Technical Split charge problems

[Bearstrangler]

Hi, i beyter syart this off with holding my hands up to a, being clueless and b, doing a shoddy job when installing my electrics /split charge relay.

Heres the thing, it worked fine for 3 years. Then for no apparent reason there was a birning smell(fuse melted between scr and leisure battery). I put a multimeter over the main battery and it wasnt charging so assumed probably alternator. At this point the engine was revving high. Took it to a gargae and said,"probably alternator but your the experts, do your tests and decide fornyourself". They changed the alternator and declared it fixed. Anyway, i picked it up and it was still revving high. Now it revs high forr a short period but then revs drop and it appears to be charging. Im not convinced its charging the leisure batteriea though as they seem to go flat very quickly.

If someone could steer me in the direction of somewhere to start that would be great. I have very basic understanding of using a multimeter. Thanks.

 

[Googlebot]

Firstly, it could be a number of things.

What leisure battery is it? Lead acid or lithium?

How old is the leisure battery?

No loads on the leisure battery and engine off, you should see 12.7 volts. Engine on, you should see about 13.5 to 14 volts for lead acid.

 

[ZaphodB]

Don't underestimate the ground connections on any vehicle. it's absolutely just as important as the 12v cable.

You could for instance measure at the alternator that it's outputting correctly and then find it's 'weirdly' not getting to the battery.....

Bad earths are often why brake lights start lighting up weirdly for instance., bad earths are often why batteries don't charge, or starters don't crank fast., and often why alternators (and starters) are wrongly replaced , cos whoever hasn't done their homework.

 

[Kahcorp]

First disconnect leisure battery from start battery & sort the start battery issue separately.

 

[the green vanper]

First disconnect leisure battery from start battery & sort the start battery issue separately.

Totally agree with you.

Then, we have no knowlegde what kind of motorhome is that, on which generation of the Ducato is based, and what's the setup / type of the batteries.

 

[Bearstrangler]

Firstly, it could be a number of things.

What leisure battery is it? Lead acid or lithium?

How old is the leisure battery?

No loads on the leisure battery and engine off, you should see 12.7 volts. Engine on, you should see about 13.5 to 14 volts for lead acid.

Hi, so they are 130ah lead acid in parallel and around 2 years old. Ive had them out and charged them and they are holding 12.9v on the multimeter. If i connect them up to the split charge relay and start the van the reading actually drops to 12.5 like they are under load.

Usually after about a minute the engine revs drop and then the digital display on the leisure battery switch board show 13.5 ish i think.

If i disconnect the fuse to make the leisure battery/split charge circuit redundant the engine revs and charges the starting battery just fine.

 

[Bearstrangler]

Don't underestimate the ground connections on any vehicle. it's absolutely just as important as the 12v cable.

You could for instance measure at the alternator that it's outputting correctly and then find it's 'weirdly' not getting to the battery.....

Bad earths are often why brake lights start lighting up weirdly for instance., bad earths are often why batteries don't charge, or starters don't crank fast., and often why alternators (and starters) are wrongly replaced , cos whoever hasn't done their homework.

Ok the start battery earth to the chasis looks pretty green, ill check that. And the earth from the split charge relay as well i suppose?

 

[AsdaPricey]

Hello @Bearstrangler

From personal experience that solitary braided earth lead is the cause of so many issues, so yes cleaning contact points and/or replacing earth cables is a good shout.
Confidence in powers and grounds are a must before delving any deeper.

On my Ducato I not only changed the braided lead but also added two extra earth leads - one in the engine bay , and a second in the battery tray.
Before that my split-charge relay was chattering away as voltage demand and supply fluctuated.
After that normal service was resumed and now it spins over quicker on the starter.

 

[Googlebot]

If it’s a smart alternator, they don’t work well with split charge relays. Effectively they just connect the batteries together to make one big battery. On modern vehicles, the alternator only gives out charge when needed so they don’t tend to charge leisure batteries well.

It sounds like they are fine, I would recommend putting a known load on them and take them down to 50% charged. So for example a 65 amp load for one hour, then check the voltage after leaving it for an hour. It should be 12.1 volts or above if the battery is decent.

How old is the van?

 

[Bearstrangler]

If it’s a smart alternator, they don’t work well with split charge relays. Effectively they just connect the batteries together to make one big battery. On modern vehicles, the alternator only gives out charge when needed so they don’t tend to charge leisure batteries well.

It sounds like they are fine, I would recommend putting a known load on them and take them down to 50% charged. So for example a 65 amp load for one hour, then check the voltage after leaving it for an hour. It should be 12.1 volts or above if the battery is decent.

How old is the van?

Its a 2007 van. The thing is it was fine for 3 years or so and then stopped working. I.tried this evening.to.get to grips with it. Its an intermittent fault, it seems to sort itself out after a minute or so of driving.

 

[Googlebot]

I would test the batteries then and go for the suggested earth straps.

Let us know how it goes.

 

[the green vanper]

Correctly charged lead acid batteries should in my opinion show more than 12,9 V.

Nominal voltage of a single cell is 2,2 V. We've got 6 cells, which makes 13,2 V.

Alternators usually are unable to fully charge the batteries as they are limited to 14,4 V, and to assume proper charging and desulfurization a lead acid battery should be charged with a higher voltage, which means a lead acid battery should be from time to time charged from another source than tthe vehicle alternator, usually a dedicated charger hooked up to mains. I don't recommend cheap 'smart' chargers, as they are unable to produce a sufficient electrolyte density.

As for adding / replacing the earth straps, I'm buying a good quality copper welding cable of the proper diameter in a welding hardware shop. They usually also have terminals and crimping tools, so they are able to crimp the terminals on the cable. It's necessary to know the length. And add heatshrink tube on the connection afterwards.

You've got 2 batteries connected in parallel. Is the wiring of the same length and diameter?