Piers
Well-Known Member
Quick question if I may - is it OK to run the battery charger whilst the engines are running?
Thank you - Piers
Thank you - Piers
Mixed charging - is it OK
- Thread starter Piers
- Start date
Portofino
Well-Known Member
Do you mean run the Geny and via the AC breaker switch turn on the bat charger(s) --as well as have the alternators on the engines ( which you can,t turn off ) running at the same time ?
If so ? --- I would not do it intentionally - for risk of blowing up something cos too much charge .Having said that --
I guess it depends how the boats wired up and what exact control devices are used to link it all together ,the charging system .
If its a so called smart AC charger then it may detect the extra ah from the engines alternators and go to float or some other low setting ? ,but then agian if the bats are low it may be grateful for the extra ah from the alternators .
Starting our engines with shore power and both bat chargers has thus far not damaged anything ,if it's done occasionally ,it's by error and the shore power is soon off ,as we depart .
Alternators x2 are 55 ah ,
Main recent smart charger 80 ah , + smaller dedicated Geny bat charger ,
Not sure of bat cap --think 120 ah x4 arranged in pairs for 24 V , engine and domestic ,with a x over switch .
One seperate 60 ah Geny bat -
I suspect it best not to do it ---- run, Alternators and main charger together for a long period --but as said depends how it's all connected together and bat cap to prevent overload ,to much charge .
What does the hand book say for the boat ?
If so ? --- I would not do it intentionally - for risk of blowing up something cos too much charge .Having said that --
I guess it depends how the boats wired up and what exact control devices are used to link it all together ,the charging system .
If its a so called smart AC charger then it may detect the extra ah from the engines alternators and go to float or some other low setting ? ,but then agian if the bats are low it may be grateful for the extra ah from the alternators .
Starting our engines with shore power and both bat chargers has thus far not damaged anything ,if it's done occasionally ,it's by error and the shore power is soon off ,as we depart .
Alternators x2 are 55 ah ,
Main recent smart charger 80 ah , + smaller dedicated Geny bat charger ,
Not sure of bat cap --think 120 ah x4 arranged in pairs for 24 V , engine and domestic ,with a x over switch .
One seperate 60 ah Geny bat -
I suspect it best not to do it ---- run, Alternators and main charger together for a long period --but as said depends how it's all connected together and bat cap to prevent overload ,to much charge .
What does the hand book say for the boat ?
Piers
Well-Known Member
Yes. Stb batt bank is separate from port batt bank. Stbd engine charges the stb bank, port eng charges the port bank. The batt charger (Mastervolt Chargemaster) charges each nabk separately
Not a lot, and what it does say is inaccurate.
benchmark
Well-Known Member
My boat hand book specifically says not to start the boat if it is on charge so i do not do it, my dock neighbor has the same boat and does not care, he has done as he likes for the last 3 years . Though i may add that he has burnt his generator out once in that time, not sure if it has anything to do with it.
rafiki_
Well-Known Member
if your engines are running, then you already state that they charge the batteries. I don't think your system will allow mains charging at the same time?
kashurst
Well-Known Member
It shouldn't matter at all. If you start the engines with the mains charger running, the charger will at first notice a big drop in battery voltage as the engine cranks and will try to compensate for that, the charger has a maximum output that will be carefully protected by the charger. It won't be able to keep up with cranking current draw, but will do it's best without damaging itself. (People do lots of stupid things like short circuit chargers etc and they are designed to withstand quite a bit of abuse, errors etc)
Once the engine is running and the alternators kick in, the charger will see a rise in battery voltage and go into trickle mode or similar.
If the charger is one of the new wizzy ones that periodically charges at a higher voltage than the alternator output, the alternators will reduce output as they will perceive a very well charged battery.
Once shore power is off normal alternator behaviour will resume.
I have been doing this for 18 years on 5 boats, don't worry about it. I doubt the blown genny is related to battery charging issues.
Boat manual may state don't do this, but that could be for a variety of other reasons.
Once the engine is running and the alternators kick in, the charger will see a rise in battery voltage and go into trickle mode or similar.
If the charger is one of the new wizzy ones that periodically charges at a higher voltage than the alternator output, the alternators will reduce output as they will perceive a very well charged battery.
Once shore power is off normal alternator behaviour will resume.
I have been doing this for 18 years on 5 boats, don't worry about it. I doubt the blown genny is related to battery charging issues.
Boat manual may state don't do this, but that could be for a variety of other reasons.
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Piers
Well-Known Member
I should have added that since i run at displacement speed, the alternators are not spinning sufficiently quickly to provide enough current to compensate for the drain taken by the nav gear I have. hence, the batteries gradually run down. Rather than run at a higher rpm, I was hoping to run the generator and use the charger to provide any extra.
rafiki_
Well-Known Member
Crikey! How many screens are you running? Could you try alternators with either a higher output, or a different pulley size to increase the output?
A note of caution when on shore power. I am pretty sure that shorepower "spiked" an alternator on Rafiki last year. I am careful to disconnect shorepower before I start the engines. The shorepower stations at the marina were renewed last year, and as a consequence caused a few electrical issues for me.
Rgrwynne
Active Member
Interesting, because I never considered this issue. I often start up engines to warm them up while still on shore power. When ready to depart I disconnect. I have somebody who runs the engines every month for me, when I am not there, and this has been happening since 2008. I am not aware of any problems, although I have to say I do not think it would be a recommended procedure.
Portofino
Well-Known Member
Are you absolutely sure ?
Tested the output @ D and P speeds or have any bat drain / charge info on the panal ,like a basic V guage and seen it drop
6-8 hrs or what ever into a D speed cruise ?
Or a Ah charge guage ( on both sets ) so you can see how hungry they are at various times into a long D Speed cruise ?
If the alternator out put is not enough ,the Ah guage ( juice going in, not what its asking ) will be low , if you then fire up the Geny and flick on the main Bat charger ,and this guage shoots up to say 40-60 ah before floating down in the next hour or so - ,then the bats are indeed being fed a lean charge diet by the D speed engines .
Just to be safe turn off the engines before turning on the Geny and charger ,a few hours into a cruise ,or when you arrive @ an anchorage .As I said watch the immediate ah demand , if it's significantly greater ,then the alternators have not really kept on top of the charge ..
Presume you do or plan to do pretty long stints @ D ? .
Seems odd a few extra screens + a fridge or two ? + any other stuff drain faster than the alternators can recover at D Speed .
What sort of ,where are you with the engine rpm ,s @ D compared to ave P
Eg for me P is 1750 ave
D 850 rpm
Tick over 600 .
Not convinced spinning alternator a bit faster make s much of a difference over 6-8 hrs or what ever ?
I know it's not scientific ,but I have a alternator out put voltage on the MMDS , it's stays at 26.5 V all the way through the rev range ,so I can see -I think - what's coming out V wise and it's the same regardless of P or D -speed .
Bigger bat bank needed ? - increase storage ??
Or as you suggested run the Geny + charger ----- if it's safe !
Piers
Well-Known Member
Don't laugh...here goes for the Pilot House:
1) Furuno nn3d black box chart plotter with a 19" Hatteland screen
2) Furuno 2117 black box radar with 6' scanner with a separate 19" Hatteland screen
3) 2 x 12" Hatteland screens for cameras and FLIR
...and for the Fly-bridge
4) 2 x 12" Hatteland screens to repeat chart plotter and radar
...plus instruments, radios (I said don't laugh!), stabilisers, 3-aerial sat compass, horn compressor, with an inverter for fridge/freezer and mains power for kettle, etc.
Now that sounds a really good idea. Thank you..
Interesting piece of info. Thank you.
Piers
Well-Known Member
Although I have instruments for almost everything, there're no ammeters to show charge/discharge. Thinking about this, it seems daft not to have this info. I will call my electrics guru tomorrow to discuss.
The max we tend to do is 16 hours.
At 1150 to 1200 rpm, the alternator voltmeters constantly flicker between 24v and 28v. Increasing the rpm to 1400 keeps the volts at 28v. Hence, it seems that the lower rpm is barely enough to excite the alternators.
Piers
jfm
Well-Known Member
+1. I often run the mastervolt chargers (powered by genset) and engines at same time, = 480 amps at 24v theoretically not counting the gensets' own alternators. Have done this for 10+ years on several boats, with no problems. A charger (whether engine alternator or mains charger or several in parallel) wont put more amps into a battery than the battery will accept, and the voltage effects are as kashurst says, ie no problem
Most people are happy to charge batteries from genset at anchor with main engines off. Well, when you're doing that the genset's alternator is in action, and nothing blows up.
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Piers
Well-Known Member
jfm
Well-Known Member
Crikey Piers you need to fix that. Just get one or two bigger alternators. On my engines the original Cat alternators were de-specced and a pair of mastervolt 150amp (@24v) beasts were fitted. These run to 6000rpm so with a x3 pulley they give 80 amps @24v when main engines are idling. You need a double pulley because there is a lot of torque needed to drive them (4Kw each). http://www.mastervolt.com/products/alternators-24v/alpha-24-150-mb/
MapisM
Well-Known Member
Do you mean the "either" idea, or the "or"?
Careful with the "or", because by changing the pulley you would have an alternator producing a proper output at low rpm, but potentially damaged at higher engines rpm.
I agree that it could be a brilliant solution, but I would check the max rated speed for the alternator first, and do some math.
Piers
Well-Known Member
Good question - I've just emailed my Cummins contact asking some questions. Thank you.
MapisM
Well-Known Member
I don't dare thinking how ridiculous was the price reduction on the C32s, if any...
Didn't you consider leaving the OEM alternators in place (disconnected) and install the MV things as an addition, rather than replacement?
That would have provided a nice backup, even if not man enough to run all you need...
Piers
Well-Known Member
All understood. I'm investigating both possibilities. I tend to favour the smaller pulley since it's simpler option and the tension bar would absorb the additional belt slack. But the higher RPM at max engine rpm is a question I've asked.
MapisM
Well-Known Member
Just fwiw, ref. your initial question, sometimes on my old boat it happened that I turned the engines on before disconnecting the shore power, but when I did that, the warning light of the engine whose alternator charges the domestic bank went off - though without any other perceivable problem (V-meter was still fine).
I never bothered investigating further anyway - in fact, I thought that it was a nice reminder to disconnect the shore power...
I never bothered investigating further anyway - in fact, I thought that it was a nice reminder to disconnect the shore power...