720Ah batteries......... 80A or 160A charger

[jenevers]

Simple question!☺️??????

Edited January 15, 2016 by jenevers

[bottle]

Simple answer: either

 

but read this then decide

 

http://www.smartgauge.co.uk/chargesize.html

[TheBiscuits]

Complex answer.

 

Genny or shore power?

 

How often and for how long is the primary engine run?

 

What is the base load on the system while charging?

 

Solar?

 

All of these affect the answer.

 

The simple answer is that any charger that can supply more than you are using will charge the bank.

 

In the real world, you need to be able to charge the bank in a sensible timeframe for your needs. A month to charge might be acceptable for someone on shore power, but 4 hours will be too long for someone who only gets back to the boat at 6pm.

[nicknorman]

160A for me, if you have the capability to run it.

[peterboat]

i have 1500 ah of battery my alternator is a 160 amps i have solar that on a good day is 63 amps and the wispergen which is 70 amps all work but take different times to charge up the bank. i have no shore power charging system at all

[Paul C]

As post #3 really.....it depends on how long you have to recharge. If you were not time constrained, there is no point wasting the money on a more powerful, more expensive charger. If you are severely time constrained, remember that after bulk charge, the battery is not fully charged and needs a certain amount of time to reach as near as fully charged as practicable - simply throwing money at the charger won't work. This is where solar excels - it doesn't mind giving a long slow charge all day long. Of course, solar goes on strike in the winter....

 

So, not as simple to answer as first seems.

[OldGoat]

As everybody says BUT-

I did a quick google ('cos I didn't think such an animal didn't exist) and found various Sealey STARTER/Chargers. Is that of which you are thinking??

 

If that is so then mebe the answer is NO. I'll probably be corrected, but the high rate is only for a very short time = jump start a vehicle - p'raps 30 seconds??

Not a lot of use for charging batteries.

 

Or do you mean an alternator??

 

If you can look at battery performance 'curves' you'll see that batteries give you best capacity / running times if you charge them slowly. If you are on shore power and have 24/7 mains electricity, then even a 40amp charger will do the do the job well. Perceived wisdom is that the '20 hour charging rate' gives best results 720/40 = 18 fills that bill.

 

So that's another twist to the story.

Please come back and give some more details!

 

Edit: If a mains charger - get one that's a 3-stage type - it'll be even better for your batteries.

Edited January 15, 2016 by OldGoat

[emlclcy]

I have 250ah AGM batteries and the data sheet says 50A max charge

[peterboat]

its a miracle i am getting 10 amps from my solar today so all is well in my world

[emlclcy]

its a miracle i am getting 10 amps from my solar today so all is well in my world

what sort of array do you have?

[Loafer]

its a miracle i am getting 10 amps from my solar today so all is well in my world

 

I got 12.3 the other day with 3X100W and pointed straight at it!

[bottle]

It's all relative, depends on battery SOC any other equipment being supplied, clouds in the sky etc. etc.

[jenevers]

Complex answer.

Genny or shore power?

How often and for how long is the primary engine run?

What is the base load on the system while charging?

Solar?

All of these affect the answer.

The simple answer is that any charger that can supply more than you are using will charge the bank.

In the real world, you need to be able to charge the bank in a sensible timeframe for your needs. A month to charge might be acceptable for someone on shore power, but 4 hours will be too long for someone who only gets back to the boat at 6pm.

Answers.....

Genny

Varies but maybe 3 hours every other day. (160A alternator)

Base load??

800w of solar.

Edited January 15, 2016 by jenevers

[jenevers]

As everybody says BUT-

I did a quick google ('cos I didn't think such an animal didn't exist) and found various Sealey STARTER/Chargers. Is that of which you are thinking??

 

If that is so then mebe the answer is NO. I'll probably be corrected, but the high rate is only for a very short time = jump start a vehicle - p'raps 30 seconds??

Not a lot of use for charging batteries.

 

Or do you mean an alternator??

 

If you can look at battery performance 'curves' you'll see that batteries give you best capacity / running times if you charge them slowly. If you are on shore power and have 24/7 mains electricity, then even a 40amp charger will do the do the job well. Perceived wisdom is that the '20 hour charging rate' gives best results 720/40 = 18 fills that bill.

 

So that's another twist to the story.

Please come back and give some more details!

 

Edit: If a mains charger - get one that's a 3-stage type - it'll be even better for your batteries.

I've got a Mastervolt 12/80 mass battery charger (and a spare in case it ever packs in) so I thought I may as well run be running them BOTH and getting a bigger charge. Think I'll have to run cables from each charger to the batteries rather than linking them together and then running a single pair.

[OldGoat]

I've got a Mastervolt 12/80 mass battery charger (and a spare in case it ever packs in) so I thought I may as well run be running them BOTH and getting a bigger charge. Think I'll have to run cables from each charger to the batteries rather than linking them together and then running a single pair.

One is Posh, two, decidedly obscene.....

 

A quick look at the manual says one is suitable for batteries between 160 and 800Ah.

 

Are you running it from a shore supply? in which case what's the point - especially in view of my previous notes

 

If running from a generator then -

It needs to be quite a big one as each unit draws 1400 watts, so a genny should be at least 3.5Kw (for various reasons

AND

you'd need to separate them with a diode block

AND

they'd need to have a separate sense lead to allow for the diode voltage loss - although I'm certain to be corrected on that point.

 

In short NO.

[DHutch]

One is Posh, two, decidedly obscene.....

The spare charger might not be of the same spec?

 

What size/brand is the generator?

 

Hoe much power to you use/need on a daily basis?

 

 

Daniel

[nicknorman]

One is Posh, two, decidedly obscene.....

 

A quick look at the manual says one is suitable for batteries between 160 and 800Ah.

 

Are you running it from a shore supply? in which case what's the point - especially in view of my previous notes

 

If running from a generator then -

It needs to be quite a big one as each unit draws 1400 watts, so a genny should be at least 3.5Kw (for various reasons

AND

you'd need to separate them with a diode block

AND

they'd need to have a separate sense lead to allow for the diode voltage loss - although I'm certain to be corrected on that point.

 

In short NO.

Why would they need to be seperated with diodes?

[OldGoat]

Short answer:-

A very nice man at Adverc said 'because' and he knows (he's done loads of charging systems and not only for narrowboats)

 

A longer answer is that I tried the same idea with a couple of 3 stage chargers in parallel and the charge stayed the same regardless whether unit 1 or 2 or both were switched on

 

I don't understand it either....

[nicknorman]

Short answer:-

A very nice man at Adverc said 'because' and he knows (he's done loads of charging systems and not only for narrowboats)

 

A longer answer is that I tried the same idea with a couple of 3 stage chargers in parallel and the charge stayed the same regardless whether unit 1 or 2 or both were switched on

 

I don't understand it either....

Well perhaps that (your middle para) was because the batteries didn't want to take any more current. There were a spate of posts on here 3 or 4 years ago about the perils of putting chargers in parallel, or mixing charger output with alternator output, but they were/are BS IMO. We have a 175A alternator, and a Travelpower that can run the mastervolt 100A charger. With them both on, outputs connected together, they both work fine. Of course we don't get 275A going into the batteries simply because the batteries won't take it, but they play nicely together and share the load happily provided the voltages are set to much the same thing. Edited January 15, 2016 by nicknorman

[Arthur Brown]

For generator use buy the largest charger that the genset will start, -minimal run time and fuel cost but some battery damage possible.

 

For mains/shoreline use buy a charger that will charge your batteries overnight (in say 8 hours)

 

remember that a flat battery will draw a lot of current from the charger -hence from the supply- when starting, rapidly the charge rate will decrease.

[jenevers]

The spare charger might not be of the same spec?

 

What size/brand is the generator?

 

Hoe much power to you use/need on a daily basis?

 

 

Daniel

Chargers are identical.

 

Mastervolt Whisper 6000 (about 5.2kva)

 

Varies but usually 4 hours 32" TV per night using batteries via inverter. If we use electric hob, dishwasher, etc we fire up the genny.

[cuthound]

Well perhaps that (your middle para) was because the batteries didn't want to take any more current. There were a spate of posts on here 3 or 4 years ago about the perils of putting chargers in parallel, or mixing charger output with alternator output, but they were/are BS IMO. We have a 175A alternator, and a Travelpower that can run the mastervolt 100A charger. With them both on, outputs connected together, they both work fine. Of course we don't get 275A going into the batteries simply because the batteries won't take it, but they play nicely together and share the load happily provided the voltages are set to much the same thing.

Completely agree. You can parallel chargers (including alternators) and they will share current in a direct relationship with their output voltage. I have seen 50 telecoms rectifiers (basically chargers) in parallel and as Nick puts it, all playing nicely.

[jenevers]

I have 250ah AGM batteries and the data sheet says 50A max charge

So that's 20% of battery capacity.

nicknorman, on 15 Jan 2016 - 7:09 PM, said:

Well perhaps that (your middle para) was because the batteries didn't want to take any more current. There were a spate of posts on here 3 or 4 years ago about the perils of putting chargers in parallel, or mixing charger output with alternator output, but they were/are BS IMO. We have a 175A alternator, and a Travelpower that can run the mastervolt 100A charger. With them both on, outputs connected together, they both work fine. Of course we don't get 275A going into the batteries simply because the batteries won't take it, but they play nicely together and share the load happily provided the voltages are set to much the same thing.

Completely agree. You can parallel chargers (including alternators) and they will share current in a direct relationship with their output voltage. I have seen 50 telecoms rectifiers (basically chargers) in parallel and as Nick puts it, all playing nicely.

Same scenario with solar and engine alternator Edited January 16, 2016 by jenevers

[Graham.m]

I think something to remember is that it all depends on how much of the battery charge has been used. A very simple rule of thumb is that if a battery is 100Ahs discharged it will initially take 100A as the state of charge rises then say at 50Ahs the battery will take something of the order of 50A.

 

So with the setup you have I would suggest wiring the two in parallel. Start off running one, if the charger indicates it is giving 100% of its capability then switch on the other to boost the charge and once the charge indication on the chargers has dropped to 50% approx switch one of them off. No point in using diesel to support a charger that is not working fully

Edited January 16, 2016 by Graham.m