90 Amp Limit

[mark99]

We have a 140 amp alternator going through a sterling fancy charger box.

 

We also have a shore supply via Victron.

 

And a 6.5 KVA inboard dedicated Genny going through its own control panel then via Victron Multiplus.

 

No matter how low my batteries are, any one of the three electrical charging inputs never goes above 90A according to my Victron electrical monitor.

 

Reason being?

 

(I'm weak on electrics!).

Edited July 26, 2015 by mark99

[Alan de Enfield]

Your Alternator will never put out 140 amps (unless you get it doing 6000 rpm) - if you are getting 90 amps you are doing well.

 

Your Victron Multiplus is an Inverter and a battery charger - it doesn't matter how big a generator, or how much shore supply you have it will only charge (at most) at what the charger is rated at - example it will have a 'number' something like 2000/90/12 which means it is a 2000 watt inverter, it is a 90 amp battery charger and is 12v.

 

It will only charge at the max (90 amps ?) either from the alternator or the battery charger for a short time (maybe minutes), as the battery starts to charge the current will drop - after 1 hour (for example) you may be down to 50 amps, or even 30 amps.

 

The batteries control the charger output - the charger does NOT control how many amps the battery gets.

[GUMPY]

How many batteries and how discharged are they?

[mark99]

I think it's a 2500/12/120 invertor.

 

8 * 6V Rolls batteries so 4 @ 12V.

 

Battery - high/mid 11V or so SOC so not right down to limit

Edited July 26, 2015 by mark99

[Alan de Enfield]

At 11.5 volts your batteries are virtually 'flat' (90% discharged).

I know you can treat Rolls batteries 'rough' but doing that regularly and they will be buggered in weeks.

 

 

In an ideal world you should keep them above 12.1 volts (50% SOC)

Edited July 26, 2015 by Alan de Enfield

[MtB]

90 Amps? I'm delighted if I see 9 Amps.

 

WTF are you running in your boat to need more than 90 Amps charge rate?!!!!!

[mark99]

90 Amps? I'm delighted if I see 9 Amps.

 

WTF are you running in your boat to need more than 90 Amps charge rate?!!!!!

 

I'm into understanding the kit rather than wanting more.

 

Only once were the batteries down to mid 11's - when we first got it. After a full evenings use they are normally a shade above/below 12v.

Edited July 26, 2015 by mark99

[Alan de Enfield]

 

 

Battery - high/mid 11V or so SOC so not right down to limit

 

So is this a hypothetical question, or it happened once when you first bought the boat ?

 

If your batteries are kept above the 'magic' 50% SOC then they wont take a high charge, they will take a steadily 'falling' charge until it gets to around 3 or 4 amps - this could take many hours to achieve. You then get to the state of diminishing returns - you run your engine / generator, using another hours worth of fuel and wear & tear and put in maybe 0.5 amps.

[mark99]

 

So is this a hypothetical question, or it happened once when you first bought the boat ?

 

If your batteries are kept above the 'magic' 50% SOC then they wont take a high charge, they will take a steadily 'falling' charge until it gets to around 3 or 4 amps - this could take many hours to achieve. You then get to the state of diminishing returns - you run your engine / generator, using another hours worth of fuel and wear & tear and put in maybe 0.5 amps.

 

 

It's hooked up to shorepower when not in use - it's a leisure use only.

 

I know the falling charge thingmy. My question is fairly simple - why only ever 89.9 (90 amps nominal) amps on initial charge. I wonder if there is a dip switch in the Victron limiting it as according to the earlier post it should shove 120 amps in it.

Edited July 26, 2015 by mark99

[Alan de Enfield]

The battery charger does NOT decide (or control) how much it outputs.

 

The state of the batteries (SOC) dictates how much the battery charger puts out

 

You could have a 1000 amp battery charger but if your batteries only 'wanted' 5 amps, that's all the battery charger would be 'allowed' to send down the wires.

 

It always makes me smile when people go on about their humungous alternator running on 'double-poly-notched belts', within a few minutes of running they will be outputting the same as the 55 amp alternator (on my old NB)

Edited July 26, 2015 by Alan de Enfield

[Nickhlx]

As Alan says..

 

On my Victron there are switch settings to limit the max charging current, presumably for when charging smaller battery banks. I set mine so that it won't charge at more than 50% of its capability, as its better / kinder to charge slower than at full blast, both for the battery heating and also the charger heating aspects - it rarely charges at more than a few tens of amps anyway as its permanently on a shoreline, and when not we are cruising, so they are almost always at full charge - I think the default setting is / was 75% on the 120 amp charger, which is why you are seeing 90 amps max... I also have a "max drain from the shoreline" control which I set to 4 amps (at 240 V a.c.) to make sure it doesn't cause the 6A trip to drop out...

 

Nick

[mark99]

As Alan says..

 

On my Victron there are switch settings to limit the max charging current, presumably for when charging smaller battery banks. I set mine so that it won't charge at more than 50% of its capability, as its better / kinder to charge slower than at full blast, both for the battery heating and also the charger heating aspects - it rarely charges at more than a few tens of amps anyway as its permanently on a shoreline, and when not we are cruising, so they are almost always at full charge - I think the default setting is / was 75% on the 120 amp charger, which is why you are seeing 90 amps max... I also have a "max drain from the shoreline" control which I set to 4 amps (at 240 V a.c.) to make sure it doesn't cause the 6A trip to drop out...

 

Nick

 

Thanks - as I suspected there is/may be a limit switch in the charger which stops it charging to 120A initially.

[OldGoat]

Nobody's mentioned the possibility of voltage drop from the alternator to the batteries -

 

Blocking diodes in the circuit?

Undersized cable between the alternator and batteries?

[Nickhlx]

That's because the issue here is that it's a setting, not an installation shortcoming... the clue was in the "never more than 90 amps", regardless of SoC or other variables

 

Nick

[Paul C]

 

You could have a 1000 amp battery charger but if your batteries only 'wanted' 5 amps, that's all the battery charger would be 'allowed' to send down the wires.

 

 

 

Yeah but if the batteries only "wanted" 5 amps BUT another device, say an inverter, "wanted" 995 amps at the time (I know the figures are figurative not real-world) then it could in theory, at the right revs, supply that.

[by'eck]

That's because the issue here is that it's a setting, not an installation shortcoming... the clue was in the "never more than 90 amps", regardless of SoC or other variables

 

Nick

 

But OP's concern was that it never exceeded this with either Victron charger or engine alternator, suggesting its battery capacity/design that is limiting the current draw rather than the Victron's charge settings.

 

Not familiar with Rolls battery charcteristics but it seems a likely explanation that (despite/because of) the relatively high charge current sources cause the battery plates surface quickly to become saturated, hence limiting current draw.

[RLWP]

 

Not familiar with Rolls battery charcteristics

 

Lots of stuff I don't understand here: http://support.rollsbattery.com/support/solutions

 

Richard

[mark99]

 

But OP's concern was that it never exceeded this with either Victron charger or engine alternator, suggesting its battery capacity/design that is limiting the current draw rather than the Victron's charge settings.

 

Not familiar with Rolls battery charcteristics but it seems a likely explanation that (despite/because of) the relatively high charge current sources cause the battery plates surface quickly to become saturated, hence limiting current draw.

 

When the Panda Generator (6.5 Kva) starts too which feeds into Inverter/Charger to batteries (6.5 Kva) it never exceeds 89.9 amp into batteries at initial start up).

 

Red = Rolls

 

[nicknorman]

When the Panda Generator (6.5 Kva) starts too which feeds into Inverter/Charger to batteries (6.5 Kva) it never exceeds 89.9 amp into batteries at initial start up).

 

Red = Rolls

The 89.9A limit will be arising from the Victron's charger settings - it matters not whether you are on shore power or on the Panda generator, they both route through the Victron. What is less clear is why the alternator should be thus affected. Are you quite certain that you also see 89.9A max when you start the engine with low domestic batteries?

[mark99]

The 89.9A limit will be arising from the Victron's charger settings - it matters not whether you are on shore power or on the Panda generator, they both route through the Victron. What is less clear is why the alternator should be thus affected. Are you quite certain that you also see 89.9A max when you start the engine with low domestic batteries?

 

Nick,

 

I suspect I don't have enough revs going (it's nowhere near 89.9) . I'll double check next time when a few revs on.

[bottle]

I think you have it sorted, just to confirm the Victron is set to 75% of maximum charge rate, out of the factory, it can be changed by the connection of an interface, computerr program, and laptop.

 

All available from Victron or someone may be near you that has all this and would be willing to set it up for you.

 

Just a bit of reading for you: http://www.smartgauge.co.uk/chargesize.html

 

To help you decide whether it should be changed.

[dmr]

If your batteries are part discharged, and if you start the engine and stick some revs on, then I would initially hope to see more than 90amps, though probably not the full rated output, This will then fall over the next few minutes as the alternator gets hot.

 

..............Dave,