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Using two battery chargers (and solar)


Richardcn

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Hi all

Our ancient Heart Interface combi has proved itself to be rather inadequate at charging the batteries, now that our solar is unable to provide enough for our needs, so I've installed a nice little Victron Bluetooth Fandango.

But what will happen with both of them running at the same time (particularly when the batteries are low) and is that a problem. I'd guess not, from other info I've read here (and a test run) but thought I'd ask anyway.

Kipor IG2000 Generator

Heart Interface

100 amps, 14.4v (I wish!) and  goes into float very early (once it reaches about 20 amps).

Victron Blue Smart

30 amps , 14.7 volts (option) and doesn't go stupidly early into float!

Batteries

330Ah Cheapo FLA more than 3  years old and really starting to show it (maybe half capacity remaining).

Solar

500W with mppt, 14.7v

Also, if I may, how might the background solar input effect charging? I'll only be charging from the genny early in the day or if it's running for other chores. 

Oh and one final question please. Is it best to connect the Victron direct to one of the genny outputs or will a socket on the ring main be fine? I'm aware that wouldn't be a good scenario without the generator running and providing the 230v though!

I gave it a test run today after the Heart had long since tripped into float and as there was a little occasional sun I dialled down the solar to 14.2v and it all seemed fine. I actually got a half decent charge done! The Bluetooth App was really useful for watching what was happening at the charger and for changing settings on the fly. Can't wait for the inverter to expire ;-) 

Thanks

Richard

 

 

 

 

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It won’t matter having multiple charge sources in parallel during the early stages of charge as the batteries will be hungry for plenty of current. As the SoC rises the current will fall off and one of the devices will go to float. This will increase the current demand from the other device so it won’t go to float any earlier than it otherwise would. So no problem at that end of the charge either. I suppose the only problem could be if they miraculously both decided to go to float at the same instant, but that seems incredibly unlikely if they are different makes/models.

If you connect the Victron to one of the sockets there is a risk you’ll forget to turn it off and have it supplied by the inverter. On the other hand if you connect it to the genny direct, it won’t be going via an RCD. Take your pick of the least worst!

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Thanks Nick, very concise, that has allayed any concerns that I had. As the Victron charges at 14.7v and the Heart at 14.4(ish)v am I right in thinking that should ensure that the Victron will always win out? By the same thinking if I (temporarily) dial down the solar to, say 14.4v, should that also prevent an early float on the Victron?

Richard

 

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9 hours ago, Richardcn said:

Thanks Nick, very concise, that has allayed any concerns that I had. As the Victron charges at 14.7v and the Heart at 14.4(ish)v am I right in thinking that should ensure that the Victron will always win out? By the same thinking if I (temporarily) dial down the solar to, say 14.4v, should that also prevent an early float on the Victron?

Richard

 

As the Victron charges at the higher voltage it will win out all by itself with no input from you :)

Solar is free, so there’s no point in doing anything to that controller; may the best man win. 

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12 hours ago, nicknorman said:

I suppose the only problem could be if they miraculously both decided to go to float at the same instant, but that seems incredibly unlikely if they are different makes/models.

Not sure I understand the above as the only problem I can see is that both chargers may have gone to float too early. I know that is not desirable, as it would lead to the batteries being under-charged and then sulphating. Is there something else?

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2 minutes ago, Col_T said:

Not sure I understand the above as the only problem I can see is that both chargers may have gone to float too early. I know that is not desirable, as it would lead to the batteries being under-charged and then sulphating. Is there something else?

Nothing else but as Nick pointed out, just about impossible. 

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1 hour ago, Col_T said:

Not sure I understand the above as the only problem I can see is that both chargers may have gone to float too early. I know that is not desirable, as it would lead to the batteries being under-charged and then sulphating. Is there something else?

Also, as I charge from a genny, it would be a real pain if it happened frequently and without me noticing.

Now that I understand better how the 3 chargers are likely to interact I still think that, whilst genny charging (and once charging has reduced to less than 30 amps) temporarily reducing the solar charge voltage would be beneficial for the above reasons. Often the solar input is up and down and (normally) being at a similar voltage it just might trip the Victron into float, then drop off again. Of course, you'd hope that the Victron would recognise this and react appropriately but, especially at the tail end, it may not. Leaving one with rather less charge than hoped for. Once the generator is finished with I would up the solar to it's normal voltage you, hopefully, complete the task.

Richard

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9 minutes ago, Richardcn said:

Also, as I charge from a genny, it would be a real pain if it happened frequently and without me noticing.

Now that I understand better how the 3 chargers are likely to interact I still think that, whilst genny charging (and once charging has reduced to less than 30 amps) temporarily reducing the solar charge voltage would be beneficial for the above reasons. Often the solar input is up and down and (normally) being at a similar voltage it just might trip the Victron into float, then drop off again. Of course, you'd hope that the Victron would recognise this and react appropriately but, especially at the tail end, it may not. Leaving one with rather less charge than hoped for. Once the generator is finished with I would up the solar to it's normal voltage you, hopefully, complete the task.

Richard

If you only ever use the Victron from the genny, you’d be best to choose a ‘custom’ charge profile and set Float voltage to be identical to Absorb. 

If you can. 

It is completely pointless to have a genny running for a charger on float. 

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