DC to DC 12v chargers

[Kayos]

Anyone any experience of these?

I'm looking to add a second battery and inverter in the pickup but ive been reading that modern vehicles don't like twin batteries due to "smart" alternators. I have a split charge relay and isolator but don't really want to spend £150 plus if I don't need it

Anyone used one?

 

[qwakers]

https://www.ebay.co.uk/itm/12V-SPLI...137407?hash=item35b1da40ff:g:uKIAAOSw241Yich8

ive got the 24v to 12v version of that on my lorry to charge the accessory battery's. had no issues with it, it works well.

 

[hotponyshoes]

Some modern stuff has a "bodybuilder" power take off point.
Or if you have 13pin towbar electrics you can use the power feed from that.
Those connections are treated differently by the ecu monitor and you can fit a regular smartcharge/volt sense relay via them.

 

[Kayos]

Some modern stuff has a "bodybuilder" power take off point.
Or if you have 13pin towbar electrics you can use the power feed from that.
Those connections are treated differently by the ecu monitor and you can fit a regular smartcharge/volt sense relay via them.

I do have a 13 pin towbar as I've just had to buy a 7 pin adapter for the bike rack lights
Would it have enough power to keep a 110ah battery charged?
I will be using a 25mm cable and isolator to connect directly to the main battery if needed

 

[m_c]

The issue with smart alternators, is the voltage can vary from 12V to 15V, depending on conditions, which means a conventional split charge relay isn't guaranteed to cut in/out when it normally would. It's not that the alternator doesn't like the extra load.

Some manufacturers have tweaked the voltages of their conventional split charge relays so they cut in and out at a lower voltage, but it's a bit of bodge, and if you mix battery types, they won't get charged with the ideal voltages.

Personally if I was adding an auxiliary battery, I'd pay for something like a Sterling battery to battery charger, as they'll do whatever you need. You can set it so it cuts in/out with ignition or just battery voltage, and also set the charging profile for the extra battery.

 

[hotponyshoes]

I do have a 13 pin towbar as I've just had to buy a 7 pin adapter for the bike rack lights
Would it have enough power to keep a 110ah battery charged?
I will be using a 25mm cable and isolator to connect directly to the main battery if needed

You will have a fuse for pin 10 on the towbar. Amp rating varies but that will be the maximum you can charge at.
To avoid confusing the ecu/alternator you would use this as your charging current rather than fitting a 25mm cable and using the towbar for the switching source.

How much power do you need from the 2nd battery? What are you using it for?
Ideally you would charge a battery at about 10% of its capacity so 11amps of charging current would be about right.
25mm cable will probably take more than your alternator can put out so unless you plan to run whatever is connected to the second battery from the first battery as well it might be excessive.

 

[Barking Mat]

Never had any issues with alternators charging various packs of batteries, through split charge isolators, the traditional and newer types.

What do you mean by smart alternators?

I've fourteen boats and over 100 batteries in service, batteries go wrong, alternators die, it's rare. Don't see the problem?

The 12 to 15 volt issue is amperage dependant, an ampermetric clamp gives you a lot better idea what is going on than a volt meter. Most alternators kick out 13.8 volts, it's the amps which change.

Leave a fully charged battery 48 hours and test the volts, is a basic way of checking is condition.

 

[gordon stephenson]

Don't know about modern systems, I have run a number of cars in the past fitted with two batteries, just linked in parallel with welding cable, batteries of different sizes but never had a problem ever.

 

[Kayos]

You will have a fuse for pin 10 on the towbar. Amp rating varies but that will be the maximum you can charge at.
To avoid confusing the ecu/alternator you would use this as your charging current rather than fitting a 25mm cable and using the towbar for the switching source.

How much power do you need from the 2nd battery? What are you using it for?
Ideally you would charge a battery at about 10% of its capacity so 11amps of charging current would be about right.
25mm cable will probably take more than your alternator can put out so unless you plan to run whatever is connected to the second battery from the first battery as well it might be excessive.

A 1500w (continuous, 3000w peak) inverter

The 25mm cable goes to a 3 way isolator so the inverter is connected to the main, aux or both batteries. Charge wire is separate
Ran it like that in the Disco and it worked well, engine running if I needed electricity all day

 

[m_c]

Never had any issues with alternators charging various packs of batteries, through split charge isolators, the traditional and newer types.

What do you mean by smart alternators?

I've fourteen boats and over 100 batteries in service, batteries go wrong, alternators die, it's rare. Don't see the problem?

The 12 to 15 volt issue is amperage dependant, an ampermetric clamp gives you a lot better idea what is going on than a volt meter. Most alternators kick out 13.8 volts, it's the amps which change.

Leave a fully charged battery 48 hours and test the volts, is a basic way of checking is condition.

Smart alternators vary the voltage, depending on conditions. Or to be more precise, the battery management system in the vehicle will control the alternator output.

A typical modern vehicle system might only output only 12 and a bit volts after starting, to allow the battery a chance to recover.
Voltage can then sit that low until the vehicle is driven, at which point the regenerative braking conditions will kick in, with the alternator load reduced under acceleration, and increasing under deceleration, which means depending on what type of battery is fitted, output voltage can continually change between 12-13 and 15-16V.

Flooded battery systems will typically see larger voltage changes, as the battery management system will increase voltage to force them to charge faster, whereas an AGM doesn't need as high a voltage for the battery to absorb charge (a flat AGM battery can burnout conventional alternators due to how quickly they'll absorb charge).

 

[Barking Mat]

Surely a smart alternator senses the voltage of the battery and adjusts the amps per se.

A discharged battery will get given high amps at lower voltage, and when fully charged get higher volts at a lower amperage.

Is my understanding.

Or has technology advanced and I'm missing something.

Always willing to learn...

 

[m_c]

Surely a smart alternator senses the voltage of the battery and adjusts the amps per se.

A discharged battery will get given high amps at lower voltage, and when fully charged get higher volts at a lower amperage.

Is my understanding.

Or has technology advanced and I'm missing something.

Always willing to learn...

Ye olde alternators simply work on maintaining the voltage.
Discharged battery = more amps. Charged battery = less amps.

Now, the alternator can vary it's output, and tell the BMS how much load it's under.

Sterling power actually have a good document on it - https://cdn.shopify.com/s/files/1/0658/7343/files/page17_RegenBraking.pdf?14861364839234428801

 

[Barking Mat]

Ahh, New technology, I'm not familiar with. Thanks.
That explains things...

 

[sako243]

Surely a smart alternator senses the voltage of the battery and adjusts the amps per se.

A discharged battery will get given high amps at lower voltage, and when fully charged get higher volts at a lower amperage.

Is my understanding.

Or has technology advanced and I'm missing something.

Always willing to learn...

It's a bit of a misnomer I think calling it a smart alternator. Most smart alternators are actually just alternators that accept a PWM input to regulate their output, it's the vehicles ECU that's the smart bit.

The first group of manufacturers to introduce it were Volvo, JLR, Merc and BMW if I remember correctly. The main point of the system was to improve fuel efficiency. The idea being that rather than immediately starting to recharge a battery the car waits until its more efficient to do so, i.e. under braking, equally when it's not ideal (e.g. when accelerating) it can be disconnected to maximise power going to accelerating.

On the higher end vehicles alternators can be 250A which if chucking out that current means about a 4hp load on the engine. Obviously not ideal for efficency if that's happening when going up hill, accelerating or just idling. If you wait until you're engine braking or physically braking then it's 4hp that can be recovered rather than literally going up in smoke (or at least brake dust).

There have been many side effects, one being that you can also more intelligently charge the battery now resulting in better battery life (what most of the posts have been referring to). In my opinion at least the smart alternator refers to the system I described above (efficiency ones) but I think these days it's applied to all sorts. In the classic ("my") definition it shouldn't matter about dual batteries.

It's not that new a technology, after all I did my masters on it 10 years ago...

 

[Kayos]

It's a bit of a misnomer I think calling it a smart alternator. Most smart alternators are actually just alternators that accept a PWM input to regulate their output, it's the vehicles ECU that's the smart bit.

The first group of manufacturers to introduce it were Volvo, JLR, Merc and BMW if I remember correctly. The main point of the system was to improve fuel efficiency. The idea being that rather than immediately starting to recharge a battery the car waits until its more efficient to do so, i.e. under braking, equally when it's not ideal (e.g. when accelerating) it can be disconnected to maximise power going to accelerating.

On the higher end vehicles alternators can be 250A which if chucking out that current means about a 4hp load on the engine. Obviously not ideal for efficency if that's happening when going up hill, accelerating or just idling. If you wait until you're engine braking or physically braking then it's 4hp that can be recovered rather than literally going up in smoke (or at least brake dust).

There have been many side effects, one being that you can also more intelligently charge the battery now resulting in better battery life (what most of the posts have been referring to). In my opinion at least the smart alternator refers to the system I described above (efficiency ones) but I think these days it's applied to all sorts. In the classic ("my") definition it shouldn't matter about dual batteries.

It's not that new a technology, after all I did my masters on it 10 years ago...

Newness is relative, its a 2015 L200 but its a Euro 5 engine and a few people I've seen have had issues with the second battery not charging.

I think the DC to DC is looking like a must have, more expense.....

It will be worth it though, I could go weeks or months and not touch the inverter when it was in the Disco, but when I needed it I really needed it

 

[8ob]

It's not that new a technology, after all I did my masters on it 10 years ago...

Interesting stuff in there Ed, makes sense.

Ed ten years ago.

 

[m_c]

@sako243 there have been different variations of "smart" alternators, but most now are LIN bus controlled.
They can tell whatever is controlling the battery management what load they're under, and if they're faulty, as well as changing their output as requested.

 

[qwakers]

for use with a constant current draw like a inverter you”re going to want a higher amp output than the one i linked...

 

[sako243]

@sako243 there have been different variations of "smart" alternators, but most now are LIN bus controlled.

Much of the sameness I'd expect. There's no point building in the smart charging aspects into the controller on the ECU - rather than being PWM to control the output it'll be a LIN message to set it output. Has the benefit the alternator can also report diagnostics such as RPM and temperature back.

Although admittedly I haven't looked into it but it's how I'd expect it to be built.

 

[sako243]

Ed ten years ago.

Not far off except there would have been a gun in my hand as well