Keeping the starting battery charged

[Davidhoy]

I just ordered an Echo Charger to keep my genset starter battery topped up. I chose the Echo Charger after much research, and several phone calls to Xantrex and Blue Sea Systems. The ACR will parallel the two batteries regardless of which has the higher voltage, so if your house bank is lower and the starter battery is full, you would in effect start charging the house from the starter - probably not what you want. The Echo Charger is very specific - it only sends current to the secondary battery when it senses a charging voltage on the primary. That's a winner in my book. And you can get them for less than $100!

[Q Xopa]

Originally Posted by john61ct

At different voltages then DC-DC / B2B chargers come into the picture, more expensive.

A simple / cheap DC converter will do, but needs manual babysitting like the 1-2-B switch approach, too easy to screw up if you are forgetful like me.

Yes exactly what I have done. Using a B2B between my 24v House to charge my 12v Start batt.

However I also have a ACR to only have the B2B charging and drawing down the House bank when there is a charging source operating.

However if I was doing it now I would have used a Victron FET batt Isolator instead of the ACR so there is no possibility of excessive flow between banks.

Of course there are many ways to skin a cat.

[Scubaseas]

One more for Echo charger

[john61ct]

Originally Posted by Q Xopa

However I also have a ACR to only have the B2B charging and drawing down the House bank when there is a charging source operating.

Most good B2B already include that VSR functionality.

In fact afaik only the new cheap Renogy units don't.

Sterling's can be set up to manually get switched on, but that's designed for IGN input when used for alternator input only.

[john61ct]

Originally Posted by Q Xopa

Of course there are many ways to skin a cat.

Hundreds, all with their little quirks and variations.

For example, Echo Charger is one-way only, limits current to 15A, drops voltage a fair bit (0.4V)and purposefully limits output V to 14.4V max, even if the source V is much higher.

Otherwise "works just the same" as standard VSR/ACRs 8-D

BTW these can be considered added-value features rather than flaws, all depends on the use-case context.

For this one, NP as long as **all** significant charge sources are directly wired to a House, put out at least as high a voltage as Starter wants, and the EC only used to keep a Starter topped up that is happy with 14.4V max.

Of course Starter not getting optimal coddling is rarely an important problem.

[accomplice]

Devil's advocate question: Why not preferentially charge starting batteries from house bank even when house bank is not being charged?

Many of us run coulomb counters and monitor battery voltage on the house bank to know when we need to run the genset, etc. to charge -- but do others take the same approach to monitoring start batteries? It would be most unfortunate if one needed to start the genset or auxilliary to charge the house bank but found the starter batteries insufficiently charged to handle the task. Presumably the housebank will be drawn down faster than the starting batteries, but this may not always be the case, especially with batteries of different age, type and self-discharge rate.

We do use an ACR for windlass/thruster, such that they are only charged when the house bank is charged -- but that is because they are not needed to start an engine to charge the house bank.

[Stu Jackson]

Echo Charger Use Warning from Maine Sail: http://www.sailnet.com/forums/electr...rger-rant.html

[john61ct]

Originally Posted by accomplice

Why not preferentially charge starting batteries from house bank even when house bank is not being charged?

Many of us run coulomb counters and monitor battery voltage on the house bank to know when we need to run the genset, etc. to charge -- but do others take the same approach to monitoring start batteries?

A healthy properly sized and installed dedicated Starter battery on well-maintained engines never drops below 99.7% SoC, requires miniscule average Ah charge input per day.

They are relatively cheap, and should be replaced on a schedule.

So heroic care measures are not required.

And one bank is never charged from another bank, that is just shorthand for the circuits being combined/isolated.

The charging current comes only from actual sources, shore charger, alt, genset, wind and solar, etc

[Q Xopa]

Originally Posted by john61ct

Hundreds, all with their little quirks and variations.

For example, Echo Charger is one-way only, limits current to 15A, drops voltage a fair bit (0.4V)and purposefully limits output V to 14.4V max, even if the source V is much higher.

Otherwise "works just the same" as standard VSR/ACRs 8-D

BTW these can be considered added-value features rather than flaws, all depends on the use-case context.

For this one, NP as long as **all** significant charge sources are directly wired to a House, put out at least as high a voltage as Starter wants, and the EC only used to keep a Starter topped up that is happy with 14.4V max.

Of course Starter not getting optimal coddling is rarely an important problem.

Honestly, with all your abbreviations code Im not sure I follow exactly what you are talking about.
As long as you do Im sure its fine for you.

[john61ct]

Yes the fact that the setpoint for combine/isolate is so low at 13V can cause issues for some use cases.

For example if the source House bank is LFP, then there will always be a natural current flow (even if very low, could be wasteful over time) to a target lead Starter.

Of course even that could be considered an advantageous feature for other use cases.

Key takeaway here - know the characteristics and care requirements of both banks being connected, and investigate the operating details of the combiner you are considering.

There is no "one best" magic bullet device that is "best" for all use cases.

The ideal would be a VSR with user adjustable setpoints, but those are rare and expensive.

[john61ct]

Originally Posted by Q Xopa

Honestly, with all your abbreviations code Im not sure I follow exactly what you are talking about.

Feel free to ask if google is not helpful.

[Q Xopa]

Originally Posted by john61ct

Feel free to ask if google is not helpful.

Ok thanks for the offer.
If you could see your way clear to spend an extra few seconds to write in full, instead of abbreviations, what you are referring to.
Even googling will usually result in many unrelated possibilities. From there is a guessing game so mostly a waste of time.
Or I, and assume others, will just assume your posts to be unintelligable.

[accomplice]

At 80F, lead acid batteries self-discharge at 4%/week. A few months without running that genset could reduce the genset start battery to < 50% charge -- assuming that it was topped off to 100% the last time it was run.

Complicate this by different battery ages and technologies and it isn't hard to see how a starting battery could run low ahead of a house bank.

We maintain separate house/starter batteries such that drain on the house will never deplete the starter banks. We maintain separate house/windlass-thruster batteries for the same reason and such that the high current wires from the battery do not have to run as far and sustain as large a voltage drop. We maintain a separate communications bank for the same reasons. The goal is to keep the house use from draining the other batteries, not the other way around since we will charge the house bank when it is depleted, but not necessarily know when the communications or one of the starter banks is depleted.

In theory, all the battery banks charge together and the house bank drains faster than any other bank. In practice, this isn't always the case.

[john61ct]

The most efficient, cost-effective and reliable solution is one big bank for everything, unless wire gauge over long distances becomes impractical.

Adding redundancy in the form of one more quality deep-cycling "Reserve" bank normally kept isolated except for topping up is IMO a good idea.

Which you use for cranking doesn't matter, should be switchable, and is a good occasional test that everything's working on the Reserve side.

Preventing a given Auxiliary load from pulling SoC too low, to ensure enough capacity for more Essential loads, is IMO best accomplished with adjustable LVCs, which can be tweaked to cut loads / circuits off the Main bank in order of ascending priority.

e.g. entertainment first, then fridge / kitchen. . . with safety / nav engine and cranking last.

Having multiple deep cycling banks each dedicated to specific functions wastes both money and capacity (see Peukert's Law), wears out banks more quickly, adds complexity, reduces reliability.

[Q Xopa]

Originally Posted by john61ct

The most efficient, cost-effective and reliable solution is one big bank for everything, unless wire gauge over long distances becomes impractical.

Adding redundancy in the form of one more quality deep-cycling "Reserve" bank normally kept isolated except for topping up is IMO a good idea.

Which you use for cranking doesn't matter, should be switchable, and is a good occasional test that everything's working on the Reserve side.

Preventing a given Auxiliary load from pulling SoC too low, to ensure enough capacity for more Essential loads, is IMO best accomplished with adjustable LVCs, which can be tweaked to cut loads / circuits off the Main bank in order of ascending priority.

e.g. entertainment first, then fridge / kitchen. . . with safety / nav engine and cranking last.

Having multiple deep cycling banks each dedicated to specific functions wastes both money and capacity (see Peukert's Law), wears out banks more quickly, adds complexity, reduces reliability.

Sounds like a good option.

Last time I suggested it you rightly said it was a waste of unused capacity.