That’s why flooded cells are better at monitoring as you can sample the specific gravity of the electrolyte and give you a precise indication.
A work around it on sealed batts, is a batt monitor with a shunt, so you can keep track of what you take out , you must replace back, and not work in deficit charging.

Hi Raul,

Even when the pump (or external halogen light / other high W appliance) was on and the lights were blacked out, the voltage from the batteries (tested with meter on terminals) was still reading 12.6. So there is no bounce back as the voltage isn't dropping.

Just to clarify the inverter isn't victron, it's a mid range chinese brand from Amazon. The solar charge controller is Victron.

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[HarryHamsta]

On a related note, you could get a 12v adaptor and stop using the inverter for your laptop.

Thanks Jev, I have a macbook pro and I read in the past that it isn't wise to charge them from anything but a pure sine wave inverter. I'll double check that though as we only use the inverter to charge the laptop and ocassionaly use a small blender.

 

[Richard n Ann]

What is confusing me is that the voltage is still reading 12.5/12.6 when this is happening. This is from a multimeter on the battery terminals.

You must have a bad connection between the lights and battery. The lights are going out because of low voltage but the voltage isn't low at the battery.

 

[Raul]

If you are sure there is no voltage drop on high drain, then Tonyidle on post two may be right.
The thing is a lot of folk misunderstand earth on a fixed installation with neutral mobile chassis bonding. On bigger draws you run two wires and avoid using the chassis as a conductor. That gives a degree of isolation and helps with corrosion. So your problem may be in connections, and specially those chassis bonded.

 

[peterc10]

When you test the batteries do you disconnect everything, including the solar? If not you are probably reading the voltage coming from the solar. But your problem is that although the voltage is there the current (amps) is not because this time of year the solar is not pumping out enough energy (measured in watts) to keep the batteries topped up.

I suspect your batteries are goosed.

BTW you do not need to use an inverter to power laptops or anything USB, and using one is a very inefficient waste of energy. All laptops and USB items run on low voltage DC - typically 12 to 20v for laptops and 5v for USB. You are taking low voltage DC (12v) from your batteries and turning it into high voltage AC with the inverter and then plugging in an adaptor which takes that high voltage AC and converts it back to low voltage DC again. Instead use 12v adaptors that plug into the 12v sockets. You can get plenty of USB ones that will power all types of USB items. And you can get an adaptor specifically for your laptop that will convert the 12v to whatever voltage yours runs at. Just search Amazon using 12v adapter along with the name and model/number of your laptop.

 

[HarryHamsta]

If you are sure there is no voltage drop on high drain, then Tonyidle on post two may be right.
The thing is a lot of folk misunderstand earth on a fixed installation with neutral mobile chassis bonding. On bigger draws you run two wires and avoid using the chassis as a conductor. That gives a degree of isolation and helps with corrosion. So your problem may be in connections, and specially those chassis bonded.

Hi Raul,

So I've got all the + cables running from no1 leisure battery, and then all the - cables running from no2 leisure battery. I read this was the correct way to do it when in parallel.

Can you clarify what you mean when you say 'run two wire and avoid using the chassis as a conductor? I am running one 10mm2 (i think) - cable which is bolted and greased to the chassis. What is the alternative?

When you test the batteries do you disconnect everything, including the solar? If not you are probably reading the voltage coming from the solar. But your problem is that although the voltage is there the current (amps) is not because this time of year the solar is not pumping out enough energy (measured in watts) to keep the batteries topped up.

I suspect your batteries are goosed.

BTW you do not need to use an inverter to power laptops or anything USB, and using one is a very inefficient waste of energy. All laptops and USB items run on low voltage DC - typically 12 to 20v for laptops and 5v for USB. You are taking low voltage DC (12v) from your batteries and turning it into high voltage AC with the inverter and then plugging in an adaptor which takes that high voltage AC and converts it back to low voltage DC again. Instead use 12v adaptors that plug into the 12v sockets. You can get plenty of USB ones that will power all types of USB items. And you can get an adaptor specifically for your laptop that will convert the 12v to whatever voltage yours runs at. Just search Amazon using 12v adapter along with the name and model/number of your laptop.

Hi Peter, I was testing it last night 8PM so no charge from the solar. In the daytime I'm not experiencing the same problem, presumably because I'm drawing enough charge from the solar.

I'll have a look for a macbook 12v charger. I have a 2017 macbook which charges from USB-C so I can charge it from a USB-USBC cable but its a much slower charge, If I'm using the macbook then it consumes power faster than it charges. Thanks for the advice.

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[peterc10]

Hi Peter, I was testing it last night 8PM so no charge from the solar. In the daytime I'm not experiencing the same problem, presumably because I'm drawing enough charge from the solar.

I'll have a look for a macbook 12v charger. I have a 2017 macbook which charges from USB-C so I can charge it from a USB-USBC cable but its a much slower charge, If I'm using the macbook then it consumes power faster than it charges. Thanks for the advice.

I doubt very much that you will be getting enough power from a 300W panel at this time of year in the UK even at midday with the sun shining. And even worse with the cloud and rain we are experiencing at the moment. You need to find an electric hookup or scoot off to Spain.

Probably duff info on search terms. Try 12v charger macbook. But I must say that you have entered Steve Jobs' secret garden so you may find it more difficult with a macbook. Link Removed and I have always found Anker adaptors to be reliable. There are others available.

 

[andy63]

Just reading through..not much to add but I do have a 12v Mac book charging adapter ..worked fine for a few years .?

Andy

 

[Spriddler]

Can you clarify what you mean when you say 'run two wire and avoid using the chassis as a conductor?

Run an Earth wire from the batteries to the panel instead of using the chassis as the earth return.
I'm with tonyidle in that it seems like a bad/loose/corroded connection in the battery feed to the panel.
Are your battery terminal posts clean?

 

[HarryHamsta]

I doubt very much that you will be getting enough power from a 300W panel at this time of year in the UK even at midday with the sun shining. And even worse with the cloud and rain we are experiencing at the moment. You need to find an electric hookup or scoot off to Spain.

Probably duff info on search terms. Try 12v charger macbook. But I must say that you have entered Steve Jobs' secret garden so you may find it more difficult with a macbook. Link Removed and I have always found Anker adaptors to be reliable. There are others available.

Haha Steve Job's secret garden, brilliant! I'll check out the anker, thanks Peter.

I'm actually in northern France. Lorraine. We aren't living in the moho at the moment - in an airbnb until April. I have a small USB / 12v plug / 12v readout panel connected to the leisure battery and I'm getting a voltage of 13.9 in the daytime (on sunny-ish days), no load on the battery. I question the accuracy of that though.

Run an Earth wire from the batteries to the panel instead of using the chassis as the earth return.
I'm with tonyidle in that it seems like a bad/loose/corroded connection in the battery feed to the panel.
Are your battery terminal posts clean?

Hi Spriddler. Battery terminals clean (i cleaned up the build up with bicarb / water). I'm going to check all the connections in the next few days.

 

[Raul]

What sprridler said. Run dedicated ngative wire from source to consuption and avoid using the chassis as a negative conductor.

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[Pausim]

Hi Pausim, to add some extra information there was a lot of build up on one of the negative terminals (the one connected to the earth), this first appeared in autumn and only got worse over winter. Also when installing the batteries I unfortunately bridged the + & - terminals of one of the batteries (not the one with the build up) with a spanner and this took a chunk out of the - terminal! Luckily my facial features and digits remained intact.

Oops! The terminal can be cleaned and greased. The sulphation I was talking about is inside the battery. Some chargers have a desulphation setting that sends higher pulses of voltage into the battery to try and dislodge the sulphates but deep discharge and not getting immediately recharged is bad for batteries.

Just a thought but having moved the leisure batteries from the front to the back of your motorhome have you used heavy enough gauge wiring. If the cable runs are longer there may be a voltage drop that is stopping proper charging.

 

[Spriddler]

What sprridler said. Run dedicated ngative wire from source to consuption and avoid using the chassis as a negative conductor.

Yes, and for just testing the effectiveness you don't have to run it 'nicely' through/behind the panels etc. but just 'drape' it from the source to the panel in the most convenient route. If it cures the problem you can tidy it up and re-run it out of sight afterwards.

 

[peterc10]

Haha Steve Job's secret garden, brilliant! I'll check out the anker, thanks Peter.

Bit like Hotel California ............................................. you can check out anytime you want, but you can never leave.

I'm actually in northern France. Lorraine. We aren't living in the moho at the moment - in an airbnb until April. I have a small USB / 12v plug / 12v readout panel connected to the leisure battery and I'm getting a voltage of 13.9 in the daytime (on sunny-ish days), no load on the battery. I question the accuracy of that though.

Northern France is getting it as bad as us I reckon.

As I said before, all you are doing is reading what voltage is going in from the solar. That does not tell you what condition your battery is in. And spot readings of voltage going in is not a reliable way of knowing the actual power going in. 13.9v with a charging current of 0.5 amps gives you 7 watts, which is not going to help you much at all. You really need a battery monitor like the Victron BM700, and make sure everything in and out goes through it. That will enable you to monitor net power in and out and give you a much better picture of the state of your batteries.

Can't you run a lead to the airbnb place to hook up mains to the motorhome to give the batteries a boost? But, your type of batteries do not like to be discharged below 50% and if that is done a few times, they become knackered. Given that you say that it has been as low as 11.9v, which is close to fully discharged, a few times I think your batteries are probably now goosed. But before you replace them you really need to sort out ways of keeping them topped up properly, or you will be in the same position later this year with your new batteries. If you spend a lot of time driving you may want to get a B2B charger which maximises the power from the vehicles alternator.

 

[HarryHamsta]

Oops! The terminal can be cleaned and greased. The sulphation I was talking about is inside the battery. Some chargers have a desulphation setting that sends higher pulses of voltage into the battery to try and dislodge the sulphates but deep discharge and not getting immediately recharged is bad for batteries.

Just a thought but having moved the leisure batteries from the front to the back of your motorhome have you used heavy enough gauge wiring. If the cable runs are longer there may be a voltage drop that is stopping proper charging.

Ah I see. I got a CTEK charger at the start of the year and ran the "recondition" mode on both batteries which I believe is what you are talking about.

The length of the original cable was actually long enough so I didn't have to extend it. I'd guess it's 3/4m at 10mm2 (guess on both measurements) but as I say I used the original cable.

Bit like Hotel California ............................................. you can check out anytime you want, but you can never leave.


Northern France is getting it as bad as us I reckon.

As I said before, all you are doing is reading what voltage is going in from the solar. That does not tell you what condition your battery is in. And spot readings of voltage going in is not a reliable way of knowing the actual power going in. 13.9v with a charging current of 0.5 amps gives you 7 watts, which is not going to help you much at all. You really need a battery monitor like the Victron BM700, and make sure everything in and out goes through it. That will enable you to monitor net power in and out and give you a much better picture of the state of your batteries.

Can't you run a lead to the airbnb place to hook up mains to the motorhome to give the batteries a boost? But, your type of batteries do not like to be discharged below 50% and if that is done a few times, they become knackered. Given that you say that it has been as low as 11.9v, which is close to fully discharged, a few times I think your batteries are probably now goosed. But before you replace them you really need to sort out ways of keeping them topped up properly, or you will be in the same position later this year with your new batteries. If you spend a lot of time driving you may want to get a B2B charger which maximises the power from the vehicles alternator.

Rather than use the hook up as the in built charger is the original from 1995 so it's not 'smart' AFAIK and I think just delivers a trickle charge (not sure if I could have overcharged the batteries from being on hook up last year but that's another topic), I ran an extension cable and plugged them into a new smart charger (see above) and ran that for about 48 hours on each battery, on recondition mode.

The original split charge relay is still fitted but as with the original charger it dates from 1995 and is probably not that efficient. What is a B2B relay? I have seen that Victron do split charge relays so perhaps that is worth a go.

- - - - - - - -

Today I simplified everything. Disconnected the solar. disconnect the split charge relay. Connected everything to one battery (the one that didn't get the build up on the -terminal). Connected only 1) the original + cable (10mm2) from the control panel, 2) the + cable (25mm2) to the new fuse box, and 3) the - which runs to the new fuse box. It's worth mentioning that the original - cable from the control panel is the same place it began, which is earthed to the chassis in the engine bay.

I also restripped & recrimped the original + cable, and checked both - cables to chassis (still working on the chassis as completing the - circuit principle for now).

So far so good. Using various appliances I've run the battery down to 12.2 (tested at the battery terminals) and the lights are still on & bright, when I run the pump / external halogen light I'm not getting the same cut out I was getting before.

With no load, the voltage is the same at the battery and at the control panel.

With a load at the battery end (eg inverter powering 80w macbook charger & 130w 12v hoover), the voltage is the same at the battery & control panel.

With a load at the control panel end (10no 2W LED lights & 1no 25W halogen ext. light) then the voltage is lower (11.8) at the control panel than at the battery end (12.2).

Sat here wishing I had paid more attention at school. Am I correct in thinking that, in the last scenario, the voltage would read lower at the control panel end than the battery end because that is where the load is 'occuring'?

Next step would be to test the 2nd battery in the same way.

I accept that without proper monitoring equipment a lot of this is fairly innaccurate but I'm working with what I have to hand. I also accept I've probably goosed the batteries but I'm trying to work out if I can get another summer out of them at least.

What is the best way to check the capacity of the batteries? I assume charge the batteries to full and then apply a known load over a set amount of time?

Thanks for all the input guys! It's all a learning process.

edit: attached a few photos for context.

 

[Richard n Ann]

Am I correct in thinking that, in the last scenario, the voltage would read lower at the control panel end than the battery end because that is where the load is 'occuring'?

Yes. All looks good so far then ?

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[Richard n Ann]

I assume charge the batteries to full and then apply a known load over a set amount of time?

Yes again. ?

 

[HarryHamsta]

Yes. All looks good so far then ?

Excellent. I thought as much. I don't know what fixed it exactly. Crimp seemed fine although wire was a little corroded (old cable) so perhaps that. Both the chassis earths looked fine.

Side note, does my multimeter need replacing? When touching probes together resistance isn't 0 on lowest setting. Google says it should be. I'll admit I think its 10/15 years old.

Side side note, I always use the '200' setting on V (on the left with 2 lines under) when reading battery voltage. I've just read I should be using 20, is that right? If so then all my measurements from earlier post are incorrect

Maybe time for an online electronics course . . .

 

[Richard n Ann]

My multimeter reads 0.3 ohms I think when leads shorted so it's near enough.

If you use the 200 range you just get one decimal place less resolution so it's not wrong, just not as precise ?

 

[DBK]

With a load at the control panel end (10no 2W LED lights & 1no 25W halogen ext. light) then the voltage is lower (11.8) at the control panel than at the battery end (12.2).

Something is wrong. A voltage drop of 0.4 volts with just a 4A load suggests there is a resistance somewhere. Might be a corroded connection but on such a small load you shouldn't really be able to measure any voltage drop.

As for the batteries, given how you've been using them, discharging them down to about 50%, then they are possibly at the end of their life. It depends on what type of battery they are but if they are a typical lead acid battery then they might be only able to do this about two hundred times. You will got a longer life from gel batteries but they a significantly more expensive to buy although on a VFM basis they can be a good bet. Lithium batteries probably best of all but cost might rule them out for you.

You mentioned a B2B. This is a device which makes the alternator produce more current and charges the batteries much faster than can be done with a split charge relay. One could be an option for you as it will put in as much power with a thirty minute drive as you will get from a two hour or more drive with your current setup.

 

[rod_vw]

From what I read above there are a lot of people looking too deep into this problem. The OP has confirmed that when some high current appliances are switched on part of the older distribution circuitry suffers low voltage but the battery source voltage does not drop significantly. I get the impression that items on the 'new' distribution wiring do not suffer the same problem.

If the above assumptions are correct then the problem is almost certainly in excessive volt drop in the older circuitry remembering that the -ve (earth) return is just as important as the +ve wires. This could be anywhere but maybe careful consideration of which circuits are affected will reveal a common point.

I would be considering if all the affected items have a common -ve (earth) point, if so I'd find that and check it carefully.

It may be worth connecting a digital meter 'length-ways' along the +ve circuit. By that I mean use the meter on the 20v scale, connect the +ve test lead to the +ve pole of the battery and the -ve test lead a long way down one of the high current affected circuits then apply the offending load. Any significant reading will indicate that there is that amount of volt drop in that circuit. If / when this test shows a problem move the -ve test lead back to half way along the same circuit and test again. At the point that the indicated volt drop disappears you will know that you have passed the fault so back-track until it becomes obvious where the problem is.

I know that sounds complicated and may require a similar test on more than one part of the circuit including the -ve side but once you've got it in your head you will see what I'm getting at. Don't forget if you end up checking the -ve side to reverse the meter test leads (or simply observe numbers on the meter not the fact that some have a -ve sign before them).

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