VSR or Split Charge Diode?

[halcyon]

Perhaps the most technically correct solution is a B2B charger to float charge the engine battery.
This avoids overcharging the engine battery, which has much less drain on it than the house battery.
An emergency starting link covers the possibility of the engine battery failing. But kept isolated and properly float charged, it's likely to last over ten years.

You cannot overcharge an engine battery with a VSR, the over charging was based on standard diode, blocking diode systems using alternator sensing on service battery. The idea was on high loads the diodes would drop around 1.2 volts, swo the alternator regulates at 15.6 volt to maintain 14.4 volt at service battery terminal. Now the engine battery is little discharged so quickly reaches recharge and current falls, so does volt drop across the diode to around 0.7 volt. So 15.6 charge voltage minus 0.7 volt drop in engine diode equals 14 9 volt charge voltage to engine battery.

Well that was the marketing theory behind it, but a good VSR will only drop 0.04 volt per 100 amp, so at 1 amp very low.

rian

 

[lw395]

You cannot overcharge an engine battery with a VSR, the over charging was based on standard diode, blocking diode systems using alternator sensing on service battery. The idea was on high loads the diodes would drop around 1.2 volts, swo the alternator regulates at 15.6 volt to maintain 14.4 volt at service battery terminal. Now the engine battery is little discharged so quickly reaches recharge and current falls, so does volt drop across the diode to around 0.7 volt. So 15.6 charge voltage minus 0.7 volt drop in engine diode equals 14 9 volt charge voltage to engine battery.

Well that was the marketing theory behind it, but a good VSR will only drop 0.04 volt per 100 amp, so at 1 amp very low.

rian

So when the engine battery is fully charged and the manufacturer says to float it at 13.7V, you're giving it 14.4V.

 

[halcyon]

So when the engine battery is fully charged and the manufacturer says to float it at 13.7V, you're giving it 14.4V.

As said before, how many hours would you drive your car with an alternator regulator that was set at 14.4, some 14.8 volt, the float voltage was for back- up power supply battery banks on permanent charge.

Brian

 

[lw395]

As said before, how many hours would you drive your car with an alternator regulator that was set at 14.4, some 14.8 volt, the float voltage was for back- up power supply battery banks on permanent charge.

Brian

I drive my car on average an hour a day.
Our solar panel works on average 8 hours a day.

On an hour a day of overcharging, a typical car battery dies after maybe 8 years.
On 8 hours a day of overcharging don't be surprised if you kill it much sooner.

 

[pvb]

On an hour a day of overcharging, a typical car battery dies after maybe 8 years.

How do you explain the battery life of taxis then? Many are run virtually around the clock (with different drivers) and their batteries last well.

 

[halcyon]

I drive my car on average an hour a day.
Our solar panel works on average 8 hours a day.

On an hour a day of overcharging, a typical car battery dies after maybe 8 years.
On 8 hours a day of overcharging don't be surprised if you kill it much sooner.

But once the batteries are at 14.4 volt charge current will fall to almost zero, so you may boil of a little water, but you want over charge the battery. Now if you motor 12 hours a day 7 days a week 52 weeks a year or have surplus cash I see no reason why you should not fit one. But for normal boaters who motor out of the mooring hoist sail, turn off the engine and go, no point in fitting one. Okay I have a wind gen, so I fitted a voltage regulator, same as solar panels fit a regulator.

Brian

 

[rszemeti]

Most of the time we run the engine to get out of the harbour and hoist the sails. I'm guessing that there is no value in advanced functions for this case where the engine is on for around 30 minutes max. However, last year we did motor round the MoK - no wind - which was around 16 hours. We had instruments/autopilot/nav lights/USB phones chargers etc on while we did that. Would an advanced alternator regulator pay for these longer runs?

Depending on the actual regulator, at least some will try to push the alternator to its maximum safe limit, to get the maximum benefit in the shortest possible time. If you dislike the running engine but need to charge your batteries, it can pay dividends.

On a long run, of many hours, I doubt it makes much (any?) difference .. cars seem to manage just fine, but just remember, cars are generally not going into deep discharge over several days holed up in an anchorage waiting out weather.


I was suprised that my "standard" alternators, even on a flattish bank of batteries didn't exceed 30A output, each. With a pair of 80A alternators, I was hoping to get a bit more than that into the batteries. The new regulators are only just fitted, I'll report back if there is an improvement.

 

[pvb]

I was suprised that my "standard" alternators, even on a flattish bank of batteries didn't exceed 30A output, each. With a pair of 80A alternators, I was hoping to get a bit more than that into the batteries. The new regulators are only just fitted, I'll report back if there is an improvement.

It's obviously dependent on the output curve of the alternators, but at typical cruising revs you may be some way short of their theoretical max output. But a 60A charge isn't bad, and may be all that your battery bank can accept. On my old boat I had 660Ah of domestic batteries and a 90A alternator with an Adverc booster, and rarely saw much more than 50 or 60A charge current.

 

[ghostlymoron]

I don't understand why, but it seems you never gain much by fitting a bigger alternator.

 

[GHA]

Depending on the actual regulator, at least some will try to push the alternator to its maximum safe limit, to get the maximum benefit in the shortest possible time. If you dislike the running engine but need to charge your batteries, it can pay dividends.

How? If you have an alternator already set to about 14.4v going up To 14.8v will make a bit of a difference but not a huge amount. The batteries don't care what expensive regulator you have, they'll take what they want and no more mostly dependent on voltage. After around 80% soc it's still going to be about at least 4 hours to get to full. No way round that.

 

[pvb]

I don't understand why, but it seems you never gain much by fitting a bigger alternator.

It's because the charge current is governed by how much the batteries can accept, not by how much the alternator can produce.

I've often suggested that the most cost-effective charging improvement is to add more batteries to the bank.

 

[GHA]

I don't understand why, but it seems you never gain much by fitting a bigger alternator.

This might be of interest..

https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/

 

[halcyon]

How? If you have an alternator already set to about 14.4v going up To 14.8v will make a bit of a difference but not a huge amount. The batteries don't care what expensive regulator you have, they'll take what they want and no more mostly dependent on voltage. After around 80% soc it's still going to be about at least 4 hours to get to full. No way round that.

Talking lead acid flooded batteries, a fully charged battery needs around 15 4 volt, but from 14.6 volt the curve gets steeper and the gain less, so above 14.6 you don't gain a lot, but water loss is high due to excessive gassing. Once you reach a fixed voltage the charge current tails of to nothing, due to lack of voltage, though the actual charge voltage is higher than your meter reads due to the sign wave output from the alternator, so you get a better charge close to 100%.

Brian

 

[lw395]

Most of the time we run the engine to get out of the harbour and hoist the sails. I'm guessing that there is no value in advanced functions for this case where the engine is on for around 30 minutes max. However, last year we did motor round the MoK - no wind - which was around 16 hours. We had instruments/autopilot/nav lights/USB phones chargers etc on while we did that. Would an advanced alternator regulator pay for these longer runs?

How are you keeping your house batteries charged?

 

[adwuk]

How are you keeping your house batteries charged?

I think the same way as a lot of people - mains charger when on hook up, 90w solar panel via its own controller, and linked to the starter battery circuit when the engine is running (but using an emergency join switch - hence the original question).

 

[lw395]

I think the same way as a lot of people - mains charger when on hook up, 90w solar panel via its own controller, and linked to the starter battery circuit when the engine is running (but using an emergency join switch - hence the original question).

Lots of people do lots of different things with their boats and batteries.
If you've got 90W of solar, that makes a significant difference.
If you plug in to the shore every mon-fri, that's a big difference to us swinging mooring cheapskates who only plug in a few times a year.
HTH?

 

[rszemeti]

It's because the charge current is governed by how much the batteries can accept, not by how much the alternator can produce.

With a simple constant-voltage alternator, yes, you are correct.

With a "clever" alternator, once into the "bulk acceptance" phase, it is permissible to increase the voltage and push a lot more current out of the alternator, which the batteries will happily soak up. The trick is of course to reduce the voltage to a "topping off" level and then to a normal "float" level before you cook them.

 

[GHA]

With a simple constant-voltage alternator, yes, you are correct.

With a "clever" alternator, once into the "bulk acceptance" phase, it is permissible to increase the voltage and push a lot more current out of the alternator, which the batteries will happily soak up. The trick is of course to reduce the voltage to a "topping off" level and then to a normal "float" level before you cook them.

That doesn't make any sense. What do you mean by "bulk acceptance phase"? Do you mean increasing the voltage during the constant voltage acceptance phase to above manufacturers recommendations (and possibly blowing some equipment onboard)? Bulk isn't constant voltage.
If so can you name a charger or regulator which does this?

Sounds barmy and dodgy

 

[pvb]

With a simple constant-voltage alternator, yes, you are correct.

With a "clever" alternator, once into the "bulk acceptance" phase, it is permissible to increase the voltage and push a lot more current out of the alternator, which the batteries will happily soak up. The trick is of course to reduce the voltage to a "topping off" level and then to a normal "float" level before you cook them.

For the avoidance of doubt, perhaps I should have written "...the charge current is governed by how much the batteries can accept at a given charging voltage...". Batteries will only "happily soak up" a certain amount of charge current, regardless of the alternator's ability to output more.

 

[halcyon]

With a simple constant-voltage alternator, yes, you are correct.

With a "clever" alternator, once into the "bulk acceptance" phase, it is permissible to increase the voltage and push a lot more current out of the alternator, which the batteries will happily soak up. The trick is of course to reduce the voltage to a "topping off" level and then to a normal "float" level before you cook them.

To put it simply, a alternator produces watts, as you increase output volts you reduce output current the old specs gave amperage at 14.00 volt. What you are doing is overcharging the battery, so it may appear fully charged, but the faster you charge the lower the available capacity. You get excessive gassing, plus the voltage you read is not the peak voltage, alternator output is a sign wave for each phase, not a straight line

Brian.