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Victron combi versus Separates


Dr Bob

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On 12/15/2017 at 16:02, Dr Bob said:

What I really need is to be able to keep at a reasonable float voltage ie 13.8V for long enough to get the battery to 100%

Float 'charge' is not really intended as a charge stage as such, it's just to preserve a fully charged battery, even so I'd not expect it to do that perfectly, hence the Victron solution of goosing the batt occasionally. :)

'The Battery FAQ' includes a paragraph on how to fully charge a battery along with lots of other useful info.

Edited by smileypete
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On 12/14/2017 at 22:45, Dr Bob said:

If I do then buy a new battery charger and just use the combo as an inverter, what is the best make of battery charger to get? I think 40-60A is fine (660Ahrs when new) as when we get back to the marina we usually have had a bit of engine running to get in and I don't normally go below 80%.

For topping up on a shoreline the Electroquest/Numax ones (made by Fairstone) seem to be a reasonable budget option, probably 30A, 20A, or even 10A would do for that purpose.

ISTR they're reasonably 'fit and forget' though there's loads of options that can be set through a kind of menu, probably there's one for absorption time.

Edited by smileypete
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On 14/12/2017 at 22:45, Dr Bob said:

If I do then buy a new battery charger and just use the combo as an inverter, what is the best make of battery charger to get? I think 40-60A is fine (660Ahrs when new) as when we get back to the marina we usually have had a bit of engine running to get in and I don't normally go below 80%.

A while since you asked thid, but someone else brought it to the surface.  If 30a would do you, and I share your reasoning, take a look at the latest Victron IP22 Blue Power or Blue Smart chargers. I quite like the look of matching gear, but there's better reasons than that - they're relatively inexpensive, compact, quite smart and highly configurable and also have a Lithium Ion setting so future ready.

I've just fitted the 30a Blue Smart to my 400+ domestic bank. If ever 30a is insufficient my alternator does 175a. 

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Speaking of Combis, how to people have them wired up? Fitted on the battery side of the master switch it's not strictly BSS isolated but correctly installed on the switched side, the domestic 12v system is fed by the charger when on  a shoreline and switched to 'charger only' - and of course the charger isn't charging the batteries. 

So doesn't it need a third isolator in the set-up to make everything BSS compliant? And do people bother - most boats I've seen only have two, domestic and engine. 

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Just now, starman said:

Speaking of Combis, how to people have them wired up? Fitted on the battery side of the master switch it's not strictly BSS isolated but correctly installed on the switched side, the domestic 12v system is fed by the charger when on  a shoreline and switched to 'charger only' - and of course the charger isn't charging the batteries. 

So doesn't it need a third isolator in the set-up to make everything BSS compliant? And do people bother - most boats I've seen only have two, domestic and engine. 

Battery chargers are permitted to bypass the master switch. The combi is a charger and hence may be directly connected. Obviously the cables must be fused. 

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14 hours ago, Sea Dog said:

A while since you asked thid, but someone else brought it to the surface.  If 30a would do you, and I share your reasoning, take a look at the latest Victron IP22 Blue Power or Blue Smart chargers. I quite like the look of matching gear, but there's better reasons than that - they're relatively inexpensive, compact, quite smart and highly configurable and also have a Lithium Ion setting so future ready.

I've just fitted the 30a Blue Smart to my 400+ domestic bank. If ever 30a is insufficient my alternator does 175a. 

Thanks for that Sea Dog. That does look interesting and a good price compared to the Sterling. I looked at the specs and it seems the max Absorption voltage is 14.6V and I couldnt see anything about temperature compensation so can it push out 14.8V when the batteries are cold (5°C)?

Looking at this victron one, and the Sterling one, - and all the other really useful stuff in this thread, it has lead me to a question that I need to get an answer to before making any more progress. "How are you all monitoring tail current to ensure you are 100% SOC"?

With my Victron combi, I never get a stable tail current as the unit switches out of Absorption while the current is still decreasing ie it goes to float (so the voltage goes sub 14.0V) with the Amps at 10-12A (660Ahr bank). As in a previous post, I think the combi is likely set to Predictive charging rather than Fixed charging - but I will check tomorrow when I get the front off. If I set it to Fixed, then it will stay in Absorption for the time I set it as - so say 1hr. This will enable me to watch the tail current and if it is still dropping after 1hr, I can switch the combi off and on again to give it another hour. The snag here is the TV/Pie/BT TV box/router goes off plus if I do need 3 to 4 hours charge as the batteries are low then I will have to be on the boat to keep reseting. What I think I need is a charger that I can switch easily from a method of charging a battery at say 60% of charge - where it needs to be on absorption for a reasonable time and it can go to float when it sees fit, to one where I can keep it in absorption for enough time to watch the tail current. The Combi box I have doesnt allow that without taking the cover off and faffing with dip switches. I guess I could put it into Fixed charging and give it a time of 3hrs but will that then wreck the batteries by overcharging when I plug in with the batteries full?

I am drawn towards the Sterling charger as I can change programme via easily accessible dip switches but can I specify either a 'time' based or 'adaptive' based switching or does the Sterling always make up its mind when to go to float based on its own view of tail current? How have you all got your chargers set up to see the tail current?

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2 hours ago, WotEver said:

Battery chargers are permitted to bypass the master switch. The combi is a charger and hence may be directly connected. Obviously the cables must be fused. 

But it's also an inverter that can't be directly connected :-)

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29 minutes ago, Robbo said:

I wonder if your solar is confusing it?  I have the same model as you with Trojan T105’s and monitor via a Simarine.  I have no solar yet tho.

Is that the same model - Victron Combi? If so does yours stay in Absorption long enough to watch tail current stabilise? If so, what is charging characteristic set to?

I wonder if solar is affecting it - but it is the same now on gloomy days as it was in the summer.

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9 minutes ago, Dr Bob said:

Is that the same model - Victron Combi? If so does yours stay in Absorption long enough to watch tail current stabilise? If so, what is charging characteristic set to?

I wonder if solar is affecting it - but it is the same now on gloomy days as it was in the summer.

I will have to double check the settings (I have exactly the same model 12/2000/120)  it looks to stabilise before going into float but it’s something I rarely check.   I was thinking even on gloomy days the voltage may be high even tho you get bugger all amps.

Edited by Robbo
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2 hours ago, starman said:

Speaking of Combis, how to people have them wired up? Fitted on the battery side of the master switch it's not strictly BSS isolated but correctly installed on the switched side, the domestic 12v system is fed by the charger when on  a shoreline and switched to 'charger only' - and of course the charger isn't charging the batteries. 

So doesn't it need a third isolator in the set-up to make everything BSS compliant? And do people bother - most boats I've seen only have two, domestic and engine. 

I wouldn't like the idea of leaving batteries unattended on a high power charge source, some combis can be 'dialled down' to a lower charge current though.

51 minutes ago, Dr Bob said:

I guess I could put it into Fixed charging and give it a time of 3hrs but will that then wreck the batteries by overcharging when I plug in with the batteries full?

Don't think that will do any great harm if the charge voltage is correct.

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9 minutes ago, starman said:

But it's also an inverter that can't be directly connected :-)

If you wish to avoid a BSS discussion - and as it is a charger there probably wont be one - then it would be feasible and I think best practice to put an isolator switch just for the combi connection to the battery.   That way it is easy to isolate the combi from the battery should you need to work on it, and in normal service you never need to switch it off.

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8 minutes ago, smileypete said:

Would a power bank with pass though help here?

I dont think so as they are all plugged into the 240V supply - although the router, hard drive and Pie are all 12v (can you get a power bank for 240v?). This off/on is just a hassle and I could live with it, so my focus is mainly on a charger where I can see the tail current stabilising.

 

22 minutes ago, Robbo said:

I will have to double check the settings (I have exactly the same model 12/2000/120)  it looks to stabilise before going into float but it’s something I rarely check.   I was thinking even on gloomy days the voltage may be high even tho you get bugger all amps.

Interesting. It is not easy to check the settings without taking the cover off - so can you remember if it is more 'time' based when it goes to float or is it more 'SoC' dependent?

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6 minutes ago, Dr Bob said:

I dont think so as they are all plugged into the 240V supply - although the router, hard drive and Pie are all 12v (can you get a power bank for 240v?). This off/on is just a hassle and I could live with it, so my focus is mainly on a charger where I can see the tail current stabilising.

 

Interesting. It is not easy to check the settings without taking the cover off - so can you remember if it is more 'time' based when it goes to float or is it more 'SoC' dependent?

It’s nearly all set at the default bar voltage settings and charge amps (I knocked it too 100% as off-grid most times),  so I’m guessing it’s adaptive charge, etc.

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22 minutes ago, starman said:

That saves me a bit of faffing about - I thought my set up was wrong. 

I don’t know why so many boaters assume things about the BSS instead of simply reading the regs for themselves. THEN if something is unclear by all means ask for clarification. 

https://www.boatsafetyscheme.org/media/268789/ecp-private-boats-ed3_rev2_apr2015_public_final.pdf

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1 hour ago, Dr Bob said:

I dont think so as they are all plugged into the 240V supply - although the router, hard drive and Pie are all 12v (can you get a power bank for 240v?). This off/on is just a hassle and I could live with it, so my focus is mainly on a charger where I can see the tail current stabilising.

Another way would be run 12V things off the batts, for stuff that's interconnected an isolated converter might be the safest bet, they sometimes turn up cheap(er!) on Ebay:

https://www.ebay.co.uk/itm/TRACOPOWER-Through-Hole-Isolated-DC-DC-Converter-Vin-18-to36-V-dc-Vout-12V-dc/263360466836

For something like a cheap LCD tele, or stuff thats not interconnected by wires, a decent non isolated converter ('stabiliser') might do:

https://www.amazon.co.uk/volt-stabiliser-regulator-adaptor-LED/dp/B009S9OVMM

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