Domestic- starter charging query

[Daydream believer]

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

Are your 2 batteries linked for alternator charging?

 

[VicS]

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)

Your impressions are wrong.
You will only need a 2 output one and presumably the only 100 amp version. (Argofet 100-2l

Unless you have some modern alternator which requires a 12 volt supply to its output terminal you won't need the connection to the "energise" terminal.
That leaves alternator output to the input terminal, domestic battery to 1 output, starter battery to the other and a ground connection to the common battery negative

 

[VicS]

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

How does your alternator manage to charge both?
Diode splitter,
VSR,
Manual switching,
Sterling A2B,
Something else.

 

[IanCC]

Are your 2 batteries linked for alternator charging?

There was a diode thing, that worked, then a vsr, that worked too and now an a2b.

 

[BabaYaga]

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

I have had a small Red Flash as a starter battery for almost 15 years (since a couple of years on my second one) and have had similar worries about over charging it, mainly in connection with shore power charging of the domestic bank, but also from solar charging.
I agree with what is already stated upthread about the Red Flash. Unless you have a usage pattern of frequent engine starts and extremely short engine runs, it will cope very well on alternator charging alone. Therefore, automatic paralleling of batteries (VSRs, multiple output chargers) is not really necessary from the starter battery's point of view. It is not even desirable, for the reason you outline above, the risk of over charging.
However, charging the domestic bank from the alternator is highly desirable and the reason for the development of various methods of paralleling/charge splitting (1-2-both switches, diodes, VSRs, low loss splitters /argofet etc).
One way to solve the problem would be, as already mentioned, a single sensing VSR between starter battery and domestic bank. Paralleling would then only occur when running the engine. But those single sensing VSRs which are still available may lack some of the sophistication necessary to avoid relay chatter etc.
A low loss splitter is another option, more expensive though.
My own solution through these 15 years has been to use a non-voltage sensitive relay, activated by alternator D+, between the battery banks. This means that the starter and domestic batteries are paralleled only when the alternator starts putting out charge and they are disconnected again at engine shut down.
Shore power charge and solar charge go to the domestic bank only.
I have also connected the alternator output primarily to the domestic bank, contrary to convention, The Red Flash is put on line through the relay. This means lower charging currents through the relay and it also provides a possibility to disconnect the starter battery while running the engine (which I do sometimes on long engine runs, several hours) to minimize the risk of over charging.

 

[Daydream believer]

My own solution through these 15 years has been to use a non-voltage sensitive relay, activated by alternator D+, between the battery banks. This means that the starter and domestic batteries are paralleled only when the alternator starts putting out charge and they are disconnected again at engine shut down.
Shore power charge and solar charge go to the domestic bank only.
I have also connected the alternator output primarily to the domestic bank, contrary to convention, The Red Flash is put on line through the relay. This means lower charging currents through the relay and it also provides a possibility to disconnect the starter battery while running the engine (which I do sometimes on long engine runs, several hours) to minimize the risk of over charging.

That sounds like the solution I need. My engine starts immediately (after nearly 5000 hours) so hardly takes any current from the starter.
I now need to know what relay to buy & how to wire it in to the circuit
Or is that what VicS is also telling me?
I need to get some diagrams drawn & compare when I come back off the water today. At the minute I am confused

 

[PaulRainbow]

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

Leave it alone, your setup is the same as millions of other boats, that all work perfectly well.

 

[Daydream believer]

Leave it alone, your setup is the same as millions of other boats, that all work perfectly well.

Ok. i would like to do that, but the question remains-why have I knackered my last Red flash after 14 months when I have NEVER run it low.? ( 2 months out of warranty)

 

[PaulRainbow]

Ok. i would like to do that, but the question remains-why have I knackered my last Red flash after 14 months when I have NEVER run it low.? ( 2 months out of warranty)

I cannot answer that question, but it's a standard way of connecting batteries for split charging. My own boat has a VSR and solar charging, so my engine battery has been on charge everyday for the last six years, as an example.

 

[IanCC]

Ok. i would like to do that, but the question remains-why have I knackered my last Red flash after 14 months when I have NEVER run it low.? ( 2 months out of warranty)

I don't know if this helps. It is very difficult (impossible) to get a datasheet out of DMS fir a redflash battery.
They gave me these figures over the phone for my redflash 1000.

Bulk. 14.5-14.7v Max
Float. 13.5-13.8v.

But he seemed to be basing his opinion on Lifeline and Enesis? data. I aould be very tempted by the Full Throttle batteries next time. Same specs more info.

 

[Tranona]

Plenty of information here odysseybatteries.com/odyssey/docs/us-ody-tm.pdf on Odyssey batteries. The PC 950 is their equivalent of the Red Flash 1000 and has an absorption of 14.7 and a float of 13.8, which is the same as the Exides I have for my house bank.

 

[Boater Sam]

Faced with the same problem, overcharging the engine starter battery, I wired a big diode into the charging lead just to the starter battery which knocks of 0.7v with respect to the cabin batteries.

 

[Daydream believer]

I don't know if this helps. It is very difficult (impossible) to get a datasheet out of DMS fir a redflash battery.
They gave me these figures over the phone for my redflash 1000.

Bulk. 14.5-14.7v Max
Float. 13.5-13.8v.

But he seemed to be basing his opinion on Lifeline and Enesis? data. I aould be very tempted by the Full Throttle batteries next time. Same specs more info.

You are correct I could not find published data so had to ring the supplier & was given the same info. But the fact remains that once full one does not still go on trying to put a bulk charge into a battery that only needs a float

 

[Daydream believer]

I cannot answer that question, but it's a standard way of connecting batteries for split charging. My own boat has a VSR and solar charging, so my engine battery has been on charge everyday for the last six years, as an example.

It is OK if it has been on a float or storage charge, but if another battery in the system has been calling for a bulk charge & your starter battery had been getting a BULK charge for 6 years i think that you would agree that it would be well cooked.
Your VSR does not stop power coming from the domestics to the starter. It only stops it going the other way. As soon as the domestics go on charge the voltage registers over 14 V so the VSR clicks on & joins the 2 banks & stays that way until the domestics go to float then the whole lot goes to float. If, however, one is using some power from the domestics whilst in dock ( lights, fridge etc) the domestics probably stay on bulk to compensate & that means the starter gets that bulk as well.
So if I go on holiday for 20 weeks, my starter gets overcharged every day when I am in dock.

 

[BabaYaga]

That sounds like the solution I need. My engine starts immediately (after nearly 5000 hours) so hardly takes any current from the starter.
I now need to know what relay to buy & how to wire it in to the circuit
Or is that what VicS is also telling me?
I need to get some diagrams drawn & compare when I come back off the water today. At the minute I am confused

In case you are interested in my set up, this is the basic idea:

 

[Daydream believer]

Thanks for that. assuming I was going to buy them-What exactly is the "Comb relay" & the "250amp"( is it a fuse because you mentioned a relay) please? What would I actually be asking the supplier for?
I assume that my shore power would sit where the solar charger sits.

 

[BabaYaga]

Thanks for that. assuming I was going to buy them-What exactly is the "Comb relay" & the "250amp"( is it a fuse because you mentioned a relay) please? What would I actually be asking the supplier for?
I assume that my shore power would sit where the solar charger sits.

The battery combining relay might be something like this:
Volvo Relay 838518 12volt 75 amp relay
250 amp fuse at the house bank because the wiring through the switches should be sufficient for engine starting.
Yes, shore power charger connects to the fuse box upper left.

Edit: This simple diagram is not extensive concerning the fusing.

 

[PaulRainbow]

You are correct I could not find published data so had to ring the supplier & was given the same info. But the fact remains that once full one does not still go on trying to put a bulk charge into a battery that only needs a float

You cannot "put a charge" into a battery, if it's charged it will not take any more current. You can't force feed it, it's a buffet. it helps itself to what it needs.

 

[PaulRainbow]

It is OK if it has been on a float or storage charge, but if another battery in the system has been calling for a bulk charge & your starter battery had been getting a BULK charge for 6 years i think that you would agree that it would be well cooked.
Your VSR does not stop power coming from the domestics to the starter. It only stops it going the other way. As soon as the domestics go on charge the voltage registers over 14 V so the VSR clicks on & joins the 2 banks & stays that way until the domestics go to float then the whole lot goes to float. If, however, one is using some power from the domestics whilst in dock ( lights, fridge etc) the domestics probably stay on bulk to compensate & that means the starter gets that bulk as well.
So if I go on holiday for 20 weeks, my starter gets overcharged every day when I am in dock.

I have lived aboard for the past 6 years, my domestic bank gets fully charged every day. My VSR and indeed your, as it's a Cyrix, the same as mine, doesn't stop any charge going anywhere. It's a micro-processor controlled, dual sensing voltage sensing relay, it closes when a set of parameters are met and opens when another set of parameters are met.

The bog standard relay that has been suggested isn't a great idea, because it's permanently closed when the engine is running, regardless of the state of the batteries, it doesn't have the safety feature of the VSR, in that it will not open if battery voltages drop.

If you don't like the way the VSR works (even though it works fine for millions of people) you could, amongst other things, fit the bog standard relay in addition to the VSR. Fit it so the relay is energised by the engine "ignition" and makes/breaks the VSR negative connection. This way, the relay operates as normal, but only when the engine is running.

 

[Daydream believer]

The battery combining relay might be something like this:
Volvo Relay 838518 12volt 75 amp relay
250 amp fuse at the house bank because the wiring through the switches should be sufficient for engine starting.
Yes, shore power charger connects to the fuse box upper left.

Edit: This simple diagram is not extensive concerning the fusing.

Thanks