Voltage drop when split relay connected to 13.3 down from.14.4

[ched999uk]

So after 16 hours of manual charge. My battery now reads 12.9. That’s without starting the engine. Is this ok? 

Anything above about 12.7v (rested i.e. after 4 hrs after charging) should be fully charged. The question is really about capacity. While a battery might appear to fully charge it's capacity might have been damaged. So just be aware that you ideally need to keep an eye on it to see if it's holding up to your usage. 

 

[spruce]

Anything above about 12.7v (rested i.e. after 4 hrs after charging) should be fully charged. The question is really about capacity. While a battery might appear to fully charge it's capacity might have been damaged. So just be aware that you ideally need to keep an eye on it to see if it's holding up to your usage. 

Exactly. At 3 1/2 years old your battery will have lost capacity. Ever time you draw power and recharge the battery looses a tiny amount of its capacity. You just help you battery last longer by keeping it as fully charged as possible as quickly as possible.

The problem we have as window cleaners @Jangois that there is no quick way of testing a leisure batteries capacity. The only way is to put a load on it and monitor the battery performance over an extended period of time. Theoretically drawing 5 amps from a fully charged 110amph battery should last 22 hours. Its not as simple as that though as there are other factors that need to be accounted for. But is a good guide.  But doing this robs the battery of one of its charging cycles.

A starter battery is different. You can put a very heavy load on it and in a short test can see how it performs watching voltage drop.

I had a problem with my nearly 7 year old 110 amph leisure battery. It had enough umph to drive two Shurflo pumps on and off through the day, but when I put a diesel heater onto it it 'died' after 5 or 6 starts. According to my battery monitor I had only drawn 15 amps from the battery. That shows how much capacity my battery had lost. It fooled us because we move the van regularly through the day, so it had a bit of a boost charge. I thought the battery was still ok. It wasn't.

 

[Jango]

I’ll keep an eye on things. I do have a backup battery in case. I keep that regularly charged even though not using it. Thanks @ched999uk and @spruce

 

[Quickwindowclean]

Hi @spruce and everyone else.

I done a lot more research regarding this 1 volt voltage drop. Firstly I double checked the other vehicle and the input across the system when the relay was connected was indeed 14.4. I changed the relay in the initial vehicle causing the problem and the voltage drop was still prominent 1 volt only when relay connected this means the leisure battery in question will never be able to be fully charged when driving.

The major difference in the initial van I noticed was extremely thick cables prob 32m at least

The best way to check your getting the right voltage is turn your switch on and just press the enter button to see it should read 14.4 if it reads less like 13.4 it means your battery is never going to be charged at capacity regardless how much driving you're doing.

I have contacted a 12-volt company and I'm hoping to get some info next week.

Can I just ask what millimetre cables is recommended in the system to the relay and where do you earth and what size cables recommended.

I also found out that some relays on the market didn't really have some sort of resistance and purposely trigger a 1v input drop I think it's supposed to be for safety reasons not sure.

If you check your input when relay connected you might be surprised you can also use a volt meter and check.

If anyone has any further info fire away meanwhile I'm looking forward to next week

Cheers.

 

[Quickwindowclean]

Hi @spruce and everyone else.

I done a lot more research regarding this 1 volt voltage drop. Firstly I double checked the other vehicle and the input across the system when the relay was connected was indeed 14.4. I changed the relay in the initial vehicle causing the problem and the voltage drop was still prominent 1 volt only when relay connected this means the leisure battery in question will never be able to be fully charged when driving.

The major difference in the initial van I noticed was extremely thick cables prob 32m at least

The best way to check your getting the right voltage is turn your switch on and just press the enter button to see it should read 14.4 if it reads less like 13.4 it means your battery is never going to be charged at capacity regardless how much driving you're doing.

I have contacted a 12-volt company and I'm hoping to get some info next week.

Can I just ask what millimetre cables is recommended in the system to the relay and where do you earth and what size cables recommended.

I also found out that some relays on the market didn't really have some sort of resistance and purposely trigger a 1v input drop I think it's supposed to be for safety reasons not sure.

If you check your input when relay connected you might be surprised you can also use a volt meter and check.

If anyone has any further info fire away meanwhile I'm looking forward to next week

Cheers.

And obviously I noticed the lack of power because before we were only running two pumps. Essentially the battery is never going to get a full charge regardless of how much driving you do. Those of you who have about 13.4 max throughout the system and only one a one pump and hardly bench charge it's because you're not drawing enough and you probably have a very good quality battery

So that charge is enough as it was for me.

 

[Iron Giant]

Anything above about 12.7v (rested i.e. after 4 hrs after charging) should be fully charged. The question is really about capacity. While a battery might appear to fully charge it's capacity might have been damaged. So just be aware that you ideally need to keep an eye on it to see if it's holding up to your usage. 

Totally agree, most of us stick a battery on charge overnight and it reads fully charged in the morning, but could be knackered and go from been fine for a full days work one day to going flat within a few hours the next day, this I have experience of by simply relying on a charger and not a multi-meter as an extra check as you simply don't know when a battery is at the point of been at the end of it's use, these were usually Halfords batteries after about 22 months of use if my memory serves me correctly.

 

[ched999uk]

As for cable size if you have a 3m cable run from battery through relay to battery and the relay is capable of 140 Amps and you want to minimise your voltage drop you would use 35mm2 cable or 2 Gauge. Lets face it though I would be surprised if you actually had more than 50amps through the cable so 16mm2 or 5 Gauge cable.

As for earthing you should use good thick cable, same as from battery to relay and earth to a solid part of chassis with bolt and serrated washer. 

Remember to fuse the cable as close to each battery as possible (2 fuses). The reason being is that if the cable shorts to earth you want a fuse to blow and disconnect the power to the cable asap. When a cable shorts it pulls lots of current and can cause the insulation or things close by to catch fire!!!

A 1v drop across a relay is very bad. It's just 2 contacts coming together so should have milliohms (thousandths of an ohm) resistance. I guess the contacts have burnt. The thing to watch is a high resistance contact will cause heat and could cause a fire. Sorry to keep on about fire but it is a danger on 12v stuff with batteries as they can discharge so much current so fast.

 

[Quickwindowclean]

As for cable size if you have a 3m cable run from battery through relay to battery and the relay is capable of 140 Amps and you want to minimise your voltage drop you would use 35mm2 cable or 2 Gauge. Lets face it though I would be surprised if you actually had more than 50amps through the cable so 16mm2 or 5 Gauge cable.

As for earthing you should use good thick cable, same as from battery to relay and earth to a solid part of chassis with bolt and serrated washer. 

Remember to fuse the cable as close to each battery as possible (2 fuses). The reason being is that if the cable shorts to earth you want a fuse to blow and disconnect the power to the cable asap. When a cable shorts it pulls lots of current and can cause the insulation or things close by to catch fire!!!

A 1v drop across a relay is very bad. It's just 2 contacts coming together so should have milliohms (thousandths of an ohm) resistance. I guess the contacts have burnt. The thing to watch is a high resistance contact will cause heat and could cause a fire. Sorry to keep on about fire but it is a danger on 12v stuff with batteries as they can discharge so much current so fast.

Hi.

Thanks

So we plugged in a brand new relay and it was still showing the 1 volt voltage drop across the entire system including before the relay.

The other van has 14.4 throughout the system. With much thicker cables I'm thinking considering both the relays gave a 1 volt drop it's probably something to do with the earthing and the thickness of cables?

Or even possible that it's something to do with the alternator type? 

 

[Quickwindowclean]

Hi.

Thanks

So we plugged in a brand new relay and it was still showing the 1 volt voltage drop across the entire system including before the relay.

The other van has 14.4 throughout the system. With much thicker cables I'm thinking considering both the relays gave a 1 volt drop it's probably something to do with the earthing and the thickness of cables?

Or even possible that it's something to do with the alternator type? 

I have a feeling that could be many split relay charge kits and cables that are not rated high enough for the maximum output of certain alternators of vehicles not sure tho.

 

[ched999uk]

Hi.

Thanks

So we plugged in a brand new relay and it was still showing the 1 volt voltage drop across the entire system including before the relay.

The other van has 14.4 throughout the system. With much thicker cables I'm thinking considering both the relays gave a 1 volt drop it's probably something to do with the earthing and the thickness of cables?

Or even possible that it's something to do with the alternator type? 

If you are putting a multimeter 0v probe on the same point when measuring either side of relay then it can't be the earth. If you are moving the 0v probe then you need to do more testing. 

If you measure voltage between the van battery 0v terminal and the leisure battery 0v it should measure 0v. If you get a voltage then you have poor earth. 

You could also disconnect the +12v cables at each end and measure resistance it should be very very low, less than an ohm ideally. 

Hope that helps? 

 

[Quickwindowclean]

If you are putting a multimeter 0v probe on the same point when measuring either side of relay then it can't be the earth. If you are moving the 0v probe then you need to do more testing. 

If you measure voltage between the van battery 0v terminal and the leisure battery 0v it should measure 0v. If you get a voltage then you have poor earth. 

You could also disconnect the +12v cables at each end and measure resistance it should be very very low, less than an ohm ideally. 

Hope that helps? 

Hi!

Almost can you say that again proofed for a novice! .

thanks a lot 

 

[spruce]

Hi.

Thanks

So we plugged in a brand new relay and it was still showing the 1 volt voltage drop across the entire system including before the relay.

The other van has 14.4 throughout the system. With much thicker cables I'm thinking considering both the relays gave a 1 volt drop it's probably something to do with the earthing and the thickness of cables?

Or even possible that it's something to do with the alternator type? 

If the voltage drop is now across the entire system on both sides of the relay, then the relay is fine. As @ched999uksays, the voltage drop between the starter battery side and the leisure battery side should be pretty much the same., not a 1 volt difference.

If you are now getting lower voltage at the starter battery side with the engine running then you have to trace back and find the problem. Is the voltage at the starter battery 14.4v? If your SCR is drawing power from this terminal then the cable starting at the starter battery must read the same. Check the voltage at the fuse before and after the fuse and then keep checking the cable.

@ched999ukalso said to thoroughly check the earth cables. If you are using the chassis as a return from the leisure battery, are those connectors making good contact?

What still bugs me is why the auto electrician didn't identify and solve the problem.

 

[spruce]

BTW, what van is it? Ford Transit Connects had an issue with a power cable under the battery box. The insulation started to break down and damp/water played havoc with the charging system.

 

[ched999uk]

Hi!

Almost can you say that again proofed for a novice! .

thanks a lot 

Basically on a multimeter all measurements are taken with ref to the 0v(black) probe. So if you measure the van battery across the terminals you get a reading. If you measured from a chassis point to the 12v terminal and you had a different (lower) reading then you have a poor earth. 

Check every connection and joint including fuse holders for both mechanical soundness and resistance. 

If you put the black multimeter probe on the input terminal of the relay and the red on the out (right next to relay) you should get 0v. Any higher then there is a poor connection between the probes. 

Hope that helps? 

 

[Quickwindowclean]

If the voltage drop is now across the entire system on both sides of the relay, then the relay is fine. As @ched999uksays, the voltage drop between the starter battery side and the leisure battery side should be pretty much the same., not a 1 volt difference.

If you are now getting lower voltage at the starter battery side with the engine running then you have to trace back and find the problem. Is the voltage at the starter battery 14.4v? If your SCR is drawing power from this terminal then the cable starting at the starter battery must read the same. Check the voltage at the fuse before and after the fuse and then keep checking the cable.

@ched999ukalso said to thoroughly check the earth cables. If you are using the chassis as a return from the leisure battery, are those connectors making good contact?

What still bugs me is why the auto electrician didn't identify and solve the problem.

Hi spruce the earth is short small black cable 3m? Going to the wheel arch is that an okay earth? The relay ofcourse is connected to the earth and that's when we get the 1v drop. Could the earth be the issue?

The auto electrician told me he's not experienced in relays and he wanted to investigate so he can learn to charge in future.

BTW, what van is it? Ford Transit Connects had an issue with a power cable under the battery box. The insulation started to break down and damp/water played havoc with the charging system.

Yes Ford connect but the power is drawn from one of the live cables in dash board and fused near there then about 1 meter away plugs into relay. This makes me think about what was mentioned regarding fuses need to be close however I recall we run a cable directly from the battery to the relay we had 14.4 but once the relay was connected which is also connected to the earth again we had 13.3

Basically on a multimeter all measurements are taken with ref to the 0v(black) probe. So if you measure the van battery across the terminals you get a reading. If you measured from a chassis point to the 12v terminal and you had a different (lower) reading then you have a poor earth. 

Check every connection and joint including fuse holders for both mechanical soundness and resistance. 

If you put the black multimeter probe on the input terminal of the relay and the red on the out (right next to relay) you should get 0v. Any higher then there is a poor connection between the probes. 

Hope that helps? 

 thank you for this everything seems to be pointing at the Earth first it's on the wheel arch I take it that's not a very good place and it's also only a 3 mil cable?

 

[ched999uk]

thank you for this everything seems to be pointing at the Earth first it's on the wheel arch I take it that's not a very good place and it's also only a 3 mil cable?

The leisure battery earth should be as thick as +12v cable from van battery. Both should be suitable for the max current. 3mm2 cable us rated about 33 amps. 

The position of the earth shouldn't matter as whole body is connected to van battery 0v terminal. But a good connection needs to be in contact with clean paint free metal! 

You mention that you have a connection under dash. Do you also have a cable from van battery to relay? 

One other thing, how new is van is it euro6? 

 

[Quickwindowclean]

The leisure battery earth should be as thick as +12v cable from van battery. Both should be suitable for the max current. 3mm2 cable us rated about 33 amps. 

The position of the earth shouldn't matter as whole body is connected to van battery 0v terminal. But a good connection needs to be in contact with clean paint free metal! 

You mention that you have a connection under dash. Do you also have a cable from van battery to relay? 

One other thing, how new is van is it euro6? 

Should both the cables be at least 16 mil or thicker as they're both only 3m the other van has very thick cables and its 14.4 when relay is connected.

The earth area has been sanded down but can double check.

Connection under dashboard from one of the live cables but the cable is delivering 14.4 also run a cable from the battery and got the same voltage all the way down the system but once the relay is connected and it's going through the Earth the maximum voltage before and after the relay as in the entire system is only 13.3 have also tested it with a different relay and have the same voltage same situation the funny thing is it's in the entire system so that means literally from the starter battery disconnect the relay and you have 14.4.

Like I say the previous van has very thick cables thick earth also and 14.4 reads throughout which is what I desperately need in this van there must be a reason because the other van is outputting correctly

 

[ched999uk]

Sounds like you have an ignition controlled relay. So the thin? Wire from under dash is so relay switches when ignition on. Some relays just have van batt (in) , leisure battery (out) and an earth. Others have an extra ignition wire that is just a thin control wire. 

If you are measuring a 1v drop across relay then as long as leisure battery is disconnected when testing then the loss can only be relay as long as the multimeter 0v probe is on same point when measuring. If the leisure battery is connected it could pull voltage down. 

It's a bit tricky as you say you swapped relay with new one and same v drop. 

All you can do is check all connections even the ones you think are OK. 

 

[Quickwindowclean]

Sounds like you have an ignition controlled relay. So the thin? Wire from under dash is so relay switches when ignition on. Some relays just have van batt (in) , leisure battery (out) and an earth. Others have an extra ignition wire that is just a thin control wire. 

If you are measuring a 1v drop across relay then as long as leisure battery is disconnected when testing then the loss can only be relay as long as the multimeter 0v probe is on same point when measuring. If the leisure battery is connected it could pull voltage down. 

It's a bit tricky as you say you swapped relay with new one and same v drop. 

All you can do is check all connections even the ones you think are OK. 

Sounds like you have an ignition controlled relay. So the thin? Wire from under dash is so relay switches when ignition on. Some relays just have van batt (in) , leisure battery (out) and an earth. Others have an extra ignition wire that is just a thin control wire. 

If you are measuring a 1v drop across relay then as long as leisure battery is disconnected when testing then the loss can only be relay as long as the multimeter 0v probe is on same point when measuring. If the leisure battery is connected it could pull voltage down. 

It's a bit tricky as you say you swapped relay with new one and same v drop. 

All you can do is check all connections even the ones you think are OK. 

Yes I swap the relay and the same voltage drop in the entire system.

I hope you're not bamboozled as well all connection seem to be fine can you recommend me a relay that you know it's definitely very good?

Sorry to ask but if you press the enter button on your switch are you seekng 14.4 while engine is running ? My other van is running at 14.4 it's just this one one must sorted out desperately need 14.4 throughout the system and the relay

 

[ched999uk]

I can't recommend a relay from personal experience but the 0-727-33 DURITE SPLIT CHARGE RELAY 12V 140A seem to be used by quite a few. 

It doesn't need an ignition control connection as it senses van batt voltage and then only connects leisure batt when van is charged. So it works a little different to your one. 

It is so difficult to remotely diagnose things and I wouldn't want to cost you unnecessary money. Do you have any mates that are into electronics or can use a multimeter? 

I would have said if there is a voltage drop then relay faulty but you tried a new one and exactly same issue. 

Might be a stupid question but is current system causing an issue? 

 

[Quickwindowclean]

I can't recommend a relay from personal experience but the 0-727-33 DURITE SPLIT CHARGE RELAY 12V 140A seem to be used by quite a few. 

It doesn't need an ignition control connection as it senses van batt voltage and then only connects leisure batt when van is charged. So it works a little different to your one. 

It is so difficult to remotely diagnose things and I wouldn't want to cost you unnecessary money. Do you have any mates that are into electronics or can use a multimeter? 

I would have said if there is a voltage drop then relay faulty but you tried a new one and exactly same issue. 

Might be a stupid question but is current system causing an issue? 

Hi

Thanks for advice. when you say current system in a way I've started noticing this only when it added the electric reels etc .I wasn't noticing it before as I had quite a basic setup is that what you meant?

In other words the lower voltage wasn't an issue as we will not drawing too much power but now it's a different situation.

I have that auto electrician guy who wants to learn so I've been passing on info to him and hes good with a meter.

 if you can continue to point me in the right direction I think I should sort it out. All I know is the other van is outputting 14.4 to the relay and everywhere so surely I'll have this sorted right now it's quite stressful but I'm sure believe we can figure it out.