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Battery Charging

Ammonite

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As a result of my other recent thread "Alternator Voltage / Replacement" I'm having a bit of a rethink when it comes to battery charging.
I currently have 2x 110amp SLA (House), 1 x 110amp SLA (Starter) and 1 x 120amp AGM (Thruster). All are 12v.
Alternator charging: I currently have a 60amp Alternator that appears to have been internally modified to output 14.8v with Battery sensing via a 1-2-Both switch meaning that when set to 2 only the house bank is sensed and if set to 1 only the starter bank is sensed. The alternator appears to be working but there is considerable heat damage / melting around the negative side of the rectifier plate. The output from the alternator goes directly to a 3 way low loss splitter (max 0.25v loss according to the manual) to each bank.

Engine off (no shore power): The starter and house bank are both charged via a wind generator which in practice I very really use. The house bank is also charged via an 80w solar panel and Victron smart controller. This works really well. The thruster battery is charged via a Cyrix VSR from the house bank which connects at 12.8v and disconnects at 13.8v.

Mains charger: I have a 20amp three output Sterling smart charge to charge each bank. This is set to the SLA profile. 14.4v max, 13.5v float.

Current issues:
Overcharging of the unsensed battery banks under engine. When the 1-2-Both is set to 2 it results in a steady 14.7/8v at the house bank but up to 15.2v at the others.
Undercharging of the thruster battery due to the mains charger having an SLA profile and the Cyrix VSR limiting the voltage to 13.8v.
Risk of Alternator damage in the event there is problem with battery sensing due to a duff battery etc

Solution: I am going to replace the heat damaged alternator with a Prestolite 70amp with a nominal output of 14.4v. If I keep the existing sensing arrangements this will result in 14.4v at the sensed battery and, based on what I'm seeing currently circa 14.8v at the others, which is ideal for the AGM but a bit high for an SLA, although it's reliant on what's happening with the sensed bank. This is all based on the sensing wire upping the voltage to account for the any load and losses through the splitter.

Add a Battery to battery charger for the Thruster to ensure that it has the correct AGM charging regime. This would then allow me to disconnect the Thruster battery from the alternator splitter and eliminate the overcharge risk. It would still use the mains charger SLA profile which is set to 14.4v with a 13.5v float. The mains charger is only used when in marinas and not on my regular mooring. Edit: on second thoughts this last bit won't be needed and I'll only need to charge the starter and house via the mains charger!

Switch the Cyrix so that it charges the starter battery from the house bank and remove the feed to the starter battery from the battery splitter. This would limit the charge to 13.8v under engine but it would still periodically charge the starter battery to 14.4v when using the mains charger. It would also remove the risk of over charging the starter battery due to the current sensing arrangements.

Remove the sense wire from the 1-2-Both switch and reinstate back onto the B+ terminal on the alternator. Remove the battery splitter which is now redundant. Connect the battery splitter input (from the AlternatorB+) back onto the starter motor solenoid where it would have originally been.

Apologies for the lengthy post but I'd appreciate your comments / other ideas. I have no plans to go down the li-on route due to a combination of cost and the current capacity being more than adequate for the type of sailing we do at the moment. Thanks
 
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PaulRainbow

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As a result of my other recent thread "Alternator Voltage / Replacement" I'm having a bit of a rethink when it comes to battery charging.
I currently have 2x 110amp SLA (House), 1 x 110amp SLA (Starter) and 1 x 120amp AGM (Thruster). All are 12v.
Alternator charging: I currently have a 60amp Alternator that appears to have been internally modified to output 14.8v with Battery sensing via a 1-2-Both switch meaning that when set to 2 only the house bank is sensed and if set to 1 only the starter bank is sensed. The alternator appears to be working but there is considerable heat damage / melting around the negative side of the rectifier plate. The output from the alternator goes directly to a 3 way low loss splitter (max 0.25v loss according to the manual) to each bank.
No matter what you do, you can only sense one battery from the alternator. The 1-2-B switch really should go in your case. Simple to fit three separate switches, you are already covering the split charging systems, so it makes sense to change the switch.

Engine off (no shore power): The starter and house bank are both charged via a wind generator which in practice I very really use. The house bank is also charged via an 80w solar panel and Victron smart controller. This works really well. The thruster battery is charged via a Cyrix VSR from the house bank which connects at 12.8v and disconnects at 13.8v.
You are mistaken about the Cyrix, it does not disconnect at 13.8V, if it did it would be worthless.

Mains charger: I have a 20amp three output Sterling smart charge to charge each bank. This is set to the SLA profile. 14.4v max, 13.5v float.
That's fine.

Current issues:
Overcharging of the unsensed battery banks under engine. When the 1-2-Both is set to 2 it results in a steady 14.7/8v at the house bank but up to 15.2v at the others.
That's because the alternator is faulty.

Undercharging of the thruster battery due to the mains charger having an SLA profile and the Cyrix VSR limiting the voltage to 13.8v.
As above, you are mistaken how the Cyrix works. Once closed, the Cyrix will stay closed until the voltage falls below the setpoint, taking into account the timings controlled by the microprocessor. The SLA profile is slightly low for your AGM battery, no more so than thousands of other boats with AGM/SLA combinations.

Risk of Alternator damage in the event there is problem with battery sensing due to a duff battery etc
Unlikely. If the sensed battery failed with a shorted cell the alternator would see it as a flat battery and try to charge it up, that isn't going to damage the alternator, but it will overcharge the other battery eventually.

Solution: I am going to replace the heat damaged alternator with a Prestolite 70amp with a nominal output of 14.4v. If I keep the existing sensing arrangements this will result in 14.4v at the sensed battery and, based on what I'm seeing currently circa 14.8v at the others, which is ideal for the AGM but a bit high for an SLA, although it's reliant on what's happening with the sensed bank. This is all based on the sensing wire upping the voltage to account for the any load and losses through the splitter.

Add a Battery to battery charger for the Thruster to ensure that it has the correct AGM charging regime. This would then allow me to disconnect the Thruster battery from the alternator splitter and eliminate the overcharge risk. It would still use the mains charger SLA profile which is set to 14.4v with a 13.5v float. The mains charger is only used when in marinas and not on my regular mooring.
Almost correct. Fit the B2B (good idea to fit this) between the domestic bank and the thruster battery, the thruster battery will then get charged irrespective of what is charging the domestic bank. Leave the solar on the domestic bank and it will also charge the thruster battery. Do not connect the mains charger to the thruster battery, just the domestics and the engine battery. Link the now spare terminal of the mains charger to the domestic terminal. You should not have any other charging sources connected to the thruster battery.

Switch the Cyrix so that it charges the starter battery from the house bank and remove the feed to the starter battery from the battery splitter. This would limit the charge to 13.8v under engine but it would still periodically charge the starter to 14.4v when using the mains charger. It would also remove the risk of over charging the starter battery due to the current sensing arrangements.
This will make the Argofet redundant. The Cyrix will simply parallel the engine and domestic bank whenever there is a charging source present at either battery. The solar will charge the engine battery, the alternator will charge the domestics (which in turn will charge the thruster battery).

Either:

1) Remove the Argofet and connect the Cyrix between the engine and starter batteries. All domestic and engine batteries will get charged from any charging source applied to either battery.

2) Remove the Cyrix and connect the alternator to the Argofet. Connect two Argofet outputs to the engine and domestic banks, leave the 3rd output spare. The alternator will charge the engine and domestic batteries via the Argofet, the mains charger will also charge both banks. No engine battery charging from the solar panel.

I would go for option 2, if you're happy that the solar doesn't charge the engine battery.

Remove the sense wire from the 1-2-Both switch and reinstate back onto the B+ terminal on the alternator. Remove the battery splitter which is now redundant. Connect the battery splitter input (from the AlternatorB+) back onto the starter motor solenoid where it would have originally been.
If you go for option 1 above you will need to connect the alternator B+ to the starter solenoid, if you go for option 2 leave it on the Argofet. In both cases bin the 1-2-B switch and connect the sensing wire (if fitted) to the domestic bank.
 
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Ammonite

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Hi Paul. Just one initial observation. I take it you are not concerned by the risk of over charging the unsensed battery (or there isn't much of a risk?) if the domestic bank is being charged at 14.4v with the new alternator. I realise my existing alternator is outputting too high a voltage but I'm seeing a 0.4v difference between starter and house banks when on 2 which I'd assumed would still be the case when charging the sensed house bank at 14.4v
 

PaulRainbow

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Hi Paul. Just one initial observation. I take it you are not concerned by the risk of over charging the unsensed battery (or there isn't much of a risk?) if the domestic bank is being charged at 14.4v with the new alternator. I realise my existing alternator is outputting too high a voltage but I'm seeing a 0.4v difference between starter and house banks when on 2 which I'd assumed would still be the case when charging the sensed house bank at 14.4v
If you connect the sense wire to the engine battery the domestics won't get properly charged. If you connect the wire to the domestics, the engine battery will sit at whatever the alternator is outputting for the domestics, so for some time that will indeed be 14.4V. If the battery is fully charged it won't accept much in the way of current, it's just have a raised voltage, this will be much less detrimental to the engine battery than undercharging the domestics. Besides, it isn't going to be at 14.4V forever, as the domestics charge the voltage will be lower.

There are 10s of thousands of boats with this setup. Many will be using a mains charger with multiple outlets, or a VSR connected between the banks with solar connected to one bank. In most cases there isn't a problem, large solar arrays on heavily cycled domestic banks being one exception when used with a VSR. In your case, if you use the Argofet i think you'll be fine.
 

Ammonite

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Thanks Paul. That all makes sense and as an interim measure, before installing a battery to battery charger, I'm guessing it would be a good idea to tweak the charging profile on the solar controller to something like 14.6v absorption and 13.4v float as a good compromise between SLA and AGM? I think these were the values you suggested in an earlier post?
 
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PaulRainbow

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Thanks Paul. That all makes sense and as an interim measure, before installing a battery to battery charger, I'm guessing it would be a good idea to tweak the charging profile on the solar controller to something like 14.6v absorption and 13.4v float as a good compromise between SLA and AGM? I think these were the values you suggested in an earlier post?
Those voltages will be OK for both battery types.
 

Ammonite

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This evening I fitted the new alternator and it is better but still not right. I'm now seeing 14.6v at the sensed battery (this is either 1,2 or Both depending on the switch position as the sense wire goes to the starter solenoid) and 14.9v at the unsensed battery. I was seeing 14.8v and 15.1/2v before.

The main problem appears to be that the sense wire is reading 0.25v less than the actual battery voltage so I'm planning to move this from the starter solenoid to the house output on the low loss battery splitter. Does this make sense and are there any precautions I need to take? I will also address the voltage drop through the battery switch when I get round to replacing this.

My other query relates to the low loss splitter because although it is only supposed to drop a maximum of 0.25v the alternator input to the splitter (from the Alternator B+) is now at 15.4v while all three outputs read 14.6v which doesn't seem right.

Thanks in advance
 
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What about doing away with the splitter and the 1,2 both switch and just have an isolator switch on the feed to the control panel. Install the B2B charger between the engine and the house batteries and a VSR between the house and the thruster battery.
This gives you 14.4 v at the engine battery and proper charging of the house and thruster batteries.
The wind gen and solar both feed the house battery bank and the thruster bank if voltage is high enough.
 

PaulRainbow

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This evening I fitted the new alternator and it is better but still not right. I'm now seeing 14.6v at the sensed battery (this is either 1,2 or Both depending on the switch position as the sense wire goes to the starter solenoid) and 14.9v at the unsensed battery. I was seeing 14.8v and 15.1/2v before.

The main problem appears to be that the sense wire is reading 0.25v less than the actual battery voltage so I'm planning to move this from the starter solenoid to the house output on the low loss battery splitter. Does this make sense and are there any precautions I need to take? I will also address the voltage drop through the battery switch when I get round to replacing this.

My other query relates to the low loss splitter because although it is only supposed to drop a maximum of 0.25v the alternator input to the splitter (from the Alternator B+) is now at 15.4v while all three outputs read 14.6v which doesn't seem right.

Thanks in advance
If you want to set the alternator up for battery sensing, you need to sense the batteries.

From post #3 "connect the sensing wire (if fitted) to the domestic bank."

If you sense the domestic bank the alternator voltage will be adjusted to suit the SOC of that bank, the engine battery should read the same voltage when the domestic bank is charged, but will read a little higher when the domestic bank is depleted (will vary according to SOC) because the lower the domestic SOC the lower the terminal voltage at the batteries.

You'd not mentioned cable sizes from the alternator to the Argofet and from the Argofet to the batteries, this can have an impact, as cable sizes can affect voltage drop between the alternator and the batteries.

It doesn't help that you keep fiddling with the 1-2-B switch, while the sense wire is connected to the starter solenoid. I don't want to get into a 1-2-B switch rant here, but with the setup that you are ascribing to, it's just not the correct switching arrangement. For the pedants reading this, other arrangement may differ, but not here.
 

PaulRainbow

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What about doing away with the splitter and the 1,2 both switch and just have an isolator switch on the feed to the control panel. Install the B2B charger between the engine and the house batteries and a VSR between the house and the thruster battery.
This gives you 14.4 v at the engine battery and proper charging of the house and thruster batteries.
The wind gen and solar both feed the house battery bank and the thruster bank if voltage is high enough.
This is incorrect, please read post #3
 

Ammonite

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What about doing away with the splitter and the 1,2 both switch and just have an isolator switch on the feed to the control panel. Install the B2B charger between the engine and the house batteries and a VSR between the house and the thruster battery.
This gives you 14.4 v at the engine battery and proper charging of the house and thruster batteries.
The wind gen and solar both feed the house battery bank and the thruster bank if voltage is high enough.
Thanks. I'm almost certainly going to go with one of the options outlined by Paul in #3
but I'm not going to have time to do any major changes for a few weeks and for now I want to sort the sensing arrangement and figure out if I have a problem with the splitter. If I do I be more inclined to do away with it!
 

Ammonite

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If you want to set the alternator up for battery sensing, you need to sense the batteries.

From post #3 "connect the sensing wire (if fitted) to the domestic bank."

If you sense the domestic bank the alternator voltage will be adjusted to suit the SOC of that bank, the engine battery should read the same voltage when the domestic bank is charged, but will read a little higher when the domestic bank is depleted (will vary according to SOC) because the lower the domestic SOC the lower the terminal voltage at the batteries.

You'd not mentioned cable sizes from the alternator to the Argofet and from the Argofet to the batteries, this can have an impact, as cable sizes can affect voltage drop between the alternator and the batteries.

It doesn't help that you keep fiddling with the 1-2-B switch, while the sense wire is connected to the starter solenoid. I don't want to get into a 1-2-B switch rant here, but with the setup that you are ascribing to, it's just not the correct switching arrangement. For the pedants reading this, other arrangement may differ, but not here.
Thanks Paul. I understand what you are saying about the current sensing arrangements via the 1-2-Both and just want to confirm that a can remove the sense wire from the starter solenoid and connect it to the house output on the splitter, and if I do, whether I need to fuse it in any way? The cables between the Alternator, splitter and batteries are all 16mm2 and there is no discernable voltage drop between the splitter and the batteries. There is however a 0.8v drop between the splitter input and the output. 15.4v in and 14.6v out at 1500rpm.
I'm hoping that by moving the sense wire I will eliminate the current 0.25v voltage drop across the 1-2-Both switch and achieve 14.4v at the house bank but that still leaves the voltage drop across the splitter which I wasn't expecting. It doesn't impact the house bank voltage because the sense wire accounts for this but I'm assuming the Alternator is working harder than it should?
 

halcyon

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Thanks Paul. I understand what you are saying about the current sensing arrangements via the 1-2-Both and just want to confirm that a can remove the sense wire from the starter solenoid and connect it to the house output on the splitter, and if I do, whether I need to fuse it in any way? The cables between the Alternator, splitter and batteries are all 16mm2 and there is no discernable voltage drop between the splitter and the batteries. There is however a 0.8v drop between the splitter input and the output. 15.4v in and 14.6v out at 1500rpm.
I'm hoping that by moving the sense wire I will eliminate the current 0.25v voltage drop across the 1-2-Both switch and achieve 14.4v at the house bank but that still leaves the voltage drop across the splitter which I wasn't expecting. It doesn't impact the house bank voltage because the sense wire accounts for this but I'm assuming the Alternator is working harder than it should?
Low loss splitters are useally rated for volt drop at float charge, i.e very low current, at high high current they have around 2 x the VSR's volt drop, as a generalization.

Why make it so complicated ? 3 isolator switches and 2 x VSR's and your done, 3 output mains charges all banks, dual output solar reg to service and bow batteries, then hang the wind gen on starter batt to keep up.

Brian
 

Ammonite

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Thanks. If the splitter is working as it should and a 0.8v drop between the input and output terminals when charging at 2-3 amps is to be expected that's fine. I just wanted to confirm that it was. All I need to do now is move my sense wire to eliminate the voltage drop caused by whoever wired it via 1-2-Both to the starter solenoid and I'm sorted and will have the 14.4v I want. My solar regulator is a brand new Victron smart charger and although single output works really well to charge both house and thruster batteries with a Cyrix VSR between the two banks, although a B2B charger would have been better but more expensive as it has an AGM setting and no voltage loss. The wind generator is a dual output version that already charges the house and starter banks but in practice I don't use it much and with this boat and my previous one I've never had any need to charge the starter battery using anything other than normal motoring given the type of marina hopping sailing we do. Also from what I've read most dual output solar controllers only provide a trickle charge on the second output which wouldn't really help given my setup. I also want to make the most of what I have got, apart from replacing the 1-2-Both and potential B2B purchase! ;-)
 

PaulRainbow

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Thanks. If the splitter is working as it should and a 0.8v drop between the input and output terminals when charging at 2-3 amps is to be expected that's fine.
If you get 0.8V drop across an Argofet at any current, there is something wrong.

If you want to use battery sensing for the alternator, the sensing wire should go to the battery, not the Argofet, as i've already said.

The information in post #16 is a little different to what you've said previously, so i'd suggest something slightly different than previously:

Connect the alternator to the Argofet. Connect the Argofet outputs to the engine, thruster and domestic banks. The alternator will charge all batteries, i wouldn't worry about the slightly lower than ideal voltage for the AGM battery.

Leave the mains charger connected to all three banks.

Leave the solar on the domestic bank.

Connect the Cyrix between the domestic and thruster batteries.

Connect the sense wire to the domestic batteries.

Change the 1-2-B switch.
 

Ammonite

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If you get 0.8V drop across an Argofet at any current, there is something wrong.

It's not an Argofet although you said you thought it was similar to one when we were discussing my Thruster charging arrangements a few months back. Its a 3 way "low lost splitter" sold up Osculati that claims to have a max 0.25v drop. Do you think it has a fault?

If you want to use battery sensing for the alternator, the sensing wire should go to the battery, not the Argofet, as i've already said.

I'm sure it's me being dumb but what's the difference between connecting the sense wire direct to the house battery (a circa 4m run) and joining the sense wire to the house output on the splitter given that there is a 16mm2 charging cable already running from the splitter output to the house bank and no discernable voltage drop. Adding a completely new cable back to the housebank is doable if needed. I'm not disagreeing just curious.

The information in post #16 is a little different to what you've said previously, so i'd suggest something slightly different than previously:

Apologies if that is the case. Nothing has changed apart from my understanding of what's going on (a little)

Connect the alternator to the Argofet. Connect the Argofet outputs to the engine, thruster and domestic banks. The alternator will charge all batteries, i wouldn't worry about the slightly lower than ideal voltage for the AGM battery.

This is how it is wired currently

Leave the mains charger connected to all three banks.

Leave the solar on the domestic bank.

Connect the Cyrix between the domestic and thruster batteries.

This is how its currently wired as you suggested a few months back

Connect the sense wire to the domestic batteries.

This is what I'm planning to do subject to my query about the routing above


Change the 1-2-B switch.

On the list for the off season

Thanks again!
 

PaulRainbow

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It's not an Argofet although you said you thought it was similar to one when we were discussing my Thruster charging arrangements a few months back. Its a 3 way "low lost splitter" sold up Osculati that claims to have a max 0.25v drop. Do you think it has a fault?
If it's dropping the 0.8V that you mentioned earlier, it's not very good. See how it all looks when you wire as above.

I'm sure it's me being dumb but what's the difference between connecting the sense wire direct to the house battery (a circa 4m run) and joining the sense wire to the house output on the splitter given that there is a 16mm2 charging cable already running from the splitter output to the house bank and no discernable voltage drop. Adding a completely new cable back to the housebank is doable if needed. I'm not disagreeing just curious.
If you want to sense a battery, that's where you connect the sense wire. The point of sensing the battery is that the charging source will correct for any voltage drop between itself and the battery. A 4m run of 16mm cable carrying a 50A current at 14V will drop 0.5V. Doesn't sound much, but your 14.4V is now only 13.9V, barely more than a float voltage.
 
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