24v charging problems

[Boater Sam]

Please will someone explain what a "battery balancer" is.

After  a lifetime in electronics and boats I have never heard of such a device unless it is the same thing that Col had on his boat and removed in favour of a buck voltage reducer. And in this case with no 12v takeoff what does it do?

With one on top of the other they will never balance anyway! The excess electrons in the top battery will drop into the bottom one.?️???

[Dr Bob]

6 hours ago, Boater Sam said:

Please will someone explain what a "battery balancer" is.

After  a lifetime in electronics and boats I have never heard of such a device unless it is the same thing that Col had on his boat and removed in favour of a buck voltage reducer. And in this case with no 12v takeoff what does it do?

With one on top of the other they will never balance anyway! The excess electrons in the top battery will drop into the bottom one.?️???

The top one is obviously balanced on the bottom one.

Forgive me for my numptyness but is stacking one battery on top of the other a bad idea? Maybe they are sealed cells so you dont need access to top them up - which you wont have - but how can you periodically check the connections without removing them? You do need to check the terminals from time to time. Also wouldnt stacking them give rise to possible temperature differences? Not sure where on the boat they are located but if in the engine bay of a cruiser stern, the bottom battery could be on the swim at the canal water temp and the top one at 30°C on a nice summers day with the engine running. I guess a location temp of difference of 10°C would have quite an effect on rate of change of SoC/capacity/charging rate?

[Chewbacka]

7 hours ago, Boater Sam said:

Please will someone explain what a "battery balancer" is.

After  a lifetime in electronics and boats I have never heard of such a device unless it is the same thing that Col had on his boat and removed in favour of a buck voltage reducer. And in this case with no 12v takeoff what does it do?

With one on top of the other they will never balance anyway! The excess electrons in the top battery will drop into the bottom one.?️???

I had never heard of a battery balancer either, so I googled.  Victron make and sell one, rather than me trying to explain it, i’ll Let victron explain to those that are interested........

https://www.victronenergy.com/battery-monitors/battery-balancer

[Boater Sam]

45 minutes ago, Chewbacka said:

I had never heard of a battery balancer either, so I googled.  Victron make and sell one, rather than me trying to explain it, i’ll Let victron explain to those that are interested........

https://www.victronenergy.com/battery-monitors/battery-balancer

Thanks for that, something I can do without. No 24v.  I know of lots of boats with 24v services that don't have these fitted, they seem to be working well without.

Where does the 1Amp drawn go too I wonder? Its not made clear.

Hate to think how much they are.

Interesting that the unit refers to the upper and lower batteries, perhaps having them stacked on top of one another is the recommended installation!

[Eeyore]

3 hours ago, Dr Bob said:

The top one is obviously balanced on the bottom one.

Forgive me for my numptyness but is stacking one battery on top of the other a bad idea? Maybe they are sealed cells so you dont need access to top them up - which you wont have - but how can you periodically check the connections without removing them? You do need to check the terminals from time to time. Also wouldnt stacking them give rise to possible temperature differences? Not sure where on the boat they are located but if in the engine bay of a cruiser stern, the bottom battery could be on the swim at the canal water temp and the top one at 30°C on a nice summers day with the engine running. I guess a location temp of difference of 10°C would have quite an effect on rate of change of SoC/capacity/charging rate?

Wow, just been to something called Ikea. They have these things called “shelves”, really exciting groud breaking idea; I wonder if it could be adapted for onboard use? or too radical?

Edited February 19, 2019 by Eeyore

[Chewbacka]

4 hours ago, Boater Sam said:

Thanks for that, something I can do without. No 24v.  I know of lots of boats with 24v services that don't have these fitted, they seem to be working well without.

Where does the 1Amp drawn go too I wonder? Its not made clear.

Hate to think how much they are.

Interesting that the unit refers to the upper and lower batteries, perhaps having them stacked on top of one another is the recommended installation!

It is lost as heat, the magic box simply diverts some of the charging current away from the high voltage battery so as to reduce the charging voltage across the high battery to give the low volt battery a chance to catch up.

 

Added - A bit more google tells me you won’t get much change from £65.

Edited February 19, 2019 by Chewbacka

[Dr Bob]

5 hours ago, Eeyore said:

Wow, just been to something called Ikea. They have these things called “shelves”, really exciting groud breaking idea; I wonder if it could be adapted for onboard use? or too radical?

Yea, too radical

[cuthound]

5 hours ago, Eeyore said:

Wow, just been to something called Ikea. They have these things called “shelves”, really exciting groud breaking idea; I wonder if it could be adapted for onboard use? or too radical?

 

You can find one on the Shroppie as well as Ikea ?

[Eeyore]

MattyB, something like half a volt difference between the individual charge voltage of the two 12 volt batteries in your 24 volt setup is far too much for new batteries. There is clearly something out of specification with one or both, be that higher or lower internal resistance than the standard specification or something else; can someone with more specialist battery knowledge advise on how to approach the supplier with this issue?

The use of a balancer is simply letting the battery supplier off the hook, and is generally viewed as somewhere between snake oil and a product looking for a market.

[WotEver]

2 hours ago, Eeyore said:

MattyB, something like half a volt difference between the individual charge voltage of the two 12 volt batteries in your 24 volt setup is far too much for new batteries. There is clearly something out of specification with one or both, be that higher or lower internal resistance than the standard specification or something else; can someone with more specialist battery knowledge advise on how to approach the supplier with this issue?

The use of a balancer is simply letting the battery supplier off the hook, and is generally viewed as somewhere between snake oil and a product looking for a market.

It’s simple enough  to determine if it’s the batteries. Swap them around so that the ‘bottom’ one moves to the top. See if the lower voltage one moves. If it does then it’s the battery. 

[Boater Sam]

7 hours ago, Eeyore said:

MattyB, something like half a volt difference between the individual charge voltage of the two 12 volt batteries in your 24 volt setup is far too much for new batteries. There is clearly something out of specification with one or both, be that higher or lower internal resistance than the standard specification or something else; can someone with more specialist battery knowledge advise on how to approach the supplier with this issue?

The use of a balancer is simply letting the battery supplier off the hook, and is generally viewed as somewhere between snake oil and a product looking for a market.

I am bound to agree with you, at £65 a throw for a 1 Amp electric heater with a Voltage Dependant Resistor to control it, definitely a marketing man's dream. I thought that the one that provided a 12v output as well was good and clever but it was over $400 I think.

 

How did we ever manage without all these smart devices at crazy prices?

I can't imagine that 2 even identical batteries connected in series for years will maintain exact identical operating conditions through many charge and discharge cycles.

 Did they ever? Does it matter?

[WotEver]

5 hours ago, Boater Sam said:

I can't imagine that 2 even identical batteries connected in series for years will maintain exact identical operating conditions through many charge and discharge cycles.

Why shouldn’t they? Of course, it depends on what you mean by ‘identical’. If they’re within <0.1V then I’d say they were pretty much identical.