Domestic- starter charging query

[Daydream believer]

I have been researching a new smart charger for my boat. 2- 90 ah AGM domestics & 1 redflash AGM 24ah starter. Connected with a cyrix VCR
The engine starts at the press of a button, so the starter battery gets charged by the engine easily.
Most chargers have 1 or 3 terminals , but when I enquire about them they do not seem to regulate the output to the batteries individually. ie they all go "bulk" then they all go "float" etc
Victron & Dolphin show the charger connected to the domestics. The current presumably flows across to the starter.
But as my alternator is rigged to charge the starter first that does not need so much of a charge, plus it is smaller.
When I arrive in port & plug in shore power the charger senses the domestics are very low so starts a bulk phase. Presumably the starter gets this as well. Even though it does not need it.
So what happens to the starter battery. Does it get cooked over time or does it reject the charge. Should there be some switch system to stop it once the starter is full
If the charger is fitted to the starter presumably the domestics get cut off before their time because the starter tells the charger " I am full"
So what happens & how does one do it, because as far as I can see, none of the lower cost ( sub £ 400) battery chargers, that I have looked at, deal with starter as a separate item

 

[Tranona]

Your starter battery will not need any charge if you have run the engine for minutes after starting it, particularly a Red Flash which has a high acceptance rate and low self discharge rate. That is what you pay the money for. Really no need to connect the shore charger to the start battery. I am fitting just a single output shore charger in my new installation (190Ah AGM house bank) as that is the bank that gets the big drain and benefits from shorepower top up. However I am sure some 3 output ones do allow individual profiles. As belt and braces make sure you can use your house bank to start the engine either through switching or paralleling.

 

[Daydream believer]

Fair comment but I checked with victron energy & they say their basic range of starters do not have facility for individual profile. The chapI spoke to actually reng off & checke then rang me back to confirm that. But the second point is that I wonder if the charge will travel down the cyrix VCR to the starter battery if the starter is not directly connected

 

[Tranona]

Pretty sure the charger should be connected direct to the batteries - that is the point of having separate outlets. That is how I am wiring mine. Negative to the common negative busbar which is downstream of the shunt for the monitor so that it registers the charge and positive to the house busbar before the isolator.

 

[Daydream believer]

Actually my old 3 wire charger was connected directly to the -ve line between batteries & shunt & one +ve to the domestic bank & one +ve to the starter battery . But I knackered a red flash battery just out of warranty.
I wanted a charger that monitored BOTH banks but that does not seem possible
I am still worried that even with only the domestic connected to the charger, putting power into the domestics will indirectly put an excessive charge into the starter
My engine alternator charges the starter, then the domestics ( which is the norm I think) so they need to be linked, so I need the VCR between them to stop the domestics accidentally draining the starter too much. But I think that means a charge will go from domestics to starter when on shore power & over charge the starter
From what you say it seems you may have the same issue.

 

[VicS]

Actually my old 3 wire charger was connected directly to the -ve line between batteries & shunt & one +ve to the domestic bank & one +ve to the starter battery . But I knackered a red flash battery just out of warranty.
I wanted a charger that monitored BOTH banks but that does not seem possible
I am still worried that even with only the domestic connected to the charger, putting power into the domestics will indirectly put an excessive charge into the starter
My engine alternator charges the starter, then the domestics ( which is the norm I think) so they need to be linked, so I need the VCR between them to stop the domestics accidentally draining the starter too much. But I think that means a charge will go from domestics to starter when on shore power & over charge the starter
From what you say it seems you may have the same issue.

Could you consider a low loss splitter such as a Victron Argofet, instead of the VSR, to split the alternator output between the two batteries and connect the battery charger to the domestic battery only.
That would avoid any problem of overcharging the Red flash starter battery with the charger while maintaining the alternator"s ability to charge both.

 

[Daydream believer]

I will look that one up.

 

[andsarkit]

How about a separate small charger for the Redflash such as a small CTEK? You would then only need a cheaper single output main charger.
I'm not sure if you would have to disable /disconnect the Cyrix to stop it connecting the batteries and upsetting the charging sequence.

 

[ChromeDome]

NOCO charge and maintain the channels independently. Their GEN and GENPRO series are rugged for e.g. marine use.

I believe they are more "fit and forget" than some of the highly complex, app managed and monitored, gadgetty things. But I could be wrong ?

Have their Genius 26000 in the garage and am impressed.

 

[VicS]

How about a separate small charger for the Redflash such as a small CTEK? You would then only need a cheaper single output main charger.
I'm not sure if you would have to disable /disconnect the Cyrix to stop it connecting the batteries and upsetting the charging sequence.

It's not charging the Red Flash that's the perceived problem. It's stopping the charger for the domestic battery overcharging it via the VSR
You can disable a VSR by fitting a switch in its negative connection and switching if off, in this case when the batterycharger is in use but it's another thing to remember to do and to switch on again so that the alternator charges both batteries.. Best therefore regarded as an emergency feature only.

It might be possible to find a single sensing VSR that can be be connected to sense the starter battery only but all the modern electronically controlled VSRs seem to be dual sensing.

 

[Tranona]

Actually my old 3 wire charger was connected directly to the -ve line between batteries & shunt & one +ve to the domestic bank & one +ve to the starter battery . But I knackered a red flash battery just out of warranty.
I wanted a charger that monitored BOTH banks but that does not seem possible
I am still worried that even with only the domestic connected to the charger, putting power into the domestics will indirectly put an excessive charge into the starter
My engine alternator charges the starter, then the domestics ( which is the norm I think) so they need to be linked, so I need the VCR between them to stop the domestics accidentally draining the starter too much. But I think that means a charge will go from domestics to starter when on shore power & over charge the starter
From what you say it seems you may have the same issue.

If you wire it like I plan there is no connection between the 2 banks . No different from attaching a free standing battery charger direct to the house bank which is what I do at the currently as the wiring for the switch cluster (which has the VSR) is not yet installed.

 

[Daydream believer]

If you wire it like I plan there is no connection between the 2 banks . No different from attaching a free standing battery charger direct to the house bank which is what I do at the currently as the wiring for the switch cluster (which has the VSR) is not yet installed.

I am assuming the alternator is connected to one bank( usually the starter)---So if they are not connected , how does the alternator charge both battery banks when motoring?

 

[IanCC]

I have been researching a new smart charger for my boat. 2- 90 ah AGM domestics & 1 redflash AGM 24ah starter. Connected with a cyrix VCR
The engine starts at the press of a button, so the starter battery gets charged by the engine easily.
Most chargers have 1 or 3 terminals , but when I enquire about them they do not seem to regulate the output to the batteries individually. ie they all go "bulk" then they all go "float" etc
Victron & Dolphin show the charger connected to the domestics. The current presumably flows across to the starter.
But as my alternator is rigged to charge the starter first that does not need so much of a charge, plus it is smaller.
When I arrive in port & plug in shore power the charger senses the domestics are very low so starts a bulk phase. Presumably the starter gets this as well. Even though it does not need it.
So what happens to the starter battery. Does it get cooked over time or does it reject the charge. Should there be some switch system to stop it once the starter is full
If the charger is fitted to the starter presumably the domestics get cut off before their time because the starter tells the charger " I am full"
So what happens & how does one do it, because as far as I can see, none of the lower cost ( sub £ 400) battery chargers, that I have looked at, deal with starter as a separate item

Battery to battery charger from domestics to starter?

 

[Daydream believer]

Battery to battery charger from domestics to starter?

If you are asking then yes. That is how victron show it in their wiring diags. It has been shown on the forum a couple of times

 

[andsarkit]

It's not charging the Red Flash that's the perceived problem. It's stopping the charger for the domestic battery overcharging it via the VSR
You can disable a VSR by fitting a switch in its negative connection and switching if off, in this case when the batterycharger is in use but it's another thing to remember to do and to switch on again so that the alternator charges both batteries.. Best therefore regarded as an emergency feature only.

It might be possible to find a single sensing VSR that can be be connected to sense the starter battery only but all the modern electronically controlled VSRs seem to be dual sensing.

Maybe too complicated, but you could have a normally closed heavy duty relay to disconnect the VSR when the battery charger is on. Usually these relays are 12 or 24Vdc so would have to be powered by a small 230V to 12Vdc power supply which is switched on with the charger.

 

[Tranona]

I am assuming the alternator is connected to one bank( usually the starter)---So if they are not connected , how does the alternator charge both battery banks when motoring?

I have just double checked and if the split charger is dual sensing as the VSR I am using is, then it will sense the charge from the mains charger connected to the house bank and direct it to the start as well. However, the charge profile of the 2 banks is the same so the start battery will not be "cooked" any more than it would if the charge was coming from the alternator. If you did have 2 different types of batteries then the recommendation is to set the mains charger at the profile to suit the lowest.

BTW this is not a battery to battery charger which is a completely different thing where you don't use a splitter but fit a B2B to charge the house bank from the starter bank as explained here 12voltplanet.co.uk/auxiliary-battery-charging-in-vehicles-with-smart-alternators.html I am using one of these to charge the bow battery as it means I only have to run small cables forward rather than using a 3 way splitter to charge it direct from the alternator.

 

[Daydream believer]

I have just double checked and if the split charger is dual sensing as the VSR I am using is, then it will sense the charge from the mains charger connected to the house bank and direct it to the start as well. However, the charge profile of the 2 banks is the same so the start battery will not be "cooked" any more than it would if the charge was coming from the alternator. If you did have 2 different types of batteries then the recommendation is to set the mains charger at the profile to suit the lowest.

I may be thick here ( forget alternator charging for now, stick to shore power charger) & i am trying to get my head round this. The batteries could be identical but the charge profile will not necessarily be in the same part of the cycle. The domestics may be nearly flat (say) & the starter full . That means that the already full starter will be getting, say 14.4 volts when it only needs a float of, say, 13.2. The domestics will be requiring 14.4 volts so the charger will be shovelling in a charge from the "Bulk" phase but not the lower "float" phase required by the starter a. Over time it will cook the starter- which is what I think has happened to me

As for a VSR, it is set to go one way. ie if the level in the domestics fall below a level ( possibly 12.6V) it shuts off the starter to avoid the starter being drained. It does not work the other way round. It does not say "Oh the starter has 13 V in it so I will shut of power to it" Which would solve the problem

 

[VicS]

>
As for a VSR, it is set to go one way. ie if the level in the domestics fall below a level ( possibly 12.6V) it shuts off the starter to avoid the starter being drained. It does not work the other way round. It does not say "Oh the starter has 13 V in it so I will shut of power to it" Which would solve the problem

You misunderstand how a VSR works

A single sensing VSR sensing the starter battery /alternator will close when it senses the starter battery has reached its closing voltage (13 8 ??) which will be almost straight away. Both batteries will then charge together in parallel.
A single sense VSR will not do the same when the domestic battery, being charged by a battery charger, reaches the closing voltage. The charger will only charge the domestic battery.

BUT

I think you will find that most, if not all, the modern eiectronically controlled VSRs, like the Victron Cyrix, are dual sensing. They will close, paralleling the batteries, when the alternator gets the starter battery up to the closing voltage or when the battery charger gets the domestic battery up to the closing voltage. The later is what you are keen to avoid.

I still think your best option if you want to avoid the possibility of overcharging the starter battery is an Argofet.It will charge both from the alternator but will only allow a single output battery charger to charge the domestic battery.

 

[Daydream believer]

I still think your best option if you want to avoid the possibility of overcharging the starter battery is an Argofet.It will charge both from the alternator but will only allow a single output battery charger to charge the domestic battery.

I have had a brief look, but the wiring is extremely complicated & I sort of got the impression that it is designed for systems that are much more detailed than my simple 2 bank 3 battery system.
I will look again tomorrow( V tired today have been laying race marks since 06-00 & I am knackered)

 

[IanCC]

I have 2 ctek battery chargers. One for domestic, one for starter. Not big, not dear on ebay. Simple wiring.