B2B Charger’s Ability to Supply House Load

[machineage]

I’m looking to add a second battery to my vessel. Currently it is one battery supplying the starter & all loads. I have been looking into B2B chargers but it has raised a question… Everything aside from the starter motor will move over to the house battery. So as I see it the B2B charger must be able to output sufficient current to handle these loads as well as charge the house battery if depleted. I was initially looking at the Ctek D250S but I see this is only rated for 20A - nowhere near enough. So I am currently looking at the D250S + SmartPass or the Sterling 60 / 120A B2B chargers. I wondered what people are using here with success and what your house loads (amps) are?

Thanks

 

[Tranona]

Not clear what you are trying to achieve. The common arrangement is to have 2 banks, a start bank with a relatively small battery just for starting the engine and a second, larger bank for "house" - that is all the boat's systems. the size of this bank depends on what you expect to draw. So, if you have a large draw such as fridge, autopilot, use lighting for long periods, you would have a larger capacity bank. Both banks are then normally charged from the engine alternator through some form of split charge device such as a VSR. Each bank has a separate isolator switch and maybe a parallel switch so the house could be used to start the engine. In addition a mains charger is useful if you have access to shorepower. A simple one will charge just the house bank, this is usually the one that needs it, but most types for boats have more than one output so can charge the start battery as well. supplementary charge can also be from solar panels or wind generators which reduce the reliance on using the engine or shorepower. If you have this type of set up you do not need a B2B charger.

 

[RobbieW]

I think I'd be starting somewhere different, given what you tell us you want to do. Some more info on battery and alternator capacities would help and what sort of boat, to get an idea of the likely loads.

On my boat the working load is usually 6-10 amps, thats running fridge, instruments, autopilot etc. It'll go higher running the windlass or water pumps but those are more transient loads. I dont expect the charger to cope with the transients, thats what the battery is there for, but you do need to be putting more in overall than you take out to charge.

The simplest solution would be to add a splitter, a VSR or similar, to share alternator output (if thats the charge source) between the two batteries. After that there are many ways to go, somewhat depending on the number of charge sources (alternator, solar, wind, mains) you have available. If you want something more sophisticated that will provide appropriate charge to the two batteries from the alternator, the Sterling A2B charger is a possible solution.

I have a small B2B that charges the engine battery from the house but its more often disconnected than not at the moment as with the boat in limited use it just drains the house for no good reason.

 

[RupertW]

Agree with the others that you have no need to mains charge the starter battery - it will look after itself with the engine charging it, either by 12B switch (if you are very familiar with electrics and will be the only person touching it), or a VSR (or equivalent) to keep the domestic bank charging too.

Then the mains charger can charge up the domestic bank whenever the engine hasn't run long enough to keep it topped up, especially when living on the boat in a marina. Our 20A charger has been plenty for a 42 foot boat sometimes with 6 or 8 people on it, big fridge and hungry autopilot.

 

[PaulRainbow]

I'd agree with much of what's already been said. We need to know more about your boat and equipment etc. You'll need a hefty battery bank and some equally hefty loads to justify a 60a charger, i doubt you have either, as you have been managing with just one battery.

 

[machineage]

Thanks guys

Indeed more information should have been forthcoming…
The vessel is a hovercraft - the engine has an 80A alternator. Here are some readings taken with the engine running for loads which could potentially be drawn simultaneously:

Engine (ECM / EFI Pump / S.I): 10A
Instruments + backlights: 2A
Nav Lights & Beacon: 1.5A
Windscreen Wiper (fast): 9.5A
Cabin Heater Fan (fast): 8A
Class D Power Amp: 7A

I guess a VSR would do the job and a mains charger to fully charge the batteries when at home. As an aside whilst looking at VSRs I wonder if anyone has come across this unit from Manson? It has programmable activate / deactivate voltages and delay settings along with a manual override:

http://www.manson.com.hk/products/detail/273

Thanks again

 

[William_H]

Thanks guys

Indeed more information should have been forthcoming…
The vessel is a hovercraft - the engine has an 80A alternator. Here are some readings taken with the engine running for loads which could potentially be drawn simultaneously:

Engine (ECM / EFI Pump / S.I): 10A
Instruments + backlights: 2A
Nav Lights & Beacon: 1.5A
Windscreen Wiper (fast): 9.5A
Cabin Heater Fan (fast): 8A
Class D Power Amp: 7A

I guess a VSR would do the job and a mains charger to fully charge the batteries when at home. As an aside whilst looking at VSRs I wonder if anyone has come across this unit from Manson? It has programmable activate / deactivate voltages and delay settings along with a manual override:

http://www.manson.com.hk/products/detail/273

Thanks again

From your list there is no reason why the engine load, windscreen wiper,instruments and nav lights should be run from the second house battery. They are all loads only applicable when the engine is on. So load is on the alternator directly.
The concept of a separate battery for house loads is to give a battery which can be isolated from engine start and discharged when camping on board for long periods without engine run. The B2B charger is designed to isolate this battery from essential engine services but still have auto charge when engine is running. A VSR also does that as do isolation diodes. The B2B also has the ability to charge the second battery at a rate faster than that which the battery will charge under normal 14v alternator voltage. So hit the battery with 16v you will charge it at a higher rate than 14v. So reducing the need for long engine runs for battery charging. Now this can also be achieved by fitting a smart regulator to the alternator which makes it produce the 16v. But this requires surgery to the alternator. NB the high voltage on both systems reduces to 14v when the battery is sensed to be full charged.
However in a B2B in producing 16v from 14v you must pull more current from the alternator like about 20% more to cover inefficiencies in the B2B converter.
The advantages of the smart charge system (B2B or alternator regulator or even mains charger) are less significant if you have a large bank of house batteries because the larger the battery the more current it will take in charging even at 14v.
Anyway my guess is that in a hovercraft you do not need a second isolated battery for engine start so no need for VSR or B2B just be a bit careful of electrical loads with engine not running. Unless you want to run the heater for long periods before engine start. In which case you want an extra battery and VSR. I expect you would run the engine for long periods so extra battery will easily charge on just alternator via VSR. olewill

 

[PaulRainbow]

Thanks guys

Indeed more information should have been forthcoming…
The vessel is a hovercraft - the engine has an 80A alternator. Here are some readings taken with the engine running for loads which could potentially be drawn simultaneously:

Engine (ECM / EFI Pump / S.I): 10A
Instruments + backlights: 2A
Nav Lights & Beacon: 1.5A
Windscreen Wiper (fast): 9.5A
Cabin Heater Fan (fast): 8A
Class D Power Amp: 7A

I guess a VSR would do the job and a mains charger to fully charge the batteries when at home. As an aside whilst looking at VSRs I wonder if anyone has come across this unit from Manson? It has programmable activate / deactivate voltages and delay settings along with a manual override:

http://www.manson.com.hk/products/detail/273

Thanks again

You could only draw all of those loads simultaneously if the engine was running, the alternator will keep up with all of that. For house loads you can discount most of the loads you list there. I would fit a 100a 2 output Victron ArgoFET low loss splitter. This is connected to the alternator output and each battery bank and will allow the alternator to charge all batteries, whilst keeping the two banks separate. I see no good reason for a B2B.

Whilst connected to shore power you only need to worry about the house loads. Some solar power might be suitable, but a 30a mains charger connected to the house bank should be fine on its own. I'd look at a Victron charger for that purpose. Either a Blue Power IP22 or a Blue Smart IP22. This will charge the batteries and will also act as a 30a power supply, running up to 30a of load whilst keeping the batteries charged.

It would make sense to connect each battery/bank to its own isolator switch, with a 3rd switch for emergency use if a battery failed.

 

[machineage]

Thank you for the replies

You know I hadn't even considered the MOSFET splitters / isolators... These do indeed look like a viable option. Does anyone here have experience of the ArgoFET? I see they quote a voltage drop of 0.02v at low current draw and 0.1v at 'higher currents' without actually giving any figures for those 'higher currents'. I see also there are various manufacturers of similar MOSFET based devices (Mastervolt, Amperlfex, Cristec, Durite, ProMariner & Vetus). My alternator has a voltage sense input so I could tie this to the input of the splitter if required.

I have also been reading about Sterling's Pro Split R. Sterling talk down the MOSFET devices stating as an example of voltage drop: 'Mastervolt battery mate is as high as 0.6V at full power (where it counts) while the Sterling is at 0.09V, a 500% performance improvement over the Mastervolt battery mate unit. '

I'm wondering having read the info if the Pro Split R's are software controlled solid-state relays?

Thanks again