Battery Capacity for Solar

[Dr Bob]

6 hours ago, Up-Side-Down said:

Thanks Dr Bob. That's really helpful stuff which I'll take to heart. I take it when you quote an output of 30 amp that's per hour? I've not met the concept of the two voltage knees before so, yes, more reading required! Do Jeremy's lithiums come with built in BM?

No, they are bare cells. Easy to build your own BMS. It sounds like you need to do more research.

I suggest you read the following 2 threads - which are long but contain all the info and links you need.

 

 

Bare cells are the way I chose to go but you can get 'drop ins' which may contain their own BMS but you have to be very careful here that they are not cheap chinese copies of expensive chinese good ones. See the info on 'drop ins' on the Marine How to site (one of the links)

 

 

[Dr Bob]

35 minutes ago, LadyG said:

ooooh, that's my plan quashed, will my 40amp controller be OK with 2 x 275W, on domestic, and put the old 80W panel with controller to starter batt, or just rip it out, abandon starter battery charging by solar? Old solar is bodged, I'd rather get rid.

My 500W struggle to get to 30A so your 550W should work with a 40A controller.

[Richard10002]

14 hours ago, Dr Bob said:

My 500W struggle to get to 30A so your 550W should work with a 40A controller.

Ditto. I have 490w of solar and a 40A controller, and have not seen 30A in the 2 years I’ve had them.

[MtB]

2 hours ago, Richard10002 said:

Ditto. I have 490w of solar and a 40A controller, and have not seen 30A in the 2 years I’ve had them.

 

I have 560w charging my 24v bank. I once saw 15A....

 

 

[peterboat]

I am saying nothing 

[WotEver]

16 hours ago, peterboat said:

I am saying nothing 

::::speechless::::

[peterboat]

1 hour ago, WotEver said:

::::speechless::::

I have been looking at 50 amps @ 24 volts on my meter 

[Alan de Enfield]

3 minutes ago, peterboat said:

I have been looking at 50 amps @ 24 volts on my meter 

I was thinking about getting some of those 'assorted number' self adhesive labels - do they look OK ?

[MtB]

17 minutes ago, peterboat said:

I have been looking at 50 amps @ 24 volts on my meter 

 

So I should think, given you have more solar panels on your single boat than probably all the boats in an average marina added together!

 

 

 

 

Edited March 16, 2020 by Mike the Boilerman
Add a bit

[peterboat]

11 minutes ago, Mike the Boilerman said:

 

So I should think, given you have more solar panels on your single boat than probably all the boats in an average marina added together!

 

 

 

 

True on a good day with all panels on domestic I get 79 amps!

[Up-Side-Down]

On 14/03/2020 at 22:26, Dr Bob said:

No, they are bare cells. Easy to build your own BMS. It sounds like you need to do more research.

I suggest you read the following 2 threads - which are long but contain all the info and links you need.

 

 

Bare cells are the way I chose to go but you can get 'drop ins' which may contain their own BMS but you have to be very careful here that they are not cheap chinese copies of expensive chinese good ones. See the info on 'drop ins' on the Marine How to site (one of the links)

 

 

So I've devoted time to reading both these threads and am now somewhat the wiser. I'm not going to pretend that I currently understand everything but thank you Dr Bob for once again pointing me in the right direction. I will continue with my homework all of which I find fascinating. As always the fund of knowledge and experience on this forum is second to none.

[Dr Bob]

3 hours ago, Up-Side-Down said:

So I've devoted time to reading both these threads and am now somewhat the wiser. I'm not going to pretend that I currently understand everything but thank you Dr Bob for once again pointing me in the right direction. I will continue with my homework all of which I find fascinating. As always the fund of knowledge and experience on this forum is second to none.

Fire in any questions you have and the experts here can try and answer.

[Richard10002]

7 hours ago, Up-Side-Down said:

So I've devoted time to reading both these threads and am now somewhat the wiser. I'm not going to pretend that I currently understand everything but thank you Dr Bob for once again pointing me in the right direction. I will continue with my homework all of which I find fascinating. As always the fund of knowledge and experience on this forum is second to none.

I found this guys videos got me up to speed very quickly, (along with the invaluable advice I got here ?

 

https://www.youtube.com/user/errolprowse

[Dr Bob]

17 minutes ago, Richard10002 said:

I found this guys videos got me up to speed very quickly, (along with the invaluable advice I got here ?

 

https://www.youtube.com/user/errolprowse

I also find his videos very very useful ....but, watch out and see them in the context of canal boats. A lot of the time he is looking at linking his lithiums in a solar instalation and working with just 100Ahr batteries. That makes it easy to set up various BMS units rated at less than 100A. On a canal boat you may have a 480Ahr bank which can require a capability of delivering 200A which could swamp the type of BMS (particularly the auto isolate relay) he uses. I dont think I have seen anything in his videos capable of auto switching 200A for a bare cell type set up. The other way to do it is 'drop in' type 12V batteries - and he has tested some of these - but I have not seen him link 4 of these together to give 400Ahr.

On the positive side, it shows when you know what you are doing, it is straightforward to use Li's on a boat.

[peterboat]

10 minutes ago, Dr Bob said:

I also find his videos very very useful ....but, watch out and see them in the context of canal boats. A lot of the time he is looking at linking his lithiums in a solar instalation and working with just 100Ahr batteries. That makes it easy to set up various BMS units rated at less than 100A. On a canal boat you may have a 480Ahr bank which can require a capability of delivering 200A which could swamp the type of BMS (particularly the auto isolate relay) he uses. I dont think I have seen anything in his videos capable of auto switching 200A for a bare cell type set up. The other way to do it is 'drop in' type 12V batteries - and he has tested some of these - but I have not seen him link 4 of these together to give 400Ahr.

On the positive side, it shows when you know what you are doing, it is straightforward to use Li's on a boat.

He likes valence batteries though Bob but they were small ones

[Dr Bob]

33 minutes ago, peterboat said:

He likes valence batteries though Bob but they were small ones

yes, he gives them the thumbs up .....and you can daisy chain them together.

[peterboat]

5 minutes ago, Dr Bob said:

yes, he gives them the thumbs up .....and you can daisy chain them together.

I had my electric truck checked by Wayne the mega truck expert he was impressed with the batteries and the fact that they were all sitting at the same voltage perfik balanced 

[Richard10002]

1 hour ago, Dr Bob said:

I also find his videos very very useful ....but, watch out and see them in the context of canal boats. A lot of the time he is looking at linking his lithiums in a solar instalation and working with just 100Ahr batteries. That makes it easy to set up various BMS units rated at less than 100A. On a canal boat you may have a 480Ahr bank which can require a capability of delivering 200A which could swamp the type of BMS (particularly the auto isolate relay) he uses. I dont think I have seen anything in his videos capable of auto switching 200A for a bare cell type set up.

In this video he uses a relay to allow the use of a low rated BMS, (Daley?), to protect the bank. His example is a 24V bank, but he does talk about being able to buy 400Ah cells. I think he runs 200A from the battery, but has a 100A, (possibly less), BMS.

 

 

I don't know if he solves the issue you talk about, but I did recall the video as protecting a high current draw with a low current BMS.

 

Having said that..... I drew lots of ideas and principles from him, (and from you, and MP, and PB  ), and applied them to the system I've ended up with.

[peterboat]

1 minute ago, Richard10002 said:

In this video he uses a relay to allow the use of a low rated BMS, (Daley?), to protect the bank. His example is a 24V bank, but he does talk about being able to buy 400Ah cells. I think he runs 200A from the battery, but has a 100A, (possibly less), BMS.

 

 

I don't know if he solves the issue you talk about, but I did recall the video as protecting a high current draw with a low current BMS.

 

Having said that..... I drew lots of ideas and principles from him, (and from you, and MP, and PB  ), and applied them to the system I've ended up with.

As long as it works for you Richard that's all that matters 

[Up-Side-Down]

Still busy on the homework .......... but of course being fascinating and with an end use, it's not work at all!

 

Very low on this month's quota of giggly bytes at the moment so the videos will have to wait five days. What I've dipped into seem really useful.

 

Question: Any obvious disadvantages in using a 24v system from the off? Looking at off-the-shelf 24v lithiums they appear cheaper per amp hour stored than a 12v. If I make use of the tug vehicle's charging capacity (remember we're talking about a towed replica showman's living van here) then with the relatively extended wiring that would be required there is clearly one great advantage (as in the 24v system used for attics and the like). On this basis I now regret choosing a 12v system for my 60ft nb when I fitted it out 21 years ago.

[MtB]

7 minutes ago, Up-Side-Down said:

Question: Any obvious disadvantages in using a 24v system from the off?

 

Yes, the shortage of 'off the shelf' 24v products in chandlers etc, e.g. fridges. 

 

The advantage is all your wires only need be only half the size.

 

Lithium cells are 3.2v nominally, so a 24v bank I would expect to cost twice that of a 12v bank!

 

 

[Up-Side-Down]

1 hour ago, Mike the Boilerman said:

 

Yes, the shortage of 'off the shelf' 24v products in chandlers etc, e.g. fridges. 

 

The advantage is all your wires only need be only half the size.

 

Lithium cells are 3.2v nominally, so a 24v bank I would expect to cost twice that of a 12v bank!

 

 

Is this a viable solution to the shortage of 'off the shelf' 24v products? https://www.roadpro.co.uk/product/08l-24v-12v-converters/alfatronix-24-30a-24v-12v-converter-c7505/C7505

 

I'm attracted to the advantage!

 

4 x 12v 100ah Victron lithiums cost £3671.52 while 2 x 24v 100ah Victron lithiums costs £3595.38. Less BMS I guess?

[MtB]

1 minute ago, Up-Side-Down said:

4 x 12v 100ah Victron lithiums cost £3671.52 while 2 x 24v 100ah Victron lithiums costs £3595.38. Less BMS I guess?

 

Ah but you originally said AH for AH, 24v is cheaper than 12v, which from your figures it plainly isn't.

 

Your first example gets you 400AH for £3671.52, but your second example only buys you 200AH for much the same money!!

 

 

AH is only half the story, as this illustrates..

 

 

[Chewbacka]

52 minutes ago, Mike the Boilerman said:

 

Ah but you originally said AH for AH, 24v is cheaper than 12v, which from your figures it plainly isn't.

 

Your first example gets you 400AH for £3671.52, but your second example only buys you 200AH for much the same money!!

 

 

AH is only half the story, as this illustrates..

 

 

Which is not surprising as the Watt hours is the same.

[MtB]

1 minute ago, Chewbacka said:

Which is not surprising as the Watt hours is the same.

 

Quite. That was my point.

 

Worrying about the price of the AH you are buying is not really relevant when considering what system voltage to use.