Battery recovery voltage, 13V

[ayates]

In monitoring a starting battery (8D, flooded lead acid), I see it recovering to 13.0V after usage (no charging source). I always thought a "full" battery would be around 12.6/12.7V. 13V seemed to be higher than expected.



Any experience/thoughts on this?




Thanks,



Allan.

[Calif.Ted]

Most regulators are set at 13.5 volts, immediately after charging battery may read 13 but 12.7 is what a fully charged battery should read after resting I believe.

[ayates]

This came up, as I just installed a Blue Sea 7620 automatic charging relay, and it is seeing the 13V as a charging voltage, and closing the relay.


The house load draws the starter battery down a little, the relay opens, the starter battery recovers, and the cycle starts again. Eventually the starter battery wouldn't recover to this extent, but is certainly not desired behaviour.





Allan.

[Bleemus]

Why are house loads drawing the starter battery down?

[smac999]

this is not pluged in / no solar or any charging? an ACR should never turn on without any charging. a full battery is 12.7 or .8. normally when you turn a charger off. the acr will stay on for maybe 15-30 mins. it will pull a little from the start battery. but the start battery will quickly drop down under 13 and the acr will shut off and stay off. if its' turning back on, you must have a charging source.

[Paul Elliott]

How long of a recovery time are you talking about? If the battery is topped off to 13+ volts, and you briefly load it, the voltage will drop during the load and then recover -- possibly to 13V for a while. With no load and no charging source a fully-charged battery will eventually stabilize at a lower voltage, perhaps around 12.7V or so depending on the battery type.

[sailinglegend]

You haven't posted any of your details on your Profile so we don't know what your boat is or what batteries or charging sources are - all this is helpful.

Why an 8D battery for the starter? If this is an AGM it may well come back up to 13v after being charged.

When the relay closes it chargers up the other battery. If the house battery is being charged then the starter is getting charged too! So the cycle will continue.

Also most importantly this is a dual sense relay so if the house is being charged then the relay closes and charges the starter.

You need a more intelligent and manually adjustable system - like the SmartBank.

[john61ct]

The ACR staying open while no charge is present is not usually a problem in practice during normal cruising cycling.

When in storage you should be isolating manually.

There are designs where this is done on purpose, LVD adjusted downward as far as possible, long as enough charge is always remaining in the "Starter segment" for reliable cranking.

[sailinglegend]

Originally Posted by john61ct

The ACR staying open while no charge is present is not usually a problem in practice during normal cruising cycling.

When in storage you should be isolating manually.

There are designs where this is done on purpose, LVD adjusted downward as far as possible, long as enough charge is always remaining in the "Starter segment" for reliable cranking.

I don't really understand any of this post relative to the OP's question!!!!

[john61ct]

That's OK, as long as the OP understands it.

Perhaps if you read their subsequent post you will see how it is relevant.

Or, if you literally do not understand the meaning of some word or phrase, ask specifically and I will clarify.

[Zil]

The op's ACR is staying closed. Or more annoying, it is cycling. The question is how long does this happen? Once or twice until the voltage on the starter stays down or longer?

[john61ct]

Good ACRs have time delays to prevent chatter.

But cycling every say 20-40min does no harm.

Yes setpoint adjustability would be nice, but that is a very rare feature even in top-notch units.

[john61ct]

I have to say I thought Blue Sea's delays were longer.

Relay Contact Position:


-Combine (30 sec.) 13.5V
-Combine (90 sec.) 13.0V

-Open Low (10 sec.) 12.35V
-Open Low (30 sec.) 12.75V

But still, not a problem functionally.

[ayates]

Originally Posted by Paul Elliott

How long of a recovery time are you talking about? If the battery is topped off to 13+ volts, and you briefly load it, the voltage will drop during the load and then recover -- possibly to 13V for a while. With no load and no charging source a fully-charged battery will eventually stabilize at a lower voltage, perhaps around 12.7V or so depending on the battery type.

Unfortunately the current instrumentation isn't enough for me to track that precisely. My observation was that it happened a couple of times in the hour I was analysing the system. The relay makes a very loud clunk, so it is obvious to everybody in the vicinity. Which then results in non-confidence in the overall system.

Originally Posted by sailinglegend

You haven't posted any of your details on your Profile so we don't know what your boat is or what batteries or charging sources are - all this is helpful.

Why an 8D battery for the starter? If this is an AGM it may well come back up to 13v after being charged.

Simplified schematic attached. I didn't do the engine work, the 8D size was picked by somebody many years ago. It is flooded lead acid.

As John indicated, the there adhoc closing of the relay is benign. While I wasn't expecting battery recover to 13.1V, I can now see that this is reasonable operation. I am surprised that Blue Sea did not take this into account with their design.

The intention of the relay is to enable automatic house bank charging when the engine is running. I don't need the reverse. Thus I could use an engine signal to disable the charging relay when the engine is not running.

The most expensive Victron charging relay does support multiple profiles, a couple of which have >13V kick in points.


Allan.

[john61ct]

Note to others, if alternator is the only source needing combining, a $50 ignition relay setup will do as well.