How to get Tachometer with Alternator off?

[SailorGerry]

Originally Posted by senormechanico

Perfectly.

Actually, better than perfectly, almost NO voltage sag during cranking regardless of state of charge.

I have one bank on my boat of 200 aH LiFePo4's and have all the toys aboard.

We live exclusively on solar when on the boat for weeks at a time.

Bingo! As fellow LiFePo4 users know, Lithium batteries don't even flinch when starting a 75 hp diesel! So why have a separate "starting" bank? I can't think of a reason. I guess I could re-name my 200 ah reserve as "starting" - maybe that would make me more "safe"? The only reason a have a FLA reserve bank is because I already owned them, and I had extra room after removing the "dead lead" from the boat. I just completed a 850 nm passage and the Li batteries performed flawlessly!

So - back to my question, since LiFePo4 banks don't like to held at a hi SOC for long periods of time, how do I turn off the alternator, and still get tach data on a new(er) Yanmar?

[SailorGerry]

Originally Posted by tinkrman69

making consession for the weight of a starting battery IMO is like considering the weight of a ditch bag as too much. there are a lot of things attached to the house batteries that can unexpectedly drain the batteries...then how do you start the engine? Sounds like your trying to invent a square wheel.

I have a battery management system that that has a low voltage alarm and a disconnect if the battery voltage or capacity gets too low. The Li battery bank will start the engine even at the pack low-voltage level. Or, I can start start with my reserve battery bank. Oh, then there is the bow thruster batteries I could use. No square wheels here. What was the question again

[Jman]

SailorGerry,

Did you even read my post #7? First you asked how to keep the tach going while changing battery banks. Now you are asking when I turn off my alternator (battery banks are charged or over charged), is your regulator not handling this for you? Are you turning off the entire ignition system or just breaking the alternator field wire? Based on some of the other responses it seems unlikely that the yanmar tach is running off the alternator at all.


Sent from my iPad using Cruisers Sailing Forum

[SailorGerry]

Originally Posted by Jman

SailorGerry,

Did you even read my post #7? First you asked how to keep the tach going while changing battery banks. Now you are asking when I turn off my alternator (battery banks are charged or over charged), is your regulator not handling this for you? Are you turning off the entire ignition system or just breaking the alternator field wire? Based on some of the other responses it seems unlikely that the yanmar tach is running off the alternator at all.


Sent from my iPad using Cruisers Sailing Forum

Yes Jman, I read your post - thanks! Just now trying to catch up with spotty cell coverage. WiFi and cell service is difficult for cruisers!
I did not say I was charging, I said I was "cycling", meaning I was halting all charging sources and letting the SOC drop to 20-25% before re-charging. That's why the alternator is off. And, I am not turning off my entire ignition system off, as I have a diesel. I'm cutting the ignition wire to my Balmar MC-614 per Balmar's recommendation (rather than the field wire) for a lot of technical reasons unimportant to this discussion. And yes, my Yanmar 4JH4-TE does use the alternator for the tach feed.

[Jman]

Then I would just say adjust the regulator to float at a lower level and not worry about cycling at all. Float at 13.2 or 13.3 and it will take care of it.


Sent from my iPad using Cruisers Sailing Forum

[smac999]

Originally Posted by Jman

Nope, you never charge at anything above 13.9. LA does not receive proper charging at that. Echo charger can't change charge voltage, just at what point it kicks in.


Sent from my iPad using Cruisers Sailing Forum

so the FLA last 6 years instead of 8. you lose $50. peanuts if you have a li bank as well. it would work just fine and would be the simplest solution if a FLA bank is on board. an on board charger would properly charge them when at dock or on gen. but this question is off the original topic, which is how to keep the tach on, not how to charge a 2nd bank.


switching the alt to the FLA bank is probably the easiest solution to keeping the tach on. the lower voltage isn't going to harm anything. in his case the FLA should already be full all the time so the lower voltage isn't an issue. and is actually a better setup then 99% of the boats out there that have internal regs at 14.5v all the time on a full battery. at least he's part way down to float.

[mitiempo]

13.9 works fine, especially for a start battery. Many older alts are still set at 13.8. If the battery was down much it would take longer but a start battery is near the top after a start.

[tinkrman69]

I believe you said you have a separate charge controller for the lifepo bank if so run alt to engine batt - FLA's- with a on/off batt sw. run that an other sw with two banks one bank to separate controller for the life bank and the other bank to the FLa' s on the othe bank. when starting only have the engine batt selected when it's recharged - in around ten to fifteen minutes- select another bank to add in. when the extra load is sensed the atl will kick up the volts again and charging through the remote charge controller will charge the life batts. in the mean time save to get down to one type of batt system. by using two technologies in your electrical system, you've made it expensive in both time and money.

[mbartosch]

Not exactly an answer on the original question, but may be of interest here.

We have a 400 Ah LiFePO4 bank and a 100 Ah Lead Acid starter battery.

All primary charging sources (shore power charger, alternator, solar) only charge the LiFePO4 service bank.
The starter battery is charged using a Balmar Digital Duo Charge (DC/DC charger) on the load bus of the LiFePO4 service bank.

The Digital Duo turns on and charges the starter battery on any of the following conditions:
- engine ignition is on
- state of charge of starter battery is below 99 % (measured by Victron BMV 700 battery monitor, triggering the relay output of the BMV)
- voltage of starter battery is below 12.6 V (also measured by BMV 700, triggering relay)
- a manual switch is activated on the panel

In order to make sure the starter battery is charged properly all these conditions activate a timer relay which keeps the Digital Duo charge in on state for at least one hour.

In case of equipment failure we have the following options:
- Digital Duo charger fails: replace with spare component (which normally charges the portable dinghy battery pack)
- Starter battery fails: use jumper cables to temporarily connect LiFePO4 bank to engine starter

See attached schematics for the design.

[smac999]

Originally Posted by mbartosch

The Digital Duo turns on and charges the starter battery on any of the following conditions:
- engine ignition is on
- state of charge of starter battery is below 99 % (measured by Victron BMV 700 battery monitor, triggering the relay output of the BMV)
- voltage of starter battery is below 12.6 V (also measured by BMV 700, triggering relay)
- a manual switch is activated on the panel

.

these conditions but only when this wire is also over 13v as well though correct? as the on /off wire on the duocharge still only works if the input is over 13v? or I am reading the manual wrong. looks like an interesting (and over complicated way) of hooking it up.


that doesn't make sense because the ign wouldn't be over 13v when the duocharge is off. so it would never turn on... weird.


I don't understand how they can use the same wire for the auto sense (needing over 13v) and for manual control, unless the manual control is always over 13v as well.

[mbartosch]

Originally Posted by smac999

these conditions but only when this wire is also over 13v as well though correct? as the on /off wire on the duocharge still only works if the input is over 13v? or I am reading the manual wrong. looks like an interesting (and over complicated way) of hooking it up.

The Duo itself is powered from the Input connection, not from the on/off wire.
The on/off wire is more or less an input to a digital switch which controls on/off state of the Duo, there is no current flowing in this connection when activated.
It also does not really care about the voltage on the wire.

As the Duo contains a step-up converter (it has to, otherwise it is impossible to charge the battery on the Output post from a battery of similar type on the Input) the actual voltage on the Input can be lower than the voltage required for charging.

Regarding overly complicated design: In this case and with my setup, the system will recharge the starter battery when needed even with engine off. This is how I like it because Lead Acid starter batteries really like being kept at 100 % SoC.

I just wanted to give an example on how to set up things, the recommended procedure of just connecting on/off to the ignition switch is perfectly sufficient and will imitate standard charger behavior.

that doesn't make sense because the ign wouldn't be over 13v when the duocharge is off. so it would never turn on... weird.

I don't understand how they can use the same wire for the auto sense (needing over 13v) and for manual control, unless the manual control is always over 13v as well.

The manual states that charging does not happen below 13 V on the Input (not on/off) post, so no problems with that. As the on/off only controls an electronic switch it does not really care about the voltage.

The setup I posted works without a problem for me.

[smac999]

Originally Posted by mbartosch

The Duo itself is powered from the Input connection, not from the on/off wire.
The on/off wire is more or less an input to a digital switch which controls on/off state of the Duo, there is no current flowing in this connection when activated.
It also does not really care about the voltage on the wire.

As the Duo contains a step-up converter (it has to, otherwise it is impossible to charge the battery on the Output post from a battery of similar type on the Input) the actual voltage on the Input can be lower than the voltage required for charging.

Regarding overly complicated design: In this case and with my setup, the system will recharge the starter battery when needed even with engine off. This is how I like it because Lead Acid starter batteries really like being kept at 100 % SoC.

I just wanted to give an example on how to set up things, the recommended procedure of just connecting on/off to the ignition switch is perfectly sufficient and will imitate standard charger behavior.



The manual states that charging does not happen below 13 V on the Input (not on/off) post, so no problems with that. As the on/off only controls an electronic switch it does not really care about the voltage.

The setup I posted works without a problem for me.

ah if it's sensing the voltage on input wire that makes more sense. the manual is actually pretty unclear in it's wording. still the manual switch then still only works if you have a charging voltage on the house. so it's not completely manual. more like manually turning on and off auto mode.

[mbartosch]

Originally Posted by smac999

ah if it's sensing the voltage on input wire that makes more sense. the manual is actually pretty unclear in it's wording. still the manual switch then still only works if you have a charging voltage on the house. so it's not completely manual. more like manually turning on and off auto mode.

I can confirm that charging does work regardless of presence of charging source, my system recharges the starter battery even if no charging source is active. The resting voltage of my house bank (4S4P Winston LiFePO4) is about 13.3 V which is greater than 13 V so automatic recharging works any time the Duo is activated.
If State of Charge of the house bank is lower, this threshold might not be reached, in this case no automatic charging will happen. I actually like that.

***

It might be possible to modify the 13 V threshold, but I have not tried it yet. The manual is vague and talks about "Lower and upper voltage limit".
I am not sure, but an interpretation might be that the "Lower voltage limit" is the threshold on Input above which the Duo will activate, while the "Upper voltage limit" might be the absorption voltage on the Output post. However, this is guesswork and untested.

[mbartosch]

I have been trying to get information about the nature of the Tachometer signal itself (in my case the one coming out of a Balmar MC 614) but was unable to find any details on this.

I would like to "extract" the tach signal for processing in DIY electronics (something like tachometer software on a micro controller). Can anybody tell me the nature of this signal?

I *assume* it's a 12 V square wave. From what I read I'd expect the frequency to either equal the actual RPMs (i. e. 1 kHz => 1000 RPM) or being a multiple of that (probably 6 or 12 times this value, e. g. 12 kHz => 1000 RPM).

I'd appreciate any information or pointers to documentation.

(Apologies for the slightly offtopic post for this thread, but didn't think starting a new one was necessary.)

[Stu Jackson]

Originally Posted by Jman

Are you just turning the ignition circuit off? If so you are losing everything including oil pressure warnings. You can stop the charge by putting a switch in the alternator field wire. This is what we do.

^^^^^^^^

Don't disconnect the alternator output, ever.

Don't shut off the ignition circuit, 'cuz you'll do what is described above.

Just turn off the signal to the regulator, which is essentially the field wire.

That will keep your gauge circuit operating.

Done.