Automatic Charge Relays - Good or Bad

[sabray]

Originally Posted by Maine Sail

If it is working, it is working.

The problem is in relay cycling. The start batt voltage comes up nearly instantaneously because of SOC. The relay CLOSES/MAKES and combines with the depleted house bank. The alt can not maintain the combine voltage set point of the combiner so the relay drops out/opens. Repeat, repeat, repeat. If this is not happening you are fine. I still prefer not to run the entire alt output through the contacts in the relay. Voltage sensing for alternator I also prefer to wire that to house too.

It is much easier for the alt to bring the house bank to combine voltage and then have it combine with the start battery, than to have the start battery combine with house and have relay cycling. If the banks are close to the same size, no big deal most combiners are dual sensing these days and relay cycling would only be a problem with small current sources like solar or wind...

Thanks .yes dual sensing. Guess if I upped the alternator it might be better if it was 2" closer to the house bus. Imagine a house bus and engine bus bar. In the middle is a combiner. I see no difference if the charge point is on house side or engine side. I am feeling better that I didn't screw this up.



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[Andina Marie]

Originally Posted by Maine Sail

If it is working, it is working.

The problem is in relay cycling. The start batt voltage comes up nearly instantaneously because of SOC. The relay CLOSES/MAKES and combines with the depleted house bank. The alt can not maintain the combine voltage set point of the combiner so the relay drops out/opens. Repeat, repeat, repeat. If this is not happening you are fine. I still prefer not to run the entire alt output through the contacts in the relay. Voltage sensing for alternator I also prefer to wire that to house too.

It is much easier for the alt to bring the house bank to combine voltage and then have it combine with the start battery, than to have the start battery combine with house and have relay cycling. If the banks are close to the same size, no big deal most combiners are dual sensing these days and relay cycling would only be a problem with small current sources like solar or wind...

I don't see why you think cycling would be a problem? Our Combiners are designed to do that. An OEM alternator typically found on marine engines was never intended to be charging massive battery banks. Forcing it to charge a large bank with low voltage by direct connection risks overloading and overheating the alternator. By cycling on and off our Combiners regulate the load on the alternator to a safe level and keep the alternator working at a voltage and temperature where it has good efficiency.

When our Combiners first came out in 1993 we recommended connecting the alternator to the house bank because we had no long history on contact life. However in 20+ years making Combiners, all with unlimited warranty, we have never had a warranty replacement due to contact failure. From about 1995 on we advised leaving the alternator on the starting battery so the Combiner could regulate the load.

[sabray]

I haven't seen that either but mainsail is far more experienced then me. What is the rating on the contacts?


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[geoleo]

Iwill throw this into the mix!I recently bought a 31 yo Brewer 12.8 sloop. It has a large house bank of 8 T125s and (get this) a pair of Grp 24 12Volt "starting batteries - catr batteries "liknked" by a West Marine "Combiner". There is a switch off-on combiner on the Elect panel. Boat also has 500 watts solar and a Air windmill. What me worry????

[Maine Sail]

Originally Posted by Andina Marie

I don't see why you think cycling would be a problem? Our Combiners are designed to do that. An OEM alternator typically found on marine engines was never intended to be charging massive battery banks. Forcing it to charge a large bank with low voltage by direct connection risks overloading and overheating the alternator. By cycling on and off our Combiners regulate the load on the alternator to a safe level and keep the alternator working at a voltage and temperature where it has good efficiency.

When our Combiners first came out in 1993 we recommended connecting the alternator to the house bank because we had no long history on contact life. However in 20+ years making Combiners, all with unlimited warranty, we have never had a warranty replacement due to contact failure. From about 1995 on we advised leaving the alternator on the starting battery so the Combiner could regulate the load.

The alternator should be properly sized and set up for the bank it is intended to charge.. Running it through a combiner to "regulate" the load and compensate for a crappy alternator is a Band-Aid.

I have fixed numerous installations/banks that have suffered from relay cycling, including systems using Yandina combiners of which I have installed a lot of.. Eventually the relay stays made but this can slow charging to the house bank, especially in the short engine run times sailors do. The start battery does not need to be charged first as it is already at 99% SOC and the relay tries to make as soon as the XX voltage / time delay has occurred.

This situation is made much worse when I see an owner install solar or wind then lead it to the start battery first and I have seen and fixed this one far to many times to count. Owners are very surprised when their house bank actually starts charging well off solar....

The relay cycling won't harm the combiner but can slow charging. If your alt is not up to the task fix that first....

[sabray]

So we don't want the high out put alternator putting big Amos across the relay. That's why it's okay for me. Until input a bigger alternator in. The sense wire gets combined when the batts do not sure that's a issue. But it's probably better if the house batts got first phase voltage charge longer. They might not once the combiner checks in. Keeping it simple but I think I get the issue. Or mot


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[smac999]

Originally Posted by Maine Sail

The start battery does not need to be charged first as it is already at 99% SOC and the relay tries to make as soon as the XX voltage / time delay has occurred.

which with a 800ah+ battery bank at 50 soc and a small 60-80a could be 4+ hours before the combiner turns on. there is no way I'd want an engine running without the engine battery being charged. not for more then a min. that is just asking for problems. and a dead and stalled engine at some point. some engines take 10+ amps while running.

[Maine Sail]

Originally Posted by smac999

which with a 800ah+ battery bank at 50 soc and a small 60-80a could be 4+ hours before the combiner turns on. there is no way I'd want an engine running without the engine battery being charged. not for more then a min. that is just asking for problems. and a dead and stalled engine at some point. some engines take 10+ amps while running.

A 60A alt on an 800Ah bank..... Why would any "competent" installer do such a thing...?

That is 4.6 hours just to get to 85% SOC from 50% SOC. Of course that does not include charge efficiency or the alt actually getting hot and putting out 40A, rather than 60A, which would now result in about 8.4 hours to go from 50% SOC to 85% SOC. An 800Ah bank on a 60A alt or main "fast charge" source is simply poor system design not an issue of the ACR or combiner.

7.5% of "C" is about as useless as tits on a bull unless it is solar and you have DAYS to wait for a full charge.....

If it takes you four hours to raise the voltage to 13.0V on an 800Ah bank you simply need to go back to the drawing board on the system design.

Even so I would bet that a diminutive 7.5% of "C" charge source could still hit combine in under 40 minutes, but it is still a horrible system design....

A healthy bank charged with 20% of "C" source will raise the voltage to combine levels (13.0V) in about 12-15 minutes. Done this test many times, with many different lead acid batteries and scaled it both up and down...

It is getting beyond the combine voltage that becomes harder, but 13.0V is pretty easy for a well designed system to hit......

If you have an 800Ah bank and don't have 20% of "C" from your alternator or charging system it may take longer to combine.... If you can't provide 20% of "C" then that is simply a poor design unless you have lots of time to charge, which on sailboats is rarely the case.....

An Echo Charger or Duo Charger also don't turn on until 13.0V so there is no difference in that regard. The Sterling battery to battery charger, their version of an Echo or Duo, does not turn on until 13.3V...

This is some collected data from a test I ran a few years ago. The battery was a healthy, but broken in, 125Ah Group 31 "Deep Cycle" battery fed by a 20% of "C" charge rate, or 25A, this after being discharged to 50% SOC. This was also after a controlled 20 hour capacity test confirming the capacity of the bank.

It took 1.7 Hours in bulk or constant current charging to hit absorption voltage but just 10 minutes at 20% of "C" to hit combine voltage. This was done at 75F....

2 Min = 12.59V / 25A = BULK / Constant Current
10 Min = 13.0V / 25A (ACR would make after 90 seconds)
20 Min = 13.12V / 25A
30 Min = 13.22V / 25A
40 Min = 13.33V / 25A
50 Min = 13.45 / 25A
60 Min = 13.6V / 25A
70 Min = 13.76 / 25A
80 Min = 13.95 / 25A
90 Min = 14.16V / 25A
100 Min = 14.39 / 25A
102 Min = 14.4V / 24.5A = ABSORPTION VOLTAGE / Attained Voltage Limiting

[DeepFrz]

Maine Sail, you are such a patient man.

[Vivid]

Strong vote against Echo Charger. They are very delicate--will fail if disconnected from start battery while on! per the owner's manual and my own experience. How hard would it have been to protect against an obvious case like that? Also, the 15 amp limit is meager and even when it worked my start battery was often at a lower than optimum SOG.

Xantrex response to my repair inquiry is that if out of warranty there is no repair option. I found a Yandina combiner at Defender for $55 and I strongly agree that combining will not "cook" the start battery whether with ACR or directly with the "Both" switch

Why not just use the "Both" switch? Eventually someone will leave the boat with a light or two on and the switch on "Both" and you will come back to two dead banks. Nice at least to be able to start the engine with a dead house bank.


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