Battery bank and monitor question

[walt]

I have a trailer boat with one battery only.. so dont follow these discussion closely..(ie, I could be wrong)..

But I thought the idea was that you have one main battery bank that you both directly charge and also use to start the motor.

There is an auxilary battery that you normally dont put a load on (even starting) since you always want to make sure its fully charged. Its your safety backup.. You can only use the aux battery by manually switching it in.

All the ACR or Echo chargers do is connect the aux battery to the main battery during charging - and charging only as that is the only time the main battery voltage gets above 13 volts..

ACR doesnt do anything for starting and actually would make sure the aux safety battery was disconnected from the main battery during starting.

... and the Echo manual shows the safety aux battery as a "starting battery" which would not agree with what I just said..

And... the "temorary islolation of starter noise and voltage drops to senstiive electroncs" would only seem to work if you used the aux battery to start the motor...

 

[Maine Sail]

Batteries them selves don’t limit current. Acceptance is a from a combination of the charger - battery working as a system. For example, a battery might be limiting acceptance current at 14.4 volts. But if the charger were changed to try and operate the battery at 20 volts, there might be a huge current into the battery - even though its voltage is at 14.4.

Yes of course the battery charger, solar controller, regulator etc. has to pulse the power supply in order to not over shoot the voltage limit but it is the battery which essentially dictates this behavior, once you attain the "limiting" voltage and hold it steady.

Yes if you raise the voltage more current will flow into the battery but if you hold it constant the accepted current declines as SOC increases. At 80% SOC it might be taking 14A at 14.4V but at 100% SOC it might only accept 0.1A in order to not over shoot the voltage limit.

In CC / constant current mode the chargers output limit is the limiting factor and in CV / constant voltage charging the battery is the limiting factor.

You could take a 1000A charger or a 15A echo charger both set to 14.4V but if the battery can only accept 2A at 98% SOC nothing you do, charger wise, at 14.4V, is going to change this. It is the battery that is causing this decline in acceptance and this is not unique to the Echo Charger nor is it a "float condition"...

But in this case, the manual says that the Echo charger will limit current to the aux battery..

Once you hold voltage steady this has to occur and is not a unique feature to the Echo Charger. Every voltage limited CV charge source has to do this.

The charger itself can shut down current to the aux battery at 14.4. Somehow I thought you said this was not true, maybe I just read things off (which has happened before..).

As I said it does not "shut down" when the start battery is full. It simply maintains the voltage not to exceed 14.4V.. Current declines naturally when voltage is held steady. The Echo does not shut off. I have had them running for days maintaining CV mode by simply holding source voltage at 14.8V... It follows the source charger and house bank voltage.

Also, the Echo charger can shut down current if the difference between the batteries is greater than 10 volts. It likely does this to limit internal heat.

It will also shut down on over heat. These are fault condition shut downs.... In normal operation, not a fault condition, the only thing that shuts the Echo down is the source voltage dropping below 13.0V..

But according the Echo manual, in the example above, even though the house bank was being charged at 15 volts (just what I picked for the example, you would "mostly" not want this), the Echo charger would connect both batteries at 13 volts but when the aux battery reached 14.4V, the Echo charger would limit or reduce to zero the current to the aux battery so that the aux battery does not go above 14.4.

The acceptance of the start battery at 14.4V and X% SOC is the determining driving factor of how much current it needs from the Echo Charger. It can reduce to zero if there is an overshoot of voltage, just as any charger does, but once that voltage decays back to 14.399V (not really that accurate) it is right back on to holding that voltage limit. My point is it does not turn off as many assume it does, it simply maintains the voltage...

 

[Maine Sail]

does the ACR in fact, actually act as a combiner to supply high amperage from the "house" when/if the starter needs more amps than the "start" battery has in it to give?...(such as a damaged battery, or too small of battery)

In short no. However, there is always a "however", the ML-500 ACR which is a 500A capable latching relay/ACR can be manually forced into combine mode and can do this. This is a much more expensive product though.

The standard 120SI ACR does not do this and has no means of "force parallel" and that is what the battery switch is for... It does however have the ability for start battery isolation but even folks who buy the Blue Sea Dual Circuit Plus battery switch, claiming they did it for isolation of the starting bank from house to avoid surges and such, rarely if ever wire them properly to drop the relay when the start button is depressed. In well over 100 factory and DIY ACR installations I've seen I have yet to see more than two where they actually used the start isolation "SI" feature.. You'd be amazed at how many power boats now ship with Blue Sea ACR's as standard equipment...

the whole point of my post was to simplify a rather indepth explaination of how it all works together, and that if the ACR gets connected correctly, its basically fool proof....

Yep one of the true "set it and forget it" items on boats. Still many folks install them incorrectly due to a lack of understanding of how they actually work. Once installed correctly they just sit there and work, for years & years....

the above paragraph is meant to explain in a short simple way that it does NOT automatically combine the banks for starting when you hit the starter switch, because any rate of transfer between the banks would be too slow for that purpose.
but maybe im wrong...

You are correct that it does not combine banks for starting. It can however isolate them for starting, if wired correctly.

 

[walt]

The issue I have is that what you are saying is different than what the manual says.. (and the hardware likely easilly suports what is in the manual - ie, no extra cost for doing it the way the manual says).

And I guess you are saying the manual is wrong because you measured this

I have had them running for days maintaining CV mode by simply holding source voltage at 14.8V... It follows the source charger and house bank voltage.

If I understand what you said, you had a main battery at 14.8 volts (held by a charging device) and a echo connecting the two (and wired correctly) and the echo charger held the second aux battery at 14.8 volts.. The manual would indicate that the aux battery would be at 14.4. Maybe I don’t understand your test conditions (including temperature)?

What I read in the manual is that the device measures both main and aux battery voltages. Between the two is a controllable current source with a maximum current of 15 amps.

The Echo device is measuring the aux battery and if it senses the voltage getting up near 14.4 volts, it will cut back on the current (which it can control) coming from the main battery to the aux battery. This is simply how any battery charger works and because of acceptance, the Echo feedback will cut the current way back because that is all that is needed to keep the aux battery at 14.4 volts.

Here a simple experiment to find out. Get a charger that can equalize and connect it to a main battery with an aux battery connected using an Echo charger.

The equalize voltage on the main battery will get up to about 15.5 volts.

If you measure 15.5 on the aux battery connected by the echo charger (after some time), I would agree that you are right and the manual is wrong. But the manual says that in this case you would measure 14.4 on the aux battery even though the main battery is at 15.5 volts.

 

[Maine Sail]

There is an auxilary battery that you normally dont put a load on (even starting) since you always want to make sure its fully charged. Its your safety backup.. You can only use the aux battery by manually switching it in.

The only reason for starting off the house bank is really for when your boat already has a 1/2/BOTH switch and you want to make the use of the boat & switch more simple by not moving the battery switch all the time. Because the house bank is usually significantly larger than the starting bank using the house bank for starting is a no brainier and works very well. You will still want to start occasionally off the reserve battery or test it occasionally.

Obviously if you have a different switch configuration, with a dedicated starting battery, there is no need to use the house bank for starting. Just a different approach for those who don't want to replace a perfectly good switch.

 

[walt]

My point is it does not turn off as many assume it does, it simply maintains the voltage...

maybe we are just interpreting something different. The Echo connection to the aux or starting battery has voltage sensing which feeds back to the current drive. When the voltage goes over 14.4, the current gets cut back (even reduced to zero). If the voltage drops below 14.4, the feedback increases the current so that the voltage rises again.

This control loop would operate very quickly and if stable would just hold the voltage right at 14.4.

Technically... yes it does not "turn off" the connection to the aux battery..

 

[Maine Sail]

maybe we are just interpreting something different. The Echo connection to the aux or starting battery has voltage sensing which feeds back to the current drive. When the voltage goes over 14.4, the current gets cut back (even reduced to zero). If the voltage drops below 14.4, the feedback increases the current so that the voltage rises again.

This control loop would operate very quickly and if stable would just hold the voltage right at 14.4.

Technically... yes it does not "turn off" the connection to the aux battery..

The problem is most owners read the manual and assume it does two things.

Floats then turns off.

Then I get the call and have to explain to them the manual is misleading. Yes it can turn off due to over voltage but the duration is usually fractions of a second...

Here's my most recent it went something like this.

"Hi RC I got your number from so and so."

"Thanks for calling what is the problem?"

"I think my Echo Charger defective because it is not floating my start battery and even after four hours of motoring my start battery is still at 14.3V."

"That is normal behavior and it is doing what it is supposed to do. The Echo Charger follows the voltage of the house bank but limits the max voltage to the start bank to 14.4V.. What do you have for an alternator regulator?"

"It's the factory regulator and my house bank gets to 14.6V"

"If you want the Echo Charger to float you will need a regulator for the alternator that has a float voltage."

(Blah, blah, blah lots of questions about how it is wired)

"I still think it is defective can you come out and look at it?"

"I certainly can but unless what you've told me about the wiring is not correct I will put my meters on it and most likely tell you the same thing plus hand you a bill. I have ridden this pony before and know it well."

Long and short.... Go to boat check Echo, working fine, mark up his Echo manual with red ink, fix a couple of minor 10 minute wiring issues, test his batteries (gotta feel like he got something out of the service call) hand owner the bill....Thanks Xantrex!!