B2B charger and mains charger running together?

[Travelling Westerly]

My current setup for charging my start and house battery is via a mains powered Sterling 30A smart charger dual output connected to the start and house battery for when on dock mains supply. When engine is on the alternator is charging the start and house via a Victron Argo Diode battery isolator so pretty standard stuff so far.

I understand that I can gain a more complete charge for my house battery by using a B2B charger rather than the alternator. I understand how the B2B works but think I have spotted an issue in that when Im on the mains charger (engine not running) the dual output will be charging both batteries and hence the B2B charger will see the charge input on the starter battery, think the engine is running, and will then try to charge the house battery at the same time? Have I got this right?

If I go this route do I need to disconnect the mains charger output to the house battery and just use it to charge the start battery and let the B2B to take care of the house battery? How do others use a B2B charger and is the extra money spent on this B2B worth it as opposed to just charging both via the alternator?

 

[jiris]

When you are charging battery from two sources, none of them is being able to tell if the voltage detected is a real BV or a voltage "topped" by the other system. It will adjust the current in accordance to the detected voltage. In the lower region both systems will reduce their currents somehow and will charge the battery in accord - no danger of any harm. When approaching the top, the difference (there will always be some) between setting in the systems will show. One of them will get to float charge while the other may still be delivering higher current. Further on one of them will stop charging completely leaving all "in the hands" of the other. No problem I could see - I've been using solar, wind gen, mains charger and engine alternator together for years. Obviously, all the system have to have reliable controllers. If you have any preference which system is supposed to finish the job, some tweaking may be required.

 

[Poey50]

I agree with jiris but if you want an easy manual over-ride you can use option 3 (page 6 of the B2B manual). This is usually wired into the ignition but you can simply wire it to the engine battery and add an on / off switch. Option 3 needs to see 13.2 volts AND power on this additional wire in order to wake up the B2B. It's good kit and warrantied units are still on clearance last time I looked.

 

[duncan99210]

Why not fit an alternator to battery charger? It would replace the diode pack for isolating the banks and once the engine battery has been topped off it prioritises the domestic bank. It also does not interfere in any way with the mains charger. I’ve had one fitted for about 5 years now, works a treat.

 

[Travelling Westerly]

Thanks guys, like the the idea of fitting an isolator to the B2B. That way I can turn on/off as required.

 

[Travelling Westerly]

Why not fit an alternator to battery charger? It would replace the diode pack for isolating the banks and once the engine battery has been topped off it prioritises the domestic bank. It also does not interfere in any way with the mains charger. I’ve had one fitted for about 5 years now, works a treat.

Ah this is new to me. I thought the B2B was similar. I'll Google this type of charger. Cheers

 

[Travelling Westerly]

Thanks Duncan. A2B looks like it will fit my requirements far better! Good call. Thanks again

 

[PaulRainbow]

What alternator do you have and how much do you use alternator charging ?

 

[Travelling Westerly]

Hi Paul

It's a brand new Volvo D2 50. I think looking at the sales blurb it has a 120a alternator.

I do quite a bit of motoring and that's why I wanted a more efficient charge profile for the house battery. It is also a brand new Bosch 240a single

 

[pvb]

It's a brand new Volvo D2 50. I think looking at the sales blurb it has a 120a alternator.

I do quite a bit of motoring and that's why I wanted a more efficient charge profile for the house battery. It is also a brand new Bosch 240a single

The standard Volvo Penta alternator charges at about 14.5v, so you won't achieve much improvement by adding an alternator-to-battery charger.

 

[Travelling Westerly]

The standard Volvo Penta alternator charges at about 14.5v, so you won't achieve much improvement by adding an alternator-to-battery charger.

Ah OK that's a shame then. Looks like it won't do what I wanted.
The Sterling site said it would charge upto 5 times faster and get 100% SOC as opposed to 80% on the alternator. Is this using a smaller alternator than mine do you think?
Cheers

 

[pvb]

Ah OK that's a shame then. Looks like it won't do what I wanted.
The Sterling site said it would charge upto 5 times faster and get 100% SOC as opposed to 80% on the alternator. Is this using a smaller alternator than mine do you think?
Cheers

The important words there are "up to"! Older alternators often worked at a somewhat lower voltage (often 13.8 to 14.0v), and additionally people were fond of installing diode splitters, which further reduced the charge voltage reaching the batteries. In these circumstances, an add-on booster was an advantage, which is why the Sterling and Adverc add-on regulators became so popular.

The Sterling Alternator-to-Battery Charger is a different kettle of fish, as it not only boosts the charge rate, but it has a built-in splitter. It can also drop the voltage to a genuine float rate - something which the old add-on regulators couldn't do. Many boatowners today use maintenance-free batteries or AGM batteries, and the Sterling charger will charge these at around 14.4 to 14.6v, virtually the same as your new engine's alternator, which is why I suggested it wouldn't be much of an improvement.

 

[Travelling Westerly]

The important words there are "up to"! Older alternators often worked at a somewhat lower voltage (often 13.8 to 14.0v), and additionally people were fond of installing diode splitters, which further reduced the charge voltage reaching the batteries. In these circumstances, an add-on booster was an advantage, which is why the Sterling and Adverc add-on regulators became so popular.

The Sterling Alternator-to-Battery Charger is a different kettle of fish, as it not only boosts the charge rate, but it has a built-in splitter. It can also drop the voltage to a genuine float rate - something which the old add-on regulators couldn't do. Many boatowners today use maintenance-free batteries or AGM batteries, and the Sterling charger will charge these at around 14.4 to 14.6v, virtually the same as your new engine's alternator, which is why I suggested it wouldn't be much of an improvement.

Thanks very much PVB looks like I'll spend my cash on my solar install which was my plan B

 

[TernVI]

The A2B charger can charge at up to 14.8V, and can do voltage sensing at the battery, along with temperature sensing.
So at some states of charge, I can well believe it might charge five times quicker.

 

[pvb]

The A2B charger can charge at up to 14.8V, and can do voltage sensing at the battery, along with temperature sensing.

Yes, the voltage setting for open lead-acid batteries is 14.8v, but wet batteries are falling out of favour and many people prefer AGMs or maintenance-free batteries, for which the voltage settings are lower.

 

[PaulRainbow]

The standard Volvo Penta alternator charges at about 14.5v, so you won't achieve much improvement by adding an alternator-to-battery charger.

This is why i asked the questions, i agree with you.

 

[PaulRainbow]

Thanks very much PVB looks like I'll spend my cash on my solar install which was my plan B

That's what i would do.